CMP Journal 2025-07-24
Statistics
Nature Reviews Materials: 1
Physical Review Letters: 24
Physical Review X: 1
arXiv: 66
Nature Reviews Materials
Hidden orders in spin-orbit-entangled correlated insulators
Review Paper | Electronic properties and materials | 2025-07-23 20:00 EDT
Leonid V. Pourovskii, Dario Fiore Mosca, Lorenzo Celiberti, Sergii Khmelevskyi, Arun Paramekanti, Cesare Franchini
In many materials, ordered phases and their order parameters are easily characterized by standard experimental methods. ‘Hidden order’ refers to a phase transition in which an ordered state emerges without such an easily detectable order parameter, despite clear thermodynamic evidence of the transition. The underlying mechanisms for these unconventional states of matter stem from spin-orbit coupling, which intertwines intersite exchange, classical electron-magnetic interactions and electron-lattice effects. This physics is elusive to experimental probes and beyond traditional theories of insulating magnetism, requiring sophisticated methodologies for its exploration. In this Review, we survey exotic hidden-order phases in correlated insulators, particularly focusing on the latest progress in material-specific theories and numerical approaches. The relevant degrees of freedom in these phases are local high-rank multipole moments of magnetic and charge density that emerge from spin-orbit-entangled correlated shells of heavy d and f electron ions and interact on the lattice via various mechanisms. We discuss approaches to modelling hidden orders in realistic systems via direct ab initio calculations or by constructing low-energy many-body effective Hamiltonian. We also describe how these new theoretical tools have helped to uncover driving mechanisms for recently discovered multipolar phases in double perovskites of heavy transition metals and how they have proved instrumental in disentangling the role of various interactions in ‘traditional’ f-electron multipolar materials such as actinide dioxides. In both cases, material-specific theories have played a key part in interpreting and predicting experimental signatures of hidden orders.
Electronic properties and materials, Magnetic properties and materials
Physical Review Letters
Entanglement Structure of Non-Gaussian States and How to Measure It
Research article | Fermi gases | 2025-07-23 06:00 EDT
Henry Froland, Torsten V. Zache, Robert Ott, and Niklas Mueller
Rapidly growing capabilities of quantum simulators to probe quantum many-body phenomena require new methods to characterize increasingly complex states. We present a protocol that constrains quantum states using experimentally measured correlation functions. This method enables measurement of a quantum state’s entanglement structure, opening a new route to study entanglement-related phenomena. Our approach extends Gaussian state parameterizations by systematically incorporating higher-order correlations. We show the protocol’s usefulness in conjunction with current and forthcoming experimental capabilities, focusing on weakly interacting fermions as a proof of concept. Here, the lowest nontrivial expansion quantitatively predicts early time thermalization dynamics, including signaling the onset of quantum chaos indicated by the entanglement Hamiltonian.
Phys. Rev. Lett. 135, 040201 (2025)
Fermi gases, Quantum chaos, Quantum entanglement, Correlation function measurements, Exact diagonalization, Hubbard model, Lattice field theory
Simulating Quantum Instruments with Projective Measurements and Quantum Postprocessing
Research article | Quantum entanglement | 2025-07-23 06:00 EDT
Shishir Khandelwal and Armin Tavakoli
Quantum instruments describe both the classical outcome and the updated state associated with a quantum measurement. We ask whether these processes can be simulated using only a natural subset of resources, namely projective measurements on the system and quantum processing of the postmeasurement states. We show that the simulability of instruments can be connected to an entanglement classification problem. This leads to a computationally efficient necessary condition for simulation of generic instruments and to a complete characterisation for qubits. We use this to address relevant quantum information tasks, namely (i) the noise tolerance of standard qubit unsharp measurements, (ii) nonprojective advantages in information-disturbance trade-offs, and (iii) increased sequential Bell inequality violations under projective measurements. Moreover, we consider also $d$-dimensional L"uders instruments that correspond to weak versions of standard basis measurements and show that for large $d$ these can permit scalable noise advantages over projective implementations.
Phys. Rev. Lett. 135, 040202 (2025)
Quantum entanglement, Quantum foundations, Quantum measurements, Unsharp measurements
Effective Theory for Strongly Attractive One-Dimensional Fermions
Research article | Scattering of atoms, molecules, clusters & ions | 2025-07-23 06:00 EDT
Timothy G. Backert, Fabian Brauneis, Matija Čufar, Joachim Brand, Hans-Werner Hammer, and Artem G. Volosniev
The problem of strongly attractive fermionic systems in one dimension can be tackled by semianalytical methods.
Phys. Rev. Lett. 135, 040401 (2025)
Scattering of atoms, molecules, clusters & ions, 1-dimensional systems, Strongly correlated systems, Bethe ansatz
Finite-Temperature Quantum Topological Order in Three Dimensions
Research article | Open quantum systems & decoherence | 2025-07-23 06:00 EDT
Shu-Tong Zhou, Meng Cheng, Tibor Rakovszky, Curt von Keyserlingk, and Tyler D. Ellison
The three-dimensional fermionic toric code shows topological order and long-range entanglement at low but nonzero temperatures due to the anomalous 2-form symmetry of the system.
Phys. Rev. Lett. 135, 040402 (2025)
Open quantum systems & decoherence, Topological order, Quantum many-body systems, Symmetries in condensed matter
Enhancing Dynamic Range of Sub-Standard-Quantum-Limit Measurements via Quantum Deamplification
Research article | Quantum control | 2025-07-23 06:00 EDT
Qi Liu, Ming Xue, Matthew Radzihovsky, Xinwei Li, Denis V. Vasilyev, Ling-Na Wu, and Vladan Vuletić
Balancing high sensitivity with a broad dynamic range is a fundamental challenge in measurement science, as improving one often compromises the other. While traditional quantum metrology has prioritized enhancing local sensitivity, a large dynamic range is crucial for applications such as atomic clocks, where extended phase interrogation times contribute to wider phase range. In this Letter, we introduce a novel quantum deamplification mechanism that extends dynamic range at a minimal cost of sensitivity. Our approach uses two sequential spin-squeezing operations to generate and detect an entangled probe state, respectively. We demonstrate that the optimal quantum interferometer limit can be approached through two-axis countertwisting dynamics. Further expansion of dynamic range is possible by using sequential quantum deamplification interspersed with phase encoding processes. Additionally, we show that robustness against detection noise can be enhanced by a hybrid sensing scheme that combines quantum deamplification with quantum amplification. Our protocol is within the reach of state-of-the-art atomic-molecular-optical platforms, offering a scalable, noise-resilient pathway for entanglement-enhanced metrology.
Phys. Rev. Lett. 135, 040801 (2025)
Quantum control, Quantum feedback, Quantum metrology, Quantum parameter estimation, Quantum protocols
First Search for Axion Dark Matter with a MADMAX Prototype
Research article | Dark matter | 2025-07-23 06:00 EDT
B. Ary dos Santos Garcia et al. (MADMAX Collaboration)
This Letter presents the first search for dark matter axions with mass in the ranges $76.56$ to $76.82\text{ }\text{ }\mathrm{\mu }\mathrm{eV}$ and $79.31$ to $79.53\text{ }\text{ }\mathrm{\mu }\mathrm{eV}$ using a prototype setup for the MAgnetized Disk and Mirror Axion eXperiment (MADMAX). The experimental setup employs a dielectric haloscope consisting of three sapphire disks and a mirror to resonantly enhance the axion-induced microwave signal within the magnetic dipole field provided by the 1.6 T Morpurgo magnet at CERN. Over 14.5 days of data collection, no axion signal was detected. A 95% CL upper limit on the axion-photon coupling strength down to $|{g}{a\gamma }|\sim 2\times{}{10}^{- 11}\text{ }\text{ }{\mathrm{GeV}}^{- 1}$ is set in the targeted mass ranges, surpassing previous constraints, assuming a local axion dark matter density ${\rho }{a}$ of $0.3\text{ }\text{ }\mathrm{GeV}/{\mathrm{cm}}^{3}$. This study marks the first axion dark matter search using a dielectric haloscope.
Phys. Rev. Lett. 135, 041001 (2025)
Dark matter, Dark matter direct detection, Axion-like particles, Axions, Dark matter detectors
First Look at Quartic-in-Spin Binary Dynamics at Third Post-Minkowskian Order
General relativity | 2025-07-23 06:00 EDT
Dogan Akpinar, Fernando Febres Cordero, Manfred Kraus, Alexander Smirnov, and Mao Zeng
We compute the conservative and radiation-reaction contributions to classical observables in the gravitational scattering between a spinning and a spinless black hole to the fourth order in spin and third order in the gravitational constant. The conservative results are obtained from two-loop amplitudes for the scattering process of a massive scalar with a massive spin-$s$ field ($s=0$, 1, 2) minimally coupled to gravity, employing the recently introduced spin interpolation method to resolve all spin-Casimir terms. The two-loop amplitude exhibits a spin-shift symmetry in both probe limits, which we conjecture to be a sign of yet unknown integrability of Kerr orbits through the quartic order in spin and to all orders in the gravitational constant. We obtain the radial action from the finite part of the amplitude and use it to compute classical observables, including the impulse and spin kick. This is done using the recently introduced covariant Dirac brackets, which allow for the computation of classical scattering observables for general (nonaligned) spin configurations. Finally, employing the radiation-reaction amplitude proposed by Alessio and Di Vecchia, together with the Dirac brackets, we obtain radiation-reaction contributions to observables at all orders in spin and beyond the aligned-spin limit. We find agreement with known results up to the quadratic order in spin for both conservative and radiation-reaction contributions. Our results advance the state of the art in the understanding of spinning binary dynamics in general relativity and demonstrate the power and simplicity of the Dirac bracket formalism for relating scattering amplitudes to classical observables.
Phys. Rev. Lett. 135, 041602 (2025)
General relativity, Perturbation theory, Quantum field theory, Scattering amplitudes
Tripling Fluctuations and Peaked Sound Speed in Fermionic Matter
Research article | Color deconfinement | 2025-07-23 06:00 EDT
Hiroyuki Tajima, Kei Iida, Toru Kojo, and Haozhao Liang
A crossover involving three-fermion clusters is relevant to the hadron-quark crossover, which, if occurring in a neutron star, could naturally reproduce the dense-matter equation of state recently deduced from simultaneous observations of neutron-star masses and radii. To understand the crossover mechanism, we examine the role of tripling fluctuations induced by the formation of three-fermion clusters. The phase-shift representation of fluctuations manifests an interplay of bound and scattering states, leading to nonmonotonic momentum distributions of baryonlike clusters and peaked sound speed at finite densities. We demonstrate them by applying our approach to a nonrelativistic system of one-dimensional three-color fermions analogous to the hadron-quark matter.
Phys. Rev. Lett. 135, 042701 (2025)
Color deconfinement, Equations of state of nuclear matter, Nuclear matter in neutron stars, Quantum chromodynamics, Quark matter, Quantum many-body systems
Dual Spectroscopy of Quantum Simulated Fermi-Hubbard Systems
Research article | Cold atoms & matter waves | 2025-07-23 06:00 EDT
K. Knakkergaard Nielsen, M. Zwierlein, and G. M. Bruun
Quantum gas microscopy with atoms in optical lattices provides remarkable insights into the real space properties of many-body systems, but does not directly reveal the nature of their fundamental excitation spectrum. Here, we demonstrate that radio-frequency spectroscopy can reveal the quasiparticle nature of doped quantum many-body systems, crucial for our understanding of, e.g., high-temperature superconductors. In particular, we showcase how the existence and energy of magnetic polaron quasiparticles in doped Fermi-Hubbard systems may be probed, revealed by hallmark peaks in the spectroscopic spectrum. In combination with fundamental dualities of the Fermi-Hubbard model, we describe how these findings may be tested using several experimental platforms.
Phys. Rev. Lett. 135, 043401 (2025)
Cold atoms & matter waves, Fermi gases, Polarons, Quantum simulation, Quasiparticles & collective excitations, Radio frequency techniques, High-temperature superconductors, Duality, Hubbard model, Self-consistent field theory, t-J model
Lifetime-Limited and Tunable Emission from Single Charge-Stabilized Nickel Vacancy Centers in Diamond
Research article | Color centers | 2025-07-23 06:00 EDT
I. M. Morris, T. Lühmann, K. Klink, L. Crooks, D. Hardeman, D. J. Twitchen, S. Pezzagna, J. Meijer, S. S. Nicley, and J. N. Becker
The negatively charged nickel vacancy center (${\mathrm{NiV}}^{- }$) in diamond is a promising spin qubit candidate with predicted inversion symmetry, large ground state spin-orbit splitting to limit phonon-induced decoherence, and emission in the near infrared. Here, we experimentally confirm the proposed geometric and electronic structure of the NiV defect via magneto-optical spectroscopy. We characterize the optical properties and find a Debye-Waller factor of 0.62. Additionally, we engineer charge state stabilized defects using electrical bias in planar all-diamond p-i-p junctions. We measure a vanishing static dipole moment and no spectral diffusion, characteristic of inversion symmetry. Under bias, we observe stable transitions with lifetime-limited linewidths as narrow as 16 MHz and convenient frequency tuning of the emission via a second-order Stark shift. Overall, this Letter provides a pathway toward coherent control of the ${\mathrm{NiV}}^{- }$ and its use as a spin qubit and contributes to a more general understanding of charge dynamics experienced by defects in diamond.
Phys. Rev. Lett. 135, 043602 (2025)
Color centers, Crystal defects, Magneto-optical spectra, Stark effect
Three-Dimensional Helical-Rotating Plasma Structures in Beam-Generated Partially Magnetized Plasmas
Research article | Penning discharges | 2025-07-23 06:00 EDT
Jian Chen, Andrew T. Powis, Igor D. Kaganovich, Zhibin Wang, and Yi Yu
Azimuthal structures emerging in beam-generated partially magnetized plasmas are investigated using three-dimensional particle in cell-Monte Carlo collision simulations. Two distinct instability regimes are identified at low pressures. When the gas pressure is sufficiently high, quasineutrality is attained and 2D spiral-arm structures form as a result of the development of a lower-hybrid instability, resulting in enhanced cross-field transport. At lower pressures, quasineutrality is not achieved and a 3D helical-rotating plasma structure forms due to development of the diocotron instability. Analytical formulas are proposed for the critical threshold pressure between these regimes and for the rotation frequency of the helical structures. Preliminary experimental verification is provided.
