Disordered Systems and Neural Networks · Cross-listed from quant-ph
Ruelle-Pollicott Decay of Out-of-Time-Order Correlators in Many-Body Systems
Jerónimo Duarte, Ignacio García-Mata and Diego A. Wisniacki
The out-of-time-order correlator (OTOC) quantifies information scrambling in
quantum systems and serves as a key diagnostic of
quantum chaos. In one-body systems with a classical counterpart, the relaxation of the OTOC is governed by Ruelle-Pollicott resonances. For many-body systems lacking a semiclassical limit, recent studies have identified an analogous role played by the Liouvillian spectrum of weakly open extensions of the dynamics, where the slowest decay rate – the Liouvillian gap – encodes relaxation. Here we study the kicked Ising
spin chain and show that the long-time exponential decay of the OTOC in the isolated system occurs at a rate equal to twice this intrinsic gap. This correspondence is demonstrated across parameter regions exhibiting distinct level spacing statistics, indicating that the Liouvillian spectrum provides a robust framework for characterizing relaxation and irreversibility in closed many-body
quantum systems.
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Mesoscale and Nanoscale Physics
Néel vector controlled charge and spin transport in altermagnetic junctions
Shubham Ghadigaonkar, Sachchidanand Das and Abhiram Soori
Altermagnets (AMs) -
magnetic materials that have
spin-split bandstructure with zero net
spin polarization can be classified as weak or strong depending upon the strength of altermagnetic term in the
Hamiltonian. We theoretically investigate electron transport in junctions between the two AMs in strong and weak altermagnetic phases. The charge and
spin conductivities are analyzed as functions of angle $\theta$ between the Néel vectors of the two AMs. In the strong AM regime, the charge conductivity vanishes as $\theta \to \pi$, while in the weak AM regime it remains finite. Introducing a normal metal (NM) between two AMs leads to Fabry-Pérot-type oscillations in charge conductivity which can be controlled by an applied gate voltage. In the strong regime, transport in AM-NM-AM junctions is dominated by up-
spin electrons, whereas both
spin channels contribute in the weak regime. These results highlight the potential of AM-based
heterostructures for spintronic applications, such as
spin filters, and
quantum interference-based spintronic devices, where tunable
spin-dependent transport and interference effects can be utilized in electronic devices without a need for externally applied
magnetic field.
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Mesoscale and Nanoscale Physics
Disorder-assisted Spin-Filtering at Metal/Ferromagnet Interfaces: An Alternative Route to Anisotropic Magnetoresistance
Ivan Iorsh and Mikhail Titov
We introduce a minimal interface-scattering mechanism that produces a sizable anisotropic magnetoresistance (AMR) in metal/ferromagnet
bilayers (e.g., Pt/YIG) without invoking bulk
spin or orbital
Hall currents. In a $\delta$-layer model with interfacial exchange and Rashba
spin-orbit coupling, charge transfer at a high-quality interface creates a
spin-selective phase condition (interfacial
spin filtering) that suppresses backscattering for one
spin projection while enhancing momentum relaxation for the other. The resulting resistance anisotropy peaks at an optimal metal thickness of a few nanometers, quantitatively reproducing the thickness and angular dependences typically attributed to
spin Hall magnetoresistance (SMR), as well as its characteristic magnitude. Remarkably, the maximal AMR scales linearly with the smaller of the two coupling strengths - exchange or
spin-orbit, highlighting a mechanism fundamentally distinct from SMR. Our scattering formulation maps onto Boltzmann boundary conditions and predicts other clear discriminants from SMR, including strong sensitivity to interfacial charge transfer and disorder.
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Statistical Mechanics · Cross-listed from quant-ph
Signatures of Topological Symmetries on a Noisy Quantum Simulator
Christopher Lamb, Robert M. Konik, Hubert Saleur et al. (+1 more)
Topological
symmetries, invertible and otherwise, play a fundamental role in the investigation of
quantum field theories. Despite their ubiquitous importance across a multitude of disciplines ranging from string theory to condensed matter physics, controlled realizations of models exhibiting these
symmetries in physical systems are rare.
Quantum simulators based on engineered solid-state devices provide a novel alternative to conventional condensed matter systems for realizing these models. In this work, eigenstates of
impurity Hamiltonians and loop operators associated with the topological
symmetries for the Ising conformal field theory in two space-time dimensions are realized on IBM's Kingston simulator. The relevant states are created on the
quantum device using a hybrid
quantum-classical
algorithm. The latter is based on a variation of the
quantum approximate optimization
algorithm ansatz combined with the
quantum natural gradient optimization method. Signatures of the topological
symmetry are captured by measuring correlation functions of different
qubit operators with results obtained from the
quantum device in reasonable agreement with those obtained from classical computations. The current work demonstrates the viability of noisy
quantum simulators as platforms for investigating low-dimensional
quantum field theories with direct access to observables that are often difficult to probe in conventional condensed matter experiments.
