CMP Journal 2026-11-02
Statistics
Nature Materials: 3
arXiv: 81
Research Square: 1
Nature Materials
Breaking symmetry in nanoparticle superlattices via spontaneous valency
Original Paper | Self-assembly | 2026-11-01 19:00 EST
Nicholas Sbalbi, Stephen Kronenberger, Hana Shinzawa, Matthew Ye, Arthi Jayaraman, Robert J. Macfarlane
Nanoparticle superlattices enable programmable material structure through ligand-mediated interactions, but attractive ligand interactions typically limit assembly to densely packed lattices that maximize nearest-neighbour bonding. Intentionally programmed directional bonding and valency are therefore typically assumed to require particle-level anisotropy in shape or surface patterning. Here, using assemblies of flexible, electrostatically active isotropic nanoparticles, we show that valency need not be encoded by particle geometry, but can instead emerge spontaneously during assembly. When ligand coronas are sufficiently deformable, ligands reconfigure to align along interparticle interfaces, generating an effective valency. Using a combination of experiment and simulation, we show that increasing ligand deformability lowers lattice coordination numbers, and identify design considerations for assembling isotropic building blocks into lattices with lower coordination, packing density and symmetry than would be predicted from hard-sphere packing. The work presented here therefore establishes ligand flexibility as a design parameter for programming coordination in nanoparticle assembly.
Self-assembly, Nanoparticles
Spin currents in polariton waveguides driven by bright and dark excitons
Original Paper | Electronic properties and materials | 2026-11-01 19:00 EST
Qiuyu Shang, Mingyang Zhang, Maria V. Maggi, Nathan W. E. Seet, Kevin Dini, Tianshu Zhao, Zexin Feng, Dong Yang, Maksym Gromovyi, Sebastien Chenot, Blandine Alloing, Abdullah Rasmita, Guillaume Malpuech, Timothy C. H. Liew, Dmitry Solnyshkov, Weibo Gao, Jesús Zúñiga-Pérez
The optical spin Hall effect enables the spatial separation of four domains of circularly polarized light from a linearly polarized source through photonic spin-orbit coupling, which arises from non-degenerate transverse-electric and transverse-magnetic modes. This mechanism is ineffective for incoherent photoluminescence. In transition metal dichalcogenide monolayers, bright excitons possess in-plane electric dipoles and strong oscillator strengths, whereas dark excitons have out-of-plane dipoles. Here, by embedding WS2 monolayers in waveguide microcavities, we demonstrate strong coupling between bright excitons and photonic modes, forming exciton-polaritons. Under non-resonant pumping, dark excitons become strongly populated and feed both transverse-magnetic- and transverse-electric-like exciton-polariton modes, each with an out-of-plane electric-field component. We observe the optical spin Hall effect in waveguide polaritons, leading to the formation of eight polarization domains and spin-polarized polariton currents propagating up to 92 ± 1 μm at room temperature. These results establish transition metal dichalcogenide-based polaritonic waveguides as a promising platform for room-temperature spin-optoelectronic devices.
Electronic properties and materials, Polaritons, Two-dimensional materials, Nanophotonics and plasmonics, Photonic devices
Process-intrinsic cellular network for sustained strength-ductility across temperatures in a 3D-printed multi-principal-element alloy
Original Paper | Metals and alloys | 2026-11-01 19:00 EST
Hyojin Park, Renhao Wu, Jae Heung Lee, Yoon-Uk Heo, Do Won Lee, Ji-Su Lee, Seon-Gyu Kim, Farahanz Haftlang, Sang Guk Jeong, Byeong-Joo Lee, Donghwa Lee, Hyoung Seop Kim
Laser-based additive manufacturing (LAM) provides a transformative route for fabricating Cr-Fe-Co-Ni-Al-Ti-based multi-principal element alloys (MPEAs). These alloys typically rely on L12 precipitate strengthening and thus require post-processing; however, such treatments rarely ensure stable mechanical performance over a wide temperature range. Here we designed a (CrFeCo)48Ni34Al7Ti5V5Ta1 MPEA with a self-assembled body-centred cubic/L21 precipitate cellular network formed intrinsically during LAM. Slip transfer and back-stress hardening across Kurdjumov-Sachs and Nishiyama-Wassermann interfaces and a weakly temperature-dependent stacking fault energy stabilize the dislocation-mediated deformation from 77 to 873 K. Consequently, the MPEA maintains a yield strength above 1 GPa and a uniform elongation of approximately 20% over a wide temperature range, indicating relatively stable tensile performance. This process-intrinsic pathway circumvents the need for post-treatment and reveals interface-mediated plasticity mechanisms. Our findings demonstrate that interface coherency engineering provides a foundation for designing strong yet ductile alloys with reduced temperature sensitivity via LAM.
Metals and alloys, Mechanical properties
arXiv
Mpemba effect as an entropy-production race:Finite-amplitude bounds on crossing times in Markovian relaxation
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Two canonical preparations evolving under a common final Markov generator can exhibit the Mpemba effect because they excite different relaxation modes. We bound the first crossing of their relative entropies by treating relaxation as an entropy-production race. The exact balance $ -\dot D=\dot e_p$ implies that a meeting occurs when the accumulated \emph{difference} of normalized entropy-production rates, $ \int_0^t(r_H-r_C),\mathrm ds$ with $ r_\alpha=\dot e_p^{\alpha}/D_\alpha$ , equals the initial logarithmic deficit $ \ln[D_H(0)/D_C(0)]$ . Global entropy-decay inequalities yield a lower crossing-time bound when the entropy-decay constant is bounded from below and the hot rate from above; we supply both certificates. A nonzero cubic moment of a slowest eigenfunction is sufficient for the modified logarithmic Sobolev constant to lie strictly below the spectral gap. Combining established relative-entropy comparison inequalities with Markov contraction and the actual mode amplitudes gives finite-amplitude crossing bounds without a small-deviation expansion. For an exactly strong, reversible three-state preparation these give $ 0.1659\le t_M\le0.1674$ in model time units, independently certified by outward-rounded interval arithmetic. This interval is narrower than $ 1%$ and contains $ t_M=0.1662209$ . The conservative global-rate comparison used here gives only $ t_M\ge0.042$ . The hotter preparation starts $ 6.12$ times farther from equilibrium, yet it reaches $ D=10^{-5}$ at $ t=0.233$ , compared with $ t=0.844$ for the colder one. Mean energy crosses later than relative entropy. For a fixed driven generator, nonadiabatic entropy production governs the same balance. These results concern finite-state relaxation in a specified distance and do not predict water-freezing times.
Statistical Mechanics (cond-mat.stat-mech)
20
SKFitter: Symmetry resolved Slater Koster tight-binding models from first principles for s, p, d and f electrons, spin orbit coupling and magnetism
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Sundeep Kapila, Bhaskaran Muralidharan, Satadeep Bhattacharjee
Constructing accurate and physically interpretable tight binding (TB) Hamiltonians from first principles calculations remains challenging, particularly for materials exhibiting complex orbital hybridization, spin orbit coupling (SOC), and magnetic order. SKFitter is an open-source Python framework for constructing and optimizing symmetry resolved Slater Koster TB models directly from density functional theory (DFT) calculations performed using Quantum ESPRESSO or VASP. The framework supports s to f orbitals, incorporates on site SOC and site resolved magnetic exchange interactions, and accommodates both orthogonal and nonorthogonal basis. A central feature is the symmetry resolved parameterization of orbital manifolds, which allows independent two centre hopping integrals between symmetry allowed orbital groups and across distinct neighbour shells. SKFitter also identifies missing orbital contributions and guide systematic basis set refinement and optimizes parameters through weights. The resulting Hamiltonian can be used to evaluate anomalous (AHC) and spin Hall conductivities (SHC), and topological invariants. We demonstrate the framework using eight representative materials spanning semimetals, semiconductors, transition metals, f-electron compounds, and magnetic systems. Symmetry resolved models achieve band energy errors of 9 to 41 meV within 1 eV of the Fermi level. The fitted Hamiltonians reproduce characteristic features of the SHC response of Pt, the SOC dependence of the AHC of Fe, and the momentum dependent altermagnetic spin splitting of MnTe without any altermagnet specific interaction. For EuMn2Bi2, projection guided orbital refinement reduces the near Fermi level fitting error from 120 to 32 meV. Together, these results establish SKFitter as a flexible and reproducible framework for developing symmetry consistent, physically interpretable TB models of complex materials.
Materials Science (cond-mat.mtrl-sci), Mathematical Software (cs.MS), Mathematical Physics (math-ph)
Open source software available at this https URL
Co–dsorption of terrylene and tetrapentacontane on hexagonal boron nitride - towards a two-dimensional Shpolskii matrix
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Rong Sun, Tolibjon Abdurakhmonov, Jan-Niklas Heidkamp, Julian Schröer, Paul Weinbrenner, Kenji Watanabe, Takashi Taniguchi, Tobias Korn, Oliver Kühn, Friedemann Reinhard
Organic molecular emitters are promising building blocks for quantum technologies, but their use at two-dimensional interfaces is limited by diffusion, aggregation, and photobleaching. We present work towards constructing an ultrathin two-dimensional Shpolskii-like host-guest matrix on hexagonal boron nitride (hBN) by co-depositing terrylene fluorophores with the long-chain tetrapentacontane in a solution-phase process. We demonstrate that this approach disperses terrylene in a roughly one-nanometer-thin alkane layer without detectable phase separation and allows tuning the emitter density from ensembles to isolated emitters showing characteristic blinking behavior consistent with single-molecule fluorescence. Time-lapse confocal microscopy, autocorrelation analysis, and fluorescence recovery after photobleaching show that suppressed diffusion and stable emitter positions can be achieved in several samples with a tetrapentacontane matrix. Encapsulation with hBN from the top side further improves photostability, with emitters demonstrating long lifetimes despite high photon doses. Successful co-adsorption of isolated emitters and alkane matrix is a milestone towards extending Shpolskii-type molecular isolation to hBN and provides a route towards stable, interface-integrated molecular qubits.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
9 pages, 4 figures
Thermal Stability and Structural Relaxation Kinetics of Commercially Pure Titanium
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Y. Semerenko, N. Galtsov, D. Hurova, T. Bednarchuk, P. Zinoviev, V. Zoryansky, V. Moskalenko, R. Smolianets, A. Smirnov, Y. Pohribna, N. Aksenova
This work explores the structural relaxation of cryorolled commercially pure titanium subjected to subsequent this http URL specimens with an average grain size of ~50 nm were produced by plastic deformation via cryogenic rolling at 100 K to a true strain of 1.20, followed by annealing at 425 K, 525 K, 725 K, and 945 K. Microstructural evolution was examined using electron microscopy and X-ray diffraction.
Cryogenic rolling was found to induce pronounced grain fragmentation, with coherent scattering regions (CSRs) of 30-50 nm dominating the substructure. X-ray diffraction analysis revealed that annealing drives crystallite growth: a slight increase at 525 K, accelerated coarsening at 725 K, and complete recrystallization at 945 K. The kinetics of grain growth follow the classical Lifshitz-Slyozov-Wagner model, with a growth exponent of ~4, reflecting the role of triple junctions and defect-controlled boundary diffusion. The activation energy, estimated at ~97 kJ/mol, corresponds to typical values for grain boundary diffusion in {\alpha}-Ti, confirming that cryogenic deformation produces a highly non-equilibrium microstructure whose relaxation is strongly temperature dependent.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
21 pages, 7 figures, 1 table
Spectral properties of orthorhombic KSbOSiO$_4$ crystals: studies of infrared, visible and ultraviolet radiation absorption, Raman scattering, cathodoluminescence and photoluminescence
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Vladimir A. Yuryev, Tatyana V. Yuryeva, Ekaterina A. Morozova, Irina F. Kadikova, Polina A. Edelbekova
Crystals of orthorhombic KSbOSiO$ _4$ (KSS) are often found to synthesize in glass of historical and artistic articles. For instance, these crystallites in the glass of turquoise Bohemian seed beads are known to play a significant role in the process of internal-stress driven corrosion of the glass causing deterioration and destruction of bead embroidered museum exhibits, especially articles made in the early 19th century. In art materials science, KSS has been known since the mid-2010s only for its destructive effects on historical glass objects, but as an optical material it has long been studied. KSS belongs to the group of compounds isomorphic to KTiOPO$ _4$ (KTP) and, like other compounds from this group, has anomalies in dielectric constant. The article presents the results of a study of orthorhombic KSS crystals using a number of spectroscopic techniques. IR absorption and diffuse reflection spectra of KSS in the spectral range from 50 to 4000~cm$ ^{-1}$ , its Raman spectrum, its absorption spectrum in the range from near infrared to ultraviolet as well as its cathodoluminescence and photoluminescence spectra are investigated. The constituent peaks of the spectral bands are analyzed and their properties are summarized in tables; the allowed direct and indirect band gaps of KSS are determined. The presented data are necessary both for the correct spectral analysis of historical and artistic glass and enamels, during the production of which this substance was sometimes synthesized in glass, and for a more in-depth study of crystals of the KTP group.
Materials Science (cond-mat.mtrl-sci)
40 pages, 12 figures, 6 tables
Kibble-Zurek dynamics beyond the thermodynamic limit
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Max Haas, Guy C. Moore, Isaac M. Craig, Kristin A. Persson, Jiali He, Michael E. Hjelmstad, Dennis Meier, Sinéad M. Griffin, Jan Schultheiß
The Kibble-Zurek mechanism (KZM) predicts the universal scaling of topological defect densities generated during continuous phase transitions, a result derived in the thermodynamic limit of homogeneous systems. Yet real materials are intrinsically finite and heterogeneous, raising the question of how nonequilibrium universality survives outside this idealized limit. Here we establish an ensemble-finite-size extension of the KZM that describes critical dynamics in collections of independent finite subsystems with distributed sizes. We test this framework using a polycrystalline model system undergoing a symmetry-breaking transition. We find that the density of topological vortices follows an apparent power law with an exponent approximately half that observed in single crystals. This reduced exponent emerges quantitatively from averaging over the experimentally measured grain-size distribution, without fitting to the measured vortex densities. Our results demonstrate that finite-size effects do not simply suppress KZ scaling but reorganize it into an emergent statistical scaling regime governed by system-size heterogeneity. This establishes microstructure and geometry as control parameters of nonequilibrium critical dynamics and provides a general strategy to engineer scaling behaviour in complex materials.
Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
Cavity-engineered ferroelectricity in SrTiO$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Omar Mehio, Sylvia Griffitt, Andrew Pierce, Emil V. Bostrom, Hanbyul Kim, Dylan P. Sotir, Darrell G. Schlom, Simone Latini, Kin Fai Mak, Jie Shan, Dongbin Shin, Angel Rubio, Ankit S. Disa
Interfacing quantum materials with photonic cavity architectures is at the vanguard of materials engineering. The structured electromagnetic fluctuations of a dark cavity environment can renormalize fundamental thermodynamical material properties and energy scales, holding promise to create a rich ecosystem of cavity-induced ground states and functionalities absent in the bare material. However, direct experimental demonstrations that cavity coupling can stabilize or enhance genuinely new phases of matter have remained scarce. In this work, we establish the presence of cavity-induced and cavity-enhanced ferroelectric phases in free-standing SrTiO$ _3$ membranes coupled to dark THz-frequency photonic crystal cavities. Using THz spectroscopy, we observe ultrastrong coupling (USC) between the ferroelectric soft mode in SrTiO$ _3$ and the cavity resonance. The structural response of SrTiO$ _3$ to this USC is measured via second harmonic generation imaging, which reveals a substantial (greater than 400%) enhancement of signal in the cavity environment and a distinct modification of the crystalline symmetry, indicating the onset and enhancement of ferroelectricity. We interpret these observations as resulting from renormalized piezoelectric and flexoelectric couplings, which in turn arise from the cavity-modified dielectric environment. This interpretation is supported with microscopic modeling via DFT-based multi-scale dynamics simulations and by macroscopic Ginzburg-Landau theory. Altogether, our experimental and theoretical results firmly confirm that cavity engineering can indeed be used to create new ground states in materials and enhance existing ones. This work establishes a new paradigm for materials engineering with direct applications for quantum transduction, quantum sensing, and nonlinear integrated photonics.
Materials Science (cond-mat.mtrl-sci)
Moiré metals and continuum models beyond a single valley
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Matthew Albert, Andrew Klekovkin-Hardy, Valentin Crépel
We derive continuum models of moiré materials valid over the full monolayer Brillouin zone, as required for metals whose large Fermi surfaces are not confined to a single valley. To this end, we introduce an environment-resolved two-center approximation, in which each hopping amplitude depends not only on the distance between the orbitals it connects but also on its position within the moiré cell. Taking the local environment to be set by the disregistry of the two layers alone, these moiré couplings and their full set of harmonics can be learnt from commensurate bilayers at uniform stackings, without fitting. The method shows excellent agreement with ab initio band structures on moiré cells containing a few hundred atoms. Applied to twisted NbSe$ _2$ , it yields a continuum model in which moiré effects concentrate at the van Hove singularities, a single-particle starting point for studying moiré-tuned superconducting, charge-density-wave instabilities and their competition.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
16 pages, 10 figures
Gapless and Non-Equilibrium Topology in Blockaded Ladders
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Ramanjit Sohal, Hannes Bernien, Ruben Verresen
We propose a multi-leg PXYP model as a minimal setting to explore constraint-induced intertwinement between itinerant and internal degrees of freedom. We argue that the Rydberg-like blockade induces correlations in squeezed space, providing a unified mechanism for nontrivial string order both in and out of equilibrium. In a two-leg geometry, this leads to an intrinsically gapless topological ground state, which can terminate at a supersymmetric multicritical point. This mechanism also leads to the preservation of string order for parametrically long times after a quench, which we verify using tensor network simulations and a classical stochastic approximation to the dynamics. In a three-leg geometry, the blockade leads to an additional emergent $ U(1)$ symmetry, resulting in a multicomponent Luttinger liquid where both itinerant and internal degrees of freedom are critical. This family of models arises naturally in a range of quantum simulator platforms such as Rydberg tweezer arrays and dipolar atoms in optical lattices.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Gases (cond-mat.quant-gas), Atomic Physics (physics.atom-ph), Quantum Physics (quant-ph)
5+8 pages; 5 figures
Singlet-Triplet Transition of Rotating Moiré Atoms in a Magnetic Field
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Conor Smith, Yubo Yang, Shiwei Zhang, Miguel A. Morales
Moiré superlattices can bind several electrons to each potential minimum, forming few-electron “moiré atoms.” Using neural quantum states that obey magnetic periodic boundary conditions, include full Landau-level mixing, and treat both spin sectors, we map the ground state of two-electron moiré atoms in a superlattice as a function of moiré depth and magnetic field strength. At strong field each atom is a spin-triplet maximum-density droplet with canonical angular momentum $ \langle L_z\rangle=-1$ and a persistent circulating current: the rotating counterpart of the “Wigner molecular crystal” recently imaged in moiré superlattices. Deepening the wells drives a singlet-triplet transition to non-rotating spin-singlet atoms whose only current is a weak diamagnetic counter-circulation. The transition moves to deeper wells as the field grows, so depth and field together open a window for the formation of rotors. This is the collective analog of the singlet-triplet transition of two-electron quantum dots. At the transition, the orbital magnetic moments of the atoms reverse sign as their spin polarization switches, a joint signature accessible to magnetometry. If the atoms are instead polarized by other means, such as magnetic proximity coupling, the rotors lock at weak field into a spontaneously ordered crystal of dimers in a pinwheel pattern.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Anisotropic spin splitting in $α$-MnTe epilayers on InP(111)A and Si(111) substrates
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Zofia Kopacz-Maj, Ali Akbar, Aleksandr Kazakov, Bartłomiej Turowski, Wojciech Zaleszczyk, Marta Aleszkiewicz, Tomasz Wojciechowski, Rafał Kurleto, Dawid Wutke, Natalia Olszowska, Tomasz Wojtowicz, Valentine V. Volobuev
$ \alpha$ -MnTe has emerged as a prototypical altermagnetic material, combining compensated antiferromagnetic order with momentum-dependent spin splitting. Here, we investigate the structural and electronic properties of epitaxial $ \alpha$ -MnTe layers grown by molecular beam epitaxy on InP(111)A and Si(111) substrates. The crystalline and surface quality of the epilayers was characterised by reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), and X-ray diffraction (XRD), confirming the formation of high-quality, single-phase films. The transport measurements were performed, confirming an antiferromagnetic transition and weak ferromagnetism. The electronic structure was studied using angle-resolved photoemission spectroscopy (ARPES). At 90 K, both samples exhibit relativistic anisotropic valence band splitting, which is substantially larger along the $ \Gamma$ -K direction, reaching approximately 300 meV, than along $ \Gamma$ -M, where values of about 150~meV are observed. The magnitude and momentum dependence of the splitting are very similar for $ \alpha$ -MnTe grown on the two different substrates, indicating the robustness of the altermagnetic electronic structure with respect to the epitaxial environment.
Materials Science (cond-mat.mtrl-sci)
12 pages, 6 figures
Theory of Convective Diffusion
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Žiga Krajnik, Takato Yoshimura, Alvise Bastianello, Enej Ilievski
We obtain a hydrodynamic theory of diffusive-scale dynamics in one-dimensional systems with interacting sound modes in the absence of self-interactions. Chaotic systems generically feature three distinct Gaussian relaxation processes: besides normal diffusion, driven by microscopic noise stemming from fast-decaying non-hydrodynamic modes, collisions between sound modes lead to two additional channels: convective diffusion manifesting as an effective multiplicative temporal noise, and an effective additive noise generated by the surrounding hydrodynamic modes. Our theory also includes, as a subclass, integrable systems described by generalized hydrodynamics, representing a pure realization of convective diffusion. Focusing on convective diffusion, we obtain an exact closed-form expression for the higher-point dynamical correlation functions and contrast their structure with those of normal diffusion. Additionally, we show that in convective diffusion each sound mode features a universal non-Gaussian distribution of charge transfer in its comoving frame, thereby establishing anomalous fluctuations as a characteristic feature of diffusive-scale dynamics in integrable systems.
Statistical Mechanics (cond-mat.stat-mech)
Quantum Monte-Carlo study of spin-valley ferromagnetism in rhombohedral graphene
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Michael Demos, Dongqi Li, Mainak Das, Tobias M. R. Wolf, Chunli Huang
Recent capacitance measurements in bilayer and trilayer rhombohedral graphene reported large magnetic entropy above the Curie temperature, suggesting the formation of fluctuating local moments. Further experimental support comes from scanning tunneling microscopy experiments in rhombohedral hexalayer graphene, which directly visualized honeycomb electron-crystal order that strengthens upon heating before melting, related to the Pomeranchuk effect. Motivated by these experiments, we construct spin-valley local-moment Hamiltonians for the quarter-metal and half-metal phases. We extract their couplings from constrained Hartree-Fock calculations, and solve their finite-temperature thermodynamics with stochastic-series-expansion quantum Monte Carlo. For the quarter metal we find a continuous 2D-Ising transition at $ T_c \approx 0.7$ K, an order of magnitude smaller than the Hartree-Fock estimate (~30 K) and closer to the experimental scale of a few kelvin. For the half metal, we study the field-induced magnetization as a function of temperature with and without proximity-enhanced spin-orbit coupling. When spin-orbit coupling is negligible, intervalley Hund’s coupling enhances the magnetic response. Strong spin-orbit coupling, as can be induced by a neighboring transition-metal dichalcogenide, gives rise to the standard spin-canted ground state at zero temperature. Upon heating, the in-plane polarization decreases more rapidly than the out-of-plane polarization. Surprisingly, despite the itinerant nature of the electrons, local-moment models with microscopically determined couplings appear to capture key finite-temperature magnetic properties of rhombohedral graphene without any fitting.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 5 figures, plus 8 pages of appendices with 4 figures. Comments are welcome
Intertwined ferromagnetic and altermagnetic orders in Cr-doped MnTe
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Jonathan M. DeStefano, Yaofeng Xie, Guodong Ren, Mai Nguyen, Yue Sun, Xiaodong Xu, Juan Carlos Idrobo, Jiun-Haw Chu
Ferromagnetism and altermagnetism both break time-reversal symmetry, yet their distinct transformation properties under crystalline symmetries forbid direct bilinear coupling between their order parameters. Whether these two magnetic orders can remain thermodynamically distinct while strongly influencing one another remains an open question. Here we demonstrate the homogeneous coexistence of ferromagnetism and altermagnetism in Cr-doped MnTe. By tuning the ferromagnetic ordering temperature across the nearly unchanged Néel temperature with Cr doping, we uncover a striking interplay between the two orders: the ferromagnetic transition becomes a crossover when altermagnetism develops first, whereas the onset of altermagnetism strongly suppresses the out-of-plane ferromagnetic remanence when ferromagnetism develops first. Moreover, spin-orbit coupling enables symmetry-selective interactions through which the ferromagnetic moment controls the altermagnetic domain manifold, with its out-of-plane and in-plane components biasing the time-reversal ($ Z_2$ ) and orientational ($ Z_3$ ) sectors, respectively. Our results reveal how two symmetry-distinct magnetic orders can retain separate ordering tendencies while remaining strongly coupled, providing a route towards internal control of altermagnetic domain states.
Materials Science (cond-mat.mtrl-sci)
Subsonic terahertz plasmon instability in space-time plasmonic crystals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
H. Terças, J. L. Figueiredo, P. Cosme
We investigate collective plasma-wave dynamics in a two-dimensional electron fluid subected to a travelling periodic modulation of the effective plasma velocity. Using a hydrodynamic description combined with Floquet-Bloch theory, we show that the travelling modulation acts as a moving plasmonic crystal whose band structure is governed by an effective drift velocity in the comoving frame. We demonstrate that the closure of the Bragg gap at the edge of the Brillouin zone gives rise to an exceptional point and triggers a Krein-type instability through the coupling of positive- and negative-energy modes. Analytical expressions are derived for the instability threshold and growth rate, revealing that self-amplification can occur even when the electron drift remains subsonic in the laboratory frame. Numerical simulations of the nonlinear hydrodynamic equations confirm the theoretical predictions and show the evolution towards a saturated regime dominated by a coherent Floquet-Bloch mode. These results identify travelling plasmonic crystals as a novel platform for wave amplification and non-Hermitian band dynamics in electronic fluids.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Quantum Gases (cond-mat.quant-gas), Plasma Physics (physics.plasm-ph)
Space-time crystals, Plasmonic crystals, Floquet bands, plasma instabilities, THz radiation
Triplon thermal Hall response in a honeycomb-lattice $J_1$-$J_2$ Heisenberg antiferromagnet with Dzyaloshinskii–Moriya interactions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Guilherme F. Figueiredo, E. Miranda, R. L. Doretto
We investigate triplon topology and the thermal Hall transport in a columnar valence-bond solid of a spin-$ 1/2$ honeycomb-lattice $ J_1$ -$ J_2$ Heisenberg antiferromagnet. Inequivalent triangular sublattices, modeled by $ J_2^A\neq J_2^B$ , remove inversion symmetry at nearest-neighbor bond centers and allow in-plane Dzyaloshinskii–Moriya (DM) interactions. We identify the two symmetry-allowed in-plane DM vector patterns and present detailed results for the pattern parallel to the bonds including an out-of-plane magnetic field. Within a harmonic bond-operator treatment, we determine the triplon bands, their Berry curvatures and Chern numbers, and the triplon thermal Hall conductivity. The DM interaction and magnetic field generate nonzero Berry curvatures, but the numerically integrated Chern number of every isolated triplon band vanishes. Nevertheless, the energy-dependent Bose weighting of positive and negative Berry-curvature regions produces a finite thermal Hall response at nonzero low temperatures. We delimit the dilute-triplon regime in which the harmonic transport calculation is expected to be reliable. These results show that a vanishing Chern number band does not directly constrain the triplon response of a valence-bond solid. We also comment on the effects on the columnar valence-bond solid phase of a DM interaction between next-nearest-neighbor spins characterized by an out-of-plane vector pattern.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech)
21 pages, 10 figures
Nonlinear visco-elasto-plastic model for the stress-strain and stress-relaxation in metallic glass
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-11-02 20:00 EST
Ankit Singh, Alessio Zaccone, Oleg Gendelman, Valeriy V. Ginzburg
We develop a nonlinear visco-elasto-plastic (VEP) model for the stress-strain response of metallic glasses by connecting the deformation dynamics with the material relaxation time obtained from independent stress-relaxation measurements. The material is modeled as a Maxwell-type element, with a nonlinear elastic spring and a stretched-exponential dashpot whose behavior is determined from the separate stress-relaxation data. The model captures the effects of temperature and strain rate on the initial elastic response, stress overshoot, post-yield softening, and steady flow. We independently determine the reference material-time function $ X_0(\varepsilon)$ from the stress-relaxation response and the nonlinear material-time variable $ X(\varepsilon)$ from the elastic-viscoplastic strain decomposition based on the stress-strain response. We introduce an Eyring-type function or material-time ratio $ \phi(\varepsilon)=X(\varepsilon)/X_0(\varepsilon)$ which quantifies the change of relaxation dynamics during nonlinear deformation. Our model provides a simple connection between structural relaxation and yielding in metallic glasses.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Fluid Dynamics (physics.flu-dyn)
9 pages, 4 figures, and 1 table
Efficient Simulation of Gate Leakage Currents in Ultra-scaled Transistors from First Principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Mauro Dossena, Nicolas Vetsch, Alexander Maeder, Anders Winka, Vincent Maillou, Denghui Lu, Alexandros Nikolaos Ziogas, Jiang Cao, Mathieu Luisier
To ensure high electrostatic integrity in ultra-scaled field-effect transistors (FETs), thin gate dielectric layers are typically needed, potentially giving rise to (strong) leakage currents. Being able to model this effect is therefore crucial. Here, we show how gate leakage currents can be computed at the ab initio level in WS$ _2$ -hBN FETs by extending the well-established quantum transmitting boundary method (QTBM). Two main challenges are tackled: (i) the calculation of the open boundary conditions (OBCs) for the gate contacts and (ii) the solution of the resulting sparse linear system of equations A x = b where the matrix A possesses an unstructured sparsity pattern. We demonstrate that the proposed method outperforms the state of the art and can be readily applied to simulate transistors with gate lengths exceeding 25 nm.
