Statistical Mechanics
Memory of topologically constrained disorder in Shakti artificial spin ice
Priyanka Priyanka, Cristiano Nisoli and Yair Shokef
Complex behaviors often sit at a critical threshold between order and disorder. But not all disorder is created equal. Disorder can be trivial or constrained, and correlated disorder can even be topological. Crucially, constrained disorder can harbor
memory, leading to non-trivial, sequence-dependent responses to external manipulations. And yet the fascinating subject of "
memory of disorder" remains poorly explored, as
memory is often associated to the retention of metastable order. In recent years artificial frustrated materials – in particular arrays of frustrated nanomagnets known as artificial
spin ices – have been employed to study complex disorders and its wealth of exotic behaviors, yet their
memory properties have received much less
attention. Here, we investigate both analytically and numerically the sequence-dependent responses of two somehow opposite yet related artificial
spin ices: the Landau-ordered square
spin ice and the disordered but topologically-ordered Shakti
spin ice. We find that Shakti exhibits a pronounced sequence-dependent response, whereas in the square
lattice, such path dependence is absent. Within Shakti, even the minimal periodic supercell demonstrates both deterministic and
stochastic forms of sequence
memory, depending on the interaction strength. Extending our study to cyclic driving, we find that retracing the same input path leads to enhanced
memory retention. These results open new perspectives on how topological constraints and correlated disorder generate robust
memory effects in frustrated artificial materials, hitherto examined mainly in terms of their ground-state kinetics and thermodynamics.
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Mesoscale and Nanoscale Physics
Oles Matsyshyn, Li-kun Shi and Inti Sodemann Villadiego
A periodically driven
Fermi gas coupled to a simple
boson bath reaches a non-
equilibrium steady-state occupation with sharp non-analyticities at certain momenta. Here, we demonstrate that these non-analyticities behave as emergent
Fermi surfaces by showing that they give rise to
quantum oscillations of observables with a period controlled by the effective
Fermi surface area enclosed by these non-analyticities. However, these oscillations have several striking differences with standard
equilibrium quantum oscillations. For example, they remain non-analytic at finite temperatures, their amplitude can survive up to extremely high temperatures comparable to the frequency of the drive, and they can display non-monotonic temperature dependence completely at odds with standard Lifshits-Kosevich behavior.
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Soft Condensed Matter
Upper bounds on the colloid separation efficiency of diffusiophoresis
Fernando Temprano-Coleto, Jeongmin Kim, Marcel M. Louis et al. (+1 more)
The separation of colloidal particles from fluids is essential to ensure a safe global supply of drinking water, yet in the case of microscopic particles, it remains a highly energy-intensive process when using traditional filtration methods. Water cleaning through diffusiophoresis, spontaneous colloid migration in chemical gradients, effectively circumvents the need for physical filters, representing a promising alternative. This separation process is typically realized in internal flows, where a cross-channel electrolyte gradient drives particle accumulation at walls, with colloid separation slowly increasing in the streamwise direction. However, the maximum separation efficiency, achieved sufficiently downstream as diffusiophoretic migration (driving particle accumulation) is balanced by Brownian motion (inducing diffusive spreading), has not yet been characterized. In this work, we develop an asymptotic theory to predict colloid separation in this limit, deriving expressions for the water recovery, defined as the fraction of clean water that can be obtained from the suspension. We find that the mechanism by which the chemical permeates in the channel and the reaction kinetics governing its dissociation into ions play key roles in the process. Moreover, we identify four distinct regimes in which separation is controlled by different scaling laws involving Damköhler and Péclet numbers, which measure the ratios of reaction kinetics to ion
diffusion and diffusiophoresis to Brownian motion, respectively. We also confirm the scaling of one of these regimes using microfluidic experiments where separation is driven by CO2 gradients. Our results shed light on pathways toward new, more efficient separations and are also applicable to quantify colloidal accumulation in the presence of chemical gradients in more general situations.
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All authors Fernando Temprano-Coleto, Jeongmin Kim, Marcel M. Louis, Howard A. Stone
Statistical Mechanics
On Critical Temperature and Finite Size Scaling of Continuous Spin $2d$ Ising Model
Swapna Mahapatra, Rudra Majhi, Jahangir Mohammed et al. (+3 more)
In this paper, we have studied the critical temperature $T_c$ of continuous
spin $2d$ square-
lattice Ising model using Monte-Carlo simulation. We have considered
spins $s$ in a bounded interval, where $s \in [-1,+1]$ in square-
lattice configuration with periodic boundary condition. We have observed that the critical temperature $T_c$ is approximately $0.925$, showing a clear second order phase transition. Considering finite size scaling, we have also obtained the critical exponents associated with susceptibility, specific heat, magnetization and we find that these values are in good agreement with the corresponding values obtained for the standard $2d$ Ising universality class.