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All authors Christopher Lamb, Robert M. Konik, Hubert Saleur, Ananda Roy
Strongly Correlated Electrons
Quantum Fisher Information as a Thermal Probe in Frustrated Magnets through Insights from Quantum Spin Ice
Chengkang Zhou, Zhengbang Zhou, Félix Desrochers et al. (+2 more)
Quantum Fisher information (QFI) is a measure of multipartite
entanglement accessible via inelastic
neutron scattering. Here we demonstrate that QFI reveals thermal and dynamical properties of
quantum spin ice (QSI), a three-dimensional
quantum spin liquid with fractionalized excitations. By developing a multi-directed loop update
quantum Monte Carlo
algorithm, along with exact diagonalization and gauge mean-field theory, we compute the QFI for the pyrochlore
lattice. The temperature and momentum dependence of QFI maps the phase diagram, distinguishing the
ferromagnetic ordered phase, its critical region, the zero-flux QSI, and the $\pi$-flux QSI. QFI also captures two crossover scales: from trivial paramagnet to classical
spin ice, then to QSI. We discuss the $\pi$-flux QSI in light of experiments on cerium-based pyrochlores. Our results suggest that QFI not only detects
entanglement but also serves as a sensitive thermal and dynamical probe for frustrated
quantum magnets.
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All authors Chengkang Zhou, Zhengbang Zhou, Félix Desrochers, Yong Baek Kim, Zi Yang Meng
Soft Condensed Matter
Grain volume distribution alters the critical phenomena in complex granular systems
Teng Man, Yimin Lu, Zhongrong Wang et al. (+3 more)
The grain size distribution (GSD) plays an important role in the mechanical properties of amorphous disordered systems and complex granular materials. Varying GSD causes segregation issues and alters critical behaviors. This work used the discrete element method (DEM) to investigate the rheological and critical behaviors of sheared granular flows with various GSDs. The results show that, while a unified rheological relation can be obtained, a characteristic length scale, which is associated with the contact probability and can be obtained from any GSD, is embedded within such a polydisperse disordered system. We further acquire a correlation function between critical solid fractions and dimensionless grain volume distributions. This work elucidates the effect of particle volumes on the rheology and micromechanics of dry granular systems and provides further insights in better incorporating the influence of other particle properties into a unified framework, which is helpful and critical for the corresponding engineering and geophysical problems.
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All authors Teng Man, Yimin Lu, Zhongrong Wang, Herbert Huppert, Alessio Zaccone, Honglei Sun
Other Condensed Matter
Topological bands in metals
Yu. B. Kudasov
In crystalline systems with a superstructure, the electron dispersion can form a nontrivial covering of the Brillouin zone. It is proved that the number of sheets in this covering and its monodromy are topological invariants under ambient isotopy. As a concrete manifestation of this nontrivial
topology, we analyze three-sublattice models for 120$^\circ$-ordered helimagnets in one, two, and three dimensions. The two-dimensional system exhibits unconventional $f$-wave magnetism and a specific topological metal state characterized by a
spin-textured, one-sheeted
Fermi surface. The observable transport signatures of the topological metal and its potential experimental realization are briefly discussed.
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Strongly Correlated Electrons
Quantum oscillations and transport properties of layered single-crystal SrCu$_4$As$_2$
Sudip Malick, Michał J. Winiarski, Joanna Bławat et al. (+3 more)
We report a systematic investigation of the physical properties and
Fermi-surface
topology of layered single-
crystal \ce{SrCu4As2} using electrical transport, magnetotransport, and
quantum-oscillation experiments plus band-structure calculations. The temperature-dependent electrical resistivity reveals a hysteretic phase transition at $T_P$ = 59 K, most likely associated with a structural change.
Hall resistivity data suggest a marked change in the average hole density resulting from the latter phase transition near $T_P$. A large, linear, and nonsaturating magnetoresistance is observed at low temperatures in \ce{SrCu4As2}, likely attributable to the multipocket
Fermi surface.
Quantum-oscillation data measured in
magnetic fields of up to 60 T show several oscillation frequencies exhibiting low effective masses, indicating the presence of Dirac-like band dispersion in \ce{SrCu4As2}, as suggested by the band structure calculations.