Materials Science (cond-mat.mtrl-sci)
Spherical law for optimal layouts of random graphs
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-11-02 20:00 EST
Jakob Stubenrauch, Christian Keup
Can the nodes of a random graph be placed in an auxiliary space $ \mathbb{R}^{M}$ so that its connectivity becomes local? The spring electric layout is a standard algorithm to try to find such local graph layouts; we study it as a statistical-physics problem by considering the Gibbs ensemble of spring-electric layouts. For graphs with independent edges we solve the model exactly at large number of nodes $ N$ and fixed embedding dimension $ M$ . The node positions obey a spherical law: they are uniformly distributed in an $ M$ -dimensional ball; for $ M=2$ this is closely related to Girko’s circular law. Crucially, the ground state energy is flat across all layouts with that density: an optimal layout for one graph is asymptotically optimal for any other. Optimal layouts of i.i.d. graphs are therefore frustrated liquids, macroscopically constrained but microscopically unoptimizable. We discuss relations to graph-partitioning, Laplacian eigenmaps, and dimensionality reduction, and outline how this harsh result breaks down for correlated graphs.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
Submission to SciPost
Temperature Evolution of Magnon-Polarons in the van der Waals Antiferromagnet FePS$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
A. Krajewska, J. Kierdaszuk, M. Dub, E. Karpierz-Marczewska, M. Potemski
Magnon polarons, hybrid excitations arising from magnon-phonon coupling, were investigated in the van der Waals antiferromagnet FePS3 using magneto-Raman scattering measurements at temperatures ranging from 4 K to the vicinity of the Néel temperature ($ T_\mathrm{N}$ = 118 K). The lower Zeeman-split component of the magnon-like mode, tuned by the magnetic field toward the lower-energy phonon mode, exhibits an avoided crossing. The corresponding magnetic field decreases from approximately 13 T at 4 K to 5.6 T at 85 K, bringing the effect within reach of a standard laboratory magnet. A model of three coupled bosonic modes shows that the magnon-phonon coupling constant, approximately 2.7 cm$ ^{-1}$ at low temperatures, decreases significantly with increasing temperature, following a trend similar to the temperature-induced softening of the magnon mode. This decrease in magnon-phonon coupling is discussed in terms of a possible reduction in sublattice magnetization due to thermal fluctuations.
Materials Science (cond-mat.mtrl-sci)
7 pages, 5 figures; Supplemental Material (2 pages, 1 figure) provided as an ancillary file
Exact Electron Dynamics in Linear and Chiral Cavities: Complete Field versus Single-Helicity Reduction
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Can a chiral cavity turn a free electron into a Landau-like orbiting particle? We answer with exact solutions of three quadratic electron–cavity models in the dipole limit, valid at arbitrary coupling. A single linearly polarized mode dresses the electron mass, which delays its flight, slows the spreading of a wavepacket and entangles the packet with the cavity. The complete transverse field, with both circular helicities, keeps two commuting, gapless translations at any coupling, mode number and helicity splitting, so the electron stays ballistic and no synthetic magnetic field appears. Keeping a single helicity gives two inequivalent models that are not related by a gauge transformation: reducing before the Power–Zienau–Woolley transformation gives ballistic motion, whereas reducing after it gives a Landau-like crossed-quadrature Hamiltonian. They differ by a real uniform field $ B=s\lambda^2/(2\omega_c)$ ($ \omega_c$ the mode frequency, $ \lambda$ the coupling, $ s=\pm1$ the helicity). In the complete theory the frequency $ \omega_{-s}$ of the partner helicity, measured against $ g^2=\lambda^2/(2\omega_c)$ , decides between them: the electron is ballistic for a stiff partner, and Landau-like only at the soft-partner point, through an exact canonical reorganization that holds for the active sector but not for observables such as the electron–photon entanglement. Projecting onto one helicity after the PZW transformation is therefore not by itself a mechanism for synthetic magnetism; the mode content of the cavity is.
Strongly Correlated Electrons (cond-mat.str-el), Chemical Physics (physics.chem-ph), Quantum Physics (quant-ph)
Electron-electron interactions mediated by overdamped vibrations: Implications for chirality-induced spin selectivity
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Leonardo Celada, Rocco Bellusci, D. K. Andrea Phan-Huu, Alessandro Chiesa, Stefano Carretta
Motivated by chirality-induced spin selectivity (CISS), we investigate spin polarization during molecular electron transfer through a correlated bridge in the presence of a rapidly relaxing Peierls mode. By modulating both electronic hopping and spin–orbit coupling, the mode mediates two-body spin-spin interactions, including isotropic, anisotropic, and Dzyaloshinskii-Moriya exchange. We derive these interactions using an exact Lang-Firsov transformation for a four-site chiral bridge. We then include fast vibrational relaxation in the joint electron–vibration master equation and derive the reduced electronic dynamics to second order in the vibronic coupling, retaining both coherent and dissipative contributions and the finite-time buildup of the vibrational response. We test our derivation by numerical simulations, finding spin polarization accumulated at the acceptor after unpolarized injection, with nonmonotonic dependence on damping and bridge filling. Within the postulated local-loss model, our results show that rapid vibrational relaxation does not preclude spin polarization through a correlated bridge and provide a framework for assessing vibration-mediated interactions and dissipative dynamics as ingredients of CISS in molecular electron transfer.
Strongly Correlated Electrons (cond-mat.str-el)
Tunable Three-Body Interactions in Microwave-Shielded Polar Molecules
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-11-02 20:00 EST
We show that microwave shielding, which enables collisionally stable ultracold polar molecules, also leads to genuine nonadditive three-body interactions comparable to the shielding interaction itself. Their magnitude, sign, and geometrical dependence can be flexibly controlled through microwave parameters and orientation. Interaction strengths can reach the ten kilohertz-scale for ultrapolar molecules in typical optical lattices. The nonadditive three-body interactions can stabilize novel many-body phases, and should be accounted for in quantum simulation with microwave shielded molecules.
Quantum Gases (cond-mat.quant-gas), Atomic Physics (physics.atom-ph), Chemical Physics (physics.chem-ph), Quantum Physics (quant-ph)
Chirality inversion and odd transport in a suspension of living rotors
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-11-02 20:00 EST
Isabelle Eisenmann, Pedro Cosme, Hannah van Sterkenburg, Hugo Franca, Titouan Seguy, Maria Tatulea-Codrean, Maziyar Jalaal
Chiral symmetry breaking is a defining feature of life, visible at all scales from molecules to organisms. Yet how microscopic chirality propagates to shape the macroscopic properties of living matter remains poorly understood. Here, using a new experimental system of spinning microalgae, we show that a living chiral fluid behaves fundamentally differently from an externally driven one. As their density increases, cells self-assemble hydrodynamically into small rotating clusters which merge into a percolating chiral fluid. Strikingly, microscopic and macroscopic vorticity have opposite signs: individual cells all spin clockwise, yet clusters orbit counterclockwise. Combining experiments, theory and simulations, we show that both chirality inversion and percolation are direct consequences of the cells’ internally driven nature. We then show how percolation reshapes transport, with even and odd diffusivities responding differently to the emerging network topology.
Soft Condensed Matter (cond-mat.soft), Fluid Dynamics (physics.flu-dyn)
10 kV $β$-Ga$_2$O$_3$ Sub-Bandgap Triggered Impurity Photoconductive Semiconductor Switches (i-PCSSs): Lessons for Optimal Design
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Imteaz Rahaman, Hunter Ellis, Afrouz Taherian, Seyedeh Shadi Mirmohammadi, Botong Li, Berardi Sensale Rodriguez, Michael A. Scarpulla, Kai Fu
$ \beta$ -Ga$ _2$ O$ _3$ photoconductive semiconductor switches (PCSSs) are attractive for high-voltage operation, but above-bandgap triggering requires deep-ultraviolet excitation. Here, we investigate a 650-um-thick, 0.01% Fe-doped $ \beta$ -Ga$ _2$ O$ _3$ impurity PCSS with a 5-mm lateral gap under continuous-wave (CW) 808-nm sub-bandgap excitation at biases up to 10 kV ( 20 kV cm^-1). The device exhibited clear sub-bandgap photoconductive switching. As the optical power density increased from 0.64 to 3.18 W cm^-2, the ON-state current increased progressively while the ON-state resistance decreased, consistent with enhanced defect-assisted photocarrier generation. A higher applied bias further strengthened the switching response through enhanced field-assisted carrier transport. The ON/OFF ratio increases with optical power density but exhibits a nonmonotonic bias dependence, reaching approximately 15-16 near 5-7 kV. At 10 kV, increased OFF-state conduction and non-ideal transient behavior reduce the switching contrast. These results demonstrate near-infrared photoconductive switching but also highlight critical trade-offs in photoconductive thresholds for impurity states.
Materials Science (cond-mat.mtrl-sci)
16 page; 5 Figures
The spin-transfer inverse Faraday effect in Au/YIG thin film bilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Victor H. Ortiz, Daniel Russell, Fengyuan Yang, Roland K. Kawakami
The inverse Faraday effect (IFE) (the generation of an effective magnetic field in a material upon irradiation with circularly polarized light) offers a pathway to ultrafast, non-thermal control of spin dynamics. In metallic/ferromagnetic-insulator (NM/FMI) bilayers, IFE-driven spin polarization in the metallic layer can be an alternative to generate magnon excitations in the magnetic insulator which otherwise would be inaccessible with photon energies below the insulator bandgap, but this avenue has remained mostly unexplored. In this work, we investigate the regime of spin-transfer via IFE in Au/YIG bilayers, by means of ultrafast time-resolved magneto-optical experiments. Understanding the mechanism of this spin-transfer IFE in these NM/FMI heterostructures is crucial for several reasons: it elucidates the fundamental coupling between light’s angular momentum and collective spin modes at buried interfaces, it enables all-optical generation and manipulation of pure spin currents, and it paves the way toward THz-frequency spintronic devices leveraging the insulator’s long magnon lifetimes.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
Minimal model of sticky collisions in modulated optical traps
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-11-02 20:00 EST
Hubert J. Jóźwiak, Tijs Karman
Collisional loss of ultracold bialkali molecules is predicted to occur through photo-excitation of collision complexes. However, recent measurements in modulated optical traps report an unexpected lack of excess survival, at odds with theoretical predictions and earlier experiments. We develop a minimal quantum scattering model that treats collisions as a coherent process occurring in the presence of the modulated trap. We demonstrate that quantum reflection from the long-range potential fundamentally alters loss dynamics, removing the tension between recent experiments and predicted sticking times. This framework provides new testable predictions such as a strong dependence on collision energy, initial molecular state, and long-range interactions, that are absent in the currently used phenomenological model.
Quantum Gases (cond-mat.quant-gas), Atomic Physics (physics.atom-ph)
8 pages, 5 figures
Unifying dynamical electron-electron and electron-phonon interactions from first principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Jae-Mo Lihm, Malte Rösner, Cyrus E. Dreyer, Massimiliano Stengel, Samuel Poncé
Electron-phonon interactions in materials with free carriers are dynamically screened by low-energy electronic excitations, yet first-principles calculations almost always treat this screening in the adiabatic approximation. A fully dynamical treatment of metals and doped semiconductors within time-dependent density functional perturbation theory (TDDFPT) is expensive and numerically delicate. Here, we introduce DFPT+A downfolding (“A” for active space), which starts from the static density functional perturbation theory (DFPT) response of a computationally convenient base system and adds the dynamical screening of a low-energy active space, described by Wannier functions. The required statically screened electron-electron interaction is computed using DFPT directly in the basis of Wannier-function pairs and truncated in a computationally efficient and systematically improvable way. The method handles entangled bands and accurately reproduces TDDFPT at a fraction of its cost. We use it to compute the total dynamical electron-electron interaction, including direct Coulomb and phonon-mediated interactions with dynamically screened electron-electron and electron-phonon couplings, all on equal footing. In hole-doped monolayer hBN, the hybridization of the carrier plasmon with the longitudinal optical phonon makes the low-energy retarded interaction nonmonotonic in the carrier density, an effect missed by the adiabatic approximation. In metallic monolayer TaS2, nonadiabatic effects are weak and occur only due to the intraband electron-hole continuum and the nesting of nearly parallel Fermi velocities. We also validate the widely used screened-screened approximation for the phonon spectral function. This work opens the way to first-principles studies of spectral functions, transport, and superconductivity with dynamically screened interactions.