Phys. Rev. Lett. 135, 045301 (2025)
Penning discharges, Plasma instabilities, Plasma production & heating by particle beams
Circular-Motion Fulling-Davies-Unruh Effect in Coupled Annular Josephson Junctions
Research article | Quantum fields in curved spacetime | 2025-07-23 06:00 EDT
Haruna Katayama and Noriyuki Hatakenaka
We propose an experimentally feasible approach for observing the Fulling-Davies-Unruh effect in circular motions using a novel detector based on the thermally activated decay of metastable bunched fluxon-antifluxon pairs in coupled annular Josephson junctions. The uniform circular motion of fluxon pairs acting as detectors under relativistic velocities and small radii produces high acceleration, making an effective Unruh temperature on the order of 1 K observable with existing technologies. In addition, the newly designed detector delivers highly sensitive temperature measurements, offering a promising avenue for experimentally probing the nontrivial properties of the quantum vacuum. Numerical simulations confirm a clear acceleration-dependent temperature providing compelling evidence for the Fulling-Davies-Unruh effect.
Phys. Rev. Lett. 135, 046001 (2025)
Quantum fields in curved spacetime, Unruh effect, Josephson junctions, Solitons, Langevin equation
Thermodynamic Uncertainty Relations for Coherent Transport
Research article | Nonequilibrium & irreversible thermodynamics | 2025-07-23 06:00 EDT
Kay Brandner and Keiji Saito
We derive a universal thermodynamic uncertainty relation for fermionic coherent transport, which bounds the total rate of entropy production in terms of the mean and fluctuations of a single particle current. This bound holds for any multiterminal geometry and arbitrary chemical and thermal biases, as long as no external magnetic fields are applied. It can further be saturated in two-terminal settings with boxcar-shaped transmission functions and reduces to its classical counterpart in linear response. Upon insertion of a numerical factor, our bound also extends to systems with broken time-reversal symmetry. As an application, we derive trade-off relations between the figures of merit of coherent thermoelectric heat engines and refrigerators, which show that such devices can attain ideal efficiency only at vanishing mean power or diverging power fluctuations. To illustrate our results, we work out a model of a coherent conductor consisting of a chain of quantum dots.
Phys. Rev. Lett. 135, 046302 (2025)
Nonequilibrium & irreversible thermodynamics, Quantum thermodynamics, Quantum transport, Stochastic thermodynamics
Approximate Symmetries, Insulators, and Superconductivity in the Continuum-Model Description of Twisted ${\mathrm{WSe}}_{2}$
Research article | Pairing mechanisms | 2025-07-23 06:00 EDT
Maine Christos, Pietro M. Bonetti, and Mathias S. Scheurer
Motivated by the recent discovery of superconductivity in twisted bilayer ${\mathrm{WSe}}_{2}$, we analyze the correlated physics in this system in the framework of a continuum model for the moir'e superlattice. Using the symmetries in a fine-tuned limit of the system, we identify the strong-coupling ground states and their fate when the perturbations caused by finite bandwidth, displacement field, and the phase of the intralayer potential are taken into account. We classify the superconducting instabilities and, employing a spin-fermion-like model, study the superconducting instabilities in proximity to these insulating particle-hole orders. This reveals that only a neighboring intervalley coherent phase (with zero or nonzero wave vector) is naturally consistent with the observed superconducting state, which we show to be crucially affected by the nontrivial band topology. Depending on details, the superconductor will be nodal or a chiral gapped state while further including electron-phonon coupling leads to a fully gapped, time-reversal symmetric pairing state.
Phys. Rev. Lett. 135, 046503 (2025)
Pairing mechanisms, Transition metal dichalcogenides, Twisted heterostructures, Unconventional superconductors
Microscopic Theory of Pair Density Waves in Spin-Orbit Coupled Kondo Lattice
Research article | FFLO | 2025-07-23 06:00 EDT
Aaditya Panigrahi, Alexei Tsvelik, and Piers Coleman
We demonstrate that the discommensuration between the Fermi surfaces of a conduction sea and an underlying spin liquid provides a natural mechanism for the spontaneous formation of pair density waves. Using a recent formulation of the Kondo lattice model that incorporates a Yao Lee spin liquid proposed by the authors, we demonstrate that doping away from half filling induces finite-momentum electron-Majorana pair condensation, resulting in amplitude-modulated pair density waves (PDWs). Our approach provides a precise, analytically tractable pathway for understanding the spontaneous formation of PDWs in higher dimensions and offers a natural mechanism for PDW formation in the absence of Zeeman splitting.
Phys. Rev. Lett. 135, 046504 (2025)
FFLO, Kondo effect, Pair density wave, Spin-triplet pairing, Superconductivity, Heavy-fermion systems
Microscopic Origin of Reduced Magnetic Order in a Frustrated Metal
Research article | Antiferromagnetism | 2025-07-23 06:00 EDT
X. Boraley, O. Stockert, J. Lass, R. Sibille, Ø. S. Fjellvåg, S. H. Moody, A. M. Läuchli, V. Fritsch, and D. G. Mazzone
Although magnetic frustration in metals provides a promising avenue for novel quantum phenomena, their microscopic interpretation is often challenging. Here, we use the face-centered cubic intermetallic ${\mathrm{HoInCu}}{4}$ as model material to show that Hamiltonians neglecting the charge degree of freedom are appropriate for frustrated metals possessing low density of states at the Fermi surface. Through neutron scattering techniques we determine matching magnetic exchange interactions in the paramagnetic and field-polarized states using an effective spin-1 Heisenberg Hamiltonian, for which we identify antiferromagnetic nearest and next-nearest-neighbor interactions ${J}{1}$ and ${J}{2}$ that are close to the critical ratio ${J}{2}/{J}_{1}=1/2$. The study further provides evidence that spin-wave theory fails to predict the low-energy spin dynamics in the antiferromagnetic zero-field state, which is dominated by overdamped magnetic excitations. We conclude that the low-energy fluctuations arise from quantum fluctuations, accounting for the missing moment of the strongly renormalized magnetic long-range order.
Phys. Rev. Lett. 135, 046702 (2025)
Antiferromagnetism, Frustrated magnetism, Magnons, Spin fluctuations, Metals, Inelastic neutron scattering, Neutron diffraction, Neutron scattering
Field-Induced Magnon Decays in Dipolar Quantum Magnets
Research article | Dipolar Rydberg atoms | 2025-07-23 06:00 EDT
Andrew D. Kim, Ahmed Khalifa, and Shubhayu Chatterjee
We investigate the spontaneous disintegration of magnons in two-dimensional ferromagnets and antiferromagnets dominated by long-range dipolar interactions. Analyzing kinematic constraints, we show that the unusual dispersion of dipolar ferromagnets in a uniform magnetic field precludes magnon decay at all fields, in sharp contrast to short-range exchange-driven magnets. However, in a staggered magnetic field, magnons can decay in both dipolar ferromagnets and antiferromagnets. Remarkably, such decays do not require a minimum threshold field, and happen over a nearly fixed fraction of the Brillouin zone in the XY limit, highlighting the significant role played by dipolar interactions. In addition, topological transitions in the decay surfaces lead to singularities in the magnon spectrum. Regularizing such singular behavior via a self-consistent approach, we make predictions for dynamical spin correlations accessible to near-term quantum simulators and sensors.
Phys. Rev. Lett. 135, 046703 (2025)
Dipolar Rydberg atoms, Long-range interactions, Magnons
Spin Dynamics in the Dirac U(1) Spin Liquid ${\mathrm{YbZn}}{2}{\mathrm{GaO}}{5}$
Research article | High magnetic fields | 2025-07-23 06:00 EDT
Hank C. H. Wu, Francis L. Pratt, Benjamin M. Huddart, Dipranjan Chatterjee, Paul A. Goddard, John Singleton, D. Prabhakaran, and Stephen J. Blundell
${\text{YbZn}}{2}{\mathrm{GaO}}{5}$ is a promising candidate for realizing a quantum spin liquid (QSL) state, particularly owing to its lack of significant site disorder. Pulsed-field magnetometry at 0.5 K shows magnetization saturating near 15 T, with a corrected saturation moment of $2.1(1){\mu }_{\mathrm{B}}$ after subtracting the van Vleck contribution. Our zero-field $\mathrm{\mu }\mathrm{SR}$ measurements down to milliKelvin temperatures provide evidence for a dynamic ground state and the absence of magnetic order. To probe fluctuations in the local magnetic field at the muon site, we performed longitudinal field $\mathrm{\mu }\mathrm{SR}$ experiments. These results provide evidence for spin dynamics with a field dependence that is consistent with a U1A01 Dirac quantum spin liquid as a plausible description of the ground state.
Phys. Rev. Lett. 135, 046704 (2025)
High magnetic fields, Quantum entanglement, Quantum spin liquid, Spin dynamics, Spin liquid, Density functional calculations, Muon spin relaxation & rotation
Deterministic Double-Zero Media and Robust Wave Manipulation Using a Phononic Weyl Semimetal
Research article | Acoustic metamaterials | 2025-07-23 06:00 EDT
Changqing Xu, Jinjie Shi, Xiaozhou Liu, Ze-Guo Chen, Ying Wu, and Yun Lai
Double-zero media exhibit unparalleled impedance-independent wave manipulation properties. However, their reliance on accidental degeneracy makes them fragile to disturbances in structural geometry and material parameters. Here, we propose a topological approach to address this limitation. By constructing a Weyl semimetal with uniaxial screw symmetry, which exhibits a charge-2 Weyl point at the Brillouin zone center, we propose a deterministic directional double-zero medium characterized by linear dispersion along one direction and quadratic dispersion along the perpendicular directions, leading to impedance-independent total transmission and divergent impedance mismatch along different directions. By experimentally constructing this Weyl semimetal, we have observed the existence of a charge-2 Weyl point and its unique wave manipulation capabilities as directional double-zero media, including frequency-tunable wave collimation and a configurable transition between positive and negative refraction. These findings open new pathways for realizing topology-protected metamaterials with unprecedented capabilities for bulk-wave manipulation.
Phys. Rev. Lett. 135, 046902 (2025)
Acoustic metamaterials, Phononic crystals, Photonic crystals, Topological materials
Indirect Band Nature of Atomically Thin Hexagonal Boron Nitride Identified by Resonant Excitation in the Deep Ultraviolet Regime
Research article | Electronic structure | 2025-07-23 06:00 EDT
Lei Fu, Yuqing Hu, Ning Tang, Junxi Duan, Xionghui Jia, Huaiyuan Yang, Zhuoxian Li, Xiangyan Han, Guoping Li, Jianming Lu, Lun Dai, Weikun Ge, Yugui Yao, and Bo Shen
Multiple spectroscopic measurements, including photoluminescence, Raman, and reflectance contrast spectroscopy in deep-UV regime on monolayer and few-layer hexagonal boron nitride confirm an indirect bandgap in the material.
Phys. Rev. Lett. 135, 046903 (2025)
Electronic structure, Excitons, Flat bands, Nanophotonics, Optoelectronics, 2-dimensional systems, Boron nitride, Wide band gap systems, Photoabsorption, Photoluminescence, Raman spectroscopy
Topology-Controlled Microphase Separation and Interconversion of Twist and Writhe Domains in Supercoiled Annealed Polyelectrolytes
Research article | Electrostatic interactions | 2025-07-23 06:00 EDT
Roman Staňo, Christos N. Likos, Davide Michieletto, and Jan Smrek
In closed circular ribbonlike polymers such as deoxyribonucleic acid, twist and writhe are known to be largely determined by the polymer’s bending and torsional rigidities, and they must sum to a topological constant. Using molecular simulations and an analytically solvable Landau theory, we study the interplay between ribbon topology and chemically annealed charges in a model polyelectrolyte. We show that the repulsions between like-charged acidic sites trigger phase separation and coexistence of supercoiling domains, in turn unveiling a complex phase diagram and providing a route to control the properties of deoxyribonucleic acid-based materials.
Phys. Rev. Lett. 135, 048101 (2025)
Electrostatic interactions, Landau theory, Phase separation, Phase transitions, Polymer conformation & topology, Polymer conformation changes, Charged polymers, Polyelectrolytes, Wormlike chain, Molecular dynamics, Monte Carlo methods
Revealing Actual Viscoelastic Relaxation Times in Capillary Breakup
Research article | Interfacial flows | 2025-07-23 06:00 EDT
Nan Hu, Jonghyun Hwang, Tachin Ruangkriengsin, and Howard A. Stone
We use experiments and theory to elucidate the size effect in capillary breakup rheometry, where prestretching in the viscocapillary stage causes the apparent relaxation time to be consistently smaller than the actual value. We propose a method accounting for both the experimental size and the finite extensibility of polymers to extract the actual relaxation time. A phase diagram characterizes the expected measurement variability and delineates scaling law conditions. The results refine capillary breakup rheometry for viscoelastic fluids and advance the understanding of breakup dynamics across scales.
Phys. Rev. Lett. 135, 048201 (2025)
Interfacial flows, Polymer solutions, Viscoelasticity
Dislocation Glides in Granular Media
Research article | Crystal defects | 2025-07-23 06:00 EDT
Fumiaki Nakai, Takashi Uneyama, Yuto Sasaki, Kiwamu Yoshii, and Hiroaki Katsuragi
Atomic crystals with dislocations deform plastically at low stresses via dislocation glide. Whether dislocation glide occurs in macroscopic frictional granular media remains unknown. We simulate structural and rheological responses of a granular crystal with an edge dislocation. We discover that dislocation glide occurs at low interparticle friction coefficients, whereas at high friction, the crystal order breaks down. When the dislocation glide occurs, the yield stress is markedly lower than in dislocation-free crystals and varies linearly with the interparticle friction coefficient. The linear dependence arises from both the elastic barrier associated with the Peierls stress and the interparticle friction slip criteria.