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All authors Sudip Malick, Michał J. Winiarski, Joanna Bławat, Hanna Świątek, John Singleton, Tomasz Klimczuk
Soft Condensed Matter
Aging and configurational memories at rough frictional interfaces
Kasra Farain and Daniel Bonn
Frictional interfaces retain distinct
memories of how they were sheared and how long they have rested, yet rate-and-state descriptions typically compress these histories into a single state variable. Here we combine nanometer-per-second sliding experiments on rough multi-asperity contacts with different protocols to disentangle temporal and configurational
memories at frictional onset. We identify a broad friction force peak associated with shear-driven reorganization of the load-bearing contact network. By contrast, holding a previously sheared system at rest in an arrested configuration produces a much narrower friction force peak that grows approximately logarithmically with hold time and relaxes over nanometer-scale slip distances. Configurational disorder without waiting regenerates only the broad peak, whereas waiting without configurational disorder generates only the aging peak. These results show that aging and configurational disorder write and read experimentally separable frictional
memories, and that static friction is a protocol-dependent quantity rather than a fixed material property.
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Strongly Correlated Electrons · Cross-listed from math-ph
Quantum Knizhnik-Zamolodchikov Equations and Integrability of Quantum Field Theories with Time-dependent Interaction Strength
Parameshwar R. Pasnoori
In this paper we consider the problem of solving
quantum field theories with time dependent interaction strengths. We show that the recently formulated framework [P. R. Pasnoori, Phys. Rev. B 112, L060409 (2025)], which is a generalization of the regular Bethe ansatz technique, provides the exact many-body wavefunction. In this framework, the time-dependent Schrodinger equation is reduced to a set of analytic difference equations and
matrix difference equations, called the
quantum Knizhnik-Zamolodchikov (qKZ) equations. The consistency of the solution gives rise to constraints on the time-dependent interaction strengths. For interaction strengths satisfying these constraints, the system is integrable, and the solution to the qKZ and the analytic difference equations provides the explicit form of the many-body wavefunction that satisfies the time-dependent Schrodinger equation. We provide a concrete example by considering the $SU(2)$ Gross-Neveu model with time dependent interaction strength. Using this framework we solve the model with the most general time-dependent interaction strength and obtain the explicit form of the wave function.
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Statistical Mechanics
Transport with noise in dilute gases: Effect of Langevin thermostat on transport coefficients
Alejandro Alés, Juan Ignacio Cerato, Leandro Marchioni et al. (+1 more)
In dilute gases, transport properties such as the thermal conductivity, self-
diffusion, and viscosity are significantly affected by interatomic collisions, which are determined by the potential form. This study explores these transport properties in the presence of a Langevin thermostat in systems where particles interact through various potentials, including soft-core and hard-core potentials, both with and without an attractive region. Using molecular dynamics simulations and a theoretical approach based on an analogy with an electric
circuit (Ohm's law), we derived and compared the transport coefficients across these interatomic potentials for different couplings with the thermostat. The transport coefficients were obtained by considering the thermostat as a resistance in a series
circuit.
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All authors Alejandro Alés, Juan Ignacio Cerato, Leandro Marchioni, Miguel Hoyuelos
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Unsupervised Learning to Recognize Quantum Phases of Matter
Mehran Khosrojerdi, Alessandro Cuccoli, Paola Verrucchi et al. (+1 more)
Drawing the
quantum phase diagram of a many-body system in the parameter space of its
Hamiltonian can be seen as a learning problem, which implies labelling the corresponding ground states according to some classification criterium that defines the phases. In this work we adopt unsupervised learning, where the
algorithm has no access to any priorly labeled states, as a tool for determining
quantum phase diagrams of many-body systems. The
algorithm directly works with
quantum states: given the ground-state configurations for different values of the
Hamiltonian parameters, the process uncovers the most significant way of grouping them based on a similarity criterion that refers to the fidelity between
quantum states, that can be easily estimated, even experimentally. We
benchmark our method with two specific
spin-$\frac{1}{2}$ chains, with states determined via tensor network techniques. We find that unsupervised learning
algorithms based on spectral clustering, combined with “silhouette” and “elbow” methods for determining the optimal number of phases, can accurately reproduce the phase diagrams. Our results show how unsupervised learning can autonomously recognize and possibly unveil novel phases of
quantum matter.
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All authors Mehran Khosrojerdi, Alessandro Cuccoli, Paola Verrucchi, Leonardo Banchi
Soft Condensed Matter
Nonreciprocal buckling makes active filaments polyfunctional
Sami C. Al-Izzi, Yao Du, Jonas Veenstra et al. (+5 more)
Active filaments are a workhorse for propulsion and actuation across biology, soft robotics and mechanical metamaterials. However, artificial active rods suffer from limited robustness and adaptivity because they rely on external control, or are tethered to a substrate. Here we bypass these constraints by demonstrating that non-reciprocal interactions lead to large-scale unidirectional dynamics in free-standing slender structures. By coupling the bending modes of a buckled beam anti-symmetrically, we transform the multistable dynamics of elastic snap-through into persistent cycles of shape change. In contrast to the critical point underpinning beam buckling, this transition to self-snapping is mediated by a critical exceptional point, at which bending modes simultaneously become unstable and degenerate. Upon environmental perturbation, our active filaments exploit self-snapping for a range of functionality including crawling, digging and walking. Our work advances critical exceptional physics as a guiding principle for programming instabilities into functional active materials.
