凝聚态物理学术速递[1.10]
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cond-mat凝聚态物理,共计47篇
【1】 DMRG and Monte Carlo studies of $\textrm{CrI}_3$ magnetic phases and the phase transition
标题:{CrI}_3磁相和相变的DMRG和Monte Carlo研究
链接:https://arxiv.org/abs/2201.02586
摘要:The monolayer of $\textrm{CrI}_3$ has been reported to exhibit the
ferromagnetic order, with a Curie temperature of $45 K$ and off-plane easy
axis, which has attracted much attention in the community of condensed matter
physics. Using the Density Matrix Renormalization Group method, we investigate
the role of correlation effects and using classical Monte Carlo simulations
analyze the nature of phase transitions in the XXZ Hamiltonian on a honeycomb
lattice, which can effectively model $\textrm{CrI}_3$. We show, that the
magnetic ordering of the Hamiltonian's ground state can be well approximated by
classical models in a wide range of an anisotropy parameter space. Using
classical Monte Carlo simulations we estimate the Curie temperature of $49.7 K$
which is in good agreement with experimental result.
【2】 Emergence of spinons in layered trimer iridate Ba4Ir3O10
标题:层状三聚铱酸钡Ba_4Ir_3O_(10)中自旋的出现
链接:https://arxiv.org/abs/2201.02567
备注:5 pages not including references or supplementary
摘要:Spinons are well-known as the elementary excitations of one-dimensional
antiferromagnetic chains, but means to realize spinons in higher dimensions is
the subject of intense research. Here, we use resonant x-ray scattering to
study the layered trimer iridate Ba4Ir3O10, which shows no magnetic order down
to 0.2 K. An emergent one-dimensional spinon continuum is observed that can be
well-described by XXZ spin-1/2 chains with magnetic exchange of ~55 meV and a
small Ising-like anisotropy. With 2% isovalent Sr doping, magnetic order
appears below TN=130 K along with sharper excitations, indicating that the
spinons become more confined in (Ba1-xSrx)4Ir3O10. We propose that the
frustrated intra-trimer interactions effectively reduce the system into
decoupled spin chains, the subtle balance of which can be easily tipped by
perturbations such as chemical doping. Our results put Ba4Ir3O10 between the
one-dimensional chain and two-dimensional quantum spin liquid scenarios,
illustrating a new way to suppress magnetic order and realize fractional
spinons.
【3】 Nature of novel moiré exciton states in WSe$_2$/WS$_2$ heterobilayers
标题:WSE$_2$/WS$_2$异质双层中新型Moiré激子态的性质
链接:https://arxiv.org/abs/2201.02562
摘要:Moir\'e patterns of transition metal dichalcogenide (TMD) heterobilayers have
proven to be an ideal platform to host unusual correlated electronic phases,
emerging magnetism, and correlated exciton physics. While the existence of
novel moir\'e excitonic states is established through optical measurements, the
microscopic nature of these states is still poorly understood, often relying on
empirically fit models. Here, combining large-scale first-principles GW-BSE
calculations and micro-reflection spectroscopy, we identify the nature of the
exciton resonances in WSe$_2$/WS$_2$ moir\'e superlattices, discovering a
surprisingly rich set of moir\'e excitons that cannot be even qualitatively
captured by prevailing continuum models. Our calculations reveal moir\'e
excitons with distinct characters, including modulated Wannier excitons and
previously unindentified intralayer charge-transfer excitons. Signatures of
these distinct excitonic characters are confirmed experimentally via the unique
carrier-density and magnetic-field dependences of different moir\'e exciton
resonances. Our study highlights the highly non-trivial exciton states that can
emerge in TMD moir\'e superlattices, and suggests novel ways of tuning
many-body physics in moir\'e systems by engineering excited-states with
specific spatial characters.
【4】 Nanoscale control of the metal-insulator transition at LAO/KTO (110) and LAO/KTO (111) interfaces
标题:LaO/KTO(110)和LaO/KTO(111)界面金属-绝缘体转变的纳米控制
链接:https://arxiv.org/abs/2201.02561
备注:19 pages, 9 figures
摘要:Recent reports of superconductivity at KTaO3 (KTO) (110) and (111) interfaces
have sparked intense interest due to the relatively high critical temperature
as well as other properties that distinguish this system from the more
extensively studied SrTiO3 (STO)-based heterostructures. Here we report
nanoscale control of the metal-to-insulator transition at the LaAlO3/KTO (110)
and (111) interfaces. Devices are created using two distinct methods previously
developed for STO-based heterostructures: (1) conductive atomic-force
microscopy lithography and (2) ultra-low-voltage electron-beam lithography. At
low temperatures, KTO-based devices show superconductivity that is tunable by
an applied back gate. A nanowire device shows single-electron-transistor (SET)
behavior. These reconfigurable methods of creating nanoscale devices in
KTO-based heterostructures offer new avenues for investigating mechanisms of
superconductivity as well as development of quantum devices that incorporate
strong spin-orbit interactions, superconducting behavior, and nanoscale
dimensions.
【5】 Origin of the large entropy change in the molecular caloric and ferroelectric ammonium sulfate
标题:分子热电硫酸铵大熵变的成因
链接:https://arxiv.org/abs/2201.02548
备注:13 pages, 5 figures
摘要:The deceptively simple inorganic salt ammonium sulfate undergoes a
ferroelectric phase transition associated with a very large entropy change and
both electrocaloric and barocaloric behaviour. While the structural origins of
the electrical polarisation are now well established, those of the entropy
change are more controversial. To resolve this question, we have performed
total (elastic), quasielastic, and inelastic neutron scattering, as functions
of both temperature and pressure, and DFT simulation. We show that a simple
model of the entropy, in which each molecular ion is disordered across the
mirror plane in the high symmetry phase, is untenable. Instead, the entropy
arises from large-amplitude, anharmonic librations in this phase. Our results
suggest that, in the search for molecular materials with large entropy changes,
vibrational entropy arising from broad, anharmonic energy minima is likely to
be just as important as configurational entropy arising from crystallographic
disorder.
【6】 Numerical Simulations of Pressure Induced $sp^2$-$sp^3$ Transitions in Defect Carbon Nanotubes
标题:缺陷碳纳米管中压力诱导的$sp^2$-$sp^3$相变的数值模拟
链接:https://arxiv.org/abs/2201.02544
备注:8 pages, 13 figures
摘要:The combination of pressure and vacancy defects are investigated to find the
ideal conditions that would create meaningful $sp^3$ interlinking without
causing severe damage to the single-walled carbon nanotubes (SWCNTs). Naturally
occurring defects fail to induce interlinking. The introduction of vacancy type
defects reduces the collapse pressure of the SWCNTs. The combination of vacancy
defects, high temperature and low pressure induces $sp^3$ without causing
severe damage to the nanotubes. Structural changes caused before and after
pressurization of the nanotubes were analyzed using Raman spectroscopy.
