Materials Science
Machine Learning for Designing Undesignable Metal-Organic Frameworks
Satya Kokonda
Many crucial processes are too complex for computational modeling, requiring experimentation to identify promising materials. Here, a methodology for material design is presented, while photocatalysis is presented as a specific case-study. Metal-Organic Frameworks (MOFs) are a subset of highly promising porous nanomaterials, used in a variety of unmodellable applications. Reinforcement learning generated 60,000 novel MOFs optimized for CO/H20 selectivity. A predictor funnel system was created, iteratively removing low-scoring MOFs to 10,986 potential candidates, improving computational efficiency by 276%. While trained
Crystal Graph Convolutional Neural Network (CGCNN) models predicted features for creating a fitness function incorporating stability, catalytic ability, material cost, sustainability, and adsorption while allowing the inclusion of application specific design criterion. This designed function provides a computational method to model photocatalytic performance- and filtered down to two promising MOFs which each pass a myriad of synthesis criteria, first a Cr-based MOF with photocatalyst score 230% higher than the control. Second, a Zn-based MOF outperforms the best control across all relevant metrics, demonstrating robustness against variable fitness functions. This work designed 20 materials, each 125% better than the control for this application. Furthermore, analysis revealed insightful design patterns, such as the significant influence of metal cluster N262 on catalytic performance, providing a method for future work to narrow the chemical space. By incorporating industrially applicable features such as cost or stability of the material, this work successfully designs industrially promising materials in otherwise unmodellable processes such as drug delivery, while paving a method for multi-objective optimization incorporating 260% more features than prior work.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Geometry-Induced Domain-Wall Pinning and $\mathbb{Z}_2$ Asymmetry in Nominally One-Dimensional Rydberg Arrays
Elijah Pelofske, Frank Barrows and Cristiano Nisoli
We perform experiments on QuEra's neutral-Rydberg-atom Aquila
quantum computer, using quasi-adiabatic
evolution on 1-dimensional models. We use hardware fine-tuning to balance the measurement statistics close to zero net magnetization, in two different
geometric outlines: one closed triangular model with 33 atoms, and one 47-atom square with an engineered atom vacancy. The nature of this processor restricts the geometry of the atoms that can be programmed to a 2D plane. We report effects not predicted by the pure 1D Ising model, such as pinning of domain walls and $\mathbb{Z}_2$
symmetry breaking due to the interplay between van der Waals interactions and the Rydberg blockade. In particular, atoms around the atom vacancy and at the vertices of the 1-dimensional square-outline model strongly prefer the Rydberg state, leading to the effective model having a
ferromagnetic bond across the vacancy.
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Strongly Correlated Electrons
Flat-band formation and chiral superconductivity in driven topological insulators
Suman Jyoti De, Leo Goutte, Kartiek Agarwal et al. (+1 more)
We demonstrate that circularly polarized light can be used to Floquet-engineer nearly flat or Mexican-hat like electronic bands on the surface of three-dimensional topological
insulators (3D TIs), which under suitable conditions, can support topological superconductivity via purely repulsive Coulomb interactions. The driving acts not merely by gapping out the Dirac cone on the surface of the 3D TI, but can be used to diminish, and even flip in sign, the intrinsic
curvature of the surface state dispersion away from the Dirac point. Using parameters for canonical 3D TIs, we find that the flat band limit is attained for reasonable electric fields and the bands realized by changing the strength of the driving field have a similar energetic and spatial profile to those obtained in rhombohedral
graphene under varying displacement field, where the case for superconductivity with purely repulsive interactions has recently been made. We find that, with the aid of appropriately placed screening metallic gate, one can obtain $T_c \sim 7 $K in this setup while avoiding Wigner crystallization for low electron densities in the range of $10^{11}-10^{12}/\text{cm}^2$.
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All authors Suman Jyoti De, Leo Goutte, Kartiek Agarwal, T. Pereg-Barnea
Statistical Mechanics
From pink to brown: Interaction-driven noise color shift in the Aubry-André Model
S. A. Montes-Camacho and E. J. Torres-Herrera
We revisit the metal-
insulator transition in a one-dimensional
lattice subjected to an on-site quasiperiodic potential, modeled using
spin-1/2 particles with tunable nearest-neighbor interactions. To characterize the transition, we examine the power-spectrum, defined as the squared modulus of the
Fourier transform of consecutive level spacings. In the absence of interactions, the power-spectrum fails to capture clear signatures of the transition, consistently exhibiting brown-noise-like behavior across regimes. In contrast, the interacting case reveals a marked change: the metallic phase displays spectral fluctuations consistent with pink noise, while the insulating phase is characterized by brown noise. These results are supported by analyses of the level spacing distribution and the level number variance. Additionally, we demonstrate that both statistics and the structure of energy eigenstates provide reliable indicators of the transition, in both interacting and non-interacting scenarios.