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All authors Sami C. Al-Izzi, Yao Du, Jonas Veenstra, Richard G. Morris, Anton Souslov, Andreas Carlson, Corentin Coulais, Jack Binysh
Superconductivity
Crossed surface flat bands in three-dimensional superconducting altermagnets
Yuri Fukaya, Bo Lu, Keiji Yada et al. (+2 more)
Superconducting altermagnets have proven to be a promising ground for emergent phenomena, but their study has involved two-dimensional systems. In this work, we investigate three-dimensional $d$- and $g$-wave altermagnets with
spin-singlet
chiral $d$-wave superconductivity and show the formation of crossed surface flat bands due to the interplay between superconducting and altermagnetic
symmetries. We find that these crossed flat bands are topologically protected, appear at zero energy in the surface along $z$ due to the superconducting nodal lines in the $xy$-plane, and their number of corners is determined by the
crystal symmetry of altermagnets. We also show that the superconducting nodal lines give rise to Bogoliubov-
Fermi surfaces, which then affect the appearance of zero-energy arcs in the surface along $x$. Moreover, we demonstrate that the crossed flat bands or surface arcs, and Bogoliubov-
Fermi surfaces give rise to the coexistence of three distinct dependences of the charge conductance on the normal transparency, hence offering a solid way for their detection and paving the way for realizing higher-dimensional topological phases using altermagnets.
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All authors Yuri Fukaya, Bo Lu, Keiji Yada, Yukio Tanaka, Jorge Cayao
Mesoscale and Nanoscale Physics
Fundamental quantum and relativistic formulation of thermal noise and linear conductance in an 1D quasi-particle ensemble under ballistic transport-regime
Lino Reggiani, Federico Intini and Luca Varani
We investigate
quantum and
quantum-relativistic effects associated with the noise power spectrum and the fluctuation–dissipation relation between current–noise spectra and linear–response conductance at low frequencies of the electromagnetic field. At high frequencies,
vacuum catastrophe is shown to be avoided by the presence of Casimir force. At low frequencies, the
quantum effect associated with one–dimensional structures under the conditions of ballistic transport typical at the nanometric scale length are briefly reviewed in terms of a universal quasi-particle approach. The case of a
photon gas inside an appropriate black-body cavity is found to provide a physical interpretation of the lines spectra of atomic elements within an exact statistical approach based on a physical interpretation of the fine structure constant, $\alpha =1/137.0560$.
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Materials Science
Identification of formation of amorphous Si phase in SiOxNy films produced by plasma enhanced chemical vapor deposition
M. V. Voitovych, A. Sarikov, V. O. Yukhymchuk et al. (+2 more)
Peculiarities of formation of inclusions of amorphous Si (a-Si) phase in Si-rich Si oxynitride films grown by
plasma-enhanced chemical vapor deposition (PECVD) are studied by combined Raman scattering and infrared (IR) absorption spectroscopy. The Raman scattering results identify presence of a-Si phase in the studied films at the relative Si content exceeding a threshold value of about 0.4. The a-Si amount correlates with the concentration of hydrogen in the films, the presence of which is detected by characteristic IR absorption bands corresponding to Si-H bending (about 660 cm-1) and stretching (a composite band in the range of about 1900-2400 cm-1) vibrations. The method of deconvolution of IR absorbance spectra in the range of about 600 to 1300 cm-1 developed earlier is used to reliably separate the IR band at about 660 cm-1. This band is identified to origin from the amorphous Si phase within the studied Si oxynitride films. This makes it possible to propose IR spectroscopy with analysis of the low-wavenumber part of the spectra as an efficient method of identifying phase composition of Si-rich Si oxynitride films. The obtained results contribute to understanding of the regularities of formation of phase compositions of PECVD grown Si oxynitride films and are useful for controlling the films properties for practical applications.
