Mesoscale and Nanoscale Physics
Electrically Tunable Valley-Based Qubits in Moiré Quantum Dots
Yasser Saleem, Pawel Potasz and Ewelina M. Hankiewicz
The search for scalable, electrically controlled
qubits remains a central challenge in
quantum technology. We introduce gate-defined moiré
quantum dots as a promising platform for valley-based
qubits. Moiré engineering resolves the central conflict of valley physics: momentum-space separation protects the states, while the enlarged moiré length scale allows smooth gates to mix them controllably. Dot geometry and confinement strength program valley hybridization, while a displacement field controls detuning, providing two noncommuting electrostatic axes for
qubit control.
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Strongly Correlated Electrons
A fractional quantum Hall factory on quantum processors: constant-depth preparation of clustered non-Abelian states
Cheng Xu, Ching Hua Lee, Hong-Hao Tu et al. (+1 more)
Non-Abelian anyons arise as exotic excitations in fractional
quantum Hall (FQH) matter and have proved very elusive to realize in conventional platforms. In this work, we show that on a programmable
quantum hardware platform, the more exotic FQH excitations are the less costly ones to prepare: clustered non-Abelian FQH states admit parallel
quantum preparation
circuits whose two-
qubit depth is independent of system size, while constructing the more common Abelian Laughlin state requires a sequential
circuit chain with linear depth. The centerpiece of this work is our new systematic framework for cataloging possible FQH states and preparing them on
quantum circuits at unprecedented scale and variety. Our prepared parafermionic Read–Rezayi $\mathbb{Z}_3$ state holds depth 3 from 8 to 118
qubits, and full root sampling extends to a 154-
qubit, 104-electron Read–Rezayi $\mathbb{Z}_4$ state. In all, our demonstrated 18-family catalog of prepared FQH states extends to all 156
qubits of an IBM Heron processor, limited only by existing hardware scale. Measurements on the prepared states recover the expected fractional quasihole charges, with the charge
estimator exact in every
symmetry-selected shot for the clustered states, and braiding data of the non-Abelian $e/4$ quasihole measured via interferometric extensions. Our work establishes a scalable route to studying FQH physics on
quantum processors and opens new avenues for preparing and probing non-Abelian topological matter far beyond the reach of conventional platforms.
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All authors Cheng Xu, Ching Hua Lee, Hong-Hao Tu, Yang Zhang
Soft Condensed Matter
Tetrahedral linkage as an intrinsic measure of glycan antifreeze behavior
Aakash Kumar, Shoumik Saha and Dilip Gersappe
Antifreeze materials prevent ice-formation by disrupting the ice-formation by binding to certain ice-planes. Cellulose, the most abundant biopolymer, has shown the ability to bind to ice-planes but the exact mechanism of this binding is far from being understood. Molecular dynamics simulations are used to investigate the hydration water of chains of cellulose-type glycans and its significance in the expression of the antifreeze behavior of sugar-derivatives found in some antifreeze materials. We find that glycans are able to prevent water from freezing near its surface by preventing their rearrangement to achieve a highly tetrahedral structure at temperatures well-below the freezing point of water. This validates our hypothesis on the role of tetrahedral coordination based on previous $\textit{ab initio}$ calculations that demonstrated cellulose prefers to bind to ice basal and prismatic planes using a tetrahedral geometry. Our findings suggest that the tetrahedral ordering of water around glycans is the key to understanding and designing cellulose-based antifreeze materials.
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Materials Science
The crossmetric tensor and the geometrical meaning of the imaginary numbers
Cyril Cayron
The product of two Cartesian quaternions can be written as a quadratic form based on a 4x4
matrix made of the symbols 1,i,j,k where i,j,k are imaginary numbers introduced by Hamilton. We generalized this
matrix to non-Cartesian bases, and showed that the
matrix is made of the metric and the cross tensors. We called it crossmetric tensor. Its symbols are s,a,b,c; they are the elementary crystallographic quaternions. We determined the crossmetric tensors for the six
crystal families. We also showed that any unit crystallographic quaternion can be geometrically represented by an infinity of pairs of oriented planes intersecting along the vectorial component of the quaternion such that the angle between them is the semiangle of the rotation. The composition of quaternions follows the intuitive source-target rule. The elementary quaternions a,b,c are geometrically represented by pair of perpendicular and oriented planes intersecting along the axis a,b,c, respectively. Other complementary quaternions noted a',b',c' were also introduced. They are the pairs of planes ma, mb, mc. The elementary quaternions a,b,c follow Hamilton rules on the squares of imaginary numbers. The complementary quaternions follow Hamilton rules on the bi and tri-products. For Cartesian basis, the quaternions i,j,k appear as a specific case of crystallographic quaternions. They are formed by the pairs of perpendicular faces of the cube mx, my, mz. Since these planes intersect along the x, y and z axis, respectively, the elementary and complementary quaternions are equal, i.e. i=i',j=j',k=k', which explains why the square, bi and tri-product Hamilton rules are satisfied all together with only three quaternions i,j,k.