【7】 Frozen dynamics of a breather induced by an adiabatic invariant
标题:绝热不变量诱导的呼吸器冻结动力学
链接:https://arxiv.org/abs/2201.02529
备注:23 pages
摘要:The Discrete Nonlinear Schr\"odinger (DNLS) equation is a Hamiltonian model
displaying frozen dynamics when breathers appear in the system. We study
breather relaxation in the thermal region, $T < +\infty$, in a unidirectional
version of the DNLS equation, where the rest of the system does not feel the
breather. Breather dynamics is governed by a time-dependent one-dimensional
Hamiltonian with two distinct time scales, and we show that the stability of
the breather is related to the existence of an adiabatic invariant (AI).
Approximate expressions for the AI are obtained both by implementing a
canonical perturbation theory and a more phenomenological approach based on the
estimate of the energy flux. The close correspondence with the original model
allows excluding that breather destabilization is induced by the formation of
localized bound states such as dimers. Finally, the AI dynamics reveals an
unexpected similarity with Levy processes, which deserves further
investigations.
【8】 Residual stresses and shear-induced overaging in boehmite gels
标题:薄水铝石凝胶中的残余应力和剪切诱导的过时效
链接:https://arxiv.org/abs/2201.02528
备注:5 pages, 4 figures
摘要:Colloidal gels respond like soft solids at rest, whereas they flow like
liquids under external shear. Starting from a fluidized state under an applied
shear rate $\dot\gamma_{p}$, abrupt flow cessation triggers a liquid-to-solid
transition during which the stress relaxes towards a so-called \textit{residual
stress} $\sigma_{\rm res}$ that tallies a macroscopic signature of previous
shear history. Here, we report on the liquid-to-solid transition in gels of
boehmite, an aluminum oxide, that shows a remarkable non-monotonic stress
relaxation towards a residual stress $\sigma_{\rm res}(\dot\gamma_{p})$
characterized by a dual behavior relative to a critical value $\dot\gamma_{c}$
of the shear rate $\dot\gamma_{p}$. Following shear at
$\dot\gamma_{p}>\dot\gamma_{c}$, the gel obtained upon flow cessation is
insensitive to shear history, and the residual stress is negligible. However,
for $\dot\gamma_{p}<\dot\gamma_{c}$, the gel encodes some memory of the shear
history, and $\sigma_{\rm res}$ increases for decreasing shear rate, directly
contributing to reinforcing the gel viscoelastic properties. Moreover, we show
that both $\sigma_{\rm res}$ and the gel viscoelastic properties increase
logarithmically with the strain accumulated during the shear period preceding
flow cessation. Such a shear-induced "overaging" phenomenon bears great
potential for tuning the rheological properties of colloidal gels.
【9】 Photo-induced insulator-to-metal transition and coherent acoustic phonon propagation in LaCoO$_3$ thin films explored by femtosecond pump-probe ellipsometry
标题:飞秒泵浦探测椭圆偏振法研究LaCoO$_3薄膜中的光诱导绝缘体-金属转变和相干声学声子传播
链接:https://arxiv.org/abs/2201.02525
备注:8 pages, 4 figures
摘要:We have studied ultrafast dynamics of thin films of LaCoO$_3$ and
La$_{0.5}$Sr$_{0.5}$CoO$_3$ with femtosecond pump-probe ellipsometry in the
energy range of 1.6-3.4 eV. We have observed a large pump-induced transfer of
spectral weight in LaCoO$_3$ that corresponds to an insulator-to-metal
transition. The photo-induced metallic state initially relaxes via a fast
process with a decay constant of about 200 fs. Both LaCoO$_3$ and
La$_{0.5}$Sr$_{0.5}$CoO$_3$ exhibit a significant secondary transient structure
in the 1-30 ps range. Results of measurements on films with different
thicknesses demonstrate that it corresponds to a propagation of an acoustic
strain pulse. On timescales longer than 100 ps, heat diffusion to the substrate
takes place that can be modelled with a bi-exponential decay.
【10】 Scaling Theory for Wöhler plots in amorphous solids under cyclic forcing
标题:循环强迫下非晶态固体中Wöhler图的标度理论
链接:https://arxiv.org/abs/2201.02513
备注:arXiv admin note: substantial text overlap with arXiv:2103.03040
摘要:In mechanical engineering W\"ohler plots serve to measure the average number
of load cycles before materials break, as a function of the maximal stress in
each cycle. Although such plots are prevalent in engineering for more than 150
years, their theoretical understanding is lacking. Recently a scaling theory of
W\"ohler plots in the context of cyclic bending was offered [1]. Here we
elaborate further on cyclic bending and extend the considerations to cyclic
tensile loads on an amorphous strip of material; the scaling theory applies to
both types of cyclic loading equally well. On the basis of atomistic
simulations we conclude that the crucial quantities to focus on are the
accumulated damage and the average damage per cycle. The dependence of these
quantities on the loading determines the statistics of the number of cycles to
failure. Finally we consider the probability distribution functions of the
number of cycles to failure and demonstrate that the scaling theory allows
prediction of these distributions at one value of the forcing amplitude from
measurements and another value.
【11】 Anisotropic vortex squeezing in Rashba superconductors: a manifestation of Lifshitz invariants
标题:Rashba超导体中的各向异性涡旋压缩:Lifshitz不变量的一种表现
链接:https://arxiv.org/abs/2201.02512
备注:8 pages, 3 figures
摘要:Most of 2D superconductors are of type II, i.e., they are penetrated by
quantized vortices when exposed to out-of-plane magnetic fields. In presence of
a supercurrent, a Lorentz-like force acts on the vortices, leading to drift and
dissipation. The current-induced vortex motion is impeded by pinning at
defects, enabling the use of superconductors to generate high magnetic fields
without dissipation. Usually, the pinning strength decreases upon any type of
pair-breaking. Here we show that in Rashba superconductors the application of
an in-plane field leads, instead, to an unexpected enhancement of pinning. When
rotating the in-plane component of the field with respect to the current
direction, the vortex inductance turns out to be highly anisotropic. We explain
this phenomenon as a manifestation of Lifshitz invariant terms in the
Ginzburg-Landau free energy, which are enabled by inversion and time-reversal
symmetry breaking and lead to an elliptic squeezing of vortex cores. Our
experiment provides access to a fundamental property of Rashba superconductors
and offers an entirely new approach to vortex manipulation.
