publicationDate stringlengths 10 10 | title stringlengths 17 233 | abstract stringlengths 20 3.22k | id stringlengths 9 12 |
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2019-05-28 | The nature of the gravitational vacuum | The vacuum must contain virtual fluctuations of black hole microstates for
each mass $M$. We observe that the expected suppression for $M\gg m_p$ is
counteracted by the large number $Exp[S_{bek}]$ of such states. From string
theory we learn that these microstates are extended objects that are resistant
to compression. We argue that recognizing this `virtual extended
compression-resistant' component of the gravitational vacuum is crucial for
understanding gravitational physics. Remarkably, such virtual excitations have
no significant effect for observable systems like stars, but they resolve two
important problems: (a) gravitational collapse is halted outside the horizon
radius, removing the information paradox; (b) spacetime acquires a `stiffness'
against the curving effects of vacuum energy; this ameliorates the cosmological
constant problem posed by the existence of a planck scale $\Lambda$. | 1905.12004v1 |
2019-07-10 | Finding Robust Periodic Timetables by Integrating Delay Management | This paper defines and solves a mathematical model for finding robust
periodic timetables by proposing an extension of the Periodic Event Scheduling
Problem (PESP). In order to model delayed and not nominal travel times already
in the timetabling step, we integrate delay management into the periodic
timetabling problem. After revisiting both (PESP) and delay management
individually, we introduce a periodic delay management model capable of
evaluating periodic timetables with respect to delay resistance. Having
introduced periodic delay management, we define the Robust Periodic Timetabling
problem (RPT). Due to the high complexity of (RPT) we propose two different
simplifications of the problem and introduce solution algorithms for both of
them. These solution algorithms are tested against timetables found by standard
procedures for periodic timetabling with respect to their delay-resistance. The
computational results show that our algorithms yield timetables which can cope
better with occurring delays, even on large-scale datasets and with low
computational effort. | 1907.04554v1 |
2020-02-07 | Spin-dependent transport through a Weyl semimetal surface | We experimentally compare two types of interface structures with magnetic and
non-magnetic Weyl semimetals. They are the junctions between a gold normal
layer and magnetic Weyl semimetal Ti$_2$MnAl, and a ferromagnetic nickel layer
and non-magnetic Weyl semimetal WTe$_2$, respectively. Due to the ferromagnetic
side of the junction, we investigate spin-polarized transport through the Weyl
semimetal surface. For both structures, we demonstrate similar current-voltage
characteristics, with hysteresis at low currents and sharp peaks in
differential resistance at high ones. Despite this behavior resembles the known
current-induced magnetization dynamics in ferromagnetic structures, evolution
of the resistance peaks with magnetic field is unusual. We connect the observed
effects with current-induced spin dynamics in Weyl topological surface states. | 2002.02673v2 |
2020-03-02 | A resistive ACHINOS multi-anode structure with DLC coating for spherical proportional counters | The spherical proportional counter is a gaseous detector used in a variety of
applications, including direct dark matter and neutrino-less double beta decay
searches. The ACHINOS multianode structure is a read-out technology that
overcomes the limitations of single-anode read-out structures for large-size
detectors and operation under high pressure. A resistive ACHINOS is presented,
where the 3D printed central component is coated in a Diamond-Like Carbon (DLC)
layer. The production and testing of the structure, in terms of stability and
resolution, is described. Further applications in fundamental physics and
industry are also discussed. | 2003.01068v2 |
2020-03-09 | BitTensor: A Peer-to-Peer Intelligence Market | As with other commodities, markets could help us efficiently produce machine
intelligence. We propose a market where intelligence is priced by other
intelligence systems peer-to-peer across the internet. Peers rank each other by
training neural networks which learn the value of their neighbors. Scores
accumulate on a digital ledger where high ranking peers are monetarily rewarded
with additional weight in the network. However, this form of peer-ranking is
not resistant to collusion, which could disrupt the accuracy of the mechanism.
The solution is a connectivity-based regularization which exponentially rewards
trusted peers, making the system resistant to collusion of up to 50 percent of
the network weight. The result is a collectively run intelligence market which
continual produces newly trained models and pays contributors who create
information theoretic value. | 2003.03917v3 |
2020-04-20 | Anomalous Magnetoresistance in Centrosymmetric Skyrmion-Lattice Magnet Gd2PdSi3 | We performed a systematic study of the temperature- and field-dependence of
magnetization and resistivity of Gd2PdSi3, which is a centrosymmetric skyrmion
crystal. While the magnetization behavior is consistent with the reported phase
diagram based on susceptibility, we show that a phase diagram can also be
constructed based on the anomalous magnetoresistance with one-to-one
correspondence among all the features. In addition, the crossover boundary into
the field-induced ferromagnetic state is also identified. Our results suggest
that the ferromagnetic spin fluctuations above the N\'eel temperature play a
key role in the high sensitivity of the resistivity anomalies to magnetic
field, pointing to the rich interplay of different magnetic correlations at
zero and finite wave vectors underlying the skyrmion lattice in this frustrated
itinerant magnet. | 2004.09664v1 |
2020-04-29 | Numerical study of space charge electric field inside Resistive Plate Chamber | Resistive plate chamber (RPC) is one of the state-of-the-art particle
detection technology for the High Energy Physics (HEP) experiments. The basic
operating mechanism of an RPC involves ionization of gas due to the passage of
charged particles followed by electron transport , avalanche, and subsequent
electromagnetic induction on readout strips due to the movement of the
electrons and ions. Especially during streamer mode of operation, the electric
field applied to the RPC can get significantly modified due to the presence of
large number of electrons and ions. In this study, we have worked on dominant
issues related to the estimation of electric field due to the space charge
arising out of the presence of electrons, ions within an RPC. For this purpose
we have considered two approaches: representation of the space charge cloud as
(a) a collection of ring charges, and (b) as a collection of line charges. The
results from these different methods have been compared with results available
in the literature. | 2004.13899v2 |
2020-09-22 | Adversarial Attack Based Countermeasures against Deep Learning Side-Channel Attacks | Numerous previous works have studied deep learning algorithms applied in the
context of side-channel attacks, which demonstrated the ability to perform
successful key recoveries. These studies show that modern cryptographic devices
are increasingly threatened by side-channel attacks with the help of deep
learning. However, the existing countermeasures are designed to resist
classical side-channel attacks, and cannot protect cryptographic devices from
deep learning based side-channel attacks. Thus, there arises a strong need for
countermeasures against deep learning based side-channel attacks. Although deep
learning has the high potential in solving complex problems, it is vulnerable
to adversarial attacks in the form of subtle perturbations to inputs that lead
a model to predict incorrectly.
In this paper, we propose a kind of novel countermeasures based on
adversarial attacks that is specifically designed against deep learning based
side-channel attacks. We estimate several models commonly used in deep learning
based side-channel attacks to evaluate the proposed countermeasures. It shows
that our approach can effectively protect cryptographic devices from deep
learning based side-channel attacks in practice. In addition, our experiments
show that the new countermeasures can also resist classical side-channel
attacks. | 2009.10568v1 |
2007-10-19 | Disorder, Metal-Insulator crossover and Phase diagram in high-Tc cuprates | We have studied the influence of disorder induced by electron irradiation on
the normal state resistivities $\rho(T)$ of optimally and underdoped YBa2CuOx
single crystals, using pulsed magnetic fields up to 60T to completely restore
the normal state. We evidence that point defect disorder induces low T upturns
of rho(T) which saturate in some cases at low T in large applied fields as
would be expected for a Kondo-like magnetic response. Moreover the magnitude of
the upturns is related to the residual resistivity, that is to the
concentration of defects and/or their nanoscale morphology. These upturns are
found quantitatively identical to those reported in lower Tc cuprates, which
establishes the importance of disorder in these supposedly pure compounds. We
therefore propose a realistic phase diagram of the cuprates, including
disorder, in which the superconducting state might reach the antiferromagnetic
phase in the clean limit. | 0710.3737v2 |
2014-01-23 | Crawling on directional surfaces | In this paper we study crawling locomotion based on directional frictional
interactions, namely, frictional forces that are sensitive to the sign of the
sliding velocity. Surface interactions of this type are common in biology,
where they arise from the presence of inclined hairs or scales at the
crawler/substrate interface, leading to low resistance when sliding 'along the
grain', and high resistance when sliding 'against the grain'. This asymmetry
can be exploited for locomotion, in a way analogous to what is done in
cross-country skiing (classic style, diagonal stride). We focus on a model
system, namely, a continuous one-dimensional crawler and provide a detailed
study of the motion resulting from several strategies of shape change. In
particular, we provide explicit formulae for the displacements attainable with
reciprocal extensions and contractions (breathing), or through the propagation
of extension or contraction waves. We believe that our results will prove
particularly helpful for the study of biological crawling motility and for the
design of bio-mimetic crawling robots. | 1401.5929v1 |
2016-03-14 | Study of Performance of Bakelite Resistive Plate Chamber (RPC) | Resistive Plate Chamber (RPC) is a type of gaseous detector having excellent
time and position resolutions. VECC is involved in the R\&D of indigenously
developed bakelite RPCs. The largest size of bakelite RPC developed in India is
100 cm $\times$ 100 cm. We present here the test results of a bakelite sample
along with the cosmic ray test results of a bakelite RPC (30 cm $\times$ 30 cm
$\times$ 0.2cm) fabricated at VECC. The steps taken towards the development of
a large size (240 cm $\times$ 120 cm $\times$ 0.2 cm) bakelite RPC have also
been discussed. | 1603.04875v1 |
2017-04-24 | Electronic transport properties of intermediately coupled superconductors: PdTe2 and Cu0.04PdTe2 | We have investigated the electrical resistivity, Seebeck coefficient and
thermal conductivity of PdTe2 and 4% Cu intercalated PdTe2 compounds.
Electrical resistivity for the compounds shows Bloch-Gruneisen type linear
temperature (T) dependence for 100 K < T < 480 K, and Fermi liquid behavior (~
T^2) below 50 K. Seebeck coefficient data exhibit strong competition between
Normal (N) and Umklapp (U) scattering processes at low T. Though our results
indicate the transfer of charge carriers to PdTe2 upon Cu intercalation, it is
difficult to discern any change in the Fermi surface of the compound by
Nordheim-Gorter plots. The estimated Fermi energies of the compounds are quite
comparable to good metals Cu, Ag and Au. The low T, thermal conductivity (k) of
the compounds is strongly dominated by the electronic contribution, and
exhibits a rare linear T dependence below 10 K. However, high T, k(T) shows
usual 1/T dependence, dominated by U scattering process. The electron phonon
coupling parameters, estimated from the low T, specific heat data and first
principle electronic structure calculations suggest that PdTe2 and Cu0.04PdTe2
are intermediately coupled superconductors. | 1704.07194v2 |
2017-05-01 | Magnetic Skyrmions for Cache Memory | Magnetic skyrmions (MS) are particle-like spin structures with whirling
configuration, which are promising candidates for spin-based memory. MS
contains alluring features including remarkably high stability, ultra low
driving current density, and compact size. Due to their higher stability and
lower drive current requirement for movement, skyrmions have great potential in
energy efficient spintronic device applications. We propose a skyrmion-based
cache memory where data can be stored in a long nanotrack as multiple bits.
Write operation (formation of skyrmion) can be achieved by injecting spin
polarized current in a magnetic nanotrack and subsequently shifting the MS in
either direction along the nanotrack using charge current through a spin-Hall
metal (SHM), underneath the magnetic layer. The presence of skyrmion can alter
the resistance of a magnetic tunneling junction (MTJ) at the read port.
Considering the read and write latency along the long nanotrack cache memory, a
strategy of multiple read and write operations is discussed. Besides, the size
of a skyrmion affects the packing density, current induced motion velocity, and
readability (change of resistance while sensing the existence of a skyrmion).
