Strongly Correlated Electrons
Studying 3D O(N) Surface CFT on the Fuzzy Sphere
Jiechao Feng and Taige Wang
Boundary conformal field theory (BCFT) provides a universal framework for critical phenomena in the presence of boundaries. We determine BCFT data for the normal and ordinary boundary universality classes of the $1+1$-dimensional boundaries of the $2+1$-dimensional $O(2)$ and $O(3)$ Wilson-Fisher fixed points, realized microscopically by a
bilayer Heisenberg model on the fuzzy sphere. Using the fuzzy-sphere state-operator correspondence, we obtain boundary operator spectra, identify low-lying boundary primary operators, extract operator-product-expansion (OPE) data, and estimate the boundary central charges for both boundary conditions. For the normal boundary condition, the universal amplitudes $a_\sigma$ and $b_t$ extracted from one- and two-point functions agree quantitatively with Monte Carlo
benchmarks where available. For both $N=2$ and $N=3$, we find a positive extraordinary-log exponent $\alpha$, providing independent microscopic evidence for extraordinary-log boundary criticality. Our results extend fuzzy-sphere BCFT spectroscopy beyond the Ising universality class to continuous $O(N)$
symmetry.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
A rigorous quasipolynomial-time classical algorithm for SYK thermal expectations
Alexander Zlokapa
Estimating local observables in Gibbs states is a central problem in
quantum simulation. While this task is BQP-complete at asymptotically low temperatures, the possibility of
quantum advantage at constant temperature remains open. The Sachdev-Ye-Kitaev (SYK) model is a natural candidate: at any constant temperature, its Gibbs states have
polynomial quantum circuit complexity and are not described by Gaussian states. Rigorous analyses of the SYK model are difficult due to the failure of known techniques using random
matrix theory, cluster expansions, and rigorous formulations of the
quantum path integral and replica trick. Despite this, we give a rigorous proof of a quasipolynomial-time classical
algorithm that estimates SYK local thermal expectations at sufficiently high constant temperature. Our result introduces a new Wick-pair cluster expansion that we expect to be broadly useful for disordered
quantum many-body systems.
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Materials Science
Generative Discovery of Magnetic Insulators under Competing Physical Constraints
Qiulin Zeng, Tahiya Chowdhury and Md Shafayat Hossain
Discovering materials that must simultaneously satisfy multiple competing constraints remains a central challenge in computational materials design, particularly in data-scarce regimes where conventional data-driven approaches are least effective.
Magnetic insulators represent a stringent example: the electronic conditions that favor
magnetic order often also promote
metallicity, while insulating behavior suppresses the interactions that stabilize magnetism. As a result, experimentally viable
magnetic insulators are rare and difficult to identify through conventional screening. Here, we introduce MagMatLLM, a constraint-guided generative discovery framework that integrates
language-model-based
crystal generation with evolutionary selection, surrogate screening, and first-principles validation to target simultaneous stability, magnetism, and insulating behavior. Unlike stability-first approaches, the framework enforces functional constraints during generation and selection, steering the search toward sparsely populated regions of materials space defined by competing physical requirements. Using this workflow, we identify twelve previously unreported candidate
magnetic insulators, including Tm$_4$Co$_2$Cr$_2$O$_{12}$ and Cr$_4$Nb$_2$O$_{12}$. Of these, ten are dynamically stable by
phonon analysis and exhibit finite band gaps and nonzero
magnetic moments in
spin-polarized density functional theory calculations. Beyond the specific compounds identified here, this work establishes a general constraint-guided paradigm for multi-objective materials discovery in sparse chemical spaces and provides a transferable strategy for the design of
quantum materials under competing physical constraints.
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Materials Science
Accelerating point defect simulations using data-driven and machine learning approaches
Arun Mannodi-Kanakkithodi, Menglin Huang, Prashun Gorai et al. (+1 more)
Point defects in solid-state materials are now routinely simulated using large supercell structures, requiring efficient
quantum mechanical solutions. Data-driven and machine learning (ML) models trained on computational data can enable rapid defect property predictions and high-throughput screening. In this article, we provide an overview of prominent efforts to accelerate defect simulations using these approaches. We begin by discussing the motivations for data-driven techniques in defect modeling, and describe efforts over the past decade to use descriptor-based models for rapid screening of defect properties – most notably in
oxides. In particular, we discuss case studies where surrogate models and interatomic potentials were trained on density functional theory (DFT) data, leading to predictions with
quantum-mechanical accuracies at a fraction of the cost. In addition to geometry relaxation and formation energy predictions, these interatomic potentials are capable of predicting
phonon modes and vibrational free energies to yield defect energetics at finite temperatures – representing a key frontier for computational defect research. We finish with a discussion on how to connect these approaches and their outputs with experimental data, and provide an outlook on this burgeoning sub-field.