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All authors M. V. Voitovych, A. Sarikov, V. O. Yukhymchuk, V. V. Voitovych, M. O. Semenenko
Mesoscale and Nanoscale Physics
Quantum beats of exciton-polarons in CsPbI3 perovskite nanocrystals
A. V. Trifonov, M. O. Nestoklon, M.-A. Hollberg et al. (+10 more)
Exciton-
phonon interactions govern the energy level spectrum and thus the optical response in
semiconductors. In this respect, lead-halide perovskite nanocrystals represent a unique system, for which the interaction with optical
phonons is particularly strong, giving rise to a ladder of multiple
exciton states which can be optically excited with femtosecond pulses. We establish a new regime of coherent
exciton-polaron dynamics with exceptionally long coherence times (T2 ~300 ps) in an ensemble of CsPbI3 nanocrystals embedded in a glass
matrix. Using transient two-pulse
photon echo at 2 K temperature, we observe
quantum beats between the
exciton-polaron states. Within a four-level model, we directly quantify the
exciton-
phonon coupling strength through the Huang-Rhys factors of 0.05-0.1 and 0.02-0.04 for low-energy optical
phonons with energies of 3.2 and 5.1 meV, respectively. The pronounced size dependence of both coupling strengths and
phonon lifetimes offers a path to tune the optical transitions between polaron states and to tailor the coherent optical dynamics in perovskite
semiconductors for solid-state
quantum technologies.
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All authors A. V. Trifonov, M. O. Nestoklon, M.-A. Hollberg, S. Grisard, D. Kudlacik, E. V. Kolobkova, M. S. Kuznetsova, S. V. Goupalov, J. M. Kaspari, D. E. Reiter, D. R. Yakovlev, M. Bayer, I. A. Akimov
Materials Science
Unique Hierarchical Rotational Dynamics Induces Ultralow Lattice Thermal Conductivity in Cyanide-bridged Framework Materials
Zhunyun Tang, Xiaoxia Wang, Jin Li et al. (+4 more)
The pursuit of materials combining light constituent elements with ultralow
lattice thermal conductivity ($\kappa_{\mathrm{L}}$) is crucial to advancing technologies like thermoelectrics and thermal barrier coatings, yet it remains a formidable challenge to date. Herein, we achieve ultralow $\kappa_{\mathrm{L}}$ in lightweight cyanide-bridged framework materials (CFMs) through the rational integration of properties such as the hierarchical vibrations exhibited in superatomic structures and rotational dynamics exhibited in perovskites. Unique hierarchical rotation behavior leads to multiple negative peaks in Grüneisen parameters across a wide frequency range, thereby inducing pronounced negative thermal expansion and strong cubic anharmonicity in CFMs. Meanwhile, the synergistic effect between large four-
phonon scattering phase space (induced by
phonon quasi-flat bands and wide bandgaps) and strong quartic anharmonicity (associated with rotation modes) leads to
giant quartic anharmonic scattering rates in these materials. Consequently, the $\kappa_{\mathrm{L}}$ of these CFMs decreases by one to two orders of magnitude compared to the known perovskites or perovskite-like materials with equivalent average atomic masses. For instance, the Cd(CN)$_{2}$, NaB(CN)$_{4}$, LiIn(CN)$_{4}$, and AgX(CN)$_{4}$ (X = B, Al, Ga, In) exhibit ultralow room-temperature $\kappa_{\mathrm{L}}$ values ranging from 0.35 to 0.81 W/mK. This work not only establishes CFMs as a novel and rich platform for studying extreme
phonon anharmonicity, but also provides a new paradigm for achieving ultralow thermal conductivity in lightweight materials via the conscious integration of hierarchical and rotational dynamics.
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All authors Zhunyun Tang, Xiaoxia Wang, Jin Li, Chaoyu He, Mingxing Chen, Chao Tang, Tao Ouyang
Mesoscale and Nanoscale Physics
Magnetic D-brane solitons: skyrmion strings ending on a Néel wall in chiral magnets
Sven Bjarke Gudnason and Muneto Nitta
Magnetic skyrmions extended to three dimensions form string-like objects whose fundamental role remains largely unexplored. We show that skyrmion strings can terminate on a Néel-type domain wall (DW), realizing a
magnetic analogue of a Dirichlet(D)-brane
soliton. While an isolated Néel DW tends to rotate into a Bloch DW, the Néel DW is stabilized when a skyrmion string ends on it, by being transformed into a trumpet. Unlike field-theory D-branes, the Bloch-type DMI produces linear rather than logarithmic DW bending, and the strings retain finite width far from the DW, circumventing singular behavior. Furthermore, the repulsive interaction between strings allows periodic multi-junction solutions, yielding a square
lattice of alternating strings and local DW deformations as well as separating Bloch points. These results establish
magnetic skyrmion strings as fundamental strings that can end on a D-brane.