Materials Science (cond-mat.mtrl-sci)
Anisotropic Boltzmann transport in a tight-binding superlattice: Exact results for power-law energy-dependent scattering
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
We develop a complete Boltzmann transport theory for the in-plane ($ \sigma_{xx}$ ) and out-of-plane ($ \sigma_{zz}$ ) conductivities of an electronic superlattice consisting of a periodic stack of two-dimensional (2D) parabolic-band layers coupled along the superlattice axis by nearest-neighbor tunneling $ t$ , in the physically relevant regime $ t\ll E_F$ where the Fermi surface is an open, corrugated cylinder. Within the relaxation-time approximation with a power-law energy-dependent scattering time $ \tau(E)\propto E^{p}$ , we study the seven models $ p=0,\pm1,\pm3/2,\pm2$ as functions of the 2D electron density $ n$ per layer and temperature $ T$ . For $ p=-2$ (in plane) and $ p\le -1$ (out of plane), long-lived carriers at the miniband bottom can dominate transport at finite temperature. For $ p=-2$ , these carriers produce a pronounced peak in $ \sigma_{zz}(T)$ at $ T\sim E_F$ . We find that the temperature dependence of the anisotropic metallic dc conductivity can be highly counterintuitive depending on $ t$ , $ T$ , and $ p$ , with no generic increase or decrease with temperature. The Lorenz ratio is determined by the energy variance of the current-carrying electrons; the Wiedemann-Franz (WF) law is exact as $ T\to0$ for all models at fixed $ t$ , with anisotropic corrections at finite temperature. Band-edge carriers first enhance the interlayer Lorenz ratio up to several times its low-temperature value through thermal occupation of separated energy ranges within the same electron band and then suppress it at high temperature by energy filtering. Strong violations of the Wiedemann-Franz law can therefore arise from miniband structure and energy-dependent elastic scattering alone.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
24 pages, 11 figures, 6 tables
Frustration-Induced $1/6$-Vortex-Paired Phase in a Kagome XY Model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Geometric frustration can fractionalize vortices in two-dimensional XY systems, but a given frustrated model usually hosts only a single type of fractional vortex. Here we study a kagome XY model in which an antiferromagnetic coupling $ J_1$ and a second-harmonic coupling $ K$ favor two competing frustrated ground-state manifolds. For $ K/J_1<1/9$ , the ground states map onto those of the kagome three-state Potts antiferromagnet and support $ 1/3$ vortices; for $ K/J_1>1/9$ , they map onto those of the kagome Ising antiferromagnet and support $ 1/2$ vortices. At $ K/J_1=1/9$ , the two manifolds become degenerate, and bends in the domain walls between them carry $ 1/6$ -vortex excitations. Tensor-network calculations show that a finite-temperature phase with quasi-long-range order only in $ e^{6i\theta}$ emerges from this degenerate point, separating the $ 1/3$ - and $ 1/2$ -vortex-paired phases. This $ 1/6$ -vortex-paired phase has no counterpart in either parent manifold, showing that competing frustrated manifolds provide a route to new fractional-vortex-paired phases.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Superconductivity (cond-mat.supr-con)
16 pages, 11 figures, including Supplemental Material
ORCHID: Connecting Finite-Temperature Thermodynamic Evidence to Computational Materials Discovery
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Raymundo Arróyave, James E. Saal, Dongwon Shin
Finite-temperature phase stability is essential to materials discovery, but the evidence needed to describe it remains scattered across decades of literature. ORCHID organizes this evidence around the thermodynamic states that the observations describe, using tiered agentic extraction guided by thermodynamic rules, expert supervision and explicit validation. The collection contains 73,542 values from 1,321 papers, represented with their thermodynamic states, phase identities, provenance, evidence classes and uncertainty, together with assessed phase assemblages and calculated references. A qualified subset is released in ESPEI-compatible form for CALPHAD assessment, and machine-readable access supports both human and AI-assisted reuse. Blind expert evaluation of 48 diagram fields gives 93.8% agreement, increasing to 97.9% after accounting for notation conventions. On a common formation-enthalpy benchmark, eight MLIPs show residual spreads close to their DFT reference, motivating evaluation of finite-temperature phase stability through PhaseForge. One-shot MLIP-PhaseForge descriptions of Cu-Zr recover 0.35-0.56 of observed phase occurrences at assessed field points. ORCHID-assisted refinement through PhaseForge+ recovers 9 of 13 invariant temperatures within 2 sigma and reduces held-out activity error from 5.1 to 1.7 kJ/mol. By supplying interpreted literature evidence directly to gradient-based refinement through PhaseForge+, ORCHID connects evidence recovery to programmatic CALPHAD assessment. With the initial description and fitting datasets prepared, the final Cu-Zr refinement completes in approximately 27 minutes, providing a foundation for continuously updated thermodynamic models and their use in materials discovery.
Materials Science (cond-mat.mtrl-sci)
67 pages including two supplementary sections (methods; repository and access). Data: ORCHID v2026.10, this https URL ; project and documentation: this https URL
Quantum-Geometric Subgap Second-Harmonic Generation in PT-Symmetric Antiferromagnetic Insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Although quantum geometry plays an established role in electronic transport and optical responses, the contribution of the time-reversal-odd Riemannian connection to fully subgap responses remains less explored. Here we identify intrinsic second-harmonic generation in PT-symmetric antiferromagnets, predominantly governed by the real sector of the interband Hermitian connection and arising entirely from virtual interband transitions. In bilayer MnBi$ _2$ Te$ _4$ , the response persists in trivial phases but is enhanced in the layer-Chern phase and reverses sign with Néel order, offering a probe of quantum geometry and phase-sensitive readout of antiferromagnetic order without mobile carriers or real excitations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
7 pages, 4 figures; Supplemental Material: 15 pages, 3 figures
Faster-than-power-law decay of order parameter correlations in the two-dimensional RP$^2$ model: a rigorous result by vibe-proving
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
We consider the RP$ ^2$ model on the two-dimensional square lattice with nearest-neighbor interactions. It is obtained by replacing the spin in the standard classical Heisenberg model with a director, which does not distinguish two opposite directions. Unlike the standard classical Heisenberg model or the O(3) nonlinear sigma model, the RP$ ^2$ (and its cousin RP$ ^3$ ) model allows point vortex defects classified by $ \pi_1(RP^2)= Z_2$ in two dimensions. It is tempting to expect the $ Z_2$ vortices to induce a phase transition analogous to the well-established Berezinskii-Kosterlitz-Thouless transition in the O(2) model (XY model) in two dimensions. Indeed, the possibilities of a critical phase or a critical point with power-law correlations of the order parameter in the RP$ ^2$ and RP$ ^3$ models have been discussed in the literature. However, the challenging nature of the problem has prevented a definitive conclusion on the phase diagram so far. In this paper, we report a rigorous mathematical proof by Artificial Intelligence (ChatGPT 6 Astra) that the absolute value of the two-point correlation function of order parameters at distance $ r$ in the RP$ ^2$ and RP$ ^3$ models on the two-dimensional square lattice is bounded above by $ C_\beta \exp{(-c_\beta[\log(2+r)]^2)}$ for any finite inverse temperature $ \beta\ge0$ , with positive constants $ C_\beta$ and $ c_\beta$ depending only on $ \beta$ . Namely, the correlation function decays faster than any power of $ r$ . The proof is formalized and verified in Lean; the formalization is publicly available at doi:https://doi.org/10.5281/zenodo.23548847 . A heuristic argument based on a one-parameter effective theory ansatz at large distances combined with the rigorous correlation bound suggests (but does not prove) that the $ Z_2$ vortices are always unbound at any nonzero temperature.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Lattice (hep-lat), Mathematical Physics (math-ph)
35 pages, no figures
Berry curvature quadrupole induced third-order anomalous Hall effect in altermagnetic $\mathrm{KV_2Se_2O}$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Jiacheng Yao, Zhuocheng Lu, Zhichao Guo, Hua Wang
Altermagnets combine compensated magnetic order with momentum-dependent spin splitting, providing a symmetry-rich platform for exploring nonlinear quantum-geometric transport. In the d-wave altermagnet considered here, the antiunitary symmetry operation $ TC_{4z}$ enforces a vanishing momentum-integrated Berry curvature, while inversion symmetry forbids a finite Berry-curvature dipole. Consequently, the Berry curvature quadrupole (BCQ) can provide a contribution to the nonlinear Hall response, scaling as $ \tau^2$ , where $ \tau$ denotes the relaxation time. We derive a gauge-covariant Wannier interpolation formula that enables efficient evaluation of the BCQ directly from first-principles Wannier tight-binding Hamiltonians. Applying this framework to $ \mathrm{KV_2Se_2O}$ , we calculate the momentum-space distribution of the BCQ and the associated chemical potential dependent nonlinear conductivity. The momentum-resolved analysis reveals that the dominant contribution originates from spin-orbit coupling induced avoided arossings, directly linking the gap structure to the sign-changing nonlinear response. Our work establishes a general first-principles route to higher-order quantum-geometric responses in altermagnets, opening avenues for exploring nonlinear Hall effects in next-generation spintronic and magnetoelectronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 3 figures
Coordination three heals, coordination four is hard: the antiferromagnetic Potts model with a costly third state
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Jeehoon Choi, Suhwan Yoo, Chaeyeon Kim, Hee Young Kwon, Changyeon Won
We study the ground states of the antiferromagnetic three-state Potts model in which the third state carries a single-ion energy cost $ D_3$ , on arbitrary lattices, and show that the difficulty of the ground-state problem is controlled by the maximum coordination $ \Delta$ alone; on planar lattices with $ \Delta\le5$ it is classified completely. On lattices with coordination at most three the third state heals frustrated bonds one for one: every graph of maximum degree three other than $ K_4$ has an independent set of sites that meets every odd cycle and whose size equals the number $ \operatorname{fr}$ of frustrated bonds of the Ising ground state. This identity also follows from known results on the chromatic vertex stability of graphs; we give a constructive proof. Hence $ E_0 (D_3)=\min(D_3,1) \operatorname{fr}$ for all $ D_3$ , computable in polynomial time on planar lattices. In graph-theoretic terms, independent odd cycle transversal is solvable in polynomial time on planar subcubic graphs. On planar lattices with maximum coordination four, in contrast, deciding the ground-state energy is NP-complete for every fixed $ 0\le D_3<2$ and polynomial for $ D_3\ge2$ . The boundary is set by a local principle: a site of coordination $ d$ in the third state relieves at most $ \lfloor d/2\rfloor$ frustrated bonds, so the third state is useless once $ D_3\ge\lfloor\Delta/2\rfloor$ ; this threshold is sharp for every $ \Delta\ge3$ and reproduces the triangular-lattice point $ D_3^\ast=3$ of the equivalent spin-1 Blume–Capel antiferromagnet. From a single Ising ground state the proof builds an exact ground state in polynomial time, which for quasicrystalline, foam-like and defective lattices with thousands of sites takes seconds to minutes.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph)
Quantifying Blinking Suppression and Probing Its Mechanism in PPD-Treated Single Quantum Dots
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Eduard A. Podshivaylov, Egor B. Kurgin, Changgang Yang, Guofeng Zhang, Pavel A. Frantsuzov
Colloidal semiconductor quantum dots (QDs) are highly promising materials for various applications, yet photoluminescence intermittency (blinking) remains a key obstacle to their practical use. While recent advances have enabled partial or complete suppression of this effect, both the degree of suppression and the mechanism by which it occurs are often difficult to establish. In the present work we analyse the blinking suppression of single CdSe/ZnS QDs after treatment with p-phenylenediamine (PPD), recently discovered by Yang et al. We revisit the blinking mechanism in this system and show that it is governed predominantly by the trapping mechanism, rather than by Auger ionization as previously proposed. For data analysis we apply a threshold-free two-dimensional criterion recently proposed by Podshivaylov and Frantsuzov. The criterion is based on the relative quantum yield estimator $ \langle \hat{Q} \rangle^{(s)}$ and the decay-rate fluctuation parameter $ \hat{\xi}$ . We found that PPD treatment significantly increases the relative quantum yield and leads to only a modest increase in $ \hat{\xi}$ , indicating that the dominant effect of PPD is to shift the distribution of the non-radiative recombination rate toward lower values, rather than to eliminate its fluctuations. We further suggest a number of possible mechanisms of PPD-induced suppression and propose critical experiments for their verification.
Statistical Mechanics (cond-mat.stat-mech), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages, 7 figures
Only the immortal can (almost) flock while turning: Two-dimensional chiral immortal flocks, time crystals and non-universal sub-logarithmic roughness
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Sudip Mukherjee, Abhik Basu, Leiming Chen, John Toner
We study two-dimensional chiral dry'' (non-momentum conserving) immortal’’ (number conserving) flocks'' (polar ordered active fluids). Noise driven fluctuations about the noise-free time crystal’’ state, in which the velocity rotates uniformly in time, obey coupled Kardar-Parisi-Zhang-like equations for the local velocity orientation and a conserved concentration field; the latter field stabilizes order. Orientational fluctuations grow only sub-logarithmically, and number fluctuations are suppressed (``hyperuniform’’); both exhibit nonuniversal scaling exponents. There are three different universality classes of disordering transitions.
Statistical Mechanics (cond-mat.stat-mech)
8 pages, 4 figures
Agentic Global Optimization of Site-Disordered Crystalline Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Martin Hoffmann Petersen, Zekun Ren, Kedar Hippalgaonkar
Site-disordered crystals, in which several elements partially occupy the same atomic site, cannot be simulated atomistically without first resolving an explicit ordering, and the number of possible orderings grows combinatorially with supercell size. Because each candidate requires an expensive structural relaxation, locating the global-minimum ordering is a costly combinatorial search. Here, we present an agentic search in which a surrogate model, fitted to previously evaluated configurations, selects each subsequent candidate by balancing exploitation, uncertainty, and novelty. Four surrogates are implemented within a shared framework: an ExtraTrees ensemble, Bayesian ridge regression, sparse ARD regression, and an ALiEGNN-inspired graph ensemble. These are benchmarked against three traditional methods: random walk, Markov chain Monte Carlo, and a genetic algorithm across 14 test cases spanning 12 crystal structures, with exhaustively enumerated global minima as ground truth. The agentic surrogates reach the global minimum in 94% of runs, compared with 55% for the traditional methods, with a median 4.3-fold reduction in evaluations relative to the best traditional method. Bayesian ridge regression succeeds in all runs with the fewest evaluations. Applied to Na2/3FePO4, with coupled Na/vacancy configurational disorder and Fe2+/Fe3+ charge disorder, the framework recovers the experimentally reported ordering when charge states are encoded in the surrogate representation, demonstrating its extension to multi-sublattice disorder.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech)
Airy distribution of the quenched spectral form factor in non-interacting fermions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Oscar Martin, Satya N. Majumdar, Laura Foini
For chaotic many-body systems as well as the random energy model, the logarithm of the (scaled) spectral form factor (SFF) exhibits two robust properties at late times: (i) self-averaging and (ii) a reflected-Gumbel distribution. Here, we demonstrate that both properties break down for $ N$ non-interacting fermions on a lattice of size $ L$ with an incommensurate single-particle spectrum. We show that the logarithm of the SFF, upon rescaling by $ 1/\sqrt{L}$ , follows the Airy distribution, in stark contrast to the reflected-Gumbel law. Moreover, it is no longer self-averaging, as its mean and standard deviation are of the same order. While deviations from reflected-Gumbel statistics are generically expected for non-interacting systems, we find that an interacting integrable model exhibits reflected-Gumbel statistics at late times, mirroring the chaotic case and distinguishing it from non-interacting fermions.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn)
5 pages
Multiband-Induced Complex Magnetotransport in the Kagome Metal LuNb$_6$Sn$_6$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Hongye Zhang, Xingyu Ma, Ying Zhu, Jingyang Zhu, Andreas Eich, Yuan Tang, Xiong Wang, Ningxi Yang, Aifeng Wang, Yisheng Chai, Xinrun Mi, Michael Merz, Quansheng Wu, Mingquan He
We report the electrical transport properties of the kagome metal LuNb$ _6$ Sn$ 6$ , which undergoes a charge density wave (CDW) transition at $ T\mathrm{CDW}\approx80$ K. Similar to the kagome metals $ A$ V$ _3$ Sb$ _5$ ($ A$ = K, Rb, Cs), LuNb$ _6$ Sn$ 6$ develops complex magnetotransport behavior near and below the CDW transition. In particular, the longitudinal magnetoconductivity exhibits an approximately linear field dependence below about 1 T, whereas the field dependence of Hall conductivity displays pronounced nonlinearity and a field-induced sign reversal. Although an anomalous Hall-like contribution can be extracted by subtracting a local background from the Hall conductivity, mobility-spectrum analysis shows that the overall magnetotransport can be largely accounted for by multiband conduction involving high-mobility electronlike and holelike carriers. Nevertheless, sizable deviations from the multiband model emerge near $ T{\mathrm{CDW}}$ , pointing to additional CDW-related scattering processes. These results demonstrate that high-mobility multiband transport, together with CDW-induced modifications of carrier scattering, play important roles in the complex magnetotransport of LuNb$ _6$ Sn$ _6$ .