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Soft Condensed Matter
It Takes Two to Tribo: Stochastic Charge Evolution in Repeated Binary Collisions of Acoustically Levitated Particles
Tom F. O'Hara, Adrian C. Barnes, Nathan Croll Dawes et al. (+1 more)
The mechanisms governing triboelectric charging between insulating particles of the same material remain an open question in nonequilibrium physics, with several competing models proposed to explain observed charging behaviour. Here, we investigate charge
evolution in a minimal system consisting of two acoustically levitated particles undergoing repeated binary collisions. To quantify particle charge transfer, purpose-built Faraday cage picoammeters were developed and calibrated. The MultiLev acoustic levitation system was used alongside Ultraino simulations to generate transducer control signals, enabling controlled collision and separation of polystyrene (PS) particles. Although individual collision events exhibit
stochastic charge transfer, described by skew-normal distributions, we demonstrate for the first time that the cumulative charge
evolution of an individual acoustically levitated particle pair follows the saturation behaviour predicted by the condenser model of triboelectric charging, with fits achieving $R^2 > 0.99$. Under identical conditions, conductive graphite-coated PS particles also undergo charge transfer, but accumulate substantially less charge, consistent with the distinct charging behaviour expected for conductive materials.
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All authors Tom F. O'Hara, Adrian C. Barnes, Nathan Croll Dawes, Karen L. Aplin
Strongly Correlated Electrons · Cross-listed from hep-th
Generalized comodule tube algebras for boundary and domain wall defects of (2+1)D topological order
Zhian Jia and Sheng Tan
The tube
algebra, which carries the structure of a $C^*$ weak
Hopf algebra, is a fundamental tool for characterizing topological excitations in topological phases. In this work, we generalize the tube
algebra framework to codimension-2 defects in $(2+1)$D gapped phases described by Turaev–Viro–Barrett–Westbury TQFTs, with particular emphasis on Levin–Wen string-net models. We show that such codimension-2 defects are described by a defect tube
algebra, which naturally carries the structure of a comodule
algebra over the weak
Hopf tube
algebra associated with the topological excitations. Boundary and domain wall defects are then characterized by the representations of the corresponding boundary and domain wall defect tube
algebras. In particular, a domain wall defect tube
algebra can be regarded as a generalized Drinfeld double of the tube
algebras associated with the two adjacent boundary defects. More generally, for a domain wall joining $N$ bulk phases, the associated domain wall defect tube
algebra can be viewed as an $N$-tuple
algebra. This perspective extends naturally to general $k$-defects, namely codimension-2 defects joining $k$ codimension-1 defects, for which the resulting generalized tube
algebra carries the structure of a multicomodule
algebra.
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Materials Science
Effective single particle picture for anharmonic lattice dynamics: a Rosetta stone for electronic and ionic response
Giovanni Caldarelli and Francesco Mauri
We establish a theoretical framework for the dynamics of a
lattice of ions in a mean-field approach, where anharmonicity is included via self-consistency. In this picture, the many-body dynamics of a system of $N$ atoms in three dimensions is mapped onto two kinds of $6N$-dimensional vectors: the
phonon condensate, describing the
evolution of the average atomic positions, and the
phonon spinors, describing the
evolution of the atomic elastic constants. The
phonon spinors are classified by a
quantum number that behaves as a
spin: the
phonon pseudospin. The many-body Liouville equation is replaced by two wave equations equivalent to the time-dependent Schrödinger equation for the electronic wave function in density functional theory. Exploiting this parallelism, we formulate the response of the anharmonic
lattice in one-to-one correspondence with time-dependent density functional theory for electrons. In complete analogy with the electronic case, we express the ionic response in terms of
matrix elements of operators representing external fields and forces. We show how anharmonicity screens external perturbations through a
phonon analogue of the Hartree-exchange-correlation kernel. We provide expressions for the
lattice optical and thermal conductivity, showing how thermal conductivity depends on the
phonon pseudospin. By approximating the density
matrix as a Gaussian, we recover the equations of the time-dependent self-consistent harmonic approximation. In this case, the linear-response equations are formulated in terms of an anharmonic kernel including three- and four-
phonon scattering. By translating anharmonic
lattice dynamics into the
language of density functional theory, this work shows how theoretical and computational advances in modeling the dynamical response of interacting electrons can be directly applied to interacting ions.
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Strongly Correlated Electrons
Direct Evidence for Robust Bulk Band Gap Across the Charge Density Wave Transition in TiSe2
Turgut Yilmaz, Anil Rajapitamahuni, Muhammad Awais Fiaz et al. (+7 more)
The mechanism driving the charge density wave (CDW) transition in TiSe2 has been debated for decades, with proposals ranging from an excitonic
insulator to a
lattice-driven instability. A central question remains whether the transition involves an opening or enhancement of the bulk band gap. Using high-resolution angle-resolved photoemission spectroscopy, we directly track the temperature
evolution of the bulk band edges across the CDW transition at TCDW = 200 K. Contrary to the expectation of a gap-opening transition, we find that the size of the fundamental band gap remains constant from the high-temperature normal phase down to 160 K. While the CDW induces clear band-folding signatures and spectral weight redistribution, the underlying band extrema are unperturbed. These results demonstrate that TiSe2 does not undergo a temperature-driven electronic gap opening. Instead, they support a scenario where the transition is governed by a
lattice symmetry-breaking reconstruction that folds, but does not gap, the electronic structure of a pre-existing band
insulator.
