CMP Journal 2026-03-30
Statistics
arXiv: 63
arXiv
Detecting Complex-Energy Braiding Topology in a Dissipative Atomic Simulator with Transformer-Based Geometric Tomography
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-03-30 20:00 EDT
Yang Yue, Nan Li, Xin Zhang, Chenhao Wang, Zeming Fang, Zhonghua Ji, Liantuan Xiao, Suotang Jia, Yanting Zhao, Liang Bai, Ying Hu
Machine learning (ML) is shaping our exploration of topological matter, whose existence is inherently tied to the geometry of quantum states or energy spectra. In non-Hermitian systems, distinctive spectral geometry can lead to topological braiding of complex-energy bands, yet directly probing this topology-geometry interplay remains challenging. Here, we introduce a Transformer-based ML framework to capture this interplay and experimentally demonstrate it in a dissipative cold-atom simulator. Using a Bose-Einstein condensate, we engineer tunable dissipative two-level systems whose complex eigenenergies form braids. Owing to the density-dependent dissipation, the instantaneous energy braids exhibit topologically distinct structures at short and long times. The Transformer not only accurately predicts topological invariants for diverse energy braids but also, through its self-attention mechanism, autonomously highlights band crossings as the governing underlying geometric feature. Our work paves the way for ML-guided exploration of non-Hermitian topological phases in cold atoms and beyond.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
6 figures,accepted by Nature Communications
A Dipolar Chiral Spin Liquid on the Breathed Kagome Lattice
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-03-30 20:00 EDT
Francisco Machado, Sabrina Chern, Michael P. Zaletel, Norman Y. Yao
Continuous control over lattice geometry, when combined with long-range interactions, offers a powerful yet underexplored tool to generate highly frustrated quantum spin systems. By considering long-range dipolar antiferromagnetic interactions on a breathed Kagome lattice, we demonstrate how these tools can be leveraged to stabilize a chiral spin liquid. We support this prediction with large-scale density-matrix renormalization group calculations and explore the surrounding phase diagram, identifying a route to adiabatic preparation via a locally varying magnetic field. At the same time, we identify the relevant low-energy degrees of freedom in each unit cell, providing a complementary language to study the chiral spin liquid. Finally, we carefully analyze its stability and signatures in finite-sized clusters, proposing direct, experimentally viable measurements of the chiral edge mode in both Rydberg atom and ultracold polar molecule arrays.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el), Atomic Physics (physics.atom-ph), Quantum Physics (quant-ph)
21 + 12 pages, 12 + 8 figures
Imaging the Meissner effect and local superfluid stiffness in a graphene superconductor
New Submission | Superconductivity (cond-mat.supr-con) | 2026-03-30 20:00 EDT
Ruoxi Zhang, Benjamin A. Foutty, Owen Sheekey, Trevor Arp, Siyuan Xu, Tian Xie, Yi Guo, Hari Stoyanov, Sherlock Gu, Aidan Keough, Evgeny Redekop, Canxun Zhang, Takashi Taniguchi, Kenji Watanabe, Martin E. Huber, Chenhao Jin, Erez Berg, Andrea F. Young
We report the observation of the Meissner effect in a rhombohedral graphene superconductor, realized via direct imaging of the static fringe magnetic field. In our few-micron sample, the onset of superconductivity manifests as a diamagnetic response that screens only $ \sim 100$ ppm of the applied magnetic field. Tracking the evolution of the resulting nanotesla-scale fields in real space allows us to observe the entry of superconducting vortices and map the local superfluid stiffness, $ \rho_s$ . Correlating fringe field signals from both Meissner screening and magnetically ordered states, we show that superconductivity onsets in the midst of a continuous quantum phase transition to a canted spin ferromagnet. Within the superconducting state, we find the temperature dependence of $ \rho_s$ to be incompatible with isotropic Bardeen-Cooper-Schrieffer theory and the zero-temperature stiffness $ \rho_s^0$ to be linearly proportional to $ T_c$ , constraining future theoretical models of superconductivity in this system.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Suppressed excitonic effects enable high mobility, high-yield photoconductivity in a two-dimensional polymer crystal with axial pyridine coordination
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Shuai Fu, Ye Yang, Guoquan Gao, Shuangjie Zhao, Miroslav Položij, Tong Zhu, Lei Gao, Thomas Heine, Zhiyong Wang, Mischa Bonn, Xinliang Feng
Two-dimensional polymers (2DPs) and their layer-stacked covalent organic frameworks (2D COFs) offer modular, atomically precise platforms for organic optoelectronics, yet their photoconductive responses remain fundamentally constrained by strong excitonic effects and localized charge transport. Here, we demonstrate that a diyne-linked 2DP crystal with axial pyridine coordination overcomes this limitation, enabling simultaneous efficient free-carrier generation and band-like transport. Introducing pyridine ligands that axially coordinate to Cu-porphyrin nodes transforms weak van der Waals stacking into a pyridine-bridged architecture with pronounced interlayer band dispersion and substantially reduced carrier effective masses. The resulting strong interlayer electronic coupling suppresses the exciton binding energy to well below thermal energy, such that optical excitation directly populates delocalized electronic states. Time-resolved terahertz spectroscopy reveals Drude-type photoconductivity with room-temperature mobilities approaching 500 cm^2 V^-1 s^-1 and a photon-to-free-carrier conversion ratio of ~0.4, yielding a photoconductive response that exceeds that of state-of-the-art organic and many inorganic photoactive materials. These results establish interlayer coordination as a powerful strategy for mitigating excitonic effects and accessing inorganic-like charge transport in organic 2D crystals, opening a pathway toward highly efficient photo-to-electricity conversion in organic-based systems.
Materials Science (cond-mat.mtrl-sci)
Magnetism and magnetoelastic effect in 2D van der Waals multiferroic CuCrP2S6
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-03-30 20:00 EDT
Jiasen Guo (1), Ryan P. Siebenaller (2,3), Michael A. Susner (2), Jiaqiang Yan (4), Zachary Morgan (1), Feng Ye (1)
We report a magnetic and neutron diffraction study on the ground state magnetism and field evolution of single crystal van der Waals multiferroic CuCrP2S6. The ordered moments align along the b axis in the A-type antiferromagnetic configuration with a spin-flop transition along the same direction. Field application along a introduces a smooth transition to a fully-polarized ferromagnetic state via in-plane spin rotation. These findings resolve the ambiguity of the ground state magnetization direction in CuCrP2S6 and uncover its field responses, providing a firm basis for future magnetoelectric study. A magnetoelastic coupling effect connecting the interlayer spacing and the magnetic order was further revealed, highlighting the out-of-plane strain as an effective control knob for tuning magnetism both in this system and in related van der Waals magnets.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
5 figures, 7 pages
Electrical and thermal magnetotransport in altermagnetic CrSb
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Sajal Naduvile Thadathil, Christoph Müller, Reza Firouzmandi, Lorenz Farin, Srikanta Goswami, Antonin Badura, Pascal Manuel, Fabio Orlandi, Philipp Ritzinger, Václav Petříček, Marc Uhlarz, Tommy Kotte, Michal Baj, Marein C. Rahn, Thanassis Speliotis, Markéta Žáčková, Jiří Pospíšil, Bernd Büchner, Jochen Wosnitza, Helena Reichlová, Vilmos Kocsis, Toni Helm, Dominik Kriegner
Chromium antimonide has emerged as a key material platform for studying altermagnetism because of its simple binary composition, high Néel temperature, and semimetallic electronic structure. Here, we investigate electrical and thermal magnetotransport in single-crystalline CrSb using steady-and pulsed-magnetic fields up to 65 T, and complement these measurements with neutron diffraction and magnetization data. We confirm the compensated magnetic structure and observe a large nonsaturating magnetoresistance together with a pronounced nonlinear Hall response at low temperatures. Multicarrier modeling, supported by mobility-spectrum analysis, reveals coexisting electron- and hole-like charge carriers with mobilities up to ~3000 cm2/Vs and shows that the number of transport channels that can be resolved strongly depends on the accessible magnetic-field range. Thermal-transport measurements further reveal a nonlinear thermal Hall response and a thermal conductivity substantially exceeding a simple Wiedemann-Franz law. The broadly similar field and temperature evolution of electrical and thermal transport point to a dominant electronic contribution, while the remaining deviations indicate additional heat-carrying channels.
Materials Science (cond-mat.mtrl-sci)
14 pages, 9 figures
Quantum Thermalization beyond Non-Integrability and Quantum Scars in a Multispecies Bose-Josephson Junction
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-03-30 20:00 EDT
Francesco Di Menna, Sergio Ciuchi, Simone Paganelli
This work investigates the relationship between quantum chaos and thermalization in a three-species Bose-Josephson Junction (BJJ) with mutual interactions, without coupling to any external environment. The analysis is grounded in the Eigenstate Thermalization Hypothesis (ETH), the modern framework for quantum thermalization, in which non-integrability and chaos are historically assumed as prerequisites. After a thorough characterization of quantum chaos in this system, we examine the occurrence of thermal behavior expected when ETH holds. We identify three distinct regimes: chaotic, integrable, and separable. Remarkably, quantum thermalization occurs in both the chaotic and integrable regimes, while it breaks down in the separable limit - supporting that non-integrability is not a necessary condition for thermalization. Furthermore, since the system exhibits collective phenomena in the semiclassical limit, we identify athermal states in the chaotic regime classifiable as quantum scars, which show no signs of thermalization, consistently with a weak form of ETH. These findings contribute to the understanding of ergodicity breaking, emerging statistical behavior, and non-equilibrium dynamics in ultracold many-body quantum systems.
