CMP Journal 2025-07-11
Statistics
Nature Physics: 2
Physical Review Letters: 8
Physical Review X: 2
arXiv: 88
Nature Physics
Measurement of phonon angular momentum
Original Paper | Sensors and biosensors | 2025-07-10 20:00 EDT
H. Zhang, N. Peshcherenko, Fazhi Yang, T. Z. Ward, P. Raghuvanshi, L. Lindsay, Claudia Felser, Yang Zhang, J.-Q. Yan, H. Miao
In condensed matter, angular momentum is intimately related to the emergence of topological quantum states, including chiral superconductivity, quantum spin liquids and various chiral quasiparticles. Recently, it has been predicted that microscopic lattice excitations, known as phonons, can carry finite angular momentum, leading to specific physical properties of materials. However, phonon angular momentum has not yet been observed directly. Here we demonstrate that angular momentum conservation results in a macroscopic mechanical torque when applying a time-reversal symmetry-breaking thermal gradient along the chiral axis of single-crystal tellurium. We probe this torque using a cantilever-based device and establish that it changes sign by flipping the chirality or thermal gradient. This behavior disappears in polycrystalline samples that lack a preferred chirality. Our experimental results align well with theoretical calculations. We provide compelling evidence for phonon angular momentum, which might enable quantum states with potential applications in microelectronics.
Sensors and biosensors, Structure of solids and liquids
Topological excitonic insulator with tunable momentum order
Original Paper | Phase transitions and critical phenomena | 2025-07-10 20:00 EDT
Md Shafayat Hossain, Zi-Jia Cheng, Yu-Xiao Jiang, Tyler A. Cochran, Song-Bo Zhang, Huangyu Wu, Xiaoxiong Liu, Xiquan Zheng, Guangming Cheng, Byunghoon Kim, Qi Zhang, Maksim Litskevich, Junyi Zhang, Jinjin Liu, Jia-Xin Yin, Xian P. Yang, Jonathan D. Denlinger, Massimo Tallarida, Ji Dai, Elio Vescovo, Anil Rajapitamahuni, Nan Yao, Anna Keselman, Yingying Peng, Yugui Yao, Zhiwei Wang, Luis Balicas, Titus Neupert, M. Zahid Hasan
Correlated topological materials often maintain a delicate balance among physical symmetries. Many topological orders are symmetry protected, whereas most correlated phenomena arise from spontaneous symmetry breaking. Cases where symmetry breaking induces a non-trivial topological phase are rare. Here we demonstrate the presence of two such phases in Ta2Pd3Te5, where Coulomb interactions form excitons that condense below 100 K, one with zero and the other with finite momentum. We observed a full spectral bulk gap, which stems from exciton condensation. This topological excitonic insulator state spontaneously breaks mirror symmetries but involves a weak structural coupling. Scanning tunnelling microscopy shows gapless boundary modes in the bulk insulating phase. Their magnetic field response, together with theoretical modelling, indicates a topological origin. These observations establish Ta2Pd3Te5 as a topological excitonic insulator in a three-dimensional crystal. Thus, our results manifest a unique sequence of topological exciton condensations in a bulk crystal, offering exciting opportunities to study critical behaviour and excitations.
Phase transitions and critical phenomena, Topological matter
Physical Review Letters
Experimental Characterization of Quantumness Using the Uncertainty Principle, Coherence, and Nonlocality
Research article | Quantum coherence & coherence measures | 2025-07-10 06:00 EDT
Yan-Han Yang, Xin-Zhu Liu, Xing-Zhou Zheng, Jun-Li Jiang, Xue Yang, Shao-Ming Fei, Zhihao Ma, Zizhu Wang, and Ming-Xing Luo
Heisenberg’s uncertainty principle, coherence, and Bell nonlocality have been individually examined through many experiments. In this Letter, we systematically characterize all of this quantumness in a unified manner. We first construct universal uncertainty relations to reveal intrinsic features of incompatible measurements, which include all the state-independent uncertainties as special cases. We further extend to witness both quantum coherence and Bell nonlocality. We finally perform experiments with unified two-photon states and validate the uncertainty principle, coherence, and Bell nonlocality within experimental error. Our methods for witnessing quantumness are valuable in characterizing quantum correlations in quantum information processing.
Phys. Rev. Lett. 135, 020201 (2025)
Quantum coherence & coherence measures, Quantum correlations in quantum information, Quantum correlations, foundations & formalism, Quantum foundations, Quantum measurements
Sharp Finite Statistics for Quantum Key Distribution
Research article | Quantum communication | 2025-07-10 06:00 EDT
Vaisakh Mannalath, Víctor Zapatero, and Marcos Curty
The performance of quantum key distribution (QKD) heavily depends on statistical inference. For a broad class of protocols, the central statistical task is a random sampling problem, customarily addressed using a hypergeometric tail bound due to Serfling. Here, we provide an alternative solution for this task of unprecedented tightness among QKD security analyses. As a by-product, confidence intervals for the average of nonidentical Bernoulli parameters follow too. These naturally fit in statistical analyses of decoy-state QKD and also outperform standard tools. Last, we show that, in a vast parameter regime, the use of tail bounds is not enforced because the cumulative mass function of the hypergeometric distribution is accurately computable. This sharply decreases the minimum block sizes necessary for QKD, and reveals the tightness of our analytical bounds when moderate-to-large blocks are considered.
Phys. Rev. Lett. 135, 020803 (2025)
Quantum communication, Quantum communication, protocols & technology, Quantum cryptography
Form Factors from String Amplitudes
Research article | Scattering amplitudes | 2025-07-10 06:00 EDT
Qu Cao
In this Letter, we propose a stringy model for $n$-point tree-level form factor with the off-shell operator in the scalar and gluon theories from the bosonic string disk amplitude: $n$ open string states and one closed string state scatter on the disk. In the field-theory limit (${\alpha }^{‘ }\rightarrow 0$), the ‘’stringy form factor’’ reduces to the form factor, which helps us to investigate the hidden properties of the field-theory form factors, manifest the factorization and soft behaviors, and uncover more nontrivial relations between form factors and scattering amplitudes.
Phys. Rev. Lett. 135, 021603 (2025)
Scattering amplitudes, Form factors
Collision-Energy Dependence in Heavy-Ion Collisions from Nonlinear QCD Evolution
Research article | Charged-particle multiplicity | 2025-07-10 06:00 EDT
Heikki Mäntysaari, Björn Schenke, Chun Shen, and Wenbin Zhao
We explore the effects of including the energy dependence determined from evolution equations within the color glass condensate framework on observables in ultrarelativistic heavy-ion collisions. This amounts to integrating the JIMWLK evolution equations into the impact parameter-dependent glasma model, which is then coupled to viscous relativistic hydrodynamics. This methodology allows for a systematic representation of nuclei at specific Bjorken-$x$ values, which are probed at different center-of-mass energies of the collision and rapidities of final state particles. Comparing the methodology to the conventional impact parameter-dependent glasma model, we find significant effects on multiplicity distributions and particle spectra, especially in smaller collision systems at the highest center-of-mass energies. Our results highlight the importance of incorporating nonlinear QCD evolution in the description of heavy-ion collisions at varying center-of-mass energies, as the precise extraction of transport coefficients will be affected. This Letter establishes a robust framework for understanding the quark gluon plasma and nuclear structure at high energy, integrating small-$x$ physics into the initial conditions of heavy-ion collisions.
Phys. Rev. Lett. 135, 022302 (2025)
Charged-particle multiplicity, Electron-ion collisions, Quark-gluon plasma, Relativistic heavy-ion collisions
Isospin Symmetry Breaking Disclosed in the Decay of Three-Proton Emitter $^{20}\mathrm{Al}$
Research article | Nuclear binding | 2025-07-10 06:00 EDT
X.-D. Xu et al.
The previously unknown nucleus $^{20}\mathrm{Al}$ has been observed for the first time by detecting its in-flight decays. Tracking trajectories of all decay products with silicon microstrip detectors allowed for a conclusion that $^{20}\mathrm{Al}$ is unbound with respect to three-proton ($3p$) emission. The $3p$-decay energy of the $^{20}\mathrm{Al}$ ground state has been determined to be $1.93{(}_{- 0.10}^{+0.12})\text{ }\text{ }\mathrm{MeV}$ through a detailed study of angular correlations of its decay products, $^{17}\mathrm{Ne}+p+p+p$. This value is significantly smaller than the predictions inferred from the isospin symmetry by using the known neutron separation energy of its mirror nucleus $^{20}\mathrm{N}$, which indicates a possible isospin symmetry breaking in the mirror nuclei $^{20}\mathrm{Al}$ and $^{20}\mathrm{N}$. This observed isospin symmetry breaking is supported by the calculations of the continuum embedded theoretical frameworks, describing the observed $^{20}\mathrm{Al}$ ground state as a $1p$ $s$-wave state with a spin-parity of ${1}^{- }$, which differs from the spin-parity (${2}^{- }$) of the $^{20}\mathrm{N}$ ground state. The $^{20}\mathrm{Al}$ ground state decays by sequential $1p\text{- }2p$ emission via the intermediate ground state of $^{19}\mathrm{Mg}$, which is the first observed case of ‘’daughter’’ $2p$ radioactivity following $1p$ decay of the parent state.
Phys. Rev. Lett. 135, 022502 (2025)
Nuclear binding, Nuclear structure & decays, Proton emission, Rare & new isotopes, 20 ≤ A ≤ 38, Radioactive beams
Optical Protection of Alkali-Metal Atoms from Spin Relaxation
Research article | Atomic & molecular collisions | 2025-07-10 06:00 EDT
Avraham Berrebi, Mark Dikopoltsev, Ori Katz, and Or Katz
We present an optical technique for suppressing relaxation in alkali-metal spins using a single off-resonant laser beam. The method harnesses a physical mechanism that synchronizes Larmor precession in the two hyperfine manifolds, protecting magnetic coherence from relaxation caused by spin-exchange and other hyperfine-changing collisions. We experimentally demonstrate up to a ninefold reduction in decoherence of warm cesium vapor, achieving simultaneous protection from both spin-exchange relaxation and partial depolarization from coated cell walls. The technique substantially enhances the spin precession quality factor and maintains a stable gyromagnetic ratio independent of spin polarization, even under frequent collisions. These findings offer a pathway for mitigating dominant relaxation channels in alkali-metal-based applications and experiments, particularly in anti-relaxation-coated cells.
Phys. Rev. Lett. 135, 023201 (2025)
Atomic & molecular collisions, Atomic & molecular processes in external fields, Exchange interaction, Magnetometry, Quantum control, Alkali metals, Atomic gases
Joint Estimation of a Two-Phase Spin Rotation beyond Classical Limit
Research article | Cold atoms & matter waves | 2025-07-10 06:00 EDT
Jiahao Cao, Xinwei Li, Tianwei Mao, Wenxin Xu, and Li You
Quantum metrology employs entanglement to enhance measurement precision [V. Giovannetti et al., Quantum-enhanced measurements: Beating the standard quantum limit, Science 306, 1330 (2004), V. Giovannetti et al., Advances in quantum metrology, Nat. Photonics 5, 222 (2011), and L. Pezz'e et al., Quantum metrology with nonclassical states of atomic ensembles, Rev. Mod. Phys. 90, 035005 (2018)]. The focus and progress so far have primarily centered on estimating a single parameter. In diverse application scenarios, estimation of more than one single parameter is often required. Joint estimation of multiple parameters can benefit from additional advantages for further enhanced precision. Here we report quantum-enhanced estimation of simultaneous spin rotations around two orthogonal axes, making use of spin-nematic squeezing in an atomic Bose-Einstein condensate. Aided by the $F=2$ atomic ground hyperfine manifold coupled to the nematic-squeezed $F=1$ states as an auxiliary field through a sequence of microwave (MW) pulses, multiple spin-1 observables are simultaneously measured, reaching an enhancement factor 3.3 to 6.3 decibels (dB) beyond the classical limit over a wide range of rotation angles. Our work realizes the first quantum enhanced multiparameter estimation using entangled massive particles. The techniques developed and the protocols implemented also highlight the application of two-mode squeezed vacuum states in quantum-enhanced sensing of noncommuting spin rotations simultaneously.
Phys. Rev. Lett. 135, 023403 (2025)
Cold atoms & matter waves, Quantum measurements, Quantum metrology, Atomic gases, Spinor Bose-Einstein condensates, Atom interferometry
Meron Spin Textures in Momentum Space Spawning from Bound States in the Continuum
Research article | Metamaterials | 2025-07-10 06:00 EDT
Lixi Rao, Jiajun Wang, Xinhao Wang, Shunben Wu, Xingqi Zhao, Wenzhe Liu, Rensheng Xie, Yijie Shen, Lei Shi, and Jian Zi
An arrangement of spins known as a meron turns out to be easier to make in momentum space than in real space.
Phys. Rev. Lett. 135, 026203 (2025)
Metamaterials, Nanophotonics, Photonic crystals, Topological effects in photonic systems
Physical Review X
Noninvertible Peccei-Quinn Symmetry and the Massless Quark Solution to the Strong $CP$ Problem
Research article | Anomalies | 2025-07-10 06:00 EDT
Clay Córdova, Sungwoo Hong, and Seth Koren
A new theory revives the ruled-out massless quark solution to the strong CP problem by linking quark color and flavor through generalized symmetries, offering a fresh path beyond the Standard Model.
Phys. Rev. X 15, 031011 (2025)
Anomalies, Grand unified models, Instantons, Naturalness, Nonperturbative effects in field theory, Symmetries
Observation of Orbital-Selective Dual Modulations in an Anisotropic Antiferromagnetic Kagome Metal ${\mathrm{TbTi}}{3}{\mathrm{Bi}}{4}$
Research article | Electronic structure | 2025-07-10 06:00 EDT
Renjie Zhang et al.
*et al.*In TbTi3Bi4, an orbital-specific response in the antiferromagnetic state reveals a deep connection between orbital behavior and magnetic ordering.
