Superconductivity
Bridging ambient- and high-pressure superconductivity in La$_2$LnNi$_2$O$_7$ films
Motoki Osada, Chieko Terakura, Shusaku Imajo et al. (+9 more)
The discovery of high critical-temperature $T_{\mathrm{c}}$ superconductivity near 80 K in
bilayer nickelates under high pressure has sparked extensive studies. While superconductivity exceeding 40 K was subsequently discovered at ambient pressure in compressively strained films, the relationship between ambient- and high-pressure regimes remains an open question. Here we present a systematic investigation of superconductivity in compressively strained La$_2$LnNi$_2$O$_7$ films (Ln = lanthanides) at ambient and high pressures. The normal-state resistivity at ambient pressure, revealed by suppressing superconductivity with
magnetic fields of 59 T, tends toward $T^2$ behaviour. Under high pressure in a cubic-anvil
cell, $T_{\mathrm{c}}$ was enhanced from 41-42 K at ambient pressure to 67-73 K at 16 GPa. On the other hand,
lattice compression induced by Ln substitution, which may mimic effects of pressure, lowers $T_{\mathrm{c}}$. In both cases, $T_{\mathrm{c}}$ correlates with the
evolution of normal-state transport between $T^2$ and $T$-linear behaviour, offering insight into the interplay between
lattice structure and superconductivity in
bilayer nickelates.
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All authors Motoki Osada, Chieko Terakura, Shusaku Imajo, Jean-Baptiste Morée, Akiko Kikkawa, Masamichi Nakajima, Hsiao-Yi Chen, Yusuke Nomura, Koichi Kindo, Ryotaro Arita, Yoshinori Tokura, Atsushi Tsukazaki
Materials Science
Active learning molecular beam epitaxy of complex quantum materials
Raghutheja Bollampally, Soumya Sankar, Yuqi Qin et al. (+1 more)
The integration of machine learning (ML) into materials science offers a transformative pathway toward fully autonomous synthesis workflows. For precise thin-film deposition techniques like molecular beam epitaxy (MBE), this automation is critical to overcome the time-consuming, manual
navigation of high-dimensional thermodynamic phase spaces. Existing approaches for ML-assisted thin film growth predominantly rely on continuous
Bayesian optimization (BO) models that assume smooth parameter landscapes. Consequently, they struggle to capture the abrupt crystallographic phase boundaries and narrow growth windows inherent to binary
quantum materials. Here, we demonstrate an active learning protocol based on Sequential Model-Based Optimization (SMBO) designed specifically for the closed-loop MBE of such compounds. To overcome the limitations of continuous models while retaining the efficient exploration-exploitation logic of traditional BO, we combine a random forest surrogate model capable of capturing highly non-linear phase transitions and thermodynamics constraints of the growth process with an expected improvement function to predict optimum growth parameters. We apply this combined SMBO framework to the MBE of the topological Weyl ferromagnet Fe$_3$Sn, which exists as a metastable line compound. Using a small initial training set of fewer than twenty growth iterations, our active learning loop rapidly navigates a complex optimization landscape to identify an optimum growth window bounded by sharp transitions. Within only four active learning iterations, the absolute predictive error is halved to $\approx10\%$. This data-efficient framework paves the way for the autonomous discovery and thin-film synthesis of functional
quantum materials.
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All authors Raghutheja Bollampally, Soumya Sankar, Yuqi Qin, Berthold Jäck
Materials Science
Vacancy-Driven Electronic Reconstruction in Monolayer PtSe$_2$: Formation Thermodynamics and Charge States
Xiwen Gai, Jingang Wang and Tianxing Ma
Layered transition metal dichalcogenides are an important platform for two-dimensional materials, where the inevitable intrinsic defects provide new degrees of freedom for tuning their physical properties. Based on first-principles calculations, this work systematically investigates the formation energies, charge states, and electronic structural characteristics of V$_{\mathrm{Pt}}$, V$_{\mathrm{Se}}$, and composite vacancies in monolayer PtSe$_2$. The results indicate that while vacancy formation energies are highly sensitive to chemical potentials, the V$_{\mathrm{Se}}$ structure consistently exhibits the lowest formation energy. The charge defect calculation reveals the stable charge state intervals of V$_{\mathrm{Se}}$ and V$_{\mathrm{Pt}}$ as a function of the
Fermi level, thus describing the
evolution of the charge states of intrinsic vacancies at different electronic chemical potentials. Climbing Image Nudged Elastic Band calculations reveal high migration barriers for V$_{\mathrm{Se}}$ and V$_{\mathrm{Pt}}$, indicating strongly hindered vacancy
diffusion at room temperature, while short Ab Initio Molecular Dynamics simulations confirm the absence of immediate structural collapse within the simulated time window. Optical property calculations indicate that point defects significantly alter the dielectric response of monolayer PtSe$_2$ and generate new low-energy absorption channels associated with in-gap defect states. These findings provide new insights into defect-mediated electronic and optical property modulation in monolayer PtSe$_2$, offering guidance for its potential device design.