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Strongly Correlated Electrons
Bosonic Laughlin and Moore-Read states from non-Chern flat bands
Hongyu Lu and Wang Yao
The rapid advances in the study of fractional Chern
insulators (FCIs) raise a fundamental question: while initially discovered in flat Chern bands motivated by their topological equivalence to Landau levels, is single- particle band
topology actually a prerequisite for these many-body topological orders emergent at fractional fillings? Here, we numerically demonstrate bosonic FCIs in two types of non-Chern flat bands in honeycomb
lattices, using exact diagonalization and density
matrix renormalization group calculations. In a gapless flat band with a singular band touching, we observe a Laughlin state at half filling, stabilized by onsite interactions from the hard-core limit down to arbitrarily small strength. Furthermore, we report the first example of a non- Abelian FCI in a non-Chern band system: a Moore-Read state at $\nu$ = 1 filling of the same singular flat band with hard-core
bosons. Under
lattice parameters that realize a gapped trivial band (C = 0) of exact flatness, we also find the Laughlin FCI of soft-core
bosons in the isolated band limit where onsite interaction is much smaller than the band gap. In this case, the FCI forms as interacting
bosons spontaneously avoid the peaks in
quantum metric and Berry
curvature, preferentially occupying Brillouin zone region with relatively uniform
quantum geometry. Our work significantly expands the landscape for (non-)Abelian FCIs and broadens the understanding of their formation beyond the Chern band paradigm.
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Quantum Gases
Nonlinear Landau levels in the almost-bosonic anyon gas
Alireza Ataei, Ask Ellingsen, Filippa Getzner et al. (+3 more)
We consider the quantitative description of a many-particle gas of interacting abelian anyons in the plane, confined in a trapping potential. If the anyons are modeled as
bosons with a
magnetic flux attachment, and if the total
magnetic flux is small compared to the number of particles, then an average-field description becomes appropriate for the low-energy collective state of the gas. Namely, by means of a Hartree-Jastrow ansatz, we derive a two-parameter Chern-Simons-Schrödinger energy functional which extends the well-known Gross-Pitaevskii / nonlinear Schrödinger density functional theory to the
magnetic (anyonic) self-interaction. One parameter determines the total number of self-generated
magnetic flux units in the system, and the other the effective strength of
spin-orbit self-interaction. This latter interaction can be either attractive/focusing or repulsive/defocusing, and depends both on the intrinsic
spin-orbit interaction and the relative length scale of the flux profile of the anyons. Densities and energies of ground and excited states are studied analytically and numerically for a wide range of the parameters and align well with a sequence of exact nonlinear Landau levels describing Jackiw-Pi self-dual
solitons. With increasing flux, counter-rotating
vortices are formed, enhancing the stability of the gas against collapse. Apart from clarifying the relations between various different anyon models that have appeared in the literature, our analysis sheds new light on the many-anyon spectral problem, and also exemplifies a novel supersymmetry-breaking phenomenon.
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All authors Alireza Ataei, Ask Ellingsen, Filippa Getzner, Théotime Girardot, Douglas Lundholm, Dinh-Thi Nguyen
Statistical Mechanics · Cross-listed from math.PR
Jump Processes with Self-Interactions: Large Deviation Asymptotics
Amarjit Budhiraja and Francesco Coghi
We consider a pure jump process $\{X_t\}_{t\ge 0}$ with values in a finite state space $S= \{1, \ldots, d\}$ for which the jump rates at time instant $t$ depend on the occupation measure $L_t \doteq t^{-1} \int_0^t \delta_{X_s}\,ds$. Such self-interacting chains arise in many contexts within statistical physics and applied probability. Under appropriate conditions, a large deviation principle is established for the pair $(L_t, R_t)$, as $t \to \infty$, where $R_t$ is the empirical flux process associated with the jump process. We show that the rate function takes a simple form that can be viewed as a dynamical generalization of the classical Donsker and Varadhan rate function for the analogous quantities in the setting of Markov processes, in particular, unlike the Markovian case, the rate function is not convex. Since the state process is non-Markovian, different techniques are needed than in the setting of Donsker and Varadhan and our proofs rely on variational representations for functionals of Poisson random measures and
stochastic control methods.
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Soft Condensed Matter
Modeling Diffusion and Permeation Across the Stratum Corneum Lipid Barrier
Rinto Thomas, Praveen Ranganath Prabhakar, Douglas J. Tobias et al. (+1 more)
Human skin oils are a major sink for ozone in densely occupied indoor environments. Understanding how the resulting volatile and semivolatile organic oxidation products influence indoor air chemistry requires accurate representations not only of their emission into indoor air but also of their transport across the outermost skin barrier, the stratum corneum. Using molecular dynamics simulations, we investigate the passive permeation of acetone, 6-methyl-5-hepten-2-one, and water – two representative products of skin-oil oxidation and a reference compound – through a model stratum corneum lipid membrane. We determine position-dependent diffusivities using two complementary analyses based on the same set of simulations and evaluate their accuracy through a propagator analysis. The two approaches provide upper and lower bounds for the true diffusivity, which, when combined with previously reported free-energy profiles, yield permeabilities relevant for modeling macroscopic skin transport. Our results show that permeation is governed primarily by energetic barriers rather than by molecular mobility, and that the predicted transport coefficients vary by about one order of magnitude depending on the chosen diffusivity
estimator. These findings provide molecular-level constraints for parameters used in indoor air chemistry models and establish a transferable framework for linking atomistic transport mechanisms to large-scale simulations of human exposure and indoor air quality.
