Mesoscale and Nanoscale Physics
Semiclassical theory of frequency dependent linear magneto-optical transport in Weyl semimetals
Azaz Ahmad, Pankaj Bhalla, Snehasish Nandy et al. (+1 more)
We develop a semiclassical Boltzmann theory for frequency-dependent magneto-optical transport in Weyl semimetals (WSMs), incorporating momentum-dependent relaxation via a scattering
matrix approach. The interplay of orbital
magnetic moment, Weyl cone tilt, intervalley scattering, and electromagnetic driving is analyzed to obtain the full conductivity tensor in the presence of a static
magnetic field. For untilted WSMs with orbital
magnetic moment, strong intervalley scattering in the weak ac regime induces a sign reversal of the longitudinal magneto-optical conductivity (LMOC), thereby suppressing the
chiral anomaly. In contrast, in the strong ac regime, intervalley scattering fails to neutralize the
chiral imbalance within a driving cycle, and no sign reversal is observed. Orbital
magnetic moment induces linear
magnetic-field contributions, while
chiral anomaly yields quadratic response accompanied by expected angular profiles. Tilt direction and orientation strongly affect LMOC such as, transverse tilt gives symmetric non-monotonic behavior, whereas parallel tilt leads to asymmetric, nearly monotonic response. Notably, negative LMOC arises intrinsically for parallel tilt, but requires orbital
magnetic moment for transverse tilt. These results highlight frequency-dependent conductivity as a sensitive probe of
chiral relaxation in MHz-THz magneto-optical experiments.
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All authors Azaz Ahmad, Pankaj Bhalla, Snehasish Nandy, Tanay Nag
Mesoscale and Nanoscale Physics
Electron localization, charge redistribution, and emergence of topological states at graphite junctions
Luke Soneji, Simon Crampin and Marcin Mucha-Kruczynski
Low-energy electronic behavior in graphite
crystals is highly dependent on the relative stacking arrangement of the constituent layers. Topologically non-trivial electronic states can arise due to interrupted rhombohedral (ABC) stacking, localized at the edges of the stacking region, but not in the case of Bernal (AB) stacking. Here, we study the electronic properties of junctions between half-
crystals of graphite of either Bernal or rhombohedral stacking, using a charge self-consistent tight-binding method and
embedding potentials to account for the influence of layers far from the junction. We find junction-localized electronic states to be a ubiquitous feature, and all systems but one involving a rhombohedral half-
crystal support a flat-band expected to exhibit electronic instabilities and strongly-correlated states. Nascent flat-band states associated with finite rhombohedral stacking sequences extend the physics into pure Bernal systems.
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Strongly Correlated Electrons
Machine-learning modeling of magnetization dynamics in quasi-equilibrium and driven metallic spin systems
Gia-Wei Chern, Yunhao Fan, Sheng Zhang et al. (+1 more)
We review recent advances in machine-learning (ML) force-field methods for large-scale Landau-Lifshitz-Gilbert (LLG) simulations of metallic
spin systems. We generalize the Behler-Parrinello (BP) ML architecture – originally developed for
quantum molecular dynamics – to construct scalable and transferable ML models capable of capturing the intricate dependence of electron-mediated exchange fields on the local
magnetic environment characteristic of itinerant magnets. A central ingredient of this framework is the implementation of
symmetry-aware
magnetic descriptors based on group-theoretical bispectrum formalisms. Leveraging these ML force fields, LLG simulations faithfully reproduce hallmark non-collinear
magnetic orders – such as the $120^\circ$ and tetrahedral states – on the triangular
lattice, and successfully capture the complex
spin textures emerging in the mixed-phase states of a square-
lattice double-exchange model under thermal quench. We further discuss a generalized potential theory that extends the BP formalism to incorporate both conservative and nonconservative electronic torques, thereby enabling ML models to learn nonequilibrium exchange fields from computationally demanding microscopic approaches such as nonequilibrium Green's-function techniques. This extension yields quantitatively accurate predictions of voltage-driven domain-wall motion and establishes a foundation for
quantum-accurate, multiscale modeling of nonequilibrium
spin dynamics and spintronic functionalities.
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All authors Gia-Wei Chern, Yunhao Fan, Sheng Zhang, Puhan Zhang
Soft Condensed Matter
Machine Learning-Enabled Mechanical Analysis and Optimization of Bioinspired Functionally Graded Materials
Zhangke Yang and Zhaoxu Meng
Tendon-bone enthesis connects tendon and bone, two mechanically dissimilar materials, while effectively minimizing stress concentrations, a capability rarely achieved in engineering materials. Its hierarchical organization and graded variations in composition or mineralization are widely recognized as key contributors to its exceptional performance. Here, we investigate the mechanics of enthesis, focusing on the insertion of interface collagen fibers into bone where hierarchical collagen fibril structures and graded mineralization are present, and translate these insights into bioinspired engineering material design using a convolutional neural network-based field predictor (CNNFP). We first construct a three-dimensional finite element model (FEM) of the interface fiber-bone enthesis, in which local material properties depend on mineralization level, mean fibril orientation, and angular dispersion, informed by a multiscale continuum theory. We introduce a scalar risk factor that integrates local stress states and constituent fibril organizations to quantify local vulnerability. Simulation results demonstrate that graded and spatially heterogeneous configurations markedly reduce stress concentrations, supporting prevailing biomechanical hypotheses. We then train the CNNFP as an accurate surrogate for FEM and embed it within a kernel-based gradient optimization framework to efficiently identify optimal field configurations. The optimized designs are validated against FEM ground truth, establishing a generalizable AI-enabled pathway for the optimization of bioinspired functionally graded materials.