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Materials Science
Parity-selective spin splitting in coplanar antiferromagnets via bichromatic driving
Di Zhu, Zhongbo Yan and Mohsen Yarmohammadi
Parity is a central characteristic of momentum-dependent
spin splitting in antiferromagnets (AFMs). Yet, intrinsic
crystal symmetries typically restrict the splitting to either even or odd parity, preventing flexible
spin control. Using a coplanar AFM, we demonstrate that bichromatic ($\omega$–$n\omega$) Floquet driving offers a natural way to bypass this constraint. This mechanism generates asymmetric
spin textures unattainable in static AFMs or under monochromatic driving. For the specific AFM considered here, we reveal an elegant relation between
spin-splitting parity and harmonic hierarchy: $\omega$–$2\omega$ fields generate highly tunable odd- and mixed-parity
spin splittings, whereas higher-order harmonics ($n \ge 3$) exclusively produce even-parity states. The macroscopic magnetization can also be toggled via the specific driving protocol and harmonic $n$. These distinct
spin splitting states manifest in qualitatively different macroscopic
spin currents generated after an optical quench—a definitive transport signature complementing direct visualization via
spin- and angle-resolved photoemission spectroscopy.
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Strongly Correlated Electrons
Altermagnetism from a Cu-Fe Lieb Lattice in FeSe/Cuprate Heterostructures
Ying Li, Augustin Davignon, Peng Rao et al. (+4 more)
Realizing altermagnetism in high-$T_c$ cuprate-based systems would provide a direct route for studying
spin-split electronic bands in the absence of net magnetization and investigate their interplay with unconventional superconductivity. Here, we propose that FeSe/cuprate
heterostructures offer such a platform, where a 45$^\circ$ twist of Cu and Fe layers creates an effective CuFe$_2$ Lieb
lattice in which Fe
magnetic order and Cu-Fe hybridization through the ligands induces altermagnetic $d$-wave
spin splitting. A minimal tight-binding model shows that this mechanism is generic. Furthermore, a substrate-induced inequivalence of the two Se sites in FeSe provides a second route in which altermagnetism originates in the Fe layer and is transferred to the cuprate layer by proximity. Density functional theory calculations for FeSe/Bi$_2$Sr$_2$CuO$_6$
heterostructures confirm the viability of both mechanisms and reveal ways to enhance the
spin splitting. These results establish superconducting cuprate/transition metal chalcogenide
heterostructures as a promising setting for engineering altermagnetism and studying its coupling to unconventional superconductivity.
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All authors Ying Li, Augustin Davignon, Peng Rao, Runhan Li, Maia G. Vergniory, Roser Valentí, Johannes Knolle
Strongly Correlated Electrons
Spin-incoherent Mott-Thouless pumps
Ajesh Kumar, Urban F. P. Seifert, Erez Berg et al. (+1 more)
A Thouless pump describes a system in which a quantized amount of charge is transported by one
lattice spacing per cycle when the parameters of a
Hamiltonian are varied slowly and periodically. In the standard case, this quantization requires the system to remain in its ground state with vanishing thermodynamic
entropy throughout the pumping process. Here, we introduce a class of Mott-Thouless pumps, which operate in highly entropic,
spin-incoherent Mott states. We show analytically that these states exhibit exponentially protected quantized transport despite their extensive
entropy, because the pumped charge resides in a gapped sector that remains dynamically decoupled from the hot
spin degrees of freedom. By contrast, motivated by a recent experimental realization, we identify other classes of Mott-Thouless pumps that lack this protection. In these systems,
spin excitations can efficiently generate charge excitations, leading to a rapid breakdown of quantized transport. Our analytical results are supported by numerically exact real-time simulations of finite systems.
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All authors Ajesh Kumar, Urban F. P. Seifert, Erez Berg, Achim Rosch
Mesoscale and Nanoscale Physics
Harnessing Native Chromium Oxidation for Giant Orbital Torque and Field-Free Magnetization Switching in NiFe/Cr Bilayers
Chirag Kalouni, Abhishek Kumar, Manish Kumar Mohanta et al. (+6 more)
Orbital currents offer charge-to-
spin conversion beyond the efficiency limit of conventional heavy-metal
Spin Hall sources. However, harnessing them has so far required either thick orbital-
Hall materials or additional heavy-metal conversion layers. Here, we show that the native
oxide of chromium, typically regarded as parasitic, transforms a simple NiFe\Cr
bilayer into a self-contained dual-channel orbital-current source without the need for any conversion layer. First-principles calculations predict a nearly threefold enhancement of the orbital
Hall conductivity upon surface oxygenation, driven by Cr(3d)-O(2p) hybridization. Experimentally, naturally oxidized NiFe\Cr
heterostructures exhibit a
giant damping-like torque efficiency of $3.9 \times 10^{6}$ $\Omega^{-1}$ m$^{-1}$, exceeding Pt (Ta) by one (two) orders of magnitude. The torque depicts a non-monotonic Cr-thickness dependence which cannot be explained by a conventional model. We have developed a drift-
diffusion model with an oxidation-gated interfacial source which quantitatively reproduces the data, revealing that the Cr-CrO$_x$ interface generates orbital currents over an order of magnitude stronger than the bulk orbital
Hall channel with an orbital transport length of $\approx 4$ nm. The enhanced torque enables field-free magnetization switching at $1.58 \times 10^{11}$ A m$^{-2}$, outperforming heavy-metal and CuO$_x$
benchmarks. These results establish native oxidation as a scalable strategy for realizing efficient orbital-torque devices.