Phys. Rev. X 15, 031012 (2025)
Electronic structure, Magnetism, Antiferromagnets, Kagome lattice, Angle-resolved photoemission spectroscopy, Density functional theory, Magnetization measurements, Resistivity measurements
arXiv
Large-scale portfolio optimization with variational neural annealing
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Nishan Ranabhat, Behnam Javanparast, David Goerz, Estelle Inack
Portfolio optimization is a routine asset management operation conducted in financial institutions around the world. However, under real-world constraints such as turnover limits and transaction costs, its formulation becomes a mixed-integer nonlinear program that current mixed-integer optimizers often struggle to solve. We propose mapping this problem onto a classical Ising-like Hamiltonian and solving it with Variational Neural Annealing (VNA), via its classical formulation implemented using autoregressive neural networks. We demonstrate that VNA can identify near-optimal solutions for portfolios comprising more than 2,000 assets and yields performance comparable to that of state-of-the-art optimizers, such as Mosek, while exhibiting faster convergence on hard instances. Finally, we present a dynamical finite-size scaling analysis applied to the S&P 500, Russell 1000, and Russell 3000 indices, revealing universal behavior and polynomial annealing time scaling of the VNA algorithm on portfolio optimization problems.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG), Portfolio Management (q-fin.PM)
16 pages, 13 figures, 1 table
Majorana edge reconstruction and the $ν=5/2$ non-Abelian thermal Hall puzzle
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Tevž Lotrič, Taige Wang, Michael P. Zaletel, Steven H. Simon, S. A. Parameswaran
Pioneering thermal transport measurements on two-dimensional electron gases in high magnetic fields have demonstrated that the quantized Hall state at filling factor $ \nu=5/2$ has a thermal Hall conductance $ \kappa$ quantized in half-integer multiples of $ \kappa_0 = {\pi^2 k_B^2 T}/{3h}$ . Half-integer $ \kappa/\kappa_0$ is a signature of neutral Majorana edge modes, in turn linked to the presence of non-Abelian anyon excitations in the bulk. However, the experimentally observed value of $ \kappa$ corresponds to the ‘PH-Pfaffian’ state, in tension with numerical studies which instead favor either the Pfaffian or the AntiPfaffian. A variety of mechanisms have been invoked to explain this discrepancy, but have been either ruled out by further experiments or else involve fine-tuning. Building on density-matrix-renormalization group studies of physically realistic edges and analytic calculations of edge structure, we propose an alternative resolution of this puzzle involving an ‘edge reconstruction’ solely involving the neutral Majorana sector of the theory. Such a Majorana edge reconstruction can “screen’’ a Pfaffian or AntiPfaffian bulk, so that transport signatures become indistinguishable from those of the PH-Pfaffian. We argue that this physically natural scenario is consistent with experiment.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
10+12 pages
Finite-temperature criticality through quantum annealing
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Gianluca Teza, Francesco Campaioli, Marco Avesani, Oren Raz
Critical phenomena at finite temperature underpin a broad range of physical systems, yet their study remains challenging due to computational bottlenecks near phase transitions. Quantum annealers have attracted significant interest as a potential tool for accessing finite temperature criticality beyond classical reach, but their utility in precisely resolving criticality has remained limited by noise, hardware constraints, and thermal fluctuations. Here we overcome these challenges, showing that careful calibration and embedding allow quantum annealers to capture the full finite-temperature critical behavior of the paradigmatic two-dimensional Ising ferromagnet. By tuning the energy scale of the system and mitigating device asymmetries, we sample effective Boltzmann distributions and extract both the critical temperature and the associated critical exponents. Our approach opens the study of equilibrium and non-equilibrium critical phenomena in a broad class of systems at finite temperature.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Confined and deconfined chaos in classical spin systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Hyeongjin Kim, Robin Schäfer, David M. Long, Anatoli Polkovnikov, Anushya Chandran
Weakly perturbed integrable many-body systems are typically chaotic and thermal at late times. However, there are distinct relationships between the timescales for thermalization and chaos. The typical relationship is confined chaos: when trajectories are still confined to regions in phase space with constant conserved quantities (actions), the conjugate angle variables are already unstable. Confined chaos thus far precedes thermalization. In a different relationship, which we term deconfined chaos, chaotic instabilities and thermalization occur on the same timescale. We investigate these two qualitatively distinct scenarios through numerical and analytical studies of two perturbed integrable classical spin models: the Ishimori spin chain (confined chaos), and the central spin model with XX interactions (deconfined chaos). We analytically establish (super)-integrability in the latter model in a microcanonical shell. Deconfined chaos emerges through the separation of phase space into large quasi-integrable regions and a thin chaotic manifold. The latter causes chaos and thermalization on the fastest possible timescale, which is proportional to the inverse perturbation strength. This behavior is reminiscent of the quantum SYK models and strange metals.
Statistical Mechanics (cond-mat.stat-mech), Chaotic Dynamics (nlin.CD), Exactly Solvable and Integrable Systems (nlin.SI)
23 pages, 16 figures
Triplet Exciton-driven Topological Mott insulator at Finite Temperature
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Motivated by experiments in which the quantum anomalous Hall (QAH) charge gap greatly exceeds the Curie temperature, we apply determinantal quantum Monte Carlo to two complementary lattice models with different geometries: the checkerboard quantum-spin-Hall-Hubbard model and the generalized Kane-Mele-Hubbard model. In both cases an incompressible QAH phase with total Chern number $ C=\pm 1$ emerges at quarter filling well above the Curie temperature. Each spin channel carries its own nonquantized Chern number while remaining only partly filled, revealing a topological Mott insulator where Mottness opens the charge gap before magnetic order appears. Charge excitations bind triplet excitons that suppress net magnetization, a many-body dynamical effect absent in mean-field theory. The concurrence of these results on two very different models shows that coupling Mottness with band topology generically yields a high-temperature QAH insulator whose charge excitations are dressed by triplet excitons.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Correlated quantum shift vector of particle-hole excitations
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Xu Yang, Ajit Srivastava, Justin C. W. Song
Excitons are a prime example of how electron interactions affect optical response and excitation. We demonstrate that, beyond its spectra, the bound nature of an exciton’s electron-hole pair produces a correlated quantum geometry: excitonic excitations possess a quantum shift vector that is independent of light polarization. We find this counterintuitive behavior has dramatic consequences for geometric response: e.g., in noncentrosymmetric but non-polar materials, vertical excitonic transitions possess vanishing shift vector zeroing their shift photocurrent; this contrasts with finite and strongly light polarization dependent shift vectors for non-interacting delocalized particle-hole excitations. This dichotomy makes shift vector a sharp diagnostic of the pair localization properties of particle-hole excitations and demonstrates the non-perturbative effects of electron interactions in excited state quantum geometric response.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
16 pages, 2 figures
Antisymmetric Raman response
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
We develop the theory of antisymmetric Raman response, defined as the difference between the Raman signals of two scattering geometries related by an exchange of mutually perpendicular incoming and the outgoing photon polarizations. Such responses, finite in orthorhombic or lower symmetry systems, are related to cross-susceptibilities of two Raman operators and are characterized by the absence of intraband terms. This is in contrast to standard Raman responses which measure auto-susceptibilities where both intra- and interband processes contribute. We illustrate the theory with examples from the charge density wave rare-earth tritellurides and the excitonic insulator Ta$ _2$ NiSe$ _5$ . Our theory establishes antisymmetric Raman response as a unique tool to probe microscopic features such as interband energy scales and to detect reflection symmetry breaking.
Strongly Correlated Electrons (cond-mat.str-el)
5 pages, 3 figures + SM
Generic and intrinsic negative longitudinal magnetoresistance at weak fields in non-magnetic metals with inversion symmetry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Rhonald Burgos Atencia, Antonio Vecchione, Denys Makarov, Carmine Ortix
Negative longitudinal magnetoresistance (NLMR) is a decrease in the electrical resistivity of a material when the driving electric field and an external magnetic field are collinear. In the semiclassical weak field regime, the NLMR of non-magnetic metals is activated in the presence of substantial concentrations of Berry curvature (BC). This restricts the appearance of a semi-classical NLMR to metals with acentric crystalline arrangements, including Weyl semimetals. Here, we show a previously unidentified mechanism of semi-classical NLMR that can be present in strongly spin-orbit coupled non-magnetic metals even if the crystal possess bulk inversion symmetry. A Zeeman-activated BC directly couples to the orbital motion of Bloch electrons to generate a negative MR that scales with the relaxation time precisely as the Drude resistivity. Importantly, the Zeeman-activated BC is \emph{independent} of the external magnetic field strength. It is instead related to the degree of non-parabolicity of the spin-orbit coupled electronic bands. We show that this NLMR mechanism, which is independent of the Landé $ g$ -factor, is generic and appears in \emph{all} centrosymmetric point groups and can occur both in topological and conventional conductors.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Short-wavelength mesophases in the ground states of core-softened particles in two-dimensions
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Rômulo Cenci, Lucas Nicolao, Alejandro Mendoza-Coto
We describe the formation of short-wavelength mesophases in a two-dimensional core-softened particle system. By proposing a series of specific ansatz for each relevant phase, we performed a variational analysis to obtain the ground-state phase diagram. Our results reveal a variety of cluster lattice phases with distinct cluster orientations, alongside traditional two-dimensional Bravais lattices such as square, triangular, oblique, and rectangular structures, as well as other non-Bravais arrangements including honeycomb and kagome phases. We characterize in detail the ground-state phase transitions and identify coexistence regions between competing phases, capturing both first-order and continuous transitions. In addition, we highlight the crucial role of the competing length scales introduced by the hard-core repulsion in shaping the rich landscape of mesophases, emphasizing the interplay between intra-cluster structure and inter-cluster organization. This study provides a systematic framework that could support future investigations of classical thermal melting behavior or quantum phase transitions in similar cluster-forming systems.
Soft Condensed Matter (cond-mat.soft), Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech)
18 pages, 7 figures
3D Atomic-Scale Metrology of Strain Relaxation and Roughness in Gate-All-Around (GAA) Transistors via Electron Ptychography
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Shake Karapetyan, Steven E. Zeltmann, Glen Wilk, Ta-Kun Chen, Vincent D.-H. Hou, David A. Muller
To improve transistor density and electronic performance, next-generation semiconductor devices are adopting three-dimensional architectures and feature sizes down to the few-nm regime, which require atomic-scale metrology to identify and resolve performance-limiting fabrication challenges. X-ray methods deliver three-dimensional imaging of integrated circuits but lack the spatial resolution to characterize atomic-scale features, while conventional electron microscopy offers atomic-scale imaging but limited depth information. We demonstrate how multislice electron ptychography (MEP), a computational electron microscopy technique with sub-Ångström lateral and nanometer-scale depth resolution, enables 3D imaging of buried features in devices. By performing MEP on prototype gate-all-around transistors we uncover and quantify distortions and defects at the interface of the 3D gate oxide wrapped around the channel. We find that the silicon in the 5-nm-thick channel gradually relaxes away from the interfaces, leaving only 60% of the atoms in a bulk-like structure. Quantifying the interface roughness, which was not previously possible for such small 3D structures but strongly impacts carrier mobility, we find that the top and bottom interfaces show different atomic-scale roughness profiles, reflecting their different processing conditions. By measuring 3D interface roughness simultaneously with strain relaxation and atomic-scale defects, from a single MEP dataset, we provide direct experimental values of these performance-limiting parameters needed for modeling and early fabrication optimization.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
43 pages, 14 figures
Ordering According to Size of Disks in a Narrow Channel
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Dan Liu, Michael Karbach, Gerhard Müller
A long and narrow channel confines disks of two sizes. The disks are randomly agitated in a widened channel under moderate pressure, then jammed according to a tunable protocol. We present exact results that characterize jammed macrostates (volume, entropy, jamming patterns). The analysis divides jammed disk sequences into overlapping tiles out of which statistically interacting quasiparticles are constructed. The fractions of small and large disks are controlled by a chemical potential adapted to configurational statistics of granular matter. The results show regimes for the energy parameters (determined by the jamming protocol) that either enhance or suppress the mixing of disk sizes. Size segregation or size alternation driven by steric forces alone are manifestations of a broken symmetry.
Soft Condensed Matter (cond-mat.soft)
8 pages, 1 figure, 3 tables. arXiv admin note: substantial text overlap with arXiv:2507.05420
Exact Solutions for Bimodal Distributions under Stochastic Plasma Irradiation in Thin Films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Joel Saucedo, Uday Lamba, Hasitha Mahabaduge
A persistent paradox complicates the study of plasma-irradiated thin films, where bimodal grain distributions and ambiguous scaling laws, roughly shifting between $ \Phi^{-1/2}$ and $ \Phi^{-1}$ , or a general inverse dependence on plasma flux, are empirical yet remain theoretically unreconciled. Existing models fail to unify noise-driven evolution, defect saturation kinetics, and nucleation-loss balance within a single, self-consistent formalism. This work resolves these discrepancies by developing the first exact analytical theory for this system. We derive the closed-form steady-state grain area distribution, $ P_{ss}(A)$ , establish the precise dimensionless threshold for bimodality onset at $ \Pi_c = 4/(3\sqrt{3})$ , and demonstrate that defect saturation physics mandate a universal $ \langle A \rangle \propto \kappa^2 \Phi^{-1} e^{+2E_b/k_B T_s}$ scaling law. The framework reveals how competition between stochastic impingement and deterministic growth triggers microstructure fragmentation, resolving long-standing ambiguities in irradiation-induced surface evolution and providing a predictive foundation for materials processing.
Materials Science (cond-mat.mtrl-sci), Plasma Physics (physics.plasm-ph)
14 pages, 4 figures
A physics-informed neural network for modeling fracture without gradient damage: formulation, application, and assessment
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Aditya Konale, Vikas Srivastava
Accurate computational modeling of damage and fracture remains a central challenge in solid mechanics. The finite element method (FEM) is widely used for numerical modeling of fracture problems; however, classical damage models without gradient regularization yield mesh-dependent and usually inaccurate predictions. The use of gradient damage with FEM improves numerical robustness but introduces significant mathematical and numerical implementation complexities. Physics-informed neural networks (PINNs) can encode the governing partial differential equations, boundary conditions, and constitutive models into the loss functions, offering a new method for fracture modeling. Prior applications of PINNs have been limited to small-strain problems and have incorporated gradient damage formulation without a critical evaluation of its necessity. Since PINNs in their basic form are meshless, this work presents a PINN framework for modeling fracture in elastomers undergoing large deformation without the gradient damage formulation. The PINN implementation here does not require training data and utilizes the collocation method to formulate physics-informed loss functions. We have validated the PINN’s predictions for various defect configurations using benchmark solutions obtained from FEM with gradient damage formulation. The crack paths obtained using the PINN are approximately insensitive to the collocation point distribution. This study offers new insights into the feasibility of using PINNs without gradient damage and suggests a simplified and efficient computational modeling strategy for fracture problems. The performance of the PINN has been evaluated through systematic variations in key neural network parameters to provide guidance for future applications. The results provide motivation for extending PINN-based approaches to a broader class of materials and damage models in mechanics.
Soft Condensed Matter (cond-mat.soft)
A version of this manuscript has been submitted for peer review
Stabilization of the first-order phase transition character and Enhancement of the Electrocaloric Effect by NBT substitution in BaTiO$_3$ ceramics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
M. Karakaya, I. Gurbuz, L. Fulanovic, U. Adem
The electrocaloric properties of BaTiO$ _3$ -based lead-free ferroelectric materials have been widely investigated. One approach to achieving a large electrocaloric response is to exploit the substantial polarization change associated with the first-order phase transition at the Curie temperature. Following this strategy, we investigated the electrocaloric response of (1$ -x$ )BaTiO$ _3$ -$ x$ Na$ _{0.5}$ Bi$ _{0.5}$ TiO$ _3$ (BT-NBT) ceramics for x = 0.05, 0.10, 0.20, and 0.30. In this BT-rich region of the solid solution, it is established that increasing the NBT content enhances the tetragonality of BaTiO$ 3$ . We show that this increase in tetragonality helps maintain the first-order nature of the phase transition and enables a correspondingly large electrocaloric response, despite the simultaneous enhancement of relaxor ferroelectric character with NBT substitution. A significantly large effective electrocaloric temperature change ($ \Delta T{\mathrm{eff}}$ ) of ~1.65 K was obtained for the x = 0.20 composition under an applied field of 40 kV/cm using direct electrocaloric measurements, in reasonable agreement with the indirect results.