Design optimization to mitigate the above effects is also investigated. | 1705.01095v1 |
2017-08-17 | van der Waals Bonded Co/h-BN Contacts to Ultrathin Black Phosphorus Devices | Due to the chemical inertness of 2D hexagonal-Boron Nitride (h-BN), few
atomic-layer h-BN is often used to encapsulate air-sensitive 2D crystals such
as Black Phosphorus (BP). However, the effects of h-BN on Schottky barrier
height, doping and contact resistance are not well known. Here, we investigate
these effects by fabricating h-BN encapsulated BP transistors with cobalt (Co)
contacts. In sharp contrast to directly Co contacted p-type BP devices, we
observe strong n-type conduction upon insertion of the h-BN at the Co/BP
interface. First principles calculations show that this difference arises from
the much larger interface dipole at the Co/h-BN interface compared to the Co/BP
interface, which reduces the work function of the Co/h-BN contact. The Co/h-BN
contacts exhibit low contact resistances (~ 4.5 k-ohm), and are Schottky
barrier free. This allows us to probe high electron mobilities (4,200 cm2/Vs)
and observe insulator-metal transitions even under two-terminal measurement
geometry. | 1708.05162v1 |
2017-08-25 | Pressure-induced magnetic collapse and metallization of $\mathrm{TlF}{\mathrm{e}}_{1.6}\mathrm{S}{\mathrm{e}}_{2}$ | The crystal structure, magnetic ordering, and electrical resistivity of
TlFe1.6Se2 were studied at high pressures. Below ~7 GPa, TlFe1.6Se2 is an
antiferromagnetically ordered semiconductor with a ThCr2Si2-type structure. The
insulator-to-metal transformation observed at a pressure of ~ 7 GPa is
accompanied by a loss of magnetic ordering and an isostructural phase
transition. In the pressure range ~ 7.5 - 11 GPa a remarkable downturn in
resistivity, which resembles a superconducting transition, is observed below 15
K. We discuss this feature as the possible onset of superconductivity
originating from a phase separation in a small fraction of the sample in the
vicinity of the magnetic transition. | 1708.07702v1 |
2017-08-29 | Physical and geometric constraints explain the labyrinth-like shape of the nasal cavity | The nasal cavity is a vital component of the respiratory system that heats
and humidifies inhaled air in all vertebrates. Despite this common function,
the shapes of nasal cavities vary widely across animals. To understand this
variability, we here connect nasal geometry to its function by theoretically
studying the airflow and the associated scalar exchange that describes heating
and humidification. We find that optimal geometries, which have minimal
resistance for a given exchange efficiency, have a constant gap width between
their side walls, but their overall shape is restricted only by the geometry of
the head. Our theory explains the geometric variations of natural nasal
cavities quantitatively and we hypothesize that the trade-off between high
exchange efficiency and low resistance to airflow is the main driving force
shaping the nasal cavity. Our model further explains why humans, whose nasal
cavities evolved to be smaller than expected for their size, become obligate
oral breathers in aerobically challenging situations. | 1708.08966v1 |
2018-08-29 | Quantum phase transition in ultrahigh mobility SiGe/Si/SiGe two-dimensional electron system | The metal-insulator transition (MIT) is an exceptional test bed for studying
strong electron correlations in two dimensions in the presence of disorder. In
the present study, it is found that in contrast to previous experiments on
lower-mobility samples, in ultra-high mobility SiGe/Si/SiGe quantum wells the
critical electron density, $n_{\text{c}}$, of the MIT becomes smaller than the
density, $n_{\text{m}}$, where the effective mass at the Fermi level tends to
diverge. Near the topological phase transition expected at $n_{\text{m}}$, the
metallic temperature dependence of the resistance should be strengthened, which
is consistent with the experimental observation of more than an order of
magnitude resistance drop with decreasing temperature below $\sim1$ K. | 1808.10063v3 |
2019-03-14 | A Two-Dimensional Resistor Network Model for Transition-Edge Sensors with Normal Metal Features | Transition-edge sensors (TESs) can be used in high-resolution photon
detection, exploiting the steep slope of the resistance in the
superconducting-to-normal transition edge. Normal metal bars on the TES film
are commonly used to engineer its transition shape, namely the dependence of
resistance on temperature and current. This problem has been studied in one
dimension, however until now, there have been no predictive models of the
influence of two-dimensional (2-D) normal metal features on the TES transition
shape. In this work, we approach this problem by treating the TES as a 2-D
network of resistors, the values of which are based on the two-fluid model. We
present a study of the behavior of devices with different 2-D geometric
features. Our 2-D network model is capable of predicting how typical TES
geometry parameters, such as number of bars, bar spacing, and overall
dimensions, influence device behavior and thus is a powerful tool to guide the
engineering of new TES devices. | 1903.06271v1 |
2019-04-01 | Quantum and classical ratchet motions of vortices in a 2D trigonal superconductor | Dynamical behavior of vortices plays central roles in the quantum phenomena
of two-dimensional (2D) superconductors. Quantum metallic state, for example,
showing an anomalous temperature-independent resistive state down to
low-temperatures, has been a common subject in recently developed 2D
crystalline superconductors, whose microscopic origin is still under debate.
Here, we unveil a new aspect of the vortex dynamics in a noncentrosymmetric 2D
crystalline superconductor of MoS$_{2}$ through the nonreciprocal transport
measurement. The second harmonic resistance $R^{2w}$ at low temperature with
high current indicates the classical vortex flow accompanying the ratchet
motion. Furthermore, we found that $R^{2w}$ is substantially suppressed in the
quantum metallic state with low current region, allowing identification of the
quantum and classical ratchet motions of vortices by the magnitude of the
second harmonic generation. This suggests that nonreciprocal transport
measurement can be a powerful tool to probe the vortex dynamics in
noncentrosymmetric 2D superconductors. | 1904.00611v1 |
2019-04-03 | Transport and chaos in lattice Sachdev-Ye-Kitaev models | We compute the transport and chaos properties of lattices of quantum
Sachdev-Ye-Kitaev islands coupled by single fermion hopping, and with the
islands coupled to a large number of local, low energy phonons. We find two
distinct regimes of linear-in-temperature ($T$) resistivity, and describe the
crossover between them. When the electron-phonon coupling is weak, we obtain
the `incoherent metal' regime, where there is near-maximal chaos with front
propagation at a butterfly velocity $v_B$, and the associated diffusivity
$D_{\rm chaos} = v_B^2/(2 \pi T)$ closely tracks the energy diffusivity. On the
other hand, when the electron-phonon coupling is strong, and the linear
resistivity is largely due to near-elastic scattering of electrons off nearly
free phonons, we find that the chaos is far from maximal and spreads
diffusively. We also describe the crossovers to low $T$ regimes where the
electronic quasiparticles are well defined. | 1904.02174v2 |
2019-12-10 | Structural properties and magnetoresistance of La$_{1.952}$Sr$_{0.048}$CuO$_4$ thin films | The evolution of the structural and transport properties of underdoped
La$_{1.952}$Sr$_{0.048}$CuO$_4$ thin films under compressive epitaxial strain
has been studied. The films of different thicknesses $d$ (from 26 nm to 120 nm)
were deposited using an insulating target. The onset of superconductivity in
the films is observed at temperatures as high as 26 K, while small residual
resistance persists at low temperatures, indicating that superconductivity is
inhomogeneous. The resistance measured under perpendicular magnetic field
saturates below about 0.65 K, suggesting a possible existence of
nonconventional metallic state. The magnetic-field-tuned
superconductor-insulator transition is observed at magnetic field of about 32
T. | 1912.04594v2 |
2019-12-26 | Inflationary routes to Gaussian curved topography | Gaussian-curved shapes are obtained by inflating initially flat systems made
of two superimposed strong and light thermoplastic impregnated fabric sheets
heat-sealed together along a specific network of lines. The resulting inflated
structures are light and very strong because they (largely) resist deformation
by the intercession of stretch. Programmed patterns of channels vary either
discretely through boundaries, or continuously. The former give rise to
facetted structures that are in effect non-isometric origami and which cannot
unfold as in conventional folded structures, since they present localized angle
deficit or surplus. Continuous variation of channel direction in the form of
spirals is examined, giving rise to curved shells. We solve the inverse problem
consisting in finding a network of seam lines leading to a target axisymmetric
shape on inflation. They too have strength from the metric changes that have
been pneumatically driven, resistance to change being met with stretch and
hence high forces like typical shells . | 1912.13425v3 |
2021-01-04 | Holographic DC Conductivity for Backreacted NLED in Massive Gravity | In this work a holographic model with the charge current dual to a general
nonlinear electrodynamics (NLED) is discussed in the framework of massive
gravity. Massive graviton can breaks the diffeomorphism invariance in the bulk
and generates momentum dissipation in the dual boundary theory. The expression
of DC conductivities in a finite magnetic field are obtained, with the
backreaction of NLED field on the background geometry. General transport
properties in various limits are presented, and then we turn to the three of
specific NLED models: the conventional Maxwell electrodynamics, the
Maxwell-Chern-Simons electrodynamics, and the Born-Infeld electrodynamics, to
study the parameter-dependence of in-plane resistivity. Two mechanisms leading
to the Mott-insulating behaviors and negative magneto-resistivity are revealed
at zero temperature, and the role played by the massive gravity coupling
parameters are discussed. | 2101.00912v1 |
2021-01-06 | Bose-Luttinger Liquids | We study systems of bosons whose low-energy excitations are located along a
spherical submanifold of momentum space. We argue for the existence of gapless
phases which we dub "Bose-Luttinger liquids", which in some respects can be
regarded as bosonic versions of Fermi liquids, while in other respects exhibit
striking differences. These phases have bosonic analogues of Fermi surfaces,
and like Fermi liquids they possess a large number of emergent conservation
laws. Unlike Fermi liquids however these phases lack quasiparticles, possess
different RG flows, and have correlation functions controlled by a continuously
varying exponent $\eta$, which characterizes the anomalous dimension of the
bosonic field. We show that when $\eta>1$, these phases are stable with respect
to all symmetric perturbations. These theories may be of relevance to several
physical situations, including frustrated quantum magnets, rotons in superfluid
He, and superconductors with finite-momentum pairing. As a concrete
application, we show that coupling a Bose-Luttinger liquid to a conventional
Fermi liquid produces a resistivity scaling with temperature as $T^\eta$. We
argue that this may provide an explanation for the non-Fermi liquid resistivity
observed in the paramagnetic phase of MnSi. | 2101.02197v2 |
2021-01-22 | Magnetic doping effects on the superconductivity of Y1-xMxBa2Cu3O7-d (M = Fe, Co, Ni) | The discovery of superconductivity in copper oxide compounds has attracted
considerable attention over the past three decades. The high transition
temperature in these compounds, exhibiting proximity to an antiferromagnetic
order in their phase diagrams, remains one of the main areas of research. The
present study attempts to introduce Fe, Co and Ni magnetic impurities into the
superconducting Y-123 with the aim of exploring the transition temperature
behavior. The solid-state synthesis is exploited to prepare fully oxygenated
Y1-xMxBa2Cu3O7 (M = Co, Fe, Ni) samples with low levels of doping (0< x <
0.03). Systematic measurements are then employed to assess the synthesized
samples using AC magnetic susceptibility, electrical resistivity and X-ray
diffraction. The measurements revealed an increase in Tc as a result of
magnetic substitution for Y. However, the study of non-magnetic dopings on the
fully oxygenated Y1-xM'xBa2Cu3O7 (M' = Ca, Sr) samples showed a decrease in Tc.