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Materials Science
Atomistic Structure Generation and Neural-Network Screening of Hard Carbons to Identify High-Capacity Sodium Storage
Harry Mclean, Aiden Daniel Emery, Theodore Thomas Walton et al. (+2 more)
Hard carbons are established anodes for lithium-ion batteries and leading candidates for sodium-ion batteries, yet their electrochemical performance is governed by a heterogeneous network of graphitic domains, defects, and nanopores that conventional atomistic methods cannot model at the required length scales. We combine universal machine-learned interatomic potentials with the RAFFLE structure-generation framework to construct 13,096 realistic hard carbon models containing up to 4,378 atoms, matching experimentally measured densities, porosities, and sp$^2$/sp$^3$ bonding fractions. Explicit sodium intercalation of representative structures reproduces the characteristic sloping-to-plateau voltage profiles, revealing that capacity increases with decreasing carbon density and increasing porosity. To screen the full library, we train a lightweight neural-network surrogate that predicts capacity directly from the host using frozen universal-potential descriptors augmented by
geometric void features. The surrogate identifies high-capacity candidates exceeding 800 mAh g$^{-1}$, which are validated by full intercalation calculations. This scalable framework links hard carbon microstructure to sodium-storage performance and provides atomistic design principles for high-capacity anodes. More broadly, the workflow enables systematic exploration of synthesis-dependent amorphous microstructures, including precursor chemistry, pyrolysis, heteroatom doping, and pore engineering, providing a route toward atomistically informed hard carbon design.
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All authors Harry Mclean, Aiden Daniel Emery, Theodore Thomas Walton, Ned Thaddeus Taylor, Steven Paul Hepplestone
Soft Condensed Matter
Hydrodynamic Mode Coupling: Effects of density variations in nanoscale channel flows
L. Heitmeier and J. S. Hansen
We apply a modal framework for investigating the effect of density variations on
gravity-type driven flows at the nanoscale. Using eigenfunction decomposition of the density and acceleration fields, each shear-pressure mode is separated into a homogeneous contribution and an inhomogeneous contribution determined by the
Fourier amplitudes of the density and applied acceleration. This decomposition provides a direct means of identifying how density variations and external forcing couple and govern the flow behavior. We first revisit the Poiseuille flow and show that for channel heights larger than the characteristic intermolecular distance the homogeneous contribution dominates the long wave length (small wave vector) response, consistent with previous simulation results. In contrast, for sinusoidally driven flow, selective excitation of acceleration modes can produce the opposite behavior, with the inhomogeneous contribution dominating the long wave length response. The results show that the effect of the density variations depends on the specific flow; specifically the detailed mode coupling between the acceleration and density fields. The framework presented here provides a direct systematic approach for understanding and predicting the flow depending on the applied acceleration.
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Statistical Mechanics · Cross-listed from physics.bio-ph
An information-theoretic perspective on feed-forward loop abundances in transcriptional networks
Mintu Nandi, Sudip Chattopadhyay and Suman K Banik
In the transcriptional networks of Escherichia coli and Saccharomyces cerevisiae, the eight feed-forward loop (FFL) motifs occur at markedly different frequencies. Although previous studies have linked the abundant C1- and I1-FFLs to specific dynamical functions, a common account of the broader pattern is lacking. To address this gap, we adopt an information-theoretic approach. An FFL transmits information through two paths that share an input and converge on an output, suggesting that their interaction may contribute to differences among motifs. To investigate this, we decompose input-output mutual information (MI) into pathway MI and interference MI (IMI). Here, the pathway MI collects the contributions of individual pathways, whereas IMI identifies the contribution that arises from their interference. We find that within a representative parameter regime, IMI values of FFLs produce a hierarchy that closely resembles the abundance ordering in E. coli, whereas total and pathway MIs do not. Motivated by this observation, we perform constrained optimization that identifies parameter regimes compatible with abundance-like targets for both S. cerevisiae and E. coli. We relate the optimized IMI hierarchy to pathway interference strength and local pathway sensitivities to understand the underlying biophysical origin. Our framework thus probes the correspondence between pathway interference, information transmission, and motif-abundance hierarchies.
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Soft Condensed Matter
Effect of Convection Rolls in Motility-Induced Phase Separation of Active Janus Particles
Poulami Bag
We numerically study motility-induced phase separation of active particles in two-dimensional convection rolls. We analyse local packing-fraction distributions, density fluctuations, the corresponding phase diagrams, and diffusivity curves to characterise the interplay between self-propulsion, global packing fraction, and advection strength. In the weak-flow regime, the system exhibits phase separation characterised by bimodal density distributions, slowly decaying density fluctuations, and a sharp reduction in diffusivity. Increasing advection suppresses clustering by enhancing particle transport and reducing trapping, leading to a shift in the critical self-propulsion velocity for motility-induced phase separation and a shrinkage of the spinodal region. Beyond the intuitive suppression of clustering by weak-flow advection, our results reveal several non-trivial phenomena including a reentrant phase behaviour where extremely high self-propulsion hinders motility-induced phase separation by facilitating particle escape from dense regions. We also observe that the density distributions strongly depend on roll periodicity. These findings demonstrate that convection rolls provide an effective means to control non-
equilibrium collective behaviour in active matter.