Materials Science (cond-mat.mtrl-sci)
accepted version of the article published in J. Mater. Chem. C. 10 Pages, 7 Figures. Plus SI file as a single pdf
J. Mater. Chem. C, 2024,12, 19612-19619
Thermodynamic Prediction Enabled by Automatic Dataset Building and Machine Learning
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Juejing Liu, Haydn Anderson, Noah I. Waxman, Vsevolod Kovalev, Byron Fisher, Elizabeth Li, Xiaofeng Guo
New discoveries in chemistry and materials science, with increasingly expanding volume of requisite knowledge and experimental workload, provide unique opportunities for machine learning (ML) to take critical roles in accelerating research efficiency. Here, we demonstrate (1) the use of large language models (LLMs) for automated literature reviews, and (2) the training of an ML model to predict chemical knowledge (thermodynamic parameters). Our LLM-based literature review tool (LMExt) successfully extracted chemical information and beyond into a machine-readable structure, including stability constants for metal cation-ligand interactions, thermodynamic properties, and other broader data types (medical research papers, and financial reports), effectively overcoming the challenges inherent in each domain. Using the autonomous acquisition of thermodynamic data, an ML model was trained using the CatBoost algorithm for accurately predicting thermodynamic parameters (e.g., enthalpy of formation) of minerals. This work highlights the transformative potential of integrated ML approaches to reshape chemistry and materials science research.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Local imperfect feedback control in non-equilibrium biophysical systems enabled by thermodynamic constraints
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Carlos Floyd, Aaron R. Dinner, Suriyanarayanan Vaikuntanathan
Understanding how biological systems achieve robust control despite relying on imperfect local information remains a challenging problem. Here, we consider non-equilibrium models which are generically used to describe natural and synthetic biological processes, such as gene regulation and protein conformational dynamics, and investigate their capacity for effective control using imperfect local feedback mechanisms. We derive a thermodynamic constraint on the response of non-equilibrium steady-state properties to changes in the driving forces. We show that this constraint enables linear, local, and easily implementable feedback rules to achieve environmental tracking and adaptation without consideration of network topology. In particular, we demonstrate that local stability of these feedback dynamics implies global stability for systems with one or two chemical regulators, regardless of the network topology. For higher-dimensional systems, global stability is not guaranteed. However, in part due to simplifications in attractor landscapes implied by our thermodynamic constraint, we find the basin of attraction remains significantly larger than would be expected from linear approximation alone. Our findings provide insight into how biological and synthetically engineered systems can respond effectively to environmental changes given only minimal feedback, without highly engineered interactions or precise parameter tuning.
Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph), Molecular Networks (q-bio.MN)
27 pages
Superheating and melting phenomena of a vibrated granular layer of cubic particles
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Francisco López-González, Gustavo M. Rodríguez-Liñán, Fernando Donado, Felipe Pacheco Vázquez, Luis Fernando Elizondo-Aguilera
We report the combined results of experiments and molecular dynamics simulations conducted to investigate superheating phenomena in vertically vibrated granular matter. Specifically, we consider a system of cubic particles densely packed in a square-lattice array and subjected to different shaking strengths, denoted by Gamma, approaching a critical value Gamma_c. Below Gamma_c, the superheated crystalline array remains indefinitely stable. Above Gamma_c, it transitions progressively into a granular liquid-like state over a Gamma-dependent timescale tau. We show that while an increase in frictional contacts significantly prolongs the lifetime of the superheated crystalline state, it does not play a major role in the scaling laws governing how that lifetime depends on shaking strength. Our findings also show that the transition from the superheated solid to the liquid state in the vibrated system is well described by a Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation, which is commonly used to model phase transformations in thermal systems.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
26 pages, 8 figures. Submitted to Physical Review E on July 4, 2025. This is the first version
Localization and top eigenvalue detection
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Diego Tapias, Benedikt Grüger, Reimer Kühn, Peter Sollich
The detection of the top eigenvalue and its corresponding eigenvector in ensembles of random matrices has significant applications across various fields. An existing method, based on the linear stability of a complementary set of cavity equations, has been successful in identifying the top eigenvalue when the associated eigenvector is extended. However, this approach fails when the eigenvector is localized. In this work, we adapt the real-valued cavity method to address this limitation by introducing a novel criterion that exploits the constraints of the cavity equations to detect the top eigenvalue in systems with a localized top eigenvector. Our results are validated using the Anderson model as a paradigmatic example.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech)
6 pages, 4 figures
Origin of insulating-like behavior of Bi$_2$Sr$_2$CaCu$2$O${8+x}$ under pressure: A first-principles study
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Xin Du, Jian-Feng Zhang, Zhong-Yi Lu, Kai Liu
Recent experimental study on Bi$ _2$ Sr$ _2$ CaCu$ _2$ O$ _{8+x}$ superconductors has revealed an unexpected quantum phase transition from superconducting state to insulatinglike state under pressure [Zhou et al., Nat. Phys. 18, 406 (2022)]. To better understand the physical origin of this pressure-induced phenomenon, here we have studied the structural, electronic, and magnetic properties of undoped and O-doped Bi$ _2$ Sr$ _2$ CaCu$ _2$ O$ _{8+x}$ (Bi2212) under pressures based on density-functional theory calculations. We first identified the crystal structure of undoped Bi2212 with the armchair distortions in the BiO layers and reproduced the insulating feature of the parent compound. Then we added an extra O atom to the parent compound to simulate the hole-doping effect and found that the structure with O dopant located in the van der Waals (vdW) gap is energetically the most stable. Further calculations on O-doped (0.125 holes/Cu) Bi2212 revealed that the pressure can induce charge redistributions between CuO$ 2$ planes and BiO layers; specifically, Cu-$ d{x^2-y^2}$ orbitals gain electrons and Cu atoms rather than O atoms dominate around the Fermi level under high pressure. Along with the increasing pressure, the density of states at the Fermi level first reaches the maximum at $ \sim$ 10 GPa and then shows a valley near the Fermi level above 20 GPa, which may be responsible for the insulatinglike state observed in recent experiments. We suggest that the competition among several factors, such as the increase of electrons in the CuO$ _2$ plane, the variation of in-plane hopping due to the shortened Cu-O distance, and the enhanced Coulomb repulsion among the Cu-3$ d$ electrons, could lead to the exotic transition under pressure. Our work provides an explanation of the high-pressure behaviors of Bi2212, which may facilitate a comprehensive understanding of cuprate superconductors.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
9 pages, 7 figures, 1 table
Phys. Rev. B 112, 045113 (2025)
Way More Than the Sum of Their Parts: From Statistical to Structural Mixtures
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
We show that mixtures comprised of multicomponent systems typically are much more structurally complex than the sum of their parts; sometimes, infinitely more complex. We contrast this with the more familiar notion of statistical mixtures, demonstrating how statistical mixtures miss key aspects of emergent hierarchical organization. This leads us to identify a new kind of structural complexity inherent in multicomponent systems and to draw out broad consequences for system ergodicity.
Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG), Dynamical Systems (math.DS), Statistics Theory (math.ST), Chaotic Dynamics (nlin.CD)
22 pages, 16 Figures; this http URL
Not even metastable: Cubic double-diamond in diblock copolymer melts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Micheal S. Dimitriyev, Benjamin R. Greenvall, Rejoy Matthew, Gregory M. Grason
We study the thermodynamics of continuous transformations between two canonical, cubic network phases of block copolymer melts: double-gyroid, an equilibrium morphology for many systems; and double-diamond, often thought to be a close competitor. We use a strong-segregation approach to compute the free energy of double network morphologies as a function of two structural parameters that convert between two limiting cubic cases; a tetragonal stretch of the unit cell in combination with fusion of pairs of trihedal gyroid nodes into tetrahedral diamond nodes. For the simplest case of conformationally symmetric diblock melts, we find that cubic double-diamond sits at an unstable saddle point that is continuously deformable into the lower free energy gyroid, as well as a second metastable, tetragonal network composed by trihedral nodes. We confirm the broad instability of double-diamond at finite segregation using self-consistent field studies and further show that it derives directly from the entropic free energy cost of chain packing in the tubular domains of tetrahedral nodes. Correspondingly, we demonstrate two factors that quench the entropic cost of packing in the tubular domain – homopolymer blending and elastic asymmetry between the blocks – promoting double-diamond to a metastable state by way of free energy barrier that separates it from double-gyroid.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
combined main manuscript and SI: 30 pages, 13 figures
Biexciton-polariton coupling mediated by dark states
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Giuseppe Fumero (1 and 2), Jagannath Paul (1 and 2), Jared K. Wahlstrand (3), Alan D. Bristow (1 and 2) ((1) Associate, Nanoscale Device Characterization Division, National Institute of Standards and Technology, Gaithersburg, MD, USA (2) Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA (3) Nanoscale Device Characterization Division, National Institute of Standards and Technology, Gaithersburg, MD, USA)
Multi-exciton correlations shape the photo-induced response of nanostructured materials, particularly when interactions are enhanced by light confinement. Here multidimensional coherent spectroscopy is used to quantify biexciton and exciton-polariton dynamics in a semiconductor microcavity. One- and two-quantum spectra, which are dominated by polariton-related contributions, also include a polarization-dependent biexciton feature whose magnitude and spectral coordinates depend on the detuning between the cavity mode and the exciton resonance. Comparison of spectra acquired using collinear and noncollinear experimental geometries indicates that excitation wavevector plays no significant role in this behavior. The measured energy dispersion and cavity enhancement are not compatible with uncoupled biexcitons or bipolaritons. To explain the measurements, an indirect biexciton-photon coupling model is introduced whereby biexcitons are formed from dark excitons that Coulomb couple to the bright-exciton fraction of the polaritons. The model addresses inconsistent observations of biexcitons previously reported in semiconductor microcavities and is generalizable to any material where optically dark excitons contribute to light-matter interaction. Our results suggest a mechanism to access long-lived dark excitons through multi-exciton correlations in strongly coupled systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
19 pages, 9 figures
Advancing Quantum Transport Calculations: An Effective Medium Theory with Plane-Wave Basis and PAW Potentials in Eigenstates
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Yi-Cheng Lin, Ken-Ming Lin, Yu-Chang Chen
We present an effective medium theory based on density functional theory that is implemented in VASP using the PAW method with a plane wave basis set. The transmission coefficient is derived through three complementary approaches: the current density relation J=nqv, the field operator method, and the nonquilibrium Green’s function formalism. We compare transmission coefficients calculated using EMT-PW with results from NEGF-DFT, based on the NanoDCAL package utilizing a linear combination of atomic orbitals (LCAO) basis set, for both periodic and nonperiodic boundary conditions. The minor discrepancies observed are attributed to differences in basis sets, pseudopotentials, and the treatment of lead regions. Notably, the EMT-PW framework avoids the common issue of overcompleteness encountered in non-equilibrium transport theories and allows for the decomposition of the total transmission coefficient into contributions from individual eigenstates. Furthermore, when combined with an effective gate model, EMT-PW is shown to be a powerful tool for analyzing current characteristics in nanodevices under applied gate voltages. By leveraging one-electron wavefunctions in eigenstates, this method provides a robust foundation for exploring the quantum statistics of electrons and current quantum correlations within the second quantization framework.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 Figures
High thermal conductivity dominated by thermal phonons with mean free paths exceeding hundred nanometer in three-dimensional covalent organic framework derivatives: a molecular dynamics study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Thermal properties of covalent organic frameworks (COFs) are of fundamental interest owing to exceptional heat conduction properties. Recent studies have suggested that their thermal conductivities can be enhanced by multiple factors such as pore size, mass density, and degree of chain order. However, microscopic processes that govern heat conduction properties have been explored in only a limited number of COFs. Here, we report thermal transport properties of 3D COF derivatives using molecular dynamics simulations. In this work, we have studied six different COF-102 derivatives with different organic linkers and topologies. Among the derivatives studied, we found that COF-102 derivatives with high mass density can exhibit thermal conductivity as high as ~ 27 W/mK, owing to suppressed chain rotation that leads to thermal phonons scattered by anharmonicity. Our results show that the observed orders of magnitude of increase in the thermal conductivity are primarily attributed to low frequency phonon modes that support hundreds of nanometer scale mean free path, which predominantly carry heat. Our study provides a theoretical framework that elucidates the structure-property relationship governing heat conduction in COFs, offering design strategies for thermal management applications.
Materials Science (cond-mat.mtrl-sci)
Hydrodynamic bend instability of motile particles on a substrate
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Sameer Kumar, Niels de Graaf Sousa, Amin Doostmohammadi
The emergence of hydrodynamic bend instabilities in ordered suspensions of active particles is widely observed across diverse living and synthetic systems, and is considered to be governed by dipolar active stresses generated by the self-propelled particles. Here, using linear stability analyses and numerical simulations, we show that a hydrodynamic bend instability can emerge in the absence of any dipolar active stress and solely due to the self-propulsion force acting on polar active units suspended in an incompressible fluid confined to a substrate. Specifically, we show analytically, and confirm in simulations, that a uniformly ordered state develops bend instability above a critical self-propulsion force. Numerical simulations show that a further increase in the self-propulsion strength leads the system towards a disorderly flow state. The results offer a new route for development of hydrodynamic instabilities in two-dimensional self-propelled materials that are in contact with a substrate, with wide implications in layers of orientationally ordered cells and synthetic active particles.
Soft Condensed Matter (cond-mat.soft)
10 pages, 5 figures
Promising ferroelectric metal EuAuBi with switchable giant shift current
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Guangrong Tan, Jinyu Zou, Gang Xu
The coexistence of metallicity and ferroelectricity in ferroelectric (FE) metals defies conventional wisdom and enables novel functionalities in electronic and optoelectronic systems. However, intrinsic FE metals remain extremely rare and challenging. Here, using first-principles calculations, we identify that a huge spontaneous polarization of 16.6-20.2 $ \mu\text{C}/\text{cm}^2$ , a moderate switching barrier of 68.5 meV/f.u., and a low carrier concentration of $ \sim 2.5 \times 10^{20}$ cm$ ^{-3}$ coexist in topological semimetal EuAuBi. Further electron-phonon coupling calculations reveal that the metallic carriers interact weakly with the FE phonon mode, consistent with the decoupled electron mechanism. Moreover, EuAuBi exhibits a pronounced bulk photovoltaic effect characterized by a giant polarization-dependent shift current with the magnitude of conductivity up to 370 $ \mu\text{A}/\text{V}^2$ . Thus, a feasible FE metal verification setup is proposed based on the shift current measurement. These results not only demonstrate that EuAuBi is a promising FE metal, but also propose a practical route for FE metals identification, which could promote the FE metals study greatly.