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Statistical Mechanics
Inverse engineering of cooling protocols: from normal behavior to Mpemba effects
Hartmut Löwen
When a cup of hot coffee is suddenly put into a cold environment, it cools down as a function of time $t$ until the internal temperature $T_\text{int}$ of the coffee equals the external ambient temperature $T_\text{ext}$. This instantaneous shock-freezing corresponds to an imposed cooling protocol of the external temperature $T_\text{ext}(t)$, ideally described as a step-function in time, causing the time-dependent change of the internal temperature $T_\text{int}(t)$. While the effect of different given protocols $T_\text{ext}(t)$ on the resulting system cooling behaviour,
embodied in $T_\text{int}(t)$, has been studied extensively, we consider here the inverse question: for a given system cooling $T_\text{int}(t)$ how can an appropriate protocol $T_\text{ext}(t)$ be engineered to produce the desired prescribed $T_\text{int}(t)$. We use both the phenomenological Newtonian equation for cooling and microscopic models, such as a discrete two-level system and a Brownian harmonic oscillator with time-dependent noise, to compute analytically the protocol $T_\text{ext}(t)$ needed to achieve a prescribed $T_\text{int}(t)$. We then discuss the same question for phenomenological generalizations of the Newtonian law which include anomalous Mpemba effects, overcooling, asymmetries in cooling and heating as well as delay phenomena. It is shown that backward-engineered protocols do not always exist and can be non-unique. The results are important for steering the cooling behavior by time-varying external heat sources in a systematic way.
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Disordered Systems and Neural Networks
Nexus-CAT: A Computational Framework to Define Long-Range Structural Descriptors in Glassy Materials from Percolation Theory
Julien Perradin, Simona Ispas, Anwar Hasmy et al. (+1 more)
Nexus-CAT (Cluster Analysis Toolkit) is an open-source Python package for cluster detection and percolation analysis of atomistic simulation trajectories. Standard structural tools, such as the pair distribution function or structure factor, fail to capture the long-range connectivity changes underlying amorphous-amorphous transitions in glassy materials. Nexus-CAT addresses this gap by reading extended XYZ trajectory files and identifying clusters via a Union-Find
algorithm with path-compression. Four clustering strategies, i.e., distance-based, bonding, coordination-filtered, and shared-neighbor, are implemented through a Strategy Factory design pattern, enabling the treatment of diverse network
topologies. The program computes key percolation properties with percolation detection based on a rigorous period vector
algorithm. The package is validated against theoretical predictions and applied to glasses with different bonding environments, namely vitreous silica, vitreous ice, and amorphous silicon. One original result is the observation of a percolation transition prior to crystallization in the latter, indicating that pressure-induced crystallization is initially driven by an amorphous transformation with similar coordination number. The code is also designed to be readily extended to gels, cements, and other disordered materials. Nexus-CAT is fully available on GitHub and PyPI.
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All authors Julien Perradin, Simona Ispas, Anwar Hasmy, Bernard Hehlen
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Noise-Induced Resurrection of Dynamical Skin Effects in Quasiperiodic Non-Hermitian Systems
Wuping Yang and H. Huang
The non-Hermitian skin effect (NHSE) refers to the accumulation of an extensive number of eigenstates at system boundaries under open boundary conditions (OBCs). As a dynamical consequence, wave packets in such systems drift and ultimately accumulate at a boundary, giving rise to the dynamical skin effect (DSE). While strong quasiperiodic potentials are known to suppress the DSE by inducing localization, we show that the introduction of Ornstein-Uhlenbeck (OU) noise unexpectedly restores it. Using perturbative analysis, we demonstrate that noise effectively maps the non-Hermitian Schrödinger dynamics onto a non-reciprocal master equation, whose complex spectrum develops a noise-induced point gap. This mechanism enables delocalization, reinstates directional transport, and revives the DSE even in regimes where the static NHSE is absent. Moreover, the relaxation dynamics exhibit a non-monotonic dependence on noise strength, reflecting a competition between noise-assisted delocalization and noise-induced decoherence. Our results uncover a noise-enabled mechanism for resurrecting the DSE and suggest a new route for controlling transport in quasiperiodic, open
quantum systems.