Statistical Mechanics (cond-mat.stat-mech), Quantum Gases (cond-mat.quant-gas)
11 pages (appendixes and bibliography included), 7 figures
Scaling laws of electron and hole spin relaxation in indirect band gap (In,Al)As/AlAs quantum dots
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
T. S. Shamirzaev, D. R. Yakovlev, D. S. Smirnov, V. N. Mantsevich, M. Bayer
We investigate the electron and heavy hole spin dynamics as a function of magnetic field in ensembles of indirect band gap (In,Al)As/AlAs quantum dots (QDs) with type-I band alignment. Employing a comprehensive model that accounts for both the exciton level quartet and the magnetic-field-driven redistribution of excitons between these states via spin relaxation processes, we extract the electron ($ \tau_{se}$ ) and heavy hole ($ \tau_{sh}$ ) spin relaxation times as a function of magnetic field for QDs of varying sizes. Our analysis reveals that both $ \tau_{se}(B)$ and $ \tau_{sh}(B)$ exhibit power-law scaling behavior, yet the scaling exponents for electrons and heavy holes show markedly different evolution with QD size. For QDs with a diameter of about 9 nm, we find $ \tau_{se}(B)\propto B^{-5}$ and $ \tau_{sh}(B)\propto B^{-3}$ . Remarkably, increasing the QD diameter to about 16 nm results in a drastic change of the scaling laws, with both $ \tau_{se}(B)$ and $ \tau_{sh}(B)$ following a $ \propto B^{-9}$ dependence. We discuss the underlying mechanisms responsible for this size-dependent transformation of the magnetic field scaling behavior of carrier spin relaxation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 5 figures, 1 table
Field-controlled interfacial transport and pinning in an active spin system
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-03-30 20:00 EDT
Mintu Karmakar, Matthieu Mangeat, Swarnajit Chatterjee, Heiko Rieger, Raja Paul
Field control provides a practical route to programmable active matter, yet how weak fields modify non-equilibrium coexistence and interfaces remains unclear. To address this, we study a minimal flocking model of active Potts particles coupled to an external field and show that even weak fields can reconfigure phase behavior and interfacial dynamics. For a homogeneous unidirectional field, the flocking phase is reshaped: the coexistence regime between an apolar gas and a polar liquid is replaced by a phase separation between two field-aligned polar phases: a low-density, weakly polarized background and a high-density, strongly polarized band, both moving along the field. When the system forms a dense longitudinal lane oriented transverse to the field, it executes a slow treadmilling motion against the field, driven by the weakly polarized background. If the system is divided into regions with opposite field directions, particles accumulate at the interface, leading to field-induced interface pinning with flocks performing back-and-forth oscillatory motion. In the presence of quenched random field orientations, this pinning favors a disordered state in which global order diminishes with increasing system size, consistent with Imry-Ma arguments, while the quenched disorder smoothens sharp first-order signatures, in line with the Aizenman-Wehr theorem, with activity modifying the scaling. A coarse-grained hydrodynamic theory supports these observations and is consistent with microscopic simulations.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
16 pages, 9 figures
Double-peak Majorana bound states in altermagnet–superconductor heterostructures
New Submission | Superconductivity (cond-mat.supr-con) | 2026-03-30 20:00 EDT
Pankaj Sharma, Narayan Mohanta
We study Majorana bound states in a planar Josephson junction in which the middle channel is a $ d$ -wave altermagnetic metal deposited on a proximitized two-dimensional electron gas. In the topological regime, the near-zero-energy states reveals a characteristic double-peak spatial profile, with the Majorana wavefunction localized near the altermagnet–superconductor interfaces. Using simplified theoretical models, we show that anisotropic hopping intrinsic to altermagnetism naturally generates interface-localized low-energy states, providing the natural explanation for the double-peak structure. In a nanowire geometry with extended normal metallic regions, the same feature persists but the Majorana bound states become more sensitive to the chemical potential compared to the case in planar Josephson junction. In a T-shaped Josephson junction, multiple near-zero-energy states appear, and the Majorana bound state expected at the crossing point is found to be localized near the interfaces, demonstrating that the localization of the Majorana bound states is primarily governed by interface boundaries rather than by the junction geometry. These results show that anisotropic hopping and interface structure play a central role in altermagnet-based topological superconductors and provide a promising route toward a network of controllable Majorana bound states without external magnetic fields.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures
Universal effect of ammonia pressure on synthesis of colloidal metal nitrides in molten salts
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Ruiming Lin, Vikash Khokhar, Ningxin Jiang, Wooje Cho, Zirui Zhou, Di Wang, Justin C. Ondry, Zehan Mi, James Cassidy, Alex M. Hinkle, John S. Anderson, Richard D. Schaller, De-en Jiang, Dmitri V. Talapin
Metal nitrides represent a large class of materials with extensive applications in optoelectronics, energy, and healthcare technologies. For example, GaN and related nitride semiconductors are key materials for solid-state lighting and high-power electronics, TiN and other early transition metal nitrides (TMNs) are widely used in wear-resistant alloys, tool coatings, catalysts and medical implants. Strong metal-nitrogen bonds grant nitrides structural rigidity as well as chemical and thermal stability. However, the covalency of metal-nitrogen bonds necessitates high temperatures to synthesize crystalline metal nitrides. Common synthetic routes include high-temperature solid-state nitridation, crystal growth in supercritical ammonia, molecular-beam epitaxy (MBE), reactive sputtering, and chemical vapor deposition (CVD). The solution synthesis of colloidal nitride nanocrystals (NCs) is rare and particularly challenging because commonly used solvents and surfactants decompose at temperatures far below those required for crystallization of most metal nitrides. Here we report a general approach to solution synthesis of colloidal metal nitride NCs by reacting metal halides and ammonia dissolved in molten inorganic salts at elevated pressures. Successful syntheses of colloidal TiN, VN, GaN, NbN, Mo2N, Ta3N5, W2N, as well as ternary Ti1-xVxN NCs, are demonstrated. These NCs expand the scope of solution-processable technologically important materials.
Materials Science (cond-mat.mtrl-sci)
Decoupling dislocation multiplication and velocity effects in metals at extreme strain rates
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Daniyar Syrlybayev, Lavanya Raman, Niraj Pramod Atale, Bhanugoban Maheswaran, Siddhartha Pathak, Curt A. Bronkhorst, Ramathasan Thevamaran
The dynamic behavior of metals is governed by collective dislocation motion and interactions that strongly depend on the applied strain rate. Metals exhibit weak strain rate sensitivity (SRS) below a certain threshold, followed by a distinct SRS upturn at higher loading rates. While this upturn is typically attributed to increased glide resistance at high dislocation velocity due to mechanisms such as phonon drag, the role of strain-rate-dependent dislocation multiplication and microstructural evolution under these extreme conditions remains elusive. Here, we decouple these two strengthening effects and show that, while dislocation velocity primarily governs the SRS upturn, the hardening due to microstructure evolution depends strongly on the initial dislocation density. Our investigation of hardness evolution across ten decades of strain rates in a quenched and tempered martensitic low-carbon steel (LCS) using laser-induced projectile impact tests (LIPIT) and nanoindentation reveals SRS upturn around 10^7 1/s. By performing in situ re-indentation of the formed craters, we probe the contribution of dislocations generated during initial deformation at different strain rates. We show that while dislocation multiplication plays a negligible role in fine-grained LCS with high dislocation density, a pronounced dislocation multiplication contributes to the hardness increase in pure iron with lower initial dislocation density. Our results show that, depending on the initial microstructure of metals, dislocation multiplication significantly governs high-strain-rate plasticity, in addition to dislocation velocity effects.
Materials Science (cond-mat.mtrl-sci)
Supplementary Information Included
Benchmarking the accuracy of superconducting pair-pair correlations within Constrained Path Quantum Monte Carlo
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-03-30 20:00 EDT
Jodie Roberts, Beau A. Thompson, R. Torsten Clay
Ground state properties of the Hubbard model are of fundamental importance to understand the mechanism of unconventional superconductivity in the high-T_c cuprates and other materials. One of the most powerful numerical methods for strongly interacting models is quantum Monte Carlo, which however faces a fundamental limitation, the Fermion sign problem. The sign problem can be mitigated using approximate methods such as Constrained Path Monte Carlo, but additional approximations must be made in order to measure different observables, particularly for operators that do not commute with the Hamiltonian. We examine critically the most commonly used approximation, back propagation, as well as a recently proposed constraint release measurement technique. In comparisons with a variety of systems that can be solved numerically exactly by other methods, we find that back propagation tends to underestimate superconducting pair-pair correlations. The constraint release technique can provide accurate results, with the disadvantages that it much more computationally expensive and reintroduces the sign problem.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
8 pages, 5 figures
Compositional Complexity-Induced Ultralow Friction in Medium-Entropy MXenes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Jiaoli Li, Yuwei Zhang, Congjie Wei, Yanxiao Li, Shuo He, Risheng Wang, Brian Wyatt, Reza Namakian, Babak Anasori, Kelvin Xie, Tobin Filleter, Ali Erdemir, Wei Gao, Chenglin Wu
Two-dimensional MXenes are promising solid lubricants, but the roles of compositional complexity and surface chemistry in governing interfacial friction remain unclear. Here, we systematically investigate the adhesion and friction behaviors of medium-entropy (ME) MXenes, TiVNbMoC3 and TiVCrMoC3, and compare them with conventional titanium carbide MXenes, Ti2C and Ti3C2, using a SiO2 colloidal atomic force microscopy probe. Thermal annealing at 200 C converts OH surface terminations to O terminations, leading to pronounced reductions in adhesion energy and friction force across all MXenes studied. ME MXenes exhibit larger adhesion reductions because of their higher initial OH contents and more extensive OH-to-O conversion. In addition, their intrinsically higher out-of-plane bending stiffness suppresses energy dissipation during sliding, enabling ultralow friction. Notably, superlubricity is achieved in ME MXenes, with annealed TiVCrMoC3 exhibiting a coefficient of friction as low as 0.0022, outperforming graphene, MoSe2, and other MXenes evaluated using the same experimental approach. These findings identify compositional complexity as a powerful strategy for engineering MXenes with exceptional tribological performance and establish ME MXenes as a new class of solid lubricants.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Cluster glass behavior and magnetocaloric effect in the hexagonal polymorph of disordered Ce$_2$PdGe$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Leszek S. Litzbarski, Kamil Balcarek, Anna Bajorek, Tomasz Klimczuk, Michał J. Winiarski, Karol Synoradzki
In this work, we study the hexagonal variant of the $ \text{Ce}_2\text{PdGe}_3$ system that crystallizes in the $ \text{AlB}_2$ -type structure (space group $ P6/mmm$ , $ hP3$ ) and exhibits cluster spin glass type behavior. The physical properties were studied by magnetization, heat capacity and electric resistivity, which showed that $ \text{AlB}_2$ -type $ \text{Ce}_2\text{PdGe}_3$ ($ h\text{-Ce}2\text{PdGe}3$ ) can be classified as a cluster glass material with the freezing temperature $ T_f = 3.44 \text{ K}$ in contrast to the behavior of the previously described tetragonal variant, which shows a double antiferromagnetic transition at $ T{N1} = 11 \text{ K}$ and $ T{N2} = 2.3 \text{ K}$ . The X-ray photoelectron spectroscopy measurements reveal that the $ \text{Ce } 4f$ states are well localized. In addition, we examine the magnetocaloric effect in this compound. The maximum values of magnetocaloric parameters appear in the vicinity of $ 7\text{–}9 \text{ K}$ . For a magnetic field change of $ 50 \text{ kOe}$ , the value of the change in magnetic entropy is $ 2.6(1) \text{ J kg}^{-1} \text{ K}^{-1}$ and the adiabatic temperature change is $ \sim 8 \text{ K}$ .
Materials Science (cond-mat.mtrl-sci)
Physica Status Solidi B: Basic Solid State Physics 262 (2025) 6
Room-temperature antiferromagnetic resonance in NaMnAs
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Jan Dzian, Stáňa Tázlarů, Ivan Mohelský, Florian Le Mardelé, Filip Chudoba, Jiří Volný, Jan Wyzula, Amit Pawbake, Simone Ritarossi, Riccardo Mazzarello, Philipp Ritzinger, Jakub Železný, Karel Výborný, Klára Uhlířová, Benoît Grémaud, Andrés Saúl, Clément Faugeras, Martin Veis, Milan Orlita
We report on antiferromagnetic resonance experiments in bulk tetragonal NaMnAs – a room-temperature antiferromagnetic semiconductor. Our results corroborate previous ab initio studies, which propose that NaMnAs is an easy-axis antiferromagnet with the Néel vector oriented along the tetragonal axis. At $ B = 0 $ , we find a single antiferromagnetic resonance line at 7 meV and associate it with a doubly degenerate ($ k = 0 $ ) magnon mode. Its energy softens considerably with increasing $ T $ , but remains clearly visible in the data up to room temperature. From the experimental data, we estimate the single-ion anisotropy of the Mn ions in NaMnAs to be $ D \approx 0.2 $ meV, a value that is relatively large compared to other manganese-based antiferromagnets.