Materials Science (cond-mat.mtrl-sci)
6 pages, 3 figures
Observation of superconductivity-induced leading-edge gap in Sr-doped $\mathrm{La}{3}\mathrm{Ni}{2}\mathrm{O}_{7}$ thin films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Wenjie Sun, Zhicheng Jiang, Bo Hao, Shengjun Yan, Hongyi Zhang, Maosen Wang, Yang Yang, Haoying Sun, Zhengtai Liu, Dianxiang Ji, Zhengbin Gu, Jian Zhou, Dawei Shen, Donglai Feng, Yuefeng Nie
The discovery of high-temperature superconductivity in pressurized bulk $ \mathrm{La}{3}\mathrm{Ni}{2}\mathrm{O}{7}$ has ignited significant interest in nickelate superconductors. Unlike cuprates, where superconductivity predominantly originates from the $ \mathrm{3}d{x^2-y^2}$ orbital, nickelates exhibit additional complexities involving contributions from the $ \mathrm{3}d_{z^2}$ orbital, prompting fundamental questions about their pairing mechanisms. Despite recent progress in stabilizing superconductivity in $ \mathrm{La}{3}\mathrm{Ni}{2}\mathrm{O}{7}$ thin films at ambient pressure, direct spectroscopic evidence of the superconducting gap opening remains elusive. Here, we present an in-situ angle-resolved photoemission spectroscopy study of Sr-doped superconducting $ \mathrm{La}{3}\mathrm{Ni}{2}\mathrm{O}{7}$ thin films. Fermi surface mapping reveals Ni-$ \mathrm{3}d_{x^2-y^2}$ -derived $ \alpha$ and $ \beta$ pockets, with orbital fillings of 0.11$ \pm$ 0.02 electrons and 0.66$ \pm$ 0.03 holes per Ni, respectively, resulting in a total of 0.45$ \pm$ 0.04 electrons for each Ni. These bands exhibit moderate electron correlations, characterized by a band renormalization factor of 3-4. Notably, both $ \alpha$ and $ \beta$ bands exhibit leading-edge shifts across the superconducting transition, with gap magnitude of ~1-2 meV at Fermi momenta along the Brillouin zone diagonal and slightly away from the zone diagonal, deviating from the conventional $ d_{x^2-y^2}$ -wave gap structure. Additionally, the Ni-$ \mathrm{3}d_{z^2}$ -derived $ \gamma$ band lies ~75 meV below the Fermi level, indicating a $ \mathrm{3}d_{x^2-y^2}$ -dominated fermiology in this compound.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
18 pages and 5 figures
Probabilistic Approximate Optimization: A New Variational Monte Carlo Algorithm
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Abdelrahman S. Abdelrahman, Shuvro Chowdhury, Flaviano Morone, Kerem Y. Camsari
We introduce a generalized \textit{Probabilistic Approximate Optimization Algorithm (PAOA)}, a classical variational Monte Carlo framework that extends and formalizes prior work by Weitz \textit{et al.}~\cite{Combes_2023}, enabling parameterized and fast sampling on present-day Ising machines and probabilistic computers. PAOA operates by iteratively modifying the couplings of a network of binary stochastic units, guided by cost evaluations from independent samples. We establish a direct correspondence between derivative-free updates and the gradient of the full $ 2^N \times 2^N$ Markov flow, showing that PAOA admits a principled variational formulation. Simulated annealing emerges as a limiting case under constrained parameterizations, and we implement this regime on an FPGA-based probabilistic computer with on-chip annealing to solve large 3D spin-glass problems. Benchmarking PAOA against QAOA on the canonical 26-spin Sherrington-Kirkpatrick model with matched parameters reveals superior performance for PAOA. We show that PAOA naturally extends simulated annealing by optimizing multiple temperature profiles, leading to improved performance over SA on heavy-tailed problems such as SK-Lévy.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG), Quantum Physics (quant-ph)
Anomaly diagnosis via symmetry restriction in two-dimensional lattice systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
We describe a method for computing the anomaly of any finite unitary symmetry group $ G$ acting by finite-depth quantum circuits on a two-dimensional lattice system. The anomaly is characterized by an index valued in the cohomology group $ H^4(G,U(1))$ , which generalizes the Else-Nayak index for locality preserving symmetries of quantum spin chains. We show that a nontrivial index precludes the existence of a trivially gapped symmetric Hamiltonian; it is also an obstruction to ``onsiteability” of the symmetry action. We illustrate our method via a simple example with $ G=\mathbb{Z}_2\times\mathbb{Z}_2\times\mathbb{Z}_2\times\mathbb{Z}_2$ . Finally, we provide a diagrammatic interpretation of the anomaly formula which hints at a higher categorical structure.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph)
31 pages, 4 figures
Large unconventional anomalous Hall effect far above room temperature in epitaxial Fe$_3$Ga$_4$ films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Jing Meng, Huali Yang, Yu Shen, Kun Zheng, Hongru Wang, Yuhao Wang, Keqi Xia, Bocheng Yu, Xiaoyan Zhu, Baiqing Lv, Yaobo Huang, Jie Ma, Dariusz Jakub Gawryluk, Toni Shiroka, Zhenzhong Yang, Yang Xu, Qingfeng Zhan, Tian Shang
Noncoplanar spin textures usually exhibit a finite scalar spin chirality (SSC) that can generate effective magnetic fields and lead to additional contributions to the Hall effect, namely topological or unconventional anomalous Hall effect (UAHE). Unlike topological spin textures (e.g., magnetic skyrmions), materials that exhibit fluctuation-driven SSC and UAHE are rare. So far, their realization has been limited to either low temperatures or high magnetic fields, both of which are unfavorable for practical applications. Identifying new materials that exhibit UAHE in a low magnetic field at room temperature is therefore essential. Here, we report the discovery of a large UAHE far above room temperature in epitaxial Fe$ _3$ Ga$ _4$ films, where the fluctuation-driven SSC stems from the field-induced transverse-conical-spiral phase. Considering their epitaxial nature and the large UAHE stabilized at room temperature in a low magnetic field, Fe$ _3$ Ga$ _4$ films represent an exciting, albeit rare, case of a promising candidate material for spintronic devices.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 5 figrues; accepted version for the npj Quantum Materials
Topological electronic structures of non-collinear magnetic phases in a multi-orbital Hubbard model with spin-orbit interactions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Ying-Lin Li, Po-Hao Chou, Chung-Yu Mou
We explore topological electronic structure of magnetic phases in a multi-orbital Hubbard model with spin-orbit interactions. To account for more general antiferromagnetic orders that go beyond the collinear Néel order, two different spin-orbit interactions, Dresselhaus and Rashba spin-orbit interactions, are considered. By performing the canonical transformation, we derive the corresponding generalized t-J model. At half filling, employing self-consistent magnetic order calculations, we find distinctive spin arrangements under Dresselhaus or Rashba spin-orbit interactions. For the Dresselhaus spin-orbit interaction, the spin configuration exhibits collinear antiferromagnetic order. On the other hand, Rashba interaction results in spins antiferromagnetically aligning in xy-plane and a small interaction controlled by hopping parameter induces spin tilting, causing antiferromagnetic alignment in xy-plane but ferromagnetic alignment in z-direction. We categorize topological properties of these phases for low doping in the generalized t-J model.: for 3D collinear antiferromagnetic order, the system possesses a modified time-reversal symmetry, characterized by the Z2 index. In contrast, for systems with tilted antiferromagnetic orders, it is protected by inversion symmetry and characterized by the Z4 index. We further examine the bulk-edge correspondence for non-collinear magnetic phases, revealing that the surface state becomes gapless when the surface is parallel to the ferromagnetic component of tilted antiferromagnetic order; otherwise, the surface state exhibits a gap. Our findings offer a comprehensive topological characterization for doped and canted antiferromagnetic insulators with spin-orbit interactions, providing valuable insights into the interplay between spin arrangements, symmetries, and topological properties in systems governed by the multi-orbital Hubbard model.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 17 figures, submitted to Phys. Rev. B
Enhanced Quantum behavior on frustrated Ising model: Quantum Approximate Optimization Algorithm study
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
We investigated the quantum effects of a frustrated Ising model on a two-dimensional square lattice using the Quantum Approximate Optimization Algorithm (QAOA). While strong spin frustration is known to induce quantum fluctuations at low temperatures, previous classical approaches restricted to binary (up or down) spin configurations have been insufficient to fully capture the quantum contributions of frustration. In this study, we introduced a quantitative metric to evaluate the quantum effects arising from frustration and employed QAOA to differentiate between classical and quantum regimes. Notably, we found that in the weakly frustrated region, QAOA measurements rarely capture first excited states, as they are energetically well separated from the ground state. In contrast, near the quantum phase transition point, excited states appear more frequently in QAOA measurements, highlighting the increased role of quantum fluctuations.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
5 pages, 4 figures
Common topological origin of longitudinal and transverse magnetoresistance in Fe3GeTe2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Alapan Bera, Soumik Mukhopadhyay
In this work, we reveal the coexistence and correlation of a topological cusp anomaly in the planar Hall signal and a spin-flip scattering dominated positive longitudinal magnetoresistance (MR) across the entire temperature range below the Curie point in Fe3GeTe2. This correlation dies out exponentially as the magnetic field is directed away from the ab-plane, resulting in unusually sharp polar angle dependence of longitudinal MR and the Hall response.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Breakdown of the conventional spin-wave dynamics and its double-constraint modification in the spin-$\mathbf{\frac{1}{2}}$ triangular-prism Heisenberg antiferromagnet
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Spontaneous magnon decays in an $ S=\frac{1}{2}$ Heisenberg antiferromagnet on the equilateral triangular prism are investigated in terms of modified magnon Green’s functions. In one dimension, the so-called infrared divergence prevents us from calculating any – whether static or dynamic – structure factor within the conventional spin-wave theory even at zero temperature. The well-known modified spin-wave theory initiated by Takahashi completely fails to treat anharmonicities to cause transverse-to-longitudinal coupling which are quite characteristic of noncollinear antiferromagnets. We propose imposing a double-constraint condition on spin waves to solve all these difficulties and get a full view of the nonlinear spin-wave dynamics in one-dimensional frustrated noncollinear antiferromagnets. We reveal a novel instability of the single-particle spectrum in the absence of any well-defined magnetically ordered ground state.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech)
7 pages including 3 figures (main text) plus 13 pages including 3 figures and 2 tables (supplemental material)
In-situ SHG microscopy investigation of the domain-wall-conductivity enhancement procedure in lithium niobate
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Iuliia Kiseleva, Boris Koppitz, Elke Beyreuther, Matthias Roeper, Samuel D. Seddon, Lukas M. Eng
Conductive domain walls (CDWs) in the uniaxial ferroelectric lithium niobate (LiNbO$ _3$ , LN) have attracted a lot of interest as potential elements in 2D nanoelectronics, due to their orders-of-magnitude larger electronic AC and DC conductivities as compared to the host material. On the way towards generating standardized CDWs into z-cut bulk LN crystals with controllable geometry and electrical properties, we have encountered setbacks recently: Although the first preparation step, i.e., the established UV-light-assisted liquid-electrode poling, reliably creates fully penetrating hexagonal domains with the DWs being aligned almost parallel to the polarization axis, the second step in the DW ‘conductivity-enhancement’ process through post-growth voltage ramping, resulted in randomly-shaped DWs as reflected in their different current-voltage (I-V) characteristics even after having applied the same process parameters. To clarify this phenomenon, we present here an \textit{in-situ} and time-resolved second-harmonic-generation (SHG) microscopy investigation of DW samples of different sizes, monitoring the DW evolution during that critical voltage ramping, which allowed us to reconstruct the 3D DW shapes both prior to and after the enhancement process. As a result, we are able to map the temporal changes of the local DW inclination angle $ \alpha$ , and to quantify the DW velocity. As a consequence, we need to re-assess and re-think the origin of the DW conductivity (DWC) in LN: The hitherto assumed simple connection between $ \alpha$ and the DWC can not be generalized, since point defects accumulating along DWs act as extra sources for charge carrier trapping/release, significantly contributing to the DW current.
Materials Science (cond-mat.mtrl-sci)
14 pages, 6 figures, with appended supplementary material (11 pages, 9 figures)
Mass-transport-limited reaction rates and molecular diffusion in the van der Waals gap beneath graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Hossein Mirdamadi, Jiří David, Rui Wang, Tianle Jiang, Yanming Wang, Karel Vařeka, Michal Dymáček, Petr Bábor, Tomáš Šikola, Miroslav Kolíbal
The confinement of molecules within the van der Waals (vdW) gap between a two-dimensional 2D material and a catalytic substrate offers a promising route toward the development of molecule-selective catalysts with increased reaction rates. However, identifying the kinetic limitations of such confined reactions remains challenging. Here, we employ an inverted wedding-cake configuration of multilayer graphene on platinum to study the dynamics of graphene etching in the vdW gap by various molecules (O2, H2, and CO), using in situ scanning electron microscopy. Under the experimental conditions explored (up to p = 1.4x10-3 Pa and T = 1000 °C), the etching reaction rates are limited by mass transport within the confined space. This limitation persists even for CO, despite its anomalously enhanced transport resulting from a significant lifting of the vdW gap. Reactive molecular dynamics simulations further reveal multiple etching pathways for CO, enabled by confinement within the vdW space. Once mass-transport limitations are overcome, the vdW gap acts as an effective nanoreactor, facilitating reaction pathways that would be otherwise inaccessible on a pristine surface without spatial confinement.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
38 pages including Supporting Information, 5 figures in the main text, 10 figures in SI
Vestigial Order Melting of a Chiral Atomic Superfluid in a Double-Valley Optical Lattice
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-11 20:00 EDT
Zhongcheng Yu, Chengyang Wu, Chi Zhang, Xiaopeng Li, Xiaoji Zhou
Quantum simulations of vestigial orders in multi-orbital superfluids have been attracting continuous research interests in both cold atoms and condensed matter systems, as it provides valuable insights into the high-temperature superconductivity. Here, we experimentally investigate thermal phase transitions in a Floquet-engineered double-valley bandstructure realized with ultracold bosonic atoms in a shaken optical lattice. The system exhibits both U(1) and time-reversal $ \mathbb{Z}_2$ symmetries, and in the ground state, it forms a chiral superfluid with the Bose-Einstein condensation at a single this http URL tuning the temperature, we observe a vestigial order melting of the chiral superfluid: first into a paramagnetic superfluid, and then into a normal phase. We measure the superfluid and Ising transition temperatures across a range of driving frequencies, and find that the critical temperature of the superfluid transition is always higher than that of Ising transition within the studied frequency range. As the frequency approaches the resonance, the Ising transition temperature decreases, while the superfluid transition temperature remains almost unaffected. The two phase transitions merge into a single transition at far detuning. Our experimental results imply rich quantum many-body physics as an interplay of quantum and thermal fluctuations in periodically driven quantum systems.
Quantum Gases (cond-mat.quant-gas)
Pseudogap in a crystalline insulator doped by disordered metals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Sae Hee Ryu, Minjae Huh, Do Yun Park, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Keun Su Kim
A key to understand how electrons behave in crystalline solids is the band structure that connects the energy of electron waves to their wavenumber (k). Even in the phase of matter with only short-range order (liquid or amorphous solid), the coherent part of electron waves still possesses a band structure. Theoretical models for the band structure of liquid metals were formulated more than 5 decades ago, but thus far, bandstructure renormalization and pseudogap induced by resonance scattering have remained unobserved. Here, we report the observation of this unusual band structure at the interface of a crystalline insulator (black phosphorus) and disordered dopants (alkali metals). We find that a conventional parabolic band structure of free electrons bends back towards zero k with the pseudogap of 30-240 meV from the Fermi level. This is k renormalization caused by resonance scattering that leads to the formation of quasi-bound states in the scattering potential of alkali-metal ions. The depth of this potential tuned by different kinds of alkali metal (Na, K, Rb, and Cs) allows to classify the pseudogap of p-wave and d-wave resonance. Our results may provide a clue to the puzzling spectrum of various crystalline insulators doped by disordered dopants, such as the waterfall dispersion in cuprates.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
Nature 596, 68-73 (2021)
Electronic rotons and Wigner crystallites in a two-dimensional dipole liquid
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Soobin Park, Minjae Huh, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Keun Su Kim
A key concept proposed by Landau to explain superfluid liquid helium is the elementary excitation of quantum particles called rotons. The irregular arrangement of atoms in a liquid forms the aperiodic dispersion of rotons that played a pivotal role in understanding fractional quantum Hall liquid (magneto-rotons) and the supersolidity of Bose-Einstein condensates. Even for a two-dimensional electron or dipole liquid in the absence of a magnetic field, their repulsive interactions were predicted to form a roton minimum that can be used to trace the transition to Wigner crystals and superconductivity, but it has not been observed. Here, we report the observation of such electronic rotons in a two-dimensional dipole liquid of alkali-metal ions doping charges to surface layers of black phosphorus. Our data reveal a striking aperiodic dispersion of rotons characterized by a local minimum of energy at a finite momentum. As the density of dipoles decreases, where interactions dominate over kinetic energy, the roton gap reduces to 0 as in crystals, signalling Wigner crystallisation. Our model shows the importance of short-range order arising from repulsion between dipoles, which can be viewed as the formation of Wigner crystallites (bubbles or stripes) floating in the sea of Fermi liquids. Our results reveal that the primary origin of electronic rotons (and the pseudogap) is strong correlations.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
Nature 634, 813-817 (2024)
Dark states of electrons in a quantum system with two pairs of sublattices
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Yoonah Chung, Minsu Kim, Yeryn Kim, Seyeong Cha, Joon Woo Park, Jeehong Park, Yeonjin Yi, Dongjoon Song, Jung Hyun Ryu, Kimoon Lee, Timur K. Kim, Cephise Cacho, Jonathan Denlinger, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Keun Su Kim
A quantum state of matter that is forbidden to interact with photons and is therefore undetectable by spectroscopic means is called a dark state. This basic concept can be applied to condensed matter where it suggests that a whole band of quantum states could be undetectable across a full Brillouin zone. Here we report the discovery of such condensed matter dark states in palladium diselenide as a model system that has two pairs of sublattices in the primitive cell. By using angle-resolved photoemission spectroscopy, we find valence bands that are practically unobservable over the whole Brillouin zone at any photon energy, polarisation, and scattering plane. Our model shows that two pairs of sublattices located at half-translation positions and related by multiple glide-mirror symmetries make their relative quantum phases polarised into only four kinds, three of which become dark due to double destructive interference. This mechanism is generic to other systems with two pairs of sublattices, and we show how the phenomena observed in cuprates, lead-halide perovskites, and density wave systems can be resolved by the mechanism of dark states. Our results suggest that the sublattice degree of freedom, which has been overlooked so far, should be considered in the study of correlated phenomena and optoelectronic characteristics.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Nature Physics 20, 1582-1588 (2024)
Phase transitions and spontaneous symmetry breaking in the renormalized Ginzburg-Landau theory
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Feulefack Ornela Claire, Tsague Fotio Carlos, Keumo Tsiaze Roger Magloire
In this study, we present theoretical investigations of phase transitions and critical phenomena in materials through the lens of second-order Ginzburg-Landau theory, in conjunction with considerations of symmetry groups and thermal fluctuations. By addressing the residual effects after a renormalization process, a small number of macroscopic degrees of freedom can effectively replace the infinite number of microscopic degrees of freedom, emphasizing the significant role of dimensionality and the intrinsic characteristics of the system in understanding and analyzing transitions. We highlight several non-universal characteristics of continuous phase transitions near the transition temperature, including the non-monotonic relationship between the critical temperature and dimensionality, as well as the enhancement or disappearance of the specific heat jump in complex superconductors. While the resulting expressions for thermodynamic quantities are complex for one-dimensional systems, obeying Mermin-Wagner’s theorem, they are considerably simplified for two-dimensional and three-dimensional systems.