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
12 pages, 5 figures
Spin-conserving and spin-flip magnetic scattering in the altermagnetic spin-splitter effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Critical magnetic fluctuations scatter electrons strongly near an ordering transition, but they barely degrade the charge current, because they scatter mostly through small angles. In an altermagnet the electric field also drives a spin current, and a nearly forward spin flip moves an electron to the other spin band at almost unchanged velocity. We develop a Boltzmann theory of the spin splitter ratio that keeps the full collision operator of quasistatic magnetic fluctuations and its change with the magnetic order. Fluctuations of equal total strength give the same resistivity for every fraction of spin flips, yet they can move the spin splitter ratio in opposite directions. Spin conserving fluctuations relax the spin current at about the charge relaxation rate, whereas forward flips equalize the two spin populations at equal energy at the quasiparticle rate, which in two dimensions grows linearly with the correlation length. Energy conservation on the split bands protects the part of the spin current carried by the band shift of the occupied states at every scattering strength, and the splitting blocks forward flips once the spin Fermi lines lie farther apart than the inverse correlation length. When flips dominate, a quarter to a half of the lattice band ratio survives. The transport time approximation reproduces the initial growth of the resistivity but recovers only a quarter to a half of the initial fall of the ratio, and a disorder series at fixed reduced temperature measures this fall independent of the order amplitude.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Spin conservation protects the altermagnetic spin-splitter current from critical scattering
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Near a magnetic transition, critical fluctuations scatter electrons strongly, but the charge current survives, because long wavelength fluctuations barely turn the electron velocity. In an altermagnet the electric field also drives a spin current, the spin splitter effect, and a nearly forward scattering event that flips spin moves an electron to the other spin band at almost unchanged velocity. We show that the spin current shares the protection of the charge current only when the fluctuations conserve spin. Solving the Boltzmann equation with the full collision operator, including its change with the magnetic order, we find that forward flips equalize the two spin populations at equal energy at the quasiparticle rate, which in two dimensions grows linearly with the correlation length, whereas spin conserving fluctuations relax the spin current at a rate comparable to the charge relaxation rate. Fluctuations with the same resistivity can thus move the spin splitter ratio in opposite directions. Energy conservation protects the part of the spin current that follows the band shift of the occupied states, and the splitting blocks forward flips once the spin Fermi lines lie farther apart than the inverse correlation length. A disorder series at fixed reduced temperature measures the initial fall of the ratio with the magnetic resistivity independent of the order amplitude, and the growth of this slope toward the transition identifies spin flip critical fluctuations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
An internal mode shifts the depinning threshold of dissociated dislocations without changing universality
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Mikko J. Alava, Tero J. Mäkinen
Driven elastic manifolds exhibit a depinning transition whose large-scale behavior is governed by a nonequilibrium critical fixed point. Real interfaces, however, often possess internal degrees of freedom, raising the question of whether such modes alter depinning universality or only nonuniversal properties of the transition. We address this question for a dissociated dislocation, whose two Shockley partials define a fluctuating stacking-fault width driven by correlated random-alloy stresses. Comparing exact thresholds on identical disorder realizations with the width either free or frozen, we find that width fluctuations leave the depinning universality class unchanged: the roughness exponent $ \zeta$ and correlation-length exponent $ \nu$ remain the same even when the width becomes strongly fluctuating and locally multistable. The threshold, however, shifts. The shift is governed by the elastic crossover length of the internal mode rather than by multistability, and can have either sign. An infinite-range mean-field treatment misses this mechanism. With the physical two-partial elastic kernel and disorder calibrated against measured strengths, width fluctuations raise the athermal critical resolved shear stress by 10-35% over that of a rigid dissociated dislocation. An internal mode can thus be irrelevant at the depinning fixed point while remaining quantitatively important for where the transition occurs.
Statistical Mechanics (cond-mat.stat-mech), Materials Science (cond-mat.mtrl-sci)
Strong-Field-Driven Non-Linear Vibronic Coupling in an Asymmetric Donor-Acceptor Oligomer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Jannik Theile, Michele Guerrini, Caterina Cocchi
Understanding how nuclear motion couples to intramolecular charge transfer beyond the perturbative regime of light–matter interaction remains an open problem. We tackle this problem by investigating the electron-nuclear response of an acceptor-donor-acceptor oligomer with structural asymmetry due to the partial fluorination of an acceptor unit. Adopting real-time time-dependent density functional theory combined with Ehrenfest dynamics, we excite the systems with a resonant pulse of varying intensity, spanning the weak-, intermediate-, and strong-coupling regimes. When nuclei are clamped, field-driven charge preferentially flows from the donor to the fluorinated acceptor, with selectivity reduced upon increasing intensity. With moving ions, the early-time spatial response remains qualitatively unchanged, despite a distinct, spatially asymmetric charge redistribution. In the strong-field regime, nuclear motion preserves the preference for field-driven charge accumulation on the fluorinated acceptor, although the process takes approximately twice the time as in the fixed-nuclei scenario. Mode-resolved kinetic-energy analysis reveals that, with increasing field strength, the laser-induced nuclear response shifts from selected bond stretchings to collective low-frequency modes. These results provide a benchmark for assessing the interplay between vibronic dynamics and strong-field coupling in donor/acceptor oligomers.
Materials Science (cond-mat.mtrl-sci)
Integer defects in active nematics of ellipsoidal Quincke rollers
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-11-02 20:00 EST
Bao Ying Fan, Lin Liu, Jie Wu, Chen Song, Wen-de Tian, Kang Chen, Tian Hui Zhang
Transverse propulsion changes topological ordering in dense ellipsoidal Quincke rollers. Under an alternating-current electric field, a polar velocity field coexists with perpendicular nematic particle alignment. The system supports integer +1 velocity vortices with radial particle axes and -1 saddle defects. Oppositely charged defects migrate along domain walls and annihilate as polar domains merge. These results identify propulsion direction relative to particle shape as a control parameter for defect textures and collective ordering.
Soft Condensed Matter (cond-mat.soft)
5 pages, 4 figures
Potentials of individual atoms by convergent beam electron diffraction
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Tatiana Latychevskaia, Colin Robert Woods, Yi Bo Wang, Matthew Holwill, Eric Prestat, Sara Mustafi, Sarah J. Haigh, Kostya S. Novoselov
In convergent beam electron diffraction (CBED) on two-dimensional (2D) materials, the intensity distributions within the individual CBED spots map the local atomic arrangements within the probed region. In this study we demonstrate that the average intensities within the CBED spots essentially depend on the scattering parameters by a single atom, thus, offering the possibility of the direct measurement of such parameters. Scattering potential of an individual atom can be approximated by the Gaussian function and its parameters, the standard deviation and the maximal phase shift, can be recovered from the ratio of the intensities in the zero- and higher orders spots in CBED pattern. In order to demonstrate this, we simulated CBED patterns and extracted the atomic scattering parameters from such patterns. In the simulated examples, no weak phase object approximation is applied and the proposed method provides accurate results even for materials with large phase shifts up to 1.5 rad, as for example tungsten. The scattering parameters recovered from the experimental CBED patterns of graphene and twisted graphene-hBN structure show good agreement with the theoretically obtained values.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Carbon 201, 244-250 (2023)
Universal model of the growth of III-V tetrahedral semiconductors on polar surfaces: pyramids and glue atoms. I. Clean surface properties
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Pawel Strak, Stanisław Krukowski
Ab initio calculations were used to elucidate the properties of the polar surfaces of III-V tetrahedral semiconductors, i.e., metal- and nonmetal-terminated. The systems considered were clean wurtzite gallium nitride (i.e. (0001) and (000-1) GaN surfaces), zinc blende gallium phosphide (i.e. (111) and (-1-1-1) GaP), gallium arsenide (i.e. (111) and (-1-1-1) GaAs), and (111) and (-1-1-1) GaSb surfaces. The calculated data include the crystallographic structure and the electronic states of the termination atoms on both sides, i.e. their positions, energies, and occupations. All nonmetal-terminated surfaces exhibit no reconstruction, and their broken-bond states are located in the vicinity of the valence band maxima (VBM), pinning the Fermi level. The Ga-terminated surface exhibited (4 x 4) reconstruction related to the division of termination atoms into sp3 and sp2 hybridized in proportions of 6 to 10, based on charge redistribution according to the electron counting rule (ECR). Thus, the broken-bond state is separated into two sets, occupied and empty, with the Fermi level located between them in the vicinity of the conduction band minimum (CBM).
Materials Science (cond-mat.mtrl-sci)
18 pages, 11 figures, 2 tables
Universal model of the growth of III-V tetrahedral semiconductors on polar surfaces: pyramids and glue atoms. II. Adsorption of nonmetal atoms (N, P, As, and Sb) on Ga-terminated surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Pawel Strak, Stanisław Krukowski
Ab initio calculations were used to simulate the adsorption processes on Ga-terminated surfaces of tetrahedral semiconductors: GaN, GaP, GaAs and GaSb. The considered adsorbates are nonmetal species, i.e., nitrogen, phosphorus, arsenic, and antimony on wurtzite gallium nitride, i.e., GaN(0001) surfaces, zinc blende gallium phosphide, i.e., GaP(111), gallium arsenide, GaAs(111), and gallium antimonide, GaSb (111) surfaces. The cases investigated include single adsorbed nonmetal atoms and full coverage, i.e. theta=1 of these surfaces. The calculated results include the stable sites and the energies of the single adsorbed atoms: located at H3 sites at low coverage and in on-top positions at high coverage for GaP, GaAs and GaSb. At high nitrogen coverage, the N2 admolecules are formed, weakly attached to the surface. The calculated electronic properties of the single-adatom systems include the band diagrams of the slabs in real and momentum space, the energies of the quantum states. In addition, the overlaps of the quantum states of the nonmetal adatoms and the nearest topmost surface Ga atoms are given. The full coverage data include the atomic configurations and the bond energies of the adsorbed layers. The electronic properties include the above-mentioned data for single adatoms, together with additional properties related to interactions between adsorbed atoms. The evaporation stability analysis confirms that the adatoms stabilize the topmost Ga atoms against detachment because of the high energy barrier of DE > 3 eV which is further increased to DE > 4 eV by coverage located at H3 sites. Thus, growth simulations should employ unreconstructed Ga-terminated surfaces covered by nonmetal atoms located at on-top positions.
Materials Science (cond-mat.mtrl-sci)
35 pages, 14 figures, 1 table
Mirror-symmetry engineering of altermagnetism based on monolayer hexagonal lattices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Altermagnetism (AM) is a novel collinear antiferromagnetic phase characterized by spin-polarized bands and zero net magnetization. However, realizing AM in monolayer hexagonal lattices is strongly constrained by lattice symmetry. Here, we propose a mirror-symmetry-based design principle and implementation scheme for realizing AM based on monolayer hexagonal lattices and validate it using holey graphyne (HGY) as a representative system. By examining hydrogenated nonmetal units X$ -$ H (X = B, C, N, P, and S) introduced along the mirror-symmetry axis and extending the analysis to N$ -$ F, we identify the configurations that form two antiparallel spin sublattices related by mirror reflection. The N$ -$ H structure forms a stable altermagnetic ground state, with a momentum-dependent spin splitting up to 148.2 meV. The magnetism originates from $ \pi-\pi$ superexchange interactions, and H/F functionalization stabilizes intrinsic AM by regulating the local charge distribution. Our work offers insights into the design of light-element altermagnetic materials.
Materials Science (cond-mat.mtrl-sci)
Finite-time Mpemba crossings with imperfect preparation
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Two preparations evolving under the same thermal Markov generator can reverse their ordering in relative entropy even when the hotter state retains a nonzero slow-mode component. We derive a sufficient finite-time crossing condition for arbitrary finite irreducible reversible systems. The condition compares the preparations’ weights in the entire slowest eigenspace, including degeneracies, and gives an explicit upper bound using the separation from the next distinct decay rate. Exact finite-amplitude entropy comparisons also yield all-mode enclosures and bounds based on a retained spectrum with a controlled omitted tail. A preparation-error inequality converts finite-time sign margins into explicit probability tolerances; extensions account for temperature, generator, and stationary-reference uncertainty. We test the bounds on 2000 predefined network draws with four graph families and 4–64 states. There are 86 numerically located crossings, of which 45 satisfy the simple sufficient condition. In a selected eight-state example, retaining two nonstationary modes certifies a crossing before 1.55163, improving a certified slow-sector endpoint of 2.53951; the located crossing is near 1.26943. A reflecting diffusion in an asymmetric potential supplies a separate physical example, with systematic mesh refinement. Independent interval arithmetic certifies selected spectral bounds, finite-grid first crossings, and an entire preparation-temperature rectangle in a three-state benchmark. The theorem does not require exact slow-mode cancellation, while its numerical sharpness and detection coverage remain model dependent. These results concern relative-entropy relaxation and do not predict water-freezing times.
Statistical Mechanics (cond-mat.stat-mech)
20 pages. 4 figures
Underdamped Stochastic Optimal Transport with Landauer boundary conditions: machine learning and analytical solution
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Julia Sanders, Dario Lucente, Marco Baldovin, Paolo Muratore-Ginanneschi
Finding optimal transport protocols for underdamped stochastic processes is a difficult yet important problem in control theory. In this paper we develop a direct method, based on machine learning, to find the optimal solution of the problem in the presence of non-linear boundary conditions, including those modelling the Landauer bit-erasure problem. The dynamics is steered from a single-peak to a double-peak distribution in position space, by only acting on a controllable external potential. The problem is highly non-linear, and analytical solutions are not available in general. We benchmark our numerical results with a perturbative expansion, which is expected to hold in a suitable overdamped limit.
Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG), Optimization and Control (math.OC)
Main: 12 pages, 6 figures. Supplemental material: 11 pages
Microscopic structure at the morphotropic phase boundary in lead-barium meta-niobat
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Marco Fornari, Virginia Carnevali
Lead-barium niobate Pb$ _{1-x}$ Ba$ _x$ Nb$ _2$ O$ _6$ is a tetragonal tungsten-bronze ferroelectric that exhibits enhanced functional properties near a morphotropic phase boundary separating orthorhombic and tetragonal phases. Using first-principles electronic-structure calculations combined with ab initio molecular dynamics, we investigate how Ba substitution modifies cation-site occupancy, local distortions, and polarization behavior across the solid solution. By explicitly accounting for vacancy ordering and the inequivalent $ A$ -site cages intrinsic to the tungsten-bronze framework, we identify the structural origin of the orthorhombic-to-tetragonal transition. Increasing Ba content progressively weakens the cooperative in-plane off-centering of Pb ions in the pentagonal channels and promotes out-of-plane displacements of Nb and $ A$ -site cations, leading to a rotation of the spontaneous polarization from [110] to [001]. The transition occurs near $ x \approx 0.6$ , in quantitative agreement with experimental phase diagrams. These results provide a microscopic interpretation of the morphotropic phase boundary in Pb$ _{1-x}$ Ba$ _x$ Nb$ _2$ O$ _6$ and establish a clear structure-polarization relationship for tungsten-bronze ferroelectrics.