【12】 Nonlinear magnetotransport in Weyl semimetal
标题:Weyl半金属的非线性磁输运
链接:https://arxiv.org/abs/2201.02505
备注:10 pages, 1 figure
摘要:The recent discovery of the quantum nonlinear Hall effect has revived the
field of nonlinear transport. Here, we predict magnetic field-induced nonlinear
Hall effect in time-reversal symmetric Weyl semimetal. We show that the
interplay of the band geometric quantities, such as the Berry curvature, and
the magnetic part of the Lorentz force can give rise to finite nonlinear Hall
conductivity that is linear in the magnetic field. Such nonlinear Hall
conductivity can manifest through nonlinear transport measurement as well as
nonlinear optical phenomena like photocurrent and the second harmonic
generation.
【13】 Optimizing broad ion beam polishing of zircaloy-4 for electron backscatter diffraction analysis
标题:用于电子背散射衍射分析的锆-4合金宽离子束抛光工艺优化
链接:https://arxiv.org/abs/2201.02501
备注:as submitted
摘要:Microstructural analysis with electron backscatter diffraction (EBSD)
involves sectioning and polishing to create a flat and preparation-artifact
free surface. The quality of EBSD analysis is often dependant on this step, and
this motivates us to explore how broad ion beam (BIB) milling can be optimised
for the preparation of zircaloy-4 with different grain sizes. We systematically
explore the role of ion beam angle, ion beam voltage, polishing duration and
polishing temperature and how this changes the surface roughness and indexing
quality. Our results provide a method to routinely prepare high-quality
Zircaloy-4 surfaces, and methods to optimise BIB polishing of other materials
for high-quality EBSD studies.
【14】 Geometric thermodynamic uncertainty relation in periodically driven thermoelectric heat engine
标题:周期驱动热电热机的几何热力学不确定性关系
链接:https://arxiv.org/abs/2201.02477
备注:11 pages, 6 figures
摘要:Thermodynamic uncertainty relation, quantifying a trade-off among average
current, the associated fluctuation (precision), and entropy production (cost),
has been formulated in nonequilibrium steady state and various stochastic
systems. Herein, we study the thermodynamic uncertainty relation in generic
thermoelectric heat engines under a periodic control protocol, by uncovering
the underlying Berry-phase-like contribution. We show that our thermodynamic
uncertainty relation breaks the seminal steady-state results, originating from
the non-vanishing geometric effect. Furthermore, by deriving the consequent
trade-off relation binding efficiency, power, and constancy, we prove that the
periodically driven thermoelectric heat engines can generally outperform the
steady-state analogies. The general bounds are illustrated by an analytically
solvable two-terminal single quantum dot heat engine under the periodic
modulation. Our work provides a geometric framework in bounding and optimizing
a wide range of periodically driven thermoelectric thermal machines.
【15】 Dynamic control of octahedral rotation in perovskites by defect engineering
标题:基于缺陷工程的钙钛矿八面体旋转动态控制
链接:https://arxiv.org/abs/2201.02476
摘要:Engineering oxygen octahedra rotation patterns in ABO$_3$ perovskites is a
powerful route to design functional materials. Here we propose a new strategy
that exploits point defects that create local electric dipoles and couple to
the oxygen sublattice, enabling direct actuation on the rotational degrees of
freedom. This approach, which relies on substituting an A site with a smaller
ion, paves a way to couple dynamically octahedra rotations to external electric
fields. A common antisite defect, $\mathrm{Al_{La}}$ in rhombohedral LaAlO$_3$
is taken as a prototype to validate the idea, with atomistic DFT calculations
supported with an effective lattice model to simulate the dynamics of switching
of the local rotational degrees of freedom to long distances. Our simulations
provide an insight of the main parameters that govern the operation of the
proposed mechanism, and allow to define guidelines for screening other systems
where this approach could be used for tuning the properties of the host
material.
【16】 Octahedral tilting in Prussian blue analogues
标题:普鲁士蓝类似物的八面体倾斜
链接:https://arxiv.org/abs/2201.02467
摘要:Octahedral tilting is key to the structure and functionality of perovskites.
Here we show how these distortions manifest in the related Prussian blue
analogues (PBAs): cyanide versions of double perovskites with formula
A$_x$M[M$^{\prime}$(CN)$_6$]$_{1-y}\Box _y\cdot n$H$_2$O (A = alkali metal, M
and M$^{\prime}$ = transition metals, $\Box$ = vacancy/defect). Tilts are
favoured by high values of $x$ if A = Na or K, whereas the transition metals
play a less important role. External hydrostatic pressure can induce tilt
transitions nearly irrespective of the stoichiometry, whereas thermal
transitions are only reported for $x>1$. Interstitial water can alter the
transitions induced by a different stimulus, but (de)hydration \textit{per se}
does not lead to tilts. Implications for rational design of critical
functionality -- including improper ferroelectricity and electrochemical
performance -- are discussed. The results are important for a fundamental
understanding of phase transitions as well as for the development of functional
materials based on PBAs.
【17】 Position-dependent memory kernel in generalized Langevin equations: theory and numerical estimation
标题:广义Langevin方程的位置相关记忆核:理论和数值估计
链接:https://arxiv.org/abs/2201.02457
备注:16 pages, 3 figures
摘要:Generalized Langevin equations with non-linear forces and position-dependent
linear friction memory kernels, such as commonly used to describe the effective
dynamics of coarse-grained variables in molecular dynamics, are rigorously
derived within the Mori-Zwanzig formalism. The derivation also yields
Volterra-type equations for the kernel, which can be used for a numerical
parametrization of the model from all-atom simulations.
【18】 Emergence of zero modes in disordered solids under periodic tiling
标题:周期瓦片作用下无序固体中零模的出现
链接:https://arxiv.org/abs/2201.02456
摘要:In computational models of particle packings with periodic boundary
conditions, it is assumed that the packing is attached to exact copies of
itself in all possible directions. The periodicity of the boundary then
requires that all of the particles' images move together. An infinitely
repeated structure, on the other hand, does not necessarily have this
constraint. As a consequence, a jammed packing (or a rigid elastic network)
under periodic boundary conditions may have a corresponding infinitely repeated
lattice representation that is not rigid or indeed may not even be at a local
energy minimum. In this manuscript, we prove this claim and discuss ways in
which periodic boundary conditions succeed to capture the physics of repeated
structures and where they fall short.