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All authors Chirag Kalouni, Abhishek Kumar, Manish Kumar Mohanta, Kanupriya, Athira Ravindran K, Damanpreet Kaur, Preet Kamal, Puru Jena, Debangsu Roy
Statistical Mechanics · Cross-listed from nlin.PS
Mean-Field Theory of Chiral Active Model B: Arrested Coarsening and Chiral Fingering Instabilities
Kristian Blom and Uwe Thiele
We derive and analyze a mean-field theory of the
chiral Ising model recently introduced by Wang, Pietzonka, and Jülicher in "Edge Currents Shape Condensates in
Chiral Active Matter", arXiv:2603.20064. Starting from the master equation for clockwise and counterclockwise rotations of 2x2
spin blocks, we first obtain spatially discrete
evolution equations for the spatially resolved average magnetization. On this discrete level, we show that a
chiral bias strongly affects phase coarsening: domains coarsen anisotropically, develop nearly rectangular shapes, and eventually display chirality-induced arrested coarsening. Taking the continuum limit of these equations yields an active field theory that has the structure of a relaxational Model-B-type dynamics supplemented by a
chiral current that permanently drives the system out of
equilibrium. The coarse graining explicitly shows how microscopic rotational bias generates tangential currents localized at interfaces. Using this continuum theory, we perform a linear stability analysis of radially symmetric clusters and identify a
chiral fingering instability in which angular perturbations of the interface are amplified and eventually lead to radially asymmetric rotating states or disordered states.
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Statistical Mechanics
When trajectory-based bounds fail: information thermodynamics under noisy feedback
Natalia Ruiz-Pino, Ludovic Bellon and Antonio Prados
Information engines exploit feedback to extract work from thermal fluctuations, extending the second law of thermodynamics through information-theoretic bounds. While several such bounds have been proposed, their relative performance under realistic conditions—where measurements are noisy and feedback is temporally correlated—remains largely unclear. Here, we experimentally and theoretically investigate this problem in an underdamped feedback-controlled system with Markovian measurements but non-Markovian control sequences. We compare three representative bounds derived from transfer
entropy, unavailable information, and Markovian mutual information, and find that none is universally optimal. Instead, measurement noise preferentially affects information measures that rely on detailed trajectory statistics, while leaving quantities based on instantaneous correlations comparatively robust. As a consequence, trajectory-dependent bounds deteriorate rapidly, giving rise to a crossover in which the Markovian mutual-information bound becomes tighter than the unavailable-information bound over a broad range of measurement noise. Our results reveal a general limitation of information-theoretic descriptions that rely on detailed trajectory statistics in realistic settings and provide a unified perspective on information thermodynamics beyond idealised feedback protocols.
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Materials Science
MatCreatioNN: Machine learning-guided computational discovery of photocatalysts for environmental applications
Satya Kokonda
The rational design of photocatalysts for environmental remediation and CO2 conversion remains limited by the high computational cost and sparse experimental data describing multi-parameter photocatalytic behavior. This work presents an integrated machine-learning framework that couples reinforcement learning-based metal-organic framework (MOF) generation with a multi-stage
Crystal Graph Convolutional Neural Network (CGCNN) prediction funnel to identify photocatalysts optimized across multiple electronic and structural features. 120,000 MOF candidates were generated and screened using 13 key descriptors, including band-gap suitability, CO2/H2O selectivity, adsorption energy, and structural stability. The funnel approach reduced computational cost by 4.13-fold while maintaining predictive robustness. Two top candidates, a Cr-based and a Zn-based MOF, exhibited predicted photocatalytic fitness values of 1.70 +/- 0.25 and 1.20 +/- 0.05 fold higher respectively than
benchmark materials such as PCN-224(Zr), demonstrating simultaneous improvements in light absorption, redox energetics, and framework durability. Simulated X-ray diffraction patterns confirmed strong structural agreement with experimentally synthesized MOFs, indicating high synthesizability. Post-hoc analysis revealed recurring structural motifs, such as the N262 metal cluster, that correlated strongly with high predicted photocatalytic activity. These results highlight the potential of data-driven methods to accelerate discovery of efficient and durable photocatalysts for environmental and energy-related transformations, providing a foundation for experimental realization and large-scale implementation of computationally designed MOFs.