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All authors Arun Mannodi-Kanakkithodi, Menglin Huang, Prashun Gorai, Seán R. Kavanagh
Materials Science
Expanding the extreme-k dielectric materials space through physics-validated generative reasoning
Hossain Hridoy, Tahiya Chowdhury and Md Shafayat Hossain
The most technologically consequential materials are often the rarest: they occupy narrow regions of chemical space, obey competing physical constraints, and appear only sparsely in existing databases. High-kappa dielectrics, high-Tc
superconductors, and
ferromagnetic insulators are to name a few. This scarcity fundamentally limits today's data-driven materials discovery, where machine-learning models excel at interpolation but struggle to generate genuinely new candidates. Here, we introduce DielecMIND, an artificial intelligence framework that reframes materials discovery as a
reasoning-driven exploration instead of a database-screening problem. Using high-kappa dielectrics as a data-scarce and technologically stringent test case, DielecMIND combines large-
language-model hypothesis generation for the first time with physics validated first-principles calculation to navigate chemical space beyond known compounds. Prior to our work, only 14 experimentally or computationally validated materials with kappa > 150 were known. Our framework discovers and validates 5 new such compounds, expanding this rare-materials class by a remarkable = 35% in a single study. Among them, we find that Ba2TiHfO6 exhibits a dielectric constant of 637, minimal loss at low optical frequencies, and stability up to 800 K. Beyond dielectrics, this work demonstrates a new paradigm for artificial-intelligence-guided discovery: one that generates a small number of physically grounded, experimentally plausible candidates yet measurably expands sparsely populated functional materials spaces. Thus, DielecMIND points toward a general strategy for discovering rare, high-impact functional materials where data scarcity has long constrained progress.
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Materials Science
Evolution of the Saddle Point in Antimony Telluride Homologous Superlattices
Yi-Hsin Shen, Shane Smolenski, Ming Wen et al. (+13 more)
Combining topological
insulators with topological semimetals in the form of homologous superlattices is a promising approach for generating correlated
quantum matter based upon
Fermi level
alignment with band extrema. For antimony telluride, a saddle point is predicted to occur at the M-point, while antimonene layering is predicted to move the M-point valence band towards the
Fermi level. To date, the predicted saddle point at the M-point has not yet been demonstrated, and studies of antimony telluride homologous superlattices have been limited to one or two layers of antimonene added to antimony telluride. Here, we present scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy studies of a series of antimony telluride homologous superlattices with two to four layers of antimonene. In addition to demonstrating the presence of a saddle point and associated van Hove singularity near the M-point, we identify the key role of Sb and Te $p_z$ orbital hybridization in driving the van Hove singularity toward the
Fermi level.
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All authors Yi-Hsin Shen, Shane Smolenski, Ming Wen, Yimo Hou, Eoghan Downey, Jakob Hammond-Renfro, Katharine Moncrieffe, Chun Lin, Makoto Hashimoto, Donghui Lu, Kai Sun, Dominika Zgid, Emanuel Gull, Pierre Ferdinand P. Poudeu, Na Hyun Jo, Rachel S. Goldman
Soft Condensed Matter
Orientation Dynamics of Gyrotactic Microswimmers in Turbulent Flows
Suraj Kumar Nayak, Vishwanath Shukla and Akshay Bhatnagar
We study the dynamics of gyrotactic microswimmers suspended in homogeneous and isotropic
turbulence by using direct numerical simulations (DNS). The swimmers are characterized by three non-dimensional parameters: their aspect ratio ($\gamma$), a dimensionless swimming speed ($\phi$), and a dimensionless reorientation time ($\psi$). Strong gyrotaxis (smaller $\psi$) promotes vertical
alignment of the swimmers, while weak gyrotaxis leads to nearly isotropic orientations. At low swimming numbers, the orientation distribution is largely shape-independent with spheres and spheroids showing marginally greater vertical
alignment than rods, whereas at higher activity the peaks of the distributions exhibit largely shape-independent behavior and the tails show a clear dependence on particle shape. However, at large $\psi$ rods exhibit a stronger
alignment along the vertical. We observe that at small $\psi$ the rod-shaped swimmers respond to shear by aligning with the stretching direction of the strain-rate tensor, while at large $\psi$ the
alignment with the vorticity vector is preferred. The orientation autocorrelation is found to decay exponentially, with a decay rate that scales as $1/(2\psi)$. Analysis of the mean-squared displacement (MSD) reveals a transition from a ballistic motion at short times to a diffusive regime at longer times. To assess the efficiency of vertical migration, we compute the probability distributions of vertical displacement over a fixed time interval and the time taken to migrate a specific vertical distance. Furthermore, we use a simplified two-dimensional model for spherical swimmers that qualitatively reproduces the key trends observed in the full three-dimensional (3D) simulations.
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Strongly Correlated Electrons
Giant spontaneous Kerr effect and its self-doping dependence in altermagnetic MnTe
Weitung Yang, Choongjae Won, Cory Cress et al. (+9 more)
Altermagnetism, a third class of collinear magnetism with
spin-split bands and vanishing net magnetization, has emerged in hexagonal {\alpha}-MnTe, a promising platform for ultrafast, stray-field-free spintronics. Whether MnTe's macroscopic
symmetry-breaking signatures reflect ideal altermagnetic order or are activated by defects remains open. Here we report
giant spontaneous Kerr rotations of up to 1500 rad in {\alpha}-MnTe single
crystals at the telecommunication wavelength of 1550 nm, onsetting precisely at the Néel temperature TN = 307 K. The signal appears in disjoint macroscopic patches whose amplitude tracks the sample conductivity, and a hole-conducting {\alpha}-MnTe film reproduces this response together with an anomalous
Hall effect. Within a single
crystal, Kerr-active regions are optically distinct from their Kerr-silent surroundings in co-registered reflection maps. These observations indicate that carrier self-doping, rather than ideal altermagnetic order alone, governs the
giant magneto-optical response, and establish telecom-wavelength Kerr imaging as a practical readout for altermagnetic spintronics.