【19】 Mobile impurity probing a two-dimensional superfluid phase transition
标题:二维超流相变的流动杂质探测
链接:https://arxiv.org/abs/2201.02453
摘要:We explore the properties of a quasiparticle formed by a mobile impurity
interacting with a two-dimensional fermionic superfluid. We demonstrate that
the discontinuous nature of the superfluid to normal phase transition leads to
a jump in the quasiparticle energy at the critical temperature. The jump
exhibits a non-monotonic behavior as a function of the pairing strength. Since
the jump is measurable with present experimental techniques, our results
illustrate how mobile impurities entangled with their environment can serve as
useful probes for non-trivial thermal and quantum correlations.
【20】 Theory of shift heat current and its application to electron-phonon coupled systems
标题:移位热流理论及其在电声耦合系统中的应用
链接:https://arxiv.org/abs/2201.02431
备注:11 pages, 5 figures
摘要:We propose a heat current analog of the shift current, ``shift heat
current''. We study nonlinear heat current responses to an applied ac electric
field by a diagrammatic method and derive a microscopic expression for the
second order dc heat current response. As a result, we find that the shift heat
current is related to the shift vector, a geometric quantity that also appears
in the expression for the shift current. The shift heat current directly
depends on and can be controlled through the chemical potential. In addition,
we apply the diagrammatic method to electron-phonon coupled systems, and we
find that even if only the phonons are excited by an external field, the
amplitude of the shift heat current is determined by the energy scale of
electrons, not of phonons.
【21】 Density depletion and enhanced fluctuations in water near hydrophobic solutes: identifying the underlying physics
标题:疏水溶质附近水的密度耗尽和增强的波动:识别潜在的物理
链接:https://arxiv.org/abs/2201.02427
备注:5 pages, 4 figures. To appear in Phys. Rev. Lett
摘要:We investigate the origin of the density depletion and enhanced density
fluctuations that occur in water in the vicinity of an extended hydrophobic
solute. We argue that both phenomena are remnants of the critical drying
surface phase transition that occurs at liquid-vapor coexistence in the
macroscopic planar limit, ie. as the solute radius $R_s\to\infty$. Focusing on
the density profile $\rho(r)$ and a sensitive spatial measure of fluctuations,
the local compressibility profile $\chi(r)$, we develop a scaling theory which
expresses the extent of the density depletion and enhancement in
compressibility in terms of $R_s$, the strength of solute-water attraction
$\varepsilon_s$, and the deviation from liquid-vapor coexistence $\delta\mu$.
Testing the predictions against results of classical density functional theory
for a simple solvent and Grand Canonical Monte Carlo simulations of a popular
water model, we find that the theory provides a firm physical basis for
understanding how water behaves at a hydrophobe.
【22】 First-principles study on the solute-induced low diffusion and self-trapping of helium in fcc iron
标题:溶质诱导面心立方铁中氦低扩散和自陷的第一性原理研究
链接:https://arxiv.org/abs/2201.02423
摘要:The addition of alloying elements plays an essential role in helium (He)
behaviours produced by transmutation in metal alloys. Effects of solutes (Ni,
Cr, Ti, P, Si, C) on the behaviours of He and He-He pair in face-centred cube
(fcc) iron have been investigated using first-principles calculations based on
density functional theory (DFT). For the interactions of solutes and He, we
found that Ti, P, Si, and C attracts He is more potent than Ni and Cr in fcc
iron. We have determined the most stable configuration for the He-He pair,
which is the Hesub-Hetetra pair with a binding energy of 1.60 eV. In
considering the effect of solutes on the stability of the He-He pair, we have
proposed a unique definition of binding energy. By applying the definition, we
suggest that Ti and P could weaken He self-trapping, and Cr and C are
beneficial for He self-trapping, while Ni is similar to the matrix Fe itself.
For the diffusion of He, which is the necessary process of forming the He
bubble, we determined that the most stable interstitial He is in a tetrahedral
site and could migrate with the energy barrier of 0.16 eV in pure fcc iron. We
further found that Ti and Si can increase the barrier to 0.18 and 0.20 eV; on
the contrary, Cr and P decrease the barrier to 0.10 and 0.06 eV, respectively.
Summarizing the calculations, we conclude that Ti decreases while Cr increases
the diffusion and self-trapping of He in fcc iron.
【23】 Simulation of nonequilibrium spin dynamics in quantum dots subjected to periodic laser pulses
标题:周期激光脉冲作用下量子点中非平衡自旋动力学的模拟
链接:https://arxiv.org/abs/2201.02421
备注:None
摘要:Large-scale simulations of the spin dynamics in quantum dots subjected to
trains of periodic laser pulses enable us to describe and understand related
experiments. By comparing the data for different models to experimental
results, we gain an improved understanding of the relevant physical mechanisms.
Using sophisticated numerical approaches and an efficient implementation
combined with extrapolation arguments, nonequilibrium stationary states are
reached for parameter ranges close to the ones in real experiments. With the
help of high performance computing, we can tune the experimental parameters to
guide future experimental research. Importantly, our simulations reveal the
possibility of resonant spin amplification in Faraday geometry, i.e., when a
longitudinal magnetic field is applied to the quantum dots.
【24】 Graphene Electron Metasurfaces
标题:石墨烯电子超表面
链接:https://arxiv.org/abs/2201.02415
摘要:The propagation effect is so far the only available implementation mechanism
when electronic components in graphene are developed based on Dirac fermion
optics. The resulting optics-inspired components are large in size and operate
normally only in the lowest possible temperature environment so that the
ballistic limits are not violated. Here electron metasurfaces based on the
generalized Snell's law, a linear array of gate-bias-controlled circular
quantum dots in form, are proposed to manipulate graphene electrons within the
distance of the quantum-dot diameter, far less than the ballistic limits at
room temperature. This provides opportunities to create untracompact
optics-inspired components which are comparable in size to components arising
from other principles and hence can operate at any temperature below room
temperature. Moreover, unlike their optical counterparts, electron metasurfaces
have near-perfect operation efficiencies and their high tunability allows for
free and fast switching among functionalities. The conceptually new
metasurfaces open up a promising avenue to pull optics-inspired components to a
desired level of performance and flexibility.