Quantitative XRD analysis further suggested that the internal pressure could
have minor effects on the increase in Tc. The normal state resistivity vs
temperature showed a linear profile, confirming that the samples are at an
optimal doping of the carrier concentration. | 2101.09292v1 |
2011-04-01 | Effective Field Theory of Fractional Quantized Hall Nematics | We present a Landau-Ginzburg theory for a fractional quantized Hall nematic
state and the transition to it from an isotropic fractional quantum Hall state.
This justifies Lifshitz-Chern-Simons theory -- which is shown to be its dual --
on a more microscopic basis and enables us to compute a ground state wave
function in the symmetry-broken phase. In such a state of matter, the Hall
resistance remains quantized while the longitudinal DC resistivity due to
thermally-excited quasiparticles is anisotropic. We interpret recent
experiments at Landau level filling factor \nu =7/3 in terms of our theory. | 1104.0256v2 |
2011-04-26 | Degenerate versus semi-degenerate transport in a correlated 2D hole system | It has been puzzling that the resistivity of high mobility
two-dimensional(2D) carrier systems in semiconductors with low carrier density
often exhibits a large increase followed by a decrease when the temperature
($T$) is raised above a characteristic temperature comparable with the Fermi
temperature ($T_F$). We find that the metallic 2D hole system (2DHS) in GaAs
quantum well (QW) has a linear density ($p$) dependent conductivity,
$\sigma\approx e\mu^*(p-p_0)$, in both the degenerate (T<<T_F) and
semi-degenerate (T T_F) regimes. The $T$-dependence of $\sigma(p)$ suggests
that the metallic conduction (d$\sigma$/d$T<$0) at low $T$ is associated with
the increase in $\mu^*$, the effective mobility of itinerant carriers. However,
the resistivity decrease in the semi-degenerate regime ($T>T_F$) is originated
from the reduced $p_0$, the density of immobile carriers in a two-phase
picture. | 1104.4834v1 |
2012-06-13 | LSFEM implementation of MHD numerical solver | Many problems in physics are inherently of multi-scale nature. The issues of
MHD turbulence or magnetic reconnection, namely in the hot and sparse, almost
collision-less astrophysical plasmas, can stand as clear examples. The Finite
Element Method (FEM) with adaptive gridding appears to be the appropriate
numerical implementation for handling the broad range of scales contained in
such high Lundquist-number MHD problems. In spite the FEM is now routinely used
in engineering practice in solid-state and fluid dynamics, its usage for MHD
simulations has recently only begun and only few implementations exist so far.
In this paper we present our MHD solver based on the Least-Square FEM (LSFEM)
formulation. We describe the transformation of the MHD equations into form
required for finding the LSFEM functional and some practical issues in
implementation of the method. The algorithm was tested on selected problems of
ideal (non-resistive) and resistive MHD. The tests show the usability of LSFEM
for solving MHD equations. | 1206.2730v1 |
2012-06-13 | Implementation of low-loss superinductances for quantum circuits | The simultaneous suppression of charge fluctuations and offsets is crucial
for preserving quantum coherence in devices exploiting large quantum
fluctuations of the superconducting phase. This requires an environment with
both extremely low DC and high RF impedance. Such an environment is provided by
a superinductance, defined as a zero DC resistance inductance whose impedance
exceeds the resistance quantum $R_Q = h/(2e)^2 \simeq 6.5\ \mathrm{k\Omega}$ at
frequencies of interest (1 - 10 GHz). In addition, the superinductance must
have as little dissipation as possible, and possess a self-resonant frequency
well above frequencies of interest. The kinetic inductance of an array of
Josephson junctions is an ideal candidate to implement the superinductance
provided its phase slip rate is sufficiently low. We successfully implemented
such an array using large Josephson junctions ($E_J >> E_C$), and measured
internal losses less than 20 ppm, self-resonant frequencies greater than 10
GHz, and phase slip rates less than 1 mHz. | 1206.2964v1 |
2012-06-14 | Universal transport near a quantum critical Mott transition in two dimensions | We discuss the universal transport signatures near a zero-temperature
continuous Mott transition between a Fermi liquid (FL) and a quantum spin
liquid in two spatial dimensions. The correlation-driven transition occurs at
fixed filling and involves fractionalization of the electron: upon entering the
spin liquid, a Fermi surface of neutral spinons coupled to an internal gauge
field emerges. We present a controlled calculation of the value of the zero
temperature universal resistivity jump predicted to occur at the transition.
More generally, the behavior of the universal scaling function that collapses
the temperature and pressure dependent resistivity is derived, and is shown to
bear a strong imprint of the emergent gauge fluctuations. We further predict a
universal jump of the thermal conductivity across the Mott transition, which
derives from the breaking of conformal invariance by the damped gauge field,
and leads to a violation of the Wiedemann-Franz law in the quantum critical
region. A connection to organic salts is made, where such a transition might
occur. Finally, we present some transport results for the pure rotor O(N) CFT. | 1206.3309v2 |
2012-06-22 | Optically induced nuclear spin polarization in a single GaAs/AlGaAs quantum well probed by a resistance detection method in the fractional quantum Hall regime | We study the optically pumped nuclear spin polarization in a single
GaAs/AlGaAs quantum well in the quantum Hall system. We apply resistive
detection via the contact hyperfine interaction, which provides high
sensitivity and selectivity, to probe a small amount of polarized nuclear spins
in a single well. The properties of the optical nuclear spin polarization are
clearly observed. We theoretically discuss the nuclear spin dynamics
accompanied with doped electrons to analyze the experimental data. The optical
nuclear polarization spectra exhibit electron-spin-resolved lowest Landau level
interband transitions. We find that the phonon emission process, which normally
assists the optical pumping process, influences the optical nuclear spin
polarization. We also discuss that the electron-electron interaction can play
an important role in the optical nuclear spin polarization. | 1206.5227v3 |
2012-06-22 | Inter-subband resistance oscillations in crossed electric and magnetic fields | Quantum oscillations of nonlinear resistance are investigated in response to
electric current and magnetic field applied perpendicular to single GaAs
quantum wells with two populated subbands. At small magnetic fields
current-induced oscillations appear as Landau-Zener transitions between Landau
levels inside the lowest subband. Period of these oscillations is proportional
to the magnetic field. At high magnetic fields different kind of quantum
oscillations emerges with a period,which is independent of the magnetic field.
At a fixed current the oscillations are periodic in inverse magnetic field with
a period that is independent of the dc bias. The proposed model considers these
oscillations as a result of spatial variations of the energy separation between
two subbands induced by the electric current. | 1206.5233v1 |
2012-06-28 | Trigonometrical sums connected with the chiral Potts model, Verlinde dimension formula, two-dimensional resistor network, and number theory | \ \ We have recently developed methods for obtaining exact two-point
resistance of the complete graph minus $N$ edges. We use these methods to
obtain closed formulas of certain trigonometrical sums that arise in connection
with one-dimensional lattice, in proving the Scott's conjecture on permanent of
Cauchy matrix, and in the perturbative chiral Potts model. The generalized
trigonometrical sums of the chiral Potts model are shown to satisfy recursion
formulas that are transparent and direct, and differ from those of Gervois and
Mehta. By making a change of variables in these recursion formulas, the
dimension of the space of conformal blocks of $SU(2)$ and $SO(3)$ WZW models
may be computed recursively. Our methods are then extended to compute the
corner-to-corner resistance, and the Kirchhoff index of the first non-trivial
two-dimensional resistor network, $2\times N$. Finally, we obtain new closed
formulas for variant of trigonometrical sums, some of which appear in
connection with number theory. | 1206.6673v2 |
2015-06-12 | Phase-coherent transport in catalyst-free vapor phase deposited Bi$_2$Se$_3$ crystals | Free-standing Bi$_2$Se$_3$ single crystal flakes of variable thickness are
grown using a catalyst-free vapor-solid synthesis and are subsequently
transferred onto a clean Si$^{++}$/SiO$_2$ substrate where the flakes are
contacted in Hall bar geometry. Low temperature magneto-resistance measurements
are presented which show a linear magneto-resistance for high magnetic fields
and weak anti-localization (WAL) at low fields. Despite an overall strong
charge carrier tunability for thinner devices, we find that electron transport
is dominated by bulk contributions for all devices. Phase coherence lengths
$\l_\phi$ as extracted from WAL measurements increase linearly with increasing
electron density exceeding $1 \mu $m at 1.7 K. While $\l_\phi$ is in
qualitative agreement with electron electron interaction-induced dephasing, we
find that spin flip scattering processes limit $\l_\phi$ at low temperatures. | 1506.04097v1 |
2015-06-24 | C-axis electrical resistivity of PrO$_{1-a}$F$_a$BiS$_2$ single crystals | The high anisotropy in RO1-aFaBiS2 (R denotes a rare-earth element)
superconductors demonstrates their potential use as intrinsic Josephson
junctions, considering the weak coupling among BiS2-PrO(F)-BiS2
(superconducting-normal-superconducting) layers along the c-axis. We grew
PrO1-aFaBiS2 single crystals using CsCl/KCl flux. The superconducting
anisotropies of the grown single crystals were estimated to be approximately
40-50 from the effective mass model. The c-axis transport properties were
characterized using single-crystal s-shaped intrinsic Josephson junctions with
a focused ion beam. Along the c-axis, the crystals showed zero resistivity at
2.7 K and a critical current density of 1.33*10^3 A/cm2 at 2.0 K. The
current-voltage curve along the c-axis displayed hysteresis. The c-axis
transport measurements under a magnetic field parallel to the ab-plane revealed
a "lock-in" state due to the Josephson vortex flow, indicating that BiS2
superconductors are promising candidates for intrinsic Josephson junctions. | 1506.07231v1 |
2015-07-06 | Switching Synchronization in One-Dimensional Memristive Networks | We report on an astonishing switching synchronization phenomenon in
one-dimensional memristive networks, which occurs when several memristive
systems with different switching constants are switched from the high to low
resistance state. Our numerical simulations show that such a collective
behavior is especially pronounced when the applied voltage slightly exceeds the
combined threshold voltage of memristive systems. Moreover, a finite increase
in the network switching time is found compared to the average switching time
of individual systems. An analytical model is presented to explain our
observations. Using this model, we have derived asymptotic expressions for
memory resistances at short and long times, which are in excellent agreement
with our numerical calculations. | 1507.01640v1 |
2018-07-09 | Artificial Neural Networks-based Track Fitting of Cosmic Muons through Stacked Resistive Plate Chambers | The India-based Neutrino Observatory (INO) collaboration, as part of its
detector R\&D program, has developed prototype stacks of resistive plate
chambers (RPCs) to study their performance. These stacks have also been used as
testbenches for the development of related hardware and software. A crucial
parameter in the characterisation of these detectors and other physics studies
is the detection efficiency, which is estimated from track fitting of cosmic
muons passing through the stack. So far, a simple straight line fit was used
for track fitting, which was sensitive to noise hits and led to rejection of
events. In this paper, we present our first results of using artificial neural
networks (ANN) for track fitting of cosmic muons traversing a stack of RPCs. We
present in detail, the simulation framework designed for this purpose and show
that ANN offers better track reconstruction efficiency than straight line
fitting. We also discuss the influence of noise and detection efficiency of
cosmic muons on the track reconstruction efficiency. | 1807.04625v3 |
2018-12-01 | A Flux-Balanced Fluid Model for Collisional Plasma Edge Turbulence: Numerical Simulations with Different Aspect Ratios | We investigate the drift wave -- zonal flow dynamics in a shearless slab
geometry with the new flux-balanced Hasegawa-Wakatani model. As in previous
Hasegawa-Wakatani models, we observe a sharp transition from a turbulence
dominated regime to a zonal jet dominated regime as we decrease the plasma
resistivity. However, unlike previous models, zonal structures are always
present in the flux-balanced model, even for high resistivity, and strongly
reduce the level of particle and vorticity flux. The more robust zonal jets
also have a higher variability than in previous models, which is further
enhanced when the computational domain is chosen to be elongated in the radial
direction. In these cases, we observe complex multi-scale dynamics, with
multiple jets interacting with one another, and intermittent bursts. We present
a detailed statistical analysis which highlights how the changes in the aspect
ratio of the computational domain affect the third-order statistical moments,
and thus modify the turbulent dynamics. | 1812.00131v1 |
2018-12-26 | Deep learning electromagnetic inversion with convolutional neural networks | Geophysical inversion attempts to estimate the distribution of physical
properties in the Earth's interior from observations collected at or above the
surface. Inverse problems are commonly posed as least-squares optimization
problems in high-dimensional parameter spaces. Existing approaches are largely
based on deterministic gradient-based methods, which are limited by
nonlinearity and nonuniqueness of the inverse problem. Probabilistic inversion
methods, despite their great potential in uncertainty quantification, still
remain a formidable computational task. In this paper, I explore the potential
of deep learning methods for electromagnetic inversion. This approach does not
require calculation of the gradient and provides results instantaneously. Deep
neural networks based on fully convolutional architecture are trained on large
synthetic datasets obtained by full 3-D simulations. The performance of the
method is demonstrated on models of strong practical relevance representing an
onshore controlled source electromagnetic CO2 monitoring scenario. The
pre-trained networks can reliably estimate the position and lateral dimensions
of the anomalies, as well as their resistivity properties. Several fully
convolutional network architectures are compared in terms of their accuracy,
generalization, and cost of training. Examples with different survey geometry
and noise levels confirm the feasibility of the deep learning inversion,
opening the possibility to estimate the subsurface resistivity distribution in
real time. | 1812.10247v1 |
2019-01-24 | Topological valley transport at the curved boundary of a folded bilayer graphene | The development of valleytronics demands long-range electronic transport with
preserved valley index, a degree of freedom similar to electron spin. A
promising structure for this end is a topological one-dimensional (1D) channel
formed in bilayer graphene (BLG) under special electrostatic conditions or
specific stacking configuration, called domain wall (DW). In these 1D channels,
the valley-index defines the propagation direction of the charge carriers and
the chiral edge states (kink states) are robust over many kinds of disorder.