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Mesoscale and Nanoscale Physics
Magnetic Breakdown and Anomalous Quantum Oscillation in Rhombohedral Tetralayer Graphene
Jing-Yu Zhao, Yang-Zhi Chou and Sankar Das Sarma
We investigate
magnetic breakdown near Van Hove singularities (VHSs) in the electron-doped rhombohedral tetralayer
graphene, where
chiral superconductivity has recently been reported. Using the noninteracting band structure and Kubo formula, we identify anomalous Shubnikov-de Haas effects: Ring-like structures in the Landau fan and anomalous high-frequency peaks in the frequency spectra. These anomalous
quantum oscillations can be understood by the reconstruction from
magnetic breakdown among three nearby
Fermi pockets separated by VHSs. Remarkably, these qualitative anomalous features persist into a stronger-VHS regime, where the semiclassical picture breaks down. The temperature and (weak) disorder dependence of the oscillations are also investigated. Our results establish that the
magnetic-breakdown-induced anomalous
quantum oscillation provides a general distinctive probe for the underlying
Fermi-surface geometry associated with VHSs and may explain the recent
quantum oscillation experiment in rhombohedral tetralayer
graphene [arXiv:2606.05356].
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Strongly Correlated Electrons
Quantum-Geometric Raman Response in Multiorbital Flat-Band Systems
Wai Ting Tai and Martin Claassen
Flat-band materials host rich collective phenomena, yet a complete theory of their signatures in inelastic light scattering remains lacking. While naive theories of interacting flat bands would predict that Raman scattering vertices vanish identically in the limit of vanishing dispersion, we show that this picture is incomplete upon including the multiorbital character of such systems. We show that virtual interband processes generate a finite subgap Raman vertex controlled by the
quantum geometric tensor even in the strict flat-band limit. We develop a systematic perturbative theory for Raman scattering from flat bands in the limit where the
photon energy is far from resonance with interband transitions. Treating interband Coulomb scattering and light-matter coupling on equal footing, we decompose the Raman scattering vertices into an interaction-independent
geometric term expressible directly in terms of the
quantum geometric tensor, together with effective resonant and non-resonant pieces generated by virtual interband Coulomb scattering. We then study the polarization-resolved Raman response from collective excitations of an interacting flat band with nontrivial
quantum geometry, and demonstrate quantitative agreement of our framework with a full multi-orbital calculation at large
photon detuning from interband transitions. These results establish
quantum geometry as an intrinsic contribution to inelastic light scattering in flat-band systems, and suggest polarization-resolved Raman spectroscopy as a
quantum geometry-sensitive probe of the collective excitations of correlated flat-band platforms.
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Materials Science
Materials Behavior as Mechanism Ensembles: A Probabilistic Framework for Emergent Behaviors
Brad L. Boyce, Mitchell A. Wood, Krishna Garikipati et al. (+16 more)
Materials behavior is often treated as a deterministic mapping from structure to properties, yet many important phenomena emerge from the conditional activation of multiple mechanisms across scales. This is especially evident in fatigue of metals, where crack growth is typically modeled as monotonic and irreversible process, despite evidence that local microstructure, loading history, and competing unit processes can shift the balance among propagation, arrest, and self-healing. Here we present a probabilistic framework that describes materials behavior as an ensemble of constituent mechanisms whose activation, interaction, and
evolution determine emergent outcomes. The framework connects mechanism activation, state
evolution, and macroscopic observables in a probabilistic way. In the case of fatigue crack propagation, it reframes damage tolerance as an inference problem over mechanism competition and provides a basis for integrating multiscale simulation,
multimodal characterization, and machine learning. The same logic extends to other physical and chemical systems suggesting a portable framework for any system in which emergent behavior reflects mechanism competition under changing conditions. The broader ambition of this perspective review is a shift from correlating structure and performance after the fact to identifying, in advance, the conditions that make desired emergent behavior probable.
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All authors Brad L. Boyce, Mitchell A. Wood, Krishna Garikipati, Andreas E. Robertson, Jeffrey Larson, Ishan Srivastava, Bert Debusschere, Saaketh Desai, Prasad Iyer, Pieterjan Robbe, Mathew Cherukara, Todd Munson, Ming Du, Trupti Mohanty, David J. Gardner, Laurent Capolungo, Benjamin A. Jasperson, Jingye Tan, Rémi Dingreville
Mesoscale and Nanoscale Physics
Inhomogeneous saturation of excitons in monolayer transition-metal dichalcogenides
Blake T. Hipsley, Adam Alfrey and Steven T. Cundiff
We observe that the apparent inhomogeneous broadening, as measured by two-dimensional coherent spectroscopy (2DCS), of the
exciton resonance in transition-metal dichalcogenide monolayers depends on the excitation strength. A key strength of 2DCS is the ability to separate inhomogeneous broadening, which primarily contributes to the diagonal linewidth, from homogeneous broadening, which dominates the cross-diagonal linewidth. We show that the fluence dependence of the diagonal linewidth arises from the effective saturation fluence varying with the
exciton's resonance energy, i.e., inhomogeneous saturation. These results are critical for interpreting the
exciton linewidths, which are often used as a measure of sample quality.