【25】 Tailoring Quadrupole Topological Insulators with Periodic Driving and Disorder
标题:周期驱动无序裁剪四极拓扑绝缘子
链接:https://arxiv.org/abs/2201.02414
备注:6 pages, 3 figures
摘要:The quadrupole topological insulator (QTI) has attracted intense studies as a
prototype of symmetry-protected higher-order topological phases of matter with
a quantized quadrupole moment. The realization of QTIs has been reported in
various static settings with periodic structures. Here, we theoretically
investigate topological phase transitions and establish the QTI phase in a
periodically driven system with disorder. In the clean limit, the Floquet QTI
phase merges from a topologically trivial band structure driven by elliptically
polarized irradiation. More strikingly, starting from a pure static system with
trivial topology, we unveil an intriguing QTI phase which necessitates the
simultaneous presence of disorder and periodic driving. Furthermore, we reveal
that particle-hole symmetry is sufficient to protect the QTI. Our work not only
establishes a new strategy to design QTIs but also enrich the
symmetry-protected mechanism of higher-order topology.
【26】 Deformation mechanism of WC single crystals under nanoindentation: Effects of surface defects and orientation on pop-in and hysteresis
标题:WC单晶纳米压痕变形机制:表面缺陷和取向对突入和滞后的影响
链接:https://arxiv.org/abs/2201.02411
备注:21 pages, 7 figures
摘要:Nanoindentation was carried out on pure tungsten carbide (WC) on the basal
(0001) and prismatic (1010) planes, using Berkovich and spherical indenters, in
both single load and multi-load testing. The work focuses on correlating the
load-displacement curves, including elastic to plastic deformation, size effect
and hysteresis with the deformation behaviour of WC. With different specimen
preparation processes, the elastic to plastic deformation started at different
threshold loads: This observation was found to be due to the variation in
surface dislocation density. Staircase deformation was observed thought to be
caused by dislocation motion and the formation of slip bands; sudden
displacement discontinuities in the load-displacement response - associated
with dislocation loop nucleation - occurred at, or near the theoretical shear
strength. Furthermore, discontinuities in load-displacement curves were also
used to confirm that hysteresis loops were a result of plastic deformation, as
they when the loading was purely elastic.
【27】 Malleable patterns from the evaporation of colloidal liquid bridge: coffee ring to the scallop shell
标题:胶体液桥蒸发的延展性模式:咖啡环到扇贝壳
链接:https://arxiv.org/abs/2201.02382
摘要:The present article highlights an approach to generate contrasting patterns
from drying droplets in a liquid bridge configuration, different from
well-known coffee rings. Reduction of the confinement distance (the gap between
the solid surfaces) leads to systematized nano-particle agglomeration yielding
to spokes-like patterns similar to those found on scallop shells instead of
circumferential edge deposition. Alteration of the confinement length modulates
the curvature that entails variations in the evaporation flux across the
liquid-vapor interface. Consequently, flow inside different liquid bridges
(LBs) varies significantly for different confinement lengths. Small confinement
lengths result in the stick-slip motion of squeezed liquid bridges. On the
contrary, the stretched LBs exhibit pinned contact lines. We decipher a
proposition that a drying liquid thin film present during dewetting near the
three-phase contact line is responsible for the aligned deposition of
particles. The confinement distance determines the height of this thin film,
and its theoretical estimations are validated against the experimental
observations using reflection interferometry, further exhibiting good agreement
(in order of magnitude). Modulating the particle size does not significantly
influence the precipitate patterns; however, particle concentration can
substantially affect the deposition patterns. The differences in deposition
patterns are attributed to the complex interplay of the gradient of evaporation
flux induced motion of contact line in combination with the drying of thin
liquid film during dewetting.
【28】 Strongly interacting trapped one-dimensional quantum gases: an exact solution
标题:强相互作用囚禁一维量子气体的精确解
链接:https://arxiv.org/abs/2201.02362
备注:22 pages, 19 figures
摘要:Quantum correlations can be used as a resource for quantum computing, eg for
quantum state manipulation, and for quantum sensing, eg for creating
non-classical states which allow to achieve the quantum advantage regime. This
review collects the predictions coming from a family of exact solutions which
allows to describe the many-body wavefunction of strongly correlated quantum
fluids confined by a tight waveguide and subjected to any form of longitudinal
confinement. It directly describes the experiments with trapped ultracold atoms
where the strongly correlated regime in one dimension has been achieved. The
exact solution applies to bosons, fermions and mixtures. It allows to obtain
experimental observables such as the density profiles and momentum distribution
at all momentum scales, beyond the Luttinger liquid approach. It also predicts
the exact quantum dynamics at all the times, including the small oscillations
regime yielding the collective modes of the system and the large quench regime
where the system parameters are changed considerably. The solution can be
extended to describe finite-temperature conditions, spin and magnetization
effects. The review illustrates the idea of the solution, presents the key
theoretical achievements and the main experiments on strongly correlated
one-dimensional quantum gases.
【29】 Pressure driven topological phase transition in chalcopyrite ZnGeSb$_2$
标题:黄铜矿ZnGeSb$2$压力驱动拓扑相变
链接:https://arxiv.org/abs/2201.02347
摘要:Recently topologically non-trivial phases have been identified in few
time-reversal invariant systems that lack of inversion symmetry. Using density
functional theory based first-principles calculations, we report a strong
topologically non-trivial phase in chalchopyrite ZnGeSb$_2$, which can act as a
model system of strained HgTe. The calculations reveal the non-zero topological
invariant ($Z_2$), the presence of Dirac cone crossing in the surface spectral
functions with spin-momentum locking. We also show that the application of
moderate hydrostatic pressure ($\sim$7 GPa) induces topological phase
transition from topological non-trivial phase to a topologically trivial phase.
A discontinuity in the tetragonal distortion of non-centrosymmetric ZnGeSb$_2$
plays a crucial role in driving this topological phase transition.
【30】 First-principles study on phase stability and physical properties of B-site ordered Nd$_{2}$FeCrO$_{6}$ double perovskite
标题:B位有序Nd${2}$FeCrO${6}$双钙钛矿相稳定性和物理性质的第一性原理研究
链接:https://arxiv.org/abs/2201.02341
备注:None
摘要:Here, the first-principles predictions on the structural stability, magnetic
behavior and electronic structure of B-site ordered double perovskite
Nd$_{2}$FeCrO$_{6}$ have been reported. Initially, the ground state of the
parent single perovskites NdCrO$_{3}$ and NdFeO$_{3}$ have been studied to
determine the relevant Hubbard U parameter to investigate the properties of
Nd2CrFeO6. The thermodynamic, mechanical, and dynamic stability analyses
suggest the possibility of the synthesis of Nd$_{2}$FeCrO$_{6}$ double
perovskite at ambient pressure. The compound shows ferrimagnetic (FiM) nature
with 2 $\mu$B net magnetic moments and the magnetic ordering temperature has
been estimated to be $\sim$265 K. Electronic structure indicates higher
probability of direct photon transition over the indirect transition with a
bandgap of $\sim$1.85 eV. Additional effect of Nd (4f) spin and spin-orbit
coupling (SOC) on the band edges have been found to be negligible for this
4f-3d-3d spin system. This first-principles investigation predicts that due to
the ferrimagnetic nature and significantly lower bandgap compared to its
antiferromagnetic parent single perovskites, B-site ordered Nd$_{2}$FeCrO$_{6}$
double perovskite could be a promising material for spintronic and
visible-light-driven energy applications.