However, the fabrication of DWs is challenging, requiring the design of complex
multi-gate structures or have been producing on rough substrates, showing a
limited mean free path. Here, we report on a high-quality DW formed at the
curved boundary of folded bilayer graphene (folded-BLG). At such 1D conducting
channel we measured a two-terminal resistance close to the quantum resistance
$R = e^2/4h$ at zero magnetic field, a signature of kink states. Our
experiments reveal a long-range ballistic transport regime that occurs only at
the DW of the folded-BLG, while the other regions behave like semiconductors
with tunable band gap. | 1901.08178v1 |
2019-06-12 | Record-High Proximity-Induced Anomalous Hall Effect in (Bi$_x$Sb$_{1-x}$)2Te$_3$ Thin Film Grown on CrGeTe$_3$ Substrate | Quantum anomalous Hall effect(QAHE) can only be realized at extremely low
temperatures in magnetically doped topological insulators(TIs) due to
limitations inherent with the doping precess. In an effort to boost the
quantization temperature of QAHE, magnetic proximity effect in magnetic
insulator/TI heterostructures has been extensively investigated. However, the
observed anomalous Hall resistance has never been more than several Ohms,
presumably owing to the interfacial disorders caused by the structural and
chemical mismatch. Here, we show that, by growing (BixSb1-x)2Te3(BST) thin
films on structurally and chemically well-matched, ferromagnetic-insulating
CeGeTe3(CGT) substrates, the proximity-induced anomalous Hall resistance can be
enhanced by more than an order of magnitude. This sheds light on the importance
of structural and chemical match for magnetic insulator/TI proximity systems. | 1906.05245v1 |
2019-06-24 | Mechanical characterization of cells and microspheres sorted by acoustophoresis with in-line resistive pulse sensing | Resistive Pulse Sensing (RPS) is a key label-free technology to measure
particles and single-cell size distribution. As a growing corpus of evidence
supports that cancer cells exhibit distinct mechanical phenotypes from healthy
cells, expanding the method from size to mechanical sensing could represent a
pertinent and innovative tool for cancer research. In this paper, we infer the
cells compressibility by using acoustic radiation pressure to deflect flowing
cells in a microchannel, and use RPS to sense the subpopulations of cells and
particles at each acoustic power level. We develop and validate a linear model
to analyze experimental data from a large number of particles. This
high-precision linear model is complemented by a more robust (yet less
detailed) statistical model to analyze datasets with fewer particles. Compared
to current acoustic cell phenotyping apparatus based on video cameras, the
proposed approach is not limited by the optical diffraction, frame rate, data
storage or processing speed, and may ultimately constitute a step forward
towards point-of-care acousto-electrical phenotyping and acoustic phenotyping
of nanoscale objects such as exosomes and viruses. | 1906.11944v1 |
2020-01-12 | Interpretation of the modulus spectra of organic field-effect transistors with electrode overlap and peripheral regions: determination of the electronic properties of the gate insulator and organic semiconductor | The modulus spectra of organic field-effect transistors (OFETs) with
electrode overlap and peripheral regions have been experimentally and
theoretically investigated. The complex impedance of regioregular
poly(3-hexylthiophene-2,5-diyl) (P3HT) OFETs with electrode overlap and
peripheral regions was measured with a frequency response analyzer. The complex
modulus was derived from an equivalent circuit of OFETs with overlap and
peripheral regions using a four-terminal matrix approach. The modulus spectra
of the P3HT OFETs were successfully fitted by those calculated using the
expression derived from the equivalent circuit. Three structures were found in
the modulus spectra of the P3HT OFETs owing to the dielectric properties of the
gate insulator, transport properties of the organic semiconductor, and contact
resistance from the low to high frequency ranges. The resistivity of the gate
insulators and the field-effect mobility of working OFETs were determined using
the values of the circuit components of the equivalent circuit obtained by
fitting. | 2001.03957v1 |
2020-05-05 | Resistance of Hall Sensors Based on Graphene to Neutron Radiation | An in-situ study of Hall sensors based on single-layered graphene in neutron
fluxes of a nuclear reactor to the fluence of 1.5e20 n/sq,m was conducted. The
sensitivity of the sensors to the magnetic field remained stable throughout the
experiment, while the resistance changes correlated with the increase in sample
temperature due to radiation heating. The experiment confirmed the theoretical
expectations regarding the high stability of graphene sensors to neutron
irradiation. Necessary further improvement of sensor technology to optimize
their characteristics, as well as radiation testing to determine the maximum
permissible neutron fluence. | 2005.01964v1 |
2020-05-12 | Superradiant Cherenkov-Wakefield radiation as THz source for FEL facilities | An electron beam passing through a tube which is lined on the inside with a
dielectric layer will radiate energy in the THz range due to the interaction
with the boundary. The resonant enhancement of certain frequencies is
conditioned by structure parameters as tube radius and permittivity of the
dielectric layer. In low loss structures narrow-band radiation is generated
which can be coupled out by suitable antennas. For higher frequencies the
coupling to the resistive outer metal layer becomes increasingly important. The
losses in the outer layer prohibit to reach high frequencies with narrow-band
conditions. Instead short broad-band pulses can be generated with still
attractive power levels. In the first section of the paper a general theory of
the impedance of a two-layer structure is presented and the coupling to the
outer resistive layer is discussed. Approximate relations for the radiated
energy, power and pulse length for a set of structure parameters are derived
and compared to numerical results in the following section. Finally first
numerical result of the out-coupling of the radiation by means of a Vlasov
antenna and estimates of the achieved beam quality are presented. | 2005.05640v1 |
2020-05-18 | Fmax = 270 GHz InAlN/GaN HEMT on Si with forming gas/nitrogen two-step annealing | In this letter, N2 and forming gas (FG) were used during ohmic contact
annealing of InAlN/GaN HEMTs on Si. It is found that N2 annealing offers lower
ohmic contact resistance (RC) while FG annealing features lower sheet
resistance (Rsheet). Then FG/N2 two-step annealing was used to achieve a
subthreshold swing (SS) of 113 mV/dec, an on/off current (Ion/Ioff) ratio of ~
106, a transconductance (gm) peak of 415 mS/mm, a record low drain-inducing
barrier lowing (DIBL) of 65 mV/V, and a record high power gain cutoff frequency
(fmax) of 270 GHz on 50-nm InAlN/GaN HEMT on Si. | 2005.08422v1 |
2020-05-18 | Machine learning for the diagnosis of early stage diabetes using temporal glucose profiles | Machine learning shows remarkable success for recognizing patterns in data.