Superconductivity (cond-mat.supr-con)
AMS-LaTeX v1.5, 11 pages with 3 figures
Evolution from intralayer to interlayer superconductivity in a bilayer $t$-$J$ model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Yuan Yang, Xin Lu, Yuan Wan, Wei-Qiang Chen, Shou-Shu Gong
Motivated by the bilayer cuprate superconductors and nickelate superconductor La$ 3$ Ni$ 2$ O$ 7$ , we investigate the evolution from intralayer to interlayer superconductivity based on a bilayer two-leg $ t$ -$ J$ -$ J{\bot}$ model, where $ t$ is the in-plane electron hopping, $ J$ is the in-plane spin interaction, and $ J{\bot}$ is the inter-plane spin interaction. By means of the density matrix renormalization group calculations, we obtain the quantum phase diagram of the system by tuning $ J{\bot}$ in a large doping range $ \delta = 1/8 - 1/2$ . We find that a large $ J_{\bot}$ can always drive an interlayer superconductivity by coupling the two layers in both the Luther-Emery liquid and Luttinger liquid states. By coupling two Luther-Emery liquid states, the in-plane superconductivity evolves to inter-plane superconductivity either through an intermediate charge density wave (CDW) phase or directly, depending on doping ratio. This emergent CDW phase, which exists over a finite doping range, appears to develop from the CDW state of the two-leg ladder at $ \delta = 1/4$ . By coupling two Luttinger liquids, the in-plane Luttinger liquids show a transition to the inter-plane superconducting phase at large $ J_{\bot}$ , as reported in previous literature. Interestingly, in the intermediate $ J_{\bot}$ regime we find that while the in-plane Luttinger-liquid features remain stable, the inter-plane superconductivity can develop an enhanced quasi-long-range order with the power exponent $ K^{zz}{\rm SC} \sim 1$ . At last, we show that the interlayer superconductivity is also stable by coupling the bilayer three-leg $ t$ -$ J$ ladders by a strong $ J{\bot}$ interaction, from both the Luther-Emery liquid and Luttinger-liquid states.
Strongly Correlated Electrons (cond-mat.str-el)
Altermagnetic Multiferroics: Symmetry-Locked Magnetoelectric Coupling
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Wei Sun, Changhong Yang, Xiaotian Wang, Shifeng Huang, Zhenxiang Cheng
Multiferroics exhibit significant potential for low-power spintronic devices due to magnetoelectric coupling. Here, we discuss an emerging class of altermagnetic multiferroics, a system demonstrating distinct advantages including zero net magnetization (eliminating stray fields), momentum-dependent spin splitting (enabling electric-field control of spin currents), and intrinsic strong magnetoelectric coupling originating from spin-space symmetry.
Materials Science (cond-mat.mtrl-sci)
Strain-Stabilized Interfacial Polarization Tunes Work Function Over 1 eV in RuO2/TiO2 Heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Seung Gyo Jeong, Bonnie Y.X. Lin, Mengru Jin, In Hyeok Choi, Seungjun Lee, Zhifei Yang, Sreejith Nair, Rashmi Choudhary, Juhi Parikh, Anand Santhosh, Matthew Neurock, Kelsey A. Stoerzinger, Jong Seok Lee, Tony Low, Qing Tu, James M. LeBeau, Bharat Jalan
Interfacial polarization-charge accumulation at the heterointerface-is a well-established tool in semiconductors, but its influence in metals remains unexplored. Here, we demonstrate that interfacial polarization can robustly modulate surface work function in metallic rutile RuO2 layers in epitaxial RuO2/TiO2 heterostructures grown by hybrid molecular beam epitaxy. Using multislice electron ptychography, we directly visualize polar displacements of transition metal ions relative to oxygen octahedra near the interface, despite the conductive nature of RuO2. This interfacial polarization enables over 1 eV modulation of the RuO2 work function, controlled by small thickness variation (2-4 nm) as measured by Kelvin probe probe microscopy, with a critical thickness of 4 nm - corresponding to the transition from fully strained to relaxed film. These results establish interfacial polarization as a powerful route to control electronic properties in metals and have implications for designing tunable electronic, catalytic, and quantum devices through interfacial control in polar metallic systems.
Materials Science (cond-mat.mtrl-sci)
25 pages, 4 figures
Nodeless superconductivity in 4H${b}$-TaS${2}$ with broken time reversal symmetry
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Yuwei Zhou, Fanyu Meng, Yanen Huang, Jiawen Zhang, Jin Zhan, Ye Chen, Yu Liu, Hechang Lei, Michael Smidman, Huiqiu Yuan
The transition metal dichalcogenide 4H$ _{b}$ -TaS$ _{2}$ exhibits characteristics of topological edge modes and two-component superconductivity with time-reversal symmetry breaking (TRSB). The nature of the superconducting order parameter is a crucial issue that requires experimental investigation. Here, we report measurements of the magnetic penetration depth using a tunnel-diode-oscillator based technique, as well as the specific heat. Both the specific heat and the change in magnetic penetration depth ($ \Delta$ \lambda$ (T)) display an exponentially-activated temperature dependence, providing evidence for nodeless superconductivity in 4H$ _{b}$ -TaS$ _{2}$ . Moreover, the deduced superfluid density can be well described by a two-gap $ s$ -wave model, and such multigap superconductivity is consistent with there being multiple bands crossing the Fermi energy. These results constrain the possible pairing symmetries of 4H$ _{b}$ -TaS$ _{2}$ .
Superconductivity (cond-mat.supr-con)
7 pages, 4 figures
Phys. Rev. B 112, 014507 (2025)
Master equations for continuous-time random walks with stochastic resetting
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Fausto Colantoni, Gianni Pagnini
We study a general continuous-time random walk (CTRW), by including non-Markovian cases and Lévy flights, under complete stochastic resetting to the initial position with an arbitrary law, which can be power-lawed as well as Poissonian. We provide three linked results. First, we show that the random walk under stochastic resetting is a CTRW with the same jump-size distribution of the non-reset original CTRW but different counting process. Later, we derive the condition for a CTRW with stochastic resetting to be a meaningful displacement process at large elapsed times, i.e., the probability to jump to any site is higher than the probability to be reset to the initial position, and we call this condition the zero-law for stochastic resetting. This law joins with the other two laws for reset random walks concerning the existence and the non-existence of a non-equilibrium stationary state. Finally, we derive master equations for CTRWs when the resetting law is a completely monotone function.
Statistical Mechanics (cond-mat.stat-mech), Probability (math.PR)
The equilibrium distribution function for strongly nonlinear systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Jialin Zhang, Yong Zhang, Hong Zhao
The equilibrium distribution function determines macroscopic observables in statistical physics. While conventional methods correct equilibrium distributions in weakly nonlinear or near-integrable systems, they fail in strongly nonlinear regimes. We develop a framework to get the equilibrium distributions and dispersion relations in strongly nonlinear many-body systems, incorporating corrections beyond the random phase approximation and capturing intrinsic nonlinear effects. The theory is verified on the nonlinear Schrodinger equation, the Majda-McLaughlin-Tabak model, and the FPUT-beta model, demonstrating its accuracy across distinct types of nonlinear systems. Numerical results show substantial improvements over existing approaches, even in strong nonlinear regimes. This work establishes a theoretical foundation for equilibrium statistical properties in strongly nonlinear systems.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Chaotic Dynamics (nlin.CD), Classical Physics (physics.class-ph)
6 pages, 4 figures
Emergent QED$_3$ at the bosonic Laughlin state to superfluid transition
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Taige Wang, Xue-Yang Song, Michael P. Zaletel, T. Senthil
Quantum phase transitions between topologically ordered and symmetry-broken phases lie beyond Landau theory. A prime example is the conjectured continuous transition from the bosonic $ \nu = 1/2$ Laughlin state to a superfluid, proposed to be governed by a QED$ _3$ –Chern–Simons (CS) critical point whose stability remains uncertain. We study half-filled bosons in the lowest Landau level subject to a lattice potential. Infinite-cylinder DMRG reveals a single continuous Laughlin–to–superfluid transition. Adiabatic flux insertion collapses the many-body gap and exposes massless Dirac quasiparticles, while momentum-resolved correlation lengths show that three lattice-related density modes share the same critical exponent, evidencing an emergent $ SO(3)$ symmetry. The joint appearance of Dirac dispersion and symmetry enlargement provides microscopic support for a stable QED$ _3$ –CS fixed point. Our numerical strategy also offers a blueprint for exploring Landau-forbidden transitions in fractional Chern insulators and composite Fermi liquids realised in moire and cold-atom systems.
Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 8 figures
First-principles analysis of the effect of magnetic states on the oxygen vacancy formation energy in doped La${0.5}$Sr${0.5}$CoO$_3$ perovskite
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Wei Wei, Florian Fuchs, Andreas Zienert, Xiao Hu, Jörg Schuster
Oxygen vacancies are critical for determining the electrochemical performance of fast oxygen ion conductors. The perovskite La$ _{0.5}$ Sr$ _{0.5}$ CoO$ _3$ , known for its excellent mixed ionic-electronic conduction, has attracted significant attention due to its favorable vacancy characteristics. In this study, we employ first-principles calculations to systematically investigate the impact of 3$ d$ transition-metal doping on the oxygen vacancy formation energies in the perovskite. Two magnetic states, namely the ferromagnetic and paramagnetic states, are considered in our models to capture the influence of magnetic effects on oxygen vacancy energetics. Our results reveal that the oxygen vacancy formation energies are strongly dependent on both the dopant species and the magnetic state. Notably, the magnetic states alter the vacancy formation energy in a dopant-specific manner due to double exchange interactions, indicating that relying solely on the ferromagnetic ground state may result in misleading trends in doping behavior. These findings emphasise the importance of accounting for magnetic effects when investigating oxygen vacancy properties in perovskite oxides.
Materials Science (cond-mat.mtrl-sci)
Strain-tunable type-II to type-III & Gimbal nodal line transition in Imm2-phase of Cu$_2$SnS$_3$: An ab-initio study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Prakash Pandey, Sudhir K. Pandey
Topological nodal line semimetals (NLSMs) represent an intriguing quantum phase, opening new avenues in materials science for practical applications such as anisotropic transport devices, high-mobility conductors, unconventional thermoelectrics, and nonlinear optical devices. Recently, Cu$ _2$ SnS$ _3$ has been theoretically proposed as a type-II NLSM, with its Fermi surface containing only one nodal ring. Here, we demonstrate how uniaxial, equi-biaxial, and equi-triaxial strains affect the nodal line state of the $ Imm2$ -phase of Cu$ _2$ SnS$ _3$ by using state-of-the-art ab-initio calculations. Under the application of uniaxial compressive strain (UCS) along the a-direction, the plane of the nodal line evolves from the $ k_x$ -$ k_z$ to $ k_y$ -$ k_z$ for 6%$ \leq$ UCS$ \leq$ 8%. In contrast, under uniaxial tensile strain (UTS), the nodal line remains in the ($ k_x$ -$ k_z$ ) plane across the entire studied range of UTS. Interestingly, on the application of equi-biaxial tensile strain (EBTS) along a-b (a-c) directions, it hosts only one nodal ring below 8% ($ <$ 6%), which further evolves into three (seven) nodal-ring for EBTS of 8% (6%$ \leq$ EBTS$ \leq$ 8%). Upon the application of EBTS along a-c directions, we found two sets of three mutually orthogonal, intersecting nodal loops (topological gimbals). Apart from this, under the application of equi-biaxial compressive strain (EBCS) along the a-b (a-c) directions, it exhibits only one nodal ring up to 8% (7%). Beyond this, the nodal line completely vanishes and does not reappear at higher values of EBCS. Under equi-triaxial tensile strain (ETTS), Cu$ _2$ SnS$ _3$ exhibits only one nodal-ring $ <$ 6%, which subsequently transforms into five nodal-ring for 6%$ \leq$ ETTS$ \leq$ 8%. However, under the application of equi-triaxial compressive strain (ETCS), as in EBCS, only one nodal line exists up to 6% ETCS.