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All authors Turgut Yilmaz, Anil Rajapitamahuni, Muhammad Awais Fiaz, Zhenxian Liu, Jerzy T. Sadowski, Abdullah Al-Mahboob, Asish K. Kundu, Shawna M. Hollen, Boris Sinkovic, Elio Vescovo
Materials Science
HPHT growth of centimeter-sized cubic boron nitride crystals
Andrey Katrusha, Weihua Peng, Jianguo Peng et al. (+1 more)
Single
crystals of cubic boron nitride (cBN) exceeding 10 mm in size were grown by the high-pressure high-temperature (HPHT) temperature-gradient method using a Ni-Cr-based solvent catalyst. Compared with the previously reported maximum
crystal size of approximately 3 mm, this improvement was achieved by maintaining a stable precursor flux during one week of growth at a source temperature of 1950 {\deg}C. In contrast to diamonds, which were grown with the same HPHT
cell and showed nearly isometric shapes, the cBN
crystals had elongated shapes. We attribute this cBN morphology to a localized growth near the BN source due to the relatively low effective diffusivity of boron and nitrogen species in the metallic solvent.
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All authors Andrey Katrusha, Weihua Peng, Jianguo Peng, Konstantin Iakoubovskii
Statistical Mechanics · Cross-listed from quant-ph
Constructing Non-Hermitian Theories with Tunable Exceptional Points and Controlled State Purification
Soumya Kanti Pal, Rupak Majumder and Shamik Gupta
Exceptional points (EP's) are a hallmark of non-Hermitian
quantum systems. We show that momentum-space deformation provides a general design principle for creating and controlling EP's in quadratic many-body
Hamiltonians. We identify universal criteria for the momentum sectors to host EP's and the corresponding critical deformation strengths, while revealing that a single momentum-sector EP induces quite remarkably an exponential proliferation of many-body eigenvector coalescences. We further establish EP's as a universal mechanism for purifying arbitrary mixed
quantum states, uncovering distinct purification regimes and a fundamental odd-even system-size dichotomy in the thermodynamic limit. Our framework also provides a systematic reverse-engineering protocol for generating short- and long-range, reciprocal and nonreciprocal non-Hermitian
quantum matter, together with an explicit Lindblad
embedding. These results thus establish momentum-space deformation as a unified route to exceptional-point engineering and controlled design of many-body non-Hermitian
quantum systems.
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Materials Science
X-ray Thermal diffuse scattering from real-space displacement correlations
Benjamin Fahl, Jonathan Bulled, Artem Korshunov et al. (+3 more)
We introduce a method for calculating X-ray thermal diffuse scattering based on the three-dimensional difference pair distribution function (3D-dPDF). Within the harmonic approximation the method is exact, as it includes all orders of multi-
phonon scattering. A single
Fourier transform delivers the diffuse intensity over large volumes of reciprocal space. We tested the method against experimental diffuse scattering measured on a silicon single
crystal. With nothing refined beyond a scale and a background, the calculation reproduces the measured intensity to an R2 residual below 5%. Because the method uses the same pair-correlation
language as the established Yell program, thermal and static correlated disorder enter the analysis on equal footing.
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All authors Benjamin Fahl, Jonathan Bulled, Artem Korshunov, Dmitry Chernyshov, Yevheniia Kholina, Arkadiy Simonov
Soft Condensed Matter
Scaling behavior in non-reciprocal and odd conserved dynamics near criticality
Martin Kjøllesdal Johnsrud, Giulia Pisegna and Ramin Golestanian
In recent years, non-reciprocity has been explored as a ubiquitous manifestation of non-
equilibrium activity at the microscopic scales for various active matter systems, from mixtures of chemically active enzymes, colloids, and droplets, to engineered light-controlled active colloids and robotic meta-materials. A commonly used minimal model to describe the dynamics of a binary mixture of conserved species with non-reciprocal interactions is the non-reciprocal Cahn-Hilliard (NRCH) model. The model is characterized by a temperature-like tuning parameter, which can trigger phase separation, and a non-reciprocal coupling, which can lead to the formation of spatio-temporal patterns, as it represents an intrinsic source of non-
equilibrium activity and breaks parity and time-reversal
symmetries. Here, we study the scaling behavior of the NRCH model near the critical point using perturbative dynamical renormalization group techniques. We find that structural and dynamical correlations are controlled by different correlation lengths, both of which diverge at the critical point, but governed by different scaling laws. In particular, while the structural correlations are always controlled by temperature and the classical Wilson-Fisher critical exponent, the dynamical correlation length exhibits multiple scaling regimes in which either temperature or non-reciprocal coupling can dominate as the key tuning parameter, with a new critical exponent characterizing the divergence. The critical point corresponds to a conserved
equilibrium-like dynamics with odd mobility, which we denote as the odd Cahn-Hilliard (OCH) model. Our findings may have important implications on how living systems can control phase separation and spatio-temporal pattern formation using the rates of catalytic reactions, and in general metabolism, as control parameters.