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All authors Weitung Yang, Choongjae Won, Cory Cress, Weihang Lu, Xiaochen Fang, Shelby Fields, Nicholas Combs, Shaofeng Han, Marshall Zachary Franklin, Steven P. Bennett, Sang-Wook Cheong, Jing Xia
Statistical Mechanics
Local Electroneutrality Violation as a Universal Constraint in Confined Electrolytes
M. Lozada-Cassou
We show that finite-size violations of local electroneutrality in confined electrolytes are governed by the
topology of the confining domain, yielding a universal hierarchy of deviations across spherical, cylindrical, and planar geometries. Within Poisson-Boltzmann theory, we introduce an electroneutrality deviation ratio that quantifies how global electrostatic constrains associated with compacness and boundary multiplicity modify charge balance inside confined domains. Although electroneutrality is asymptotically restored in all geometries, finite-size deviations are strongest in compact spherical cavities, weaker in cylindrical confinement, and weakest in planar slits. These results identify
topology as the structural origin of confinement-induced charge redistribution and stablish the violation of local electroneutrality as global constraint underlying phenomena such as overcharging anf charge reversal, demostrating that confinement-not local-not local
geometric details-controls the emergence of these effects.
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Soft Condensed Matter
Element-deletion-enhanced digital image correlation for automated crack detection and tracking in lattice materials
Alessandra Lingua, Arturo Chao Correas, François Hild et al. (+1 more)
Architected materials can exhibit remarkable combinations of stiffness, strength, and toughness, yet their application is currently limited by an incomplete understanding of how cracks initiate and propagate through their discrete architecture. Elucidating the mechanisms that underpin these processes is challenging because
lattice failure is governed by highly localized deformations of slender beams, which fall outside the resolution and assumptions of optical methods developed for continuum solids, such as digital image correlation (DIC). Thus, characterizing crack propagation within
lattice materials requires measurement strategies capable of resolving
lattice-scale deformations while accounting for both the intrinsic discreteness of
lattice architectures and the progressive formation of material discontinuities during failure. This work introduces a global DIC framework tailored to architected materials, in which the correlation problem is solved directly on the
lattice mesh and damaged elements are automatically removed during the analyses. Damage detection, which relies on a data-driven residual criterion, enables the robust tracking of localized deformation and crack-tip motion under different testing conditions. The method provides physically consistent displacement field measurements on the evolving intact
lattice topology and resolves the crack path over time. Validations on 3D-printed regular and imperfect triangular
lattices under mode-I loading demonstrate that the approach accurately captures both damage initiation and crack propagation. Furthermore, we demonstrate that identifying damaged elements provides an estimate of the critical failure strain, which can be used directly in numerical models or adopted as an alternative element-deletion threshold in DIC analyses.
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All authors Alessandra Lingua, Arturo Chao Correas, François Hild, David S. Kammer
Statistical Mechanics · Cross-listed from quant-ph
Ansätz Expressivity and Optimization in Variational Quantum Simulations of Transverse-field Ising Model Across System Sizes
Ashutosh P. Tripathi, Nilmani Mathur and Vikram Tripathi
We explore the application of the Variational
Quantum Eigensolver (VQE) to investigate the ground state properties, particularly the
entanglement entropy, of the Transverse Field Ising Model (TFIM) in one, two, and three dimensions, considering systems of up to 27
spins. By benchmarking VQE results against exact diagonalization and analyzing the
entanglement properties across different system sizes, we assess the
algorithm's effectiveness in capturing faithful ground state. Using results of TFIM, we also investigate how VQE's expressivity and optimization influence the simulation of highly entangled
quantum states. We employ different ansätze: the hardware-efficient EfficientSU2 from Qiskit, the physics-inspired
Hamiltonian Variational ansätz (HVA) and HVA with
symmetry breaking, and
benchmark their performance using energy variance,
entanglement entropy,
spin correlations, and magnetization. We further discuss the implications for scaling these methods to larger
quantum systems.
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Strongly Correlated Electrons
Unconventional Quantum Criticality in Long-Range Spin-1 Chains: Insights from Entanglement Entropy and Bipartite Fluctuations
Justin Tim-Lok Chau, Jiarui Zhao, Nicolas Laflorencie et al. (+1 more)
We study the ground-state phase diagram of a
spin-1 Heisenberg chain with staggered long-range (LR) interactions decaying as $\propto r^{-\alpha}$ using a
quantum Monte Carlo approach based on the split-
spin representation. This formulation enables efficient large-scale simulations by mapping the
spin-1 model onto
spin-$1/2$ degrees of freedom with local projection constraints. We resolve the continuous
quantum phase transition between the gapped Haldane phase at large $\alpha$ (short-range regime) and a gapless antiferromagnetically ordered Néel phase at small $\alpha$ (LR regime), where the continuous SU(2)
symmetry is broken. From finite-size scaling and crossing point analyses, we determine the critical point to be at $\alpha_c = 2.49(1)$ and extract the associated critical exponents, which indicate unconventional criticality. In particular, the transition is found to be nonconformal, characterized by a dynamical exponent $z \neq 1$. We further analyze the scaling of
entanglement entropy and bipartite fluctuations across the transition, and determine the corresponding universal scalings in both phases and at criticality.