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Mesoscale and Nanoscale Physics
Giant Domain-Wall Hall Magnetoresistance in Magnetic Topological Semimetal
Jinying Yang, Qingqi Zeng, Yibo Wang et al. (+7 more)
Magnetic topological semimetals exhibit emerging magneto-transport behaviors, such as the
giant anomalous
Hall effect (AHE),
chiral Hall effect, and antisymmetric magnetoresistance. In this work, based on the
magnetic Weyl semimetal Co3Sn2S2, we report an intriguing longitudinal domain-wall
Hall magnetoresistance in multi-domain states. According to a multi-domain model, a concise formula of this
Hall magnetoresistance was revealed and verified experimentally. Rather than the real change of longitudinal resistance, this
Hall magnetoresistance originates from an additional electric field distribution induced by the transverse
giant AHE through the domain wall, which can be directly correlated to the Berry phase of topological Weyl bands. In Co3Sn2S2 devices, the
Hall magnetoresistance was an order of magnitude larger than that of conventional
magnetic materials, indicating its potential for multi-resistance-state modulation via the Weyl-enhanced AHE.
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All authors Jinying Yang, Qingqi Zeng, Yibo Wang, Meng Lyu, Yang Liu, Xingchen Liu, Xuebin Dong, Binbin Wang, Xiyang Li, Enke Liu
Statistical Mechanics
Optimization of cooling power of a thermoelectric refrigerator: A unified approach
Rajeshree Chakraborty and Ramandeep S. Johal
We analyze the steady-state formalism for optimizing the cooling power of a thermoelectric refrigerator (TER), unifying the endoreversible and exoreversible approximations within one framework. Although the cooling power is non-optimizable within the endoreversible model based on Newtonian heat-transfer law, we show that the issue can be circumvented in the near-reversible regime where the external thermal conductances are large, but finite. We extend this analysis to optimize the cooling power in the presence of both internal and external irreversibilities and derive a closed-form expression for the coefficient of performance (COP) that depends on the thermoelectric figure of merit and the ratio of internal to external thermal conductances. The model reproduces the endoreversible and the exoreversible limits as special cases. We conclude that for small temperature differences, the combined irreversibilities reduce the COP to values below 1/2, which aligns with the observed performance of the single-stage TER, and can provide realistic estimates for the COP.
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Materials Science
Field-driven triggering of self-induced Floquet magnons in a magnetic vortex
R. Lopes Seeger, G. Philippe, A. Jenkins et al. (+5 more)
We report the experimental control of Floquet
magnons in a
magnetic vortex. Using microwave spectroscopy of
vortex state
magnetic tunnel junctions (MTJs), we find that self-induced Floquet sidebands form frequency combs whose existence depend on the
vortex core orbit. By shifting the
vortex core with an applied
magnetic field, we switch the system between regular and Floquet
magnons at identical drive conditions, demonstrating hysteretic control of the Floquet spectrum. A nonlinear
vortex-
magnon model shows that this behavior originates from multiple stable
vortex gyration radii created by Floquet-mediated feedback. These results establish
magnetic state initialization as a means to switch between regular and Floquet
magnons.
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All authors R. Lopes Seeger, G. Philippe, A. Jenkins, L. C. Benetti, A. Schulman, R. Ferreira, J.-V. Kim, T. Devolder
Materials Science
Investigating nucleation-driven phase transitions in neopentyl molecular crystals using infrared thermography and polarised light microscopy
Frederic Rendell-Bhatti, Vinzent G. Hana, Csongor Joba et al. (+2 more)
Sustainable solid-state refrigerants based on barocaloric materials are often limited by thermal hysteresis associated with supercooling effects. Here, we present imaging methods to investigate and compare thermal behaviour and transition kinetics of the barocaloric molecular
crystal neopentyl glycol (NPG) with those of a lightly doped derivative, NPG$_{0.99}$PE$_{0.01}$, which incorporates 1 mol % pentaerythritol (PE). We use temperature-dependent polarised light (PL) microscopy and infrared (IR) thermography to correlate phase transition kinetics and local heat-flow with the bulk thermodynamic response obtained from calorimetry. We show that the doped system exhibits reduced supercooling and thermal hysteresis, attributed to increased microstructural disorder and an increase in the number of nucleation events. These findings provide insight into the design of low-hysteresis barocaloric materials for high-efficiency solid-state cooling applications.
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All authors Frederic Rendell-Bhatti, Vinzent G. Hana, Csongor Joba, David Boldrin, Donald A. MacLaren
Statistical Mechanics
Exact criteria for ground-state overlap dominance and dynamical quantum phase transitions
Taisanul Haque
It was recently conjectured and verified for the transverse-field Ising model [Phys. Rev. B 113, 165102 (2026)] that, after a sudden quench within the same
equilibrium phase, the initial ground state has its largest overlap with the final ground state. We show that this phase-based criterion is generally false, even in translationally invariant free-
fermion systems. For
Hamiltonians that factorize into independent $2\times 2$ momentum sectors, we derive the exact necessary-and-sufficient condition for ground-state overlap dominance: the initial and final sector Bloch vectors must have positive dot product for every momentum. This result proves the
conjecture in classes where same-phase quenches enforce this
geometric condition, but gives explicit same-phase counterexamples in Kitaev chains, where excited final eigenstates can dominate the overlap distribution. We further show that the same obstruction controls real-time Fisher-zero crossings, allowing dynamical
quantum phase transitions without crossing an
equilibrium phase boundary.