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Superconductivity
Nonlinear nanoelectromechanics of a movable Cooper-pair box
S. Park, A. Patra, L. Y. Gorelik et al. (+3 more)
We theoretically study the dynamics of a movable Cooper-pair box coupled to a normal-metal pillar using a semiclassical approach. We analyze the dynamical stability induced by the nonlinear nanoelectromechanical coupling between the mechanical motion and an inelastic Andreev tunneling through linear stability and bifurcation analyses. As a function of $\eta$, defined as the ratio of electrostatic energy to Josephson coupling energy, the system exhibits reentrant stability. At small $\eta$, the fixed point loses stability through a supercritical
Hopf bifurcation, giving rise to self-sustained vibrations. With a further increase of $\eta$, a second critical point appears, at which the fixed point regains stability. We show that this second transition corresponds to an inverse subcritical
Hopf bifurcation in the adiabatic regime and to an inverse supercritical
Hopf bifurcation in the nonadiabatic regime. These results extend previous studies of adiabatic self-vibrations to the nonadiabatic regime and reveal a rich nonlinear dynamical phase diagram arising from the interplay between electronic and mechanical degrees of freedom in superconducting devices.
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All authors S. Park, A. Patra, L. Y. Gorelik, M. J. Park, H. C. Park, R. I. Shekhter
Mesoscale and Nanoscale Physics
Accessing Chern Numbers From Bloch Eigenstates Singularities
Rajesh Asapanna, Rabih El Sokhen, Paolo Aceto et al. (+7 more)
We propose two methods to extract the Chern numbers of the Bloch bands of a two dimensional
insulator, and apply them to a photonic
lattice experiment. These two methods require the knowledge of the complex-valued components of the Bloch eigenvectors, or their ratios. Unlike other
tomography methods relying on the approximate reconstruction of the Berry
curvature and its integration over the Brillouin zone, our methods boil down to the observation of phase vorticities in the eigensates structure. Those measurements, robust to experimental noise, yield exactly quantized values. One of the two methods exploits the non-normalization of the eigenmodes, making it particularly relevant for classical wave systems.
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All authors Rajesh Asapanna, Rabih El Sokhen, Paolo Aceto, Patrick Popescu-Pampu, Martin Guillot, Jacqueline Bloch, Sylvain Ravets, Clément Hainaut, Alberto Amo, Pierre Delplace
Mesoscale and Nanoscale Physics
Magnetic enhancement and Hall conductivity of excitonic insulators in a Gross–Neveu type model
William R. Tavares, Rudnei O. Ramos and Nei Lopes
We study the effects of a perpendicular
magnetic field on the excitonic
insulator (EI) phase in the
semiconductor regime using an extended planar four-
Fermi model. Within the large-$N$ approximation, we determine the coupled scalar and excitonic condensates at finite temperature, chemical potential, and
magnetic field. The field enhances the EI condensate and raises its critical temperature, providing an excitonic realization of
magnetic catalysis, while the scalar condensate remains constant throughout the EI phase. By contrast, the critical chemical potential depends nonmonotonically on the field because of the successive occupation of Landau levels. The
magnetic field also shifts the mean-field tricritical point and enlarges the first-order region of the temperature–chemical-potential phase diagram. We further analyze the
Hall conductivity and find that increasing the field reduces the number of plateaus and modifies the threshold for a finite
Hall response. For the parameters considered, the emergence of the EI condensate is accompanied by a characteristic change in the
Hall conductivity, including a field-dependent change of slope near a continuous transition. These results show that the combined phase structure and
Hall response can provide complementary signatures of excitonic ordering in planar fermionic systems.
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Materials Science
Delocalized Coupled-Cluster Theory for Polaron Structure and Dynamics
Hamlin Wu, Moritz K.A. Baumgarten, Tong Jiang et al. (+1 more)
Polaron ground states and finite-temperature dynamics remain challenging to simulate because existing methods struggle to combine nonperturbative accuracy, systematic improvability, and scalability from models to materials-specific
Hamiltonians. We introduce a translationally invariant variational coupled-cluster (CC) theory for polarons, termed delocalized CC (dCC), with closed-form energies at cost as low as $\mathcal{O}(N^3)$ and no
phonon-number cutoff. dCC accurately describes the ground states of the one- and two-dimensional Holstein and Su–Schrieffer–Heeger (optical and bond) models and the Fröhlich model, in close agreement with density
matrix renormalization group (DMRG) and diagrammatic Monte Carlo
benchmarks. A projected tangent-space response formalism built on the same ansatz yields electron-addition spectral functions and optical conductivities at zero and finite temperature. The resulting spectra agree well with DMRG, Lanczos, and neural-network
quantum-state
benchmarks while retaining a physically interpretable excitation hierarchy, and extend to two-dimensional
lattices at finite temperature beyond the practical reach of these methods. The same framework applies directly to ab initio electron–
phonon matrix elements, yielding LiF electron- and hole-polaron binding energies that match state-of-the-art many-body calculations. These results establish dCC as a unified variational framework for polaron ground states and dynamics, from model systems to real materials.