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Mesoscale and Nanoscale Physics
Robust stabilization of high-frequency magnetic droplets in W-CoFeB-MgO nanoconstriction spin Hall nano-oscillators
Hind Prakash, Arunima TM, Roman Khymyn et al. (+1 more)
Magnetic droplets are highly nonlinear
spin-wave
solitons that can be excited in nanoscale spintronic devices with strong perpendicular
magnetic anisotropy. Although extensively studied in nanocontact-based
spin-torque oscillators, their stabilization in pure
spin current-driven devices such as
spin Hall nano-oscillators (SHNOs) has remained elusive. Here, we micromagnetically demonstrate the robust stabilization of non-propagating high-frequency droplets in CMOS-compatible W/CoFeB/MgO nanoconstriction SHNOs under oblique
magnetic fields. While the constriction geometry gives rise to noncircular droplet shapes in an inhomogeneous effective field landscape, stable droplet modes exhibiting complete core magnetization reversal and pronounced hysteresis are observed. At lower current densities, droplets display breathing oscillations with periodic expansion and contraction, whereas higher drive currents lead to drift, deformation, and the emergence of sidebands around the fundamental frequency. Tuning the strength and orientation of the applied
magnetic field alters the effective field landscape, allowing droplets to escape confinement and propagate over distances exceeding 2$\mu$m.
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All authors Hind Prakash, Arunima TM, Roman Khymyn, Himanshu Fulara
Quantum Gases
Dispersive Shock Waves in a 1D Quantum Liquid
Philipp Schüttelkopf, Mohammadamin Tajik, Federica Cataldini et al. (+8 more)
We implement a moving boundary condition in a 1D
quantum liquid to study nonlinear wave breaking and its regularization by dispersion. Programmable optical potentials allow us to compress a weakly interacting ultra-cold Bose gas trapped on an atomchip at tunable speeds of up to three times the speed of sound and we subsequently measure the quasi-in-situ density distribution to extract the shock wave edge dynamics. We resolve both leading and trailing edge velocities and observe a shock wave width that increases linearly in time, which are distinguishing features of dispersive shock waves, consistent with asymptotic predictions using Whitham's method. Quantitative agreement is found with finite temperature non-
polynomial Schrödinger equation simulations, taking into account the imaging process and the finite height of the piston potential. Our results constitute a controlled, quantitative test of dispersive shock dynamics in a 1D
quantum fluid and demonstrate that the coarse-grained dispersive-shock phenomenology remains robust even as the microscopic dynamics depart from the strictly integrable 1D regime.
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All authors Philipp Schüttelkopf, Mohammadamin Tajik, Federica Cataldini, Si-Cong Ji, Igor Mazets, Sebastian Erne, Nataliia Bazhan, Mojtaba Alyannezhadi, Mostafa Alyannezhadi, Jörg Schmiedmayer, Frederik Møller
Disordered Systems and Neural Networks
Long-range Nonlinear Sigma Model for a Singular Quantum Kicked Rotor
Weitao Chen and Yunxiang Liao
Singular kicked rotors have long been compared with power-law random banded
matrices (PRBM) because their momentum-space Floquet
matrix elements decay algebraically. However, it has remained unclear whether the deterministic correlations of the rotor become irrelevant at long distances and, consequently, under what conditions the two systems share the same infrared theory. To address this question, we derive a nonlocal supersymmetric nonlinear sigma model directly from a
quantum kicked rotor with a power-law or logarithmic singularity. By carrying out the renormalization-group analysis up to two-loop order, we show that, after matching the
symmetry class and coupling convention, the rotor reproduces the long-range Anderson transition of the corresponding PRBM, including its localized, critical, and extended infrared regimes.
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Other Condensed Matter
Wavelength-Resolved Control of Photovoltaic Screening and Defect-Mediated Doping in Photo-Ferroelectric/Graphene Devices
Krishna Prasad Maity, Mohd Uvais, Jean-Francois Dayen et al. (+3 more)
Ferroelectrics enable large charge doping of two-dimensional overlayers, but the coexistence of switching and nonswitching charge dynamics complicate electro-optical analysis. Here, we investigate the optoelectronic response of a ferroelectric/
graphene device under 365 and 530 nm illumination, disentangling effects on ferroelectric dipole
alignment from extrinsic current pathways.
Graphene acts as a high-gain sensor, amplifying subtle polarization dynamics into a pronounced resistance difference. By resolving switching and nonswitching channels in dark and illuminated conditions, we reveal a competition between photovoltaic charge screening and defect-assisted excitation that governs device electrostatics. Above-band gap illumination generates free carriers that induce leaky ferroelectric hysteresis and suppress the
graphene resistance ratio between opposite remanent polarization states from 290% to 15% due to dynamic photovoltaic charge screening. In contrast, 530 nm illumination primarily induces charge redistribution in ferroelectrics via defect-state excitation, leading to a significantly weaker suppression of the resistance variation of
graphene. These results establish practical guidelines for selecting
photon energy and intensity to either preserve remanent polarization while tuning channel doping or deliberately reconfigure polarization through optical programming.
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All authors Krishna Prasad Maity, Mohd Uvais, Jean-Francois Dayen, Bernard Doudin, Roman Gumeniuk, Bohdan Kundys
Strongly Correlated Electrons
Gauge-constrained Spinon Complexes Near Deconfined Quantum Criticality
Zhi-Yao Ning, Xue-Feng Zhang, Naoki Kawashima et al. (+1 more)
Quantum magnets provide a microscopic platform for studying confinement and gauge-constrained structures mediated by emergent gauge fields. We investigate confined spinon complexes in the columnar valence-bond-solid (VBS) phase near deconfined
quantum criticality using pinned-
spin defects and
quantum Monte Carlo simulations. The pinned
spins act as static spinon sources with controlled positions,
spin projections, and VBS vorticities, enabling measurement of defect energies and direct real-space visualization of the associated VBS domain-wall strings. For matched spinon-antispinon sources, the excitation energy saturates beyond a characteristic separation as one extended dipole reorganizes into two shorter neutral dipoles, providing energetic and real-space evidence of string breaking. We further show that domain-wall connectivity is governed by
lattice-scale VBS phase offsets in addition to vorticity and
spin-projection neutrality. Compatible multi-pin patterns generate connected four-spinon complexes and extended domain-wall networks that retain their global connectivity under local distortions. These results establish pinned-
spin defects as a controlled tool for assembling and resolving multi-spinon structures and their confining strings in a VBS phase.