Phys. Rev. Lett. 135, 048202 (2025)
Crystal defects, Plastic deformation, Granular materials, Granular solids, Molecular dynamics
Friction Measurements with Picoliter Droplets Using Scanning Probe Microscopy
Research article | Drop interactions | 2025-07-23 06:00 EDT
Diego Cortés, Michael Kappl, Hans-Jürgen Butt, Pranav Sudersan, and Tomas P. Corrales
Topographical and chemical defects on solid surfaces tend to pin three-phase contact lines of moving liquid drops. Our quantitative understanding of the pinning process is, however, still poor. Here we use an atomic force microscope to slide $\approx 100\text{ }\text{ }\mathrm{pL}$ droplets of water-glycerol mixtures over hydrophobic surfaces and measure friction forces. By using picoliter droplets, the sensitivity for detecting processes at the contact line is enhanced. We have found that only a region $<200\text{ }\text{ }\mathrm{nm}$ around the contact line contributes to friction. By imaging isolated nanospherical defects, we could quantify the force and energy dissipation when the front and rear of the droplet passes the defect and compare it to theory.
Phys. Rev. Lett. 135, 048203 (2025)
Drop interactions, Friction, Hydrophobic interactions, Wetting, Gas-liquid interfaces, Liquid-solid interfaces, Surfaces, Atomic force microscopy
Physical Review X
Thermal Avalanches Drive Logarithmic Creep in Disordered Media
Research article | Creep | 2025-07-23 06:00 EDT
Daniel J. Korchinski, Dor Shohat, Yoav Lahini, and Matthieu Wyart
Creep in disordered materials arises from progressively harder local rearrangements, which trigger each other in slow sequences termed thermal avalanches.
Phys. Rev. X 15, 031024 (2025)
Creep, Amorphous materials, Disordered systems
arXiv
Spontaneous Emergence of Phase Coherence in a quasiparticle Bose-Einstein Condensate
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-24 20:00 EDT
Malte Koster, Matthias R. Schweizer, Timo Noack, Vitaliy I. Vasyuchka, Dmytro A. Bozhko, Burkard Hillebrands, Mathias Weiler, Alexander A. Serga, Georg von Freymann
Since their prediction by Einstein at the dawn of quantum mechanics, Bose-Einstein condensates (BECs), owing to their property to show quantum phenomena on macroscopic scales, are drawing increasing attention across various fields in physics. They are the subject of many fascinating observations in various physical systems, from liquid helium to diluted atomic gases. In addition to real particles like atoms and composite bosons such as Cooper pairs or excitons, this phenomenon is also observed in gases of quasiparticles such as polaritons and magnons - quanta of spin-wave excitations in magnetic media. The fundamental property of the BEC state is its coherence, which is represented by a precisely defined phase of the corresponding wave function, which arises spontaneously and encompasses all particles gathered at the bottom of their spectrum. Until now, the BEC phase was only revealed in phenomena depending on the spatial phase difference, such as interference, second order coherence, and macroscopic BEC motions - supercurrents, superfluidity and Josephson oscillations. Here, we present a method for the direct time-domain measurement of the magnon BEC coherent state phase relative to an outside reference signal. We report the emergence of spontaneous coherence from a freely evolving magnon gas, which manifests as the condensation of magnons into a uniform precession state with minimal energy and a well-defined phase. These findings confirm all postulated fundamental properties of quasiparticle condensates, provide access to a new degree of freedom in such systems, and open up the possibility of information processing using microwave-frequency magnon BECs.
Quantum Gases (cond-mat.quant-gas)
17 pages, 6 figures
Superconductivity in kagome metals due to soft loop-current fluctuations
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-24 20:00 EDT
Daniel J. Schultz, Grgur Palle, Yong Baek Kim, Rafael M. Fernandes, Jörg Schmalian
We demonstrate that soft fluctuations of translation symmetry-breaking loop currents provide a mechanism for unconventional superconductivity in kagome metals that naturally addresses the multiple superconducting phases observed under pressure. Focusing on the rich multi-orbital character of these systems, we show that loop currents involving both vanadium and antimony orbitals generate low-energy collective modes that couple efficiently to electrons near the Fermi surface and mediate attractive interactions in two distinct unconventional pairing channels. While loop-current fluctuations confined to vanadium orbitals favor chiral $ d+id$ superconductivity, which spontaneously breaks time-reversal symmetry, the inclusion of antimony orbitals stabilizes an $ s^{\pm}$ state that is robust against disorder. We argue that these two states are realized experimentally as pressure increases and the antimony-dominated Fermi surface sheet undergoes a Lifshitz transition.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
13 + 4 pages; 6+3 figures
Superfluid stiffness of superconductors with delicate topology
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-24 20:00 EDT
Tijan Prijon, Sebastian D. Huber, Kukka-Emilia Huhtinen
We consider superconductivity in two-dimensional delicate topological bands, where the total Chern number vanishes but the Brillouin zone can be divided into subregions with a quantized nontrivial Chern number. We formulate a lower bound on the geometric contribution to the superfluid weight in terms of the sum of the absolute values of these sub-Brillouin zone Chern numbers. We verify this bound in Chern dartboard insulators, where the delicate topology is protected by mirror symmetry. In iso-orbital models, where the mirror representation is the same along all high-symmetry lines, the lower bound increases linearly with the number of mirror planes. This work points to delicate bands as promising candidates for particularly stable superconductivity, especially in narrow bands where the kinetic energy is suppressed due to lattice effects.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
7+3 pages, 5 figures
Exact downfolding and its perturbative approximation
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Jonas B. Profe, Jakša Vučičević, P. Peter Stavropoulos, Malte Rösner, Roser Valentí, Lennart Klebl
Solving the many-electron problem, even approximately, is one of the most challenging and simultaneously most important problems in contemporary condensed matter physics with various connections to other fields. The standard approach is to follow a divide and conquer strategy that combines various numerical and analytical techniques. A crucial step in this strategy is the derivation of an effective model for a subset of degrees of freedom by a procedure called downfolding, which often corresponds to integrating out energy scales far away from the Fermi level. In this work we present a rigorous formulation of this downfolding procedure, which complements the renormalization group picture put forward by Honerkamp [PRB 85, 195129 (2012)}]. We derive an exact effective model in an arbitrarily chosen target space (e.g. low-energy degrees of freedom) by explicitly integrating out the the rest space (e.g. high-energy degrees of freedom). Within this formalism we state conditions that justify a perturbative truncation of the downfolded effective interactions to just a few low-order terms. Furthermore, we utilize the exact formalism to formally derive the widely used constrained random phase approximation (cRPA), uncovering underlying approximations and highlighting relevant corrections in the process. Lastly, we detail different contributions in the material examples of fcc Nickel and the infinite-layer cuprate SrCuO$ _2$ . Our results open up a new pathway to obtain effective models in a controlled fashion and to judge whether a chosen target space is suitable.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
13 pages, 8 figures and 6 pages appendix
Unveiling the Miniband Structure of Graphene Moiré Superlattices via Gate-dependent Terahertz Photocurrent Spectroscopy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
Juan A. Delgado-Notario, Stephen R. Power, Wojciech Knap, Manuel Pino, JinLuo Cheng, Daniel Vaquero, Takashi Taniguchi, Kenji Watanabe, Jesús E. Velázquez-Pérez, Yahya M. Meziani, Pablo Alonso-González, José M. Caridad
Moiré superlattices formed at the interface between stacked two-dimensional atomic crystals offer limitless opportunities to design materials with widely tunable properties and engineer intriguing quantum phases of matter. However, despite progress, precise probing of the electronic states and tantalizingly complex band textures of these systems remain challenging. Here, we present gate-dependent terahertz photocurrent spectroscopy as a robust technique to detect, explore and quantify intricate electronic properties in graphene moiré superlattices. Specifically, using terahertz light at different frequencies, we demonstrate distinct photocurrent regimes evidencing the presence of avoided band crossings and tiny (~1-20 meV) inversion-breaking global and local energy gaps in the miniband structure of minimally twisted graphene and hexagonal boron nitride heterostructures, key information that is inaccessible by conventional electrical or optical techniques. In the off-resonance regime, when the radiation energy is smaller than the gap values, enhanced zero-bias responsivities arise in the system due to the lower Fermi velocities and specific valley degeneracies of the charge carriers subjected to moiré superlattice potentials. In stark contrast, above-gap excitations give rise to bulk photocurrents – intriguing optoelectronic responses related to the geometric Berry phase of the constituting electronic minibands. Besides their fundamental importance, these results place moiré superlattices as promising material platforms for advanced, sensitive and low-noise terahertz detection applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
6 figures
ACS Nano 2025
Rigidity control of general origami structures
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Origami, the traditional paper-folding art, has inspired the modern design of numerous flexible structures in science and engineering. In particular, origami structures with different physical properties have been studied and utilized for various applications. More recently, several deterministic and stochastic approaches have been developed for controlling the rigidity or softness of the Miura-ori structures. However, the rigidity control of other origami structures is much less understood. In this work, we study the rigidity control of general origami structures via enforcing or relaxing the planarity condition of their polygonal facets. Specifically, by performing numerical simulations on a large variety of origami structures with different facet selection rules, we systematically analyze how the geometry and topology of different origami structures affect their degrees of freedom (DOF). We also propose a hypergeometric model based on the selection process to derive theoretical bounds for the probabilistic properties of the rigidity change, which allows us to identify key origami structural variables that theoretically govern the DOF evolution and thereby the critical rigidity percolation transition in general origami structures. Moreover, we develop a simple unified model that describes the relationship between the critical percolation density, the origami facet geometry, and the facet selection rules, which enables efficient prediction of the critical transition density for high-resolution origami structures. Altogether, our work highlights the intricate similarities and differences in the rigidity control of general origami structures, shedding light on the design of flexible mechanical metamaterials for practical applications.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
Speed of sound in dense simple liquids
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
The speed of sound of simple dense fluids is shown to exhibit a pronounced freezing temperature scaling of the form $ c_{\rm s}/v_{\rm T}\simeq \sqrt{\gamma} +\alpha (T_{\rm fr}/T)^{\beta}$ , where $ c_s$ is the speed of sound, $ v_{\rm T}$ is the characteristic thermal velocity, $ \gamma$ is the ideal gas heat capacity ratio, $ T$ is the temperature, $ T_{\rm fr}$ is the freezing temperature, and $ \alpha$ and $ \beta$ are dimensionless parameters. For the Lennard-Jones fluid we get $ \gamma=5/3$ , $ \alpha\simeq 7$ with a weak temperature dependence, and $ \beta = 1/3$ . Similar scaling works in several real liquids, such as argon, krypton, xenon, nitrogen, and methane. In this case, $ \alpha$ and $ \beta$ are substance-dependent fitting parameters. A comparison between the prediction of this freezing temperature scaling and a recent experimental measurement of the speed of sound in methane under conditions of planetary interiors is presented and discussed. The results provide a simple practical tool to estimate the speed of sound in regimes where no experimental data are yet available.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Chemical Physics (physics.chem-ph)
Physical Review E 111, 065423 (2025)
Space-time crystals from particle-like topological solitons
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Hanqing Zhao, Ivan I. Smalyukh
Time crystals are unexpected states of matter that spontaneously break time translation symmetry either in a discrete or continuous manner. However, spatially-mesoscale space-time crystals that break both the space and time symmetries have not been reported. Here we report a continuous space-time crystal in a nematic liquid crystal driven by ambient-power, constant-intensity unstructured light. Our numerically constructed 4-dimensional configurations exhibit good agreement with these experimental findings. While meeting the established criteria to identify time-crystalline order, both experiments and computer simulations reveal a space-time crystallization phase formed by particle-like topological solitons. The robustness against temporal perturbations and spatiotemporal dislocations shows the stability and rigidity of the studied space-time crystals, which relates to their locally topological nature and many-body interactions between emergent spontaneously-twisted, particle-like solitonic building blocks. Their potential technological utility includes optical devices, photonic space-time crystal generators, telecommunications, and anti-counterfeiting designs, among others.
Soft Condensed Matter (cond-mat.soft)
44 pages, 14 figures
Emergent discrete space-time crystal of Majorana-like quasiparticles in chiral liquid crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Hanqing Zhao, Rui Zhang, Ivan I. Smalyukh
Time crystals spontaneously break the time translation symmetry, as recently has been frequently reported in quantum systems. Here we describe the observation of classical analogues of both 1+1-dimensional and 2+1-dimensional discrete space-time crystals in a liquid crystal system driven by a Floquet electrical signal. These classical time crystals comprise particle-like structural features and exists over a wide range of temperatures and electrical driving conditions. The phenomenon-enabling period-doubling effect comes from their topological Majorana-like quasiparticle features, where periodic inter-transformations of co-existing topological solitons and disclinations emerge in response to external stimuli and play pivotal roles. Our discrete space-time crystals exhibit robustness against temporal perturbations and spatial defects, behaving like a time-crystalline analogues of a smectic phase. Our findings show that the simultaneous symmetry breaking in time and space can be a widespread occurrence in numerous open systems, not only in quantum but also in a classical soft matter context.