Materials Science (cond-mat.mtrl-sci)
Resilient cluster Mott states in layered Nb$_3$Cl$_8$ against pressure-induced symmetry breaking
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Hongbin Qu, Xiaoqun Wang, Hai-Qing Li, ang Gang Li
In this work, by combining density-functional theory (DFT) with dynamical mean-field calculations (DMFT), we compare the crystal and electronic structures of the prototype cluster Mott insulator Nb$ _{3}$ Cl$ 8$ at ambient and high-pressure. We explain the finite but significantly reduced charge gap experimentally observed at $ P=9.7$ GPa. We reveal a local symmetry breaking of the Nb$ {3}$ trimer under pressure, reducing its symmetry from $ C{3v}$ to $ C{s}$ . This leads to a strong bandwidth enhancement and a lift of band degeneracy. Crucially, despite the significant change of band details, the cluster Mott insulating state is robust against local symmetry breaking. We show that the experimental observed gap under pressure is still a cluster Mott gap and its reduced value stems from both increased bandwidth and reduced Coulomb interactions under pressure. Our study provides the first systematic theoretical elucidation of how pressure-induced symmetry breaking dictates the cluster Mott state, establishing a robust foundation for understanding the intricate relationship between symmetry, local/non-local correlations, and emergent quantum states in correlated cluster compounds.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
6 pages and 4 figures
Geometry-Dependent Adhesion in Transparent, Monodomain Liquid Crystal Elastomers
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Aidan Street, Devesh Mistry, Johan Mattsson, Helen F. Gleeson
Elastomeric pressure-sensitive adhesives (PSAs) form adhesive bonds under light pressure. Liquid crystal elastomers (LCEs) are exciting PSA candidates as they can impart both anisotropy and temperature-dependence to adhesion, but the full potential of their anisotropic adhesion is unexplored. Here, identical side-chain LCEs, produced as transparent isotropic or nematic films are investigated; the latter aligned in homeotropic or planar geometries. Their room-temperature adhesion, determined through a 90-degree peel test, is consistent with theoretical predictions and strongest in a planar geometry (peeled parallel to the director) with adhesive force per unit length of 0.67 Nmm-1. In contrast, adhesion of the planar perpendicular, isotropic and homeotropic films is 62.5%, 38.5% and 23.0% lower, respectively. The surface contribution to adhesion is identical for all films, confirming that the variation in adhesion is determined solely by the bulk LCE alignment controlled during film preparation. A temperature-dependent adhesion factor is determined from 0 Celsius to 80 Celsius using dynamic mechanical analysis, and found to be in excellent agreement with the peel data at room temperature. Molecular relaxations active above the glass transition temperature are dominant in determining LCE adhesion. The results show that side-chain LCEs can function as transparent, tunable, broad-temperature smart PSAs
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
19 pages, 8 figures, 2 tables
Summing Real Time Feynman Paths of Lattice Polaron with Matrix Product States
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
We study numerically the real time dynamics of lattice polarons by combining the Feynman path integral and the matrix product state (MPS) approach. By constructing and solving a flow equation, we show that the integrand, viewed as a multivariable function of polaron world line parameters, can be compressed as a low bond dimension MPS, thereby allowing for efficient evaluation of various dynamical observables. We establish the effectiveness of our method by benchmarking the calculated polaron spectral function in one dimension against available results. We further demonstrate its potential by presenting the polaron spectral function in two dimensions and simulating polaron diffusion in both one and two dimensions.
Strongly Correlated Electrons (cond-mat.str-el)
15 pages, 9 figures
Pressure induced ferromagnetic to antiferromagnetic phase transition in transition metal chalcogenide Cr$_{3}$Te$_4$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Asish Kumar Mishra, Souvick Chakraborty, Bidisha Mukherjee, Mrinmay Sahu, Suvashree Mukherjee, Shubham Purwar, Harekrishna Bhunia, S. Thirupathaiah, Peter Liermann, Satyabrata Raj, Goutam Dev Mukherjee
We have carried out a detailed high-pressure investigation on the strongly correlated transition metal chalcogenide $ Cr_{3}Te_4$ using Raman spectroscopy and XRD, which is ferromagnetic and metallic at ambient conditions. We find that the monoclinic structure remains stable up to 30 GPa, the highest pressure studied. The Cr-Te bond length and octahedral volume decrease drastically up to 7.6 GPa pressure. The $ A_{1g}$ Raman mode shows a red shift up to 7.6 GPa, and the $ E_g$ Raman mode shows a sudden drop around the same pressure. Further low-temperature Raman spectroscopic investigation shows that the Raman modes soften at the ferromagnetic to antiferromagnetic phase transition. This suggests a change in the magnetic ordering at high pressure. Our Density Functional Theory (DFT) calculations reveal the change in magnetic ground state from ferromagnetic state to antiferromagnetic state above 7.6 GPa pressure, corroborating our experimental result.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Exotic collective dynamics in molten Carbon
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Taras Bryk, Giancarlo Ruocco, Jean-François Wax, Noël Jakse
Collective longitudinal and transverse propagating modes in molten Carbon at $ T=5500$ ~K and pressure range $ 10$ -$ 40$ GPa are reported from {\it ab initio} based as well as machine learned molecular dynamics. A striking exotic feature in collective dynamics is the two-peak shape of the current spectral functions of the single-component liquid, which makes evidence of a second branch of longitudinal propagating modes in the wave number range $ k>1$ Å$ ^{-1}$ . It is shown that time correlation functions reflecting the out-of-phase motion of particles and their cages of nearest neighbors results in the same frequencies of the exotic low-frequency branch of vibrations. A theoretical framework of generalized collective modes is applied to recover the time dependence of density-density, imaginary part of susceptibility and longitudinal current-current correlations.
Statistical Mechanics (cond-mat.stat-mech)
12
A comprehensive study of bond bipolaron superconductivity in triangular lattice
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
We employ the diagrammatic Monte Carlo method with a lattice path-integral formulation for both electron and phonon degrees of freedom to investigate the formation and properties of bond polarons and bipolarons on a two-dimensional triangular lattice. In the adiabatic regime ($ \omega/t < 1.0$ ), single polarons remain light with a small effective mass, while bipolarons remain compact and lightweight, resulting in a high superfluid transition temperature $ T_c$ . We systematically study the dependence of $ T_c$ on electron-phonon coupling strength and on-site interaction in the bond bipolaron model. Our results show that a moderate on-site repulsion enhances $ T_c$ by stabilizing compact yet lightweight bipolarons, leading to high-$ T_c$ superconductivity in the dilute limit. Notably, the triangular lattice sustains relatively high $ T_c$ across a wide range of phonon frequencies, outperforming square lattice geometry. This enhancement arises from the higher coordination number and the bond-centered nature of the electron-phonon coupling. These findings suggest that triangular lattice geometry offers a promising platform for realizing high-$ T_c$ bipolaronic superconductivity.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
9 pages, 9 figures
Universal Spin Models are Universal Approximators in Machine Learning
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Tobias Reinhart, Gemma De les Coves
One of the theoretical pillars that sustain certain machine learning models are universal approximation theorems, which prove that they can approximate all functions from a function class to arbitrary precision. Independently, classical spin models are termed universal if they can reproduce the behavior of any other spin model in their low energy sector. Universal spin models have been characterized via sufficient and necessary conditions, showing that simple models such as the 2d Ising with fields are universal. In this work, we prove that universal spin models are universal approximators of probability distributions. As a consequence, the characterization of the former gives rise to universal approximation theorems for the latter. This allows us to derive new proofs of universal approximation theorems for restricted and deep Boltzmann machines, as well as deep belief networks. This work illustrates that independently discovered universality statements may be intimately related, enabling the transfer of results.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
6 pages, 2 figures
Extracting Nonlinear Dynamical Response Functions from Time Evolution
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
We develop a general framework based on the functional derivative to extract nonlinear dynamical response functions from the temporal evolution of physical quantities, without explicitly computing multipoint correlation functions. We validate our approach by calculating the second- and third-order optical responses in the Rice-Mele model and further apply it to a many-body interacting system using a tensor network method. This framework is broadly applicable to any method that can compute real-time dynamics, offering a powerful and versatile tool for investigating nonlinear responses in dynamical systems.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Optics (physics.optics), Quantum Physics (quant-ph)
18 pages, 6 figures (including End Matter and Supplemental Material)
Phys. Rev. Lett. 135, 026401 (2025)
Temporal modulation of second harmonic generation in ferroelectrics by a pulsed electric field
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
We revisit the relationship between electric polarization modulation $ \Delta P$ in ferroelectrics induced by a low-frequency pulsed electric field and the corresponding second harmonic intensity modulation $ \Delta I_{\mathrm{SH}}$ . Using nonlinear response theory, we derive their time-domain expressions linear in the pulse amplitude, revealing that not only the electric field but also its time derivative contributes to $ \Delta I_{\mathrm{SH}}$ . Furthermore, even when the time-derivative component is negligible, $ \Delta I_{\mathrm{SH}}$ can be in antiphase with the pulsed field and thus with $ \Delta P$ . These theoretical predictions are further supported by real-time simulations of a model for electronic ferroelectrics. Our results demonstrate that the commonly assumed relation $ \Delta P \propto \Delta I_{\mathrm{SH}}$ can break down under certain conditions, reflecting the complex-valued and frequency-dependent nature of nonlinear dynamical susceptibilities.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Optics (physics.optics)
11 pages, 5 figures
Quench spectroscopy for Lieb-Liniger bosons in the presence of harmonic trap
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-11 20:00 EDT
Jiachen Yu, Yuanzhe Hu, Wenhan Chen, Jianing Yang, Xuzong Chen, Hepeng Yao
Quench spectroscopy has emerged as a novel and powerful technique for probing the energy spectrum of various quantum phases for quantum systems from out-of-equilibrium dynamics. While its efficacy has been demonstrated in the homogeneous systems theoretically, most experimental setups feature a confining potential, such as a harmonic trap, which complicates the practical implementations. In this work, we experimentally probe the quench spectroscopy for one-dimensional bosons in optical lattices with the presence of a harmonic trap, and comparing our results with the density matrix renormalization group simulation. For the Mott insulator phase, although a gap is still observed, the band signal is broadened along the frequency space and cut at the half Brillouin zone, which can be explained by the excitations under harmonic confinement. Comparing with the superfluid spectrum, we can see a clear distinction between the two phases and find the inverse quench with larger amplitude yields the clearest spectrum. Our work offers pivotal insights into conducting quench spectroscopy effectively in practical systems.
Quantum Gases (cond-mat.quant-gas)
Crossing over from flat band superconductivity to conventional superconductivity
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Over the past ten years, flat band (FB) or geometric superconductivity has become a major issue in condensed matter physics due to the significant technological benefits it could offer. Observations of this unconventional form of superconductivity are unfortunately still very limited, and significant efforts are being made to search for candidate materials. Most existing theoretical studies focus on systems with strictly non-dispersive bands, which, from an experimental point of view, represents an extremely difficult technological constraint to achieve. It is therefore crucial to understand to what extent this constraint can be relaxed. In other words, to what extent can superconductivity in flat bands survive weak perturbations? The main objective of the present study is precisely to answer this essential question in detail.
Superconductivity (cond-mat.supr-con)
9 pages, 8 figures
Superlubricity of Borophene: Tribological Properties in Comparison to hBN
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Antoine Hinaut, B. Sena Tömekçe, Shuyu Huang, Yiming Song, Ernst Meyer, Antonio Cammarata, Willi Auwärter, Thilo Glatzel
The tribological performance of 2D materials makes them good candidates toward a reduction of friction at the macroscale. Superlubricity has been observed for graphene, MoS\textsubscript{2} and MXenes and hexagonal boron nitride (hBN) is used to reduce or tune friction, but other materials are investigated as potential candidates for low-lubricity applications. Specifically, borophene is predicted to have ultra-low friction. Here, we experimentally investigate frictional properties of borophene and use a borophene-hBN lateral heterostructure to directly compare the tribological properties of the two complementary 2D materials. In particular, we investigate the friction between a sliding tip and (i) the weakly corrugated $ \mathcal{X}_6$ -borophene layer on Ir(111) or (ii) the hBN/Ir(111) superlattice structures with a strongly corrugated moiré reconstruction. Our experimental study performed in ultra-high vacuum at room temperature combined with a Prandtl-Tomlinson (PT) model calculation confirms the superlubricity predicted for borophene, while hBN, which exhibits a higher friction, is nevertheless confirmed as a low friction material. Ab initio calculations show that the lower friction of $ \mathcal{X}_6$ -borophene with respect to hBN can be rationalized by weaker tip/surface interactions. In addition, we assess structural and electrical properties of borophene and hBN by using scanning probe techniques and compare their dissipation under the oscillating tip to investigate the possible path of energy dissipation occurring during friction. Our study demonstrates the low frictional properties of borophene and the potential of lateral heterostructure investigations to directly compare the properties of these 2D materials.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
In situ impedance spectroscopy tests of Li${4-x}$Ge${1-x}$P$_x$O$_4$ as potential solid state electrolyte for Micro Li ion Batteries
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Mohammadhossein Montazerian, Kyle J. Stephens, Vladimir Roddatis, Christof Vockenhuber, Arnold Müller, Anders J. Barlow, Thomas Lippert, Nick A. Shepelin, Daniele Pergolesi
Lithium-ion batteries employing solid-state electrolytes (SSEs) are emerging as a safer and more compact alternative to conventional batteries using liquid electrolytes, especially for miniaturized energy storage systems. However, the industry-standard SSE, LiPON, imposes limitations due to its incompatibility with high-temperature processing. In this study, we investigate Li$ _{4-x}$ Ge$ _{1-x}$ P$ _x$ O$ _4$ (LGPO), a LISICON-type oxide, as a promising alternative thin-film SSE. LGPO thin films are fabricated using pulsed laser deposition under four distinct deposition conditions, with in situ impedance spectroscopy enabling precise conductivity measurements without ambient exposure. We systematically correlate deposition temperature, background pressure, chemical composition, crystallinity, and morphology with ionic transport properties. Polycrystalline LGPO films grown at high temperature (535 $ ^\circ$ C) and low oxygen pressure (0.01 mbar) exhibited the highest room-temperature ionic conductivity ($ \sim 1.2 \times 10^{-5}$ S cm$ ^{-1}$ ), exceeding that of LiPON by an order of magnitude, with an activation energy of 0.46 eV. In contrast, amorphous films show significantly lower conductivity ($ \sim 5.2 \times 10^{-8}$ S cm$ ^{-1}$ ) and higher activation energy (0.72 eV). The results reveal that crystallinity, chemical composition, and grain boundary density critically affect ion transport, highlighting the importance of microstructural control. This work establishes LGPO as a viable, high-performance oxide SSE compatible with high-temperature processing for next-generation microbattery architectures.
Materials Science (cond-mat.mtrl-sci)
19 pages, 5 figures
Muonium as a probe of point defects in type-Ib diamond
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
K. Yokoyama, J.S. Lord, H. Abe, T. Ohshima
Muonium (Mu), a bound state of a positively charged muon and an electron, can diffuse through crystal lattices and interact with defect centers in insulators and semiconductors. We demonstrate that this Mu’s diffusive property can be used to probe defects in a diamond crystal lattice; specifically, substitutional nitrogen atoms (N$ _\text{s}^0$ ) and nitrogen-vacancy (NV) centers in type-Ib diamond. Upon interaction with these defects, Mu can exchange its electron’s spin or change its charge state, which result in muon spin relaxation. However, muons in diamond (and semiconductors in general) can be in a few distinctive muonium states, with each state contributing to the muon signal. In addition, these states can undergo site and charge exchange interaction, forming a dynamic network. Hence, to study the Mu interaction with point defects, the muon data have to be deconvoluted to isolate signals from the diffusing species. To achieve this goal, we have modeled the Mu state exchange dynamics and numerically simulated the time evolution of muon spin polarization by the density matrix method. With a global curve fit to a set of longitudinal field scan data, one can extract the Mu transition rates that involve interaction with the defect centers. The diffusing tetrahedral interstitial Mu was found to interact with the paramagnetic N$ _\text{s}^0$ center via electron spin exchange. In contrast, they are converted to form a diamagnetic center upon interaction with the negatively charged NV center.