【31】 Roles of liquid structural ordering in glass transition, crystallization, and water's anomalies
标题:液体结构有序化在玻璃化转变、结晶和水异常中的作用
链接:https://arxiv.org/abs/2201.02334
备注:None
摘要:The liquid state is one of the fundamental and essential states of matter,
but its physical understanding is far behind the other states, such as the gas
and solid states, due to the difficulties associated with the high density
causing many-body correlations and the lack of long-range order. Significant
open problems in liquid science include glass transition, crystallization, and
water's anomalies. Austen Angell has contributed tremendously to these problems
and proposed many new concepts of fundamental importance. In this article, we
review how these concepts have influenced our work on liquid physics, focusing
on the roles of liquid structural ordering in glass transition,
crystallization, and water's anomalies.
【32】 Multiple skyrmion crystal phases by itinerant frustration in centrosymmetric tetragonal magnets
标题:中心对称四方磁体中巡游受挫产生的多个Skrmion晶相
链接:https://arxiv.org/abs/2201.02326
备注:6 pages, 4 figures
摘要:A skyrmion crystal (SkX) expressed as a multiple number of spiral modulations
manifests itself not only in its peculiar magnetic texture but also in
nontrivial transport properties originating from an emergent magnetic field. We
here report our numerical results for multiple SkXs in a centrosymmetric
tetragonal crystal system. By performing simulated annealing for an effective
spin model for itinerant magnets, we find that three types of the SkXs with the
skyrmion numbers of one and two, which are characterized by different
superpositions of helices, are stabilized in the ground state, and are
transformed by an external magnetic field. The essence of the emergent multiple
SkXs is lied in itinerant frustration where exchange interactions are competed
in momentum space due to the nature of itinerant electrons.
【33】 Temperature-Modulated Photomechanical Actuation of Photoactive Liquid Crystal Elastomers
标题:光活性液晶弹性体的温度调制光机械驱动
链接:https://arxiv.org/abs/2201.02324
备注:submitted revised manuscript
摘要:Photoactive liquid crystal elastomers are polymer networks of liquid crystal
mesogens embedded with chromophores like azobenzene. They undergo large
deformation when illuminated by light of a certain wavelength through
photochemical reaction, inspiring exciting new applications. However, despite
the recent progresses in both the experiment and theory of these materials, the
fundamental understanding of the temperature effect on their photomechanical
actuation through various molecular-to-mesoscale processes have remained
largely unexplored. This paper constructs a theoretical model to investigate
this temperature-modulated photomechanical actuation, by integrating different
temperature-dependent processes into a continuum framework. The model studies a
special working condition where the material is subjected to a uniaxial tensile
load, a prescribed temperature, and a polarized light illumination. We explore
the free energy landscape of the system and the uniaxial stress-stretch
responses under various conditions. We exploit the coupling between individual
controls of temperature and light in a single photomechanical actuation for
several working scenarios, including the temperature-modulated photomechanical
snap-through instability, specific work, and blocking stress. We study the
effect of the temperature-dependent backward isomerization of chromophores on
the photomechanical actuation. These results are hoped to motivate future
fundamental studies and new applications of various photomechanical material
systems.
【34】 Spin order and fluctuations in the EuAl$_4$ and EuGa$_4$ topological antiferromagnets: A $μ$SR study
标题:Eual$_4$和EuGa$_4$拓扑反铁磁体的自旋有序和涨落:$μ$SR研究
链接:https://arxiv.org/abs/2201.02294
备注:10 pages, 7 figures, accepted by Phys. Rev. B
摘要:We report on systematic muon-spin rotation and relaxation ($\mu$SR) studies
of the magnetic properties of EuAl$_4$ and EuGa$_4$ single crystals at a
microscopic level. Transverse-field $\mu$SR measurements, spanning a wide
temperature range (from 1.5 to 50 K), show clear bulk AFM transitions, with an
almost 100% magnetic volume fraction in both cases. Zero-field $\mu$SR
measurements, covering both the AFM and the paramagnetic (PM) states, reveal
internal magnetic fields $B_\mathrm{int}(0) = 0.33$ T and 0.89 T in EuAl$_4$
and EuGa$_4$, respectively. The transverse muon-spin relaxation rate
$\lambda_\mathrm{T}$, a measure of the internal field distribution at the
muon-stopping site, shows a contrasting behavior. In EuGa$_4$, it decreases
with lowering the temperature, reaching its minimum at zero temperature,
$\lambda_\mathrm{T}(0) = 0.71$ $\mu$s$^{-1}$. In EuAl$_4$, it increases
significantly below $T_\mathrm{N}$, to reach 58 $\mu$s$^{-1}$ at 1.5 K, most
likely reflecting the complex magnetic structure and the competing interactions
in the AFM state of EuAl$_4$. In both compounds, the temperature-dependent
longitudinal muon-spin relaxation $\lambda_\mathrm{L}(T)$, an indication of the
rate of spin fluctuations, diverges near the onset of AFM order, followed by a
significant drop at $T < T_\mathrm{N}$. In the AFM state, spin fluctuations are
much stronger in EuAl$_4$ than in EuGa$_4$, while being comparable in the PM
state. The evidence of robust spin fluctuations against the external magnetic
fields provided by $\mu$SR may offer new insights into the origin of the
topological Hall effect and the possible magnetic skyrmions in the EuAl$_4$ and
EuGa$_4$ compounds.
【35】 Formation of probability density waves and probability current density waves by excitation and decay of a doublet of quasistationary states of a three-barrier heterostructure upon scattering of gaussian wave packets
标题:高斯波包散射激发和衰减三屏障异质结双稳态形成概率密度波和概率流密度波
链接:https://arxiv.org/abs/2201.02288
备注:15 pages, 16 figures
摘要:A numerical-analytical simulation of scattering by a three-barrier
heterostructure of an electronic Gaussian wave packet, the spectral width of
which is on the order of the distance between the levels of the doublet of
quasi-stationary states, is carried out. It is shown that as a result of
scattering, damped waves of electron charge and current densities are formed
outside the double well, their characteristics are determined by the structure
of the initial wave packet and the poles of the scattering amplitudes. The
frequency of these waves is equal to the difference frequency of the doublet,
the wavenumber is the difference between the wave numbers of free motion of
electrons with resonant energies, and the speed of their propagation is the
ratio of these quantities. The system can go into the regime of repetition or
amplification of the emission of electron waves if a periodic resonant pumping
of the doublet population is provided by scattering of a series of coherent
wave packets.