Materials Science (cond-mat.mtrl-sci)
Hierarchy of Electromagnetic Gauge Field Quantum Geometries
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Bin Wang, Fuming Xu, Lei Zhang, Jian Wang
The conventional Bloch quantum geometric tensor (QGT) describes electric-dipole geometry for spatially uniform perturbations and vertical Bloch transitions. We develop a broader framework linking quantum geometry to local and nonlocal electromagnetic response in gauge-field space, placing this tensor within a hierarchy of electric and magnetic multipole quantum geometries. The intrinsic antisymmetric adiabatic response in every electromagnetic channel is a Berry curvature in the space of its conjugate fields. The field-dependent projector uniquely fixes the QGT for that channel, pairing the response curvature with a quantum metric. This construction extends to spatially nonuniform perturbations, whose finite momentum transfer induces nonvertical Bloch transitions. We explicitly construct the current–current QGT connecting Bloch states at $ \mathbf{k}\pm\mathbf{q}/2$ , providing a unified metric and curvature description of nonlocal current response. In the doubled Brillouin zone, tangential derivatives generate conventional momentum-space QGT multipoles, whereas normal derivatives connect finite-momentum geometry to uniform electric- and magnetic-multipole-pair QGTs. We derive this connection through second order in $ \mathbf{q}$ . The finite-momentum curvature governs the intrinsic nonlocal Hall response, while an inverse-frequency moment of symmetric optical absorption probes the index-symmetric metric sector.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
2 figures
Static and dynamic density correlations of interacting active Brownian particles
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Artur Soriani, Samuel Cameron, Tomer Markovich, Elsen Tjhung
We develop a stochastic Dean–Kawasaki field theory to predict the static structure factor and collective intermediate scattering function of interacting active Brownian particles. Starting from the microscopic overdamped dynamics, we derive coupled stochastic equations for the density and polarization fields using an angular-moment closure. Gaussian linearization then yields closed analytical expressions for static and dynamic density correlations in terms of propulsion speed, mean number density, interaction potential, translational and rotational diffusivities. The coupling between density and polarization predicts a crossover from exponential relaxation to damped oscillations despite the absence of inertia. For Gaussian-core potential, the predictions contain no fitting parameters. Brownian dynamics simulations show quantitative agreement at low activity and long wavelengths, and reproduce the crossover behaviour. For Weeks–Chandler–Andersen potential, the nonintegrable core makes both the Fourier transform of the potential and the self-interaction correction term in the Dean–Kawasaki field theory ill-defined. We therefore introduce an approximation that replaces the interaction potential with a passive direct-correlation function fitted separately at each density and temperature. This approximation requires no additional activity-dependent fitting parameters.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
Counting kinks and magnons with the lattice: magnetoelastic effects in Cs$_2$CoBr$_4$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
V. Romerio, J. Nagl, K. Yu. Povarov, S. Gvasaliya, A. Zheludev
We report low-temperature dilatometry and ultrasound measurements on the frustrated quasi-one-dimensional antiferromagnet Cs$ _2$ CoBr$ _4$ across the entire cascade of field-induced magnetic phase transitions. The whole phase diagram can be recovered from these lattice probes, with distinct anomalies observed at each phase boundary. Elongation along the principal chain axis is found to closely track magnetization throughout the phase diagram. This behavior is interpreted in terms of kinks in the Néel structure and magnons in the transverse-ordered magnetic-BEC phases, each carrying a fixed lattice distortion. A simultaneous analysis of ultrasound and striction data allows us to quantify the strength of magnetoelastic coupling.
Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 13 figures
Pair density waves via interband pairing — a perspective from superfluid weight
New Submission | Superconductivity (cond-mat.supr-con) | 2026-11-02 20:00 EST
Yi-Jian Hu, Yi-Fan Jiang, Wen Huang
Pair density waves (PDW) are superconducting states that exhibit a spatially modulated pairing order parameter, corresponding to Cooper pairs carrying finite center-of-mass momentum. While some recent studies have emphasized the role of quantum geometry in stabilizing PDW order in certain multiband systems, we here present a systematic investigation of an alternative, geometry-independent mechanism: PDW order driven purely by interband Cooper pairing. Using the superfluid weight (SW) as a diagnostic, we study two canonical models. The first is the classic Fulde-Ferrell model of an $ s$ -wave superconductor subject to a Zeeman splitting field, which realizes pure interband pairing between two rigidly shifted bands; the second is a spinless honeycomb-lattice model with nearest-neighbor $ f$ -wave pairing, a modified version of which was recently found to exhibit PDW instability in density-matrix renormalization-group simulations. In both models the SW receives no quantum geometric contribution at the mean-field level, yet it can be greatly suppressed or even turn negative, signaling a tendency toward pairing with spatial phase modulations. For the first model, we establish that the SW is increasingly suppressed as the Zeeman field grows, drastically turning negative upon the emergence of extensive gapless excitations, i.e., the Bogoliubov Fermi surfaces. For the honeycomb $ f$ -wave model, we demonstrate, both analytically and numerically, vanishing quantum-geometric SW and an invariably negative total SW. Our results thus establish the SW as a qualitative indicator of the tendency toward PDW order, and provide a microscopic rationale for the interband-pairing-driven PDW instability.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
14 pages, 9 figures
Evaluating Instrument-Centered AI Agents for Table-Top Science Experiments
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Jiaqi Cai, Siyu Cheng, William S. Huxter, Li-Qiao Xia, Shuwen Sun, Shuai Yuan, Yifan Zhao, Naiyuan Zhang, Weijie Li, Muxian Xu, Ilija Zeljkovic, Xiaodong Xu, Pablo Jarillo-Herrero
Reliable evaluation of AI agents for table-top science experiments has remained elusive because live instruments are hard to reset and share at scale, while instrument statefulness and safety constraints complicate evaluation. We introduce instrMCP and q-devBench, an evaluation stack for instrument-centered AI agents in table-top experiments. instrMCP connects coding agents to scientific instruments through the Model Context Protocol, serving as the instrument-access harness. q-devBench reconstructs 37 real experimental tasks from condensed-matter physics as virtual QCoDeS instruments covering quantum electronic transport, scanning probe imaging, and calibration workflows. q-devBench exposes reproducible failure modes in laboratory-agent systems while preserving realistic instrument-control workflows. Across a range of commercial coding-agent configurations, current systems already show substantial operational competence, satisfying 70-83% of measurement-related rubric criteria. The main bottleneck is scientific analysis, where performance falls to 28-46%. In an analysis-only ablation in which agents receive clean reference datasets without running the virtual measurement session, analysis performance improves substantially, closing roughly two thirds of the difference between the measurement and analysis scores. This suggests that much of the deficit arises from the measurement-session context, including tool-use overhead, longer context, measurement-planning decisions, and possible acquisition errors, while a residual scientific-reasoning gap remains. Together, instrMCP and q-devBench provide a practical sandbox for benchmarking, diagnosing, and improving laboratory AI harnesses, and establish a route from controlled virtual evaluation to future live-hardware validation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
36 pages (26 main text + 10 supplemental material), 14 figures, 5 tables. Code: this https URL and this https URL
Dipolar Exciton Polarons in a van der Waals Homobilayer
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Yuxin Duan, Hongming Zhang, Yaofeng Zhu, Hang Zhou, Xinyue Zhang, Yan Liu, Song Luo, Long Zhang, Zhanghai Chen
Fermi polarons exemplify how many-body interactions give rise to emergent quasiparticles, providing a fundamental framework for understanding interacting quantum matter. In electron-doped two-dimensional semiconductors, exciton polarons offer optical access to Fermi-polaron physics and electrical tunability, yet achieving stronger and more controllable exciton-electron interactions remains a key challenge. Here, we realize dipolar exciton polarons in an electrically tunable van der Waals homobilayer, where interlayer excitons with spatially separated electrons and holes act as quantum impurities carrying permanent electric dipole moments. These dipolar polarons exhibit substantially enhanced exciton-electron interactions, with binding energies more than four times those of conventional intralayer exciton polarons. We further demonstrate that Fermi-sea layer polarization provides an additional degree of freedom for controlling many-body interactions. In particular, the presence of a Fermi sea induces hybridization between oppositely oriented dipolar polarons, whereas confining the Fermi sea to a single layer suppresses this hybridization and produces orientation-selective many-body dressing. Our findings establish an experimental platform for dipolar-polaron physics in which dipole orientation and Fermi-sea layer polarization jointly govern many-body interactions, opening a route towards electrically tunable interactions and dipolar-polaron-mediated attraction between itinerant electrons.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
6 pages, 4 figures
Pair-Condensation Peak in Radio-Frequency Dimer-Projection Spectroscopy of a Unitary Fermi Gas
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-11-02 20:00 EST
Radio-frequency dimer-projection spectroscopy has recently emerged as a powerful probe of strongly interacting Fermi gases, yet its frequency-resolved spectrum remains largely unexplored. Here we show that the spectrum exhibits two qualitatively distinct features: a broad quasiparticle continuum governed by fermionic pairing and a sharp pair-condensation peak arising from the coherent projection of condensed Cooper pairs onto the final-state dimer. To reveal this physics, we develop a point-dimer approximation that exploits the separation between the molecular and many-body length scales and expresses the radio-frequency response directly in terms of pair correlations in the initial many-body state. Within the BCS mean-field theory, we derive the frequency-dependent spectrum, identify the microscopic transfer processes underlying its structure, and show that the continuum possesses a threshold determined by the superfluid gap. Our theory establishes radio-frequency dimer-projection spectroscopy as a unified probe of short-range correlations, fermionic pairing, and long-range coherence in strongly interacting Fermi gases.
Quantum Gases (cond-mat.quant-gas)
Phys. Rev. A 114, L041301 (2026)
Spontaneous Circular Dichroism and Memory Effect from Surface Defects in Altermagnetic MnTe
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Benjamin F. Mead, Isaiah Gray, Seng Huat Lee, Michael Chilcote, Zi-Jie Yan, Sijie Xu, Aparna Jayakumar, Emilia Morosan, Jörn W. F. Venderbos, Cui-Zu Chang, Zhiqiang Mao, Pengcheng Dai, Matthew Brahlek, Liang Wu
Altermagnetism has emerged as a new class of magnetism with vanishing magnetization and macroscopic time reversal symmetry breaking. Hexagonal MnTe is a g-wave altermagnet with a 307 K Néel temperature, large spin splitting, and an anomalous Hall effect. However, the relationship between altermagnetism and the anomalous Hall effect in MnTe remains debated. Here, using optical magnetic circular dichroism, we observe hysteresis and a memory effect in a MnTe bulk crystal below 250 K. No hysteresis is seen after polishing the bulk crystal and in thin films. We conclude that the hysteresis in magnetic circular dichroism in the bulk crystal is from surface defects. The similar temperature dependence and a sign change between circular dichroism and the anomalous Hall effect indicate that the origin of the anomalous Hall effect in transport is likely not intrinsic.
Materials Science (cond-mat.mtrl-sci)
8 pages, 3 figures
Fano Resonance of a Magnonic Ring Resonator with a Nano-Scatterer Embedded in a Magnonic Conduit
New Submission | Other Condensed Matter (cond-mat.other) | 2026-11-02 20:00 EST
Rajesh Kumar, Yat-Yin Au, Snorri Ingvarsson
We present micromagnetic simulation of a nanoscale magnonic ring resonator coupled to a magnonic waveguide, with and without a hole embedded in the waveguide (H-NRR and NRR respectively), for realizing transformation into a Fano resonance frequency spectral lineshape from a Lorentzian one. Transmission and reflection spectra of the H-NRR and NRR have been analyzed for different structural parameters (embedded hole diameter and gap between the ring and the waveguide) and material parameters (damping factor of the ring) to achieve maximum spectral transmission magnitude variation. The obtained micromagnetic simulation results are supported by an analytical model that consists of two-tracks of wave propagation, forwards and backwards. Our findings show that H-NRR system demonstrates a monotonic dependence of spectral transmission magnitude variation against the aforementioned design parameters (gap and damping) which should provide better engineering controllability and tolerance when compared with the original NRR system. Overall, our proposed structure and study may help in building unconventional magnonic integrated circuits for sensing, data processing systems and computing.