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All authors Justin Tim-Lok Chau, Jiarui Zhao, Nicolas Laflorencie, Zi Yang Meng
Statistical Mechanics
Arrow of Time as an indicator of Measurement-Induced Phase Transitions
Nitay Hurvitz, Alon Kochol, Victor Fleurov et al. (+1 more)
Measurement-induced phase transitions (MIPTs) in monitored
quantum systems are typically diagnosed using
entanglement-based measures. Here, we develop a complementary thermodynamic perspective based on the arrow of time (AoT), which arises from the intrinsic irreversibility of the
quantum measurements driving these transitions. We study the AoT - defined as the logarithmic ratio of forward and backward trajectory probabilities - across a family of models exhibiting MIPTs. We find that, like
entanglement entropy, the AoT is a nonlinear functional of the averaged density
matrix; however, in contrast to
entanglement, it is associated with a local operator. To determine whether the AoT exhibits critical behavior, we formulate and exactly solve a model of a random
quantum circuit with non-projective measurements. This allows us to analytically demonstrate that the AoT displays nonanalytic behavior and identify its critical exponent. Our results establish the AoT as a novel diagnostic for phase transitions in monitored
quantum systems.
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All authors Nitay Hurvitz, Alon Kochol, Victor Fleurov, Eran Sela
Disordered Systems and Neural Networks
Autonomous Emergence of Hamiltonian in Deep Generative Models
Wenjie Xi and Wei-Qiang Chen
The unprecedented predictive success of deep generative models in complex many-body systems, such as AlphaFold 3, raises an epistemological question: do these networks merely memorize data distributions via high-dimensional interpolation, or do they autonomously deduce the underlying physical laws? To address this, we introduce a framework to extract the implicit physical interactions learned by generative models. Using the exact equivalence between the zero-noise limit of a
diffusion score field and the thermodynamic restoring force, we directly compare the internal interaction structure of a trained neural network with the physical
Hamiltonian. Applying this framework to a sequence-dependent, frustrated 1D $O(3)$
spin glass, we probe the latent representations of an $O(3)$-equivariant
attention architecture trained solely on thermal
equilibrium snapshots. Without imposing a locality cutoff or configuration independence, the dense scalar
matrix in our architecture develops locality and nearly configuration-independent coefficients that recover the microscopic interactions of the
spin glass with Pearson correlation $0.993$ on $2{,}000$ unseen sequences. This provides quantitative, falsifiable evidence for the emergence of the
Hamiltonian in a deep generative model. Similarly, in an explicit-water phenol experiment, the network is trained only on coordinate data. With sufficient expressive capacity, a molecular-graph-guided Pairformer recovers the dominant bond, angle, and proper-torsion potential-of-mean-force (PMF) sectors. A sector-preserving projection of configuration-dependent coefficients onto constants yields $R_{\rm const}^2=0.9669$ on unseen molecular dynamics (MD), providing molecular-scale evidence for partial emergence of the
Hamiltonian.
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Strongly Correlated Electrons
Gauge-Equivariant Graph Neural Networks for Lattice Gauge Theories
Ali Rayat, Yaohang Li and Gia-Wei Chern
Local gauge
symmetry underlies fundamental interactions and strongly correlated
quantum matter, yet existing machine-learning approaches lack a general, principled framework for learning under site-dependent
symmetries, particularly for intrinsically nonlocal observables. Here we introduce a gauge-equivariant graph neural network that embeds non-Abelian
symmetry directly into message passing via
matrix-valued, gauge-covariant features and
symmetry-compatible updates, extending equivariant learning from global to fully local
symmetries. In this formulation, message passing implements gauge-covariant transport across the
lattice, allowing nonlocal correlations and loop-like structures to emerge naturally from local operations. We validate the approach across pure gauge, gauge-matter, and dynamical regimes, establishing gauge-equivariant message passing as a general paradigm for learning in systems governed by local
symmetry.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Reflections on Quantum Reflectometry: Quantum and Tunneling capacitances as well as Sisyphus and Hermes resistances
O. Yu. Kitsenko, S. N. Shevchenko, L. Peri et al. (+1 more)
When a
quantum electronic device is coupled to an electrical resonator, admittance changes of the
quantum subsystem may be detected. The effective reactance may include capacitive and inductive terms that incorporate
geometric,
quantum, and tunneling components; while the effective resistance may be composed of Sisyphus and Hermes terms linked to relaxation and decoherence, respectively. Such reflectometry is usually studied when all characteristic times of the
quantum system are much shorter than the resonator's period, in which case only stationary
quantum states are probed. We present a rigorous description of a driven-dissipative qudit-resonator system. Our approach demonstrates how to strictly introduce
quantum and tunneling capacitances as well as Hermes and Sisyphus resistances, and how these values are modified when the dynamics of the subsystems becomes mutually dependent. We present the cases of a Cooper-pair box, a single-Cooper-pair transistor, a double
quantum dot, and a single-electron box. Our approach can be applied to describe any
quantum system coupled to any classical resonator.