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All authors Zhi-Yao Ning, Xue-Feng Zhang, Naoki Kawashima, Jun Takahashi
Materials Science
Quantized Spin Hall Effect in Three-Dimensional Nodal-Ring Semimetal: Geometric Scaling and Symmetry-Engineered Spin Response
Jiali Chen, Chaoxi Cui, Zhi-Ming Yu et al. (+2 more)
The anomalous
Hall conductivity in
magnetic Weyl semimetals scales linearly with the momentum separation between Weyl nodes, establishing a
geometric paradigm for three-dimensional
Hall responses. Here we discover an analogous phenomenon in the
spin Hall effect: a quantized
spin Hall conductivity (SHC) in nodal-ring semimetals that scales linearly with the nodal-ring radius $R$. From an ideal model with a single nodal ring, we derive analytically that the SHC inside the
spin-orbit-coupled gap obeys $\sigma_{\alpha \beta}^{S, 3D}=\sigma_0^{S,2D} \cdot (\pi R/2 \pi)$, where $\sigma_0^{S,2D}=(e^2/h) \cdot (\hbar/2 e)$ is the two-dimensional
quantum spin Hall conductance. Crucially, the
symmetry of the
spin-orbit coupling acts as an independent switch: Rashba coupling generates purely conventional SHC components, while Weyl coupling additionally activates unconventional ones, providing separate control over response magnitude and tensor
symmetry. We validate this principle in yttrium nitride, where strain tunes $R$ and
symmetry breaking toggles between response types. Our work establishes a new paradigm for engineering quantized
geometric responses in three dimensions, opening pathways to tailored
spin-orbit functionalities.
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All authors Jiali Chen, Chaoxi Cui, Zhi-Ming Yu, Wei Jiang, Yugui Yao
Mesoscale and Nanoscale Physics · Cross-listed from hep-ph
Anomaly-Induced Phenomena with Massive Fermions: Higher-Landau-Level Dominance from Spatially Modulated Electric Fields
Koichi Hattori, Kazuya Mameda, Takeru Uchiyama et al. (+1 more)
We investigate the axial Ward identity for massive
fermions under a constant
magnetic field at arbitrary strength, maintaining an arbitrary spacetime configuration of a perturbative electric field. We show that a spatially modulated electric field prevents the exact cancellation between the anomaly and pseudoscalar terms, generating a local axial-charge source even in the adiabatic regime where the frequency is subthreshold to massive-
fermion production. Remarkably, unlike conventional
magnetic responses, this charge generation is dominated not by the contribution of the lowest Landau level, but by those of the higher Landau levels. Our findings provide a microscopic foundation for anomaly-induced transport and anomalous optical responses in gapped systems. In particular, we find that the spatially modulated
chiral magnetic effect in weakly gapped Weyl semimetals that exhibits a linear suppression of the magneto-resistance by the
magnetic-field strength instead of the renowned quadratic suppression.
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All authors Koichi Hattori, Kazuya Mameda, Takeru Uchiyama, Di-Lun Yang
Materials Science
Chiral Spinterfaces as an Overlooked Component of the Chiral-Induced Spin Selectivity Effect
Franziska Schölzel, Aybüke Gülkaya, Rico Ehrler et al. (+11 more)
The
chiral-induced
spin selectivity (CISS) effect is generally attributed to
spin-selective transport through
chiral molecules, while the role of the molecule-electrode interface remains largely unexplored. Here, we show that adsorption of
chiral amino acid derived molecules on
ferromagnetic Ni thin films generates a remanent chirality-dependent magneto-optical response that is localized to the molecule-Ni/NiO interface and can be reversibly switched by an external
magnetic field, demonstrating its genuine
magnetic character. A comprehensive series of control experiments establishes that the response originates from the interfacial region rather than from the molecular layer or the bulk ferromagnet. First-principles calculations reveal that Boc-methionine adsorption proceeds through energetically accessible sulfur- and carboxyl-bound configurations that produce distinct molecular orientations and ligand-p/Ni-d hybridization, thereby defining structurally and electronically distinct interfaces. Together, the experimental and theoretical results support the formation of
chiral spinterfaces, identifying the molecule-ferromagnet interface as an active and previously overlooked component of CISS systems. These findings broaden the microscopic picture of CISS beyond the
chiral molecule itself and reveals interface electronic structure as a key design parameter for
spin-selective molecular devices.