Materials Science (cond-mat.mtrl-sci)
9 pages, 9 figures
Exciton dynamics and high-temperature excitonic superfluidity in S-doped graphyne
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Enesio Marinho Jr., Alexandre C. Dias, Luiz A. Ribeiro Jr., Maurizia Palummo, Cesar E. P. Villegas
S-doped graphyne (S-GY) is a recently synthesized two-dimensional graphyne-based carbon allotrope that provides a promising platform for exciton engineering and coherent many-body phases. Here, we investigate the quasiparticle electronic structure, optical response, and exciton dynamics of monolayer S-GY using the G$ _0$ W$ _0$ approximation and the Bethe–Salpeter equation (BSE). Quasiparticle corrections increase the fundamental band gap from $ 0.88,\text{eV}$ (PBE) to $ 1.95,\text{eV}$ , while slightly reducing the carrier effective masses. The BSE optical response reveals strongly bound excitons, with the lowest bright exciton exhibiting a binding energy of $ 0.72,\text{eV}$ , as well as a nearly degenerate dark exciton within the thermal energy scale. Analysis of exciton wavefunctions in reciprocal space confirms a hydrogenic Rydberg series with well-defined angular-momentum character, and radiative lifetimes in the nanosecond range at room temperature, comparable to those in transition-metal dichalcogenide monolayers. Finally, we construct the excitonic phase diagram and estimate a crossover density of $ \sim6 \times10^{12}~\text{cm}^{-2}$ , below which the exciton gas behaves as a dilute Bose system, and the Berezinskii–Kosterlitz–Thouless (BKT) superfluid phase becomes accessible. We estimate a maximum BKT transition temperature of $ \sim 143,\text{K}$ in the freestanding limit for the 1s exciton, indicating that monolayer S-GY may provide favorable conditions for high-temperature excitonic superfluidity in graphyne-based materials.
Materials Science (cond-mat.mtrl-sci)
Extreme (Rogue) Waves: From Theory to Experiments in Ultracold Gases and Beyond
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-03-30 20:00 EDT
A. Chabchoub, P. Engels, P. G. Kevrekidis, S. I. Mistakidis, G. C. Katsimiga, M. E. Mossman, S. Mossman
In this Chapter, we review key theoretical and experimental advances in the study of extreme nonlinear wave events, called rogue waves (RWs), in both single-component attractively interacting and two-component repulsive mixtures of ultracold quantum gases. Starting from the exact rational solutions of the integrable focusing nonlinear Schroedinger model, the hierarchy of RW solutions is exemplified. These range from the Peregrine soliton (PS) and, related to it, the destabilization into a multi-peak cascade of PSs dubbed “Christmas-tree”, to the Akhmediev breather, and Kuznetsov-Ma soliton as well as higher-order RWs. Emphasis is placed on their controllable dynamical emergence and characteristics in non-integrable quantum many-body systems described by Gross-Pitaevskii models and extensions thereof through different protocols such as modulational instability, gradient catastrophe, and dam-break flows. We further discuss how immiscible particle-imbalanced repulsive mixtures can be cast into effective attractive single-component environments capable of hosting RWs. Next, state-of-the-art experimental techniques are summarized within the ultracold realm that can be utilized to realize solitary waves, modulational instability, dispersive shock waves and RWs including the very recent first experimental observation of the PS, enabled through engineered effective focusing interactions and precise dynamical triggering. Observations of these extreme events in water waves, nonlinear optics and beyond are also outlined, highlighting their broader relevance and potential of emergence in disparate physical settings. Our exposition aims at showcasing ultracold atomic gases as versatile platforms for controllably generating and probing extreme nonlinear events, among others, in the quantum realm across integrable and non-integrable settings.
Quantum Gases (cond-mat.quant-gas), Pattern Formation and Solitons (nlin.PS), Quantum Physics (quant-ph)
25 pages, 13 figures
Modeling key characteristics of high-efficiency gallium arsenide solar cells
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
A.V. Sachenko, V.P. Kostylyov, I.O. Sokolovskyi, A.I. Shkrebtii
The paper proposes a theoretical approach to modeling the key characteristics of highly efficient gallium arsenide-based solar cells (SCs), using a one-dimensional SC model. The following recombination mechanisms are considered in the modeling: radiative recombination, interband Auger recombination, Shockley-Reed-Hall (SRH) recombination, surface recombination, recombination in the space charge region (SCR), and recombination along the perimeter of the structure. A simple empirical formula is proposed to describe the recombination along the perimeter of the SC structure. The GaAs band-gap narrowing effect is also taken into consideration. The main results are obtained under the assumption that the times of Shockley-Reed-Hall recombination and recombination in the SCR are the same. The effect of photon recycling (re-emission and re-absorption) is taken into account in a model similar to the one we used previously to simulate key characteristics of high-efficiency single-crystal silicon SCs. The model additionally uses absorption analysis at different doping levels of gallium arsenide. A good agreement was achieved between the experimental and theoretical dependencies. The results obtained in this work can be used to optimize the characteristics of highly efficient SCs based on direct-band semiconductors, particularly gallium arsenide (GaAs). Keywords: solar cell, high efficiency, modeling, gallium arsenide, recombination mechanisms, external quantum efficiency, parameter optimization.
Materials Science (cond-mat.mtrl-sci)
Assessing the classicality of photon echo from excitons in lead halide perovskite nanocrystals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
George Alkhalil, Hendrik Rose, Artur V. Trifonov, Polina R. Sharapova, Jan Sperling, Dmitri R. Yakovlev, Elena V. Kolobkova, Maria S. Kuznetsova, Marc Aßmann, Manfred Bayer, Torsten Meier, Ilya A. Akimov
Photon echo (PE) spectroscopy is a powerful technique for probing decoherence mechanisms and charge carrier dynamics in semiconductor systems. Beyond traditional coherence measurements, characterizing the photon statistics of the echo signal is important for assessing its potential in quantum information applications and understanding the underlying quantum mechanical processes. Here, we study the photon statistics of PE signals generated by excitons in ensembles of lead halide perovskite CsPbI$ _3$ nanocrystals at cryogenic temperature of 2 K using continuous-variable quantum state optical tomography based on homodyne detection. Pronounced Rabi oscillations of PE amplitude allow us to evaluate the statistics for various pulse areas in the excitation sequence. The damping of the oscillations with increasing pulse area is attributed to spatial excitation inhomogeneity and excitation-induced dephasing. Despite the large ensemble of optically addressed excitons, the efficiency of generated PE signals is low which is attributed to complex energy structure of excitons and non-radiative recombination channels in CsPbI$ _3$ nanocrystals. We analyze the statistical characteristics of PE via the second-order correlation function $ g^{(2)}(0)$ and the characteristic function for different combinations of the areas of the excitation pulses. Our results show that $ g^{(2)}(0) = 1$ , and the characteristic function of the PE signal corresponds to classical behavior. Despite the relatively low efficiency, the photon echo exhibits a high degree of coherence and minimal classical noise, consistent with Poissonian statistics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 10 figures
Floquet-driven thermal transport in topological Haldane lattice systems
New Submission | Other Condensed Matter (cond-mat.other) | 2026-03-30 20:00 EDT
Imtiaz Khan, Muzamil Shah, Ambreen Uzair, Reza Asgari, Gao Xianlong
In this paper, we employ a modified Haldane lattice model to investigate the light-driven, spin- and valley-dependent anomalous Nernst effect in two-dimensional hexagonal topological systems. We demonstrate that two-dimensional buckled materials exhibit a hierarchy of electrically and optically tunable topological phases when subjected to off-resonant circularly polarized light in the presence of intrinsic spin-orbit coupling and a staggered sublattice potential. Within a Berry-curvature-driven transport framework, we systematically analyze charge-, spin-, and valley-resolved anomalous Nernst responses and identify their correspondence with distinct topological regimes. A finite charge Nernst conductivity arises under optical driving combined with spin-orbit coupling, whereas the generation of a pure valley Nernst current requires the simultaneous presence of sublattice asymmetry and off-resonant light. Substrate-induced inversion asymmetry further enables thermally driven valley currents with tunable magnitude and sign. We find that single-spin and single-valley Nernst responses occur in selected insulating and metallic phases, while the valley Nernst signal is suppressed in spin-polarized and anomalous quantum Hall phases. Extending our analysis to monolayer MoS$ _2$ , we show that strong spin-orbit coupling and broken inversion symmetry allow fully spin- and valley-polarized Nernst currents over a broad energy window. The temperature dependence of the Nernst response exhibits characteristic signatures of topological phase transitions, establishing the anomalous Nernst effect as a sensitive probe of field-engineered band topology in two-dimensional Dirac materials.