Soft Condensed Matter (cond-mat.soft)
42 pages,10 figures
Modifying electronic and structural properties of 2D van der Waals materials via cavity quantum vacuum fluctuations: A first-principles QEDFT study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Hang Liu, Simone Latini, I-Te Lu, Dongbin Shin, Angel Rubio
Structuring the photon density of states and light-matter coupling in optical cavities has emerged as a promising approach to modifying the equilibrium properties of materials through strong light-matter interactions. In this article, we employ state-of-the-art quantum electrodynamical density functional theory (QEDFT) to study the modifications of the electronic and structural properties of two-dimensional (2D) van der Waals (vdW) layered materials by the cavity vacuum field fluctuations. We find that cavity photons modify the electronic density through localization along the photon polarization directions, a universal effect observed for all the 2D materials studied here. This modification of the electronic structure tunes the material properties, such as the shifting of energy valleys in monolayer h-BN and 2H-MoS$ _2$ , enabling tunable band gaps. Also, it tunes the interlayer spacing in bilayer 2H-MoS$ _2$ and T$ _\text{d}$ -MoTe$ _2$ , allowing for adjustable ferroelectric, nonlinear Hall effect, and optical properties, as a function of light-matter coupling strength. Our findings open an avenue for engineering a broad range of 2D layered quantum materials by tuning vdW interactions through fluctuating cavity photon fields.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
14 pages, 5 figures
Graphene Frontiers: Recent Advancements in Energy and Electronics Applications
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
Abdallah M. Abdeldaiem, Abdulrhman M. Alaraj, Ahmed K. Abozaid, Habiba E. Elsayegh, Mohamed A. Khamis, Mohamed M. Kedra, Mahmoud A. Elqassas, Ahmed M. Dowidar, Aya A. Esmaeil, Nora H. El mowafy, Fayza R. Ramadan, Walid J. Hamouda, Sara R. Ghazal, Haneen A. Saad, Naglaa M. Zian, Fatma Sameh, Alshimaa M. Rizk, Mena K. Selema, Aml F. Dawood, Ebrahem H. Abdelaal, Walid Ismail, Mahmoud Abdelfatah, Swellam W. Sharshir, Abdelhamid El-Shaer
This review article explores the synthesis, characterization, and potential applications of graphene, a two-dimensional material with exceptional properties. Graphene’s versatility in energy and electronics applications is highlighted, with its high conductivity and huge surface area facilitating improved energy storage capabilities in supercapacitors and batteries. In electronics, graphene is revolutionizing the industry by enabling the development of flexible displays, high-speed transistors, and improved thermal management systems. The integration of graphene into composite materials presents opportunities for stronger, lighter, and more conductive materials. The study provides a comprehensive overview of graphene’s current and future impact on technology, emphasizing its transformative potential in energy solutions and electronic advancements. In the energy sector, graphene’s integration into batteries, energy storage systems, capacitors, fuel cells, and renewable energy technologies signifies a leap forward in efficiency, capacity, and sustainability. In the electronics sector, graphene’s unique characteristics are utilized in RFID, sensors, and EMI shielding, leading to advancements in communication, security, and device miniaturization. The study underscores graphene’s potential to spearhead future innovations, reinforcing its status as a pivotal material in the ongoing technological evolution.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Thermophysical and Mechanical Properties Prediction of Rear-earth High-entropy Pyrochlore Based on Deep-learning Potential
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Yuxuan Wang, Guoqiang Lan, Huicong Chen, Jun Song
High-entropy pyrochlore oxides possess ultra-low thermal conductivity and excellent high-temperature phase stability, making them promising candidate for next-generation thermal barrier coating (TBC) materials. However, reliable predictive models for such complex and disordered systems remain challenging. Ab initio methods, although accurate in describing anharmonic phonon-phonon interactions, struggle to capture the strong inherent phonon-disorder scattering in high-entropy systems. Moreover, the limited simulation cell size, hundreds of atoms, cannot fully represent the configurational complexity of high-entropy phases. On the other hand, classical molecular dynamics (MD) simulations lack accurate and transferable interatomic potentials, particularly in multi-component systems like high-entropy ceramics. In this work, we employed Deep Potential Molecular Dynamics (DPMD) to predict the thermophysical and mechanical properties of rare-earth high-entropy pyrochlore oxide system. The deep-potential (DP) model is trained on a limited dataset from ab initio molecular dynamics (AIMD) calculations, enabling large-scale molecular dynamics simulations with on-the-fly potential evaluations. This model not only achieves high accuracy in reproducing ab initio results but also demonstrates strong generalizability, making it applicable to medium-entropy ceramics containing the same constituent elements. Our study successfully develops a deep potential model for rare-earth pyrochlore systems and demonstrates that the deep-learning-based potential method offers a powerful computational approach for designing high-entropy TBC materials.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
19 pages, 6 figures, 1 table
A Novel Discovery of Negative Thermal Expansion in Rare-earth Pyrochlore through Anion Order-Disorder Transition
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Yuxuan Wang, Guoqiang Lan, Jun Song
In this study, we report for the first time the occurrence and investigation of the negative thermal expansion (NTE) effect in rare-earth pyrochlores. It is found that the NTE originates from the migration of oxygen anions from 48f sites to 8b sites, where one-twelfth of the original anions gradually occupy half of the available oxygen vacancies. This initial rapid transition leads to the distortion and rotation of polyhedral units, effectively contracting the lattice and manifesting as macroscopic NTE. The transition is sensitive to external isotropic pressure, where increasing pressure delays the onset of anion migration. This study deepens our understanding of NTE in complex oxides and demonstrates the utility of deep learning potentials for exploring intricate structural behaviors.
Materials Science (cond-mat.mtrl-sci)
23 pages, 7 figures
Dopant-induced stabilization of three-dimensional charge order in cuprates
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Zheting Jin, Sohrab Ismail-Beigi
We investigate the microscopic mechanisms behind the stabilization of three-dimensional (3D) charge order by Pr doping in YBa$ _2$ Cu$ _3$ O$ _7$ (YBCO7). Density-functional-theory calculations locate the lowest-energy Pr superlattices for both Ba- and Y-site substitution. In the Ba-site case, the smaller Pr ion pulls the surrounding atoms inward. This breathing-mode distortion pins charge-stripe walls to the Pr columns and forces them to align along the $ c$ axis. Y-site Pr is larger than the host ion, produces an outward distortion, and fails to pin the stripes. Coarse-grained Monte-Carlo simulations show that the stripe correlation length rises in step with the structural correlation length of the Pr dopant as observed in prior experiments. We thus identify dopant-induced lattice pinning as the key mechanism behind 3D charge order in Pr-doped YBCO7. This approach provides quantitative guidelines for engineering electronic orders through targeted ionic substitution.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
16 pages, 14 figures
Fast 4D-STEM-based phase mapping for amorphous and mixed materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Andreas Werbrouck, Nikhila C. Paranamana, Xiaoqing He, Matthias J. Young
All materials are made from atoms arranged either in repeating (crystalline) or in random (amorphous) structures. Diffraction measurements probe average distances between atoms and/or planes of atoms. A transmission electron microscope in scanning mode (STEM) can collect spatially resolved 2-dimensional diffraction data, effectively creating a 4-dimensional (4D) hyperspectral dataset (4D-STEM). Interpretation strategies for such 4D data are well-developed for crystalline materials, because their diffraction spectra show intense peaks, allowing for effective phase and crystal orientation mapping at the nanoscale. Yet, because of the continuous nature of the diffraction data for amorphous and mixed materials, it is challenging to separate different amorphous contributions. Nonnegative matrix factorization (NMF) allows separation of 4D-STEM data into components with interpretable diffraction signatures and intensity maps, independent of the structure. However, NMF is a non-convex optimization problem and scales ~ O(nmk) with n the number of positions probed, m the number of diffraction features and k the number of components, making analysis of large 4D datasets inaccessible. Here, we apply QB decomposition as a preprocessing step for NMF (Randomized NMF or RNMF) to achieve scaling independent of the largest data dimension (~O(nk)), opening the door for NMF analysis of 4D-STEM data. We demonstrate our approach by mapping a thin TiO$ _2$ layer on top of SiO$ _2$ , and a LiNi$ _{0.6}$ Co$ _{0.2}$ Mn$ _{0.2}$ O$ _{2}$ (NMC) - Li$ _{10}$ GeP$ _2$ S$ _{12}$ (LGPS) mixed crystalline-amorphous battery interface, illustrating strengths and limitations of using RNMF for structure-independent phase mapping in 4D-STEM experiments.
Materials Science (cond-mat.mtrl-sci), Instrumentation and Detectors (physics.ins-det)
Successive orthorhombic distortions in kagome metals by molecular orbital formation
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Ryo Misawa, Shunsuke Kitou, Rinsuke Yamada, Tobi Gaggl, Ryota Nakano, Yudai Shibata, Yoshihiro Okamura, Markus Kriener, Yuiga Nakamura, Yoshichika Ōnuki, Youtarou Takahashi, Taka-hisa Arima, Milena Jovanovic, Leslie M. Schoop, Max Hirschberger
The kagome lattice, with its inherent frustration, hosts a plethora of exotic phenomena, including the emergence of $ 3\mathbf{q}$ charge density wave order. The high rotational symmetry, required to realize such an unconventional charge order, is broken in many kagome materials by orthorhombic distortions at high temperature, the origin of which is much less discussed despite their ubiquity. In this study, synchrotron X-ray diffraction reveals a structural phase transition from a parent hexagonal phase to an orthorhombic ground state, mediated by a critical regime of diffuse scattering in the prototypical kagome metals $ R$ Ru$ _3$ Si$ 2$ ($ R$ =rare-earth). Structural analysis uncovers an interlayer dimerization of kagome atoms in the low-temperature phase. Accordingly, a dimer model with one-dimensional disorder on kagome layers successfully reproduces the diffuse scattering. The observations point to molecular orbital formation between kagome $ 4d{z^2}$ orbitals as the driving force behind the transition, consistent with \textit{ab initio} calculations. A framework based on electronegativity and atomic radii is proposed to evaluate the stability of the hexagonal phase in kagome metals, guiding the design of highly symmetric materials.
Strongly Correlated Electrons (cond-mat.str-el)
Defect-Mediated Aggregation and Motility-Induced Phase Separation in Active XY Model
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
We propose an ``active XY model’’ that incorporates key elements of both the classical XY model and the Vicsek model to study the role of topological defects in active matter systems. This model features self-propelled particles with XY spin degrees of freedom on a lattice and introduces a self-propulsion parameter controlling the directional bias of particle motion. Using numerical simulations, we demonstrate that self-propulsion induces motility-induced phase separation (MIPS), where particles aggregate into clusters around topological defects with positive vortex charge. In contrast, negative charge defects tend to dissipate. We analyze the evolution of these clusters and show that their growth follows a two-stage exponential relaxation process, with characteristic time scaling as $ \tau \sim L^{3}$ with the system size $ L$ , reminiscent of first-order phase separation in equilibrium systems. Our results highlight the important role of topological defects in phase separations and clustering behavior in active systems, bridging nonequilibrium dynamics and equilibrium theory.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
29 pages, 17 figures
Exact solution of asymmetric gelation between three walks on the square lattice
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-24 20:00 EDT
Aleksander L Owczarek, Andrew Rechnitzer
We find and analyse the exact solution of a model of three different
polymers with asymmetric contact interactions in two dimensions, modelling a
scenario where there are different types of polymers involved. In particular, we find
the generating function of three directed osculating walks in star
configurations on the square lattice with two interaction Boltzmann weights,
so that there is one type of contact interaction between the top pair of walks and a
different interaction between the bottom pair of walks. These osculating
stars are found to be the most amenable to exact solution using functional
equation techniques in comparison to the symmetric case where three friendly
walks in watermelon configurations were successfully solved with the same
techniques. We elucidate the phase diagram, which has four phases, and find
the order of all the phase transitions between them. We also calculate the
entropic exponents in each phase.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Combinatorics (math.CO)
23 pages, 3 figures
Tunable spin-wave nonreciprocity in ferrimagnetic domain-wall channels
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Tingting Liu, Shuhong Li, Yunlong Liu, Shuchao Qin, Yang Liu, Wenjun Wang, Minghui Qin
The nonreciprocal propagation of spin waves (SWs) offers opportunities for developing novel functional magnonic logic devices, where controllability is crucial for magnetic signal processing. Domain walls act as natural waveguides due to their magnetic configuration, offering a platform for the in-depth investigation of nonreciprocal SW propagation and its manipulation. In this work, we theoretically and numerically investigate the tunable spin-wave nonreciprocity in ferrimagnetic domain-wall channels under the influence of an external field. It is revealed that the Dzyaloshinskii-Moriya interaction (DMI) exerts dual control over both nonreciprocal spin-wave propagation and spin-splitting phenomena. Moreover, SW nonreciprocity is magnetically tunable, with its sign reversibly switched by inverting the applied field direction, while preserving the host spin configuration. The orientation of the magnetic field can selectively stabilize or destabilize the domain wall structure, offering precise control over spin-wave nonreciprocity. Ultimately, we demonstrate a controllable SW transmission scheme via external magnetic field modulation, providing critical insights for the design of future magnonic devices.