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All authors Swapna Mahapatra, Rudra Majhi, Jahangir Mohammed, Subhashree Mohanty, Priyanka Priyadarshini Pruseth, Masoom Singh
Materials Science
Concentration-Dependent Tungsten Effects on Chemical Short-Range Order and Deformation Behavior in Ni-W alloys
Shaozun Liu, Zehao Li, Hantong Chen et al. (+8 more)
Ni-W based medium heavy
alloys offer a promising pathway to bridge the density-strength gap between tungsten heavy
alloys and ultrahigh-strength steels. In this study, the effects of W concentration on chemical short-range order (CSRO), deformation behavior, and grain boundary chemistry of Ni-xW
alloys in the range x = 0 to 38 wt% were systematically investigated using a suite of advanced characterization and modeling techniques, including synchrotron X-ray diffraction, transmission electron microscopy, atom probe
tomography, and first-principles thermodynamic simulations. Our study reveals that strong CSRO emerges when W content exceeds about 30 wt%, producing distinct diffuse scattering and significantly enhancing strain-hardening capacity. During deformation, the presence of SRO promotes planar slip and twin formation, leading to strong dislocation interactions and elevated flow stress.
Hall-Petch analysis demonstrates an exceptionally high grain boundary strengthening coefficient (ky about 1100 MPa micrometer^(1/2)) in Ni-38W, underscoring the intrinsic strengthening effect associated with CSRO. First-principles cluster expansion coupled with Monte Carlo simulations reveals that increasing W content enhances SRO tendency through the stabilization of Ni4W-type local configurations. These findings establish a mechanistic link between W concentration, CSRO
evolution, and mechanical response, providing new insights for designing high-density, high-strength Ni-W based
alloys with optimized performance.
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All authors Shaozun Liu, Zehao Li, Hantong Chen, Xingyuan San, Bi-Cheng Zhou, Dieter Isheim, Tiejun Wang, Nie Zhao, Yu Liu, Yong Gan, Xiaobing Hu
Quantum Gases
Bethe-ansatz study of the Bose-Fermi mixture
Soham Chandak, Aleksandra Petković and Zoran Ristivojevic
We consider a one-dimensional mixture of
bosons and spinless
fermions with contact interactions. In this system, the elementary excitations at low energies are described by four linearly dispersing modes characterized by two excitation velocities. Here we study the velocities in a system with equal interaction strengths and equal masses of
bosons and
fermions. The resulting model is integrable and admits an exact Bethe-ansatz solution. We analyze it and analytically derive various exact results, which include the Drude weight
matrix. We show that the excitation velocities can be calculated from the knowledge of the
matrices of compressibility and the Drude weights, as their squares are the
eigenvalues of the product of the two
matrices. The elements of the Drude weight
matrix obey certain sum rules as a consequence of Galilean invariance. Our results are consistent with the presence of a momentum-momentum coupling term between the two subsystems of
bosons and
fermions in the effective low-energy
Hamiltonian. The analytical method developed in the present study can be extended to other models that possess a nested Bethe-ansatz structure.
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Mesoscale and Nanoscale Physics
Non-Hermitian topological devices with Chern insulators
Kyrylo Ochkan, Michael Wissmann, Louis Veyrat et al. (+9 more)
Multi-terminal topological devices are a new generation of electronic devices with quantized properties robust against imperfections. In
magnetic topological
insulators, dissipationless edge states give functional devices in zero
magnetic field, of interest for
quantum metrology (resistance standard) or topological electronics (Chern networks). Here we show that a new generation of simple
quantum circuits (disk, ring) with non-Hermitian
topology, based on the interconnection of 1D Chern states in the
quantum anomalous
Hall regime, can have a much stronger quantization of their invariant than that of the Chern invariant itself, when measured in a non-metrology grade setup - that is, in industry-relevant conditions. Remarkably, the chirality-related topological skin effect is realized without the need of a
magnetic field or an electrical gate, with a record degree of localization for a
quantum Hall device. This new type of topological
quantum devices based on magnets, with an exponential response that can be switched at small
magnetic fields (about 200mT), can operate at
liquid-Helium temperature with a good quantization and have some potential as cryogenic sensors for applications in high-precision impedance or
magnetic field measurements.
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All authors Kyrylo Ochkan, Michael Wissmann, Louis Veyrat, Lixuan Tai, Minoru Kawamura, Yoshinori Tokura, Viktor Könye, Bernd Büchner, Jeroen van den Brink, Ion Cosma Fulga, Joseph Dufouleur, Romain Giraud
Soft Condensed Matter
Analytic solution of the multidensity Ornstein-Zernike equation for hard-sphere fluid with tetrahedral quadrupolar-like surface adhesion
Y. V. Kalyuzhnyi and P. T. Cummings
We develop a multidensity formulation of the Ornstein-Zernike equation with Percus-Yevick closure for hard spheres with anisotropic surface adhesion of tetrahedral quadrupolar-like
symmetry. An analytical solution is obtained using the invariant expansion method combined with Baxter's factorization technique. Structural properties are evaluated using both the multidensity theory and the previously proposed single-density molecular OZ approach. At low stickiness, the two theories yield nearly identical predictions, while increasing stickiness leads to growing discrepancies and eventual loss of convergence of the single-density approach. These results highlight the importance of multidensity descriptions for strongly associating anisotropic fluids.