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All authors Hamlin Wu, Moritz K.A. Baumgarten, Tong Jiang, Joonho Lee
Mesoscale and Nanoscale Physics
RKKY interaction as a probe of valley-dependent spin splitting and odd-parity nature in Floquet collinear magnets
Hou-Jian Duan, Yong-Jia Wu, Xiaoliang Xiao et al. (+3 more)
Odd-parity magnets were recently proposed to emerge in collinear antiferromagnets (AFMs) via Floquet engineering, with valley-dependent
spin splitting underlying the odd-parity
spin polarization. This proposal brings about two key challenges: detecting the
spin splitting to verify the generation mechanism of these magnets, and identifying such polarization to confirm the odd-parity nature. Here, we show that the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction provides a unified
magnetic probe for both tasks. Taking collinear $f$-wave magnets as a representative example, we find that the RKKY interaction yields distinct
magnetic signals of the
spin splitting—including a magnetism reversal in the Heisenberg/Ising terms and a sign alternation of the Dzyaloshinskii-Moriya (DM) term—that enable clear discrimination of collinear $f$-wave magnets from other related AFMs. Moreover, the DM term exhibits an $f$-wave shape with odd-parity
symmetry, satisfying $J^{\alpha\beta}_{DM}(\mathbf{R}) = -J^{\alpha\beta}_{DM}(C_{2q}\mathbf{R})$ ($q=3$), which directly reflects the odd-parity
spin polarization $S_z(\mathbf{k}) = -S_z(C_{2q}\mathbf{k})$ in momentum space. This behavior persists in $p$-wave magnets ($q=1$), demonstrating the generality of our approach. Our work establishes the RKKY interaction as a versatile probe for detecting band features of collinear odd-parity magnets, with predictions accessible to existing experimental techniques such as
spin-polarized scanning tunneling spectroscopy.
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All authors Hou-Jian Duan, Yong-Jia Wu, Xiaoliang Xiao, Ming-Xun Deng, Mou Yang, Rui-Qiang Wang
Strongly Correlated Electrons
Complex field-induced magnetic phases and anisotropic magnetotransport in off-stoichiometric CeCuBi2
Vikas Chahar, Shivam Rathod, Sneh et al. (+9 more)
We report a detailed study on the structural, angle-dependent
magnetic and magnetotransport properties of highly anisotropic off-stoichiometric CeCuBi2 single
crystals. Our results reveal CeCuBi2 as an anisotropic Kondo antiferromagnet exhibiting complex field-induced
magnetic behavior and unusual magnetotransport properties.
Magnetic susceptibility and specific heat measurements reveal
antiferromagnetic (AFM) ordering below TN = 14 K with strong anisotropy and weak heavy-
fermion behavior. Electrical transport measurements show highly anisotropic resistivity and a broad hump around 47 K, indicative of Kondo-driven heavy-
fermion behavior. Magnetization measurements reveal multiple field-induced metamagnetic phases, while AC susceptibility measurements indicate slow
spin dynamics and
spin-glass-like behavior in intermediate field-induced
magnetic states. Furthermore, we observe large and strongly anisotropic magneto transport responses, including room-temperature magnetoresistance of approximately 22% at 300 K and 9 T and butterfly-like anisotropic magnetoresistance with AMR values reaching approximately 10.9%. These results highlight a strong interplay among Kondo correlations,
magnetic anisotropy, and field-tunable
spin configurations, making CeCuBi2 a possible platform for exploring correlated and anisotropic
quantum phenomena.
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All authors Vikas Chahar, Shivam Rathod, Sneh, Lipika, Shobha Singh, Balwant Singh Chauhan, Subhadeep Bej, Weida Yin, Yin-Chen Huang, Rie Y. Umetsu, Ratnamala Chatterjee, Kaustuv Manna
Materials Science · Cross-listed from cs.LG
CheMLFlow: An Open-Source Platform for Cheminformatics and Materials Informatics Applications
Brendan Smith, Susana Lopez-Moreno, Eric Dolores-Cuenca et al. (+3 more)
CheMLFlow is an open-source platform for building and executing end-to-end, high-throughput, and agentic workflows for scientific and technological applications. CheMLFlow targets a common bottleneck in scientific machine learning development, where researchers often need to assemble data acquisition, curation, representation, model training, validation, screening, interpretation, and reporting into a reproducible pipeline, even when their primary research contribution concerns only one stage. CheMLFlow provides modular workflow components, ready-to-run reference pipelines, standardized artifacts, and evaluation outputs that reduce orchestration overhead and support benchmarking across methods and
datasets. The platform is designed to be extensible, reproducible, and automation friendly, with pluggable representations and models, deterministic splits, explicit run artifacts, batch execution, and report generation. As scientific software increasingly moves toward
agent assisted experimentation, CheMLFlow's configuration driven workflows and structured outputs also provide a practical interface for coding
agents to help users construct experiments, inspect results, and summarize findings under human supervision. This article describes the system architecture, core workflows, and
benchmarks that reach literature performance for
quantum mechanical, physicochemical and bioactivity property prediction, and use cases involving time series
datasets demonstrating applications beyond molecular chemistry
datasets.