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All authors Franziska Schölzel, Aybüke Gülkaya, Rico Ehrler, Dominik Hornig, Lokesh Rasabathina, Aleksandra Lindner, Jürgen Lindner, Aleksandr Kazimir, Christina Lamers, Dietrich R.T. Zahn, Michael Mehring, Olav Hellwig, Shuxia Tao, Georgeta Salvan
Quantum Gases
KPZ scaling in one-dimensional arrays of photon condensates
Michiel Yzewyn and Michiel Wouters
Bose-Einstein condensates of
photons in dye filled microcavities are known to feature many properties of the ideal bose gas at thermal
equilibrium. Nevertheless, the finite
photon life time renders them driven dissipative systems where losses are balanced by continuous driving by a pump
laser. We show here with simulations based on a classical field model that their driven-dissipative nature causes their first order coherence to feature Kardar-Parisi-Zhang (KPZ) scaling, a phenomenon well known in the related condensates of
exciton-polaritons. Remarkably, we find that the KPZ scaling even occurs in a regime with large density fluctuations. We discuss the modification of the scaling by the occupation of excited states and how to recover the universal scaling behavior by spectral filtering.
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Statistical Mechanics · Cross-listed from physics.pop-ph
Entropy and Frenesy: the arrow and the bustle of time
Christian Maes
Nonequilibrium statistical mechanics is the science of time as it manifests itself in the transient or steady
entropy producing dynamical condition of many-body systems. Beyond the vivid multiformity of the phenomena themselves, three foundational issues lie at its heart. The first question concerns the very origin of
entropy production, which gives macroscopic processes their direction and thereby defines the arrow of time: how does an atomistic mechanical world give rise to dissipated heat, thermalization, and time-reversal
symmetry breaking? The second asks why, far beyond the familiar behavior of
equilibrium systems, driving or agitation may produce and select stable and functionally rich structures: what is it about far-from-
equilibrium, low-
entropy driving that unleashes the wealth and intricacy of the natural world? The third issue is partly methodological: to determine how, and for which subclass of such wildly diverse nonequilibrium systems, a systematic, unified description and modeling from first principles remains possible. This essay addresses these issues in an informal, semi-popular-science style, offering a personally engaging yet wide-ranging introduction to the complementary roles of
entropy production and the less familiar, more recently coined notion of frenesy in the dynamical fluctuations of steadily driven systems. Together, we argue, they provide a more complete starting point for understanding physical time on mesoscopic to macroscopic scales.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Automating Variational Quantum Sensing through Reinforcement-Learned Circuit Structures
Jie Liu and Xin Wang
Variational
quantum sensing offers a promising route to high-precision parameter estimation, but its performance depends strongly on the
circuit architectures used for probe preparation and measurement. Existing approaches typically optimize continuous parameters within predefined ansätze, restricting the accessible design space and limiting adaptation to sensing tasks and hardware constraints. Here, we introduce AutoQSense, a reinforcement-learning framework that searches
circuit architectures using Fisher-information-based objectives. For few-
qubit systems, a single
agent sequentially constructs preparation and measurement
circuits. For larger systems, a distributed formulation assigns local
circuit design to subsystem
agents and inter-block
entanglement to a budgeted
agent. Numerical results show that the learned architectures recover known
benchmark strategies, adapt to dephasing noise, and outperform fixed hardware-efficient ansätze while using fewer entangling gates. These results establish AutoQSense as a resource-aware approach to adaptive and hardware-compatible
quantum sensing.
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Soft Condensed Matter · Cross-listed from physics.flu-dyn
Modelling flow-driven pore closure of weakening poroelastic media
Matthew V. Ghosh, Matthew G. Hennessy, Andreas Münch et al. (+1 more)
Poroelastic materials, such as
polymer tissue scaffolds, porous rocks, and hydrogels, can weaken due to interactions between the solid skeleton and chemical species in the interstitial fluid. We develop a mathematical model for a poroelastic material to provide fundamental mechanistic insight into how weakening the material can affect the time-varying mechanics of the system. Our model couples large-deformation poroelasticity with an advection-
diffusion equation for the solute. Furthermore, we introduce a decay equation for the material stiffness, whose rate of decay depends on the solute concentration. In this way, we describe a three-way coupling between poroelastic deformation, weakening of the skeleton and transport of solute through the material. We exploit numerical and analytical techniques to reveal the flow-driven uniaxial compression of a weakening poroelastic material and determine parameter regimes for which weakening the material facilitates pore closure at the downstream boundary. We identify parameter regimes in which (1) a steady state is attained without pore closure, (2) pore closure occurs at a finite time or (3) the pores close instantaneously; we uncover case (2) through the introduction of weakening into the system. We provide insights into the relationship between the differing behaviours and the separation between the timescales of the system. For systems with slow weakening, we derive a leading-order approximation for the time of pore closure, treating the ratio of the timescales of poroelastic relaxation and weakening as a small parameter, and investigate the accuracy of this approximation and the new behaviours that arise when these timescales become comparable.
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All authors Matthew V. Ghosh, Matthew G. Hennessy, Andreas Münch, Sarah L. Waters
Strongly Correlated Electrons
Inducing metal-insulator transition via disorder in correlated kagome systems
Qingzhuo Duan, Hongdao Zhuge, Zixuan JIa et al. (+1 more)
The metal-
insulator transition is often accompanied by fascinating
quantum phenomena, including superconducting domes,
antiferromagnetic phase transitions, and
quantum spin liquids. Concurrently, kagome materials are predominantly metallic, necessitating the realization of insulating states to fully exploit their significant potential in logic and optoelectronic device applications. To address this, we investigate the electronic transport and
magnetic properties in correlated kagome systems with hopping disorder using the determinant
quantum Monte Carlo method. Through comprehensive analysis of the kinetic energy, dc conductivity, and density of states at the
Fermi level, we demonstrate that the cooperative interplay between hopping disorder and electron correlations promotes electron localization. Within the
insulator, an increase in the disorder level reduces the Coulomb interaction required for the Mott transition. Additionally, while disorder partially suppresses
antiferromagnetic ordering, it remains insufficient to induce a complete
magnetic transition. Finally, we summarize two schematic regions distinguishing between
antiferromagnetic metal, correlated Anderson
insulator, and disordered Mott
insulator. Our study advances the understanding of metal-
insulator transition in kagome systems by disorder and provides actionable insights for experimental control of these transitions.