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Statistical Mechanics
Charging capacitors using diodes at different temperatures. II Numerical studies
J. M.Mangum, L. L. Bonilla, A. Torrente et al. (+1 more)
This study is presented in a series of two papers. The first paper is an analytical study. This is the second paper, and here we numerically study the thermal energy harvesting capability of two electronic
circuits. The first
circuit consists of a diode and capacitor in series. We solve the time-dependent Fokker-Planck equation and show the capacitor initially charges and then discharges to zero. The peak charge on the capacitor increases with temperature, capacitance, and diode quality. The second
circuit has two current loops with one small capacitor, two storage capacitors, and two diodes wired in opposition. When the diodes are held at different temperatures we observe a non-zero steady-state charge is accumulated on both storage capacitors. The magnitude of the stored charges are nearly equal but the signs are opposite. When resistors are used in place of diodes there is no transient and no steady-state charge buildup. Numerical studies for the time-independent Fokker-Planck equation are presented and confirm the steady state charges.
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All authors J. M.Mangum, L. L. Bonilla, A. Torrente, P. M. Thibado
Statistical Mechanics
Charging capacitors using diodes at different temperatures. I Theor
L. L. Bonilla, A. Torrente, J. M. Mangum et al. (+1 more)
Nonlinear elements in a rectifying
circuit can be used to harvest energy from thermal fluctuations either steadily or transitorily. We study an energy harvesting system comprising a small variable capacitor (e.g., free standing
graphene) wired to two diodes and two storage capacitors that may be kept at different temperatures (or at a single one) and use two current loops. The system reaches very rapidly a quasi stationary state with constant overall charge while the difference of the charges at the storage capacitors evolves much more slowly to its stationary value. In this paper, we extract an exponentially small factor out of the solution of the Fokker-Planck equation and use a Chapman-Enskog procedure to describe the long
evolution of the marginal probability density for the charge difference, from the quasi stationary state to the final stationary state (thermal
equilibrium for equal temperatures). The second paper of this series shows that the results of the perturbation procedure compare well with direct numerical simulations. For a specific form of the diodes' nonlinear mobilities, we can approximate the quasi stationary state by Gaussian functions and further study the
evolution of the marginal probability density. The latter adopts the shape of a slowly expanding pulse (comprising left and right moving wave fronts whose fore edges become sharper as time elapses) in the space of charge differences that leaves the final stationary state behind it.
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All authors L. L. Bonilla, A. Torrente, J. M. Mangum, P. M. Thibado
Statistical Mechanics · Cross-listed from hep-th
On prethermal time crystals from semi-holography
Toshali Mitra, Sukrut Mondkar, Ayan Mukhopadhyay et al. (+1 more)
We demonstrate the existence of a pair of almost dissipationless oscillating modes at low temperatures in both the shear and sound channels of a hybrid
quantum system, comprised of a weakly self-interacting perturbative sector coupled to strongly self-interacting
holographic degrees of freedom described by a black hole geometry. We argue that these modes realize prethermal time-
crystal behavior in semi-
holographic systems without fine-tuning and can be observed by measuring operators that probe either the hard (perturbative) or the soft (
holographic) sector. We also find novel {short wavelength} instabilities that lead to the formation of inhomogeneities even at higher temperatures. These results provide evidence that black holes with planar horizons and dynamical boundary conditions can develop both inhomogeneous and metastable time-
crystal phases over a wide range of temperatures set by an intermediate scale given by the intersector coupling. Furthermore, they suggest that such phases can be realized without external driving in non-Abelian
plasmas of asymptotically free gauge theories in the large-$N$ limit.
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All authors Toshali Mitra, Sukrut Mondkar, Ayan Mukhopadhyay, Alexander Soloviev
Strongly Correlated Electrons · Cross-listed from hep-th
Classifying fusion rules of anyons or SymTFTs: A general algebraic formula for domain wall problems and quantum phase transitions
Yoshiki Fukusumi
We propose a formula for the transformation law of anyons in topologically ordered phases or topological
quantum field theories (TQFTs) through a gapped or
symmetry-preserving domain wall. Our formalism is based on the ring homomorphism between the $\mathbb{C}$-linear commutative fusion rings, also known as
symmetry topological field theories (SymTFTs). The fundamental assumption in our formalism is the validity of the Verlinde formula, applicable to commutative fusion rings. By combining it with more specific data of the settings, our formula provides classifications of anyons compatible with developing categorical formulations. It also provides the massless renormalization group (RG) flows between conformal field theories (CFTs), or a series of measurement-induced
quantum phase transitions, in the
language of SymTFT, through the established correspondence between CFTs and TQFTs. Moreover, by studying the correspondence between the ideal structure in the massless RG and the module in the related massive RG, one can make the Nambu-Goldstone-type arguments for generalized
symmetry. By combining our formula with orbifolding, extension, and similarity transformation, one can get a series of classifications for the corresponding extended models, or
symmetry-enriched topological orders and
quantum criticalities.