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All authors Brendan Smith, Susana Lopez-Moreno, Eric Dolores-Cuenca, Sangil Kim, Jose L. Mendoza-Cortes, Nijamudheen Abdulrahiman
Statistical Mechanics
Resolving coupled transport in space and time from molecular fluctuations in confined fluids
Thê Hoang Ngoc Minh and Ian C. Bourg
Transport in fluids is generally reduced to continuum laws parametrized by bulk coefficients and effective interfacial parameters, such as viscosities, diffusivities, slip lengths, and interfacial resistances. This description becomes incomplete at the nanoscale, where spatial heterogeneity, molecular structure, and finite relaxation times are inseparable from the transport process. Here we formulate coupled transport in nanoconfined fluids as a space–time-resolved Onsager response
matrix and extract it from
equilibrium molecular dynamics simulations. Applied to a confined charged fluid, the framework resolves the nonlocal and transient pathways coupling particle, solute, heat, and charge transport. Momentum transport appears as a long-lived, nonlocal hydrodynamic mode, whereas charge transport relaxes rapidly through localized ionic friction. Off-diagonal responses reveal distinct projected dynamics, providing a microscopic basis for nonlocal, history-dependent transport laws.
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Soft Condensed Matter
Predicting Plasticity in Two-Dimensional Foam Channel Flow Around an Obstacle
Alexandre Stepanetz, Bahaa Mazloum, Benjamin Dollet et al. (+1 more)
We study the prediction of plastic activity in the confined channel flow of two-dimensional amor- phous soft particles around a circular obstacle. Using
datasets generated with a particle-based bubble model, we formulate the prediction problem within two supervised-learning frameworks: re- gression of the non-affine displacement and binary classification of neighbor change events. A key technical challenge is that the obstacle and the confining walls explicitly break translational and rotational
symmetries. We address this issue by introducing additional structural descriptors that encode the positions of particles relative to these boundaries. Starting from simple linear models, we systematically increase the complexity of the learning framework by considering a logarithmic transformation of the target variable, the incorporation of particle-size information, the addition of
symmetry-breaking obstacle and wall descriptors, the coarse-graining of local structural descrip- tors, and nonlinear neural-network models. We find that the obstacle and wall descriptors provide the largest improvement in predictive performance. Nevertheless, the models considered here cap- ture mainly the overall localization of plastic activity near the obstacle and do not fully reproduce its detailed heterogeneous pattern in individual configurations. A perturbation analysis indicates that this heterogeneity is robustly encoded in the initial structure, suggesting that further progress requires more expressive structural representations and machine-learning architectures.
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All authors Alexandre Stepanetz, Bahaa Mazloum, Benjamin Dollet, Misaki Ozawa
Materials Science
Effects of Interfacial States and Strain on Tunnel Magnetoresistance in van der Waals Magnetic Tunnel Junctions
Sakshi Goel, Arti Kashyap, Keisuke Masuda et al. (+1 more)
All-two-dimensional
magnetic tunnel junctions promise atomically sharp interfaces, yet the role of interface-induced states in their
spin transport is not fully understood. Here, we theoretically investigate
spin-dependent transport in van der Waals
magnetic tunnel junctions of the structure Cr$_2$C/$MY_2$/Cr$_2$C ($M$ = Mo, W; $Y$ = S, Se) with barrier thicknesses of 3, 5, 7, and 9 layers. The broad features of the $\mathbf{k}_{\parallel}$-resolved conductances, namely suppression near the $\Gamma$ point and enhancement at six off-$\Gamma$ hot spots, are consistent with the decay of evanescent states in the barrier. However, trilayer WS$_2$, MoSe$_2$, and WSe$_2$ barriers exhibit conductances of the order of $e^2/h$ at $\mathbf{k}_{\parallel}$ points within the hot spots. We attribute these near-unity transmission channels to resonant coupling between the interfacial states at the two electrode–barrier interfaces, as evidenced by their weak but finite residual weight at the barrier center. For thicker barriers, this coupling weakens, which suppresses the residual weight, thereby reducing the tunnel magnetoresistance (TMR) ratio of the MoS$_2$ junction while enhancing those of the other junctions. To exploit the interfacial states for
spin-selective tunneling, we further examine biaxial tensile strain applied to the trilayer junctions. At 4% strain, the TMR ratio increases from 176% to 540% for MoS$_2$ and from 98% to 496% for WS$_2$, whereas MoSe$_2$ and WSe$_2$ exhibit comparatively weaker enhancement. Our results establish interfacial-state engineering via strain and barrier thickness as effective routes for enhancing the TMR effect in all-two-dimensional
magnetic tunnel junctions.
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All authors Sakshi Goel, Arti Kashyap, Keisuke Masuda, Terumasa Tadano
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Variational Bounds for Perceptron Learning from Structured Data
Francesco Camilli, Pierluigi Contucci, Federica Gerace et al. (+1 more)
We introduce a variational approach to a finite-temperature continuous-
spin perceptron trained on a Gaussian mixture. The model allows for a broad class of concave utilities and log-concave separable prior measures on the
spins. By combining the interpolation method with log-concavity and concentration estimates, we derive lower and upper minimax variational bounds for the limiting quenched pressure. Remarkably, the two bounds differ only in the order of optimization of two variational parameters, while all remaining extrema are controlled by the concave–convex structure of the variational potential. Whenever the two optimizations commute, the two bounds match and identify the solution of the model. The same potential yields the fixed-point equations as stationarity conditions and provides a unified route to the computation of the ground-state energy, training loss, and generalization error.