Other Condensed Matter (cond-mat.other)
14 pages, 9 figures
Computational Insights into PEMFC Durability: Degradation Mechanisms, Interfacial Chemistry, and the Emerging Role of Machine Learning Potentials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Jack Jon Hinsch, Kazushi Fujimoto
Proton exchange membrane fuel cells (PEMFCs) are a promising clean energy technology, offering high efficiency and near-zero operational emissions for stationery and automotive applications. However, their widespread adoption remains limited by insufficient durability, driven by the degradation of the catalyst layer and proton exchange membrane under realistic operating conditions. While the macroscopic consequences of degradation are well established experimentally, the atomistic and molecular mechanisms that initiate and propagate failure remain incompletely understood. This review synthesizes recent advances in computational modelling, spanning density functional theory, molecular dynamics, and emerging machine learning potentials, to examine how chemical, mechanical, electrochemical, and contamination driven degradation mechanisms operate across multiple length and time scales. Key topics include radical-induced membrane degradation, platinum dissolution and carbon support corrosion, mechanical fatigue under electrical and hygrothermal cycling, and the impact of ionic and gaseous contaminants. A central finding is that these degradation pathways are not independent, but form strongly coupled feedback loops that no existing computational framework has been designed to capture this coupling simultaneously. Future directions are proposed, with emphasis on multiscale modelling frameworks and the application of machine learning interatomic potentials to the electrified interface.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
A literature review to be submitted to advance chemical reviews. This is the version before submission
Spontaneous oscillations and geometric cutoff in confined bacterial swarms
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-03-30 20:00 EDT
Self-organized dynamic patterns in dense active matter are striking manifestations of non-equilibrium physics. A prominent example is the macroscopic elliptical motion observed in quasi-2D bacterial suspensions, which has lacked a physical explanation. Here, we examine a minimal linear response framework coupling bacterial swimming dynamics with fluid flow, treating long-range hydrodynamic interactions as a macroscopic communication channel. We demonstrate that microscopic swim motion, via Jeffery coupling, manifests as a ``phase-leading’’ response to local shear flows. System-wide sustained oscillations, on the other hand, require both a critical bacterial density and strict geometric confinement. By analytically predicting the onset cell density and maximum film thickness, our model achieves excellent quantitative agreement with experiments, establishing a unified physical framework for self-organized periodic motion of elongated body in active fluids.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Fluid Dynamics (physics.flu-dyn)
5 pages, 3 figures
ZEBRA-Prop: A Zero-Shot Embedding-Based Rapid and Accessible Regression Model for Materials Properties
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Ryoma Yamamoto, Akira Takahashi, Kei Terayama, Yu Kumagai, Fumiyasu Oba
Large language models (LLMs) exhibit substantial potential across diverse scientific disciplines, including materials science. A property prediction framework, ZEBRA-Prop (Zero-Shot Embedding-Based Rapid and Accessible Regression Model for Materials Properties), is presented here as an extension of LLM-Prop. In contrast to LLM-Prop, which requires task-specific fine-tuning of the LLM, ZEBRA-Prop eliminates fine-tuning, thereby reducing computational cost and enabling rapid model training. The framework employs MatTPUSciBERT, an LLM specialized for materials science, to enhance predictive capability. Multiple textual embeddings are incorporated through a learnable weighting mechanism, which alleviates the context-length constraints inherent in LLM-Prop and facilitates effective integration of diverse textual representations. Evaluation is conducted using two datasets: the TextEdge dataset (approximately 140,000 entries) and an in-house dataset (approximately 2,000 entries) derived from the Materials Project database, with physical properties obtained from first-principles calculations. The predictive performance of ZEBRA-Prop is close to that of LLM-Prop, while the training time is reduced by approximately 95%. The performance improvements are attributable to three principal factors: domain-specific LLM utilization, diversified textual descriptions, and systematic text preprocessing. ZEBRA-Prop constitutes a scalable and computationally efficient framework for materials property prediction and supports accelerated materials discovery, particularly under limited computational resources.
Materials Science (cond-mat.mtrl-sci)
Composition-dependent bulk properties in intercalated transition metal dichalcogenides $Co_{1/3(1\pmδ)}NbS_{2}$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Woonghee Cho, Kiwan Nam, Yeochan An, You Young Kim, Myung-Hwa Jung, Kee Hoon Kim, Je-Geun Park
We report a systematic study of the composition-dependent bulk properties in $ Co_{1/3(1\pm\delta)}NbS_{2}$ single crystals across a series of precisely controlled cobalt compositions with -4%<$ \delta$ <8%. By tuning the cobalt stoichiometry, we find that the topological Hall effect is critically sensitive to the intercalant cobalt composition and is completely suppressed when the cobalt composition exceeds $ \delta$ =+4%. We observe that the longitudinal conductivity is also strongly influenced by the cobalt composition, reaching its maximum value just before the disappearance of the topological Hall effect. Furthermore, heat capacity measurements reveal distinct Sommerfeld coefficients ($ \gamma$ ) across different compositions, which exhibit a clear linear scaling with the inverse of the ordinary Hall coefficient ($ R_H^{-1}$ ). These results demonstrate that composition tuning in $ Co_{1/3(1\pm\delta)}NbS_{2}$ systematically modifies the low-energy electronic degree of freedom, moving beyond a simple dilute impurity picture. Finally, we use the microscopic spin Hamiltonian to explain the stability of experimentally observed M-point modulation vector and the corresponding triple-Q magnetic order. Our findings highlight that the topological properties of this system are highly tunable through precise control of the intercalant concentration, offering a new perspective on the competition between electronic and magnetic orders in intercalated transition-metal dichalcogenides.
Materials Science (cond-mat.mtrl-sci)
16 pages, 8 figures
Comparing the orbital angular momentum and magnetic moment of magnon in the Kagome antiferromagnet with negative spin chirality
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Youngjae Jeon, Jongjun M. Lee, Hyun-Woo Lee
The orbital dynamics of magnons have recently drawn interest due to their potential roles in thermal and orbital transport phenomena in magnetic insulators. In this study, we investigate the orbital magnetic moment (OMM) and orbital angular momentum (OAM) of magnons in a Kagome antiferromagnet with negative vector chirality, focusing on the distinction between thermodynamic and wave-packet-based definitions. We compute the Berry curvature, the OMM, and the OAM in momentum space under an external magnetic field. Our results reveal a quantitative difference between the OMM and OAM, yet their associated Nernst coefficients exhibit similar temperature and field dependence in transport. Our results provide a quantitative comparison between the thermodynamic and wave-packet formulations of magnon orbital dynamics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Evolution of Linear Viscoelasticity across the Critical Gelation Transition
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-03-30 20:00 EDT
In this work, we develop a rigorous theoretical framework for the evolution of linear viscoelastic properties across the sol-gel transition. More specifically, we derive general admissible expressions for the relaxation modulus and dynamic moduli as the critical gel state is approached from the pre-gel or the post-gel side. These expressions possess a generalized multi-mode series representation and recover the critical gel power law spectrum in the limit of vanishing distance from the gel point. We validate these expressions against the experimental data for various polymeric and colloidal systems. A central finding of the present work is the requirement of continuity of the dynamic moduli and their derivatives at the critical gel point, which imposes a profound physical constraint, necessitating the relaxation dynamics on both sides of the transition to be symmetric. This, in turn, leads to the hyper-scaling relation, which is a theoretical requirement rather than an empirical proposal. We further show that the critical relaxation exponent (n) always remains above the relaxation scaling exponent (\kappa), establishing a previously unrecognized lower bound on n. We also analytically estimate, for the first time, the parameter C that characterizes the relative evolution of the storage modulus with respect to the loss modulus as the critical state is approached. These results reveal that the symmetry, scaling, and hyperscaling properties of the sol-gel transition are all consequences of a single unifying physical requirement originating from the continuity of the linear viscoelastic properties at the critical gel point.
Soft Condensed Matter (cond-mat.soft), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
45 pages and 5 figures
Crossover Scaling of Binder Cumulant and its application in Non-reciprocal Sandpiles
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-03-30 20:00 EDT
In this letter, we unveil a robust, pre-asymptotic scaling regime for the Binder cumulant $ U_L$ , a central finite-size scaling tool, demonstrating $ U_L\sim N^{-1} |t|^{-d\nu}$ (disordered phase) and $ \frac{2}{3}-U_L\sim N^{-1} |t|^{-d\nu}$ (ordered phase), with $ t$ being the reduced control parameter, and $ N$ , $ d$ , $ \nu$ represent the total number of sites, the dimensionality, and correlation length exponent, respectively. Leveraging this result, we resolve a fundamental question on the stability of universality classes under the breaking of microscopic reciprocity. For the conserved Manna sandpile, we show that reciprocal biases preserve its universality class, merely shifting the critical point. In striking contrast, any non-reciprocal interaction acts as a relevant perturbation, decisively driving the system’s critical exponents to flow from their non-mean-field values towards the mean-field related ones. This flow establishes non-reciprocity as a generic mechanism inducing mean-field criticality in conserved, non-equilibrium systems.
Statistical Mechanics (cond-mat.stat-mech)
6+7pages, 4+7figures
Phase Coherence of Strongly Interacting Bosons in One-Dimensional Optical Lattices
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-03-30 20:00 EDT
R. Vatré, G. Morettini, J. Beugnon, R. Lopes, L. Mazza, F. Gerbier
Ultracold Bose gases in one-dimensional optical lattices constitute an important benchmark problem in the study of strongly interacting many-body quantum phases. Here we present a combined experimental and theoretical study of their phase-coherence properties over a wide range of lattice depths. Experimentally, we extract the single-particle correlation function directly from the measured momentum distribution. Theoretically, we perform tensor-network simulations of the Bose-Hubbard model that incorporate all relevant experimental parameters. For deep lattices well within the Mott insulator regime, the experimental results are in good agreement with the expected zero-temperature behavior, with only small temperature-dependent corrections. As the lattice depth is reduced, finite-temperature effects become increasingly important. We find that the experimental data are quantitatively described by an effective temperature extracted from the tensor-network simulations, and that this effective temperature decreases markedly with increasing lattice depth. Rather than indicating actual cooling, we interpret this behavior as evidence of inhibition of thermalization caused by the formation of Mott domains that suppress heat transport. Counterintuitively, the inhibition of thermalization favors the preparation of an effectively low-entropy quantum gas in the trap center for large lattice depths.
Quantum Gases (cond-mat.quant-gas)
Liquid-state structural asymmetry governs species-selective crystallization in multicomponent systems
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-03-30 20:00 EDT
Rikuya Ishikawa, Kyohei Takae, Daisuke Takegami, Yoshikazu Mizuguchi, Rei Kurita
Multicomponent crystals are often assumed to form nearly random solid solutions when thermodynamically stable. However, crystal growth proceeds from structurally heterogeneous liquids, raising the possibility that the liquid state may influence which species are incorporated into the growing crystal. Here we demonstrate that liquid-state structural asymmetry can induce species-selective crystallization in multicomponent systems. Using molecular dynamics simulations of a multivalent rocksalt-type model (AgPbBiTe$ _3$ ), we find that cations with higher valence readily form locally crystal-compatible coordination environments in the liquid and are efficiently incorporated into the growing lattice, whereas lower-valence cations exhibit more disordered liquid coordination and attach less efficiently at the crystal-liquid interface. This asymmetry leads to species-selective incorporation and slower crystal growth. Depth-resolved photoelectron spectroscopy measurements on AgPbBiTe$ _3$ further reveal enhanced Ag concentration near grain-boundary and surface regions, consistent with the selective incorporation predicted by the simulations. These results demonstrate that structural compatibility between liquid-state structure and the target crystal motif governs selective incorporation during crystallization, providing a general kinetic mechanism by which compositional heterogeneity can emerge during growth of multicomponent crystals.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
Towards twisted, topological, and quantum graphene plasmonics
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
A. Octávio Soares, Nuno M. R. Peres
In this article, we analyze the quantum and topological properties of graphene-based plasmonic systems. We consider the following plasmonic materials: single-layer graphene, twisted bilayer graphene, and other graphene stackings, as well as the following architectures: graphene-based gratings, grids, chains of graphene disks, and the kagomé lattice.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 1 Figure, Perspective article
Multifractal Analysis of the Non-Hermitian Skin Effect: From Many-Body to Tree Models
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-03-30 20:00 EDT
The non-Hermitian skin effect is an anomalous localization phenomenon induced by nonreciprocal dissipation and has attracted considerable attention in recent years both theoretically and experimentally. In this article, we review the multifractal aspects of the non-Hermitian skin effect. In particular, we discuss how the many-body skin effect exhibits multifractality in many-body Hilbert space, unlike the trivial Hilbert-space occupation of the single-particle skin effect on crystalline lattices. We further highlight that the many-body skin effect can coexist with random-matrix spectral statistics, in contrast to the multifractality associated with many-body localization, which typically accompanies the absence of ergodicity. We also introduce a solvable model on a Cayley tree as an effective description of the many-body Hilbert space, in which the multifractal dimensions can be obtained analytically. This review provides a unified perspective on multifractal structures in the non-Hermitian skin effect across single-particle, many-body, and tree models, and clarifies their distinctive relation to ergodicity in open quantum systems.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
19 pages, 6 figures. Submitted as an invited article to Quantum Science and Technology Focus Collection on “Non-Hermitian Quantum Many-Body Physics”
A Sc2C2@C88 cluster based ultra-compact multi-level probabilistic bit for matrix multiplication
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Haoran Qi, Guohao Xi, Yuan-Biao Zhou, Xinrong Liu, Yifu Mao, Jian Yang, Jun Chen, Kuojuei Hu, Weiwei Gao, Shuai Zhang, Xiaoqin Gao, Jianguo Wan, Da-Wei Zhou, Junhong An, Xuefeng Wang, De-Chuan Zhan, Minhao Zhang, Cong Wang, Wei ji, Yuan-Zhi Tan, Su-Yuan Xie, Fengqi Song
Information units are progressively approaching the fundamental physical limits of the integration density, including in terms of extremely small sizes, multistates and probabilistic traversal. However, simultaneously encompassing all of these characteristics in a unit remains elusive. Here, via real-time in situ electrical monitoring, we clearly observed stochastic alterations of multiple conductance states in Sc2C2@C88. The true random bit sequence generated exhibited an autocorrelation function whose confidence interval fell within \pm 0.02, demonstrating high-quality randomness. The alterations of multiple conductance states are controllable, that is, whose probability distributions could traverse from 0 to 1, enabling us to factorize 551 into its prime factors. Furthermore, we proposed a matrix-chain multiplication scheme and experimentally verified the multiplication of two 4 \times 4 state-transition matrices with a small maximum error < 0.05. Combined with theoretical calculations, the stochastic but controllable multistates are probably attributed to the rich energy landscape, which could be stepwise changed by the electric field. Our findings reveal extremely small multi-level probabilistic bit for matrix multiplication, which pave the way for ultracompact intelligent electronic devices.