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Materials Science
Pressure-Tuned Metamagnetism and Emergent Three-Body Interactions in CsFeCl$_3$
K. Nihongi, T. Kida, Y. Narumi et al. (+11 more)
We present a combined experimental and theoretical study of the triangular-
lattice quantum antiferromagnet CsFeCl$_3$ under high
magnetic fields and high pressure. Pulsed-field magnetization for the
magnetic field along the symmetric $c$ direction at ambient pressure reveals a magnetization process from a nonmagnetic singlet ground state with a nearly linear increase between 3.7 and 10.7 T, a plateau-like region, and then a sharp stepwise metamagnetic transition near 32 T. Wide frequency–field range electron
spin resonance indicates that the low-field regime originates from the $J = 1$
manifold, while the high-field metamagnetic transition suggests a level crossing between the $J = 1$ and $J = 2$ lowest states. Pulsed-field
magnetic susceptibilities measured with a proximity detector oscillator under high pressure show that the low-field nonmagnetic singlet phase is gradually suppressed, while the high-field metamagnetic transition evolves into an increasingly rich pattern of fractional steps. While the observations at low to intermediate fields can be understood within the established
spin-1 description, the high-field regime requires a new perspective, which we provide through a projected
spin-1/2 framework built from Zeeman-selected
crystal-field states not related by time reversal. This construction naturally allows emergent three-body interactions on triangular plaquettes and explains the asymmetric
evolution of the fractional steps in the magnetization. Our findings reveal that high-field effective
spin models in
quantum magnets with separated yet accessible
crystal-field multiplets are not constrained to even-body couplings, but can naturally host odd-body terms, opening a broader avenue for realizing field-asymmetric magnetization processes and exotic phases beyond conventional even-body physics.
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All authors K. Nihongi, T. Kida, Y. Narumi, Y. Etoh, D. Yamamoto, M. Matsumoto, N. Kurita, H. Tanaka, K. Yu. Povarov, S. A. Zvyagin, J. Wosnitza, K. Kindo, Y. Uwatoko, M. Hagiwara
Materials Science
Defect Engineering for Stabilizing Magnetic and Topological Properties in Mn(Bi1-xSbx)2Te4
Haonan Chen, Jiayu Wang, Huayao Li et al. (+18 more)
MnBi2Te4 is a versatile platform for exploring diverse topological
quantum states, yet its potential is hampered by intrinsic antisite defects. While Sb substitution has been employed to tune the
Fermi level towards the charge neutral point, it exacerbates the formation of Mn-Sb antisite defects. Here, we address this challenge by combining first-principles calculations with strategic synthesis to systematically investigate and control antisite defects in Mn(Bi1-xSbx)2Te4. Our calculations reveal that increasing antisite defect density progressively destroys the field-forced
magnetic Weyl state, eventually driving the system into a trivial
magnetic insulator. Motivated by these findings, we develop an optimized chemical vapor transport method, yielding high-quality Mn(Bi1-xSbx)2Te4
crystals with significantly reduced antisite defect density. The emergence of strong Shubnikov-de Haas oscillations in the forced
ferromagnetic state and a pronounced anomalous
Hall effect near charge neutrality, with opposite signs for n- and p-type samples, confirms the type-II Weyl semimetal nature. These findings underscore the critical role of antisite defects in determining the
magnetic and topological properties of Mn(Bi1-xSbx)2Te4 and establish defect engineering via optimized synthesis as a crucial strategy for realizing its exotic
magnetic topological states.
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All authors Haonan Chen, Jiayu Wang, Huayao Li, Xunkai Duan, Yuxiang Wang, Zixuan Xu, Yingchao Xia, Wenhao He, Zehao Jia, Xiangyu Cao, Yicheng Mou, Xiangyu Jiang, Jiaming Gu, Pengliang Leng, Fengfeng Zhu, Changlin Zheng, Xiang Yuan, Faxian Xiu, Tong Zhou, Lin Miao, Cheng Zhang
Materials Science
Symmetry-guided prediction of magnetic-ordered ground states
Yuhui Li, Sike Zeng, Yutong Yu et al. (+4 more)
Given the scarcity of experimentally confirmed
magnetic structures, the prediction of
magnetic ground states is crucial yet remains a long-sought challenge due to the complex potential energy landscape. Here, we propose a
symmetry-guided framework that systematically generates
magnetic configurations without requiring any experimental input or prior assumptions. Within a
symmetry-breaking scenario, we incorporate the recently developed oriented
spin space group formalism, which captures
symmetry-breaking induced by both
magnetic ordering and
spin-orbit coupling. By performing nonrelativistic and relativistic first-principles calculations, we establish the energy ladder of the generated
magnetic configurations. Exemplified by three prominent unconventional magnets, we demonstrate that only a few dozen calculations are sufficient to identify the ground-state
magnetic structure. To demonstrate the universality and robustness of our approach, we conduct large-scale
benchmark tests on the MAGNDATA database. Our framework successfully reproduces experimentally reported
magnetic geometries for 78% of the surveyed materials, among which 93% have their
spin orientations successfully generated when considering SOC. Furthermore, in a large-scale first-principles
benchmark involving 305 compounds, 82% of experimentally reported
magnetic structures are accurately captured within an energy tolerance of 5 meV per
magnetic atom. Beyond reproducing known
magnetic configurations, our framework further predicts a variety of low-energy metastable phases, including altermagnets,
spin-orbit magnets, and noncollinear antiferromagnets with
spin splitting or
geometric Hall effect. Our work establishes a general and efficient route toward large-scale prediction of
magnetic structures and unconventional magnets, and offers insight into the origins of
magnetic interactions across diverse material systems.