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All authors Qingzhuo Duan, Hongdao Zhuge, Zixuan JIa, Tianxing Ma
Materials Science
Multiple topological electronic and phononic quasiparticle excitations in hexagonal TTe (T=Hf, Zr & Ti) crystals
Prakash Pandey and Sudhir K. Pandey
The exploration of topological
fermions and
bosons marks a new chapter in condensed matter physics, unveiling rich and unconventional phenomena. Particularly in
quantum field theory, exotic quasiparticle excitations such as Dirac and Weyl
fermions can serve as direct analogs, and their recent experimental realizations have sparked significant interest in these topological quasiparticles. Although there are various reports on the coexistence of unconventional fermionic quasiparticles such as
spin-1/2 (type-I, type-II, & type-III),
spin-1 (threefold degeneracy), nodal line (type-I, type-II, & type-III) and others, reports on the simultaneous presence of such quasiparticles in both electronic and phononic spectra within a single material remain extremely limited. Herein, using state-of-theart ab initio calculations, we propose the HfTe class of materials, which hosts coexisting type-I, type-II, and type-III Weyl and nodal line phases, along with pseudospin-1/
spin-1 quasiparticles in both electronic and phononic states. We have found that these excitations are robust against variations in exchange-correlation functionals,
spin-orbit coupling, and
lattice parameters, confirming that multiple topological phases in this class of materials are likely to be observed experimentally.
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Strongly Correlated Electrons
Absence of nontrivial local conserved quantities in a class of $U(1)$-symmetric spin-1 chains
Shunsuke Sengoku and Haruki Watanabe
We prove the absence of nontrivial local conserved quantities in a class of $U(1)$-symmetric
spin-$1$ chains with nearest-neighbor interactions in which some of the quadrupolar couplings vanish, a class that is not covered by previous studies. Applying the technique of Shiraishi to these systems, we show that, for every model in this class on a periodic chain of $N$ sites, there is no $k$-local conserved quantity for any $3\le k\le N/2$. In particular, for a frustration-free
spin-$1$ chain that exhibits spontaneous $U(1)$
symmetry breaking at zero temperature in one spatial dimension, we prove that every local conserved quantity with support up to half of the system size is a linear combination of the identity, the total magnetization $S^z$, and the
Hamiltonian itself. This rigorously establishes that, unlike the Heisenberg ferromagnet, the model admits no local order parameter commuting with the
Hamiltonian, so that its continuous
symmetry breaking is enabled by the frustration-free structure rather than by a conserved order parameter. We also prove the absence of $k$-local conserved quantities for $3\le k\le N/2$ in the periodic Motzkin chain, a frustration-free
spin-$1$ chain closely related to the original Motzkin chain, for which spontaneous $U(1)$
symmetry breaking at zero temperature has also been reported.
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Disordered Systems and Neural Networks
Equilibrium and nonequlibrium scaling behaviors of localization transition in a non-Hermitian Aubry-André model with onsite gain and loss
Wen-Jing Yu, Yue-Mei Sun, Xin-Yu Wang et al. (+1 more)
The interplay between non-Hermiticity and localization has attracted considerable interest, yet the driven dynamics of localization transitions in non-Hermitian systems with on-site gain and loss remains largely unexplored. Here we investigate the critical scaling behavior and driven dynamics of the non-Hermitian Aubry-André (AA) model with on-site gain and loss. Through finite-size scaling analyses of the localization length, the inverse participation ratio (IPR), and the energy gap, we extract the critical exponents $\nu = 1.00(2)$, $s = 0.7965(2)$, and $z = 1.999(2)$. These exponents are different from those of both the Hermitian AA model and the nonreciprocal hopping AA model, particularly the IPR exponent $s$, demonstrating that the gain-loss mechanism belongs to a distinct universality class. For the driven dynamics, we focus on the case where the system is initially prepared in a gapless extended state and linearly driven across the critical point. We verify that the finite-time scaling (FTS) framework remains applicable provided that the criterion $z' < r$ is satisfied, where $z' = 1.999(2)$ characterizes the gap closure in the extended phase and $r = z + 1/\nu \approx 2.999$. The predicted FTS scaling forms for the IPR are numerically validated across a wide range of system sizes and driving rates, demonstrating that the unified scaling description can be successfully generalized to the gain-loss type non-Hermitian AA model. Our work not only establishes the gain-loss AA model as a new universality class of localization transitions but also extends the applicability of the FTS framework to non-Hermitian systems with gapless initial states.