Materials Science (cond-mat.mtrl-sci)
Time-hidden magnetic order in a multi-orbital Mott insulator
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Xinwei Li, Iliya Esin, Youngjoon Han, Yincheng Liu, Hengdi Zhao, Honglie Ning, Cora Barrett, Jun-Yi Shan, Kyle Seyler, Gang Cao, Gil Refael, David Hsieh
Photo-excited quantum materials can be driven into thermally inaccessible metastable states that exhibit structural, charge, spin, topological and superconducting orders. Metastable states typically emerge on timescales set by the intrinsic electronic and phononic energy scales, ranging from femtoseconds to picoseconds, and can persist for weeks. Therefore, studies have primarily focused on ultrafast or quasi-static limits, leaving the intermediate time window less explored. Here we reveal a metastable state with broken glide-plane symmetry in photo-doped Ca$ _2$ RuO$ _4$ using time-resolved optical second-harmonic generation and birefringence measurements. We find that the metastable state appears long after intralayer antiferromagnetic order has melted and photo-carriers have recombined. Its properties are distinct from all known states in the equilibrium phase diagram and are consistent with intralayer ferromagnetic order. Furthermore, model Hamiltonian calculations reveal that a non-thermal trajectory to this state can be accessed via photo-doping. Our results expand the search space for out-of-equilibrium electronic matter to metastable states emerging at intermediate timescales.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages main text, 4 figures, 21 pages supplementary information
Nature Physics 21, 451-457 (2025)
Altermagnetism and Weak Magnetism in the Insulating Distorted Perovskite Antiferromagnet NaOsO$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Hong-Suk Choi, M.-C. Jung, K.-H. Ahn, W. E. Pickett, K.-W. Lee
The GdFeO$ _3$ -type perovskite antiferromagnet NaOsO$ _3$ , calculated here to be altermagnetic for all three typical collinear antiferromagnetic orders, was suggested early on to be a Slater-type insulator, due in large part to its continuous metal-insulator transition and its small energy gap. Below the Néel temperature, the gap opens along with ``weak magnetism’’, accompanied by a discontinuity in the magnetic susceptibility. Most other properties remain continuous. Without explicit correlation in the band structure calculation, and neglecting spin-orbit coupling (SOC), already a gap opens. Inclusion of a modest on-site Coulomb repulsion ($ U\sim$ 1 eV) is sufficient to eliminate a SOC-induced small band overlap, reproducing the experimentally observed gap of several tens meV as reported earlier. This evidence supports the viewpoint that NaOsO$ _3$ lies in an unusual crossover region between Slater and Mott insulator. The unreported altermagnetism in NaOsO$ _3$ is demonstrated and its consequences are considered. The origin of the very weak magnetism has been investigated using a combination of {\it ab initio} calculations and symmetry analysis of the magnetic space group, confirming the origin lying in the Dzyaloshinskii-Moriya spin-orbit coupling buttressed by altermagnetic order. After determining the easy axis, our calculation leads to an Os spin canting angle of about 3$ ^{\circ}$ , accounting for the observed weak magnetism and the resulting discontinuity in the susceptibility. The altermagnetism spin-split bands (up to $ \sim$ 100 meV) result in a chiral-split magnon spectrum in both acoustic and optical modes in the THz range, and lead to significant anomalous Hall conductivity upon hole doping.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
13 pages with supplementary information
Weak in the boundary: How weak SPT phases spoil anomaly matching
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Daniel Sheinbaum, Omar Antolín Camarena
We show how weak symmetry protected topological (SPT) phases on systems with a boundary are not in 1-to-1 correspondence with weak SPT phases on fully periodic systems, breaking the standard anomaly inflow interpretation of SPT phases. We further discuss the implications for the crystalline equivalence principle (CEP).
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph)
Accepted for Publication in PRB
Mott Criticality as the Confinement Transition of a Pseudogap-Mott Metal
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Abhirup Mukherjee, S. R. Hassan, Anamitra Mukherjee, N. S. Vidhyadhiraja, A. Taraphder, Siddhartha Lal
The phenomenon of Mott insulation involves the localization of itinerant electrons due to strong local repulsion. Upon doping, a pseudogap (PG) phase emerges - marked by selective gapping of the Fermi surface without conventional symmetry breaking in spin or charge channels. A key challenge is understanding how quasiparticle breakdown in the Fermi liquid gives rise to this enigmatic state, and how it connects to both the Mott insulating and superconducting phases. Here, we develop a renormalization-based construction of strongly correlated lattice models that captures the emergence of the pseudogap phase and its transition to a Mott insulator. Applying a many-body tiling scheme to the fixed-point impurity model uncovers a lattice model with electron interactions and Kondo physics. At half-filling, the interplay between Kondo screening and bath charge fluctuations in the impurity model leads to Fermi liquid breakdown. This reveals a pseudogap phase characterized by a non-Fermi liquid (the Mott metal) residing on nodal arcs, gapped antinodal regions of the Fermi surface, and an anomalous scaling of the electronic scattering rate with frequency. The eventual confinement of holon-doublon excitations of this exotic metal obtains a continuous transition into the Mott insulator. Our results identify the pseudogap as a distinct long-range entangled quantum phase, and offer a new route to Mott criticality beyond the paradigm of local quantum criticality.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
24 pages, 12 figures
Phonon Dynamics of Topological Quantum Materials
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
The thesis presents a comprehensive Raman spectroscopic and first-principle density functional theory based investigation of V_(1-x)PS_(3) ; PbTaSe_(2) and 1T-TaS_(2). In V_(1-x)PS_(3),the detection of fractionalized excitations (Majorana fermions) suggests a potential Kitaev spin liquid phase, which becomes more pronounced as dimensionality decreases. Evidence of temperature-driven structural phase transition and topological surface phonons has been detected in PbTaSe_(2). TaS_(2) in 1T-phase reveals the presence of a hidden quantum state, a Mott-insulating phase, and a quantum spin liquid state. The observed phenomenon in these quantum systems makes them a promising candidate for advanced technologies such as quantum computing and communication.
Strongly Correlated Electrons (cond-mat.str-el)
PhD thesis
Group-I lead oxide X2PbO3 (X=Li, Na, K, Rb, and Cs) glass-like materials for energy applications: A hybrid-DFT study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
R. Zosiamliana, Lalhriat Zuala, Lalrinthara Pachuau, Lalmuanpuia Vanchhawng, S. Gurung, A. Laref, D. P. Rai
Pb-based compounds have garnered considerable theoretical and experimental attention due to their promising potential in energy-related applications. In this study, we explore the glass-like alkali metal lead oxides X2PbO3 (X=Li, Na, K, Rb, Cs) and assess their suitability for piezoelectric and thermoelectric applications. First-principles calculations were performed using hybrid density functional theory (DFT), incorporating B3LYP, HSE06, and PBE0 functionals. Among these, PBE0 is identified as the most accurate, yielding lattice parameters in close agreement with experimental data. Structural stability was confirmed through evaluation of thermal, mechanical, and formation energies. For the non-centrosymmetric orthorhombic phase Cmc21-X2PbO3 (X=K, Rb, Cs), piezoelectric constants were computed via both the numerical Berry phase (BP) method and the analytical Coupled Perturbed Hartree-Fock/Kohn-Sham (CPHF/KS) formalism. Notably, Cs2PbO3 exhibited a piezoelectric coefficient of e33 = 0.60 C m-2 (CPHF/KS), while K2PbO3 showed e32 = -0.51 Cm-2 (BP). Thermoelectric properties were investigated using the semiclassical Boltzmann transport theory within the rigid band approximation. The calculated thermoelectric performance reveals promising figures of merit (ZT), ranging from 0.3 to 0.63, suggesting these materials are applicable as future thermoelectric materials.
Materials Science (cond-mat.mtrl-sci)
Topological Zero Modes in Non-Hermitian Topolectrical Systems: Size and Impedance Control
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
S M Rafi-Ul-Islam, Zhuo Bin Siu, Md. Saddam Hossain Razo, Mansoor B.A. Jalil
We investigate the size-dependent behavior of topological zero modes (TZMs) in finite non-Hermitian Su-Schrieffer-Heeger (SSH) chains implemented on a topolectrical circuit platform. By deriving exact analytical solutions for the eigenenergies and band gaps of TZMs, we reveal their sensitivity to system size and non-Hermitian parameters, such as asymmetric coupling and onsite gain or loss. Our results show that non-Hermiticity enables the recovery of exactly zero-energy TZMs at a critical system size, unlike Hermitian systems where finite-size effects cause energy splitting. These zero-energy modes produce pronounced impedance peaks in the circuit’s admittance spectrum, providing a measurable signature of topological states. Additionally, a tunable grounding capacitor enables precise control of TZM energies at a fixed resonance frequency, enhancing practical tunability. Our findings offer insights into finite-size effects in non-Hermitian topological systems and guide the design of robust, reconfigurable topolectrical circuits for sensing and energy transfer applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Atomic and Molecular Clusters (physics.atm-clus)
15 pages, 9 figures
Restricted Boltzmann machine as a probabilistic Enigma
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-24 20:00 EDT
We theoretically propose a symmetric encryption scheme based on Restricted Boltzmann Machines that functions as a probabilistic Enigma device, encoding information in the marginal distributions of visible states while utilizing bias permutations as cryptographic keys. Theoretical analysis reveals significant advantages including factorial key space growth through permutation matrices, excellent diffusion properties, and computational complexity rooted in sharp P-complete problems that resist quantum attacks. Compatible with emerging probabilistic computing hardware, the scheme establishes an asymmetric computational barrier where legitimate users decrypt efficiently while adversaries face exponential costs. This framework unlocks probabilistic computers’ potential for cryptographic systems, offering an emerging encryption paradigm between classical and quantum regimes for post-quantum security.
Statistical Mechanics (cond-mat.stat-mech), Applied Physics (physics.app-ph), Data Analysis, Statistics and Probability (physics.data-an)
7 pages, 4 figures
Coupling of magnetic and lattice collective excitations in the 2D van der Waals antiferromagnet FePS$_{3}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Kartik Panda, Itzik Kapon, Dumitru Dumcenco, Dirk van der Marel, Alexey Kuzmenko, Nimrod Bachar
We report a comprehensive magneto-optical investigation of FePS$ _3$ single crystals using temperature-dependent polarized transmission spectroscopy and Faraday rotation measurements. Our data reveal pronounced in-plane anisotropy in both phonon and magnon excitations, emerging distinctly below the Néel temperature ($ T_N \approx 118$ K). A prominent magnon mode at 122 cm$ ^{-1}$ exhibits characteristic redshifting with increasing temperature and field-induced splitting, confirming its magnetic origin. The optical conductivity, extracted via Drude-Lorentz modeling, shows polarization-sensitive spectral changes across the magnetic transition. The appearance of Raman-active modes in the infrared spectra, along with the observation of multiple phonons contributing to Faraday rotation, provides compelling evidence for spin-phonon coupling and inversion symmetry breaking in the magnetically ordered state. These findings highlight the intricate interplay between spin and lattice degrees of freedom in FePS$ _3$ , positioning it as a model system for exploring spin-lattice interactions in two-dimensional antiferromagnets.
Strongly Correlated Electrons (cond-mat.str-el)
Mechanically and electrically switchable triferroic altermagnet in a pentagonal FeO2 monolayer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Deping Guo, Jiaqi Dai, Renhong Wang, Cong Wang, Wei Ji
Two-dimensional multiferroics promise low-power, multifunctional devices, yet the intrinsic coexistence and mutual control of three coupled ferroic orders in a single layer remains elusive. Here, we identify pentagonal monolayer FeO$ _2$ as an intrinsic triferroic altermagnet where ferroelectric (FE), ferroelastic (FA), and altermagnetic (AM) orders coexist and are tightly coupled, accompanied by a competing antiferroelectric (AFE) phase using first-principles calculations. The sole presence of glide mirror $ M_x$ symmetry in a FeO$ 2$ sublayer, with the breaking of four-fold rotation $ C{4z}$ symmetry, induces in-plane vector ferroelectricity and twin-related ferroelastic strains. Both FE and AFE phases break combined parity - time symmetry and display sizable altermagnetic spin splitting with Néel temperatures over 200~K. Electric-field-induced rotation of the FE polarization reverses the sign of the spin splitting, while in-plane uniaxial strain triggers ferroelastic switching that simultaneously rotates the FE polarization vector by $ 90^\circ$ and reverses the AM state. These electric-field- and strain-mediated pathways interlink six distinct polarization states that can be selected purely by electric fields and/or mechanical strain. This work extends intrinsic triferroicity to pentagonal monolayers and outlines a symmetry-based route toward mechanically and electrically configurable altermagnetic spintronics.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Fingerprints of collective magnetic excitations in inelastic electron tunneling spectroscopy
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Finnian Rist, Henry L. Nourse, Ben J. Powell
Spin-flip inelastic electron tunneling spectroscopy allows magnetic materials to be probed at the single-atom level via scanning tunneling microscopy. Previously, the local spectral weight of spin excitations of small systems has been deduced from discrete steps in the differential conductance. However, this is not viable for large systems. We show that the local spin density of states can be measured via the double differential conductance. This contrasts with elastic measurements where the local density of electronic states is deduced from the differential conductance. We study the tunneling currents of the spin-1/2 and -1 Heisenberg chains and propose a method to probe zero-frequency modes.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Role of temperature oscillation in growth of large-grain CdZnTe single crystal by traveling heater method
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
P. Vijayakumar, Subham Dhyani, K. Ganesan, R. Ramar, Edward Prabu Amaladass, R.M.Sarguna, S. Ganesamoorthy
Self-nucleation in CdZnTe crystal growth remains a significant challenge, despite numerous attempts to achieve large-grain single crystals by restricting multi-nucleation during growth process using the traveling heater method. In this study, we present a novel approach to achieve large-grain CdZnTe single crystals by introducing temperature oscillations above the crystallization temperature during the growth process. This method effectively suppresses secondary nucleation and promotes the preferential selection of a single grain during early stage of growth as well as along the growth axis, by reducing multi-nucleation. By adjusting the amplitude and the number of temperature oscillations, we have successfully grown CdZnTe single crystals with dimensions of 20 mm in diameter and 60 mm in length. The resulting crystals exhibited excellent compositional homogeneity, with a nearly constant resistivity of ~ 10^9 Ohm-cm and Te inclusions smaller than 15 microns along the growth axis. Additionally, the crystal elements were of detector grade achieving an energy resolution of 4.5% for gamma radiation at 662 keV from a 137Cs source in a quasi-hemispherical geometry. This study highlights the critical role of temperature oscillations in controlling secondary nucleation and promoting the formation of large-grain single crystals.