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Strongly Correlated Electrons
Direct minimization versus iterative embedding in the ghost-Gutzwiller method: a comparative study of magnetism in Mott insulators
Antonio Maria Tagliente, Ivan Pasqua and Michele Fabrizio
Accurately describing a hypothetical
symmetry-invariant Mott
insulator presents a long-standing ing challenge in iterative
quantum embedding methods. We address this issue within the ghost- Gutzwiller method, which can be solved either through an iterative
embedding scheme, analogous to dynamical mean-field theory, or by directly minimizing its variational energy functional. Across the Mott transition of the single-band Hubbard model, these formally equivalent approaches behave very differently: the iterative scheme is computationally efficient but fragile, necessitating ad-hoc recipes in the Mott phase that fail in a Zeeman field, leading to a discontinuous energy and a spurious fully-polarized
insulator. Direct minimization avoids these artifacts, stabilizing a genuinely paramagnetic solution. Conversely, when
symmetry breaking is allowed, as in an
antiferromagnetic phase, the iterative scheme yields the correct solution, closely aligning with dynamical mean-field theory. Our findings delineate the conditions under which the iterative
embedding can be trusted and when direct minimization is instead required.
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Superconductivity
Momentum Structure of Superconductivity and Sublattice Effects from Quasiparticle Interference in CsV$_3$Sb$_5$
Aaron G. Greenberg, Xinze Yang, Junze Deng et al. (+11 more)
Quantum interference encoded in the sublattice texture of kagome Bloch wavefunctions has been widely invoked as a route to correlated states, including
chiral charge order, unconventional superconductivity, and their possible intertwining in pair-density-wave (PDW) states. Using sub-Kelvin scanning tunneling microscopy, we conducted spectroscopic mapping of the kagome material CsV$_3$Sb$_5$ with high energy resolution and dense energy sampling through the superconducting gap. Quasiparticle interference (QPI) analysis, aided by ab initio and
symmetry calculations, reveals an isotropic superconducting gap on the
Fermi surfaces derived from V $M_z$-even ($M_z^+$) $d$ orbitals, thereby constraining possible gap
symmetries and limiting any gap anisotropy to the remaining V $M_z$-odd ($M_z^-$) and Sb $p_z$ bands. Meanwhile, the CDW-peak-selected d$I$/d$V$ spectra closely track the spatially averaged density of states and show no distinct enhancement restricted to subgap energies, which do not support an additional PDW modulation within our sensitivity. Finally, the selective absence of specific QPI scattering vectors points to a spectroscopic sensitivity to sublattice character on the
Fermi surface. Together, these results provide a clearer experimental picture of the low-energy electronic structure relevant to kagome superconductivity in CsV$_3$Sb$_5$.
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All authors Aaron G. Greenberg, Xinze Yang, Junze Deng, Pranab Kumar Nag, Kirsty Scott, Yi Jiang, Haoyu Hu, Chandra Shekhar, Dong Chen, Claudia Felser, Santiago Blanco-Canosa, Päivi Törmä, B. Andrei Bernevig, Eduardo H. da Silva Neto
Strongly Correlated Electrons
Interaction-induced sign reversal of the orbital magnetic susceptibility in Chern insulators
Ke Huang and Xiao Li
It has been well established that the orbital magnetization of interacting electrons can be simply evaluated by applying the single-particle formula to self-consistent HF bands. However, we show that such procedure fails qualitatively for orbital
magnetic susceptibility, especially in topological systems: in a Chern-insulating phase of twisted MoTe$_2$, the interaction-induced correction reverses the sign of the susceptibility. This result follows from an algebraic framework that solves the HF problem at finite
magnetic field, where noncommuting canonical momenta obstruct a direct calculation: a reverse Peierls substitution maps every
magnetic-translation-invariant operator to a unique bivariate function, converting the finite-field self-consistency into a function equation that can be expanded systematically in $B$. At first order, this yields a linear equation for the field-induced change $\delta X$ of the Fock potential, leading to an intrinsically interaction-induced susceptibility in addition to a single-particle-like one. The framework reproduces the Středa formula for
insulators, and an auxiliary-
Hilbert-space construction carries it to periodic and moiré systems. Finite-field HF calculations in a gapped Dirac model and in the twisted-MoTe$_2$ Chern
insulator confirm the theory quantitatively.