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All authors Francesco Camilli, Pierluigi Contucci, Federica Gerace, Emanuele Mingione
Mesoscale and Nanoscale Physics
Large nonlinear Hall effect in strained moiré structures hosting pseudospin-3/2 fermions
Srijata Lahiri, Gourab Paul, Bilal Tanatar et al. (+1 more)
We investigate the linear and nonlinear
Hall response of a moiré watermill
lattice, in which stacking and twisting generate a four-band
manifold near the
Fermi level with suppressed group velocities at discrete magic angles. Including an inversion
symmetry breaking onsite mass breaks the interlayer
symmetry, opening a gap in this
manifold and driving the system into a non-trivial bulk topological phase. We map the resulting phase diagram as a function of the strength of the mass and twist angle $\theta$, revealing several sectors with high Chern numbers. We then introduce strain to break the residual $C_3$
symmetry of the
lattice which activates a finite Berry
curvature dipole and correspondingly, a nonlinear
Hall response. The dipole reverses sign sharply across topological phase boundaries, producing butterfly like features when plotted against the relevant system parameters. Its magnitude substantially exceeds that reported for
symmetry-broken transition metal dichalcogenides, consistent with the elevated Wilson-loop winding and enhanced
quantum geometry associated with the
lattice's pseudospin-$3/2$ character. We conclude by incorporating thermal effects on the Berry
curvature dipole, asserting that it is an important tool for discerning
topology at low temperatures.
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All authors Srijata Lahiri, Gourab Paul, Bilal Tanatar, Saurabh Basu
Mesoscale and Nanoscale Physics
High-speed time-series prediction using compact memristor circuits with adjustable dynamics
Dániel Molnár, János Volk Jr., Tímea Nóra Török et al. (+5 more)
Ta$_2$O$_5$ nonvolatile memristors are used as compact, traceable, and well-controllable dynamic reservoir computing layers to perform time-series prediction tasks. The strongly voltage-dependent switching speed is utilized for information processing. It enables the configuration of tailorable programming and forgetting times in response to the positive and negative driving voltage pulses. Benchmarking this framework on time-series prediction problems reveals that the configurable forgetting dynamics enables a high prediction accuracy using a rather small number of memristive input channels. The training is based either on optimizing the output layer using linear regression with fixed forgetting times, or on optimizing the forgetting times as well. In the first case, six memristive channels, while in the second, only two memristive channels are used to demonstrate excellent prediction accuracy for the
benchmark tasks. This scheme allows for the tunability of the operating frequency over many orders of magnitude: by adjusting the input voltage levels, the information processing speed of the same memristive dynamic layer can be increased from the kHz to the MHz range while maintaining excellent prediction accuracy. These findings demonstrate the merits of memristor based dynamic networks in the analysis, prediction and recovery of fast temporal signals, approaching telecommunication data rates.
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All authors Dániel Molnár, János Volk Jr., Tímea Nóra Török, Zoltán Balogh, Nadia Jimenez Olalla, Miklós Csontos, Juerg Leuthold, András Halbritter
Statistical Mechanics · Cross-listed from quant-ph
Two-dimensional Toda–Arnoldi correspondence: Holomorphic Krylov geometry and counterdiabatic transport
Urei Miura
Although Arnoldi reduction of a generally non-Hermitian
Hamiltonian yields an upper Hessenberg
matrix rather than the tridiagonal form of Hermitian Lanczos theory, we show that a closed Toda sector survives in its diagonal and subdiagonal coefficients. For a fixed finite-dimensional
Hamiltonian and a cyclic state vector deformed holomorphically, the Krylov Gram determinants are $\tau$ functions of the finite two-dimensional Toda
lattice, whose Flaschka variables coincide exactly with these Arnoldi coefficients. The Toda dynamics therefore closes on this sector without determining the remaining upper Hessenberg entries. The subdiagonal part of the same sector also has a direct
geometric meaning: the squared subdiagonal coefficients determine both the Fubini–Study metric and the Berry
curvature of holomorphic Krylov subspaces, whereas the
geometric quantities associated with subspaces lost at Arnoldi breakdown cease to be defined. Along a smooth real path in the cyclic region, the Arnoldi-frame connection further provides a Hermitian tridiagonal generator of exact isospectral transport. When added to the Arnoldi
matrix, this generator cancels transitions between instantaneous eigenspaces and realizes counterdiabatic driving whenever the
matrix is diagonalizable with a nondegenerate spectrum.
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Materials Science
Structural Chirality from Short-Range Order in Heteroanionic Materials
Benjamin J. Morgan
Established routes to structural chirality in inorganic
crystals depend on
symmetry-lowering atomic displacements of an achiral parent structure. We show that chirality can instead be forced by the ordering of two anion species over the sites of an achiral parent, independent of atomic displacements. ReO$_3$-type oxyfluorides with a 2:1 anion stoichiometry, such as NbO$_2$F, exhibit two ordering patterns: cis octahedral coordination and period-three anion-chain ordering, both rooted in the off-centring of $d^0$ cations. By direct enumeration, we prove that every configuration combining both orderings on the smallest commensurate
cell is
chiral, belonging to a Sohncke space group. For the specific case of NbO$_2$F, density-functional theory calculations predict that the ground state is the maximally symmetric
chiral configuration. Wang-Landau Monte Carlo simulations of a DFT-trained cluster-expansion model predict an
equilibrium chiral phase up to a first-order transition at 494 K. These results establish configurational ordering as a chemically realisable route to structural chirality, and mark heteroanionic materials with analogous ordering chemistry as candidates for a new class of
chiral functional materials.