Other Condensed Matter (cond-mat.other), Materials Science (cond-mat.mtrl-sci)
Uploaded file 31 pages, comprising article: 13 pages, supplementary material: 18 pages
Appl. Phys. Lett. 129, 172407 (2026)
Creating functional nanostructures for vortex manipulation in superconducting Bi$\text{2}$Sr$\text{2}$CaCu$\text{2}$O$\text{8+x}$ thin films via focused He ion beam irradiation
New Submission | Superconductivity (cond-mat.supr-con) | 2026-11-02 20:00 EST
Bernd Aichner, Christoph Schmid, Sandra Keppert, Reinhold Kleiner, Edward Goldobin, Johannes D. Pedarnig, Dieter Koelle, Wolfgang Lang
Bi$ _2$ Sr$ _2$ CaCu$ _2$ O$ _{8+x}$ (Bi-2212) is a highly anisotropic high-temperature superconductor exhibiting unique vortex dynamics due to its layered structure. Precise nanoscale patterning of ultrathin Bi-2212 films remains challenging, limiting controlled studies of vortex pinning. Here, we employ 30 keV focused helium ion beam (He-FIB) irradiation to fabricate periodic arrays of columnar defects with 100 nm spacings in optimally-doped Bi-2212 thin films, thereby creating artificial vortex pinning centers. Magnetotransport measurements reveal pronounced vortex matching effects, evidenced by minima in magnetoresistance and peaks in critical current at commensurate magnetic fields. The angular dependence of magnetoresistance and critical current scale with an effective magnetic field, indicating strong confinement of pancake vortices along irradiation-induced tracks. These findings demonstrate the efficacy of He-FIB nanopatterning in modulating the superconducting properties in Bi-2212 thin films, providing a platform for fundamental studies of vortex matter and advancing prospects for device applications based on this highly anisotropic superconductor.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
11 pages, 7 figures
Full-Potential Korringa Kohn Rostoker Study of Structural and Mechanical Properties in SiGeSn Alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Wasim Raja Mondal, Swarnava Ghosh, Ka-Ming Tam, Markus Eisenbach, Yang Wang, Hanna Terletska
Accurate first-principles descriptions of open, covalently bonded crystal structures remain challenging within conventional Korringa–Kohn–Rostoker (KKR) approaches owing to the spherical approximations commonly employed for the effective crystal potential. Here, we systematically assess the recently developed full-potential KKR (KKR-FP) implementation in the open-source MuST package and demonstrate its applicability to diamond-structured group-IV semiconductors and SiGeSn alloys. Benchmark calculations for diamond-structured Si reveal substantial limitations of the conventional muffin-tin and atomic sphere approximations, whereas KKR-FP accurately reproduces the experimental equilibrium lattice parameter and bulk modulus, yielding 5.433 and 94.9 GPa. The full-potential treatment also recovers the semiconducting character of Si. Further calculations for elemental Ge and Sn establish the applicability of the approach across group-IV materials. Extending this framework to SiGeSn alloys, we investigate their composition-dependent equilibrium lattice parameters, bulk moduli, and mixing enthalpies. The calculated lattice parameters exhibit positive deviations from Vegard’s law, while the bulk modulus decreases substantially with changes in alloy composition. Moreover, positive mixing enthalpies of 180.92 and 346.32 meV/atom are obtained for Si0.5Ge0.375Sn0.125 and Si0.375Ge0.25Sn0.375, respectively, indicating an energetic penalty for homogeneous alloy formation relative to the selected elemental reference states. These findings highlight the importance of nonspherical potential contributions in accurately describing open-structured semiconductors and establish KKR-FP within MuST as a promising framework for investigating the structural properties and mixing energetics of compositionally complex group-IV alloys
Materials Science (cond-mat.mtrl-sci)
5 figures
Magnetic control of reflectionless states and an intrinsic-mode exceptional point in a magnon-phonon coupling system
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Mingyuan Ma, Jiongjie Wang, Chong Chen, Weiqi Du, Liyang Liao, Yanzhang Cao, Peisen Liu, Boyuan Xiao, Deqi Tao, Shixuan Liang, Sulei Fu, Jiang Xiao, Cheng Song, Feng Pan
Reflectionless states (RLs) and exceptional points (EPs) are hallmark singular responses of non-Hermitian systems, with potential applications in sensing, wave control, and energy manipulation. Yet, realizing and independently tuning these states in a compact integrated platform remains challenging. Here, we demonstrate two-dimensional magnetic control of RLs and EPs in an on-chip magnon-phonon system based on a FeGaB-32 degree-YX-LiNbO3 heterostructure. The magnetic-field magnitude tunes the magnon-phonon detuning, driving a low-loss reflection zero across the real-frequency axis and producing two field-tunable RLs with near-vanishing reflection. A closed contour of the experimentally measured complex S11 around the reflection-zero singularity accumulates a -2pi phase winding. Independently, rotating the magnetic field tunes the magnon-phonon coupling strength, driving the intrinsic magnon-phonon eigenmode spectrum across an exceptional point, identified by the exchange between real-part and imaginary-part eigenvalue splitting. A unified one-port input-output model connects the measured complex S11 response to the field-driven dynamics of the reflection zeros and the angle-tuned intrinsic magnon-phonon eigenmodes. These results establish a magnetically programmable non-Hermitian magnon-phonon platform for integrated wave control and compact vector magnetic sensing.
Materials Science (cond-mat.mtrl-sci)
4 figures
Andreev-Enhanced Conductance in a Bilayer Graphene Quantum Point Contact
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Emma Horgan, Bernd Aichner, Nadine Omar, Kenji Watanabe, Takashi Taniguchi, Luca Banszerus
Quantum point contacts provide a platform for probing mode-dependent Andreev reflection. Here, we demonstrate Andreev-enhanced conductance in a gate-defined bilayer graphene quantum point contact coupled to a superconducting aluminum electrode. Electrostatic gating enables sequential mode occupation, verified by normal-state conductance quantization. In the superconducting state, the conductance is enhanced within the conductance plateaus, while the enhancement decreases between plateaus, consistent with the nonlinear transmission dependence of Andreev reflection. The enhancement yields effective transmission probabilities up to 0.9, and extends over a bias window of approximately 140 $ \mu$ V, which we associate with a proximity-induced superconducting gap, close to the gap of the aluminum film. For in-plane fields, the enhancement persists up to the critical field, and the bias window follows the spectral gap predicted by Abrikosov-Gor’kov theory. In contrast, perpendicular fields suppress the enhancement approximately linearly from zero field, deviating from homogeneous pair breaking and indicative of flux penetration.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
5 pages, 4 figures
Generative Design and Graph Neural Network Screening of Novel Bimetallic Alloy Catalysts for the Hydrogen Evolution Reaction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Vipin Kurian Elavunkel, Sylvain Le Tonquesse, Hadrien Vroylandt
Identifying earth-abundant catalysts for the hydrogen evolution reaction (HER) is a central challenge in scalable green hydrogen production. We present a computational pipeline that couples diffusion-based generative modelling, machine-learning force-field relaxation, and graph neural network (GNN) property prediction to discover bimetallic HER catalysts beyond the structures and stoichiometries covered by existing adsorption databases. A generative model (MatterGen) is fine-tuned on bulk alloy structures labelled with their minimum hydrogen adsorption energy and steered towards adsorption energies near zero. From the generated pool we retain the stable structures that are novel bimetallic alloys: binary compositions built from the training-set metals but at stoichiometries or structures absent from that database. Each candidate’s low-index facets are ranked by a machine-learning-force-field (MatterSim) surface-energy screen, and only the most stable terminations are converted into explicit slab models with hydrogen adsorbed at all high-symmetry surface sites and relaxed with the same force field. Two GNN surrogates (MEGNet and ALIGNN), trained on a high-throughput density functional theory (DFT) dataset, then screen the resulting slab candidates. Because the two models encode the local environment through different inductive biases, we retain only the alloys on which both agree, reducing the influence of any single model. This consensus screening, combined with a MatterSim energy-difference triangulation, resulted in a shortlist of near-thermoneutral bimetallic candidates. Eight are validated with plane-wave DFT, and four of them, Pd5Au, Pt5Rh, Cu5Pt3, and Pd13Ru3, bind hydrogen within the thermoneutral window. All eight alloys are dynamically stable by phonon calculations. These four alloys are highlighted as DFT-validated bimetallic HER candidates for experimental follow-up.
Materials Science (cond-mat.mtrl-sci)
18 pages, 9 figures
Existence of the thermodynamic limit for the Hopfield model
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-11-02 20:00 EST
Adriano Barra, Fabrizio Durante
We prove that the quenched pressure of the Hopfield model with $ K\sim\alpha N$ i.i.d. symmetric Rademacher patterns has a thermodynamic limit at every load $ \alpha\in(0,\infty)$ , finite inverse temperature and uniform external field, with no replica-symmetry, order-parameter concentration or non-condensation hypothesis required. The limit is the supremum over $ r$ of limiting pressures of mixed models with $ r$ binary patterns in a Gaussian bulk. Via the Hubbard–Stratonovich representation we extract the finitely many patterns whose hidden coordinates exceed $ \delta\sqrt N$ ; a collective interpolation replaces the other binary patterns by Gaussian ones with error $ O(\delta^2)$ uniform in the volume, and convex concentration on the discrete cube controls the disorder-dependent choice of retained patterns. For the mixed models we prove a Gaussian hidden-spin truncation bound uniform in the volume and in an arbitrary Ising potential, and convergence for Gaussian bulks with finitely many site-field types, reducing to results of Ho and of Chen, Ho and Issa on non-convex vector spin glasses with compact spins. For Gaussian patterns we give an alternative proof of the existence result announced by Camilli, Contucci and Mingione, extended to a uniform field and an extra binary pattern. In both cases the pressure has exponentially small deviation probabilities and converges a.s.; internal energy and entropy converge wherever the limit is differentiable. An extra binary Mattis pattern admits a scalar variational reduction. At zero field the Rademacher pressure dominates the Gaussian one with an extra binary pattern, which dominates the pure Gaussian one. No explicit formula is given. The proofs were generated through extensive interaction with the AI models Claude (Opus5.5) and ChatGPT (Sol6.1), based on the problem formulation and guidance of the authors.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Probability (math.PR)
Thermal conductivity of Lennard-Jones fluids from equilibrium thermodynamics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Miguel Hoyuelos, Alejandro Alés
We derive a general expression for the thermal conductivity of simple fluids within a thermodynamic transport theory (TTT) in which the Onsager coefficients of an interacting system are related to those of an ideal reference system through the ratio of the determinants of the Hessians of the relevant thermodynamic potential. The transported quantity is identified with an effective energy density proportional to the rms energy fluctuations of a small fluid cell. The result expresses the thermal conductivity as the product of its dilute-gas value and a function of equilibrium thermodynamic properties, namely the specific heats at constant density and at constant $ \rho T$ and the temperature derivative of the latter, with no adjustable parameters. For hard spheres, it reduces to a previously verified expression in terms of the thermodynamic factor. The theory is tested against molecular dynamics results for the Lennard-Jones (LJ) and the truncated and shifted Lennard-Jones (LJTS) fluids in the supercritical region, for densities up to $ \rho^\ast=0.8$ , using equations of state based on perturbation theory. For the LJTS fluid, the mean absolute percentage error is below 8% for all the temperatures considered. For the LJ fluid, the predictions are compared with those of the revised Enskog theory for Mie fluids, using the same equation of state: TTT gives smaller errors at almost all temperatures, with a significant improvement at low temperatures, where the errors are reduced approximately by a factor between two and three.
Statistical Mechanics (cond-mat.stat-mech)
12 pages, 4 figures and 3 tables
Shock Loading Accesses Reaction Pathways beyond Accelerated Thermolysis
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Mingjie Wen, Jiahe Han, Zihan Zhou, Hao Wang, Xueyong Guo, Qingzhao Chu, Dongping Chen
Thermolysis and shock loading can produce similar major stable products in energetic materials, despite different chemical evolution and reaction pathways. Here, we develop EMFF-MACE, a reactive machine-learning potential for C/H/N/O energetic materials, enabling thermolysis simulations of 20 materials and shock simulations of 10 on a common potential energy surface. Comparisons at matched normalized reaction progress reveal divergent chemical states and local structural environments. Mean reaction-state similarity decreases from 94.0% at 20% progress to 25.9% at trajectory endpoints, while 47.1-92.6% of shock local environments lie outside corresponding material-specific thermolysis reference domains. Structural and reaction-network analyses reveal enhanced intermolecular reorganization and additional association and rearrangement branches under shock loading, despite partially shared early decomposition chemistry. These findings show that loading history influences the structural states and subsequent reaction pathways accessed during decomposition, rather than merely the rate of thermolysis.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
28 pages, 9 figures, 1 table
Microswimmers lose by swimming selfishly
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-11-02 20:00 EST
At low Reynolds number, microswimmers are coupled by the flows they create, even when they are apart. The best way for each swimmer to push itself forward then depends on its neighbors, turning swimming together into a game. To study this, we optimize the shape changes of soft swimmers, alone and in pairs, with a differentiable Stokes solver. From random initial membrane motions, a lone swimmer converges to a traveling membrane wave. In a pair, the stroke of a swimmer affects its neighbor far more than the neighbor affects its own best stroke. For swimmers in line, this influence decays as $ 1/\ell$ with their separation $ \ell$ , whereas the incentive to respond decays as $ 1/\ell^2$ . Selfish swimmers, which maximize their own payoff, respond only to the weak incentive. The cooperative gain they miss decays only as $ 1/\ell^2$ , and their selfish adaptations leave the pair worse off than if both had kept their solitary strokes. Related swimmers, which also value the payoff of their neighbor, recover this gain, whereas competitors pay to hinder each other, both following a law that we derive analytically. Hydrodynamics alone thus makes swimming in company a social dilemma, whose outcome depends on how much the swimmers value each other.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Fluid Dynamics (physics.flu-dyn), Populations and Evolution (q-bio.PE)
Tensor cluster expansion as an efficient surrogate for multi-ACE
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Jacob Jeffries, Enrique Martinez, Eva Zarkadoula
In this work, we generalize an on-lattice tensor cluster expansion (TCE) framework to an arbitrary correlation order. We show that these generalized tensor cluster expansion features span a subspace of MACE features, suggesting that TCE features can sufficiently pre-screen MACE features for chemical diversity in alloyed transition metal dichalcogenide (TMD) monolayers. We show that, using maximum-entropy subset sampling, we can empirically recover chemical diversity from MACE features using a cheaper TCE representation. We then fine-tune a multi-ACE (MACE) potential with both subsets, and use this potential to predict temperature-dependent vibrational properties in alloyed TMD monolayers with varying chemical ordering. In our approach, TCE features can be used as cheap surrogate features for pre-screening chemically rich configurations using MACE features, allowing for the more efficient finetuning of atomic cluster expansion (ACE) potentials, thus achieving a tractable prediction of finite-temperature alloy thermodynamics on modest hardware.