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All authors O. Yu. Kitsenko, S. N. Shevchenko, L. Peri, Franco Nori
Statistical Mechanics
Encounter times of random walkers with simultaneous resetting on networks
Cristian D. Suarez-Jimenez, Alejandro P. Riascos and Denis Boyer
In this work, we study the dynamics of multiple random walkers on networks subject to a simultaneous resetting protocol, whereby all walkers are synchronously returned to their respective initial nodes. For this collective Markovian process, we derive exact analytical expressions for the mean first-encounter time, defined as the average time required for all walkers to meet for the first time at a given node. These results are formulated in terms of the
eigenvalues and eigenvectors of the transition
matrices governing the dynamics without resetting, providing a clear spectral interpretation of the impact of resetting on encounter processes. We further establish a general criterion for finite networks that determines when the introduction of a nonzero resetting probability reduces the mean first-encounter time and leads to an optimal resetting strategy. The theoretical predictions are illustrated through numerical results on regular and heterogeneous networks, for encounters involving two or more walkers, and for combinations of local and nonlocal dynamics. Our findings demonstrate that simultaneous resetting can significantly reduce encounter times for specific target nodes and initial conditions, while becoming ineffective for highly exploratory dynamics or distant targets. A comparison with independent resetting shows that simultaneous resetting is more efficient in homogeneous networks, whereas independent resetting can outperform it in heterogeneous structures, thereby revealing a trade-off between synchronization and exploration. The framework provides a unified approach to collective search and encounter problems on networks with resetting.
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Superconductivity
Stabilization of a non-superconducting, orthorhombic phase by over-hydrogenating LaFeSiH
M. F. Hansen, C. Lepoittevin, J.-B. Vaney et al. (+7 more)
Chemical composition provides a powerful route to tune the electronic ground state of iron-based
superconductors and other
quantum materials, yet access to highly doped phases remains limited. Here we demonstrate that high-pressure thermal decomposition of hydrogen-rich precursors enables over-hydrogenation of LaFeSi. Using anthracene, we synthesize tetragonal superconducting LaFeSiH, including a single hydrogen site, while ammonia borane yields a structurally distorted over-hydrogenated phase, LaFeSiH1+x, with an orthorhombic structure. Chemical analysis reveal excess hydrogen (x ~ 0.6), implying a second H site in LaFeSiH1.6 whose localization and occupancy are determined by
neutron diffraction. In contrast to metallic LaFeSi and superconducting LaFeSiH, orthorhombic LaFeSiH1.6 exhibits
semiconductor-like behavior. Upon hydrogen release near 100 {\deg}C, it transforms into tetragonal superconducting LaFeSiH1+{\delta} ({\delta} << 0.6). These results establish the chemical flexibility of the layered LaFeSiX (X = H, O, F) family and provide access to a high hydrogen-doping regime, creating new opportunities to investigate superconductivity in Fe-based silicides.
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All authors M. F. Hansen, C. Lepoittevin, J.-B. Vaney, P. Boullay, V. Nassif, A. Sulpice, H. Mayaffre, M.-H. Julien, S. Tencé, P. Toulemonde
Materials Science
Anisotropic multiband magnetotransport in LaAg$_2$Ge$_2$ thin films
Mizuki Ohno, Reiley Dorrian, Veronica Show et al. (+1 more)
ThCr$_2$Si$_2$-type intermetallics are layered conductors in which crystallographic anisotropy and multiband electronic states often give rise to characteristic magnetotransport phenomena. Here, we report the molecular-beam epitaxy growth of LaAg$_2$Ge$_2$ thin films on MgO(001) and their magnetotransport properties. The
Hall effect and magnetoresistance are captured by an effective two-carrier description with a high-mobility electron band, yielding a positive magnetoresistance of 22.5% at 9 T. Angle-dependent magnetoresistance exhibits a dominant twofold anisotropy and additional reproducible dip/peak features at characteristic tilt angles that are nearly independent of field and temperature. These results extend our understanding of the anisotropic electronic transport in thin-film germanides within the ThCr$_2$Si$_2$ family.