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All authors Yuhui Li, Sike Zeng, Yutong Yu, Renzheng Xiong, Yu-Jun Zhao, Xiaobing Chen, Qihang Liu
Strongly Correlated Electrons
Linear Foundation Model for Quantum Embedding: Data-Driven Compression of the Ghost Gutzwiller Variational Space
Samuele Giuli, Hasanat Hasan, Benedikt Kloss et al. (+5 more)
Simulations of
quantum matter rely mainly on Kohn-Sham density functional theory (DFT), which often fails for strongly correlated systems.
Quantum embedding (QE) theories address this limitation by mapping the system onto an auxiliary
embedding Hamiltonian (EH) describing fragment-environment interactions, but the EH is typically large and its iterative solution is the primary computational bottleneck. We introduce a linear foundation model for QE that utilizes principal component analysis (PCA) to compress the space of
quantum states needed to solve the EH within a small variational subspace. Using a data-driven active-learning scheme, we learn this subspace from EH ground states and reduce each
embedding solve to a deterministic ground-state
eigenvalue problem in the reduced space. Within the ghost Gutzwiller approximation (ghost-GA), we show for a three-orbital Hubbard model that a variational space learned on a Bethe
lattice is transferable to square and cubic
lattices without additional training, while substantially reducing the cost of the EH step. We further validate the approach on plutonium, where a single variational space reproduces the energetics of all six crystalline phases while reducing the cost of the EH solution by orders of magnitude. This provides a practical route to overcome the main computational bottleneck of QE frameworks, paving the way for high-throughput ab initio simulations of strongly correlated materials at a near-DFT cost.
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All authors Samuele Giuli, Hasanat Hasan, Benedikt Kloss, Marius S. Frank, Tsung-Han Lee, Olivier Gingras, Yong-Xin Yao, Nicola Lanatà
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Spectroscopic Search for Topological Protection in Open Quantum Hardware: The Dissipative Mixed Hodge Module Approach
Prasoon Saurabh
Standard spectroscopic protocols model the dynamics of open
quantum systems as a superposition of isolated, exponentially decaying eigenmodes. This paradigm fails fundamentally at Exceptional Points, where the eigenbasis collapses and the response becomes dominated by non-diagonalizable Jordan blocks. We resolve this ambiguity by introducing a
geometric framework based on Dissipative Mixed Hodge Modules (DMHM). By replacing the scalar linewidth with a topological Weight Filtration, we derive “Weight Filtered Spectroscopy” (WFS)–a protocol that spatially separates decay channels based on the nilpotency rank of the Liouvillian. We demonstrate that WFS acts as a dissipative x-ray, quantifying dissipative leakage in molecular polaritons and certifying topological isolation in Non-Hermitian Aharonov-Bohm rings. This establishes that topological protection persists as an algebraic invariant even when the spectral gap is closed.
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Mesoscale and Nanoscale Physics
Proximity-Induced Spin-Orbit Torque in Graphene on a Trigonal CrSBr Monolayer
Maedeh Rassekh and Martin Gmitra
We present a first-principles and
quantum transport study of proximity-induced
spin-orbit torque (SOT) in
graphene on a trigonal CrSBr monolayer. Density functional theory combined with nonequilibrium Green's function calculations shows that the CrSBr substrate induces
spin polarization and a sizable exchange splitting in the
graphene Dirac states. The resulting current-driven
spin density in
graphene generates a self-SOT on the Dirac electrons. The proximity-induced exchange field breaks time-reversal
symmetry and gives rise to a purely odd SOT component, while the even contribution vanishes. The torque magnitude exhibits a strong angular dependence with phase shifts arising from the noncollinearity between the CrSBr magnetization and the induced
magnetic moments in
graphene. Monte Carlo simulations based on the calculated exchange parameters predict a Curie temperature of approximately 304 K, confirming the robustness of ferromagnetism in the trigonal CrSBr monolayer. These results identify
graphene/CrSBr
heterostructures as a promising platform for room-temperature two-dimensional spintronics.