Materials Science (cond-mat.mtrl-sci)
The Unreconstructed α-Al${2}$O${3}$(0001) Surface is Inhomogeneous and Rough
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Johanna I. Hütner-Reisch, Andrea Conti, David Kugler, Florian Mittendorfer, Michael Schmid, Ulrike Diebold, Jan Balajka
Alumina (Al$ _{2}$ O$ _{3}$ ) is a key material for thin-film growth and heterogeneous catalysis, where the atomic surface structure critically impacts performance. Using noncontact atomic force microscopy (nc-AFM) combined with density functional theory (DFT) calculations, we challenge the common assumption that the unreconstructed $ \alpha$ -Al$ _{2}$ O$ _{3}$ (0001) surface is atomically flat and uniformly Al-terminated. This widely accepted bulk termination satisfies polarity compensation requirements but results in highly undercoordinated surface Al cations at the surface. Despite substantial inward relaxation of these Al cations, we find that the (1 $ {\times}$ 1) surface remains inherently metastable, relative to the thermodynamically stable $ (\sqrt{31} \times \sqrt{31})R\pm9°$ surface reconstruction that forms at high temperatures above 1000 °C. Nc-AFM imaging of the unreconstructed surface reveals a rough and disordered morphology, with only nanometer-scale regions exhibiting the ordered Al-terminated (1 $ \times$ 1) structure. Our results show that the unreconstructed Al$ _{2}$ O$ _{3}$ (0001) surface is intrinsically inhomogeneous, reconciling conflicting experimental observations and challenging the validity of commonly used atomistic models.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Photoinduced strain and polarization switching in barium titanate in the far-infrared spectral range
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Maarten Kwaaitaal, Daniel Lourens, Carl S. Davies, Andrei Kirilyuk
Short mid-infrared laser pulses efficiently facilitate ultrafast manipulation of ferroic order parameters, including full reversal of magnetization or ferroelectric polarization, with the invoked mechanisms relating to the properties of polar phonons in ionic crystals. Much less is known, however, about the behaviour of such order parameters in response to an excitation in the far-infrared range, where phonons are more collective and less polar. Here we investigate transient crystallographic strains and polarization switching in ferroelectric barium titanate (BaTiO3) driven by an excitation in the frequency range of 5-8 THz, or wavelengths of 35-60 um. We find that switching persists in a large part of this range, but is governed primarily by optical absorption rather than by the longitudinal optical phonons or epsilon-near-zero conditions that dominate in the mid-infrared regime.
Materials Science (cond-mat.mtrl-sci)
Probing deuterium-induced magnetic phase transitions in TbCo alloys with in-situ polarized neutron reflectometry
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Robbie G. Hunt, Gunnar K. Pálsson, Matías P. Grassi, Victoria Kabanova, Alexey Vorobiev, Gabriella Andersson
Hydrogen-based magneto-ionics is a promising approach for rapid magnetoelectric control of spintronic devices. Most investigations so far into the magneto-ionic manipulation of rare-earth transition-metal alloys have used electrochemical methods for evaluating the magnetoelectric properties, but this technique makes it difficult to discriminate between the effects of competing ionic species. In this work, we use atmospheric loading to evaluate the effect of an isotope of hydrogen, deuterium, on the magnetic properties of TbCo films using in-situ polarized neutron reflectometry. With this approach, we are able to simultaneously measure the magnetization, thickness expansion and deuterium concentration of TbCo films. We quantitatively observe the deuterium concentrations at which the paramagnetic phase transition occurs for a Tb-rich film, and the weakening of out-of-plane magnetic anisotropy for a Co-rich film. For the Tb-rich film the expansion of the film thickness is the primary mechanism identified for the paramagnetic phase transition, while for the Co-rich film no thickness expansion is observed. We also find that an oxidized interface is insensitive to deuterium loading, but remains exchange coupled to the rest of the film and can be indirectly manipulated by loading of deuterium in the alloy. We expect these results to be directly translatable to that of hydrogen.
Materials Science (cond-mat.mtrl-sci)
12 pages, 7 figures
On the interpretation of Hahn echo measurements in electron spin resonance scanning tunneling microscopy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Paul Greule, Wantong Huang, Máté Stark, Kwan Ho Au-Yeung, Christoph Wolf, Soo-hyon Phark, Andreas J. Heinrich, Philip Willke
Electron spin resonance scanning tunneling microscopy (ESR-STM) has become a powerful tool for probing spin dynamics and coherence of individual atoms and molecules on surfaces. In this work, we perform Rabi oscillation and Hahn echo pulse protocols on individual iron phthalocyanine (FePc) molecules on MgO/Ag(001) using ESR-STM. While Hahn echo protocols are widely used to extract spin coherence times, we show that in ESR-STM they are particularly susceptible to misinterpretation due to tunneling electrons generated by the applied radio-frequency (RF) voltage. The RF voltage not only drives the spin, but simultaneously probes and relaxes it, which consequently leads to an exponential decay that reflects spin relaxation rather than intrinsic phase coherence. We moreover show that varying both delay times in the refocusing pulse sequence is a reliable way to ensure a coherent nature of the echo signal. The extracted decay for the latter protocol suggests that T2 is approximately 30 ns and is thus closer to the decoherence time observed in Rabi oscillation measurements. This is significantly shorter than values reported in previous echo measurements. Our findings underscore the need for caution in interpreting T2 times from Hahn echo and Carr-Purcell protocols in ESR-STM and provide practical criteria for distinguishing true spin echoes from tunneling-induced relaxometry signals.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
12 pages, 5 figures
Euler band topology and multiple hinge modes in three-dimensional insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Yutaro Tanaka, Shingo Kobayashi
In two-dimensional systems with space-time inversion symmetry, such as $ C_{2z}T$ , the reality condition on wave functions gives rise to real band topology characterized by the Euler class, a $ \mathbb{Z}$ -valued topological invariant for a pair of real bands in the Brillouin zone. In this paper, we study three-dimensional $ C_{2z}T$ -symmetric insulators characterized by $ \bar{e}2$ , defined as the difference in the Euler classes between two $ C{2z}T$ -invariant planes in the three-dimensional Brillouin zone. By deriving effective surface Hamiltonians from generic low-energy continuum Hamiltonians characterized by the topological invariant $ \bar{e}_2$ , we reveal that multiple gapless boundary states exist at the domain walls of the surface mass, which give rise to the multiple chiral hinge modes. We also show that three-dimensional insulators characterized by $ \bar{e}_2=N$ support $ N$ chiral hinge modes. Notably, due to the constraint of two occupied bands in our system, these phases are distinct from stacked Chern insulators composed of $ N$ layers. Furthermore, we construct tight-binding models for $ \bar{e}_2=2$ and $ 3$ and numerically demonstrate the emergence of two and three chiral hinge modes, respectively. These results are consistent with those obtained from the surface theory.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages, 6 figures
Sign control of photocurrents by spin-group-symmetry breaking in altermagnetic insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Gastón Blatter, Xiao Zhang, Jeroen van den Brink, Mengli Hu, Shu Zhang
Controlling physical responses through symmetry breaking is a central paradigm in quantum materials, enabling novel functionalities. Here we determine the effects of spin-group-symmetry breaking on nonlinear optical responses of collinear altermagnetic insulators. Using shear strain as an example, we show that the direction of symmetry-breaking induced components of charge and spin photocurrents are locked to the sign of the strain. In the absence of spin-orbit coupling, this effect is intuitively captured by the spin-gap asymmetry–an imbalance between spin-up and spin-down direct band gaps which couples trilinearly with the Néel order and the strain. We demonstrate this mechanism with density functional theory calculations on the recently proposed altermagnet CuWP$ _2$ S$ _6$ . Having symmetry-guided control of both charge and spin photocurrents allows, vice versa, to reveal and investigate altermagnetism in insulating materials by exploration of their optical responses.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
8 pages, 4 figures
Simulation of single-qubit gates in spin-orbit coupled Bose-Einstein condensate with cubic-quintic nonlinearity by nonlinear perturbations
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-03-30 20:00 EDT
Prithwish Ghosh, Kajal Krishna Dey, Golam Ali Sekh
We consider spin-orbit coupled Bose-Einstein condensates with cubic-quintic nonlinear interaction within the framework of second quantization formulation and find eigen states using numerical simulation and mean-field approximation. We show that two low-lying Schrodinger cat states remain degenerate up to a certain value of Raman coupling strength and these states can serve as qubit basis. We take three different nonlinear perturbations and find that the perturbations can result in different rotations of qubit state on Bloch sphere. We calculate the unitary operator corresponding to each perturbation and suggest the possibilities for obtaining various gates in ultra-cold atomic system.