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Materials Science
Formation of $\mathrm{L}1_2$-ordered $\gamma'$-$\mathrm{Ni}_3\mathrm{Al}$ precipitates in ternary Cu-Ni-Al alloys modelled using an ab initio concentration wave theory and atomistic simulations
Christopher D. Woodgate, Hubert J. Naguszewski, Samuel L. Deacon et al. (+4 more)
Precipitation-strengthened Cu-Ni-Al
alloys are of interest for technological applications because coherent, $\mathrm{L}1_2$-ordered $\gamma'$-$\mathrm{Ni}_3\mathrm{Al}$ precipitates can confer high mechanical strength while allowing the material to retain many of the good transport properties characteristic of elemental Cu. In this work, we study the thermodynamics and phase stability of the pseudobinary $\textrm{Cu}_x (\textrm{Ni}_{3/4} \textrm{Al}_{1/4})_{1-x}$ system, $0 \leq x \leq 1$. We use a computational modelling framework combining first-principles electronic structure calculations with a concentration wave analysis from which atom-atom effective pair interactions are extracted for use in atomistic Monte Carlo simulations. Our modelling reveals three distinct, composition-dependent regimes of phase behaviour, in qualitative agreement with the experimentally determined phase diagram. At low Cu content, Cu is soluble in the $\mathrm{L}1_2$-ordered $\mathrm{Ni}_3\mathrm{Al}$ phase, with a single identifiable phase transition corresponding to chemical ordering between Ni and Al. At intermediate compositions, this high-temperature ordering is followed at lower temperatures by phase separation of Cu and $\mathrm{L}1_2$-ordered $\mathrm{Ni}_3\mathrm{Al}$. Finally, at high Cu content, $\mathrm{L}1_2$-ordered $\mathrm{Ni}_3\mathrm{Al}$ precipitates directly from the solid solution, with no clearly identifiable secondary transition. We relate these phase transformations to features of the underlying electronic structures of the considered
alloys. Overall, this work demonstrates a computationally efficient workflow capturing both chemical ordering and coherent precipitation in multicomponent substitutional
alloys, with relevance to the study of phenomena such as precipitation strengthening.
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All authors Christopher D. Woodgate, Hubert J. Naguszewski, Samuel L. Deacon, Mathys P. Potel, Ján Minár, David Quigley, Julie B. Staunton
Quantum Gases
Engineering SU($N$)-Symmetric Hubbard Models with Microwave-Shielded Dipolar Molecules
Jing-Lun Li, Ragheed Alhyder, Andreas Schindewolf et al. (+3 more)
Ultracold polar molecules provide strong, long-range interactions that microwave shielding makes tunable and nearly
nuclear-
spin independent, giving an emergent SU($N$)
symmetry. However, extended Hubbard models of polar molecules in optical
lattices lack, so far, controllable finite on-site interactions, a key ingredient of strong correlated physics. We show that tuning the Rabi frequency of the microwave coupling can bring two individual molecules (monomers) on neighboring
lattice sites into resonance with a field-linked dimer (doublon) on one of the sites, enabling coherent doublon–monomer-pair conversion. In this model, we characterize the key Hubbard parameters and the dimer lifetime, demonstrating that the on-site and off-site interactions can be tuned nearly independently through the microwave amplitude and orientation, respectively. Our results provide a roadmap for implementing SU($N$)-symmetric extended Hubbard models with controllable doublon fluctuations, providing access to
quantum-simulation in the strongly dipolar regime.
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All authors Jing-Lun Li, Ragheed Alhyder, Andreas Schindewolf, Kaden R. A. Hazzard, Mikhail Lemeshko, Georgios M. Koutentakis
Superconductivity
Dual Enhancement of Superconductivity in FeSe/SrTiO3 via Orbital and Correlation Synergy
Guihao Jia, Jingming Yan, Yucong Peng et al. (+5 more)
In iron-based
superconductors, the dz2 orbital band typically resides far below the
Fermi level and has not been considered to participate in Cooper pairing. Here, using monolayer FeSe/SrTiO3 as a model system, we demonstrate that tip-induced tensile strain controllably shifts the dz2 band toward the
Fermi level, driving a two-stage enhancement of superconductivity. In-plane
lattice expansion first enhances electronic correlation, amplifying superconductivity in the initial stage. As strain further increases, the upward-shifted dz2 band hybridizes with the dxy band, reconstructing the pairing-active d-orbital bands and inducing a secondary, stronger gap enhancement. Collectively, these two stages enlarge the superconducting gap from 17.8 to 23.6 meV. Throughout this process, invariant
Fermi wave vectors confirm that the enhancement originates from band renormalization and reconstruction rather than carrier doping. Our work establishes a route to tailor superconducting states via strain-activated electronic correlations and band engineering, and reveals a previously unrecognized orbital-selective pairing mechanism with broad implications for correlated multiband
superconductors.
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All authors Guihao Jia, Jingming Yan, Yucong Peng, Shendong Su, Pei Ouyang, Xiaopeng Hu, Qi-Kun Xue, Wei Li
Materials Science
No band gap, no problem: Defects in InAs using a band-avoiding occupation-constrained density functional theory
Peter A. Schultz, Arthur H. Edwards, Evan M. Anderson et al. (+2 more)
Density functional theory (DFT) underestimates the experimental band gap—the infamous band gap problem. As the band gap defines the energy scale of defect levels, this complicates computation of charge transition energies for atomic defects. In the extreme case of narrow-gap
semiconductors, the DFT band gap collapses to zero, seemingly precluding quantitative predictions of defect levels. We present a band-avoiding occupation-constrained DFT (ba-occ-DFT) approach that prevents spurious occupation of band-edge states and enables reliable total energy calculations of atomic defects. Application to indium arsenide (InAs) shows that ba-occ-DFT circumvents the band gap problem, separates band-edge errors from defect level calculations, and enables rigorous defect level predictions in a narrow-gap
semiconductor despite a zero DFT band gap.