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Soft Condensed Matter
The Origin of Organic Magnetoresistance Using Time-Domain Magnetic Spectroscopy
Paul Ben Ishai, Roshlin Kiruba and Amos Bardea
Organic Magnetoresistance is defined as the change of resistance in an organic material, such as a conducting
polymer, as a function of an imposed
magnetic field. We demonstrate this effect in a Polypyrrole/ Polydimethylsiloxane complex by using a novel
magnetic pulse system. The frequency spectrum of the current flowing through the sample reveals equally spaced reversed peaks in the current. We show that these peaks happen at the Lamour frequency for the dominant charge carrier of the system, namely polarons. This posits the origin Organic magnetoresistance as simple Rabi Oscillations rather than mechanisms based of bipolaron formation and singlet-triplet conversions. We directly estimate the effective polaronic mass in this complex. A semi classical theoretical approach is suggested to explain this effect as direct
spin flipping in a time transient
magnetic field. This is the first time that such an experimental approach has been applied in this field and the first time the effective polaronic mass has been measured in a conducting
polymer.
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Strongly Correlated Electrons
Nonvolatile optical switching of surface metallicity in 1T-TaSe2
Junde Liu, Liwen Su, Pei Liu et al. (+12 more)
The surface of a
quantum material provides a distinct electronic environment in which reconstruction can stabilize states absent from the bulk. However, whether light can persistently reconfigure this surface-bulk electronic contrast remains unclear. Here we demonstrate nonvolatile and reversible optical
insulator-to-metal switching at the surface of the charge density wave (CDW) material 1T-TaSe2, whose bulk is metallic. Angle-resolved photoemission spectroscopy reveals that a single femtosecond pulse creates a persistent metallic surface state. Heating or optical pulse trains restore the insulating state. Comparison of the measured band structures with first-principles calculations associates the two electronic states with distinct near-surface CDW stacking configurations that modify interlayer-mediated electron hopping. Layer-resolved calculations further show insulating outer layers above a metallic interior in the
equilibrium configuration, whereas metallic states reach the outermost layer in the configuration associated with the photoinduced state. Our results establish persistent optical control of surface
metallicity and open a route to reconfiguring the effective surface-bulk electronic boundary in layered
quantum materials.
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All authors Junde Liu, Liwen Su, Pei Liu, Hui Liu, Mojun Pan, Yuchong Zhang, Famin Chen, Yueqian Chen, Zhaoyang Xie, Stefan Mathias, Tianping Ying, Lin Hu, Tian Qian, Xun Shi, Yugui Yao
Mesoscale and Nanoscale Physics
Spatiotemporal chaos in the interface growth of topological insulators
Yutaro Tanaka and Akira Furusaki
We demonstrate that topological
insulators exhibit an intrinsic interfacial instability that amplifies small interface fluctuations, resulting in chaotic behavior during interface growth. This mechanism is different from conventional interfacial instabilities in
crystal growth that are driven by external non-uniformities such as surface
diffusion, and instead arises from intrinsic electronic properties of topological materials. We find that the boundary states of topological
insulators have a pronounced impact on the surface stiffness, which quantifies how strongly a surface resists changes in its shape or orientation. While trivial
insulators possess positive stiffness that smooths out surface roughness, topological
insulators exhibit negative stiffness that amplifies small shape fluctuations. We derive an effective equation of the interface growth with this negative stiffness and demonstrate that the interface dynamics is governed by the Kuramoto–Sivashinsky equation, a prototypical nonlinear equation exhibiting spatiotemporal chaos.
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Mesoscale and Nanoscale Physics
Fractional High-Chern Insulator in Twisted Rhombohedral Graphene
Zexu Li, Wenxuan Wang, Fajie Wang et al. (+9 more)
The realization of fractional Chern
insulators opens up the possibility of exploring fractionally charged excitations and anyonic statistics in the absence of a
magnetic field. A central question is whether
lattice-based systems can give rise to radically new states, distinct from those observed in traditional fractional
quantum Hall systems. In this work, we investigate a new type of moiré flat band system composed of Bernal
bilayer graphene and rhombohedral tetralayer
graphene. We discover an unprecedented richness of
quantum anomalous
Hall insulators with Chern numbers from C = 1 to C = 7 at v = 1 and around v = 3. Remarkably, we observe an exotic fractional Chern
insulator with C = 7/3 around v = 2/3 which is beyond all known fractional Chern
insulators described by either the Jain sequence or current high Chern theory. Our work expands the understanding of fractionally charged excitations beyond the Landau level basis and offers a new moire platform for exploring anyons.