Materials Science (cond-mat.mtrl-sci)
26 pages, 11 figures
Solvable coupled cluster states in $d=\infty$ with prescribed momentum distribution
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Two of the most successful ideas in many-body theory, the exponential coupled cluster ansatz and DMFT, have to date developed separately. We establish a connection between them, by showing that the infinite dimensional limit of the hypercubic lattice allows the exact closed-form evaluation of static expectation values of coupled cluster wave functions, provided the cluster amplitudes admit a low-rank decomposition. As a result, evaluation errors – a serious concern in conventional coupled cluster theory – can be disentangled from limitations to expressivity of coupled cluster states. For this family of coupled cluster states, the cavity construction in $ d\to\infty$ exactly reduces the environment of a lattice site to a Gaussian Grassmann kernel, and irreducible diagrams for one-body expectation values are found to be site-diagonal (in analogy to the DMFT self-energy). The resulting ``impurity problem” is an integral over a finite number of Grassmann variables rather than a dynamical quantum impurity problem, so that static observables derive exactly from a static self-consistency condition: a wave function counterpart of DMFT. For the simplest case of a cluster amplitude restricted to rank-one doubles, we obtain the momentum distribution in closed form. We show that any momentum distribution can be realized by a state that is the exact and unique ground state of an explicit parent Hamiltonian with a gapless single-particle tunnelling spectrum. By construction these coupled cluster states variationally recover low order perturbation theory for the Hubbard model. Their failure in the strong coupling regime near the Mott transition diagnoses a fundamental limitation of coupled cluster doubles. Intriguingly, our family of coupled cluster wave functions includes a gapless state with zero quasiparticle weight, with a momentum distribution that is completely smooth at the Fermi energy.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
22 pages, 2 figures
Relaxation speed in quenched-random force fields
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-11-02 20:00 EST
Jan Meibohm, Sabine H. L. Klapp
Disorder is commonly expected to slow down relaxation, as in glasses and disordered magnets. Here we show that this need not be the case in general, by analysing the asymptotic relaxation rate of a Brownian particle in a harmonic background potential and a quenched-random Gaussian force field with conservative and non-conservative components. Combining weak-disorder perturbation theory, random-matrix theory, and numerical solutions of the Fokker-Planck equation, we show that the outcome depends on the geometry of the background and on the properties of the random forces. We identify two distinct mechanisms that shape the relaxation speed: an effective stiffening of the background by the disorder, as previously reported in one dimension, and interactions (repulsive and attractive) between the levels of the Fokker-Planck operator. Through level attraction, a common feature of non-Hermitian operators, non-conservative driving forces pull the slowest mode towards faster ones, which facilitates faster relaxation. In anisotropic backgrounds, both effects occur at second order in the disorder strength, enabling either slower or faster relaxation. In isotropic backgrounds, level interactions dominate and the disorder affects the degenerate slowest mode already at first order. The shift is then given by the left-most eigenvalue of a Gaussian random matrix and relaxation is generically slowed down. In backgrounds whose anisotropy is comparable to the disorder strength, level attraction is most effective by merging the slowest mode with its neighbour into an oscillating complex-conjugate pair. In this case, relaxation becomes faster on average once the random forces are sufficiently non-conservative. Our results draw a nuanced picture of how disorder affects the asymptotic relaxation speed in complex systems and uncover general mechanisms that are likely to apply beyond the current setting.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn)
45 pages, 24 figures
Anomalies of TQFTs coupled to parameter spaces and constraints on ground-state degeneracies
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Anomalies of global symmetries can arise in long-range entangled quantum many-body systems and provide useful constraints on their dynamics. In this paper, we study anomalies of $ d$ -dimensional topological quantum field theories (TQFTs) coupled to parameter spaces and their implications for ground-state degeneracies. Specifically, we formulate anomalies as obstructions to constructing parametrized families of TQFTs. We discuss how the classification of these anomalies depends on the choice of topology on the universal $ \mathrm{U}(1)$ $ (d-1)$ -form symmetry. In this framework, we use the projective ground-state bundle obtained by compactifying the TQFT on a spatial manifold to derive a general constraint relating its ground-state degeneracy $ N$ to its torsion anomaly $ \omega$ , expressed as $ N\int_W\omega\in\mathbb{Z}$ for bundles $ W$ of spatial manifolds over closed surfaces. We apply this constraint to ground-state degeneracies of (2+1)-dimensional TQFTs with framing and 1-form symmetry anomalies and to obstructions to symmetry-preserving TQFTs. We also discuss implications for bordism generators and propose a conjecture on anomaly detection by manifolds fibered over surfaces.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph)
41 pages
Generation and spectroscopic characterization of continuous-wave 148.4-nm light in strontium tetraborate
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Ming Guan, Yang Wang, Heng Tu, Kaifgeng Zhou, Zhengrong Xiao, Zhong Zuo, Songpo Xu, Shaogang Yu, Xin Tong, Linqiang Hua, Xiaojun Liu
Continuous-wave (CW) radiation at 148.4nm is required to drive the $ ^{229}$ Th isomeric transition of a solid-state nuclear clock, and frequency doubling of 296.8-nm light is its most direct source. We generate CW 148.4-nm light by random quasi-phase matching in strontium tetraborate and characterize it with a compact prism spectrometer built for the purpose. The spectrometer separates the harmonic from the pump on a CaF$ _2$ prism, reads the wavelength from the rotation angle of a solar-blind photomultiplier, resolves the two lines with $ \delta\lambda \approx 0.6nm$ , and yields an absolute power calibration. At room temperature the source delivers $ 1.9nW$ at 148.4nm, rising to 5.7 nW at the optimum crystal temperature. The conversion efficiency is also strongly structured in temperature: between 30 degree and 50 degree it shows several pronounced maxima, with neighbouring extrema only a few degrees apart, so that a small temperature excursion moves the output from a maximum to a minimum. These results provide practical guidance for optimizing and stabilizing 148.4-nm sources for solid-state $ ^{229}$ Th nuclear clocks.
Materials Science (cond-mat.mtrl-sci)
7 pages, 6 figures
Current-driven transient dynamics of magnetic-octupole domain walls in noncollinear antiferromagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Current-driven magnetic-octupole domain walls in noncollinear antiferromagnets are promising for fast spintronic devices, yet their transient dynamics are not yet fully understood. Here, we investigate spin-orbit-torque-driven domain-wall motion in Mn$ _\text{3}$ Sn using a multipole micromagnetic framework. The three symmetry-related 60° walls exhibit equivalent current-driven dynamics, unlike their field-driven motion. For a representative 60° wall, the post-pulse motion is governed by relaxation of the current-induced rotation of the surrounding octupole domains, with a characteristic time of approximately 33 ps quantitatively captured by a uniform-domain analytic model. By resolving spatially nonuniform texture dynamics beyond this analytic description, the simulations further reveal an additional slow relaxation in a composite 180° wall associated with the relative motion of its constituent walls. The post-pulse response also varies systematically with the exchange stiffness and magnetic anisotropies. These results identify distinct domain and internal-coordinate relaxation channels and establish the intrinsic time scales governing pulse-controlled positioning of magnetic-octupole domain walls in antiferromagnetic spintronic devices.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures
Drying kinematics selects open honeycomb fold networks on solvent-extracted viscoelastic thin films and gels
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-11-02 20:00 EST
Fan Zhao, Surjyasish Mitra, Sunandan Tandon, Zoya Leonenko, Boxin Zhao, Sushanta K. Mitra
Solvent extraction and drying of substrate-supported viscoelastic films and gels produce quasiperiodic networks of three-armed surface folds. In this Letter, we examine the physical mechanisms governing their formation, length scales, and geometric organization. We observed that swelling-induced compression in the pinned film drives localized folding of a stiffening, diffusively thickening surface skin over a drained underlayer. Combining experiments and theory, we reveal that both the pattern wavelength and fold-arm length scale with the dried-film thickness following a power-law with an exponent 5/8, with remarkably weak dependence on elastic modulus. The folds form 120-degree junctions on a triangular lattice, defining an open honeycomb network whose pitch satisfies p = sqrt(3)(aL + g), where g is the junction gap. Notably, the folds accommodate less than 0.1% of the stored compressive strain, implicating elastocapillary arrest, rather than strain relaxation, in limiting their amplitude. These findings establish distinct geometric, kinetic, and interfacial constraints governing pattern selection in drying soft solids.
Soft Condensed Matter (cond-mat.soft), Applied Physics (physics.app-ph)
Main text: 5 pages, 4 figures; Supplemental Material: 13 pages, 10 figures
Charge Pumping Leptogenesis from the Symmetric Mass Generation Phase on a Four-Leg Ladder Lattice
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Runze Chi, Meng Zeng, Tao Xiang, Yi-Zhuang You, Bertrand I. Halperin, Juven Wang
Quantized charge pumping in quantum Hall systems is a bulk topological property, typically manifesting on gapless boundaries as spectral flow through chiral edge modes upon flux insertion. When the boundary is anomaly-free, it can be symmetrically gapped by symmetric mass generation (SMG) interactions. However, the effects on quantized charge pumping at an interacting gapped boundary are unclear. We address this using density-matrix renormalization group simulations of a four-leg ladder quasi-(2+1)d realization of the (1+1)d 3-4-5-0 lattice chiral fermion model with six-fermion interactions at one edge. We find gapless modes near the interacting edge for both weak and strong couplings, but the edge can be in a fully gapped SMG phase at intermediate coupling. We also identify spontaneous breaking of the model’s $ \mathbb{Z}_2$ symmetry above a critical interaction strength. Across all three boundary phases, we find quantized charge pumping with the same pumped charge per flux quantum. The spatial distribution of the pumped charge varies between phases. Besides charge pumping, we study how a single injected fermion propagates under open boundary conditions. In the SMG phase, an interaction-induced flavor-mixing current develops at the endpoints of the gapped edge, which is absent in the weak- and strong-coupling limits. This current reveals a charge-redistribution mechanism unique to the SMG phase. Additionally, we propose an analogy between charge pumping in this model and a topological leptogenesis scenario in the (3+1)d Standard Model. The anomaly-free chiral U(1) symmetries of the 3-4-5-0 model play a role analogous to the baryon-minus-lepton symmetry of the Standard Model. In both settings, charge pumping can be associated with a continuous deformation along a classically defined but quantum-anomalous direction, while a discrete subgroup remains an exact quantum symmetry.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
30 pages, many figures
Quantum 3xplorer: AI-Native Engine for Next-Generation Quantum Materials Modeling
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-11-02 20:00 EST
Vsevolod Biryukov, Sergey V. Barabash, Pranab Kumar Das, Jack Deslippe, Mauro Del Ben, Felipe H. da Jornada, Yuming Shi, Johannes Voss, Zhenglu Li, Piero Altoe, Kamal Choudhary, Ruth Pachter, Steven G. Louie, Marvin L. Cohen, Timur Bazhirov
Quantum-mechanical approaches, such as density functional theory (DFT), underpin much of modern computational materials science and are the primary source of data for AI-driven discovery. Yet the established electronic-structure codes today represent decades-old software architectures, making new physical models slow and costly to implement, validate, and deploy on emerging hardware. We present Quantum 3xplorer (Q3, pronounced “Quantum Explorer”), an AI-native quantum simulation engine written from scratch by AI coding agents under the direction and supervision of domain scientists. As a first and demanding validation case, we implement plane-wave pseudopotential DFT end to end: norm-conserving, ultrasoft, and projector-augmented-wave formalisms, spin polarization, DFT+U, and dispersion corrections, together with forces, stresses, structural relaxation, and electronic-structure analysis. Q3 reproduces established reference implementations, runs faster on a single core in representative benchmarks, and scales across GPU-accelerated supercomputers. It was developed in weeks rather than years. Its layered, physics-first architecture separates abstract quantum-mechanical concepts from their numerical representations, making its framework extendable beyond plane waves to other basis sets and levels of theory. Its inputs and outputs follow structured, schema-validated data standards, making every result AI-ready. Q3 is open source under Apache 2.0 and built to be reused, extended, and improved by the research community. Q3 points to a paradigm shift in how computational quantum science is done. Scientists define the physics, formulate the models, and set the criteria for validation; AI agents write, test, and optimize the code. The decades-long path from a new theory to a trusted, high-performance implementation can thus collapse to days, significantly accelerating scientific discovery.
Materials Science (cond-mat.mtrl-sci)
29 pages, 3 figures, 10 tables
Observation of light-induced Haldane gap in graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-11-02 20:00 EST
Fei Wang, Xuanxi Cai, Wanying Chen, Xiao Tang, Jinze Li, Benshu Fan, Tianshuang Sheng, Jinxi Lu, Jiansong Li, Hongyun Zhang, Pu Yu, Peizhe Tang, Wenhui Duan, Angel Rubio, Zhiyuan Sun, Shuyun Zhou
Symmetry and topology, encoded in electronic wavefunctions, play a central role in the electronic properties and emergent phenomena of quantum materials. While these properties are conventionally determined by the equilibrium Hamiltonian, strong optical fields offer a fundamentally different route by reshaping the Hamiltonian on ultrafast timescales, turning symmetry and topology into dynamically controllable degrees of freedom. Graphene provides a paradigmatic platform for realizing this concept, where circularly polarized light has long been predicted to dynamically break time-reversal symmetry (TRS) and open a topologically nontrivial gap at the Dirac point. Despite extensive experimental efforts, direct observation of this Dirac gap-the defining spectroscopic signature of the dynamical TRS-breaking induced topological phase-has remained missing. Here we directly observe this light-induced Dirac gap in monolayer graphene. Time- and angle-resolved photoemission spectroscopy reveals that the gap emerges simultaneously with the optical field and exclusively under circularly polarized driving, directly linking its opening to dynamical TRS breaking. Together with Floquet theory, we identify the gap with a light-induced Haldane mass and reveal the associated nontrivial Floquet Berry curvature and Chern topology. By demonstrating dynamical TRS breaking in a prototypical non-magnetic material, our results establish optical driving as a route to ultrafast engineering of symmetry and topology, opening opportunities for dynamically tunable quantum matter beyond equilibrium.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
This manuscript was submitted and sent out for review on 2026/09/24
Resolving the spinon hierarchy of the Heisenberg antiferromagnet
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-11-02 20:00 EST
Ian P. McCulloch, Jesse J. Osborne
A local spin fluctuation in the spin-$ \tfrac12$ Heisenberg antiferromagnet creates an even number of fractional spinon excitations. We resolve its zero-temperature dynamical structure factor through six spinons directly in the thermodynamic limit. Beyond the established two-spinon contribution of $ 72.89%$ , the four-spinon response gives approximately $ 21.90%$ of the integrated intensity and six spinons contribute a further $ 4.3%$ , bringing the response to about $ 99%$ of both the intensity and first-frequency-moment sum rules. We derive momentum-independent first-moment fractions in the calculated sectors and a general upper-edge law $ S_n\sim A_n(k)(\omega_{n,u}-\omega)^{(n^2-3)/2}$ for every even $ n$ at nonzero momentum. The rapid growth of the edge exponent explains why the expanding multiparticle bandwidth carries very little high-energy weight, while higher sectors remain appreciable within the lower-sector continua.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech)
Research Square
Observation of light-induced Haldane gap in graphene
Physical Sciences - Article | Electronic properties and materials | 2026-11-01 19:00 EST
Shuyun Zhou, Fei Wang, Xuanxi Cai, Wanying Chen, Xiao Tang, Jinze Li, Benshu Fan, Tianshuang Sheng, Jinxi Lu, Jiansong Li, Hongyun Zhang, Pu Yu, Peizhe Tang, Wenhui Duan, Angel Rubio, Zhiyuan Sun
Symmetry and topology, encoded in electronic wavefunctions, play a central role in the electronic properties and emergent phenomena of quantum materials. While these properties are conventionally determined by the equilibrium Hamiltonian, strong optical fields offer a fundamentally different route by reshaping the Hamiltonian on ultrafast timescales, turning symmetry and topology into dynamically controllable degrees of freedom. Graphene provides a paradigmatic platform for realizing this concept, where circularly polarized light has long been predicted to dynamically break time-reversal symmetry (TRS) and open a topologically nontrivial gap at the Dirac point. Despite extensive experimental efforts, direct observation of this Dirac gap–the defining spectroscopic signature of the dynamical TRS-breaking induced topological phase–has remained missing. Here we directly observe this light-induced Dirac gap in monolayer graphene. Time- and angle-resolved photoemission spectroscopy reveals that the gap emerges simultaneously with the optical field and exclusively under circularly polarized driving, directly linking its opening to dynamical TRS breaking. Together with Floquet theory, we identify the gap with a light-induced Haldane mass and reveal the associated nontrivial Floquet Berry curvature and Chern topology. By demonstrating dynamical TRS breaking in a prototypical non-magnetic material, our results establish optical driving as a route to ultrafast engineering of symmetry and topology, opening opportunities for dynamically tunable quantum matter beyond equilibrium.
Research Square:rs-11148426 (2026)
Posted on Research Square
Physical sciences/Physics/Condensed-matter physics/Electronic properties and materials, Physical sciences/Physics/Condensed-matter physics/Topological matter, Physical sciences/Materials science