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All authors Peter A. Schultz, Arthur H. Edwards, Evan M. Anderson, Anthony C. Knighton, Leopoldo Diaz
Mesoscale and Nanoscale Physics
Angular Momentum Transfer in Magnetic Weyl Semimetal Spheres
Adriano Biondo and Francesco M. D. Pellegrino
In this work, we investigate the problem of electromagnetic angular momentum within the framework of topological materials, described by
axion electrodynamics. Specifically, we calculate the electromagnetic angular momentum for a spherical sample of
magnetic Weyl semimetal in the presence of a point charge. We then analyze how, by moving the point charge quasi-statically, the angular momentum stored in the electromagnetic field can be converted into mechanical angular momentum of the sphere. Finally, we derive analytical expressions for the resulting angular velocity and angular displacement, demonstrating that the effect is enhanced in the Weyl semimetal compared with a topological
insulator.
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Soft Condensed Matter
Twist-driven helical flattening in nematic elastomer cylinders
Alexia Chatzitheodorou and Christian D. Santangelo
Liquid Crystal elastomers (LCEs) deform anisotropically along a prescribed nematic director field, making them promising candidates for programmable shape change. Existing studies have primarily focused on either director patterns on flat sheets or simple patterns on curved geometries, leaving the case of a non-trivial director on a non-trivial geometry still largely unexplored. Many biological systems, however, have both complex geometries and complex helical fiber architectures. To explore the interplay between director and underlying geometry, we use a non-Euclidean plate theory for nematic elastomers with a through-thickness twisted director to develop an effective 2D model. With a fixed twist angle, our model shows an anomalous coupling between mid-surface
curvature and director twist. This emergent term arises from the interplay between orientational order and elasticity, and dominates traditional bending contributions. To illustrate the general theory, we study the stability of cylindrical shapes with through-thickness twist. We find that the cylinder is unstable to a long-wavelength helical flattening mode and determine the critical parameter for the onset of instabilities.
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Disordered Systems and Neural Networks · Cross-listed from cs.LG
Equilibrium Training of Energy-Based Models with Parallel Trajectory Tempering
Nicolas Béreux, Aurélien Decelle, Cyril Furtlehner et al. (+1 more)
Energy-Based Models (EBMs) provide an interpretable framework for generative modeling of scientific data, but poor Markov Chain Monte Carlo mixing often limits their reliability. We introduce a training
algorithm based on Parallel Trajectory Tempering (PTT), which exploits the continuity of the optimization path to maintain
equilibrium sampling throughout learning. This enables stable and fast training on highly
multimodal and data-scarce scientific
datasets. Combined with reservoir sampling and adaptive optimization, PTT has a computational cost comparable to Persistent Contrastive Divergence, making it a practical replacement for standard training methods. It also provides direct estimates of thermalization times,
equilibrium samples from trained models, and accurate log-likelihoods at essentially no additional cost. Experiments on Restricted Boltzmann Machines show that PTT consistently outperforms existing EBM training approaches. On discrete tabular data, it also surpasses state-of-the-art deep generative models, yielding higher-quality samples and greater robustness to overfitting and limited data. Our results make
equilibrium maximum-likelihood training of EBMs practical and computationally efficient.
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All authors Nicolas Béreux, Aurélien Decelle, Cyril Furtlehner, Beatriz Seoane
Mesoscale and Nanoscale Physics
A Degenerate Singlet-Triplet Qubit with All-Electrical Orthogonal Control
Phuong X. Nguyen, Konstantinos Tsoukalas, Jann H. Ungerer et al. (+8 more)
Singlet-triplet
qubits offer an attractive encoding for
semiconductor quantum computing, combining ancilla-free readout, reduced sensitivity to common-mode noise, and baseband voltage control. However, the Zeeman energy difference $\Delta E_\mathrm{Z}$ is typically fixed by local
magnetic field gradients or $g$-factor inhomogeneities, leaving the exchange interaction $J$ as the only dynamically tunable parameter. This always-on $\Delta E_\mathrm{Z}$ precludes orthogonal control of the
qubit's rotation axes and introduces unwanted state rotations during idling. Here we demonstrate all-electrical orthogonal control of a degenerate singlet-triplet (DST)
qubit formed by two hole
spins in a germanium double
quantum dot. Exploiting the electrically tunable anisotropic $g$-factors of the two
spins, we identify a regime where both $\Delta E_\mathrm{Z}$ and $J$ vanish, making the $S$ and $T_0$ states degenerate at the idle point. By applying only baseband voltage pulses, we independently control both $J$ and $\Delta E_\mathrm{Z}$, enabling fully orthogonal $Z$- and $X$-axis rotations. Randomized benchmarking yields an average physical single-
qubit gate fidelity of 99.53% for a gate duration of approximately 100 ns. Finally, we electrically tune the degenerate point across a wide range of
magnetic field orientations, enabling operation in a regime of enhanced coherence time and offering a route towards multi-
qubit scaling under a shared global
magnetic field.