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All authors Mizuki Ohno, Reiley Dorrian, Veronica Show, Joseph Falson
Materials Science
Engineering Wake-Up-Free Ferroelectric Capacitors with Enhanced High-Temperature Reliability
Nashrah Afroze, Salma Soliman, Yu-Hsin Kuo et al. (+5 more)
We systematically explore the design space of ferroelectric hafnium-zirconium
oxide (H0.5Z0.5O or HZO)
heterostructures for reliable high temperature operation. HZO films are deposited using thermal and
plasma-enhanced atomic layer deposition (Th-ALD and PE-ALD) on tungsten (W) and titanium nitride (TiN) bottom electrodes (BE), while maintaining identical top electrodes. We demonstrate that PE-ALD HZO capacitors integrated with W BE exhibit wake-up-free switching up to 125C, along with significantly improved endurance compared to Th-ALD HZO/W devices across a wide temperature range (85-125C). By decoupling the contributions of the
plasma-deposited HZO film and the oxidized bottom interface inherently formed during PE-ALD, we identify the oxidized W interfacial layer (WOx) as the primary factor governing endurance enhancement and wake-up suppression at elevated temperatures, while the PE-ALD HZO film provides secondary benefits in reducing wake-up. In contrast, PE-ALD HZO capacitors fabricated on TiN BE show no substantial improvement in wake-up behavior or endurance relative to Th-ALD HZO/TiN devices, despite the formation of an unintentional TiOxNy interfacial layer, and instead exhibit degraded polarization. This difference arises from the significantly weaker endurance enhancement and no wake-up suppression provided by oxidized TiN compared to oxidized W under comparable oxidation conditions. Overall, PE-ALD HZO films enable superior ferroelectric performance at elevated temperatures only when deposited on W BE, while Th-ALD HZO films remain a viable option for high temperature operation on TiN BE. These findings clarify the interplay between deposition technique, electrode chemistry, and interfacial oxidation, and provide design guidelines for integrating ferroelectric
memories into monolithic 3D systems under stringent thermal constraints.
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All authors Nashrah Afroze, Salma Soliman, Yu-Hsin Kuo, Sanghyun Kang, Mengkun Tian, Priyankka Ravikumar, Andrea Padovani, Asif Khan
Strongly Correlated Electrons
Interaction-induced asymmetry in infinite-temperature dynamical correlations of hard-core anyons
Doru Sticlet, Ovidiu I. Pâţu, Balázs Dóra et al. (+1 more)
We study dynamical correlations of interacting hard-core anyons on a one-dimensional
lattice at infinite temperature. This is a setting in which the many-body spectrum is independent of the statistical phase $\theta$, while dynamical correlators remain sensitive to $\theta$ through nonlocal Jordan-Wigner strings. We compute single-particle Green's functions, spectral functions, and density-density correlators, thereby separating the effects of fractional statistics on one-body coherence from those on density transport in a maximally mixed ensemble. In the noninteracting case $V=0$, high-temperature averaging leads to inversion-symmetric Green's functions for all $\theta$ despite the presence of anyonic strings. Finite nearest-neighbor interactions $V$ generate, however, a pronounced left-right asymmetry in the Green's functions for $0<\theta<\pi$, with the strongest chirality appearing at intermediate couplings $V\sim J$ where interactions and hopping compete most effectively. In this regime, the Green's function decays exponentially in time with a statistical-angle-dependent decay rate. At strong coupling, the dynamics crosses over to an atomic-limit regime in which the dependence on $\theta$ is reduced. Here, the Green's function decays universally as $t^{-1}$ and the corresponding spectral function displays a three-band structure. In contrast, density-density correlations are insensitive to statistics and recover the known infinite-temperature transport regimes of the XXZ chain, including ballistic, superdiffusive, and diffusive behaviors. These results identify dynamical correlation functions as direct probes of fractional statistics in high-
entropy quantum systems.
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All authors Doru Sticlet, Ovidiu I. Pâţu, Balázs Dóra, Cătălin Paşcu Moca
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Toward nanophotonic platforms for solid-state $^{229}$Th nuclear clocks
Sandro Kraemer, Karen Mamian, Toby Bi et al. (+18 more)
While the $^{229}$Th
nuclear isomer has recently been observed and
laser-excited, converting optical
nuclear manipulation into a chip-scale solid-state frequency standard remains an open challenge. Here, we present a nanophotonic platform to realize an all-solid-state
nuclear clock based on the low-energy isomeric transition of $^{229}$Th embedded in high-$Q$ fluoride photonic resonators. By coupling ensembles of thorium
nuclei to confined optical modes, we show that resonant field build-up in the cavity can substantially enhance the
nuclear excitation rate, enabling optical interrogation at practical
laser intensities. We model the
nuclei-
photon interaction dynamics and outline a technological roadmap toward addressing this challenge, including resonator fabrication in fluoride
crystals, thorium implantation,
nuclear excitation with integrated
lasers, and on-chip detection of
vacuum-ultraviolet
photons. As an initial proof of concept, we implant a crystalline fluoride whispering-gallery-mode resonator with $^{229}$Th and assess the impact of implantation-induced damage on resonator performance. Our platform leverages recent advances in materials integration and nanophotonics to chart a realistic route toward compact and scalable
nuclear frequency standards.