Here we apply the machine learning (ML) for the diagnosis of early stage
diabetes, which is known as a challenging task in medicine. Blood glucose
levels are tightly regulated by two counter-regulatory hormones, insulin and
glucagon, and the failure of the glucose homeostasis leads to the common
metabolic disease, diabetes mellitus. It is a chronic disease that has a long
latent period the complicates detection of the disease at an early stage. The
vast majority of diabetics result from that diminished effectiveness of insulin
action. The insulin resistance must modify the temporal profile of blood
glucose. Thus we propose to use ML to detect the subtle change in the temporal
pattern of glucose concentration. Time series data of blood glucose with
sufficient resolution is currently unavailable, so we confirm the proposal
using synthetic data of glucose profiles produced by a biophysical model that
considers the glucose regulation and hormone action. Multi-layered perceptrons,
convolutional neural networks, and recurrent neural networks all identified the
degree of insulin resistance with high accuracy above $85\%$. | 2005.08701v1 |
2020-05-28 | Study of Streamer Development in Resistive Plate Chamber | This work has been carried out to simulate a Resistive Plate Chamber and
corroborate it with experimental measurements in order to develop a numerical
tool for studying the performance of the device for any gas mixture. This will
allow us to explore the feasibility of operating these chambers in their
avalanche mode within the Iron Calorimeter setup at India-based Neutrino
Observatory with any eco-friendly substitute. The simulation has considered a
hydrodynamic model of charge transport to emulate the electronic and ionic
growths in the device as a function of the applied voltage which determines its
working mode as either of the avalanche or streamer. In order to validate, the
simulation result has been compared with compatible experimental data available
in the literature. | 2005.13911v2 |
2020-06-20 | In-Memory Resistive RAM Implementation of Binarized Neural Networks for Medical Applications | The advent of deep learning has considerably accelerated machine learning
development. The deployment of deep neural networks at the edge is however
limited by their high memory and energy consumption requirements. With new
memory technology available, emerging Binarized Neural Networks (BNNs) are
promising to reduce the energy impact of the forthcoming machine learning
hardware generation, enabling machine learning on the edge devices and avoiding
data transfer over the network. In this work, after presenting our
implementation employing a hybrid CMOS - hafnium oxide resistive memory
technology, we suggest strategies to apply BNNs to biomedical signals such as
electrocardiography and electroencephalography, keeping accuracy level and
reducing memory requirements. We investigate the memory-accuracy trade-off when
binarizing whole network and binarizing solely the classifier part. We also
discuss how these results translate to the edge-oriented Mobilenet~V1 neural
network on the Imagenet task. The final goal of this research is to enable
smart autonomous healthcare devices. | 2006.11595v1 |
2020-07-03 | Surpassing the resistance quantum with a geometric superinductor | The superconducting circuit community has recently discovered the promising
potential of superinductors. These circuit elements have a characteristic
impedance exceeding the resistance quantum $R_\text{Q} \approx
6.45~\text{k}\Omega$ which leads to a suppression of ground state charge
fluctuations. Applications include the realization of hardware protected qubits
for fault tolerant quantum computing, improved coupling to small dipole moment
objects and defining a new quantum metrology standard for the ampere. In this
work we refute the widespread notion that superinductors can only be
implemented based on kinetic inductance, i.e. using disordered superconductors
or Josephson junction arrays. We present modeling, fabrication and
characterization of 104 planar aluminum coil resonators with a characteristic
impedance up to 30.9 $\text{k}\Omega$ at 5.6 GHz and a capacitance down to
$\leq1$ fF, with low-loss and a power handling reaching $10^8$ intra-cavity
photons. Geometric superinductors are free of uncontrolled tunneling events and
offer high reproducibility, linearity and the ability to couple magnetically -
properties that significantly broaden the scope of future quantum circuits. | 2007.01644v1 |
2020-07-17 | Breaking the quantum PIN code of atomic synapses | Atomic synapses represent a special class of memristors whose operation
relies on the formation of metallic nanofilaments bridging two electrodes
across an insulator. Due to the magnifying effect of this narrowest
cross-section on the device conductance, a nanometer scale displacement of a
few atoms grants access to various resistive states at ultimately low energy
costs, satisfying the fundamental requirements of neuromorphic computing
hardware. Yet, device engineering lacks the complete quantum characterization
of such filamentary conductance. Here we analyze multiple Andreev reflection
processes emerging at the filament terminals when superconducting electrodes
are utilized. Thereby the quantum PIN code, i.e. the transmission probabilities
of each individual conduction channel contributing to the conductance of the
nanojunctions is revealed. Our measurements on Nb$_2$O$_5$ resistive switching
junctions provide a profound experimental evidence that the onset of the high
conductance ON state is manifested via the formation of truly atomic-sized
metallic filaments. | 2007.09215v1 |
2020-07-21 | Granular packings with sliding, rolling and twisting friction | Intuition tells us that a rolling or spinning sphere will eventually stop due
to the presence of friction and other dissipative interactions. The resistance
to rolling and spinning/twisting torque that stops a sphere also changes the
microstructure of a granular packing of frictional spheres by increasing the
number of constraints on the degrees of freedom of motion. We perform discrete
element modeling simulations to construct sphere packings implementing a range
of frictional constraints under a pressure-controlled protocol. Mechanically
stable packings are achievable at volume fractions and average coordination
numbers as low as 0.53 and 2.5, respectively, when the particles experience
high resistance to sliding, rolling and twisting. Only when the particle model
includes rolling and twisting friction, were experimental volume fractions
reproduced. | 2007.10860v1 |
2020-07-27 | Unconventional bulk superconductivity in YFe$_2$Ge$_2$ single crystals | Using a new horizontal flux growth technique to produce high quality crystals
of the unconventional superconductor YFe$_2$Ge$_2$ has led to a seven-fold
reduction in disorder scattering, resulting in mm-sized crystals with residual
resistivities $\simeq \SI{0.45}{\micro\ohm\centi\meter}$, resistivity ratios
$\simeq 430$ and sharp superconducting heat capacity anomalies. This enables
searching multi-probe experiments investigating the normal and superconducting
states of YFe$_2$Ge$_2$. Low temperature heat capacity measurements suggest a
significant residual Sommerfeld coefficient, consistent with in-gap states
induced by residual disorder as predicted for a sign-changing order parameter. | 2007.13584v1 |
2020-08-28 | Superinsulators: a toy realization of QCD in condensed matter | Superinsulators are dual superconductors, dissipationless magnetic monopole
condensates with infinite resistance. The long-distance field theory of such
states of matter is QED with dynamical matter coupled via a compact BF
topological interaction. We will quantize the 2D model in the functional
Schr\"odinger picture and show how strong entanglement of charges leads to a
phase which is a single-color, asymptotically free version of QCD in which the
infinite resistance is caused by the linear confinement of charges. This phase
has been experimentally detected in TiN, NbTiN and InO thin films, including
signatures of asymptotically free behaviour and of the dual, electric Meissner
effect. This makes superinsulators a ``toy realization" of QCD with Cooper
pairs playing the role of quarks. | 2008.12541v1 |
2020-11-03 | Relativistic non-resistive viscous magnetohydrodynamics from the kinetic theory:a relaxation time approach | We derive the relativistic non-resistive, viscous second-order
magnetohydrodynamic equations for the dissipative quantities using the
relaxation time approximation. The Boltzmann equation is solved for a system of
particles and antiparticles using Chapman-Enskog like gradient expansion of the
single-particle distribution function truncated at second order. In the first
order, the transport coefficients are independent of the magnetic field. In the
second-order, new transport coefficients that couple magnetic field and the
dissipative quantities appear which are different from those obtained in the
14-moment approximation \cite{Denicol:2018rbw} in the presence of a magnetic
field. However, in the limit of the weak magnetic field, the form of these
equations are identical to the 14-moment approximation albeit with a different
values of these coefficients. We also derive the anisotropic transport
coefficients in the Navier-Stokes limit. | 2011.01606v1 |
2020-11-04 | First application of machine learning algorithms to the position reconstruction in Resistive Silicon Detectors | RSDs (Resistive AC-Coupled Silicon Detectors) are n-in-p silicon sensors
based on the LGAD (Low-Gain Avalanche Diode) technology, featuring a continuous
gain layer over the whole sensor area. The truly innovative feature of these
sensors is that the signal induced by an ionising particle is seen on several
pixels, allowing the use of reconstruction techniques that combine the
information from many read-out channels. In this contribution, the first
application of a machine learning technique to RSD devices is presented. The
spatial resolution of this technique is compared to that obtained with the
standard RSD reconstruction methods that use analytical descriptions of the
signal sharing mechanism. A Multi-Output regressor algorithm, trained with a
combination of simulated and real data, leads to a spatial resolution of less
than 2 $\mu m$ for a sensor with a 100 $\mu m$ pixel. The prospects of future
improvements are also discussed. | 2011.02410v3 |
2020-11-15 | Hidden Quantum Hall Stripes in Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As Quantum Wells | We report on transport signatures of hidden quantum Hall stripe (hQHS) phases
in high ($N > 2$) half-filled Landau levels of
Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As quantum wells with varying Al
mole fraction $x < 10^{-3}$. Residing between the conventional stripe phases
(lower $N$) and the isotropic liquid phases (higher $N$), where resistivity
decreases as $1/N$, these hQHS phases exhibit isotropic and $N$-independent
resistivity. Using the experimental phase diagram we establish that the stripe
phases are more robust than theoretically predicted, calling for improved
theoretical treatment. We also show that, unlike conventional stripe phases,
the hQHS phases do not occur in ultrahigh mobility GaAs quantum wells, but are
likely to be found in other systems. | 2011.07563v1 |
2020-11-26 | Spin-Torsion effect on collapsing of first generation stars into neutron stars rather than black holes in Einstein-Cartan-Sciama-Kibble theory | In this project, we try to find the correlation between the non-local
pressure inside the massive neutron stars resisting the gravitational collapse
of the core and ECSK dark energy led by the effect of spin-torsion coupling
between quark fields and the space-time at very high densities much larger than
the nuclear density. The injection of dark energy into the core of massive
neutron stars (MANs) and extra resistant nature of this dark energy to the
collapse of MANs by the anti-gravity give the possibility of existence of
neutron stars in the unobserved mass range of $[2.16M_{\odot},5M_{\odot}]$.
Obtaining the ECSK TOV equation gives the local pressure of the ambient medium
of MANs. Moreover, the negative pressure from the ECSK dark energy is obtained
from the Lagrangian again, from which we are able to investigate the
hydro-static equilibrium of the core and ambient medium of the MANs. If the
equilibrium state is satisfied for the unobserved mass gap for the MANs in ECSK
theory framework this will imply our model predicts this vast mass range of
unobserved spectrum of the MANs in astrophysical studies. | 2012.01131v1 |
2020-12-07 | Van der Waals Multiferroic Tunnel Junctions | Multiferroic tunnel junctions (MFTJs) have aroused significant interest due
to their functional properties useful for non-volatile memory devices. So far,
however, all the existing MFTJs have been based on perovskite-oxide
heterostructures limited by a relatively high resistance-area (RA) product
unfavorable for practical applications. Here, using first-principles
calculations, we explore spin-dependent transport properties of van der Waals
(vdW) MFTJs which consist of two-dimensional (2D) ferromagnetic FenGeTe2 (n =
3, 4, 5) electrodes and 2D ferroelectric In2Se3 barrier layers. We demonstrate
that such FemGeTe2/In2Se3/FenGeTe2 (m, n = 3, 4, 5) MFTJs exhibit multiple
non-volatile resistance states associated with different polarization
orientation of the ferroelectric In2Se3 layer and magnetization alignment of
the two ferromagnetic FenGeTe2 layers. We find a remarkably low RA product
which makes the proposed vdW MFTJs superior to the conventional MFTJs in terms
of their promise for non-volatile memory applications. | 2012.03546v1 |
2020-12-28 | Excitation spectra of quantum matter without quasiparticles II: random $t$-$J$ models | We present numerical solutions of the spectral functions of $t$-$J$ models
with random and all-to-all exchange and global SU($M$) spin rotation symmetry.
The solutions are obtained from the saddle-point equations of the large volume
limit, followed by the large $M$ limit. These saddle point equations involve
Green's functions for fractionalized spinons and holons carrying emergent U(1)
gauge charges, obeying relations similar to those of the Sachdev-Ye-Kitaev
(SYK) models. The low frequency spectral functions are compared with an
analytic analysis of the operator scaling dimensions, with good agreement. We
also compute the low frequency and temperature behavior of gauge-invariant
observables: the electron Green's function, the local spin susceptibility and
the optical conductivity; along with the temperature dependence of the d.c.