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All authors Phuong X. Nguyen, Konstantinos Tsoukalas, Jann H. Ungerer, Julian Santen, Valentin John, Stefan D. Oosterhout, Lucas Stehouwer, Stefano Bosco, Giordano Scappucci, Menno Veldhorst, Amir Yacoby
Statistical Mechanics
Neural variational framework for random Young-diagram limit shapes
Qian Chen and Bo-Xuan Ge
We develop a structure-preserving neural variational framework for random Young-diagram ensembles, with representations adapted to the structure and scaling of each measure. The method is validated on the Plancherel, uniform, minimal-difference, and fixed-\(q\) \(q\)-Plancherel ensembles, using known asymptotic profiles only for post-training comparison. We then study a quartically deformed hook-length ensemble without assuming an analytical saddle shape. Large-\(n\) neural profiles are compared with finite-size MAP profiles obtained from exact-action searches and with mean profiles obtained from corner-transfer Metropolis–Hastings sampling. Increasing the deformation suppresses the leading rows and broadens the support, while the neural, discrete, and sampled mean profiles agree at the percent level. These results provide numerical evidence for a deformation-dependent macroscopic saddle family.
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Statistical Mechanics
Temporal Interference from Topological Transitions in Monitored Quantum Dynamics
Qingyuan Wang, Ruoyu Yin and Eli Barkai
Quantum interference is conventionally associated with the coherent superposition of alternative paths. We uncover a temporal form of interference in repeatedly monitored
quantum systems, appearing directly as fringes in the
stochastic first-detection-time distribution. This temporal interference becomes remarkably long lived near a class of topological transitions at which a pair of dark states emerges in
Hilbert space. Close to such transitions, the corresponding quasi-dark modes dominate the late-time dynamics and interfere coherently, producing pronounced temporal fringes whose decay becomes arbitrarily slow upon approaching the transition. We identify the
symmetry conditions underlying this mechanism and relate the fringe frequency to the energy spectrum of the
Hamiltonian. Our results reveal how the interplay of
quantum superposition, topological transitions, and dark-state formation generates long-lived temporal interference in monitored
quantum dynamics.
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Strongly Correlated Electrons
Interactions between structural and magnetic domains through the Verwey transition in stoichiometric and doped magnetite
Mateusz Ślęzak, Zbigniew Kąkol, Ryszard Zalecki et al. (+5 more)
The
magnetic response of magnetite as it cycles through the Verwey transition at $T_{\rm V}\approx 120$ K remains incompletely understood, despite numerous studies of both structural and
magnetic domains. For example, although the alternating-current susceptibility increases upon heating through the Verwey temperature $T_{\rm V}$, the magnetization may either increase or decrease. Since many intertwined processes occur at $T_{\rm V}$, a multifaceted view of the
magnetic changes may help clarify the nature of these processes and establish specific features of the transition as diagnostic tools. To this end, we report measurements of the
magnetic response of magnetite upon heating through $T_{\rm V}$ under a wide range of applied-field conditions. We studied synthetic stoichiometric and doped (Zn, Ti, and Al) single
crystals, as well as a natural polycrystalline sample, with the aim of explaining how and why the magnetization changes as a function of temperature through $T_{\rm V}$. The
magnetic-field-induced reorientation of the monoclinic $c$ axis may broaden the transition, primarily in stoichiometric magnetite. These findings help clarify the mechanism of the transition.
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All authors Mateusz Ślęzak, Zbigniew Kąkol, Ryszard Zalecki, Andrzej Kozłowski, Naveen Kumar Chogondahalli Muniraju, Neven Barišić, Stuart Gilder, Wojciech Tabiś
Mesoscale and Nanoscale Physics
Anisotropic Spin Polarization and magnetic spin hall effect in Ferromagnets
Jiabin Wang, Zhenhua Zhang, Wancheng Zhang et al. (+4 more)
Spin-dependent transport in ferromagnets underpins the development of high-density spintronic
memories.
Spin-dependent transport in strong
spin-orbit-coupled ferromagnets exhibits a significant anisotropy. Both the overall
spin polarization during charge transport and the
magnetic spin Hall conductivity are found to exhibit pronounced anisotropy when the magnetization is tilted away from the crystallographic easy axis or when the electric field is rotated relative to the
crystal axes. These anisotropic responses originate primarily from
spin-orbit coupling, which is identified as the key driver of the large anisotropy observed in ferromagnet. Furthermore, strain tunability of the
magnetic spin Hall anisotropy is demonstrated, with tensile strain progressively enhancing the oscillatory amplitude of the
spin Hall conductivity. These findings establish strong
spin-orbit-coupled ferromagnets as a platform for anisotropic
spin-current generation and field-free spintronic devices that exploit intrinsic material anisotropy for improved performance and energy efficiency.
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All authors Jiabin Wang, Zhenhua Zhang, Wancheng Zhang, Jianxiong Zhao, Yong Liu, Rui Xiong, Zhihong Lu