【36】 Numerical studies for an ab initio investigation into the Boltzmann prescription in statistical mechanics of large systems
标题:大系统统计力学中玻耳兹曼公式从头计算的数值研究
链接:https://arxiv.org/abs/2201.02271
备注:13 pages, 4 figures
摘要:We present numerical investigations into the question of the validity of the
Boltzmann prescription in Statistical Mechanics for large systems, addressing
the issue of whether extensivity of energy implies the extensivity of the
Boltzmann entropy. The importance of the question stems from the fact that it
is currently considered open by some investigators but quite settled by others.
We report ab initio results for gas-like Hamiltonian systems with long-range as
well as short-range interactions, based on simulations that explicitly consider
more than $2^{30} \approx 10^9$ states of the full Hilbert space. The basis of
the technique is Monte Carlo algorithms. Despite the largeness of the numbers
used, careful inspection shows that the systems studied are still too small to
settle uniquely the issues raised. Therefore, the new approach outlined
represents a first step in addressing on first principles the question of
non-extensive statistical mechanics. General theoretical comments are also
supplied to supplement the numerical investigations.
【37】 ScS_{2} Monolayer as a Potential Cathode Material for Alkali-ion Batteries and Beyond
标题:SCS_{2}单分子膜作为潜在的碱性离子电池正极材料
链接:https://arxiv.org/abs/2201.02268
摘要:Sc is the lightest transition metal that could help to achieve the goal of
high theoretical capacity. Hence, we here explored the performance of ScS_{2}
monolayer as a cathode material for alkali-ion batteries (Li, Na, K) and other
multi-valent metal-ion batteries (Mg, Al). Previous studies on ScS_{2} have
focused only on the fundamental electronic and magnetic properties of the
ScS_{2} monolayer, but not on its possible applications. Our first-principles
calculations show that 2D ScS_{2} is able to deliver a large theoretical
capacity of 491.36 mAh g^{-1} for alkali-ions and 324.29 mAh g^{-1} for Mg and
Al-ions while maintaining good average open-circuit voltages. We also studied
the diffusivity of these metal ions on the ScS_{2} surface which is related to
the charge/discharge rate capability of batteries. Our results suggest low
diffusion barriers for all metal ions except Al. Owing to these results, we,
therefore, believe that the ScS_{2} monolayer can be an interesting candidate
for cathode material to be used in alkali-ion batteries and beyond.
【38】 Pseudogap in elemental plutonium
标题:元素钚中的假能隙
链接:https://arxiv.org/abs/2201.02255
备注:6 pages including 3 figure panels
摘要:Electronic correlations associated with incipient magnetism have long been
recognized as an important factor in stabilizing the largest atomic volume
$\delta$ phase of plutonium, yet their strength compared to those in the rare
earths and neighboring actinides in the Periodic Table has largely remained a
mystery. We show here using calorimetry measurements, together with prior
detailed measurements of the phonon dispersion, that the $5f$ electrons of the
$\delta$ phase reside in a pseudogapped state, accompanied by reductions in
various physical properties below a characteristic temperature
$T^\ast\approx$~100~K. The small characteristic energy scale of the
pseudogapped state implies that the $5f$ electrons in plutonium are much closer
to the threshold for localization and magnetic order than has been suggested by
state-of-the-art electronic structure theory, revealing plutonium to be
arguably the most strongly correlated of the elements.
【39】 Massless Dirac fermions on a space-time lattice with a topologically protected Dirac cone
标题:拓扑保护狄拉克锥时空格子上的无质量狄拉克费米子
链接:https://arxiv.org/abs/2201.02235
摘要:The symmetries that protect massless Dirac fermions from a gap opening may
become ineffective if the Dirac equation is discretized in space and time,
either because of scattering between multiple Dirac cones in the Brillouin zone
(fermion doubling) or because of singularities at zone boundaries. Here we
introduce an implementation of Dirac fermions on a space-time lattice that
removes both obstructions. The quasi-energy band structure has a single Dirac
cone which cannot be removed without breaking both time-reversal and chiral
symmetries. We show that this topological protection is absent in the familiar
split-operator discretization, because there the time-evolution operator is
discontinuous at Brillouin zone boundaries.
【40】 Transformation between elastic dipoles, quadrupoles, octupoles and hexadecapoles driven by surfactant self-assembly in nematic emulsion
标题:向列相乳状液中表面活性剂自组装驱动的弹性偶极、四极、八极和十六极间的相互转化
链接:https://arxiv.org/abs/2201.02234
摘要:Emulsions comprising isotropic fluid drops within a nematic host are of
interest for applications ranging from biodetection to smart windows, which
rely on changes of molecular alignment structures around the drops in response
to chemical, thermal, electric and other stimuli. We show that absorption or
desorption of trace amounts of common surfactants can drive continuous
transformations of elastic multipoles induced by the droplets within the
uniformly aligned nematic host. Out-of-equilibrium dynamics of director
structures emerge from a controlled self-assembly or desorption of different
surfactants at the drop-nematic interfaces, with ensuing forward and reverse
transformations between elastic dipoles, quadrupoles, octupoles and
hexadecapoles. We characterize inter-transformations of droplet-induced surface
and bulk defects, probe elastic pair interactions and discuss emergent
prospects for fundamental science and applications of the reconfigurable
nematic emulsions.
【41】 Loschmidt echo and Poincaré recurrences of entanglement
标题:Loschmidt回波与纠缠的Poincaré重现
链接:https://arxiv.org/abs/2201.02600
备注:28 pages, 20 figures and 4 pages with 4 figures Supplementary Material
摘要:We study numerically the properties of entanglement of two interacting, or
noninteracting, particles evolving in a regime of quantum chaos in the quantum
Chirikov standard map. Such pairs can be viewed as interacting, on
noninteracting, Einstein-Podolsky-Rosen pairs in a regime of quantum chaos. The
analysis is done with such tools as the Loschmidt echo of entanglement and the
Poincar\'e recurrences of entanglement in presence of absorption. The obtained
results show unusual features of the entropy of entanglement and the spectrum
of Schmidt decomposition with their dependence on interactions at different
quantum chaos regimes.