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Materials Science
Revealing Dislocation Interactions Controlling Mechanical Properties of Metals
Felix Frankus, Sina Borgi, Albert Zelenika et al. (+4 more)
During plastic deformation, metals change shape while continuously becoming stronger. The microscopic origin of these processes lies in the proliferation and movement of line defects, dislocations, and the subsequent self-organisation and pinning of dislocations on
lattice imperfections, including other dislocations. The nature of these multiscale processes has remained elusive because in situ observations have not been feasible. We present 3D movies of how dislocations pile up near an obstacle, deeply within a mm-sized pure Al sample and during tensile deformation. Cross-slip is found to provide a mechanism for the dislocations to escape the pile-up, leading to pronounced intermittent behaviour. Such data support a new generation of dislocation dynamics and micro-mechanics modelling.
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All authors Felix Frankus, Sina Borgi, Albert Zelenika, Basit Ali, Raquel Rodriguez-Lamas, Henning Friis Poulsen, Grethe Winther
Statistical Mechanics
Absence of thermalization after a local quench and strong violation of the eigenstate thermalization hypothesis
Peter Reimann and Christian Eidecker-Dunkel
Absence of thermalization after a global
quantum quench is a well-established numerical observation in integrable many-body systems, and can be empirically related to a violation of the eigenstate thermalization hypothesis (ETH) in such models. Still, in many of those examples a weaker version of the conventional ETH (wETH) has been numerically reported or even rigorously proven. In this paper we show analytically and illustrate numerically that the absence of thermalization is already possible after a local quench. A closely related finding is a strong violation of the ETH, meaning that not even the wETH is fulfilled anymore. In our analytical explorations we focus on XX-
spin-chain models with open boundary conditions, where the local quench is generated by initiating the system in thermal
equilibrium and then suddenly switching on (or slightly changing) a single-
spin impurity either at the end or in the center of the chain. Numerically we observe qualitatively similar phenomena also for more general XXZ-models in the case of an end-
impurity, but not in the case of a central
impurity.
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Materials Science
Ru Alloying in Ni/Al Reactive Multilayers: Experimental Observations and Molecular Dynamics Simulations
Nensi Toncich, Ankit Yadav, Jan Fikar et al. (+1 more)
Reactive multilayer thin films, a class of energetic materials, are increasingly recognized for their potential in joining applications, utilizing the chemical energy released as heat during exothermic reactions. These materials hold also promise for additional diverse technological applications, which require precise control over heat release rates and reaction propagation velocities. The microstructural properties of reactive multilayers play a critical role in determining their chemical reaction behavior. Among these, Ni/Al reactive multilayers have been extensively studied and used due to their favorable characteristics. In this study, we explore the incorporation of ruthenium (Ru) as a co-alloying element with nickel (Ni) in the Ni/Al system to investigate its impact on the materials properties, with a particular focus on reaction velocity and temperature. Ru enhances the reaction rates, but also causes a composition dependent phase transition in the as-deposited state from fcc to hcp. Additionally, molecular dynamics simulations are employed to examine the effects of Ru co-alloying with Ni, providing deeper insights into the underlying mechanisms. This work aims to advance the understanding of Ru's role in influencing the performance of Al/Ni-based reactive multilayers for advanced applications.
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All authors Nensi Toncich, Ankit Yadav, Jan Fikar, Ralph Spolenak
Mesoscale and Nanoscale Physics
Strain-Induced Curvature in Monolayer Graphene: Effects on Electronic Structure, Phonon Dynamics, and Lattice Thermal Conductivity
M. C. Santos, E. Lora da Silva, D. S. Baptista et al. (+6 more)
We present a comprehensive set of calculations to investigate the effect of strain-induced x-y topological perturbation in the monolayer
graphene sheet. We show that the induced
curvature with the defined strain constraint, energetically stabilizes the systems. The electronic properties are modified when the amplitude of the
curvature of the sheet increases, which induces Van Hove singularities of the electronic Density of States to approach the
Fermi energy. The highly curved system exhibits coexisting flat and linear dispersions close to the
Fermi level, which is a promising feature for thermoelectric applications. We also demonstrate, through the
phonon dispersion curves, that respective systems are dynamically stable within the studied range of strains/
curvatures. Moreover, the flexural acoustic mode transitions from quadratic to linear dispersion under strain, mimicking the 3D behavior and enhancing
phonon scattering. The increase of
phonon scattering will therefore decrease the value of the
lattice thermal conductivity, $\kappa_L$. Such results allows us to conclude that it is possible to tune $\kappa_L$ by applying x-y strain to the monolayer sheet, and inducing different topological
curvatures.