resistivity. The time reparameterization soft mode (equivalent to the boundary
graviton in holographically dual models of two-dimensional quantum gravity)
makes important contributions to all observables, and provides a
linear-in-temperature contribution to the d.c. resistivity. | 2012.14449v1 |
2020-12-31 | Linear-in-$T$ resistivity from semiholographic non-Fermi liquid models | We construct a semiholographic effective theory in which the electron of a
two-dimensional band hybridizes with a fermionic operator of a critical
holographic sector, while also interacting with other bands that preserve
quasiparticle characteristics. Besides the scaling dimension $\nu$ of the
fermionic operator in the holographic sector, the effective theory has two
{dimensionless} couplings $\alpha$ and $\gamma$ determining the holographic and
Fermi-liquid-type contributions to the self-energy respectively. We find that
irrespective of the choice of the holographic critical sector, there exists a
ratio of the effective couplings for which we obtain linear-in-$T$ resistivity
for a wide range of temperatures. This scaling persists to arbitrarily low
temperatures when $\nu$ approaches unity in which limit we obtain a marginal
Fermi liquid with a specific temperature dependence of the self-energy. | 2012.15679v3 |
2021-02-05 | Cross-Code verification and sensitivity analysis to effectively model the electrothermal instability | This manuscript presents verification cases that are developed to study the
electrothermal instability (ETI). Specific verification cases are included to
ensure that the unit physics components necessary to model the ETI are
accurate, providing a path for fluid-based codes to effectively simulate ETI in
the linear and nonlinear growth regimes. Two software frameworks with different
algorithmic approaches are compared for accuracy in their ability to simulate
diffusion of a magnetic field, linear growth of the ETI, and a fully nonlinear
ETI evolution. The nonlinear ETI simulations show early time agreement, with
some differences emerging, as noted in the wavenumber spectrum, late into the
nonlinear development of ETI. A sensitivity study explores the role of
equation-of-state (EOS), vacuum density, and vacuum resistivity. EOS and vacuum
resistivity are found to be the most critical factors in the modeling of
nonlinear ETI development. | 2102.03378v1 |
2021-02-20 | Deformation Mechanics of Self-expanding Venous Stents: Modelling and Experiments | Deformation properties of venous stents based on braided design, chevron
design, Z design, and diamond design are compared using in vitro experiments
coupled with analytical and finite element modelling. Their suitability for
deployment in different clinical contexts is assessed based on their
deformation characteristics. Self-expanding stainless steel stents possess
superior collapse resistance compared to Nitinol stents. Consequently, they may
be more reliable to treat diseases like May-Thurner syndrome in which
resistance against a concentrated (pinching) force applied on the stent is
needed to prevent collapse. Braided design applies a larger radial pressure
particularly for vessels of diameter smaller than 75% of its nominal diameter,
making it suitable for a long lesion with high recoil. Z design has the least
foreshortening, which aids in accurate deployment. Nitinol stents are more
compliant than their stainless steel counterparts, which indicates their
suitability in veins. The semi-analytical method presented can aid in rapid
assessment of topology governed deformation characteristics of stents and their
design optimization | 2102.10219v1 |
2021-03-09 | Coulomb drag between two strange metals | We study the Coulomb drag between two strange-metal layers using the
Einstein-Maxwell-Dilaton model from holography. We show that the
low-temperature dependence of the drag resistivity is $\rho_D \propto T^4$,
which strongly deviates from the quadratic dependence of Fermi liquids. We also
present numerical results at room temperature, using typical parameters of the
cuprates, to provide an estimate of the magnitude of this effect for future
experiments. We find that the drag resistivity is enhanced by the plasmons
characteristic of the two-layer system. | 2103.05652v3 |
2021-03-29 | Electrical conductivity of strongly magnetized dense quark matter -- possibility of quantum hall effect | We have pointed out the possibility of quantum Hall effect or quantum
patterns of transportation in a degenerate strongly magnetized quark matter,
which might be expected inside a highly dense compact star. An anisotropic
pattern of electrical conductivity and resistivity tensor in classical and
quantum cases is explored by considering cyclotron motion and Landau
quantization respectively. With increasing magnetic field, classical to quantum
transitions are realized through enhanced/reduced resistivity/conductivity with
jumping pattern. Considering QCD relaxation time scale of 10 fm, $eB\approx
(1-4) m_\pi^2$ might be considered as strong magnetic field for massless and
degenerate quark matter with quark chemical potential $\mu\approx 0.2-0.4$ GeV.
Beyond these threshold ranges of magnetic field, perpendicular motion of quarks
might be stopped and 3 $\rightarrow$ 1 dimensionally reduced conduction picture
might be established. | 2103.15364v1 |
2021-03-30 | Noise-resistant Deep Metric Learning with Ranking-based Instance Selection | The existence of noisy labels in real-world data negatively impacts the
performance of deep learning models. Although much research effort has been
devoted to improving robustness to noisy labels in classification tasks, the
problem of noisy labels in deep metric learning (DML) remains open. In this
paper, we propose a noise-resistant training technique for DML, which we name
Probabilistic Ranking-based Instance Selection with Memory (PRISM). PRISM
identifies noisy data in a minibatch using average similarity against image
features extracted by several previous versions of the neural network. These
features are stored in and retrieved from a memory bank. To alleviate the high
computational cost brought by the memory bank, we introduce an acceleration
method that replaces individual data points with the class centers. In
extensive comparisons with 12 existing approaches under both synthetic and
real-world label noise, PRISM demonstrates superior performance of up to 6.06%
in Precision@1. | 2103.16047v2 |
2021-04-09 | Piracy-Resistant DNN Watermarking by Block-Wise Image Transformation with Secret Key | In this paper, we propose a novel DNN watermarking method that utilizes a
learnable image transformation method with a secret key. The proposed method
embeds a watermark pattern in a model by using learnable transformed images and
allows us to remotely verify the ownership of the model. As a result, it is
piracy-resistant, so the original watermark cannot be overwritten by a pirated
watermark, and adding a new watermark decreases the model accuracy unlike most
of the existing DNN watermarking methods. In addition, it does not require a
special pre-defined training set or trigger set. We empirically evaluated the
proposed method on the CIFAR-10 dataset. The results show that it was resilient
against fine-tuning and pruning attacks while maintaining a high
watermark-detection accuracy. | 2104.04241v1 |
2021-04-19 | Intermittent current interruption method for commercial lithium ion batteries aging characterization | In this article, a pioneering study is presented where the intermittent
current interruption method is used to characterize the aging behavior of
commercial lithium ion batteries. With a very resource-efficient
implementation, this method can track the battery resistive and diffusive
behaviors over the entire state of charge range and be able to determine the
aging throughout the lifetime of the batteries. In addition, the incremental
capacity analysis can be carried out with the same data set. This method can
provide measurement results with a high repeatability and produce equivalent
information as the electrochemical impedance spectroscopy method. In this
study, both the resistive and diffusive parameters increase with the battery
capacity fading. This method does not require advanced test equipment and even
with a 0.1 Hz sampling frequency, it is possible to extract usable parameters
by prolonging the interruption length. Therefore, it has the potential to be
easily implemented in the charging sequence in electric vehicles or stationary
storage batteries for aging diagnostics. | 2104.09260v3 |
2021-05-17 | StRETcH: a Soft to Resistive Elastic Tactile Hand | Soft optical tactile sensors enable robots to manipulate deformable objects
by capturing important features such as high-resolution contact geometry and
estimations of object compliance. This work presents a variable stiffness soft
tactile end-effector called StRETcH, a Soft to Resistive Elastic Tactile Hand,
that is easily manufactured and integrated with a robotic arm. An elastic
membrane is suspended between two robotic fingers, and a depth sensor capturing
the deformations of the elastic membrane enables sub-millimeter accurate
estimates of contact geometries. The parallel-jaw gripper varies the stiffness
of the membrane by uni-axially stretching it, which controllably modulates
StRETcH's effective modulus from approximately 4kPa to 9kPa. This work uses
StRETcH to reconstruct the contact geometry of rigid and deformable objects,
estimate the stiffness of four balloons filled with different substances, and
manipulate dough into a desired shape. | 2105.08154v1 |
2021-05-26 | Temperature Damping of Magneto-Intersubband Resistance Oscillations in Magnetically Entangled Subbands | Magneto-intersubband resistance oscillations (MISO) of highly mobile 2D
electrons in symmetric GaAs quantum wells with two populated subbands are
studied in magnetic fields tilted from the normal to the 2D electron layer at
different temperatures $T$. Decrease of MISO amplitude with temperature
increase is observed. At moderate tilts the temperature decrease of MISO
amplitude is consistent with decrease of Dingle factor due to reduction of
quantum electron lifetime at high temperatures. At large tilts new regime of
strong MISO suppression with the temperature is observed. Proposed model
relates this suppression to magnetic entanglement between subbands, leading to
beating in oscillating density of states. The model yields corresponding
temperature damping factor: $A_{MISO}(T)=X/\sinh(X)$, where $X=2\pi^2kT\delta
f$ and $\delta f$ is difference frequency of oscillations of density of states
in two subbands. This factor is in agreement with experiment. Fermi liquid
enhancement of MISO amplitude is observed. | 2105.12263v1 |
2021-06-12 | RF surface resistance tuning of superconducting niobium via thermal diffusion of native oxide | Recently, Nb superconducting radio frequency cavities vacuum heat treated
between 300-400 C for a few hours have exhibited very high quality factors
(~5x10^10 at 2.0 K). New secondary ion mass spectrometry measurements of O, N
and C show this enhancement in RF surface conductivity is primarily associated
with interstitial O alloying via dissolution and diffusion of the native oxide.
We use a theory of oxide decomposition and O diffusion to quantify previously
unknown parameters crucial in modeling this process. RF measurements of a
vacuum heat treated Nb superconducting radio frequency cavity confirm the
minimized surface resistance (higher Q0) previously expected only from 800 C
diffusive alloying with N. | 2106.06647v2 |
2021-09-07 | A Novel Manufacturing Process for Glass THGEMs and First Characterisation in an Optical Gaseous Argon TPC | This paper details a novel, patent pending, abrasive machining manufacturing
process for the formation of sub-millimetre holes in THGEMs, with the intended
application in gaseous and dual-phase TPCs. Abrasive machining favours a
non-ductile substrate such as glasses or ceramics. This innovative
manufacturing process allows for unprecedented versatility in THGEM substrates,
electrodes, and hole geometry and pattern. Consequently, THGEMs produced via
abrasive machining can be tailored for specific properties, for example: high
stiffness, low total thickness variation, radiopurity, moisture
absorption/outgassing and/or carbonisation resistance. This paper specifically
focuses on three glass substrate THGEMs (G-THGEMs) made from Schott Borofloat
33 and Fused Silica. Circular and hexagonal hole shapes are also investigated.
The G-THGEM electrodes are made from Indium Tin Oxide (ITO), with a resistivity
of 150 $\Omega$/Sq. All G-THGEMs were characterised in an optical (EMCCD)
readout GArTPC, and compared to a traditionally manufactured FR4 THGEM, with
their charging and secondary scintillation (S2) light production behaviour
analysed. | 2109.02910v2 |
2021-09-17 | Less is more: more scattering leading to less resistance | We study the breaking of integrability by a finite density of dilute
impurities, specifically the emerging diffusive transport. Provided the
distance between impurities (localized perturbations) is large, one would
expect that the scattering rates are additive, and therefore, the resistivity
is proportional to the number of impurities (the so-called Matthiessen's rule).
We show that this is, in general, not the case. If transport is anomalous in
the original integrable system without impurities, the diffusion constant in
the non-integrable system at low impurity density gets a nontrivial power-law
dependence on the impurity density, with the power being determined by the
dynamical scaling exponent of anomalous transport. We also find a regime at
high impurity density in which, counterintuitively, adding more impurities to
an already diffusive system increases transport rather than decreases it. | 2109.08390v2 |
2021-09-17 | Long-term evolution of neutron-star merger remnants in general relativistic resistive-magnetohydrodynamics with a mean-field dynamo term | Long-term neutrino-radiation resistive-magnetohydrodynamics simulations in
full general relativity are performed for a system composed of a massive
neutron star and a torus formed as a remnant of binary neutron star mergers.