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All authors Sandro Kraemer, Karen Mamian, Toby Bi, Shun Fujii, Jan de Haan, Harshith Babu, Arno Claessens, Rafael Ferrer Garcia, Fedor Ivandikov, Piet Van Duppen, Andreas Dragoun, Christoph E. Düllmann, Christoph Marquardt, Ulrich Wahl, Bart Kuyken, Thorsten Schumm, Pascal Del'Haye, Lino M. C. Pereira, Georgy A. Kazakov, Kasper Van Gasse, Charles Roques-Carmes
Soft Condensed Matter
Flow-history-dependent orientational relaxation in dilute polydisperse colloidal rod suspensions
Yuto Yokoyama, Vincenzo Calabrese, Fabian Hillebrand et al. (+3 more)
Orientation and relaxation dynamics of rod-like colloids under flow govern the optical and mechanical properties of many emerging soft materials. In polydisperse suspensions, particles of different lengths exhibit distinct rotational
diffusion timescales, yet how this polydispersity influences relaxation following flow cessation remains unclear. In particular, it is not well understood how the pre-shear rate determines the subsequent orientation relaxation dynamics. To address this question, we performed simple shear on dilute cellulose nanocrystal (CNC) suspensions in a narrow-gap Taylor-Couette
cell and measured birefringence relaxation after flow cessation using high-speed polarization imaging. To interpret the experiments, we formulated a polydisperse Fokker-Planck model parameterized by the measured length distribution. As a result, the average orientation relaxation time systematically decreases with increasing pre-shear rate. Moreover, when organized by the Péclet number based on the rotational
diffusion coefficient of the weighted average rod length, the data agree well with the theory over a wide range of shear rates. This trend arises because the rod sub-population contributing most strongly to the orientation shifts from longer rods to shorter rods as the pre-shear rate increases, showing that the flow history governs the orientation relaxation dynamics. In polydisperse systems, the orientation relaxation time is no longer a material-specific constant but is determined by both the flow conditions and the polydispersity. This study provides a quantitative framework for understanding orientation dynamics in polydisperse rod suspensions and for interpreting rheo-optical measurements.
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All authors Yuto Yokoyama, Vincenzo Calabrese, Fabian Hillebrand, Henry J. London, Simon J. Haward, Amy Q. Shen
Materials Science
Strain effects in [001] textured Co80Ir20 thin films with negative magnetocrystalline anisotropy
L. Aviles Felix, M. Vasquez Mansilla, J. E. Gomez et al. (+6 more)
Co80Ir20
ferromagnetic thin films have recently been the focus of intensive research because the negative magnetocrystalline anisotropy adds to the shape anisotropy and favors a strong
alignment of the magnetization in the film plane for [001] textured or epitaxial thin films. However, the role of magnetoelastic effects has not been properly considered in most published research. In this work we have performed a detailed analysis of 24 nm Co80Ir20 thin films deposited on Si/SiO2 with different underlayers (Ta, Pt) and overlayers in order to induce [001]-textured growth and different degrees of strain. Using x-ray diffraction measurements we have found that the c-axis
lattice parameter depends on the underlayer material (larger negative strain for Ta), but the degree of texture and the average grain size remain essentially constant, except for one of the multilayers. Differences in the
magnetic behavior according to the underlayer were also found in room temperature magnetization vs field loops and temperature dependent dc magnetization measurements. Anisotropy was quantified using
ferromagnetic resonance which showed that the effective anisotropy field is also dependent on the underlayer. Ta underlayers show an anisotropy close to that expected for shape, while Pt underlayer induces an additional in-plane anisotropy field of the order of 7-9 kOe. A simple model of stress induced anisotropy gives anisotropy field values similar to those observed experimentally. The correlation between observed strain and anisotropy together with the similarity in microstructural properties strongly suggests that stress effects cannot be disregarded when analyzing the
magnetic data for the estimation of the magnetocrystalline contribution.
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All authors L. Aviles Felix, M. Vasquez Mansilla, J. E. Gomez, M. Balod, J. Padilla, J. Santiso, Subhakanta Das, S.N. Piramanayagam, A. Butera
Materials Science
Polaron transport and Verwey transition in magnetite
Nikita Fominykh and Vladimir Stegailov
The enigmatic puzzle of the Verwey transition in magnetite Fe$_3$O$_4$ has been unresolved for almost a century. We present an ab initio-based model of the polaron transport combining kinetic Monte Carlo and molecular dynamics calculations to directly describe the coupling of polarons with
lattice vibrations. Contrary to the Ihle-Lorentz small-polaron model, we find no significant change in the band structure across the Verwey transition, however, trimeron hopping is observed. The proposed model provides dc-conductivity in agreement with experimental data across the Verwey transition.
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Materials Science
Load-dependent Hardness Prediction for Materials using Machine Learning
Madhubanti Mukherjee, Rampi Ramprasad and Harikrishna Sahu
Superhard materials are critical for wear-resistant and high-stress applications. Conventional approaches correlating hardness with elastic
moduli derived from DFT calculations enable rapid screening but overlook the strong load dependence of hardness. In this work, machine learning (ML) models were developed using a large, curated
dataset of load-dependent experimental Vickers hardness (Hv) measurements. Moderate correlation was observed between experimental and DFT-based Hv values, whereas a single-task ML model trained solely on experimental data outperformed multi-task models that combined experimental and computed data. The superior performance of the single-task model highlights that explicit inclusion of indentation load, along with compositional, electronic, and structural descriptors, is essential and sufficient for accurate hardness prediction, beyond what can be achieved using DFT-accessible bulk and shear
moduli alone (or in tandem with experimental data). These results emphasize the importance of high-quality experimental data and explicit inclusion of measurement conditions, particularly load, in the development of reliable hardness prediction models.