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All authors M. C. Santos, E. Lora da Silva, D. S. Baptista, T. Santos, M. Molinari, F. J. Manjón, Yin Cui, Xidong Lin, Tao Yang
Mesoscale and Nanoscale Physics
Ultrafast ghost Hall states in a 2d altermagnet
Ruikai Wu, Deepika Gill, Sangeeta Sharma et al. (+1 more)
Two-dimensional materials that exhibit optically active
spin and valley degrees of freedom represent one of the most fascinating – and potentially most technologically useful – platforms for the ultrafast interaction of light and matter. Here we show, via the example of Cr$_2$SO, that two dimensional altermagnets host valley states controllable by femtosecond
laser light: linearly polarized light pulses excite charge at one of two inequivalent valleys, with which valley charge is excited at determined by the polarization vector direction. This underpins a rich
spin and valley physics including: (i) valleytronics $-$ the generation of nearly 100$\%$
spin polarized valley currents, as well as (ii) a "ghost
Hall" effect $-$ the ultrafast creation of states in which
spin and charge currents are orthogonal without invoking
Hall physics. Our findings establish 2d altermagents as a platform providing a new route for the control of
spin- and charge currents at ultrafast times.
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All authors Ruikai Wu, Deepika Gill, Sangeeta Sharma, Sam Shallcross
Materials Science · Cross-listed from physics.app-ph
ALD W-Doped SnO$_2$ TFTs for Indium-Free BEOL Electronics
Mansi Anil Patil, Devarshi Dhoble, Shivaram Kubakaddi et al. (+4 more)
This work reports back-end-of-line (BEOL) compatible, thin-film transistors (TFTs) with sub-10 nm tungsten-doped tin
oxide (TWO) channels deposited by atomic layer deposition (ALD) at 150 $^\circ$C. TFTs with undoped SnO$_{\mathrm{x}}$, undoped WO$_{\mathrm{x}}$, and W-doped SnO$_{\mathrm{x}}$ channels with W concentrations of 5% and 10% were investigated. TFT with 10% W doping exhibited the best electrostatic control and overall device performance. Post-fabrication O$_{\mathrm{2}}$ annealing at 300 $^\circ$C for 5 minutes significantly enhanced device characteristics, reducing the subthreshold swing (SS) by nearly 2$\times$, increasing the I$_{\mathrm{on}}$/I$_{\mathrm{off}}$ ratio from $10^7$ to $10^9$, decreasing hysteresis by nearly 3$\times$ and positive bias stress-induced threshold shift by over 2$\times$ to a low value of 93 mV at a stress field of 4 MV/cm. Kinetic Monte Carlo simulations using Ginestra$^{\mathrm{TM}}$ support the experimental observations and attribute the bias instability to charge trapping in the gate dielectric and at the interface. This work demonstrates low-temperature ALD-grown TWO TFTs as a promising indium-free platform for BEOL and monolithic 3D integration.
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All authors Mansi Anil Patil, Devarshi Dhoble, Shivaram Kubakaddi, Mamta Raturi, Marco A Villena, Gaurav Thareja, Saurabh Lodha
Mesoscale and Nanoscale Physics
Enhancement of topological magnon-driven spin currents through local edge strain in CrI$_3$ nanoribbons
David Sanz Ruiz and David Soriano
This work describes topological
magnon transport in zigzag CrI$_3$ nanoribbons (ZNR) in presence of edge strain. Exchange coupling terms under strain are obtained from first-principles calculations, and the topological properties are introduced via second-neighbor Dzyaloshinskii-Moriya interactions. The
magnon Hamiltonian is calculated using linear
spin-wave theory and the Holstein-Primakoff transformation. Then, we use non-
equilibrium Green's function method to calculate the
spin-wave-generated currents in ribbons with different edge strain. Our calculations show the formation of strongly localized edge topological
magnons within the gap for DMI values slightly higher than the ones reported experimentally and in the presence of a tensile edge strain of the order of 3%. The
magnon-mediated topological
spin transport calculations shows an increase of the
spin current and characteristic decay length in tensile-strained CrI$_3$ nanoribbons compared with unstrained ones. Our findings demonstrate that straintronics provides a powerful route to harness and control topological
magnons in two-dimensional
magnetic materials.
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Materials Science
A new helical InSeI polymorph: crystal structure and polarized Raman spectroscopy study
Lucía Olano-Vegas, Davide Spirito, Evgeny Modin et al. (+7 more)
Tetragonal InSeI is an interesting low-dimensional metal chalcohalide due to its composition and anisotropic
crystal structure composed of helical chains, which give rise to optoelectronic properties with potential application in photodetectors, optical thermometers, and spintronic devices. However, experimental works lack on the study of its anisotropic or
chiral behavior. Here we present the
crystal structure of an unreported InSeI polymorph and study its
lattice dynamics in bulk
crystals and exfoliated nanowires by polarized Raman spectroscopy for two non-equivalent crystallographic planes. We determine the orientation of the helical chains and distinguish between crystallographic planes by linearly polarized measurements, evaluating the angle-dependent intensity of the modes, which allows assigning each mode to its representation. Circularly polarized Raman measurements do not reveal
chiral phonons, despite the helical chains and anisotropic
crystal structure. These results offer insight into the
crystal structure of InSeI, which is fundamental for the fabrication of orientation-dependent optoelectronic and spintronic devices.