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All authors Rinto Thomas, Praveen Ranganath Prabhakar, Douglas J. Tobias, Michael von Domaros
Strongly Correlated Electrons
Interplay of ferromagnetism, nematicity and Fermi surface nesting in kagome flat band
Yuman He, Wentao Jiang, Siqi Wu et al. (+4 more)
Recent experiment on Fe-doped CoSn has uncovered a series of correlated phases upon hole doping of the kagome flat bands. Among the phases observed, a nematic phase with a six- to two-fold rotation
symmetry breaking is found to prevail over a wide doping and temperature range. Motivated by these observations, we investigate the interaction-driven phases realized in a kagome model with partially filled, weakly dispersing flat bands. Density-density interactions up to second-nearest neighbors are considered. We identify a close competition between
ferromagnetic and nematic phases in our self-consistent Hartree-Fock calculations: while on-site interaction favors ferromagnetism, the sizable inter-sublattice interactions stabilize nematicity over a wide doping window. Competition from translational-
symmetry-breaking phases is also considered. Overall, our results show that nematicity is a generic outcome of partially filled kagome flat bands and establish a minimal framework for understanding correlated flat-band phases.
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All authors Yuman He, Wentao Jiang, Siqi Wu, Xuzhe Ying, Berthold Jack, Xi Dai, Hoi Chun Po
Materials Science
Substitutional sulfur and its vibrational fingerprints in Sb$_2$Se$_3$
F. Herklotz, E. V. Lavrov, A. Herklotz et al. (+4 more)
The configurational behavior of sulfur in antimony triselenide (Sb$_2$Se$_3$) is investigated by combining infrared absorption spectroscopy with density functional theory. Four sulfur-related local vibrational modes are identified at 249, 273, 283, and 312~cm$^{-1}$ in melt-grown single
crystals prepared from Sb$_2$Se$_3$ granulate. Their assignment to sulfur is confirmed through controlled indiffusion experiments using Sb$_2$S$_3$ and elemental sulfur, as well as isotope-substitution studies with $^{34}$S, which produce the expected frequency shifts. Polarization-resolved measurements, together with theoretical calculations of local vibrational modes, demonstrate that the observed spectral features are fully consistent with substitutional sulfur on the three inequivalent selenium sites of Sb$_2$Se$_3$.
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All authors F. Herklotz, E. V. Lavrov, A. Herklotz, V.V. Melnikov, T. P. Shalvey, J. D. Major, and K. Durose
Mesoscale and Nanoscale Physics
Precision of an autonomous demon exploiting nonthermal resources and information
Juliette Monsel, Matteo Acciai, Didrik Palmqvist et al. (+3 more)
Quantum-dot systems serve as nanoscale heat engines exploiting thermal fluctuations to perform a useful task. Here, we investigate a multi-terminal triple-dot system, operating as a refrigerator that extracts heat from a cold electronic contact. In contrast to standard heat engines, this system exploits a nonthermal resource. This has the intriguing consequence that cooling can occur without extracting energy from the resource on average – a seemingly demonic action – while, however, requiring the resource to fluctuate. Using full counting statistics and
stochastic trajectories, we analyze the performance of the device in terms of the cooling-power precision, employing performance quantifiers motivated by the thermodynamic and kinetic uncertainty relations. We focus on two regimes with large output power, which are based on two operational principles: exploiting information on one hand and the nonthermal properties of the resource on the other. We show that these regimes significantly differ in precision. In particular, the regime exploiting the nonthermal properties of the resource can have cooling-power fluctuations that are suppressed with respect to the input fluctuations by an order of magnitude. We also substantiate the interpretation of the two different working principles by analyzing cross-correlations between input and output heat currents and information flow.