The simulation is performed in axial symmetry incorporating a mean-field dynamo
term for a hypothetical amplification of the magnetic-field strength. We first
calibrate the mean-field dynamo parameters by comparing the results for the
evolution of black hole-disk systems with viscous hydrodynamics results. We
then perform simulations for the system of a remnant massive neutron star and a
torus. As in the viscous hydrodynamics case, the mass ejection occurs primarily
from the torus surrounding the massive neutron star. The total ejecta mass and
electron fraction in the new simulation are similar to those in the viscous
hydrodynamics case. However, the velocity of the ejecta can be significantly
enhanced by magnetohydrodynamics effects caused by global magnetic fields. | 2109.08732v1 |
2021-09-20 | Fast Online Optimization for Terrain-Blind Bipedal Robot Walking with a Decoupled Actuated SLIP Model | We present a highly reactive controller which enables bipedal robots to
blindly walk over various kinds of uneven terrains while resisting pushes. The
high level motion planner does fast online optimization for footstep locations
and Center of Mass (CoM) height using the decoupled actuated Spring Loaded
Inverted Pendulum (aSLIP) model. The decoupled aSLIP model simplifies the
original aSLIP with Linear Inverted Pendulum (LIP) dynamics in horizontal
states and spring dynamics in the vertical state. The motion planning can be
formulated as a discrete-time Model Predictive Control (MPC) and solved at a
frequency of 1k~HZ. The output of the motion planner using a reduced-order
model is fed into an inverse-dynamics based whole body controller for execution
on the robot. A key result of this controller is that the foot of the robot is
compliant, which further extends the robot's ability to be robust to unobserved
terrain changes. We evaluate our method in simulation with the bipedal robot
SLIDER. Results show the robot can blindly walk over various uneven terrains
including slopes, wave fields and stairs. It can also resist pushes while
walking on uneven terrain. | 2109.09373v1 |
2021-11-15 | Copper Large-scale Grain Growth by UV Nanosecond Pulsed Laser Annealing | UV nanosecond pulsed laser annealing (UV NLA) enables both surface-localized
heating and short timescale high temperature processing, which can be
advantageous to reduce metal line resistance by enlarging metal grains in lines
or in thin films, while maintaining the integrity and performance of
surrounding structures. In this work UV NLA is applied on a typical Cu thin
film, demonstrating a mean grain size of over 1 {\mu}m and 400 nm in a melt and
sub-melt regime, respectively. Along with such grain enlargement, film
resistivity is also reduced. | 2111.07580v1 |
2021-11-26 | Absence versus Presence of Dissipative Quantum Phase Transition in Josephson Junctions | Dissipative quantum phase transition has been widely believed to occur in a
Josephson junction coupled to a resistor despite a lack of concrete
experimental evidence. Here, on the basis of both numerical and analytical
nonperturbative renormalization group (RG) analyses, we reveal breakdown of
previous perturbative arguments and defy the common wisdom that the transition
always occurs at the quantum resistance $R_{Q} \!=\! h/(4e^2)$. We find that RG
flows in nonperturbative regimes induce nonmonotonic renormalization of the
charging energy and lead to a qualitatively different phase diagram, where the
insulator phase is strongly suppressed to the deep charge regime (Cooper pair
box), while the system is always superconducting in the transmon regime. We
identify a previously overlooked dangerously irrelevant term as an origin of
the failure of conventional understandings. Our predictions can be tested in
recent experiments realizing high-impedance long superconducting waveguides and
would provide a solution to the long-standing controversy about the fate of
dissipative quantum phase transition in the resistively shunted Josephson
junction. | 2111.13710v3 |
2021-12-02 | Effective model and Magnetic Properties of the Resistive Electron Quadrupling State | Recent experiments [V.~Grinenko {\it et al.} {Nat. Phys. {\bf 17}, 1254
(2021)}; \url{http://doi.org/10.1038/s41567-021-01350-9}] reported the
observation of a condensate of four-fermion composites. This is a resistive
state that spontaneously breaks the time-reversal symmetry, leading to
unconventional magnetic properties, detected in muon spin rotation experiments
and by the appearance of a spontaneous Nernst effect. In this work, we derive
an effective model for the four-fermion order parameter that describes the
observed spontaneous magnetic fields in this state. We show that this model,
which is alike to the Faddeev-Skyrme model can host skyrmions:
magnetic-flux-carrying topological excitations. | 2112.01286v2 |
2021-12-06 | A stableness of resistance model for nonresponse adjustment with callback data | Nonresponse arises frequently in surveys and follow-ups are routinely made to
increase the response rate. In order to monitor the follow-up process, callback
data have been used in social sciences and survey studies for decades. In
modern surveys, the availability of callback data is increasing because the
response rate is decreasing and follow-ups are essential to collect maximum
information. Although callback data are helpful to reduce the bias in surveys,
such data have not been widely used in statistical analysis until recently. We
propose a stableness of resistance assumption for nonresponse adjustment with
callback data. We establish the identification and the semiparametric
efficiency theory under this assumption, and propose a suite of semiparametric
estimation methods including a doubly robust one, which generalize existing
parametric approaches for callback data analysis. We apply the approach to a
Consumer Expenditure Survey dataset. The results suggest an association between
nonresponse and high housing expenditures. | 2112.02822v3 |
2021-12-29 | Geometric interference in a high-mobility graphene annulus p-n junction device | The emergence of interference is observed in the resistance of a graphene
annulus pn junction device as a result of applying two separate gate voltages.
The observed resistance patterns are carefully inspected, and it is determined
that the position of the peaks resulting from those patterns are independent of
temperature and magnetic field. Furthermore, these patterns are not
attributable to Aharonov-Bohm oscillations, Fabry Perot interference at the
junction, or moir\'e potentials. The device data are compared with those of
another device fabricated with a traditional Hall bar geometry, as well as with
quantum transport simulation data. Since the two devices are of different
topological classes, the subtle differences observed in the corresponding
measured data indicate that the most likely source of the observed geometric
interference patterns is quantum scarring. | 2112.14614v1 |
2022-03-26 | A construction of exotic metallic states | We discuss examples of two dimensional metallic states with charge
fractionalization, and we will demonstrate that the mechanism of charge
fractionalization leads to exotic metallic behaviors at low and intermediate
temperature. The simplest example of such state is constructed by fermionic
partons at finite density coupled to a $Z_N$ gauge field, whose properties can
be studied through rudimentary methods. This simple state has the following
exotic features: (1) at low temperature this state is a "bad metal" whose
resistivity can exceed the Mott-Ioffe-Regel limit; (2) while increasing
temperature $T$ the resistivity $\rho(T)$ is a nonmonotonic function, and it
crosses over from a bad metal at low $T$ to a good metal at relatively high
$T$; (3) the optical conductivity $\sigma(\omega)$ has a small Drude weight at
low $T$, and a larger Drude weight at intermediate $T$; (4) at low temperature
the metallic state has a large Lorenz number, which strongly violates the
Wiedemann-Franz law. A more complex example with fermionic partons at finite
density coupled to a SU(N) gauge field will also be constructed. | 2203.14168v1 |
2022-04-07 | Using electrical resistance asymmetries to infer the geometric shapes of foundry patterned nanophotonic structures | While silicon photonics has leveraged the nanofabrication tools and
techniques from the microelectronics industry, it has also inherited the
metrological methods from the same. Photonics fabrication is inherently
different from microelectronics in its intrinsic sensitivity to 3D shape and
geometry, especially in a high-index contrast platform like
silicon-on-insulator. In this work, we show that electrical resistance
measurements can in principle be used to infer the geometry of such
nanophotonic structures and reconstruct the micro-loading curves of foundry
etch processes. We implement our ideas to infer 3D geometries from a standard
silicon photonics foundry and discuss some of the potential sources of error
that need to be calibrated out to improve the reconstruction accuracy. | 2204.03591v1 |
2022-04-12 | Biermann Battery Powered by Resistive Heating Induced by Cosmic Ray Streaming | It is recently proposed that cosmic rays generate a seed magnetic field in
the early universe. In this paper, we propose another generation mechanism of
magnetic fields by cosmic rays, which is the Biermann battery driven by
resistive heating induced by the streaming of cosmic rays. This mechanism is
dominant in small-scale, low-temperature, and strongly-ionized regions,
compared with other previously proposed mechanisms. Because cosmic rays are
expected to be accelerated after the death of the first stars, this mechanism
can work during structure formation in the early universe. We show that it
makes the seed magnetic field with sufficient strength for the subsequent
dynamo to amplify it to the micro Gauss level in the current galaxies. | 2204.05787v2 |
2022-06-15 | Demonstration of high sensitivity of microwave-induced resistance oscillations to circular polarization | We demonstrate that long-debated immunity of microwave-induced resistance
oscillations (MIRO) to the sense of circular polarization is not a generic
property of this phenomenon in solid-state two-dimensional electron systems.
Using a large-area GaAs-based heterostructure we detect up to 30 times larger
MIRO signal for the cyclotron resonance (CR) active helicity, fully consistent
with the concurrently measured transmission and the deduced CR shape of the
Drude absorption. We further elaborate conditions to avoid extrinsic factors
capable of producing an apparent immunity of the photoresponse. | 2206.07600v2 |
2022-07-04 | Granular Effect on Electron Conduction in Discontinuous Metal Films | We reanalyze the seminal work by Dolan and Osheroff [Phys. Rev. Lett.
$\textbf{43}$, 721 (1979)] which reported anomalous low-temperature conduction
of high-resistivity thin-film metal strips. We argue that the observed
logarithmic increase of resistance with decreasing temperature in their
3-nm-thick Au-Pd strips be ascribed to the granularity effect on electron
conduction in discontinuous metal films. This reanalysis is further supported
by our measurements on conducting Pb$_x$(SiO$_2$)$_{1-x}$ nanogranular films,
where $x$ is the volume fraction of Pb. | 2207.02304v2 |
2022-07-23 | Bandwidth-Hard Functions from Random Permutations | ASIC hash engines are specifically optimized for parallel computations of
cryptographic hashes and thus a natural environment for mounting brute-force
attacks on hash functions. Two fundamental advantages of ASICs over general
purpose computers are the area advantage and the energy efficiency. The
memory-hard functions approach the problem by reducing the area advantage of
ASICs compared to general-purpose computers. Traditionally, memory-hard
functions have been analyzed in the (parallel) random oracle model. However, as
the memory-hard security game is multi-stage, indifferentiability does not
apply and instantiating the random oracle becomes a non-trivial problem. Chen
and Tessaro (CRYPTO 2019) considered this issue and showed how random oracles
should be instantiated in the context of memory-hard functions. The
Bandwidth-Hard functions, introduced by Ren and Devadas (TCC 2017), aim to
provide ASIC resistance by reducing the energy advantage of ASICs. In
particular, bandwidth-hard functions provide ASIC resistance by guaranteeing
high run time energy cost if the available cache is not large enough.
Previously, bandwidth-hard functions have been analyzed in the parallel random
oracle model. In this work, we show how those random oracles can be
instantiated using random permutations in the context of bandwidth-hard
functions. Our results are generic and valid for any hard-to-pebble graphs. | 2207.11519v1 |
2022-08-10 | Spin and valley effects on the quantum phase transition in two dimensions | Using several independent methods, we find that the metal-insulator
transition occurs in the strongly-interacting two-valley two-dimensional
electron system in ultra-high mobility SiGe/Si/SiGe quantum wells in zero
magnetic field. The transition survives in this system in parallel magnetic
fields strong enough to completely polarize the electrons' spins, thus making
the electron system "spinless". In both cases, the resistivity on the metallic
side near the transition increases with decreasing temperature, reaches a
maximum at a temperature $T_{\text{max}}$, and then decreases. The decrease
reaches more than an order of magnitude in zero magnetic field. The value of
$T_{\text{max}}$ in zero magnetic field is found to be close to the
renormalized Fermi temperature. However, rather than increasing along with the
Fermi temperature, the value $T_{\text{max}}$ decreases appreciably for
spinless electrons in spin-polarizing magnetic fields. The observed behavior of
$T_{\text{max}}$ cannot be described by existing theories. The results indicate
the spin-related origin of the effect. At the same time, the low-temperature
resistivity drop in both spin-unpolarized and spinless electron systems is
described quantitatively by the dynamical mean-field theory. | 2208.05356v1 |
2022-09-19 | Adaptive 3D Mesh Steganography Based on Feature-Preserving Distortion | 3D mesh steganographic algorithms based on geometric modification are
vulnerable to 3D steganalyzers. In this paper, we propose a highly adaptive 3D
mesh steganography based on feature-preserving distortion (FPD), which
guarantees high embedding capacity while effectively resisting 3D steganalysis.
Specifically, we first transform vertex coordinates into integers and derive
bitplanes from them to construct the embedding domain. To better measure the
mesh distortion caused by message embedding, we propose FPD based on the most
effective sub-features of the state-of-the-art steganalytic feature set. By
improving and minimizing FPD, we can efficiently calculate the optimal
vertex-changing distribution and simultaneously preserve mesh features, such as
steganalytic and geometric features, to a certain extent. By virtue of the
optimal distribution, we adopt the Q-layered syndrome trellis coding (STC) for
practical message embedding. However, when Q varies, calculating bit
modification probability (BMP) in each layer of Q-layered will be cumbersome.