Quantum Gases (cond-mat.quant-gas)
9 pages, 6 figures
Crystalline b-Ga2O3 thin films deposited via reactive magnetron sputtering of a liquid Ga target
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Petr Novak, Jan Koloros, Stanislav Haviar, Jiri Rezek, Pavel Baroch
Ga2O3 thin films were deposited by reactive magnetron sputtering from a liquid gallium target. The influence of deposition temperature, substrate type, and discharge parameters on the structural and electrical properties was systematically investigated. Films deposited on silicon and quartz glass exhibit polycrystalline growth, whereas sapphire substrates enable highly oriented growth of b-Ga2O3 with a preferred (-201) orientation. The lowest electrical resistivity of 7x10_3 this http URL was obtained for films deposited on sapphire at a temperature of 585C. At this temperature, the films reach sufficient crystalline quality to enable efficient charge carrier transport and thus the manifestation of unintentional conductivity. At higher deposition temperatures, pronounced crystallization occurs; however, it is not homogeneous throughout the entire film thickness, which leads to a deterioration of the electrical properties. These results demonstrate that, despite intrinsic limitations, reactive magnetron sputtering can be successfully employed for the preparation of Ga2O3 thin films with optimized electrical properties when appropriate substrates and deposition temperatures are selected.
Materials Science (cond-mat.mtrl-sci)
Emergence of multiple quasi-ferromagnetic magnon modes induced by strong magnetoelastic coupling in $TmFeO_3$ single crystal
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Sourabh Manna, Felix Fuhrmann, Olena Gomonay, Xiaoxuan Ma, Haiyang Chen, Luca M. Carrella, Sergio Rodríguez Fernández, Edgar Galindez-Ruales, Jairo Sinova, Shixun Cao, Mathias Kläui
We investigate the magnetization dynamics of $ TmFeO_3$ single crystals across the spin-reorientation phase transition using broadband microwave absorption spectroscopy up to 87.5 GHz. Temperature- and magnetic-field-dependent antiferromagnetic resonance measurements reveal the characteristic softening of the quasi-ferromagnetic (q-FM) resonance mode at the $ \Gamma_2\rightarrow\Gamma_{24}$ and $ \Gamma_{24}\rightarrow\Gamma_4$ transition points. The finite magnon gap observed at the transition points reflects the strong magnetoelastic coupling. In addition to the uniform q-FM mode, multiple magnon modes appear in the intermediate $ \Gamma_{24}$ phase, separated by approximately 0.5–2 GHz and exhibiting similar field and temperature dependence. These additional modes are attributed to nonuniform spin-wave excitations arising from the periodic magnetic domain structure present in the intermediate phase and their hybridization with acoustic phonons mediated by strong magnetoelastic coupling. Our results demonstrate that the spin-reorientation transition in $ TmFeO_3$ provides a natural platform for generating multiple hybridized magnon modes, offering new opportunities for tunable magnonic excitations in rare-earth orthoferrites.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
13 pages, 4 figures
Ultrafast Formation and Annihilation of Strongly Bound, Anisotropic Excitons
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Lawson T. Lloyd, Tommaso Pincelli, Mohamed Amine Wahada, Alessandro De Vita, Ferdinand Menzel, Kseniia Mosina, Túlio H. L. G. Castro, Alexander Neef, Andreas V. Stier, Nathan P. Wilson, Zdeněk Sofer, Jonathan J. Finley, Martin Wolf, Laurenz Rettig, Ralph Ernstorfer
Van der Waals (vdW) layered materials with long-range magnetic order have the potential to enable novel optoelectronic and spintronic applications. Among these, CrSBr is an air-stable, direct band gap semiconductor that hosts interlayer antiferromagnetic order, a highly anisotropic electronic structure, and strongly bound excitons. In particular, excitons in CrSBr have been shown to inherit the quasi-one-dimensional nature of the material and also couple to the underlying spinorder. However, mechanisms of exciton formation, dissociation, and interaction with free carriers remain largely unexplored, despite being crucial for spintronic and optoelectronic applications. Here, we employ time- and angle-resolved photoemission spectroscopy to map the electronic structure and excited state dynamics in CrSBr. We directly resolve an exceptionally large exciton binding energy (~800 meV) and a highly anisotropic momentum space distribution of the exciton, revealing its quasi-1D real-space character. We observe an excitation-density-dependent interconversion between bound excitons and quasi-free carriers on sub- to few-picosecond timescales, indicating that many-body effects govern the excited-state dynamics and optical properties during the initial stages of relaxation. Our work highlights the strongly bound, anisotropic character of excitons in CrSBr, as well as the microscopic interactions steering relaxation pathways after photoexcitation in elevated density regimes relevant for future device applications.
Materials Science (cond-mat.mtrl-sci)
Hunting Structural Demons in Digital Reticular Chemistry
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Yongchul G. Chung, Myoung Soo Lah
Digital reticular chemistry relies on accurate crystal structures to power computational screening, data-driven discovery, and structure-property analysis, yet recent studies reveal that more than half of the top-performing candidates in major computational screening campaigns are chemically invalid. In experimental MOF databases, structural errors arise when disordered or incomplete structural models are incorrectly converted into fully specified simulation inputs. In hypothetical MOF database, structures are complete by construction but may encode chemically implausible oxidation states, coordination environments, or charge distributions. We term these erroneous structural models “structural demons.” This mini-review asks three questions: where these errors enter, how we find them, and how we prevent them. On the prevention side, the key steps are keeping diffraction data and synthesis details together from the start, using consistent curation when structures enter a database, and filtering topology choices before structure generation. Connecting these steps can keep many bad structures out of downstream databases and reduce the need to fix them later.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Antiferromagnetic stripe phase and large-gap insulating ground state of the correlated $\sqrt{3}\times\sqrt{3}$~R30$^{\circ}$-Sn/Si(111) single atomic layer
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-03-30 20:00 EDT
Mohammadmehdi Torkzadeh, Mattia Iannetti, Mathieu Lizée, Amitayhush Thakur, Maris Hervé, Francois Debontridder, Pascal David, Michele Casula, Gianni Profeta, Tristan Cren, Matteo Calandra, Cesare Tresca, Christophe Brun
The one-third monolayer Sn layer on Si(111) has long been considered a benchmark system for exploring two-dimensional Mott physics, owing to its narrow bandwidth and sizable on-site Coulomb repulsion. Previous experiments suggested the emergence of a low-temperature Mott insulating phase with an energy gap of only a few tens of meV, while theory predicted a possible antiferromagnetic ordering that remained experimentally elusive. Here, by combining low-temperature scanning tunneling microscopy/spectroscopy with first-principles calculations, we reveal that the $ \sqrt{3}\times\sqrt{3}$ ~R30$ ^{\circ}$ -Sn/Si(111) surface undergoes a transition below 30K into a robust insulating state characterized by a remarkably large gap of about 440 $ \pm$ 120 meV at 4K, five to ten times larger than previously reported. Quasiparticle interference imaging uncovers a well-defined $ 2\sqrt{3}\times\sqrt{3}$ ~R30$ ^{\circ}$ -Sn/Si(111) superstructure, providing direct evidence for a two-dimensional stripe-like antiferromagnetic order. Ab initio calculations reveal that the silicon substrate stabilizes this phase through strong nonlocal tin-tin interactions, highlighting the decisive role of substrate-driven correlations in the $ \sqrt{3}\times\sqrt{3}$ ~R30$ ^{\circ}$ -Sn/Si(111) system.
Strongly Correlated Electrons (cond-mat.str-el)
14 pages, 9 figures
Strain-released epitaxy of GaN enabled by compliant single-crystalline metal foils
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Yaqing Ma, Junwei Cao, Huaze Zhu, Yijian Song, Huicong Chen, Menglin He, Jun Yang, Ping Jiang, Tong Jiang, Han Chen, Xiang Xu, Yuqiao Zheng, Hao Wang, Muhong Wu, Yu Zou, Xiaochuan Chen, Tongbo Wei, Kaihui Liu, Wei Kong
Heteroepitaxy conventionally relies on rigid crystalline substrates, implicitly assuming that lattice and thermal mismatch must be accommodated within the epitaxial layer, leading to residual strain and defects that worsen with increasing substrate size. Here we demonstrate a substrate-mediated strain-partitioning regime in which lattice and thermal mismatch are preferentially partitioned into the substrate rather than stored in the epitaxial layer. We report the epitaxial growth of single-crystalline GaN on mechanically compliant yet crystallographically ordered single-crystalline copper foils. Atomic-resolution microscopy, geometric phase analysis and density functional theory reveal that mismatch-induced stress is primarily screened by elastic deformation of the Cu lattice, accompanied by localized interfacial slip confined to a few atomic layers, leaving the AlN and GaN epilayers nearly strain-free despite large nominal mismatch. Leveraging this strain-released epitaxial platform, we further demonstrate dense GaN micro-light-emitting diode arrays that benefit from efficient vertical electrical conduction and thermal dissipation enabled by the metallic substrate. By establishing compliant single-crystal metal foils as a new substrate class, this work identifies mechanical contrast as an underexplored governing parameter in heteroepitaxial design, with implications extending beyond GaN.
Materials Science (cond-mat.mtrl-sci)
Coherent Ultrafast Excitonic Oscillations in Monolayer WS$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Jorge Cervantes-Villanueva, Alberto García-Cristóbal, Davide Sangalli, Alejandro Molina-Sánchez
Monolayer transition metal dichalcogenides are a suitable platform for studying excitonic coherence in the light-matter coupling regime. We present an ab initio time-dependent GW-Bethe-Salpeter equation (GW-BSE) investigation of coherent excitonic dynamics in monolayer WS$ _2$ . By solving the coherent coupling between the A, A$ ^{\ast}$ , and B excitons under linearly polarized pump fields, we identify the microscopic origin of the resulting oscillatory dynamics and rationalize it using an effective theoretical model. Our results provide the interpretation of recently reported coherent excitonic phenomena in monolayer WS$ _2$ (Nano Lett. 24, 8117 (2024)). Building on this first-principles time-resolved framework, we propose a tailored pump-probe scheme that enables the controlled generation and regeneration of coherent oscillations between excitonic states. These findings establish a predictive route for controlling excitonic coherence in two-dimensional materials, with direct relevance for ultrafast optoelectronic switches and solid-state quantum logic devices.
Materials Science (cond-mat.mtrl-sci)
7 pages, 3 figures
Interstitial-Electron Altermagnetism in Two Dimensions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-03-30 20:00 EDT
Xia Cheng, Yang Wu, Zhenzhou Guo, Tie Yang, Weizhen Meng, Zhenxiang Cheng, Zhi-Ming Yu, Xiaotian Wang
Altermagnetism has so far been associated with compensated magnetic moments carried by atoms. Here we introduce Stoner instability induced interstitial-electron altermagnetism, a distinct mechanism in which altermagnetic order is carried instead by interstitial anionic electrons in electrides. We show that, owing to the quasi-nucleus-free nature of interstitial electrons, the Stoner instability in electrides hosting two interstitial electrons can naturally stabilize an altermagnetic state rather than the conventional ferromagnetic one. This mechanism leads to a practical design principle for two-dimensional materials, from which we identify monolayers Zr2N and Ti2N as representative candidates. The strong sensitivity of interstitial electrons to cavity size enables efficient strain control of the altermagnetic order and a pronounced piezo-altermagnetic effect. Moreover, we investigate the evolution of the magnetism in Zr2N under ultrafast laser excitation, which exhibits dynamics distinct from those in all previously reported magnetic materials where magnetism is carried by real atoms. Our work not only offers a novel pathway to realize altermagnetism but also reveals an efficient non-magnetic route for its control.