Materials Science (cond-mat.mtrl-sci)
17 pages, 9 figures
Beyond symmetry protection: Robust feedback-enforced edge states in non-Hermitian stacked quantum spin Hall systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
Conventional wisdom holds that strongly coupling two QSH layers yields a trivial $ \mathbb{Z}_2$ phase and no protected topological edge states. We demonstrate that, in a regime with intermediate inter-layer coupling (neither in the strong or weak coupling regimes) and competitive non-Hermitian directed amplification, bulk modes are suppressed while arbitrary bulk excitations inevitably accumulate into robust helical edge transport modes - without relying on any symmetry protection. Our feedback-enforced mechanism persists over broad parameter ranges and remains robust even on fractal or irregular boundaries. These findings challenge the traditional view of stacked QSH insulators as inevitably trivial, and open up new avenues for designing helical topological devices that exploit feedback-enforced non-Hermitian engineering, instead of symmetry-enforced robustness.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Mathematical Physics (math-ph), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
Any comments are welcome
Dissociation of one-dimensional excitons by static electric field
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
Adriana García, Alexander López, Jorge Quereda, Francisco Domínguez-Adame
The quantum states of an electron-hole pair in one-dimensional semiconductors under a static electric field are theoretically analyzed using a two-band model with on-site Coulomb interaction. In the absence of static field, the electron and hole are always bound, forming an exciton regardless of the Coulomb interaction strength, in contrast to what occurs in higher-dimensional semiconductors. The static field modifies the wave function of the electron-hole pair, turning bound states into continuum states. However, at low static fields, the linear optical spectra resemble those of the unbiased semiconductor, exhibiting a quadratic redshift of the main exciton absorption line as the field increases. When the static field exceeds a critical threshold, the exciton dissociates and the linear optical spectra exhibit signatures of the Wannier-Stark ladder with squally spaced peaks, making them a valuable tool for experimentally probing exciton dissociation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
pH-dependent interfacial rheology of polymer membranes assembled at liquid-liquid interfaces using hydrogen bonds
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Julien Dupré de Baubigny (SIMM), Corentin Tregouet (SIMM), Elena N. Govorun, Mathilde Reyssat, Patrick Perrin (SIMM), Nadège Pantoustier (SIMM), Thomas Salez (LOMA), Cécile Monteux (SIMM)
Self-assembly of polymers at liquid interfaces using non-covalent interactions has emerged as a promising technique to reversibly produce self-healing membranes. Besides the assembly process, it is also crucial to control the mechanical properties of these membranes. Here, we measure the interfacial rheological properties of PMAA-PPO (polymethacrylic acidpolypropylene oxide) polymer membranes assembled using hydrogen bonds at liquid-oil interfaces. Varying the pH enables us to modify the degree of ionization of the PMAA chains, and hence their ability to establish hydrogen interactions with PPO. Frequency sweeps of the interfacial layers show a crossover between a viscous regime at low frequencies and an elastic regime at high frequencies. The crossover elastic modulus decreases by half after one hour of the experiment over the pH range investigated, which can be accounted for by a decrease of the layer thickness as pH increases. Furthermore we find that the crossover frequency varies exponentially with the degree of ionization of PMAA. To account for these observations, we propose a simple picture where the short PPO chains behave as non-covalent cross-linkers that bridge several PMAA chains. The dissociation rate and hence the crossover frequency are controlled by the number of PO units per PPO chain involved in the hydrogen bonds.
Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph)
Giant Damping-like Torque Efficiency via Synergistic Spin Hall and enhanced Orbital Hall Effects
New Submission | Other Condensed Matter (cond-mat.other) | 2025-07-24 20:00 EDT
Subhakanta Das, Sabpreet Bhatti, Ramu Maddu, Bilal Jamshed, Go Dong Wook, S.N. Piramanayagam
Current-induced spin-orbit torque (SOT) has emerged as a promising method for achieving energy-efficient magnetisation switching in advanced spintronic devices. Over the past two decades, researchers have primarily focused on enhancing spin current generation through the spin Hall effect, relying predominantly on the spin degree of freedom (DoF) of the electron, while neglecting its orbital counterpart. Orbital Hall effect depends critically on the crystallinity and the interface between the orbital Hall layer and the orbital-to-spin conversion layer. However, most experimental works on orbital Hall effect relied on polycrystalline films with no special attention to improve the crystallographic texture. In this work, we have grown the Ru layer on a NiW seedlayer, which helped to improve the crystallographic texture, thereby enhancing the switching efficiency by over 44%. Such a huge increase in switching efficiency was achieved by (i) improving crystallographic texture and (ii) leveraging both spin and orbital DoFs. Our study underscores the potential for improving the spin-torque efficiency by combining interface engineering, orbital and spin Hall effects to drive next-generation spintronics.
Other Condensed Matter (cond-mat.other)
17 pages, 6 figures,
Symmetry re-breaking in an effective theory of quantum coarsening
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-24 20:00 EDT
Federico Balducci, Anushya Chandran, Roderich Moessner
We present a simple theory accounting for two central observations in a recent experiment on quantum coarsening and collective dynamics on a programmable quantum simulator [T. Manovitz et al., Nature 638, 86 (2025)]: an apparent speeding up of the coarsening process as the phase transition is approached; and persistent oscillations of the order parameter after quenches within the ordered phase. Our theory, based on the Hamiltonian structure of the equations of motion in the classical limit of the quantum model, finds a speeding up already deep within the ordered phase, with subsequent slowing down as the domain wall tension vanishes upon approaching the critical line. Further, the oscillations are captured within a mean-field treatment of the order parameter field. For quenches within the ordered phase, small spatially-varying fluctuations in the initial mean-field lead to a remarkable long-time effect, wherein the system dynamically destroys its long-range order and has to coarsen to re-establish it. We term this phenomenon symmetry re-breaking, as the resulting late-time magnetization can have a sign opposite to the initial magnetization.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Dynamic correlations in Calogero-Sutherland model
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-24 20:00 EDT
G. Lleopart Motis, D. M. Gangardt, M. Pustilnik, G. E. Astrakharchik
The Calogero-Sutherland model represents a paradigmatic example of an integrable quantum system with applications ranging from cold atoms to random matrix theory. Combining sum rules with the Monte Carlo technique, we introduce a stochastic method that allows one to compute the dynamic structure factor and obtain an exact description of excitations beyond the conventional Luttinger liquid regime. We explore a broad range of interaction regimes, including weak interactions, where a Bogoliubov-type spectrum emerges, the Tonks-Girardeau regime, where excitations resemble those of an ideal Fermi gas, and strong interactions, where umklapp scattering leads to a Brillouin zone structure, typical of a crystal. Additionally, we discuss the connection between the hydrodynamic description of one-dimensional quantum gases, liquids, and solids with the Calogero-Sutherland wave function. The model’s universality extends beyond atoms in waveguides, with implications for disordered systems and random matrix theory.
Quantum Gases (cond-mat.quant-gas)
9 pages, 3 figures, and End Matter
Quantum Monte Carlo simulation of light and superlight bipolarons in extended Hubbard-Holstein models on face- and body-centered-cubic lattices
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
G.D. Adebanjo, J.P. Hague, P.E. Kornilovitch
Superlight pairing of bipolarons driven by electron-phonon interactions (EPIs) in face-center-cubic (FCC) and body-center-cubic (BCC) lattices is investigated using a continuous-time path-integral quantum Monte Carlo (QMC) algorithm. The EPIs are of the Holstein and extended Holstein types, and a Hubbard interaction is also included. The number of phonons associated with the bipolaron, inverse mass, and radius are calculated and used to construct a phase diagram for bipolaron pairing (identifying the regions of pairing into intersite bipolarons and onsite bipolarons). From the inverse mass it is determined that for the extended interaction, there is a region of light pairing associated with intersite bipolarons formed in both BCC and FCC lattices. Intersite bipolarons in the extended model at large phonon frequency and large Coulomb repulsion become superlight due to first order hopping effects. The transition temperature of Bose–Einstein condensates of these pairs is estimated. It is determined that intersite bipolarons are associated with regions of high transition temperatures.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
12 pages, 8 figures
Revisiting the Impact of Single-Vacancy Defects on Electronic Properties of Graphene
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Mohammadamir Bazrafshan, Thomas. D. Kühne
While defects are generally considered to be unavoidable in experiments, engineering them is also a way of manipulating the physical properties of materials. In this study, the role of periodically arranged single vacancy defects in graphene is studied using the tight-binding method. Our numerical results show that single vacancy (SV) defects can exhibit predictable electronic behavior when they reside on the same sublattices (SS), following the armchair graphene nanoribbons (AGNRs) electronic band structure depending on the spacing between SVs. AGNRs are known to their tunable electronic band gap. However, when they are located on different sublattices (DS), the interaction between the defect-induced states becomes strong and can introduce anisotropy into the electronic band structure, demonstrating that the relative position of the SVs can also act as an additional degree of freedom for tuning the electronic properties. Interestingly, the behavior is independent of the density of SVs; for a system fully defected with SVs, the electronic properties depend heavily on the sublattices involved. The results provide a novel insight into sublattice-based defect engineering.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
From shallow to full wrapping: geometry and deformability dictate lipid vesicle internalization
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Stijn van der Ham, Alexander Brown, Halim Kusumaatmaja, Hanumantha Rao Vutukuri
The deformability of vesicles critically influences their engulfment by lipid membranes, a process central to endocytosis, viral entry, drug delivery, and intercellular transport. While theoretical models have long predicted this influence, direct experimental validation has remained elusive. Here, we combine experiments with continuum simulations to quantify how vesicle deformability affects the engulfment of small giant unilamellar vesicles (GUVs) by larger GUVs under depletion-induced adhesion. Using 3D confocal reconstructions, we extract vesicle shape, curvature, wrapping fraction, and the bendo-capillary length, a characteristic length scale that balances membrane bending and adhesion forces. We find that when vesicle size exceeds this length scale, engulfment is primarily governed by geometry. In contrast, when vesicle size is comparable to this scale, deformability strongly affects the transition between shallow, deep, and fully wrapped states, leading to suppression of full engulfment of vesicles. These findings connect theoretical predictions with direct measurements and offer a unified framework for understanding vesicle-mediated uptake across both synthetic and biological systems, including viral entry, synthetic cell design, drug delivery, and nanoparticle internalization.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
Pressure-tunable phase transitions in atomically thin Chern insulator MnBi$_2$Te$_4$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
Albin Marffy, Endre Tovari, Yu-Fei Liu, Anyuan Gao, Tianye Huang, Laszlo Oroszlany, Kenji Watanabe, Takashi Taniguchi, Su-Yang Xu, Peter Makk, Szabolcs Csonka
Topological insulators lacking time-reversal symmetry can exhibit the quantum anomalous Hall effect. Odd-layer thick MnBi$ _2$ Te$ _4$ is a promising platform due to its intrinsic magnetic nature, however, quantization is rarely observed in it. Our magnetoresistance measurements in the anti-ferromagnetic phase indicate, instead of a quantum anomalous Hall insulator, the presence of a trivial insulator state likely due to disorder, while at high magnetic field a Chern insulator state appears. By applying hydrostatic pressure we are able to tune the magnetic interactions and the characteristic energy scales in the phase diagram. The trivial band gap is reduced, suggesting the role of disorder decreases with the compression of the layers.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
18 pages, 13 figures
Chiral lone-pair helices with handedness coupling to electric-strain fields
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
C. R. Zeiger, R. S. Dragland, R. Sjökvist, R. Beanland, D. Meier, T. Grande, M. S. Senn, O. G. Grendal
Ferrochiral materials with an achiral-to-chiral phase transition and switchable chirality have unique application opportunities, enabling control of the angular momentum of circularly polarized lattice vibrations (chiral phonons) and chirality-related electronic phenomena. Materials that fall into this class are, however, extremely rare, and often accompanied by other types of ferroic order that interfere with the ferrochiral responses. In this work, we demonstrate ferrochirality in two tetragonal tungsten bronzes, K4Bi2Nb10O30 and Rb4Bi2Nb10O30. Using high-resolution X-ray powder diffraction combined with transmission electron microscopy, we solve the incommensurately modulated and chiral structures. Temperature dependent X-ray powder diffraction reveals that both materials undergo an achiral-to-chiral phase transition from P4/mbm to P4212(00{\gamma})q00. The chirality originates from a cooperative helical displacement of Bi3+ atoms perpendicular to the c direction and represents the primary order parameter. As a secondary effect of the ferrochiral order, a spatially varying piezoelectric response is observed, consistent with the polycrystalline nature of the investigated materials. Through invariant analysis, an external electric-strain-field coupling with the piezoelectricity is proposed as a conjugate field for switching chirality, establishing tetragonal tungsten bronzes as a versatile playground for the emergent field of ferrochirality.
Materials Science (cond-mat.mtrl-sci)
32 pages, 16 figures, to be submitted to Advanced Materials, Wiley
Spin-dependent Off-Axis Holography in Magnetic Environments
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-24 20:00 EDT
Nejc Blaznik, Dries van Oosten, Peter van der Straten
Nondestructive spin-resolved imaging of ultracold atomic gases requires calculating the differences of the refractive indices seen by two circular probe polarizations. Perfect overlap of the two images, corresponding to two different polarizations, is required well below the feature size of interest. In this paper, we demonstrate that the birefringence of atoms in magnetic field gradients results in polarization-dependent aberrations in the image, which deteriorates the overlap. To that end, we develop a model that couples atomic tensor polarizability with position-dependent spin orientation and yields aberration predictions for accumulated phase shifts in arbitrary field geometries. Applied to data from an ultra-cold atomic cloud trapped in a Ioffe-Pritchard trap, the model quantitatively reproduces the observed distortion across a range of temperatures. A residual offset of $ \sim1;\mu\mathrm{m}$ remains even under uniform field conditions, likely due to optical asymmetries. For images obtained through off-axis holography, the full complex field of the probe enables post-processing removal of all magnetically induced aberrations through a single numerically calculated Fourier-space phase mask.