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All authors Lucía Olano-Vegas, Davide Spirito, Evgeny Modin, Pavlo Solokha, Sergio Marras, Marco Gobbi, Fèlix Casanova, Serena De Negri, Luis E. Hueso, Beatriz Martín-García
Mesoscale and Nanoscale Physics
Multiplexed cryo-CMOS control of an isolated double quantum dot
Mathieu Darnas, Mathilde Ouvrier-Buffet, Antoine Faurie et al. (+12 more)
Scalable
spin-based
quantum computing demands precise and stable control of a large number of gate-defined
quantum dots while minimizing wiring complexity and thermal load. Control architectures based on sample-and-hold (SH) multiplexing techniques offer a promising solution by enabling sequential programming of several gate voltages using a limited number of input lines. However, the compatibility of such dynamic voltage refreshing with the stringent stability, noise, and speed requirements of
quantum dot operation is an active subject of study. Here we experimentally demonstrate that a multiplexing cryo-CMOS
circuit can reliably bias a silicon double
quantum dot (DQD) at 0.5K. Exploiting the isolated regime, we show deterministic loading and isolation of four electrons and stable access to all five charge configurations from (4,0) to (0,4), despite the sequential voltage refreshing. We further demonstrate rapid voltage pulsing across an inter-dot transition, resolving single-electron tunneling events and
stochastic switching at the (1,3)-(0,4) transition. These results confirm that SH-based multiplexed control is compatible with both static biasing and pulsing of isolated
quantum dots, representing an important milestone toward scalable cryogenic control architectures for large-scale
spin-
qubit processors.
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All authors Mathieu Darnas, Mathilde Ouvrier-Buffet, Antoine Faurie, Jean-Baptiste Casanova, Benoit Bertrand, Candice Thomas, Jean Charbonnier, Jean-Philippe Michel, Bruna Cardoso Paz, Yvain Thonnart, Franck Badets, Franck Balestro, Matias Urdampilleta, Tristan Meunier, Baptiste Jadot
Strongly Correlated Electrons
Magnetic Order of Dresselhaus-type Antiferromagnet EuIr$_4$In$_2$Ge$_4$ Studied by Single Crystal Neutron Diffraction
Chihiro Tabata, Koji Kaneko, Akiko Nakao et al. (+3 more)
The
magnetic order of EuIr$_4$In$_2$Ge$_4$, which crystallizes in a Dresselhaus-type noncentrosymmetric tetragonal structure, was investigated using two complementary single-
crystal neutron diffraction approaches. Time-of-flight single-
crystal diffraction reveals
antiferromagnetic Bragg reflections with propagation vector $q = (1, 0, 0)$ below the Néel temperature $T_{\rm N}$ = 2.5 K, indicating a breaking of body-centered translational
symmetry. Polarized
neutron diffraction on a triple-axis spectrometer demonstrates that the ordered Eu$^{2+}$ $4f$ moments lie within the basal plane and form a collinear
antiferromagnetic structure with antiparallel
alignment between corner and body-center sites. Despite the Dresselhaus-type
spin splitting in the conduction bands, the
magnetic order remains simple, implying weak coupling between localized moments and itinerant electrons.
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All authors Chihiro Tabata, Koji Kaneko, Akiko Nakao, Takashi Ohhara, Tatsuma D. Matsuda, Yoshichika Ōnuki
Materials Science
Surface correlation functions of dead-leaves models
Cedric J. Gommes
The pore-surface and surface-surface correlation functions are structural characteristics that play an important role in theoretical materials science and in small-angle scattering theory. Exact analytical expressions for the surface correlation functions are available only for very few models, and we here derive such expressions for the general class of dead-leaves models. Within these models, a two-phase pore/solid structure is created by sequentially and randomly filling space with pore-like or solid-like grains that overlap any pre-existing structure, in the same way as dead leaves fall on the ground. The obtained mathematical expressions are valid for any grain shape, in arbitrary dimension. The results are illustrated with monodispersed spherical grains,as well as with a dead-leaves realization of a Debye random medium. In the latter case, the size distribution of the grains is designed to produce a structure having exponential two-point correlation function. Compared to Debye random media obtained by numerical reconstruction, the dead-leaves structure has almost identical surface-surface correlation function, but distinctly different pore-surface correlation function. As a byproduct of our analysis, we also submit a general expression for the pore-surface and surface-surface correlation functions of the Boolean model, valid for arbitrary grains.