Strongly Correlated Electrons (cond-mat.str-el)
Emergence of ferromagnetic state due to structural disorder in pseudo-binary Ce(Fe0.9Co0.1)2 compound
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Andrzej Musiał, Maria Pugaczowa-Michalska, Natalia Lindner, Zbigniew Śniadecki
The changes in magnetic properties of Ce(Fe0.9Co0.1)2 compound with increasing disorder are discussed in the paper. Homogeneous alloys are known to undergo the phase transition from ferromagnetic to antiferromagnetic state accompanied by the structural distortion of the cubic Laves C15 phase into the rhombohedral one. Various stimuli, like the structural disorder, or applied magnetic field, can force the emergence of ferromagnetism at low temperatures. We initially introduced the structural disorder using rapid quenching. Further changes were made by severe plastic deformation. The presence of a ferromagnetic phase in a low-temperature region is reported here and accompanies the deterioration of a first-order phase transition. We show, based on electronic calculations, that the structural motifs arising from various distortions of the initial MgCu2-type structure, caused by the partial replacement of Fe with Co atoms, are characterized by stable antiferromagnetic order. This neglects simple structural distortions as the source of ferromagnetism. The presence of a strongly defective structure understood as a topologically disordered volume, reduced the fraction transformed from a ferromagnetic to an antiferromagnetic state. Therefore, a strong reduction of isothermal entropy changes was also observed, as it decreased from 1.94 Jkg-1K-1 and -1.43 Jkg-1K-1 ({\Delta}{\mu}0H = 4 T) to 0.30 Jkg-1K-1 and -0.96 Jkg-1K-1 for antiferromagnetic-ferromagnetic and ferromagnetic-paramagnetic transition, respectively.
Materials Science (cond-mat.mtrl-sci)
26 pages, 9 figures
Metallurgical and Materials Transations A 56 (2025) 1983-1993
Anomalous Nonlinear Magnetoconductivity in van der Waals Magnet CrSBr
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Junhyeon Jo, Manuel Suárez-Rodríguez, Samuel Mañas-Valero, Eugenio Coronado, Ivo Souza, Fernando de Juan, Fèlix Casanova, Marco Gobbi, Luis E. Hueso
Nonlinear magnetoconductivity (NLMC) is a nonreciprocal transport response arising in non-centrosymmetric materials. However, this ordinary NLMC signal vanishes at zero magnetic field, limiting its potential for applications. Here, we report the observation of an anomalous NLMC controlled by internal order parameters such as the magnetization or Néel vectors. We achieve this response by breaking both inversion and time-reversal symmetry in artificial van der Waals heterostructures based on the magnetic CrSBr and insulating hBN. The nonreciprocal signal can be tuned between two different states in ferromagnetic monolayer CrSBr and among four different states in antiferromagnetic bilayer CrSBr, thanks to its metamagnetic transition. Remarkably, this output signal in the ferromagnetic (antiferromagnetic) state of CrSBr is three (one) orders of magnitude higher than those previously measured. A conductivity scaling analysis reveals the Berry connection polarizability as the origin of the anomalous NLMC. Our results pave the way for high-frequency rectifiers with magnetically switchable output polarity as well as for an efficient electrical readout of the magnetic state of antiferromagnetic materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages, 4 figures, and supporting information
Advanced Materials 37, 2419283 (2025)
Towards a unified first-principles-based description of VO$_2$ using DFT+DMFT with bond-centered orbitals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-03-30 20:00 EDT
Peter Mlkvik, Nicola A. Spaldin, Claude Ederer
We present a combined density-functional theory and dynamical mean-field theory (DFT+DMFT) study of the full structural phase space of rutile-based vanadium dioxide (VO$ _2$ ), including also the less studied M2 and T phases, using an unconventional bond-centered orbital basis. The use of bond-centered orbitals allows us to treat all main phases of VO$ _2$ , and the structural transitions between them, using one consistent approach with moderate computational cost and without pre-pattering of the structure into dimerized and undimerized V–V pairs. We obtain two distinct insulating states on the two different types of vanadium chains in the M2 phase, a singlet-insulator on the dimerized chains and a Mott-insulator on the zigzag-distorted chains, which, however, are strongly coupled in the M2 phase and thus the metal-insulator transition always occurs concomitantly for both types of sites. We also demonstrate that the M2 phase corresponds to a local energy minimum in the structural phase space of VO$ _2$ , the stability of which, apart from the internal structural distortion, depends crucially on the unit cell strain relative to the undistorted rutile phase. Our calculations further indicate that the symmetry-distinct triclinic T phase corresponds electronically to either an M1 or an M2-type insulator with an abrupt transition as a function of distortion. Finally, we disentangle the effect of the dimerization and zigzag distortions by constructing hypothetical structures that contain only one site type, finding that the zigzag distortion strongly favors emergence of the Mott-insulating state, both as function of distortion and on-site interaction.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Importance of Electronic Entropy for Machine Learning Interatomic Potentials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Martin Hoffmann Petersen, Steen Lysgaard, Arghya Bhowmik, Kedar Hippalgaonkar, Juan Maria Garcia Lastra
Machine learning interatomic potentials (MLIPs) enable large-scale atomistic simulations but remain challenged in describing mixed-valence materials where charge ordering strongly influences thermodynamic stability. Here we investigate the role of electronic entropy in MLIP structural optimization of the battery cathode material \ce{NaFePO4}. We show that conventional MLIPs fail to reproduce the correct stability of intermediate \ce{Na} concentrations because structural optimization leads to incorrect \ce{Fe^{2+}}/\ce{Fe^{3+}} charge assignments, resulting in erroneous energy ordering and convex-hull predictions. Analysis of magnetic moments during structural optimization reveals that MLIPs are unable to capture electronic entropy associated with charge ordering. To address this limitation, we introduce an approach that embeds charge-state information directly into the MLIP representation by distinguishing between \ce{Fe^{2+}} and \ce{Fe^{3+}} environments during training. Retraining CHGNet, cPaiNN, and MACE with this representation enables accurate structural optimization, correct identification of charge ordering, and improved agreement with density functional theory convex hulls. Our results demonstrate that incorporating electronic entropy into MLIP representations is essential for modeling charge-disordered materials and provide a practical framework for extending MLIP simulations to mixed-valence transition-metal systems.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Caloric Phenomena and Stirling-Cycle Performance in Heisenberg- Kitaev Magnon Systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-03-30 20:00 EDT
Bastian Castorene, Martin HvE Groves, Francisco J. Peña, Nicolas Vidal-Silva, Miguel Letelier, Roberto E. Troncoso, Felipe Barra, Patricio Vargas
We investigate the Stirling-cycle performance of a Heisenberg–Kitaev magnonic medium with Dzyaloshinskii–Moriya (DM) interactions. Using linear spin-wave theory, we show the DM interaction preserves spectral symmetry, yielding even caloric responses and symmetric Stirling engine efficiency. In contrast, bond-dependent Kitaev exchange asymmetrically distorts the magnonic density of states, enabling distinct direct and inverse caloric effects. Consequently, Kitaev-driven cycles achieve significantly higher efficiencies than DM-driven protocols, approaching a high-performance saturation regime for negative couplings. This establishes exchange-anisotropic magnets as highly tunable platforms for nanoscale solid-state energy conversion.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Analysis of the singular band structure occurring in one-dimensional topological normal and superfluid fermionic systems: A pedagogical description
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-03-30 20:00 EDT
Marcello Calvanese Strinati, Giancarlo Calvanese Strinati
Topological properties of solid-state materials arise when crossings occur in their band-structure eigenvalues, which give rise to discontinuities in the associated Bloch-function eigenvectors once these are mapped over the whole Brillouin zone. These nonanalytic properties have direct consequences on the spatial decay of the corresponding Wannier functions, leading to what is nowadays referred to as the “obstruction to finding symmetric Wannier functions” for a given set of bands, as well as on the need for shifting the Wannier functions to interstitial positions, related to what is nowadays known as the “bulk-boundary correspondence.” The importance of nonanalytic points of Bloch eigenfunctions and their consequences for the spatial decay of Wannier functions were historically anticipated back in 1978 [G. Strinati, Phys. Rev. B 18, 4104-4119 (1978)], somewhat before the work of Berry on what came to be referred to as the “Berry phase” [M. V. Berry, Proc. R. Soc. London, Ser. A 392, 45 (1984)]. In particular, the former paper identified key precursors and physical insights that are now understood, in hindsight, to be closely related to the later developments mentioned above. Here, we recap the essential features of these key issues in a rather pedagogical way, by considering in full details two instructing examples for which the origin of the discontinuities in the eigenvectors can be readily traced and mapped out, and the rate of the spatial falloff of the associated Wannier functions can be fully determined. For this analysis to be as complete as possible, two cases, one for noninteracting and one for interacting fermions, are considered on equal footing.