Quantum Gases (cond-mat.quant-gas)
11 pages, 5 figures
Universality of Alpha-Relaxation in Glasses
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-24 20:00 EDT
Valeriy V. Ginzburg, Oleg Gendelman, Riccardo Casalini, Alessio Zaccone
In the vicinity of the glass transition, the characteristic relaxation time (e.g., the alpha-relaxation time in dielectric spectroscopy) of a glass-former exhibits a strongly super-Arrhenius temperature dependence, as compared to the classical Arrhenius behavior at high temperatures. A comprehensive description of both regions thus requires five parameters. Here, we demonstrate that many glass-formers exhibit a universal scaling, with only two material-specific parameters setting the timescale and the temperature scale; the other three being universal constants. Furthermore, we show that the master curve can be described by the recently developed two-state, two-(time) scale (TS2) theory (Soft Matter 2020, 16, 810) and regress the universal TS2 parameters. We also show the connection between the TS2 model and the Hall-Wolynes elastic relaxation theory.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
Will be submitted to Phys. Rev. Lett
Magnetic-Field Tunable Möbius and Higher-Order Topological Insulators in Three-Dimensional Layered Octagonal Quasicrystals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
Yuxiao Chen, Zhiming Xu, Citian Wang, Huaqing Huang
We propose that three-dimensional layered octagonal quasicrystals can host magnetic-field-tunable Möbius insulators and various higher-order topological insulators (HOTIs), enabled by the interplay of quasicrystalline symmetry and magnetic order. By constructing a minimal model based on stacked Ammann-Beenker tilings with magnetic exchange coupling and octagonal warping, we demonstrate that an A-type antiferromagnetic (AFM) configuration yields a topological phase protected by an effective time-reversal symmetry $ \mathcal{S}=\mathcal{T}\tau_{1/2}$ . Breaking $ \mathcal{S}$ via an in-plane magnetic field induced canting of the AFM order while preserving a nonsymmorphic glide symmetry $ \mathcal{G}n=\tau{1/2}\mathcal{M}_n$ leads to Möbius-twisted surface states, realizing a Möbius insulator in an aperiodic 3D system. Furthermore, we show that the quasicrystal with a general magnetic configuration supports multiple HOTI phases characterized by distinct hinge mode configurations that can be switched by rotating the magnetic field. A low-energy effective theory reveals that these transitions are driven by mass kinks between adjacent surfaces. Our work establishes a platform for realizing symmetry-protected topological phases unique to quasicrystals and highlights the tunability of hinge and surface states via magnetic control.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The Influence of Electric Field on the Anisotropic Dispersion of the Flexocoupling Induced Phonons and Ferrons in Van der Waals Ferrielectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Anna N. Morozovska, Eugene A. Eliseev, Yujie Zhu, Yulian M. Vysochanskii, Venkatraman Gopalan, Long-Qing Chen, Jia-Mian Hu
As has been shown recently, the influence of the flexoelectric coupling (shortly “flexocoupling”) on the fluctuations of electric polarization and elastic strains can lead to the principal changes of the dispersion law of soft optical and acoustic phonons (shortly “flexophonons”) and ferrons (shortly “flexoferrons”) in van der Waals ferrielectrics. Analytical results, derived in the framework of Landau-Ginzburg-Devonshire approach, revealed that the dispersion of flexophonons and flexoferrons is strongly anisotropic and should depend on the magnitude and direction of applied electric field. In this work we study the influence of applied electric field on the anisotropic dispersion of the flexophonons and flexophonons in a uniaxial van der Waals ferrielectric CuInP2S6. We reveal that the frequency of acoustic flexophonons and flexoferrons tends to zero at nonzero wavevectors under increase of applied electric field. We relate the changes with a possible appearance of a spatially modulated incommensurate polar phase induced by the flexocoupling in external field. The critical strength of flexocoupling is determined by the magnitude of electric field and direction of the wavevector. This allows us to propose a method for estimating the strength of flexocoupling in van der Waals ferrielectrics, providing that the frequency of the acoustic flexophonon is zeroing at the threshold value of the electric field. Since the flexoelectric coefficients are poorly known in van der Waals ferrielectrics, obtained analytical results can be useful for their flexo-engineering.
Materials Science (cond-mat.mtrl-sci)
30 pages, including 4 figures and Supporting Information. To be submitted to the Journal of Applied Physics, Special Topic “Flexoelectric Engineering: from Fundamentals to Emerging Technologies”. arXiv admin note: text overlap with arXiv:2503.06305
Exact results for active particle models: from long-range interactions to first-passage properties
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-24 20:00 EDT
The goal of this thesis is to obtain new exact results for models of active particles in one dimension, focusing on two different aspects: their behavior in the presence of long-range interactions and their first-passage properties. In the first part we give an overview of existing exact results both for active particle models and for Brownian particles with long-range interactions (Riesz gases). The next two parts focus on how methods from these two fields can be combined and extended to derive new results for models of active particles with long-range interactions. In part two, we study the density of particles in the stationary state, in the limit where the number of particles is very large, using an extension of the Dean-Kawasaki equation to run-and-tumble particles (RTPs). In the case of the 1D Coulomb interaction (attractive or repulsive), we obtain exact expressions for the stationary density for different types of confining potentials, which sheds lights on new non-equilibrium phase-transitions. Some results are also obtained for a repulsive 2D Coulomb interaction (log-gas), although the single-file constraint makes the study more difficult in this case. In part three, we focus on the fluctuations at the tagged particle level. In the limit of weak noise, we compute exactly and analyze in different regimes a variety of correlation functions of the particle positions and interparticle distances, both for the Brownian Riesz gas and for its active counterpart, and show that the activity plays an important role both at short times and at small distances. The last part of this thesis focuses on Siegmund duality, which connects the first-passage properties of a stochastic process with absorbing boundaries to its spatial distribution with hard walls. We extend this duality to a new class of stochastic processes, which includes active particles and diffusing diffusivity models.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft), Mathematical Physics (math-ph), Probability (math.PR)
PhD thesis defended on June 12, 2025 at Ecole Normale Supérieure (ENS), Paris. 214 pages
Graph Neural Network Approach to Predicting Magnetization in Quasi-One-Dimensional Ising Systems
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-24 20:00 EDT
V. Slavin, O. Kryvchikov, D. Laptev
We present a graph-based deep learning framework for predicting the magnetic properties of quasi-one-dimensional Ising spin systems. The lattice geometry is encoded as a graph and processed by a graph neural network (GNN) followed by fully connected layers. The model is trained on Monte Carlo simulation data and accurately reproduces key features of the magnetization curve, including plateaus, critical transition points, and the effects of geometric frustration. It captures both local motifs and global symmetries, demonstrating that GNNs can infer magnetic behavior directly from structural connectivity. The proposed approach enables efficient prediction of magnetization without the need for additional Monte Carlo simulations.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG)
18 pages, 4 figures
Coincidence double-tip scanning tunneling spectroscopy
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Yuehua Su, Guoya Zhang, Dezhong Cao, Chao Zhang
The development of new experimental techniques for direct measurement of many-body correlations is crucial for unraveling the mysteries of strongly correlated electron systems. In this work, we propose a coincidence double-tip scanning tunneling spectroscopy (STS) that enables direct probing of spatially resolved dynamical two-body correlations of sample electrons. Unlike conventional single-tip scanning tunneling microscopy, the double-tip STS employs a double-tip scanning tunneling microscope (STM) equipped with two independently controlled tips, each biased at distinct voltages ($ V_1$ and $ V_2$ ). By simultaneously measuring the quantum tunneling currents $ I_1(t)$ and $ I_2(t)$ at locations $ j_1$ and $ j_2$ , we obtain a coincidence tunneling current correlation $ \overline{\langle I_1(t) I_2(t)\rangle}$ . Differentiating this coincidence tunneling current correlation with respect to the two bias voltages yields a coincidence dynamical conductance. Through the development of a nonequilibrium theory, we demonstrate that this coincidence dynamical conductance is proportional to a contour-ordered second-order current correlation function. For the sample electrons in a nearly free Fermi liquid state, the coincidence dynamical conductance captures two correlated dynamical electron propagation processes: (i) from $ j_1$ to $ j_2$ (or vice versa) driven by $ V_1$ , and (ii) from $ j_2$ to $ j_1$ (or vice versa) driven by $ V_2$ . For the sample electrons in a superconducting state, additional propagation channels emerge from the superconducting condensate, coexisting with the above normal electron propagation processes. Thus, the coincidence double-tip STS provides direct access to spatially resolved dynamical two-body correlations, offering a powerful tool for investigating strongly correlated electron systems.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
22 pages, 2 figures
Hydrogen modes in KDP under pressure from ab initio calculation and inelastic neutron scattering
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
V. A. Abalmasov, A. S. Ivanov, R. A. Sadykov, A. V. Belushkin
The nature of the phonon triplet in the region of OH-stretching modes in hydrogen-bonded materials is often explained by the interplay of OH-stretching modes and combinations and overtones of OH-bending modes. In order to elucidate the both contributions in KDP, we compare the pressure dependence of the OH-bending and stretching modes from ab initio calculation and inelastic neutron scattering (INS) measurements. The ab initio calculation predicts a hardening of OH-bending modes and a softening of OH-stretching modes with pressure. At the same time, INS measurements in the region of OH-stretching modes indicate a hardening of the phonon triplet together with the bending modes. This means that this triplet in INS measurements is mainly due to combinations and overtones of OH-bending modes, while the intensity of OH-stretching modes appears to be relatively low. This conclusion may also apply to other hydrogen-bonded materials.
Materials Science (cond-mat.mtrl-sci)
12 pages, 8 figures
Sliding multiferrocity in van der Waals layered CrI$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Hui-Shi Yu, Xiao-Sheng Ni, Kun Cao
Understanding magnetoelectric coupling in emerging van der Waals multiferroics is crucial for developing atomically thin spintronic devices. Here, we present a comprehensive first-principles investigation of magnetoelectric coupling in orthorhombic CrI$ _2$ . Monte Carlo simulations based on DFT-calculated magnetic exchange interactions suggest a proper-screw helimagnetic ground state with a Néel temperature consistent with experimental observations. A ferroelectric switching pathway driven by interlayer sliding is predicted, featuring a low switching energy barrier and out-of-plane ferroelectric polarization. To quantitatively characterize the magnetoelectric effect in orthorhombic CrI$ _2$ and its microscopic origin, we evaluate the spin-driven polarization using the paramagnetic phase as a reference alongside the magnetoelectric tensor method. The extracted spin-driven polarization aligns along the $ z$ -axis, with its origin dominated by the exchange-striction mechanism. Although in-plane components of the total polarization in the bulk vanish due to global symmetry constraints, each CrI$ _2$ single layer exhibits local electric polarization along the $ x$ direction, arising from the generalized spin-current mechanism, which couples spin chirality to the electric polarization. As a result, we further predict that a proper-screw helimagnetic state may persist in monolayer CrI$ _2$ , with its charity reversable by switching the in-plane electric polarization through applying external electric field, providing another promising candidate for electrical control of two-dimensional multiferroics.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Atomistic modeling of uranium monocarbide with a machine learning interatomic potential
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Lorena Alzate-Vargas, Kashi N. Subedi, Roxanne M. Tutchton, Michael W.D. Cooper, Tammie Gibson, Richard A. Messerly
Uranium monocarbide (UC) is an advanced ceramic fuel candidate due to its superior uranium density and thermal conductivity compared to traditional fuels. To accurately model UC at reactor operating conditions, we developed a machine learning interatomic potential (MLIP) using an active learning procedure to generate a comprehensive training dataset capturing diverse atomic configurations. The resulting MLIP predicts structural, elastic, thermophysical properties, defect formation energies, and diffusion behaviors, aligning well with experimental and theoretical benchmarks. This work significantly advances computational methods to explore UC, enabling efficient large-scale and long-time molecular dynamics simulations essential for reactor fuel qualification.
Materials Science (cond-mat.mtrl-sci)
Using optical tweezers to simultaneously trap, charge and measure the charge of a microparticle in air
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Andrea Stoellner, Isaac C.D. Lenton, Artem G. Volosniev, James Millen, Renjiro Shibuya, Hisao Ishii, Dmytro Rak, Zhanybek Alpichshev, Gregory David, Ruth Signorell, Caroline Muller, Scott Waitukaitis
Optical tweezers are widely used as a highly sensitive tool to measure forces on micron-scale particles. One such application is the measurement of the electric charge of a particle, which can be done with high precision in liquids, air, or vacuum. We experimentally investigate how the trapping laser itself can electrically charge such a particle, in our case a $ \sim 1,\mathrm{\mu m;SiO_2}$ sphere in air. We model the charging mechanism as a two-photon process which reproduces the experimental data with high fidelity.
Soft Condensed Matter (cond-mat.soft), Optics (physics.optics)
Interaction between Rydberg Excitons in Cuprous Oxide Revealed through Second Harmonic Generation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Dirk Semkat, Heinrich Stolz, Peter Grünwald, Andreas Farenbruch, Nikita V. Siverin, Dietmar Fröhlich, Dmitri R. Yakovlev, Manfred Bayer
We report experimental and theoretical investigations of interacting excitons of the yellow series in cuprous oxide (Cu$ _2$ O) with principal quantum numbers up to $ n=7$ by means of second harmonic generation (SHG). Using picosecond pulsed laser excitation up to 10 GW/cm$ ^2$ peak intensity we observe a pronounced change of the spectra with increasing pump laser intensity: an energetic shift to lower absolute energies and a spectral broadening, while the absolute intensity for low powers scales with the square of the pump power, but saturates at higher powers. Concomitant with SHG we determined the density of the excitons excited by the ps pulse by measuring the two-photon absorption directly. This allows to derive quantitative values for the exciton-exciton interaction. Surprisingly, the results disagree both in magnitude and scaling with principal quantum number with those calculated by state-of-the art atomic-like van der Waals interaction theory. As a possible screening by an electron-hole plasma created by three-photon absorption into blue and violet band states could be ruled out, our results point toward fundamental differences between excitons and atoms.