Materials Science (cond-mat.mtrl-sci)
7 pages, 3 figures, 1 table
A Semi-Empirical Descriptor for Open Circuit Voltage
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Sourav Baiju, Mark Huijben, Payam Kaghazhi
Layered transition metal oxides (TMO) are widely used as cathode materials in Na/Li batteries. The open-circuit voltage (OCV), which determines the energy density (together with capacity), is among the key physical and chemical factors influencing the performance of cathodes. The shape of the voltage profile is also influenced by the formation energy of intermediate phases during cycling. From a theoretical perspective, the formation energy (and voltage) are defined as internal energy differences between phases. Therefore, an accurate prediction of internal energy is crucial for the calculation of OCV. In this work, we present a theoretical framework that decomposes the internal energy of a given TMO into distinct contributions with clear physical significance. Specifically, we break down the energy into parameters that can be more easily calculated (compared to DFT) and obtained from experimental databases. From these parameters, we define a potential term that can be calculated for different compositions, and can be used for calculation of voltage profile
Materials Science (cond-mat.mtrl-sci)
Energy Efficient p-Circuits for Generative Neural Networks
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Lakshmi A. Ghantasala, Ming-Che Li, Risi Jaiswal, Archisman Ghosh, Behtash Behin-Aein, Joseph Makin, Shreyas Sen, Supriyo Datta
A p-circuit comprising a network of $ N$ p-bits can generate samples from a probability distribution with $ 2^N$ possibilities just like a network of q-bits, though there are interesting fundamental differences. A p-bit is essentially a binary stochastic neuron used in Boltzmann machines which involve the repeated application of a specific elementary operation, whereby each p-bit looks at the state of ‘n’ other p-bits, computes the probability for being $ 0$ or $ 1$ , and chooses its next state accordingly. We argue that the energy cost, $ \epsilon(n)$ , of this elementary operation is an important metric and we use our ASIC to extract it for our implementation, to serve as model and benchmark for other implementations. We further argue that the same elementary operation can be used in generative AI replacing the standard continuous or multi-bit digital neurons with p-bits. It might appear that this would introduce significant errors, but we show that by averaging a small number (say $ 1 \ to \ 100$ ) samples, the image quality can be restored.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
4 pages, 7 figures, letter
Temporal and spatial separations between spin glass and short-range order
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Margarita G. Dronova, Feng Ye, Zachary J. Morgan, Yishu Wang, Yejun Feng
Broken-symmetry-induced order parameters account for many phenomena in condensed matter physics. For spin glasses, such a framework dictates its theoretical construction, whereas experiments have only established dynamical behaviors such as frequency dependent magnetic susceptibility and aging but not the thermodynamic phase. Experimental techniques have limitations when the spin glass is probed as an isolated state. To resolve this conundrum, we create an evolution from long-range order using a well-controlled tuning of the disorder on a spinel’s sublattice. Cross-referencing a series of specimens at both long (milliseconds to seconds) and short (picosecond) time scales illustrates the relationship between spin glass and long- and short-range orders. The dynamics of short- and long-range order formations are not affected by disorder, as revealed by neutron magnetic diffuse scattering, however the ranges of these orderings are changed by the introduced disorder. Across all specimens, the inflection point of the correlation length’s temperature dependence fully matches with the peak in heat capacity, while spin glass can freeze either below or well above this characteristic temperature of spin order formation. Our results identify an uncorrelated coexistence of the two and attribute components of the spin glass to individual spins at domain walls between spin clusters.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Strongly Correlated Electrons (cond-mat.str-el)
Reversible local strain engineering of $\mathrm{WS}_2$ using a micro-mechanical spring
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Eric Herrmann, Zhixiang Huang, Sai Rahul Sitaram, Ke Ma, S M Jahadun Nobi, Xi Wang
Local strain engineering is a promising technique to tune the properties of two-dimensional materials at the nanoscale. However, many existing methods are static and limit the systematic exploration of strain-dependent material behavior. Here, we demonstrate dynamic and reversible control of local strain distributions in suspended trilayer tungsten disulfide ($ \mathrm{WS}_2$ ) via nanoindentation using a micro-mechanical spring patterned with nanoscale probes. Micro-photoluminescence measurements reveal that indentation using a ring-shaped probe induces a nearly uniform biaxial strain distribution accompanied by a reversible redshift of the neutral exciton peak, consistent with simulated strain magnitudes. We further show that the in-plane strain distribution is spatially programmable by engineering the probe geometry and present designs for inducing point-like, uniaxial, biaxial, and triaxial strain distributions. The presented platform enables substrate-free, repeatable local strain engineering in suspended 2D materials and provides a versatile tool for streamlining the investigation of strain-dependent phenomena.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Fundamental of CO2 Adsorption and Diffusion in Sub-nanoporous Materials: Application to CALF-20
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
André de Freitas Gonçalves, Emerson Parazzi Lyra, Sayali Ramdas Chavan, Philip Llewellyn, Luis Fernando Mercier Franco, Yann Magnin
We propose a theoretical approach for predicting thermodynamics and kinetics of guest molecules in nanoporous materials. This statistical mechanical-based method requires a minimal set of physical parameters that may originate from experiments or numerical simulations. We applied it to CO2 molecules in the recently highlighted CALF-20 metal-organic framework for adsorption and molecular self-diffusion at different temperatures. All the physical parameters of the model are extracted from one CO$ _2$ isotherm analyzed by the adsorption energy distribution method. The model is then used to approximate isotherms at different temperatures, Henry’s constant, saturation density, as well as enthalpies of adsorption at infinite dilution. We then express molecular kinetics through the transition state theory allowing to predict molecular diffusion in part from the prior knowledge of thermodynamics, and further compared self-diffusion coefficients to one from molecular dynamics used as a numerical experiment. The approach proposed allows to express molecular adsorption and diffusion based on a fitting procedure allowing to get physical parameters with a view on thermodynamics and kinetics mechanisms at play in the system.
Materials Science (cond-mat.mtrl-sci)
23 pages, 12 figures
Hyperuniformity at the Absorbing State Transition: Perturbative RG for Random Organization
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Xiao Ma, Johannes Pausch, Gunnar Pruessner, Michael E. Cates
Hyperuniformity, where the static structure factor obeys $ S(q)\sim q^{\varsigma}$ with $ \varsigma> 0$ , emerges at criticality in systems having multiple, symmetry-unrelated, absorbing states. Important examples arise in periodically sheared suspensions and amorphous solids; these lie in the random organisation (RO) universality class, for which analytic results for $ \varsigma$ are lacking. Here, using Doi-Peliti field theory and perturbative RG about a Gaussian model, we find $ \varsigma = 0^+$ and $ \varsigma= 2\epsilon/9 + O(\epsilon^2)$ in dimension $ d>d_c=4$ and $ d=4-\epsilon$ respectively. Our calculations assume that renormalizability is sustained via a certain pattern of cancellation of strongly divergent terms. These cancellations allow the upper critical dimension to remain $ d_c = 4$ , as is known for RO, while generic perturbations (e.g., those violating particle conservation) would typically flow to a fixed point with $ d_c=6$ . The assumed cancellation pattern is closely reminiscent of a long-established one near the tricritical Ising fixed point. (This has $ d_c=3$ , although generic perturbations flow towards the Wilson-Fisher fixed point with $ d_c = 4$ .) We show how hyperuniformity in RO emerges from anticorrelation of strongly fluctuating active and passive densities. Our calculations also yield the remaining exponents to order $ \epsilon$ , surprisingly without recourse to functional RG. These exponents coincide as expected with the Conserved Directed Percolation (C-DP) class which also contains the Manna Model and the quenched Edwards-Wilkinson (q-EW) model. Importantly however, our $ \varsigma$ differs from one found via a mapping to q-EW. That mapping neglects a conserved noise in the RO action, which we argue to be dangerously irrelevant. Thus, although other exponents are common to both, the RO and C-DP universality classes have different exponents for hyperuniformity.
Statistical Mechanics (cond-mat.stat-mech)
This is an expanded and clarified version of arXiv:2310.17391 , which it now supersedes without changing the main results
Growth of Structural Lengthscale in Kob Andersen Binary Mixtures: Role of medium range order
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Sanket Kumawat, Mohit Sharma, Ujjwal Kumar Nandi, Indrajit Tah, Sarika Maitra Bhattacharyya
A central and extensively debated question in glass physics concerns whether a single, growing lengthscale fundamentally controls glassy dynamics, particularly in systems lacking obvious structural motifs or medium range crystalline order (MRCO). In this work, we investigate structural and dynamical lengthscales in supercooled liquids using the Kob Andersen binary Lennard Jones (KALJ) model in two compositions: 80:20 and 60:40. We compute the dynamical lengthscale from displacement displacement correlation functions and observe a consistent growth as temperature decreases. To explore the static counterpart, we use a structural order parameter (SOP) based on the mean field caging potential. While this SOP is known to predict short time dynamics effectively, its bare correlation function reveals minimal spatial growth. Motivated by recent findings that long time dynamics reflect collective rearrangements, we perform spatial coarse-graining of the SOP and identify an optimal lengthscale $ L_{max}$ that maximises structure dynamics correlation. We show that the structural correlation length derived from SOP coarse-grained over $ L_{max}$ exhibits clear growth with cooling and closely tracks the dynamical lengthscale, especially for A particles in the 80:20 mixture and for both A and B particles in the 60:40 system. Our results reconcile the previously observed absence of static length growth in MRCO-free models like KALJ by highlighting the necessity of intermediate range structural descriptors. Furthermore, we find that the particles with larger structural length growth also correspond to species with latent crystallisation tendencies, suggesting a possible link between structural order, dynamics, and incipient crystallisation.
Soft Condensed Matter (cond-mat.soft), Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph)
14 pages, 41 figures
The effect of fiber plasticity on domain formation in soft biological composites – Part I: a bifurcation analysis
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Michalis Agoras, Fernanda F. Fontenele, Nikolaos Bouklas
The main objective of this work is to shed light on the effect of fiber plasticity on the macroscopic response and domain formation in soft biological composites. This goal is pursued by analyzing the plane-strain response of two-phase laminates. In the context of this problem, the effect of fiber plasticity is accounted for by allowing the elastically stiffer layers (fiber'' phase) to also yield plastically and by taking the soft layers (matrix’’ phase) to be purely elastic solids. The analysis is carried out at finite elastic and plastic strains, but it is restricted to unidirectional, non-monotonic loading paths, applied by initially increasing the macroscopic stretch along the direction of the layers up to a prescribed maximum value and then decreasing the same stretch down to a minimum value. A simple expression is derived for the critical conditions at which the homogenized behavior of the laminate loses strong ellipticity for the first time along the loading path. The relevance of this result stems from the fact that the loss of macroscopic ellipticity of these composites is known to coincide with the onset of bifurcations of the long-wavelength type. It follows from this result that, just like hyperelastic laminates, elastoplastic laminates may lose macroscopic ellipticity whenever their incremental strength in shear perpendicular to the layers vanishes for the first time. For situations in which loss of macroscopic ellipticity does take place, a corresponding post-bifurcation solution for the homogenized behavior of the laminate is computed. The deformed state of the material described by this solution is characterized by twin lamellar domains that are formed at a length scale much larger than the width of the original, microscopic layers, but still much smaller than the overall dimensions of the macroscopic specimen under consideration.
Soft Condensed Matter (cond-mat.soft)
29 pages, 9 figures
Modulation of PEDOT properties via cobalt ferrite nanoparticles: morphology, conjugation length, doping level, structure, and electrical conductivity
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Gabriel Paciaroni, María Ana Castro, Carlos Acha, Paula Soledad Antonel
Composite materials based on Poly(3,4-ethylenedioxythiophene) (PEDOT) and CoFe$ _2$ O$ _4$ magnetic nanoparticles (NP) were synthesized by chemical oxidative polymerization with varying monomer and surfactant (DBSA) concentrations, and were compared to PEDOT samples synthesized without NP. Electrical conductivity measurements were performed, which revealed that the composites are more conductive than the pure PEDOT samples, with this effect depending on EDOT and DBSA contents. Characterizations by SEM and TEM microscopies, UV-Vis, FTIR and Raman spectroscopies, X-ray diffraction and dynamic light scattering were carried out in order to associate the morphology and structure of these materials to their electrical conductivity, and to explain how EDOT and DBSA concentrations, and also the presence of NP, affects those properties. It was found that the NP play a significant role in the polymerization of EDOT, influencing the formation and arrangement of polymer chains, as well as their conjugation length, oxidation state, and resonant structures. These effects are also dependent on the DBSA content. To describe the conductivity of the composites, a two-phase model based on general effective media theory was introduced. The analysis revealed that, at low reactant concentrations, the NP increase the conductivity of the adjacent PEDOT by over two orders of magnitude.
Materials Science (cond-mat.mtrl-sci)
42 pages, 7 figures
Polymer 334 (2025) 128652
Instability in Ostwald ripening processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
There is a dimensionless parameter which enters into the equation for the evolution of supersaturation in Ostwald ripening processes. This parameter is typically a large number. Here it is argued that the consequent stiffness of the equation results in the evolution of the supersaturation being unstable. The instability is evident in numerical simulations of Ostwald ripening.
Statistical Mechanics (cond-mat.stat-mech), Chaotic Dynamics (nlin.CD)
16 pages, 8 figures
Temperature Dependent Optical Response Of High- Tc Yba2cu3o7-δ (Ybco) Thin Films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-11 20:00 EDT
Vivek Khichar, V. A. Chirayath, Jonathan Asaadi, Nader Hozhabri, Benjamin J. P. Jones, Ali R. Koymen, Iakovos Tzoka, Pratyanik Sau
We report on the temperature-dependent optical response of thin films of YBa2Cu3O7-{\delta} (YBCO) in the visible spectral range under cryogenic conditions. Specifically, we observe an increase in transmittance near the superconducting transition temperature (Tc), which saturates within a few kelvins below Tc. The increase in transmittance is accompanied by a corresponding decrease in reflectance as the temperature drops below Tc, and both quantities track the superconducting phase transition. Changes in transmittance are found to be wavelength dependent, with the maximum variation occurring at 633 nm and minimal at 450 nm. These observations establish a correlation between the variation in optical response and the superconducting phase transition, even in the visible regime. The results of our experiment highlight the potential for using non-contact optical measurements to determine Tc. The effect can be explained using the two-fluid model, which can account for the observed temperature and wavelength dependence of the transmittance of the superconducting thin films.
Superconductivity (cond-mat.supr-con)
Excess Observables Reveal Nonreciprocity in Integrated Covariance
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Timur Aslyamov, Massimiliano Esposito
Near equilibrium, the symmetric part of the time-integrated steady-state covariance, i.e., the time integral of correlation functions, is governed by the fluctuation-dissipation theorem, while the antisymmetric part vanishes due to Onsager reciprocity. Far from equilibrium, where these principles no longer apply, we develop a unified formalism for both symmetric and antisymmetric components of integrated covariances. We derive exact, computationally tractable expressions for these quantities, valid in arbitrary nonequilibrium steady states of Markov jump processes. Both components are expressed in terms of excess observables, a notion central to both statistical physics and reinforcement learning. Furthermore, we establish thermodynamic upper bounds for these covariances in terms of entropy production, dynamical activity, and cycle affinities.
Statistical Mechanics (cond-mat.stat-mech)
Membrane-mediated force transduction: Stick-slip motion of vesicles with fluid membranes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Paula Magrinya, Arin Escobar Ortiz, Juan L. Aragones, Laura R. Arriaga
How internal forces are transduced into motion through soft, fluid membranes remains a fundamental question in the study of active systems. To investigate this coupling, we develop a minimal system consisting of a single ferromagnetic particle encapsulated within a lipid vesicle with controlled membrane composition and phase behavior. An external rotating magnetic field actuates the particle, which rotates and translates along the inner membrane leaflet. This motion generates local slip in the membrane; near a substrate, the slip creates a shear gradient across the lubrication gap that propels the vesicle forward. Propulsion is intermittent and strongest when the particle moves near the vesicle bottom, where stress transmission is most effective. We find that the coupling between internal flows and vesicle motion is highly sensitive to membrane elasticity, excess area, and phase coexistence. Local membrane deformation and flow dissipate part of the stress, limiting the efficiency of force transduction. Additionally, membrane fluctuations and external boundaries reduce particle mobility, and in phase-separated membranes, line tension at domain boundaries deflects the particle and gradually reorients membrane structure. These results demonstrate that lipid membranes not only transmit internal stresses but also remodel themselves in response, actively shaping the dynamics of force transduction and motion in active systems.