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All authors Zexu Li, Wenxuan Wang, Fajie Wang, Zaizhe Zhang, Qiu Yang, Kenji Watanabe, Takashi Taniguchi, X.C. Xie, Jie Wang, Kaihui Liu, Zhida Song, Xiaobo Lu
Mesoscale and Nanoscale Physics
Entangled Moire Chern Insulator in Rhombohedral Graphene
Zaizhe Zhang, Xi Chen, Kenji Watanabe et al. (+3 more)
Graphene-based moire superlattices exhibit novel
quantum phenomena driven by pronounced interactions, leading to topological corrected states like orbital Chern
insulators exhibiting
quantum anomalous
Hall effect (QAHE). Typically, intrinsic Chern
insulators are stabilized at odd moiré fillings, as even fillings often result in valley-balanced, topologically trivial states at zero
magnetic field. In our work, we report the observation of an intrinsic Chern
insulator with C = 1 state at moire filling v = 2 in rhombohedral octalayer
graphene (R8G)/hBN moire superlattice. Observing such Chern
insulators in particular with C = 1 at v = 2 is intriguing, as each moiré band carries Chern number C = 1 or -1. We further demonstrate such a state can originate from the
entanglement between the low-energy moire flat bands and high-energy remote bands according to the Hartree-Fock calculation. Our findings extend the known topological phase diagram of rhombohedral multilayer
graphene (RMG) moire systems and establish this platform as highly promising for investigating strong electron correlations and multiband hybridized transport.
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All authors Zaizhe Zhang, Xi Chen, Kenji Watanabe, Takashi Taniguchi, Zhida Song, Xiaobo Lu
Disordered Systems and Neural Networks · Cross-listed from physics.optics
Incorporating rank-free coupling and external field via an incoherent modulated spatial photonic Ising machine
Ze Zheng, Yuegang Li, Hang Xu et al. (+3 more)
Spatial photonic Ising machines offer a novel optical platform for optimization and
spin-model simulation, but existing diffraction-based schemes rely on auxiliary
spins or multiplexing to encode high-rank couplings and external fields, reducing either speed or
spin count. We demonstrate an amplitude-only, rank-free spatial photonic Ising machine in which arbitrary Ising
Hamiltonians are encoded as Hadamard products on aligned amplitude and binary spatial modulators and read out by a single-pixel intensity measurement. The machine directly programs fully connected 797-
spin Ising models with external fields at nearly 9-bit precision and operates at a constant iteration rate of ~200 Hz. By removing zero-valued product terms, the same architecture scales to sparse problems and experimentally solves a Max-Cut instance on a 424,108-vertex Mobius ladder graph. We also observe the phase transition of the Sherrington-Kirkpatrick model, demonstrating programmable optical simulation beyond low-rank couplings. These results establish amplitude modulation as a scalable route to programmable photonic Ising machines.
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All authors Ze Zheng, Yuegang Li, Hang Xu, Jingzheng Huang, Tailong Xiao, Guihua Zeng
Materials Science
Account of the self-interaction energy correction in the first principles calculation of the fundamental absorption edge spectrum of LiCl
M.A.Bunin and I.I Geguzin
Within the framework of the local electron density functional theory, an ab-initio method is proposed that takes into account the self-interaction energy correction (SIC) for the
crystal potential. The principle of dividing the unit
cell into regions remained the same as for the ground-state potential. The expression for the self-consistent muffin-tin-SIC potential satisfies the condition of
cell electroneutrality. This scheme was applied to calculate the spectrum of the fundamental absorption edge of LiCl. The obtained interband transition energies were not required for fitting to experimental values. In the calculated spectrum, the shape and position of the peaks above ~2.5 eV from the edge agree fairly well with the measured ones, which allows their intensity in this region to be attributed primarily to interband transitions. Closer to the edge, electron-hole interaction significantly alters the ground state, which must be taken into account when calculating the spectrum shape.
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Strongly Correlated Electrons
Kondo Effect in Nonreciprocal Response
Hajime Murata and Hiroaki Ishizuka
Chiral magnetic states give rise to rich phenomena, from the anomalous
Hall effect and the nonlinear electrical current to multiferroics and magnetochiral dichroism. Most of the studies on electrical transport so far have focused on the cases where the
magnetic moments are well approximated by classical local moments. Here, we reveal that the coexistence of
quantum fluctuations and
chiral spin correlations gives rise to a $\log(T)$ temperature dependence in the electrical magnetochiral effect, a nonreciprocal response. Using the Green's function method and a scattering theory approach, we show that the $\log(T)$ temperature dependence occurs through a scattering process similar to that of the Kondo effect. The electrical magnetochiral effect is sensitive to the sign of vector
spin chirality and the
magnetic field. The results demonstrate that local
spin correlations and
quantum fluctuations cooperatively induce nontrivial properties in transport phenomena.