Materials Science (cond-mat.mtrl-sci)
Edge states at the boundary of graphene-like and Lieb lattices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
I. V. Kozlov, Yu. A. Kolesnichenko
Properties of the boundary of two conductors in a quantizing magnetic field are studied: with conventional Dirac charge carriers and so-called pseudospin-1 fermions, which are realized in graphene-like and Lieb lattices respectively. It is shown that edge states arise that relate the properties of conductors to the trivial and nontrivial Berry phase. These edge states lead to the appearance of a characteristic series of root features in the density of states.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
17 pages, 5 figures
Quantum superposition in ultra-high mobility 2D photo-transport
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-24 20:00 EDT
We investigate the striking properties that magnetoresistance of irradiated two-dimensional electron systems presents when their mobility is ultrahigh and temperature is low (T =0.5 K). Such as, an abrupt magnetoresistance collapse at low magnetic field and a resonance peak shift to the second harmonic (2wc = w), wc and w being the cyclotron and radiation frequencies respectively. We appeal to the principle of quantum superposition of coherent states and obtain that Schrodinger cat states (even and odd) are key to explain magnetoresistance at these extreme mobilities. On the one hand, the Schodinger cat states system oscillates with 2wc, thus being responsible of the resonance peak shift. On the other hand, we obtain that Schrodinger cat states-based scattering processes give rise to a destructive effect when the odd states are involved, leading to a magnetoresistance collapse. The Aharonov-Bohm effect plays a central role in the latter, turning even cat states into odd ones. We show that ultra-high mobility two-dimensional electron systems could make a promising bosonic mode-based platform for quantum computing.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Design Principles and Identification of Birefringent Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Gwan Yeong Jung, Guodong Ren, Pravan Omprakash, Jayakanth Ravichandran, Rohan Mishra
Birefringence ($ \Delta n$ ) is the dependence of the refractive index of a material on the polarization of light travelling through it. Birefringent materials are used as polarizers, waveplates, and for novel light-matter coupling. While several birefringent materials exist, only a handful of them show large $ \Delta n$ > 0.3, and are primarily limited to the infrared region. The variation of $ \Delta n$ across diverse materials classes and strategies to achieve highly birefringent materials with transparency covering different regions of the electromagnetic spectrum are missing. We have calculated the $ \Delta n$ of 967 non-cubic, formable crystals having vastly different structures, polyhedral connectivity and chemical compositions. From this set of compounds, we have screened highly birefringent crystals ($ \Delta n$ greater than 0.3) having transparency in different regions of the electromagnetic spectrum. The screened compounds belong to several families such as A3’MN3, AMO2, AN3, and A’N6 (A = Li, Na, K; A’= Ca, Sr, Ba; M = V, Nb, Ta). By analyzing the electronic structures of these compounds, we have distilled rules to enable the design of crystals with large $ \Delta n$ .
Materials Science (cond-mat.mtrl-sci)
27 pages, 5 figures
Giant Spin-to-Charge Conversion by Tailoring Magnetically Proximitized Topological Dirac Semimetal
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Masayuki Ishida, Soichiro Fukuoka, Takahiro Chiba, Yohei Kota, Masaaki Tanaka, Le Duc Anh
While ferromagnet and topological material bilayers are widely studied to obtain efficient spin charge conversion via topological surface states (TSS), the influence of the magnetic proximity effect (MPE) on the TSS evolution and conversion efficiency remains poorly understood. In this study, we experimentally probe and reveal the behavior of spin momentum locked TSS through spin pumping measurements in heterostructures composed of ferromagnetic Fe and the topological Dirac semimetal alpha Sn. As the alpha Sn thickness (tSn) increases from 9 to 35 nm, the Gilbert damping constant of the Fe layer exhibits a pronounced peak at tSn = 25 nm, followed by a decrease at greater thicknesses. Our rigorous theoretical analysis, combining analytical modeling and first principles calculations, attributes this behavior to the TSS disappearance at the Fe and alpha Sn interface and exchange gap opening on the opposite surface, both induced by the long range MPE and its influence on the spin charge conversion efficiency. At tSn = 25 nm, we demonstrate highly efficient spin charge conversion with an inverse Edelstein length of 3.14 nm, the highest value reported at room temperature for ferromagnet and topological material bilayers. These findings underscore the critical role of tuning TSS properties under MPE for advancing topological materials in spintronic applications.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Fragility of Topology under Electronic Correlations in Iron Chalcogenides
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Younsik Kim, Junseo Yoo, Sehoon Kim, Kiyohisa Tanaka, Li Yu, Minjae Kim, Changyoung Kim
The interplay between electronic correlations and topology is a central topic in the study of quantum materials. In this work, we investigate the impact of the orbital-selective Mott phase (OSMP) on the topological properties of FeTe1-xSex (FTS), an iron chalcogenide superconductor known to host both non-trivial Z2 topology and strong electronic correlations. Using angle-resolved photoemission spectroscopy, we track the evolution of topological surface states across various doping levels and temperatures. We identify a topological phase transition between trivial and non-trivial topology as a function of selenium content, with critical behavior observed between x = 0.04 and x = 0.09. Additionally, we find that at elevated temperatures, the coherence of the topological surface state deteriorates due to the emergence of OSMP, despite the topological invariant remaining intact. Our results demonstrate that the non-trivial topology in iron chalcogenide is fragile under strong electronic correlations.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 4 figures
Effect of Group-V Impurities on the Electronic Properties of Germanium Detectors: An Insight from First-Principles Calculations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Sandip Aryal, Enrique R. Batista, Gaoxue Wang
The outstanding properties of high-purity germanium (HPGe) detectors, such as excellent energy resolution, high energy sensitivity, and a low background-to-signal ratio, make them essential and ideal candidates for detecting particle signatures in nuclear processes such as neutrino-less double beta decay. However, the presence of defects and impurities in HPGe crystals can lead to charge trapping, which affects carrier mobility and results in significant energy resolution degradation. In this work, we employ density functional theory with a hybrid functional to study the energetics of possible point defects in Ge. Our findings indicate that n-type group-V impurities, such as phosphorus (P), arsenic (As), and antimony (Sb), form more readily in Ge compared to nitrogen (N), Ge vacancies, and Ge interstitials. Unlike N dopants, which yield deep trap states, P, As, and Sb create shallow traps close to the conduction band edge of Ge. Furthermore, we predict that n-type defects can condense into defect complexes with Ge vacancies. These vacancy-impurity complexes form deep traps in Ge, similar to Ge vacancies, suggesting that both vacancies and vacancy-impurity complexes contribute to charge trapping in these detectors, thereby diminishing their performance.
Materials Science (cond-mat.mtrl-sci)
Machine Learning-Assisted Nano-imaging and Spectroscopy of Phase Coexistence in a Wide-Bandgap Semiconductor
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-24 20:00 EDT
Alyssa Bragg, Fengdeng Liu, Zhifei Yang, Nitzan Hirshberg, Madison Garber, Brayden Lukaskawcez, Liam Thompson, Shane MacDonald, Hayden Binger, Devon Uram, Ashley Bucsek, Bharat Jalan, Alexander McLeod
Wide bandgap semiconductors with high room temperature mobilities are promising materials for high-power electronics. Stannate films provide wide bandgaps and optical transparency, although electron-phonon scattering can limit mobilities. In SrSnO3, epitaxial strain engineering stabilizes a high-mobility tetragonal phase at room temperature, resulting in a threefold increase in electron mobility among doped films. However, strain relaxation in thicker films leads to nanotextured coexistence of tetragonal and orthorhombic phases with unclear implications for optoelectronic performance. The observed nanoscale phase coexistence demands nano-spectroscopy to supply spatial resolution beyond conventional, diffraction-limited microscopy. With nano-infrared spectroscopy, we provide a comprehensive analysis of phase coexistence in SrSnO3 over a broad energy range, distinguishing inhomogeneous phonon and plasma responses arising from structural and electronic domains. We establish Nanoscale Imaging and Spectroscopy with Machine-learning Assistance (NISMA) to map nanotextured phases and quantify their distinct optical responses through a robust quantitative analysis, which can be applied to a broad array of complex oxide materials.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main text: 22 pages, 5 figures. Supplementary Information: 26 pages, 9 figures, 6 tables
Wave propagation in a model artery
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Pierre Chantelot, Alexandre Delory, Claire Prada, Fabrice Lemoult
Fluid filled pipes are ubiquitous in both man-made constructions and living organisms. In the latter, biological pipes, such as arteries, have unique properties as their walls are made of soft, incompressible, highly deformable materials. In this article, we experimentally investigate wave propagation in a model artery: an elastomer strip coupled to a rigid water channel. We measure out-of-plane waves using synthetic Schlieren imaging, and evidence a single dispersive mode which resembles the pulse wave excited by the heartbeat. By imposing an hydrostatic pressure difference, we reveal the strong influence of pre-stress on the dispersion of this wave. Using a model based on the acoustoelastic theory accounting for the material rheology and for the large static deformation of the strip, we demonstrate that the imposed pressure affects wave propagation through an interplay between stretching, orthogonal to the propagation direction, and curvature-induced rigidity. We finally highlight the relevance of our results in the biological setting, by discussing the determination of the arterial wall’s material properties from pulse wave velocity measurements in the presence of pre-stress.
Soft Condensed Matter (cond-mat.soft)
Script and data to reproduce the figures are available in the following GitHub repsoitory, this https URL
The Scaling of Triboelectric Charging Powder Drops for Industrial Applications
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-24 20:00 EDT
Tom F. O’Hara, Ellen Player, Graham Ackroyd, Peter J. Caine, Karen L. Aplin
Triboelectrification of granular materials is a poorly understood phenomenon that alters particle behaviour, impacting industrial processes such as bulk powder handling and conveying. At small scales ($ < 1 g$ ) net charging of powders has been shown to vary linearly with the total particle surface area and hence mass for a given size distribution. This work investigates the scaling relation of granular triboelectric charging, with small, medium ($ < 200 g$ ), and large-scale ($ \sim 400 kg$ ) laboratory testing of industrially relevant materials using a custom powder dropping apparatus and Faraday cup measurements. Our results demonstrate that this scaling is broken before industrially relevant scales are reached. Charge (Q) scaling with mass (m) was fitted with a function of the form $ Q \propto m^b$ and $ b$ exponents ranging from $ 0.68\ \pm\ 0.01$ to $ 0.86\ \pm\ 0.02$ were determined. These exponents lie between those that would be expected from the surface area of the bulk powder ($ b = 2 / 3$ ) and the total particle surface area ($ b = 1$ ). This scaling relation is found to hold across the powders tested and at varying humidities.
Soft Condensed Matter (cond-mat.soft)
Submitted to the Journal of Electrostatics
Deep Generative Learning of Magnetic Frustration in Artificial Spin Ice from Magnetic Force Microscopy Images
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-24 20:00 EDT
Arnab Neogi, Suryakant Mishra, Prasad P Iyer, Tzu-Ming Lu, Ezra Bussmann, Sergei Tretiak, Andrew Crandall Jones, Jian-Xin Zhu
Increasingly large datasets of microscopic images with atomic resolution facilitate the development of machine learning methods to identify and analyze subtle physical phenomena embedded within the images. In this work, microscopic images of honeycomb lattice spin-ice samples serve as datasets from which we automate the calculation of net magnetic moments and directional orientations of spin-ice configurations. In the first stage of our workflow, machine learning models are trained to accurately predict magnetic moments and directions within spin-ice structures. Variational Autoencoders (VAEs), an emergent unsupervised deep learning technique, are employed to generate high-quality synthetic magnetic force microscopy (MFM) images and extract latent feature representations, thereby reducing experimental and segmentation errors. The second stage of proposed methodology enables precise identification and prediction of frustrated vertices and nanomagnetic segments, effectively correlating structural and functional aspects of microscopic images. This facilitates the design of optimized spin-ice configurations with controlled frustration patterns, enabling potential on-demand synthesis.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Scaling Properties of Current Fluctuations in Periodic TASEP
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-24 20:00 EDT
We investigate current fluctuations in the totally asymmetric simple exclusion process (TASEP) on a ring of size $ N$ with $ p$ particles. By deforming the Markov generator with a parameter $ \gamma$ , we analyze the tilted operator governing current statistics using coordinate Bethe ansatz techniques. We derive implicit expressions for the scaled cumulant generating function (SCGF), i.e. the largest eigenvalue, and the spectral gap in terms of Bethe roots, exploiting the geometric structure of Cassini ovals.
In the thermodynamic limit, at fixed particle density, a dynamical phase transition emerges between regimes distinguished by the sign of $ \gamma$ . For positive deformation $ \gamma$ , the SCGF exhibits ballistic scaling, growing linearly with system size $ N$ . For negative $ \gamma$ , the SCGF converges to a universal constant, highlighting distinct fluctuation regimes.
Correspondingly, the spectral gap, controlling relaxation times, shows qualitatively different finite-size scaling: it closes as $ O(N^{-1})$ for $ \gamma>0$ reflecting slow relaxation, but it decreases exponentially for $ \gamma<0$ indicating rapid convergence. These results provide insight into the metastability and relaxation dynamics in driven interacting particle systems.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph)
37 pages, 6 figures
Perturbative renormalization group approach to magic-angle twisted bilayer graphene using topological heavy fermion model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-24 20:00 EDT
Yi Huang, Yang-Zhi Chou, Sankar Das Sarma
We develop a perturbative renormalization group (RG) theory for the topological heavy fermion (THF) model, describing magic-angle twisted bilayer graphene (MATBG) as an emergent Anderson lattice. The realistic parameters place MATBG near an intermediate regime where the Hubbard interaction $ U$ and the hybridization energy $ \gamma$ are comparable, motivating the need for RG analysis. Our approach analytically tracks the flow of single-particle parameters and Coulomb interactions within an energy window below $ 0.1$ eV, providing implications for distinguishing between Kondo-like ($ U\gg \gamma$ ) and projected-limit/Mott-semimetal ($ U\ll \gamma$ ) scenarios at low energies. We show that the RG flows generically lower the ratio $ U/\gamma$ and drive MATBG toward the chiral limit, consistent with the previous numerical study based on the Bistritzer-MacDonald model. The framework presented here also applies to other moiré systems and stoichiometric materials that admit a THF description, including magic-angle twisted trilayer graphene, twisted checkerboard model, and Lieb lattice, among others, providing a foundation for developing low-energy effective theories relevant to a broad class of topological flat-band materials.
Strongly Correlated Electrons (cond-mat.str-el)
22 pages, 15 figures