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All authors Wen-Jing Yu, Yue-Mei Sun, Xin-Yu Wang, Liang-Jun Zhai
Materials Science
Growth of Altermagnetic {\alpha}-MnTe Films: Substrate Variation and Surface Modification
M. Dittmar, L. Hirnet, H. Haberkamm et al. (+10 more)
Manganese telluride (MnTe) in its hexagonal {\alpha}-MnTe
crystal structure has evolved as one of the altermagnet workhorse materials. The synthesis of MnTe thin films is highly relevant for both fundamental science and device applications. Here, we report on the epitaxial growth of MnTe thin films and
heterostructures. The films are studied by X-ray and electron diffraction as well as soft X-ray angle-resolved photoemission spectroscopy. We demonstrate the ability to grow high-quality {\alpha}-MnTe on various substrates, ranging from transparent band
insulators, over topological
insulators, metallic transition metal chalcogenides, to the van der Waals ferromagnet Fe$_3$GeTe$_2$. While insulating substrates are useful for transport experiments or optical spectroscopy, metallic topological surface states may trigger spintronic interface effects, such as
spin-orbit torques. Metallic substrates, in general, are highly relevant to avoid charging at the insulating MnTe films in electron spectroscopy or microscopy methods. Lastly,
ferromagnetic substrates will be of interest to control magnetization across the interface. In addition, we discuss the formation of superstructures on the MnTe(0001) surfaces, that emerge directly after growth, upon subsequent tellurium evaporation and after thermal treatment. This will be relevant in further studying the surface
magnetic and electronic structure in {\alpha}-MnTe.
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All authors M. Dittmar, L. Hirnet, H. Haberkamm, F. Beisler, C.-W. Chuang, R. Ganser, P. Kagerer, M.-J. Huang, J. Buck, M. Hoesch, K. Rossnagel, M. Ünzelmann, F. Reinert
Statistical Mechanics
Conditional-path Monte Carlo for rare stochastic dynamics on networks: Details and derivations
Thomas Barthel, Jiazheng Sun and Jhao-Hong Peng
The simulation of rare macroscopic events in
stochastic network dynamics, such as widespread epidemic outbreaks, cascading failures in communication networks, or the escape from metastable states in many-body systems, is severely hindered by methodological challenges like catastrophic rejection rates, weight degeneracy, genealogical correlations, and critical slowing down inherent to standard forward-time
algorithms, splitting methods, and transition-path sampling. Conditional-path Monte Carlo (CPMC) overcomes these limitations by employing non-local Swendsen-Wang-like cluster updates that operate directly on full-system trajectories. Serving as the technical companion to [Sun, Moody, and Barthel, arXiv:2608.16171], this paper provides the rigorous mathematical foundations and algorithmic details underlying the CPMC framework. We formally define the joint path-graph probability weights and derive the transition and uniformization sum rules that guarantee detailed balance. Applying the framework to susceptible-infectious-susceptible (SIS) models, we systematically construct and optimize single-node and edge graph vertex sets specifically designed to prevent lock avalanches and maintain the structural mobility of the epidemic trunk. Furthermore, we detail a dynamic programming scheme to exactly implement complex boundary conditions - including patient-zero and macroscopic outbreak-size constraints - enabling the rejection-free generation of valid trajectories. Finally, we assess the computational complexity of the
algorithm, describe parallelization strategies, and validate CPMC against exact solutions for dynamics on small networks.
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Superconductivity
Unconventional Pressure Evolution of Spin-Density-Wave State in La$_{3}$Ni$_{2}$O$_{7}$
Xiaoxiang Zhou, Shiyu Xie, Liangxin Qiao et al. (+13 more)
The discovery of pressure-induced high temperature superconductivity in the
bilayer nickelate La$_{3}$Ni$_{2}$O$_{7}$ has raised the question of how its
spin-density-wave (SDW) state evolves toward the superconducting regime. Here, we report a systematic electronic Raman study of La$_{3}$Ni$_{2}$O$_{7}$ single
crystals under hydrostatic pressures up to 16.51 GPa. Both the SDW gap energy and the transition temperature $T_{\mathrm{SDW}}$ show an overall increase with pressure, while the dimensionless coupling ratio 2$\Delta_{\text{SDW}}/(k_{\text{B}}T_{\text{SDW}})$ remains constant around $\sim7.5$, indicating a robust strong-coupling character of SDW state. At the same time, the Raman SDW peak broadens as pressure is applied, indicating a gradual weakening of long-range SDW order. These results reveal an unusual pressure
evolution in which the SDW energy scale is enhanced while the SDW state becomes progressively less coherent, providing spectroscopic constraints on the
magnetic correlations relevant to superconductivity in
bilayer nickelates.
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All authors Xiaoxiang Zhou, Shiyu Xie, Liangxin Qiao, Hengyuan Zhang, Jun Shu, Rui Liu, Mengwu Huo, Deyuan Hu, Hengjie Liu, Chuansheng Hu, Yilin Wang, Ge He, Zeming Qi, Meng Wang, Dong-Lai Feng, Zengyi Du
Quantum Gases
Universal quantum corrections of two-body correlation in a weakly interspecies interacting binary Bose mixture
Rui-Yan Chen, Zhaoxin Liang and Gao Xianlong
We investigate universal
quantum corrections to two-body correlations in a zero-temperature binary Bose mixture using the Cornwall-Jackiw-Tomboulis two-particle-irreducible effective action formalism. In the weak interspecies-coupling regime, a saddle-point treatment based on Hubbard-Stratonovich transformations can be combined with a two-loop expansion and a gapless Hartree-Fock correction, thereby preserving the Goldstone
theorem and reducing the coupled two-component problem to two analytically solvable single-component theories. Within this framework, we derive the ground-state energy density as a low-density expansion in the gas parameter, together with the
quantum depletion and chemical potentials. The results exhibit a simple mapping to the single-component case: the universal
quantum corrections of the mixture are obtained by evaluating the known single-component series at an effective scattering length $a_{\sigma\sigma}-a_{12}$ for each species, where $a_{\sigma\sigma}$ and $a_{12}$ are the intra- and interspecies $s$-wave scattering lengths. This reproduces Petrov's equation of state at one-loop order in the weak-coupling limit and yields beyond-Lee-Huang-Yang corrections at two-loop order. We also analyze the role of mass imbalance, which enters the energy density through the exact rescaling factor $(1+m_{1}/m_{2})/2$.