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Materials Science
Nonvolatile Electrical Control of Spin via Sliding Fractional Quantum Multiferroics
Jiajun Lu, Mu Tian, Chaoxi Cui et al. (+3 more)
We propose a fractionally quantized polarization induced by interlayer sliding in
bilayer altermagnets, unveiling a previously unrecognized multiferroic phase termed sliding fractional
quantum multiferroicity (SFQM). This unconventional
magnetic phase uniquely integrates sliding ferroelectricity with fractional
quantum ferroelectricity, enabling highly efficient switching and nonvolatile electrical control of
spin.~Unlike conventional multiferroics, SFQM simultaneously exhibits
lattice-scale atomic displacements, ultralow switching barriers, and
spin splitting, giving rise to a large fractionally quantized polarization and strong magnetoelectric coupling. Through
symmetry analysis and first-principles calculations, we identify
bilayer altermagnet Ca(CoN)$_2$ and its family materials as promising candidates hosting SFQM. In contrast to gate-controlled schemes, the
spin-layer coupling in SFQM is intrinsically induced by spontaneous electrical and layer polarization, requiring no sustained gate field and exhibiting nonvolatile character. This mechanism enables nonvolatile electrical control of
spin through biaxial sliding, where displacements along the x- and y-axes generate opposite polarization directions in the layer-dependent electrical polarization. Furthermore, SFQM exhibits a fully switchable anomalous
Hall effect and a pronounced magneto-optical response, which can be utilized for its detection and distinction. These findings highlight the promising role of sliding-mediated couplings among unconventional magnetism, fractional
quantum ferroelectricity, and stacking order in realizing electrically controllable two-dimensional multiferroics.
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All authors Jiajun Lu, Mu Tian, Chaoxi Cui, Zhi-Ming Yu, Run-Wu Zhang, Yugui Yao
Mesoscale and Nanoscale Physics
Higher-order exceptional ring semimetal with real hinge states in phononic crystals
Yejian Hu, Zhenhang Pu, Xiangru Chen et al. (+5 more)
Non-Hermitian topological phase, with the novel concepts such as exceptional points and skin effect, has opened up a new paradigm beyond Hermitian topological physics. Exceptional ring semimetal, featured by a stable ring of exceptional points in three dimensions, exhibits first-order topological properties, including topological surface states and surface-dependent skin effect. Nevertheless, despite extensive research on Hermitian higher-order
insulators and semimetals, higher-order exceptional ring semimetal is just emerging. Here, we report the first realization of a higher-order Weyl exceptional ring semimetal in a three-dimensional lossy phononic
crystal. The non-Hermitian higher-order
topology reflects in the topological hinge states and hinge-dependent skin effect. Counterintuitively, the topological hinge states maintain purely real energy even under a high loss level, ensuring robust hinge-state propagation. Our findings evidence the non-Hermitian higher-order bulk-boundary correspondence of exceptional ring semimetal, and may pave the way to non-Hermitian functional acoustic devices.
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All authors Yejian Hu, Zhenhang Pu, Xiangru Chen, Yuxiang Xi, Jiuyang Lu, Weiyin Deng, Manzhu Ke, Zhengyou Liu
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Under pressure: poroelastic regulation of flow in espresso brewing
Radost Waszkiewicz, Franciszek Myck, Łukasz Białas et al. (+4 more)
The sensory richness of coffee is widely recognised and arises from the complex chemistry and immersion in cultural practices of coffee preparation. In contrast, the physical complexity of espresso has received less
attention. The multiphase reactive flow through a dissolving, elastic porous medium remains challenging to describe. Using a controlled experimental setup based on a café-grade espresso machine, we demonstrate that the interplay between elasticity and porosity governs the long-time flow rate during espresso extraction and, consequently, the concentration of solubles in the final beverage. We introduce a minimal model that captures the resulting non-linear pressure-flow relationship and propose a methodology capable of reproducing the time-dependent behaviour of the espresso brewing process. Finally, we show that dissolution dynamics play a central role in determining the temporal
evolution of flow during extraction.
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All authors Radost Waszkiewicz, Franciszek Myck, Łukasz Białas, Maria Puciata-Mroczynska, Michał Dzikowski, Piotr Szymczak, Maciej Lisicki
Strongly Correlated Electrons
Thermodynamic-Limit Evidence for Chiral Superconductivity Induced by Doping Chiral Topological Phases
Sen Niu, D. N. Sheng and Yang Peng
The emergence of superconductivity from doping strongly correlated
chiral topological phases in purely repulsive two-dimensional fermionic systems is a problem of broad and fundamental interest. However, existing numerical evidence has been limited to finite-size studies, and direct thermodynamic-limit evidence for superconducting long-range order has remained lacking. Here we provide such evidence for
chiral superconductivity in the triangular Hofstadter-Hubbard model by advancing a simplex tensor-network approach that simultaneously captures superconducting long-range order and
chiral topological order in the presence of intrinsic charge fluctuations, a capability that has remained challenging for previous two-dimensional approaches. We show that a broad intermediate-$U$
chiral spin liquid is separated from the weak-$U$ Chern
insulator by a Mott transition, together forming undoped parent
chiral topological states. Upon hole doping, we identify a uniform
chiral superconducting state in the infinite system, characterized by a finite complex pairing order parameter. The pairing field exhibits an almost universal phase winding over a broad interaction-doping regime, with a distinct pocket of opposite winding near the Mott criticality. In addition, the
entanglement spectrum retains the
chiral structure of the parent topological phases while developing additional low-energy branches upon doping. These results establish that
chiral superconductivity emerges robustly from doped
chiral topological phases.
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