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Statistical Mechanics · Cross-listed from math.PR
The Ising Model on a Two-Community Stochastic Block Model
Alessandra Bianchi, Vanessa Jacquier and Matteo Sfragara
We study the Ising model on a two-community
stochastic block model, where $n$
spins are split into two equal groups with inter-community interaction parameter $\alpha_n\in[0,1]$. We provide a complete characterization of the phase diagram and show that, almost surely with respect to the graph realization, the model undergoes a uniqueness/non-uniqueness phase transition of the Gibbs measure. In particular, in the supercritical regime, the law of the magnetization vector of the two communities converges to a mixture of Dirac measures that, depending on whether $\alpha_n\gg 1/n$ or $\alpha_n\lesssim1/n$, is supported on two or four points, with possibly different weights. In the uniqueness region, we further analyze the fluctuations of the magnetization vector in the subcritical regime and we prove a quenched central limit
theorem.
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Mesoscale and Nanoscale Physics
Topological Word for Non-Abelian Topological Insulators
Zhenming Zhang, Tianyu Li and Wei Yi
We propose a unified framework, dubbed topological word, for the complete non-Abelian bulk-boundary correspondence in multigap non-Abelian topological
insulators. Composed by an ordered sequence of letters, each a non-Abelian charge depicting the gap-resolved
topology, the topological word captures both the global non-Abelian
topology corresponding to the homotopy classification, and the band-adjacency information. The latter, though crucial for the edge-state pattern across multiple gaps, is often overlooked in previous studies. We confirm our framework using both static models and periodically driven Floquet systems, and discuss its connection and distinction with existing descriptions, such as the phase-band singularities and braiding representations. Intriguingly, topological word continues to provide insight regarding
topology and edge states, even as the global non-Abelian
topology becomes ill-defined under broken parity-time
symmetry.
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Statistical Mechanics · Cross-listed from hep-th
Stochastic Krylov Dynamics: Revisiting Operator Growth in Open Quantum Systems
Arpan Bhattacharyya, S. Shajidul Haque, Jeff Murugan et al. (+2 more)
In closed
quantum systems, Krylov complexity admits a
geometric description; operator growth is equivalent to
Hamiltonian flow in an emergent phase space whose structure is fixed by the Lanczos coefficients. We show that this picture survives, albeit in a fundamentally altered form, once the system is coupled to an environment.Using a Schwinger-Keldysh formulation of the full counting statistics of the Krylov position, we derive an effective action for operator growth under Lindblad dynamics. Even for the minimal case of dephasing, the phase-space dynamics ceases to be
Hamiltonian; environmental coupling generates
diffusion in the variable conjugate to Krylov depth, converting deterministic trajectories in to
stochastic ones. The
hyperbolic mechanism underlying exponential complexity growth is therefore broadened and, beyond a parametrically controlled scale, destroyed.This identifies dissipation as a relevant perturbation of the chaotic Krylov fixed point and reveals operator growth in open systems as a problem of
stochastic dynamics in an emergent phase space.
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All authors Arpan Bhattacharyya, S. Shajidul Haque, Jeff Murugan, Mpho Tladi, Hendrik J.R. Van Zyl
Superconductivity
Superconductivity in bilayer La$_3$Ni$_2$O$_7$: A review focusing on the strong-coupling Hund's rule assisted pairing mechanism
Zhiming Pan, Chen Lu, Fan Yang et al. (+1 more)
Discovery of high-$T_c$ superconductivity (SC) in the
bilayer nickelate series La$_3$Ni$_2$O$_7$ have attracted substantial interest, providing a new platform for exploring unconventional SC. Certain experimental evidence has pointed to a correlated electronic nature, which is the driving force responsible for its high critical temperature ($T_c$). This work reviews the SC in La$_3$Ni$_2$O$_7$, with a particular focus on theoretical understanding of its pairing mechanism driven by this strong-coupling, Hund-assisted scenario. The electronic landscape is governed by two $E_g$-orbitals within the
bilayer structure of NiO$_2$ planes. The $3d_{z^2}$ orbital is nearly half-filled and exhibits a stronger localized character, while the $3d_{x^2-y^2}$ is approximately quarter-filled and remains highly itinerant. The localized $3d_{z^2}$ orbitals experience robust interlayer hybridization, mediated by the $2p_z$ orbitals of the inner apical oxygen atoms. This hybridization generates a strong interlayer
antiferromagnetic (AFM) exchange. In the strong coupling regime, Hund's rule coupling aligns the
spins of the two $E_g$ orbitals on the same nickel site. The strong interlayer AFM exchange is effectively transferred to the itinerant $3d_{x^2-y^2}$ orbital, generating an effective coupling $J_{\perp}$ within this orbital. This mechanism is captured by a minimal strong-coupling
bilayer $t$-$J$-$J_{\perp}$ model for the $3d_{x^2-y^2}$ band. Driven by $J_{\perp}$, $3d_{x^2-y^2}$ electrons can form interlayer Cooper pairs, leading to an extended $s$-wave pairing SC with high $T_c$. Meanwhile, the strongly localized $3d_{z^2}$ electrons tend to form interlayer rung singlets. Due to a lack of phase coherence, these singlets do not directly participate in the SC condensate, but instead give rise to a pseudogap phase.
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All authors Zhiming Pan, Chen Lu, Fan Yang, Congjun Wu