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Soft Condensed Matter
Suspensions of non-Brownian rods: droplet pinch-off, onset of heterogeneity and effective extensional viscosity
Virgile Thiévenaz, Nathan Vani and Alban Sauret
The stretching and pinch-off of a
liquid bridge is a simple way to probe when a suspension of particles stops behaving as a continuum. In this study, we consider density-matched suspensions of rigid nylon fibers with aspect ratios (length over diameter) ranging from 2 to 84, and volume fractions $\phi$ spanning the dilute to dense regimes. High-speed imaging of pendant-drop breakup reveals three successive regimes, as previously observed for spherical particles: an equivalent-fluid regime at early times, a dislocation regime corresponding to the separation of the rods, and a final regime controlled by the interstitial
liquid once the neck is devoid of rods. The thresholds between these regimes follow the previously proposed scaling for spherical particles, in which the rod length, rather than the rod diameter, is used as the relevant discrete scale. In the equivalent-fluid regime, pinch-off also leads to an effective extensional viscosity that increases with both volume fraction and aspect ratio. This viscosity is not equal to the shear viscosity measured in a parallel-plate rheometer, but both sets of data are well described by Mills' law using a critical volume fraction $\phi_c$. Finally, the critical volume fraction $\phi_c$ decreases monotonically with the aspect ratio and is well captured by an empirical law. These results show that pinch-off is a sensitive probe of continuum breakdown in anisotropic suspensions and that, for rigid rods, the rod length controls the onset of heterogeneous thinning.
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Materials Science
Density Functional Theory Study of Lanthanide Monoxides under High Pressure: Pressure-Induced B1-B2 Transition
Sergio Ferrari and Daniel Errandonea
Using density functional theory, we study the influence of hydrostatic pressure on the
crystal structure of lanthanide monoxides, focusing on the monoxides formed by the fifteen elements of the lanthanide series, from La to Lu. Calculations are performed using two methods for the ambient pressure B1 (NaCl type) structure, the general gradient approximation (GGA) and the local density approximation (LDA). Through a systematic comparison with existent experimental data, we find that the first method agrees better with the experiments. In addition, considering other cubic structures previously reported for lanthanide monoxides, as B2 (CsCl type) and B3 (ZnS type), we explore the possibility of the occurrence of pressure-induced phase transitions. Based on the better accuracy of GGA to describe the B1 phase at ambient conditions, we exclusively use GGA for the high pressure study. We find, for the fifteen studied compounds, that, at ambient pressure, the B1 structure is the one with the lowest enthalpy, being therefore the most thermodynamically stable structure. We also determine that, at elevated pressures, all the studied compounds undergo a structural phase transition to the B2 phase. We finally establish the relationship between pressure and volume of the unit
cell, along with the associated isothermal equation of state, determining the bulk modulus.
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Materials Science
High-Pressure Structural Evolution of Na2ZrSi2O7 and Na2ZrSi2O7.H2O: Topology-Driven Compression Behaviors, Phase Stability, and Electronic Transitions
Peijie Zhang, Pablo Botella, Neha Bura et al. (+6 more)
Silicate frameworks exhibit diverse structural responses under extreme conditions, which are strongly influenced by hydration. Here, we present a comparative high-pressure synchrotron X-ray diffraction study of Na2ZrSi2O7 and its hydrated analogue Na2ZrSi2O7.H2O up to 30 GPa, combined with electronic structure calculations. At ambient conditions, both phases share the same primary building units (PBUs: [ZrO6] and [SiO4]) but differ in secondary building units (SBUs, M2T4 vs. M2T6). Under compression, Na2ZrSi2O7 undergoes a phase transition near 15 GPa, while the hydrated phase remains stable throughout the pressure range. The anhydrous compound exhibits a higher bulk modulus (B0 = 77.1 GPa) and less anisotropic compression compared with the hydrated phase (B0 = 66.3 GPa). Distinct deformation mechanisms are observed: the anhydrous framework accommodates pressure through [ZrO6] octahedral distortion, whereas the hydrated framework compresses via [Si2O7] group tilting. Electronic structure calculations indicate band gap widening with pressure in both phases; notably, Na2ZrSi2O7 shows a direct-to-indirect band gap transition, whereas the hydrated phase retains a direct gap. These results reveal how hydration-driven topological modifications at the secondary building unit scale dictate the pressure-induced structural
evolution, phase stability, and electronic properties of zirconosilicate frameworks.