【42】 Variational quantum simulation of valence-bond solids
标题:价键固体的变分量子模拟
链接:https://arxiv.org/abs/2201.02545
摘要:We introduce a hybrid quantum-classical variational algorithm to simulate
ground-state phase diagrams of frustrated quantum spin models in the
thermodynamic limit. The method is based on a cluster-Gutzwiller ansatz where
the wave function of the cluster is provided by a parameterized quantum
circuit. The key ingredient is a tunable real XY gate allowing to generate
valence-bonds on nearest-neighbor qubits. Additional tunable single-qubit Z-
and two-qubit ZZ-rotation gates permit the description of magnetically ordered
phases while efficiently restricting the variational optimization to the U(1)
symmetric subspace. We benchmark the method against the paradigmatic J1-J2
Heisenberg model on the square lattice, for which the present hybrid ansatz is
an exact realization of the cluster-Gutzwiller with 4-qubit clusters. In
particular, we describe the Neel order and its continuous quantum phase
transition onto a valence-bond solid characterized by a periodic pattern of 2x2
strongly-correlated plaquettes, providing a route to synthetically realize
valence-bond solids with currently developed superconducting circuit devices.
【43】 Spatial data modeling by means of Gibbs Markov random fields based on a generalized planar rotator model
标题:基于广义平面旋转体模型的吉布斯马尔可夫随机场空间数据建模
链接:https://arxiv.org/abs/2201.02537
备注:29 pages, 9 figures
摘要:We introduce a Gibbs Markov random field for spatial data on Cartesian grids
which is based on the generalized planar rotator (GPR) model. The GPR model
generalizes the recently proposed modified planar rotator (MPR) model by
including in the Hamiltonian additional terms that better capture realistic
features of spatial data, such as smoothness, non-Gaussianity, and geometric
anisotropy. In particular, the GPR model includes up to infinite number of
higher-order harmonics with exponentially vanishing interaction strength,
directional dependence of the bilinear interaction term between nearest grid
neighbors, longer-distance neighbor interactions, and two types of an external
bias field. Hence, in contrast with the single-parameter MPR model, the GPR
model features five additional parameters: the number $n$ of higher-order terms
and the parameter $\alpha$ controlling their decay rate, the exchange
anisotropy parameter $J^{nn}$, the further-neighbor interaction coupling
$J^{fn}$, and the external field (bias) parameters $K$ (or $K'$). We present
numerical tests on various synthetic data which demonstrate the effects of the
respective terms on the model's prediction performance and we discuss these
results in connection with the data properties.
【44】 Projective Embedding of Dynamical Systems: uniform mean field equations
标题:动力系统的射影嵌入:一致平均场方程
链接:https://arxiv.org/abs/2201.02355
备注:45 pages; one column; 10 figures;
摘要:We study embeddings of continuous dynamical systems in larger dimensions via
projector operators. We call this technique PEDS, projective embedding of
dynamical systems, as the stable fixed point of the dynamics are recovered via
projection from the higher dimensional space. In this paper we provide a
general definition and prove that for a particular type of projector operator
of rank-1, the uniform mean field projector, the equations of motion become a
mean field approximation of the dynamical system. While in general the
embedding depends on a specified variable ordering, the same is not true for
the uniform mean field projector. In addition, we prove that the original
stable fixed points remain stable fixed points of the dynamics, saddle points
remain saddle, but unstable fixed points become saddles.
【45】 Precision Bootstrap for the $\mathcal{N}=1$ Super-Ising Model
链接:https://arxiv.org/abs/2201.02206
备注:32 pages, 6 figures
摘要:In this note we report an improved determination of the scaling dimensions
and OPE coefficients of the minimal supersymmetric extension of the 3d Ising
model using the conformal bootstrap. We also show how this data can be used as
input to the Lorentzian inversion formula, finding good agreement between
analytic calculations and numerical extremal spectra once mixing effects are
resolved.
【46】 Topological confinement in Skyrme holography
标题:Skyrme全息术中的拓扑约束
链接:https://arxiv.org/abs/2201.00105
备注:21 pages, 8 figures, new title, additional author
摘要:We study phase transitions in five-dimensional Einstein Gravity with a
negative cosmological constant, coupled to a Skyrme matter field. These
transitions are topological generalizations of the Hawking-Page transition
between thermal Anti de Sitter (AdS) spacetime and an AdS black hole. Phases
are characterized by a topological number associated with the Skyrme field
configuration. Depending on that topological number and on the Skyrme coupling
strength, there occur transitions between those phases at two, one, or no
value(s) of the temperature. Through the holographic (AdS/CFT) correspondence,
these solutions are dual to topologically non-trivial states in a conformal
field theory (CFT) with an SU(2)-symmetry, which support either confined or
deconfined (quasi-)particles at strong coupling. We compare to similar known
phase transitions, and discuss potential applications to confinement in
topological phases of condensed matter and the quark-gluon plasma.
【47】 Information flow, Gating, and Energetics in dimeric molecular motors
标题:二聚体分子马达中的信息流、门控和能量学
链接:https://arxiv.org/abs/2112.15088
摘要:Molecular motors belonging to the kinesin and myosin super family hydrolyze
ATP by cycling through a sequence of chemical states. These cytoplasmic motors
are dimers made up of two linked identical monomeric globular proteins. Fueled
by the free energy generated by ATP hydrolysis, the motors walk on polar tracks
(microtubule or filamentous actin) processively, which means that only one head
detaches and executes a mechanical step while the other stays bound to the
track. Thus, the one motor head must regulate chemical state of the other,
referred to as "gating", a concept that is not fully understood. Inspired by
experiments, showing that only a fraction of the energy from ATP hydrolysis is
used to advance the kinesin motors against load, we demonstrate that additional
energy is used for coordinating the chemical cycles of the two heads in the
dimer - a feature that characterizes gating. To this end, we develop a general
framework based on information theory and stochastic thermodynamics, and
establish that gating could be quantified in terms of information flow between
the motor heads. Applications of the theory to kinesin-1 and Myosin V show that
information flow occurs, with positive cooperativity, at external resistive
loads that are less than a critical value, $F_c$. When force exceeds $F_c$,
effective information flow ceases. Interestingly, $F_c$, which is independent
of the input energy generated through ATP hydrolysis, coincides with force at
which the probability of backward steps starts to increase. Our findings
suggest that transport efficiency is optimal only at forces less than $F_c$,
which implies that these motors must operate at low loads under $\textit{in
vivo}$ conditions.
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