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All authors Juliette Monsel, Matteo Acciai, Didrik Palmqvist, Nicolas Chiabrando, Rafael Sánchez, Janine Splettstoesser
Mesoscale and Nanoscale Physics
The fate of disorder in twisted bilayer graphene near the magic angle
Zhe Hou, Hailong Li, Qing Yan et al. (+2 more)
In disordered
lattices, itinerant electrons typically undergo Anderson localization due to random phase interference, which suppresses their motion. By contrast, in flat-band systems where electrons are intrinsically localized owing to their vanishing group velocity, the role of disorder remains elusive. Twisted
bilayer graphene (TBG) at the magic angle $\sim 1.1^\circ$ provides a representative flat-band platform to investigate this problem. Here, we perform an atomistic tight-binding
quantum transport calculation on the interplay between disorder and flat-bands in TBG devices. This non-phenomenological approach provides direct evidence that moderate disorder enhances conductance, whereas stronger disorder restores localization, revealing a disorder-driven delocalization-to-localization transport behavior. The underlying physical mechanism is understood by an effective inter-moiré tunneling strength via spectral flow analysis of a disordered TBG cylinder. Moreover, by comparing magic-angle and large-angle TBG, we demonstrate qualitatively distinct disorder responses tied to the presence of flat-bands. Our quantitative results highlight the unconventional role of disorder in flat-band moiré materials and offer insights into the observation of the fractional
quantum anomalous
Hall effect in disordered moiré systems.
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All authors Zhe Hou, Hailong Li, Qing Yan, Yu-Hang Li, Hua Jiang
Materials Science
Orbital magnetization in Sierpinski fractals
L. L. Lage, Tarik. P. Cysne and A. Latgé
Orbital magnetization (OM) in Sierpinski carpet (SC) and triangle (ST) fractal is theoretically investigated by using Haldane model as a prototypical example. The OM calculation is performed following two distinct approaches; employing the definition and local markers formalism. Both methods coincides for all systems analyzed. For the SC, higher fractal generations create a dense set of edge states, resulting in a staircase profile, leading to oscillations in the magnetization as a function of the chemical potential. In contrast, the ST self-similarity produces distinct fractal-induced spectral gaps, which manifest as constant plateaus in the magnetization. The STs exhibit a pronounced sensitivity to edge terminations. Our results reveal how
quantum confinement in fractal structures affects the electronic orbital angular momentum, pointing to possible pathways for exploring novel orbitronics in systems with complex geometries.
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Materials Science
Contrasting properties of free carriers in $n$- and $p$-type Sb$_2$Se$_3$
F. Herklotz, E. V. Lavrov, T. D. C. Hobson et al. (+3 more)
We report persistent photoconductivity in $p$-type Sb$_2$Se$_3$ single
crystals doped with Cd or Zn, where enhanced conductivity remains for hours after illumination ceases at temperatures below $\sim$25~K. Comparative transport and infrared absorption measurements, including on $n$-type Cl-doped counterparts, reveal strong indications that hole transport in Sb$_2$Se$_3$ is more strongly affected by intrinsic carrier scattering than electron transport. These results point to a fundamental asymmetry in charge carrier dynamics and highlight the potential role of polaronic effects in limiting hole mobility in this quasi-one-dimensional
semiconductor.
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All authors F. Herklotz, E. V. Lavrov, T. D. C. Hobson, T. P. Shalvey, J. D. Major, K. Durose
Materials Science
Uniaxial Magnetic Anisotropy and Type-X/Y Current-Induced Magnetization Switching in Oblique-Angle-Deposited Ta/CoFeB/Pt and W/CoFeB/Pt Heterostructures
Amir Khan, Shalini Sharma, Tiago de Oliveira Schneider et al. (+1 more)
Planar current-induced magnetization switching (CIMS) driven by
spin-orbit torque (SOT) requires an in-plane uniaxial
magnetic anisotropy (UMA), which can be induced by oblique-angle sputter deposition of the heavy-metal underlayer in heavy-metal/ferromagnet
heterostructures. To enhance the SOT efficiency, we employ trilayer
heterostructures of (Ta or W)/CoFeB/Pt, where the CoFeB layer exhibits a UMA of 50 mT at 2 nm thickness of Ta or W. The magnetization reversal in
Hall-bar devices is detected through unidirectional
spin Hall magnetoresistance (USMR) for the type Y geometry (easy-axis transverse to current) and planar
Hall measurements for the type X geometry (easy-axis parallel to current). Both configurations exhibit CIMS with sub-microsecond current pulses, reaching switching current densities as low as $2 \times 10^{11}$ A/m$^2$ for a W (4 nm)/CoFeB (1.4 nm)/Pt (2 nm) stack with a UMA of 146 mT. Macrospin simulations reproduce the type Y switching as coherent magnetization rotation, whereas the type X devices switch at much lower currents than predicted, indicating that nucleation and domain-wall propagation dominate reversal in this geometry. Our results show that combining oblique-angle deposition with easy-axis engineering enables deterministic, field-free switching, paving the way for future low-power spintronic devices.
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All authors Amir Khan, Shalini Sharma, Tiago de Oliveira Schneider, Markus Meinert