Hence, we contrapuntally design a universal and automatic BMP calculation
approach. Extensive experimental results demonstrate that the proposed
algorithm outperforms most state-of-the-art 3D mesh steganographic algorithms
in terms of resisting 3D steganalysis. | 2209.08884v1 |
2022-10-10 | A general efficiency relation for molecular machines | Living systems efficiently use chemical fuel to do work, process information,
and assemble patterns despite thermal noise. Whether high efficiency arises
from general principles or specific fine-tuning is unknown. Here, applying a
recent mapping from nonequilibrium systems to battery-resistor circuits, I
derive an analytic expression for the efficiency of any dissipative molecular
machine driven by one or a series of chemical potential differences. This
expression disentangles the chemical potential from the machine's details,
whose effect on the efficiency is fully specified by a constant called the load
resistance. The efficiency passes through a switch-like inflection point if the
balance between chemical potential and load resistance exceeds thermal noise.
Therefore, dissipative chemical engines qualitatively differ from heat engines,
which lack threshold behavior. This explains all-or-none dynein stepping with
increasing ATP concentration observed in single-molecule experiments. These
results indicate that biomolecular energy transduction is efficient not because
of idosyncratic optimization of the biomolecules themselves, but rather because
the concentration of chemical fuel is kept above a threshold level within
cells. | 2210.04380v1 |
2022-10-18 | A survey of open questions in adaptive therapy: bridging mathematics and clinical translation | Adaptive therapy is a dynamic cancer treatment protocol that updates (or
"adapts") treatment decisions in anticipation of evolving tumor dynamics. This
broad term encompasses many possible dynamic treatment protocols of
patient-specific dose modulation or dose timing. Adaptive therapy maintains
high levels of tumor burden to benefit from the competitive suppression of
treatment-sensitive subpopulations on treatment-resistant subpopulations. This
evolution-based approach to cancer treatment has been integrated into several
ongoing or planned clinical trials, including treatment of metastatic castrate
resistant prostate cancer, ovarian cancer, and BRAF-mutant melanoma. In the
previous few decades, experimental and clinical investigation of adaptive
therapy has progressed synergistically with mathematical and computational
modeling. In this work, we discuss 11 open questions in cancer adaptive therapy
mathematical modeling. The questions are split into three sections: 1) the
necessary components of mathematical models of adaptive therapy 2) design and
validation of dosing protocols, and 3) challenges and opportunities in clinical
translation. | 2210.12062v1 |
2022-10-26 | Access Service Records Based Trust Management Scheme for Internet of Things | The distributed structure of the Internet of things has gradually replaced
the centralized structure because of its scalability, security, and single
point of failure. The huge scale of information recording of the Internet of
things brings challenges and opportunities to the trust management of the
Internet of things. Through the analysis of a variety of existing trust
management schemes, this paper proposes a unified data structure for
distributed access service records, TokenChain, in which triple DES data
encryption is used to ensure privacy and traceability, to achieve a unified
trust management scheme. Based on TokenChain, a three-tier trust management
architecture (TokenChain-Based Trust Management, TBTM) is implemented in the
data layer, computing layer, and control layer. Trust evaluation is affected by
four statistics and finally converges to a real value under certain conditions.
Based on TBTM, we carry out theoretical analysis, malicious attack resistance,
simulation, and performance evaluation in various complex scenarios. The
results show that TBTM satisfies service prediction, global trust analysis,
high security, and excellent performance in multi-domain complex scenarios.
Compared with the existing trust management schemes, TBTM realizes
cross-scenario interaction and two-way trust management, and simultaneously
meets the characteristics of traceability, tamper-proof, attack resistance, and
distribution. Finally, this paper is summarized. | 2210.14566v1 |
2022-11-13 | Negative differential thermal resistance of fluids induced by heat baths | It has recently been shown that in one-dimensional hard-point gases, there is
a mechanism that induces negative differential thermal resistance (NDTR)
between heat baths. We examine this mechanism in more general higher
dimensional fluids described by multiparticle collision dynamics. We consider
fluids in a finite cuboid region of three-dimensional space with each end in
contact with a heat bath. Based on analytical results and numerical models, we
find that the mechanism underlying NDTR also works for high-dimensional fluidic
systems with weak interactions and is very robust to mixed fluids. Our results
significantly advance knowledge of NDTR induced by heat bath and illuminate new
directions to explore in fabricating fluid thermal transistors in micro- and
nanosystems. | 2211.06872v1 |
2022-11-16 | Coherent interlayer coupling in quasi-two-dimensional Dirac fermions in $α$-(BEDT-TTF)$_2$I$_3$ | Theoretical and experimental studies have supported that the electronic
structure of $\alpha$-(BEDT-TTF)$_2$I$_3$ under pressure is described by
two-dimensional Dirac fermions. When the interlayer tunneling is coherent, the
electronic structure of the system becomes three-dimensional, and we expect the
peak structure to appear in the interlayer resistivity under magnetic fields.
We theoretically and experimentally show that the peak appears in the
interlayer resistivity at low temperatures and high magnetic fields. From the
experiment, we estimate that the magnitude of the interlayer tunneling is $t_1
\sim 1$ meV. Our result opens the door to investigating the three-dimensional
electronic structure of $\alpha$-(BEDT-TTF)$_2$I$_3$. | 2211.08730v2 |
2023-03-02 | Random telegraph fluctuations in granular microwave resonators | Microwave circuit electrodynamics of disordered superconductors is a very
active research topic spawning a wide range of experiments and applications.
For compact superconducting circuit elements, the transition to an insulating
state poses a limit to the maximum attainable kinetic inductance. It is
therefore vital to study the fundamental noise properties of thin films close
to this transition, particularly in situations where a good coherence and
temporal stability is required. In this paper, we present measurements on
superconducting granular aluminum microwave resonators with high normal state
resistances, where the influence of the superconductor to insulator phase
transition is visible. We trace fluctuations of the fundamental resonance
frequency and observe, in addition to a 1/f noise pattern, a distinct excess
noise, reminiscent of a random telegraph signal. The excess noise shows a
strong dependency on the resistivity of the films as well as the sample
temperature, but not on the applied microwave power. | 2303.01079v1 |
2023-03-28 | Anomalous superconducting diode effect in a polar superconductor | A superconductor with broken time reversal and inversion symmetry may exhibit
nonreciprocal charge transport, including a nonreciprocal critical current,
also known as superconducting diode effect. We report an intrinsic
superconducting diode effect in a polar strontium titanate film. Differential
resistance measurements reveal a superconducting state whose depairing current
is polarity dependent. There is, however, no measurable deviation from Ohmic
behavior, implying that this state does not arise from a bulk magnetochiral
anisotropy. In the entire measurement range, the only deviation from linearity
in the differential resistance is on the edge of the superconducting transition
at high magnetic fields, likely due to the motion of flux vortices.
Furthermore, the magnitude of the effect is preserved even when the in-plane
magnetic field is oriented parallel to the current, indicating that this effect
truly does not originate from a bulk magnetochiral anisotropy. | 2303.16238v1 |
2023-05-16 | Gate-tunable multiband transport in ZrTe5 thin devices | Interest in ZrTe5 has been reinvigorated in recent years owing to its
potential for hosting versatile topological electronic states and intriguing
experimental discoveries. However, the mechanism of many of its unusual
transport behaviors remains controversial, for example, the characteristic peak
in the temperature-dependent resistivity and the anomalous Hall effect. Here,
through employing a clean dry-transfer fabrication method under inert
environment, we successfully obtain high-quality ZrTe5 thin devices that
exhibit clear dual-gate tunability and ambipolar field effects. Such devices
allow us to systematically study the resistance peak as well as the Hall effect
at various doping densities and temperatures, revealing the contribution from
electron-hole asymmetry and multiple-carrier transport. By comparing with
theoretical calculations, we suggest a simplified semiclassical two-band model
to explain the experimental observations. Our work helps to resolve the
long-standing puzzles on ZrTe5 and could potentially pave the way for realizing
novel topological states in the two-dimensional limit. | 2305.09119v1 |
2023-05-26 | Room temperature quantum Hall effect in a gated ferroelectric-graphene heterostructure | The quantum Hall effect is widely used for the investigation of fundamental
phenomena, ranging from topological phases to composite fermions. In
particular, the discovery of a room temperature resistance quantum in graphene
is significant for compact resistance standards that can operate above
cryogenic temperatures. However, this requires large magnetic fields that are
accessible only in a few high magnetic field facilities. Here, we report on the
quantum Hall effect in graphene encapsulated by the ferroelectric insulator
CuInP2S6. Electrostatic gating of the graphene channel enables the Fermi energy
to be tuned so that electrons in the localized states of the insulator are in
equilibrium with the current-carrying, delocalized states of graphene. Due to
the presence of strongly bound states in this hybrid system, a quantum Hall
plateau can be achieved at room temperature in relatively modest magnetic
fields. This phenomenon offers the prospect for the controlled manipulation of
the quantum Hall effect at room temperature. | 2305.16825v1 |
2023-08-07 | Hall Coefficient and Resistivity in the Doped Bilayer Hubbard Model | Finding and understanding non-Fermi liquid transport behaviors are at the
core of condensed matter physics. Most of the existing studies were devoted to
the monolayer Hubbard model, which is the simplest model that captures
essential features of high-temperature superconductivity. Here we discover a
new type of non-Fermi liquid behavior emergent in the hole-doped bilayer
Hubbard model, using dynamical mean-field theory with a full consideration of
the short-range interlayer electron correlation. We find that at low
temperatures, the Hall coefficient has a strong nonmonotonic dependence on
temperature, leading to a double or quadruple reversal of its sign depending on
the doping level. At the same time, the resistivity exhibits two plateaus
rather than linearity in its temperature dependence. We show that these
intriguing transport behaviors stem from the formation of coherent interlayer
singlets, which scatter off gapped collective modes arising from short-range
interlayer antiferromagnetic fluctuations. | 2308.03862v1 |
2023-11-17 | Fate of the superconducting state in floating islands of hybrid nanowire devices | We investigate the impact of transport current on the superconducting order
parameter in superconducting islands in full-shell epitaxial Al-InAs nanowires.
Depending on a device layout, the suppression of superconductivity occurs in
three fundamentally different ways -- by a critical current in the case of
superconducting reservoirs and by a critical voltage or by a critical Joule
power in the case of normal reservoirs. In the latter case, the collapse of the
superconducting state depends on the ratio of the dwell time and the
electron-phonon relaxation time of quasiparticles in the island. For low
resistive and high resistive coupling to the reservoirs, respectively, the
relaxation-free regime and the strong electron-phonon relaxation regime are
realized. Our results shed light on potential shortcomings of finite-bias
transport spectroscopy in floating islands. | 2311.10676v2 |
2023-11-29 | Dynamic Programming Algorithms for Discovery of Antibiotic Resistance in Microbial Genomes | The translation of comparative genomics into clinical decision support tools
often depends on the quality of sequence alignments. However, currently used
methods of multiple sequence alignments suffer from significant biases and
problems with aligning diverged sequences. The objective of this study was to
develop and test a new multiple sequence alignment (MSA) algorithm suitable for
the high-throughput comparative analysis of different microbial genomes. This
algorithm employs an innovative tensor indexing method for partitioning the
dynamic programming hyper-cube space for parallel processing. We have used the
clinically relevant task of identifying regions that determine resistance to
antibiotics to test the new algorithm and to compare its performance with
existing MSA methods. The new method "mmDst" performed better than existing MSA
algorithms for more divergent sequences because it employs a simultaneous
alignment scoring recurrence, which effectively approximated the score for edge
missing cell scores that fall outside the scoring region. | 2311.17538v1 |
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