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Materials Science
Intra-atomic magnetic octupoles and their coupling to cluster magnetic octupoles in Chiral antiferromagnets Mn$_3$Sn
Dohoon Park, Seungyun Han and Hyun-Woo Lee
We demonstrate that Mn$_3$Sn hosts finite intra-atomic
magnetic octupoles (AMOs) $\mathbf{o}$ in addition to the well-established cluster
magnetic octupole (CMO) $\mathbf{O}$. In contrast to the cluster-scale CMO, the AMO is a site-localized
magnetic multipole associated with the anisotropic intra-atomic
spin density.
Symmetry analysis shows that the CMO and AMO transform in the same representation, allowing a bilinear interaction of the form $-g\,\mathbf{O}\cdot\mathbf{o}$. Using first-principles calculations, we confirm the presence of finite AMO densities and show that the AMO transforms concomitantly with the CMO under rotations of the noncollinear
magnetic structure, providing microscopic evidence for the coupling between them. We further show that the
magnetic band splitting can be represented by projected AMO operators, with
manifold-dependent effective octupolar exchange coefficients in realistic Mn$_3$Sn. The presence of AMOs has three important implications. First, we show that the nonrelativistic
spin splitting of Mn$_3$Sn can be described in terms of projected AMO operators, with
manifold-dependent effective octupolar exchange coefficients, establishing the AMO as a microscopic operator underlying the
spin splitting. Second, the AMO reveals a close connection between Mn$_3$Sn and $d$-wave altermagnets from the
magnetic-octupole perspective. Third, the $\mathbf{O}\cdot\mathbf{o}$ coupling suggests a new route to manipulate the CMO using AMO currents, opening a direction for controlling the multipolar order in Mn$_3$Sn.
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Disordered Systems and Neural Networks · Cross-listed from stat.ML
Nonlocal Transition Kernel for Efficient Learning of Restricted Boltzmann Machines
Kaiji Sekimoto and Muneki Yasuda
Learning restricted Boltzmann machines (RBMs) is computationally challenging because it requires expectations whose exact evaluation is generally intractable. The expectations are typically evaluated using a sampling approximation based on blocked Gibbs sampling (BGS), which is a local Markov chain Monte Carlo transition kernel. However, the locality of BGS can lead to poor sampling quality when the RBM has high energy barriers, thereby degrading learning performance. Deep tempering (DT), which performs parallel tempering over a sequence of learnable RBMs including the training RBM, alleviates this locality issue. However, DT algorithmically requires multiple steps to move through the RBM sequence to achieve a nonlocal transition. In this paper, we propose a transition kernel defined over the RBM sequence used in DT. The proposed kernel has a round-trip structure over the sequence, enabling nonlocal moves within a single transition while leaving the RBM sequence invariant. Numerical experiments show that the proposed kernel performs nonlocal transitions more frequently and achieves higher sampling quality with fewer transitions than BGS and DT. We further verify that learning based on the proposed kernel is more stable and mitigates the training failures observed with BGS- and DT-based learning.
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Mesoscale and Nanoscale Physics
Flat band and Bulk-Boundary correspondence in a non-Hermitian trimerized lattice model with generic boundary conditions
Supriyo Ghosh, Pijush K. Ghosh and Shreekantha Sil
We consider a Su-Schrieffer-Heeger(SSH)-type trimer model with next-nearest-neighbor(NNN) interaction and balanced loss-gain(BLG) to study the combined effect of
lattice symmetries,
topology, non-hermiticity and general boundary conditions(GBC)on the existence of flat band and the nature of Bulk-Boundary correspondence(BBC). We derive the necessary and sufficient conditions for the existence of an entirely real spectrum under the periodic boundary condition(PBC). The exact expressions for the compact localized states(CLS) and energy
eigenvalues corresponding to flat bands are derived analytically under the PBC. We establish topological phase transitions(TPT) for PT-
symmetry and pseudo-
chiral symmetry through the computation of the Zak phase and sub-
lattice Zak phase, respectively. The
Hamiltonian under the open boundary condition(OBC) is studied numerically, and edge states are observed in the topologically non-trivial phase, thereby establishing the non-hermitian BBC. The CLS exists in both bulk and the boundary for systems having only pseudo-
chiral symmetry, and an additional PT-
symmetry destroys the CLS at the boundary. We generalize a known formalism to study the same
Hamiltonian under GBC, and derive analytic expressions for the energy and eigenstates for a class of boundary conditions in parametric ranges which admit flat band under the PBC. The edge states for these boundary conditions, including the OBC, are obtained analytically in the topologically non-trivial phase, thereby establishing BBC. The non-hermitian skin effect(NHSE) is seen in the model with reciprocal bulk interaction and strongly non-reciprocal boundary terms. The winding number based on spectral
topology is computed analytically.
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