Quantum Gases (cond-mat.quant-gas)
19 pages, 10 figures. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appears in AVS Quantum Sci. 8, 016201 (2026) and may be found at this https URL
AVS Quantum Sci. 8, 016201 (2026)
Efficient evaluation of the $k$-space second Chern number in four dimensions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Xiang Liu, Xiao-Xia Yi, Zheng-Rong Liu, Rui Chen, Bin Zhou
We propose an efficient numerical method to compute the $ k$ -space second Chern number in four-dimensional (4D) topological systems. Our approach employs an adaptive mesh refinement scheme to evaluate the Brillouin-zone integral, which automatically increases the grid density in regions where the Berry curvature is sharply peaked. We compare our method with the 4D lattice-gauge extension of the Fukui-Hatsugai-Suzuki method and a direct uniform grid integration scheme. Compared with these approaches, our method (i) achieves the same accuracy with substantially fewer diagonalizations, and thus runs faster; (ii) requires minimal memory to execute, enabling calculations for larger systems; and (iii) remains accurate even near topological phase transitions where conventional methods often face challenges. These results demonstrate that the adaptive subdivision strategy is a practical and powerful tool for calculating the $ k$ -space second Chern number.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Electron- and Lattice-Temperature Dependence of the Optical Response of Gold Nanoparticles
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Nour E. H. Chetoui, Jonas Grumm, Robert Lemke, Andreas Knorr, Holger Lange
Transient absorption spectroscopy is routinely used to study the electron dynamics in plasmonic gold nanoparticles. Typically, the transient absorption bleach is analyzed as measure for the electron temperature. However, the implicitly assumed linear dependence between bleach intensity and temperature has not been systematically studied. Similarly, the influence of lattice heating also lacks a detailed analysis. Here, we solve momentum-resolved metal Boltzmann-Bloch equations for a semi-analytic access to the temperature-dependent gold nanoparticle absorption. We confirm the theory with steady state and transient absorption experiments, define regions of linear correlation between transient absorption bleach intensity and electron temperature and reveal a strong impact of the lattice temperature on the TA bleach intensity.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Non-additive Ion Effects on the Coil-Globule Equilibrium of a Generic Uncharged Polymer
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-03-30 20:00 EDT
Kushagra Goel, Monika Choudhary, Swaminath Bharadwaj
Mixtures of weakly and strongly hydrated anions induce non-additive changes in the LCST of thermoresponsive polymers such as Poly(N-isopropylacrylamide) (PNIPAM) and PEO. Large-scale atomistic simulations of PNIPAM-NaI-Na$ _{2}$ SO$ _{4}$ mixtures show that these effects arise from the interplay between favorable PNIPAM-iodide interactions and the depletion of strongly hydrated sulfate ions. Here, we investigate whether chemically specific polymer-anion interactions are necessary to reproduce such behavior. To this end, we study the coil-to-globule transition of a generic uncharged linear polymer with non-specific polymer-water and polymer-ion van der Waals interactions in atomistic aqueous solutions of single and mixed salts. We perform simulations at fixed concentrations of the strongly hydrated salt, Na$ _{2}$ SO$ _{4}$ , and increasing concentrations of weakly hydrated salts, NaSCN and NaI. The generic polymer qualitatively reproduces experimental trends in both pure NaSCN and Na$ _{2}$ SO$ _{4}$ solutions, as well as in mixed salt solutions. The model captures the mutual reinforcement between SCN$ ^{-}$ accumulation near the polymer and SO$ _{4}^{2-}$ depletion that gives rise to non-additive behavior, consistent with atomistic simulations in PNIPAM solutions. These features become more pronounced with increasing background salt concentration and are further enhanced upon replacing SCN$ ^{-}$ with I$ ^{-}$ , owing to weaker polymer-iodide interactions. Our results demonstrate that non-specific polymer-ion interactions are sufficient to reproduce non-additive features, highlighting the dominant role of bulk ion-ion and ion-water interactions.
Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph)
Main text: 13 pages, 4 figures, Supplementary information is included after the references
Mean-field theory of the Stribeck effect
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-03-30 20:00 EDT
Vincent Bertin, Olivier Pouliquen
We present a theoretical analysis of frictional transitions along the Stribeck curve for rough elastic contacts lubricated by a Newtonian fluid. Building on the mean-field framework of Persson and Scaraggi (J. Phys.: Condens. Matter 21 (2009) 185002), we formulate a minimal elastohydrodynamic model that couples contact mechanics and lubrication through a homogenized pressure decomposition. Dimensional analysis reveals three independent dimensionless parameters governing the frictional response, which correspond to a dimensionless speed, normal load, and surface roughness.
Using asymptotic expansions, we first characterize the boundary and hydrodynamic lubrication regimes, which arise naturally as the quasistatic and smooth-surface limits of the model. In both limits, the contact morphology converges toward Hertzian contact in the regime of large elastic deformation, with boundary layers regularizing the separation profile at the edge of the contact zone.
We then analyze the mixed lubrication regime and derive asymptotic expressions for the friction coefficient in the low- and high-speed limits. At high speeds, friction decomposes into a viscous contribution and a residual contact term, leading to a roughness- and load-dependent criterion for the transition to hydrodynamic lubrication that departs from constant-{\Lambda} ratio theories. At low speeds, friction reduction results from the progressive redistribution of the applied load between asperity contact and hydrodynamic pressure, yielding a characteristic transition speed from boundary to mixed lubrication. These results are summarized in a phase diagram that generalizes the classical Stribeck curve to a multidimensional parameter space.
Soft Condensed Matter (cond-mat.soft), Fluid Dynamics (physics.flu-dyn)
24 pages, 12 figures
Contrasting Spin Excitations in Octahedral and Square-Planar n=8 Ruddlesden-Popper Nickelates
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-03-30 20:00 EDT
K. Scott, H. LaBollita, G. A. Pan, X. Yang, A. Kar, C. Lim, A. Thorshov, D. Ferenc Segedin, C. M. Brooks, F. Yakhou-Harris, K. Kummer, N. B. Brookes, F. Boschini, A. Frano, J. A. Mundy, E. H. da Silva Neto, A. S Botana, S. Blanco-Canosa
The discovery of superconductivity in reduced square-planar nickelates marked a major advance in identifying structural and electronic analogs to the high-$ T_c$ cuprates. The more recent observation of superconductivity in parent Ruddlesden-Popper (RP) octahedral nickelates with a clear difference in electron count with respect to cuprates raises new questions about the nature of superconductivity across these related but distinct nickelate families. Here, we use Ni $ L_3$ -edge resonant inelastic x-ray scattering (RIXS) to probe the low-energy excitations in a representative compound of both families: the parent octahedral $ n=8$ RP phase Nd$ _9$ Ni$ _8$ O$ _{25}$ (p-RP), which is non-superconducting, and its reduced square-planar counterpart Nd$ _9$ Ni$ _8$ O$ {18}$ (r-RP), which exhibits superconducting correlations with a $ T_c \approx 5$ K. The $ n=8$ p-RP develops a spin-density-wave (SDW) ground state with ordering wave vector $ q{\mathrm{SDW}} = (1/4,, 1/4)$ , analogous to the bilayer RP, while the $ n=8$ r-RP shows an elastic peak at $ q^\star = (1/3,, 0)$ . Polarimetric RIXS shows that the p-RP exhibits low-energy spectra dominated by weakly dispersive paramagnons along the 0$ \rightarrow\pi$ and $ \pi !\rightarrow! \pi$ directions, whereas the r-RP with superconducting correlations displays dispersionless magnetic excitations. Our results comprehensively map out the spin excitations and reveal fundamental differences in the ground state between these two distinct structural families.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
8 pages, 4 figures
Non-equilibrium Green’s function formalism for radiative heat transfer
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-03-30 20:00 EDT
Radiative heat transfer (RHT) at the nanoscale can vastly exceed the far-field blackbody limit due to the tunneling of evanescent waves, a phenomenon traditionally described by fluctuational electrodynamics (FE). While FE has been exceptionally successful for systems in local thermal equilibrium, its foundational assumptions break down in the growing number of scenarios involving genuine non-equilibrium conditions, such as in active devices or driven materials. This review introduces the non-equilibrium Green’s function (NEGF) formalism as a powerful and versatile framework to study RHT beyond these classical limits. Rooted in quantum many-body theory, NEGF provides a unified language to describe energy transport by photons, electrons, and phonons on an equal footing. We first outline the theoretical foundations of the NEGF approach for RHT, demonstrating how it recovers the canonical results of FE in the local equilibrium limit. We then survey recent breakthroughs enabled by NEGF, including: (i) providing a quantum-accurate description of equilibrium RHT that naturally incorporates non-local and finite-size effects, resolving unphysical divergences predicted by local models; (ii) unifying heat transfer channels to reveal the non-additive synergy between radiation, electron tunneling, and phonon conduction at sub-nanometer gaps; (iii) enabling the quantum design of materials and metamaterials with tailored thermal properties through band structure and topological engineering; and (iv) describing active control of heat flow in driven systems, which allows for phenomena like isothermal heat transfer and pumping heat against a temperature gradient.
Statistical Mechanics (cond-mat.stat-mech)
22 pages,4 figures
J. Phys.: Condens. Matter 37 (2025) 473002
Refining hydrogen positions in α-FeOOH through combined neutron diffraction and computational techniques
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-03-30 20:00 EDT
Yusuke Nambu, Akihide Kuwabara, Masahiro Kawamata, Seira Mori, Megumi Okazaki, Kazuhiko Maeda
The hydrogen positions and magnetic structure of goethite $ \alpha$ -FeOOH, a key component of iron rust, were examined through neutron diffraction. All symmetry-allowed magnetic structures under the space group $ Pnma$ with the magnetic wavevector $ \vec{q}_{\rm m} = (0, 0, 0)$ r.l.u. were analysed using irreducible representation and magnetic space group approaches. The magnetic moments aligned along the $ b$ -axis form antiferromagnetic spin arrangements, as reproduced by first-principles calculations. Accurately determining the hydrogen positions is crucial for understanding the mechanism of catalytic reduction of CO$ _2$ in $ \alpha$ -FeOOH. These positions were precisely identified through diffraction and calculations, highlighting the effectiveness of using both methods for undeuterated compounds.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
8 pages, 5 figures
Dalton Transactions (Spotlight Collection: Mixed-Anion Compounds) (2006)
Beyond the Quantum Picture: The Electrodynamic Origin of Chiral Nanoplasmonics
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Vasil Saroka, Lorenzo Cupellini, Nicolò Maccaferri, Alessandro Fortunelli, Tommaso Giovannini
Chiral plasmonic nanostructures are rapidly emerging as ideal substrates for enantioselective sensing, chiral near-field engineering, and plasmon-assisted catalysis, owing to their exceptional sensitivity to structural handedness. However, the physical origin of plasmonic chirality, whether intrinsically quantum or primarily governed by collective electrodynamics, remains an open question, limiting the development of predictive theoretical methods for the design of novel chiral plasmonic architectures. Here, we show that a fully atomistic classical electrodynamic model, coupling intraband charge transport and interband polarization, quantitatively reproduces state-of-the-art \textit{ab initio} and experimental chiroptical spectra across the quantum-to-classical regime, from atomistically defined chiral Ag and Au nanostructures to DNA-origami-assembled Au nanorods containing up to $ \sim 10^5$ atoms. Our results support a unified electrodynamic origin of plasmonic chirality, providing the missing foundation to connect local structural motifs to chiroptical response and local chiral near fields, and paving the way for the atomistically defined, rational design of chiral plasmonic nanostructures optimized for targeted applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Computational Physics (physics.comp-ph), Optics (physics.optics)
23 pages, 4 figures
Gigahertz-clocked Generation of Highly Indistinguishable Photons at C-band Wavelengths
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-03-30 20:00 EDT
Robert Behrends, Lucas Rickert, Nils D. Kewitz, Martin v. Helversen, Partim K. Saha, Mareike Lach, Jochen Kaupp, Yorick Reum, Tobias-Huber-Loyola, Sven Höfling, Andreas Pfenning, Tobias Heindel
High-performance single-photon sources at telecom C-band wavelentghs are key building blocks for applications in long-distance quantum communication. Here, we report the generation of highly indistinguishable, single photons at a clock-rate of 2.5,GHz. This is achieved by coherently driving the biexciton transition ($ T_1^\mathrm{XX}=64(1),$ ps) of a semiconductor quantum dot embedded in a microcavity with strong asymmetric Purcell enhancement. Employing pulsed two-photon resonant excitation, strong multiphoton suppression with $ g^{(2)}(0) < 4%$ and high two-photon-interference visibility of $ V_\mathrm{raw}> 85%$ is observed. The observed photon indistinguishability is close to the theoretical limit expected for the photonically engineered radiative cascade and matches values obtained at lower repetition rates. Our results show a substantial advancement towards interference-based quantum information protocols at unprecedented data rates in the telecom C-Band.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
6 pages, 2 figures