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Statistical Mechanics · Cross-listed from physics.flu-dyn
Laminar gaps mirror turbulent puffs in pipe flow
Shai Kapon, Tobias Grafke and Anna Frishman
Pipe flow at intermediate Reynolds numbers, between the laminar and fully turbulent regimes, takes the form of several spatially and temporally intermittent phases in which turbulent and laminar states coexist. In the lower range, $Re\in (1750,2300)$,
turbulence appears in the form of localized traveling structures called "puffs", which form long-lived chaotic dynamical states, whose
stochastic decays and splits control the steady state intermittency. At the other end, $Re\in (2300,3000)$, puffs are replaced by an extended turbulent state, with laminar pockets intermittently forming and disappearing within it. Using direct numerical simulations of pipe flow at $Re = 2400, 2450, 2500, 2550$, we provide evidence that these laminar gaps form a distinct dynamical state analogous to puffs: a traveling laminar pocket in a turbulent surrounding, stabilized by a shear-dependent self-tuning mechanism. We analyse the mean spatial profile of these gaps and show that their lifetimes are exponentially distributed, suggesting that gap closing corresponds to an escape from a chaotic saddle. Finally, we suggest these laminar gaps become unstable and disappear at a finite Reynolds number, $Re\sim 2900$, which can be interpreted as the onset point of spatially and temporally homogeneous
turbulence.
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Strongly Correlated Electrons
Ghost-RISB for Correlated Electron-Phonon Systems: Application to the Hubbard-Holstein Model
Samuele Giuli, Ricardo J. Campos-Lopes, Emin Moghadas et al. (+1 more)
We develop a generalization of the ghost-rotationally-invariant slave-
boson (ghost-RISB) method that incorporates local
phonon modes coupled to arbitrary on-site electronic degrees of freedom, enabling a nonperturbative treatment of electron-electron and electron-
phonon interactions within an efficient variational framework. The method extends the ghost-orbital construction to capture dynamical self-energy effects and
phonon-induced renormalizations beyond static slave-
boson approaches. Benchmarking against dynamical mean-field theory (DMFT) results for the Hubbard-Holstein model, we find excellent quantitative agreement for electron quasiparticle weights and
phonon properties across a wide range of coupling strengths, and it captures accurately the competition between electron-electron and electron-
phonon interactions. We show that the inclusion of the ghost orbitals is crucial to accurately describe the regime of low-frequency, strongly dynamical,
phonons. The extended ghost-RISB achieves this accuracy at a fraction of the computational cost of DMFT, due to its self-consistency rooted in static observables instead of dynamical ones, enabling rapid exploration of correlated electron-
phonon phase diagrams. We exploit this advantage to characterize the most demanding regime of strong coupling and adiabatic
phonons. Our analysis shows a suppression of the superconducting order parameter, which is interpreted as a Franck-Condon-like reduction of the overlap between the
phonon wavefunctions associated with empty and doubly-occupied sites in the bipolaronic regime.
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All authors Samuele Giuli, Ricardo J. Campos-Lopes, Emin Moghadas, Massimo Capone
Materials Science
Growth and characterization of GaN/Ga2O3 Nanowire Heterostructures for Ultraviolet Optoelectronics
Edgars Butanovs, Eriks Dipans, Martins Zubkins et al. (+10 more)
Ultraviolet-range GaN/b-Ga2O3
heterostructures were fabricated and investigated in both planar and nanowire geometries using pulsed
laser deposition and reactive magnetron sputtering from a
liquid gallium target for b-Ga2O3 deposition, while both GaN nanowire arrays and planar p-type Mg-doped GaN layers were grown by metal-organic chemical vapor deposition. Precise control of film uniformity and thickness was achieved as confirmed by structural and morphology studies using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. Planar n-Ga2O3/p-GaN heterojunction diodes were electrically and photoelectronically characterized, exhibiting pronounced rectifying behavior, high forward current and a visible-blind ultraviolet photoresponse under zero external bias, demonstrating intrinsic self-powered operation. Furthermore, GaN/b-Ga2O3 core/shell nanowire
heterostructures were developed and systematically studied with a focus on morphology control and process optimization. The influence of deposition parameters on shell thickness, uniformity, and tapering was investigated, enabling improved conformality of the b-Ga2O3 coating on the M-plane facets of GaN nanowires. The results highlight the viability of physical vapor deposition techniques for forming GaN/b-Ga2O3
heterostructures and establish a pathway toward nanowire-based ultraviolet optoelectronic devices.
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All authors Edgars Butanovs, Eriks Dipans, Martins Zubkins, Edvards Strods, Anatolijs Sarakovskis, Juris Purans, Ashutosh Kumar, Sergiy Khartsev, Martin Berg, Anders Hallen, Qin Wang, Joseph le Pluart, Peter Ramvall