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All authors Peijie Zhang, Pablo Botella, Neha Bura, Xiao Dong, Catalin Popescu, Yellampalli Raghavendra, Rakesh Shukla, Srungarpu Nagabhusan Achary, Daniel Errandonea
Statistical Mechanics
Sluggish quantum mechanics of noninteracting fermions with spatially varying effective mass
Giuseppe Del Vecchio Del Vecchio, Manas Kulkarni, Satya N. Majumdar et al. (+1 more)
We analyze a class of one-dimensional
quantum systems characterized by a position-dependent kinetic term arising as the continuum limit of an inhomogeneous tight-binding model with spatially varying hopping amplitudes. In this limit, the Schrodinger equation takes the so-called BenDaniel-Duke form with an effective mass, scaling as $m_{eff}(x) = m_{eff}|x|^{\alpha}$ with $\alpha > 0$, leading to a framework we term sluggish
quantum mechanics, where particle motion is progressively suppressed at larger distances. Both without any external potential and with $V_{ext}(x)=\frac{1}{2}m_{eff}\omega^2 |x|^{\alpha+2}$, we obtain the eigenfunctions and the
quantum propagators exactly. We then investigate the problem of $N$ noninteracting spinless
fermions in the trap, determining the many-body ground-state wavefunction and the joint probability density function of the positions of the $N$
fermions. We show that the many-body
quantum probability density in the ground state forms a determinantal point process whose correlation kernel can be computed for any $N$, giving access to the average density as well as higher order correlation functions for any finite $N$. Moreover, we analyze the scaling form of this kernel in the large $N$ limit in the bulk, near the edge, and close to the origin. Our results show that the scaled average density profile for large $N$ has a finite support symmetric with respect to the origin, but has a non-monotonic shape with a vanishing minimum at the origin for any $\alpha>0$. One of the key findings of our work is that the scaled kernel near the origin $x=0$ for $\alpha>0$ is neither the Bessel nor the Airy kernel (that are standard for trapped
fermions), but is new, and is given by a sum of two Bessel kernels with different indices. Our results thus provide a framework relevant to engineered optical
lattices with position-dependent tunneling.
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All authors Giuseppe Del Vecchio Del Vecchio, Manas Kulkarni, Satya N. Majumdar, Sanjib Sabhapandit
Quantum Gases
Artificial-gauge-field-driven reentrant charge-density-wave phase in a three-leg Bose-Hubbard ladder
Takayuki Yokoyama and Yasuhiro Tada
We investigate hard-core
bosons at half filling on a three-leg ladder under the uniform artificial gauge field. By analyzing current patterns and correlation functions, we uncover a rich
quantum phase diagram containing multiple superfluid and insulating phases. In bosonic ladder systems, increasing the gauge flux typically destabilizes the Meissner phase and leads to
vortex phases characterized by circulating currents. In the present system, however, we find that charge-density-wave (CDW) phases emerge precisely in such a flux regime despite the presence of only an on-site interaction, where
vortex states are naturally expected and are indeed realized in nearby parameter regions. While part of this behavior can be qualitatively understood from a strong-coupling perspective, we also identify an isolated CDW region that cannot be connected to such limits. Furthermore, upon increasing the artificial gauge flux, we observe a reentrant sequence of
quantum phase transitions, CDW $\to$
vortex-superfluid $\to$ CDW, revealing a strong competition between the
vortex phase and the density-wave order.
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Statistical Mechanics
Tensor-Network Population Annealing
Takumi Oshima, Yuma Ichikawa and Koji Hukushima
We propose a hybrid sampling method, tensor-network population annealing (TNPA), which combines tensor-network (TN) initialization with population annealing (PA). We apply this method to the two-dimensional Edwards-Anderson Ising
spin glass. The approach is motivated by the limitations of existing methods: TN-based samplers can become numerically unstable in frustrated
spin systems at low temperatures, whereas conventional PA requires a long annealing schedule when started from the high-temperature limit. In TNPA, TN contractions are used only within a reliable temperature range to generate initial configurations that are close to the
equilibrium distribution. The subsequent low-temperature equilibration is then carried out by PA. To stabilize the initialization process, we introduce a diagnostic based on the effective sample size that adaptively selects the initialization temperature. The proposed framework provides a practical and physically motivated route to low-temperature sampling by combining the complementary strengths of TN and PA.
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Materials Science
Ladder-like Structural Architecture of Layered Magnetic $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs) Compounds by Self-flux Synthesis
Kai D. Röseler, Felix Eder and Fabian O. von Rohr
The discovery and control of intergrowth structures represent an important avenue for the targeted synthesis of new, more complex structure types. When including
magnetic framework metal atoms, this enhanced complexity can transfer to rich
magnetic ground states. Here, we show that the subtle adjustment of the composition of alkali-tellurium fluxes enables the synthesis of a new family of alkali chromium tellurides, $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs). Their ladder-like
crystal structures integrate the two-dimensional character of delafossite-like $A$CrTe$_2$ with the tunnel motifs of hollandite-like $A_{x}$Cr$_5$Te$_8$ phases. This results in a previously unobserved unique hybrid framework. Direction-dependent magnetization measurements on oriented single
crystals reveal distinct
magnetic ground states: Rb$_{2.4}$Cr$_8$Te$_{14}$ is
antiferromagnetic with $T_{\rm N}$ = 114.5 K, while Cs$_{2.4}$Cr$_8$Te$_{14}$ is ferrimagnetic with $T_{\rm C}$ = 125.0 K. This work underscores the simplicity and effectiveness of flux growth as a design strategy for discovering low-dimensional materials.
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