Soft Condensed Matter (cond-mat.soft)
9 pages, 5 figures
Shaping Magnetic Order by Local Frustration for Itinerant Fermions on a Graph
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Kinetic magnetism is an iconic and rare example of collective quantum order that emerges from the interference of paths taken by a hole in a sea of strongly interacting fermions. Here the lattice topology plays a fundamental role, with odd loops frustrating ferromagnetism, as seen in recent experiments. However, the resulting magnetic order on a general graph has remained elusive. Here we systematically establish, using exact diagonalization, that local frustration centers on a grid strongly bind singlets while sharing a delocalized hole. This collective effect generalizes to random graphs, producing sharp and predictable variation with tunable frustration measures. Our findings demonstrate that one can shape the spin order as well as tune the net magnetization by embedding geometric frustration, opening up new avenues for spatially resolved quantum control of many-body systems. We outline a protocol to realize some of the key findings in existing cold-atom setups.
Strongly Correlated Electrons (cond-mat.str-el), Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech)
4 pages, 5 figures + appendix
Pseudoperiodic Spherical Boundary Conditions: Efficient And Isotropic 3D Particle Simulations Without Lattice Artifacts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-11 20:00 EDT
Manuel Dedola, Ludovico Cademartiri
Periodic Boundary Conditions (PBC) introduce well-known lattice artifacts. We present a novel Pseudoperiodic Spherical Boundary Condition (SBC) that is perfectly isotropic. Through detailed comparative simulations, we demonstrate that SBC eliminates the structural and dynamic anisotropy inherent to PBC. For the crowded systems where these artifacts are most prominent, our method is also computationally more efficient than standard Minimum Image Convention implementations. This establishes SBC as a powerful, high-fidelity alternative for simulating isotropic matter.
Soft Condensed Matter (cond-mat.soft), Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Statistical Mechanics (cond-mat.stat-mech)
Graphene Heterostructure-Based Non-Volatile Memory Devices with Top Floating Gate Programming
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Gabriel L. Rodrigues, Ana B. Yoshida, Guilherme S. Selmi, Nickolas T.K.B de Jesus, Igor Ricardo, Kenji Watanabe, Takashi Taniguchi, Rafael F. de Oliveira, Victor Lopez-Richard, Alisson R. Cadore
We present a graphene-based memory platform built on dual-gated field-effect transistors (GFETs). By integrating a lithographically defined metal patch directly atop the hexagonal boron nitride (hBN)-graphene channel, the device functions simultaneously as a top gate, floating gate (FG) reservoir, and active reset contact. This architecture forms an ultrathin van der Waals heterostructure with strong capacitive coupling to the back-gate, confirmed by a dynamic model, enabling a tunable and wide memory window that scales with back-gate voltage and is further enhanced by reducing hBN thickness or increasing FG area. Our devices demonstrate reversible, high-efficiency charge programming, robust non-volatile behavior across 10 to 300 K and a wide range of operation speeds, and endurance beyond 9800 cycles. Importantly, a grounded top electrode provides on-demand charge erasure, offering functionality that is absent in standard FG designs. These results position hBN/graphene-based GFETs as a compact, energy-efficient platform for next-generation 2D flash memory, with implications for multilevel memory schemes and cryogenic electronics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
2025
Edge State Selective Measurement of Quantum Hall Dispersions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Henok Weldeyesus, Taras Patlatiuk, Qianqian Chen, Christian P. Scheller, Amir Yacoby, Loren N. Pfeiffer, Ken W. West, Dominik M. Zumbühl
Edge states reflect the key physical properties yet are difficult to probe individually, particularly when several states are present at an edge. We present momentum resolved tunneling spectroscopy between a quantum well and a quantum wire to extract the dispersions of the quantum Hall edge states. Momentum and energy selective tunneling allows to separately address the different states even if they are spatially overlapping. This delivers the edge state velocities over broad ranges of magnetic field and density, in excellent agreement with a hard-wall model. This technique provides a basis for future edge state selective spectroscopy on quantum materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
A statistical physics framework for optimal learning
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-11 20:00 EDT
Francesca Mignacco, Francesco Mori
Learning is a complex dynamical process shaped by a range of interconnected decisions. Careful design of hyperparameter schedules for artificial neural networks or efficient allocation of cognitive resources by biological learners can dramatically affect performance. Yet, theoretical understanding of optimal learning strategies remains sparse, especially due to the intricate interplay between evolving meta-parameters and nonlinear learning dynamics. The search for optimal protocols is further hindered by the high dimensionality of the learning space, often resulting in predominantly heuristic, difficult to interpret, and computationally demanding solutions. Here, we combine statistical physics with control theory in a unified theoretical framework to identify optimal protocols in prototypical neural network models. In the high-dimensional limit, we derive closed-form ordinary differential equations that track online stochastic gradient descent through low-dimensional order parameters. We formulate the design of learning protocols as an optimal control problem directly on the dynamics of the order parameters with the goal of minimizing the generalization error at the end of training. This framework encompasses a variety of learning scenarios, optimization constraints, and control budgets. We apply it to representative cases, including optimal curricula, adaptive dropout regularization and noise schedules in denoising autoencoders. We find nontrivial yet interpretable strategies highlighting how optimal protocols mediate crucial learning tradeoffs, such as maximizing alignment with informative input directions while minimizing noise fitting. Finally, we show how to apply our framework to real datasets. Our results establish a principled foundation for understanding and designing optimal learning protocols and suggest a path toward a theory of meta-learning grounded in statistical physics.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG), Neurons and Cognition (q-bio.NC)
35 pages, 13 figures
Chiral superconductivity near a fractional Chern insulator
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-11 20:00 EDT
Taige Wang, Michael P. Zaletel
Superconductivity arising from fully spin-polarized, repulsively interacting electrons can host intrinsically chiral Cooper pairs and Majorana zero modes, yet no concrete microscopic route to such a state has been established. Motivated by recent observations in twisted MoTe$ _2$ and rhombohedral pentalayer graphene, where fractional Chern insulators (FCIs) appear adjacent to spin-valley-polarized superconductors, we investigate a minimal model: spinless electrons in the lowest Landau level subject to a tunable moire potential. Large-scale density-matrix renormalization group (DMRG) calculations show that, as the FCI gap closes, two nearly degenerate phases emerge before a metallic state forms. A chiral $ f+if$ superconductor and a commensurate $ \sqrt{3} \times \sqrt{3}$ charge-density wave (CDW) differ in energy by less than $ 1%$ , reproducing the distinct superconducting and re-entrant integer quantum Hall (RIQH) phases experimentally observed near the FCI regime. The superconducting dome remains robust against realistic Coulomb screening, light doping, and variations in lattice geometry. Melting the FCI therefore provides a new mechanism for realizing spin-polarized chiral superconductivity and RIQH order. We predict that twisted MoTe$ _2$ at larger twist angles will develop a superconducting dome even at filling $ \nu = 2/3$ , and suppressing this superconductivity with a magnetic field should drive the system into an RIQH state.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
9 pages, 5 figures
Phase Stability and Transformations in Lead Mixed Halide Perovskites from Machine Learning Force Fields
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-11 20:00 EDT
Xia Liang, Johan Klarbring, Aron Walsh
Lead halide perovskites (APbX$ _3$ ) offer tunable optoelectronic properties but feature an intricate phase-stability landscape. Here we employ on-the-fly data collection and an equivariant message-passing neural-network potential to perform large-scale molecular dynamics of three prototypical perovskite systems: CsPbX$ _3$ , MAPbX$ _3$ , and FAPbX$ _3$ . Integrating these simulations with the PDynA analysis toolkit, we resolve both equilibrium phase diagrams and dynamic structural evolution under varying temperature and halide-mixing conditions. Our findings reveal that the A-site cation strongly modulates octahedral tilt modes and phase pathways: MA$ ^+$ effectively “forbids” the beta-to-gamma transition in MAPbX$ _3$ by requiring extensive molecular rearrangements and crystal rotation, whereas the debated low-temperature phase in FAPbX$ _3$ is best represented as an Im$ \bar{3}$ cubic phase with $ a^+a^+a^+$ tilts. Additionally, small changes in halide composition and arrangement $ \unicode{x2013}$ from uniform mixing to partial segregation $ \unicode{x2013}$ alter tilt correlations. Segregated domains can even foster anomalous tilting modes that impede uniform phase transformations. These results highlight the multi-scale interplay between cation environment and halide distribution, offering a rational basis for tuning perovskite architectures toward improved phase stability.
Materials Science (cond-mat.mtrl-sci)
Finite-time and Finite-size scalings of coercivity in dynamic hysteresis
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Miao Chen, Xiu-Hua Zhao, Yu-Han Ma
The coercivity panorama for characterizing the dynamic hysteresis in interacting systems across multiple timescales is proposed by Chen et al. in a companion paper. For the stochastic $ \phi^4$ model under periodic driving of rate $ v_H$ , the coercivity landscape $ H_c(v_H)$ exhibits plateau features at a characteristic rate $ v_P$ with the corresponding coercivity $ H_P$ . Below this plateau ($ v_H<v_P$ ), the $ H_c\sim v_H$ scaling obtained in the near-equilibrium regime becomes inaccessible in the thermodynamic limit. Above the plateau ($ v_H>v_P$ ), scaling in the fast-driving regime, $ H_c\sim v_H^{1/2}$ , is completely different from that, $ H_c-H_P\sim (v_H-v_P)^{2/3}$ , in the post-plateau slow-driving regime. The emergence of the plateau with a finite-size scaling reflects the competition between the thermodynamic limit and the quasi-static limit. In this paper, we provide detailed analytical proofs and numerical evidence supporting these results. Moreover, to demonstrate the coercivity panorama in concrete physical systems, we study the magnetic hysteresis in the Curie-Weiss model and analyze its finite-size effects. We reveal that finite-time coercivity scaling shows model-specific behavior only in the fast-driving regime, while exhibiting universal characteristics elsewhere.
Statistical Mechanics (cond-mat.stat-mech)
Comments are welcome! arXiv admin note: substantial text overlap with arXiv:2506.24035
A c-theorem for the effective central charge in the R=1 replica limit, and applications to systems with measurement-induced randomness
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-11 20:00 EDT
Rushikesh A. Patil, Andreas W. W. Ludwig
We present a general theorem demonstrating non-perturbatively the decrease of the “effective central charge” $ c_{\text{eff}}=(d c/dR)|{R=1}$ under renormalization group (RG) flow in the $ R\rightarrow1$ replica limit of a $ R$ -copy $ 2D$ conformal field theory (CFT) action $ S{\ast}$ perturbed by a replica interaction of the form $ -\mathbb{S}=-\sum_{a=1}^{R}S_{\ast}^{(a)}+\Delta\int d^2 x \sum_{\substack{a,b=1\ a\neq b}}^{R}\varphi^{(a)}(x)\varphi^{(b)}(x).$ Here $ \varphi$ is a scaling field belonging to the CFT with action $ S_\ast$ and the coupling $ \Delta$ is relevant in the RG sense. We show that the infrared value of $ c_{\text{eff}}$ is always $ \textit{less}$ than the central charge $ c$ of the unperturbed CFT $ S_{\ast}$ . We refer to this result as the “$ c$ -effective theorem”. As an application of this theorem, we consider replica field theories in the limit of $ R \to 1$ replicas of the form above, shown by Nahum and Jacobsen [arXiv:2504.01264] to describe $ 2D$ classical monitored systems, where measurements introduce a form of quenched randomness via Bayes’ theorem. Lastly, we discuss a possible relationship of our theorem with the effective central charge $ c_{\text{eff}}^{(R\rightarrow0)}=(dc/dR)|_{R=0}$ for the above replica action in the different $ R\rightarrow0$ replica limit, which is of relevance to systems with generic uncorrelated impurity-type quenched disorder, as opposed to measurements.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Physics (quant-ph)
15 pages
Spin-only dynamics of the multi-species nonreciprocal Dicke model
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-11 20:00 EDT
Joseph Jachinowski, Peter B. Littlewood
The Hepp-Lieb-Dicke model is ubiquitous in cavity quantum electrodynamics, describing spin-cavity coupling which does not conserve excitation number. Coupling the closed spin-cavity system to an environment realizes the open Dicke model, and by tuning the structure of the environment or the system-environment coupling, interesting spin-only models can be engineered. In this work, we focus on a variation of the multi-species open Dicke model which realizes mediated nonreciprocal interactions between the spin species and, consequently, an interesting dynamical limit-cycle phase. In particular, we improve upon adiabatic elimination and, instead, employ a Redfield master equation in order to describe the effective dynamics of the spin-only system. We assess this approach at the mean-field level, comparing it both to adiabatic elimination and the full spin-cavity model, and find that the predictions are sensitive to the presence of single-particle incoherent decay. Additionally, we clarify the symmetries of the model and explore the dynamical limit-cycle phase in the case of explicit parity-time-symmetry breaking, finding a region of phase coexistence terminating at an codimension-two exceptional point. Lastly, we go beyond mean-field theory by exact numerical diagonalization of the master equation, appealing to permutation symmetry in order to increase the size of accessible systems. We find signatures of phase transitions even for small system sizes.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
18 pages, 6 figures
Purcell enhancement of photogalvanic currents in a van der Waals plasmonic self-cavity
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-11 20:00 EDT
Xinyu Li, Jesse Hagelstein, Gunda Kipp, Felix Sturm, Kateryna Kusyak, Yunfei Huang, Benedikt F. Schulte, Alexander M. Potts, Jonathan Stensberg, Victoria Quirós-Cordero, Chiara Trovatello, Zhi Hao Peng, Chaowei Hu, Jonathan M. DeStefano, Michael Fechner, Takashi Taniguchi, Kenji Watanabe, P. James Schuck, Xiaodong Xu, Jiun-Haw Chu, Xiaoyang Zhu, Angel Rubio, Marios H. Michael, Matthew W. Day, Hope M. Bretscher, James W. McIver
Cavities provide a means to manipulate the optical and electronic responses of quantum materials by selectively enhancing light-matter interaction at specific frequencies and momenta. While cavities typically involve external structures, exfoliated flakes of van der Waals (vdW) materials can form intrinsic self-cavities due to their small finite dimensions, confining electromagnetic fields into plasmonic cavity modes, characterized by standing-wave current distributions. While cavity-enhanced phenomena are well-studied at optical frequencies, the impact of self-cavities on nonlinear electronic responses–such as photogalvanic currents–remains largely unexplored, particularly in the terahertz regime, critical for emerging ultrafast optoelectronic technologies. Here, we report a self-cavity-induced Purcell enhancement of photogalvanic currents in the vdW semimetal WTe$ _2$ . Using ultrafast optoelectronic circuitry, we measured coherent near-field THz emission resulting from nonlinear photocurrents excited at the sample edges. We observed enhanced emission at finite frequencies, tunable via excitation fluence and sample geometry, which we attribute to plasmonic interference effects controlled by the cavity boundaries. We developed an analytical theory that captures the cavity resonance conditions and spectral response across multiple devices. Our findings establish WTe$ _2$ as a bias-free, geometry-tunable THz emitter and demonstrate the potential of self-cavity engineering for controlling nonlinear, nonequilibrium dynamics in quantum materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)