Other Condensed Matter
Engineering edge states in two-leg SSH ladder and their topoelectric circuit realization
Anish Kuanr, Rajashri Parida, Prabhu Prasad Tripathy et al. (+2 more)
We study the topological phase transition in a two-leg Su-Schrieffer-Heeger (SSH) ladder by redefining the unit-
cell structure. For both identical hopping dimerization pattern (uniform) and alternate hopping dimerization pattern (staggered) along the legs of the ladder, we demonstrate that different unit-
cell choices generate different topological phases and phase transitions. In the uniformly dimerized ladder, variation of the inter-leg coupling induces a transition from topological phase to another topological phase through a gapless region. In contrast, the staggered dimerization configuration exhibits a richer phase structure, supporting both topological-topological and trivial-topological transitions occurring through a single gap-closing point, depending on the unit-
cell definition. The phases are characterized through bulk-boundary correspondence, edge-state analysis, and bulk topological invariants. Interestingly, we obtain that while all the topological phases host two zero energy edge states each, the topological phase for the staggerred dimerization case at small inter-leg coupling hosts four edge states. We then perform topoelectric
circuit simulation and experiments to observe the signatures of the topological phases. By using
circuit impedance and voltage responses we establish the emergence of distinct edge modes in the
circuit. Our analysis provides a route to engineer topological edge modes in a two-leg SSH ladder set-up.
Read the full abstract ▾
All authors Anish Kuanr, Rajashri Parida, Prabhu Prasad Tripathy, Saralasrita Mohanty, Tapan Mishra
Materials Science
Enhancing Phase Clustering in Nanomechanical Property Maps of Multiphase Materials Using Kernel-Averaged Mechanical Mismatch
David Mercier and Yasmine El Gharoussi
This work presents a novel approach to improve phase identification in nanomechanical property maps of multiphase materials, such as those obtained by nanoindentation or atomic force microscopy (AFM). A major challenge in validating clustering strategies for these data is the lack of ground-truth phase labels in experimental measurements, along with the tendency of overly simplistic synthetic
datasets to artificially inflate
algorithm performance. To address this gap, we construct controlled yet non-trivial synthetic
benchmarks with tunable mechanical contrast, graded interfaces, curved boundaries, and diffuse morphologies, enabling rigorous and realistic evaluation of clustering robustness. Conventional clustering methods based only on elastic modulus (E) and hardness (H) often struggle to separate phases when mechanical contrast is low or when diffuse interphase regions are present. We introduce the Kernel-Averaged Mechanical Mismatch (KAMM), a neighborhood-informed feature that quantifies local mechanical heterogeneity by comparing each point to its neighbors in (E, H) space. When incorporated into a three-dimensional clustering space (E, H, KAMM), this framework improves phase separability, enhances interphase detection, and increases robustness to noise. By enabling more reliable
segmentation of mechanical domains under realistic contrast conditions, the proposed method facilitates the generation of representative volume elements (RVEs) and supports more accurate extraction of phase-specific properties in heterogeneous microstructures.
Read the full abstract ▾
Materials Science
High-quality, high-information datasets for universal atomistic machine learning
Cesare Malosso, Filippo Bigi, Paolo Pegolo et al. (+7 more)
The quality, consistency, and information content of training data is often what determines the practical value of machine-learning models for atomistic simulations. Yet, many widely used electronic-structure databases are assembled having materials screening as primary goal rather than robust force-field learning, are limited in their scope to a specific class of chemical compounds, and/or employ inconsistent DFT functionals and settings. Here we introduce MAD-1.6, a highly curated
dataset designed explicitly for training broadly applicable atomistic models across the periodic table at high levels of theory. MAD-1.6 extends the MAD
dataset with targeted enrichment strategies that improve the coverage of chemical space to 102 elements while keeping the total number of configurations compact. All structures are computed with a single, standardized all-electron DFT workflow using the r$^2$SCAN meta-GGA functional and consistent convergence settings, ensuring uniformity across chemically heterogeneous systems. The
dataset encompasses molecules, clusters, bulk
crystals, surfaces, and low-dimensional structures, and its quality and consistency are further enhanced by outlier removal using uncertainty quantification. We demonstrate the high accuracy that can be achieved with the proposed
dataset by training PET-MAD-1.6, a generally applicable r$^2$SCAN interatomic potential that covers 102 elements in the periodic table and achieves exceptional levels of
benchmark accuracy and stability in challenging simulation protocols.
Read the full abstract ▾
All authors Cesare Malosso, Filippo Bigi, Paolo Pegolo, Joseph W. Abbott, Philip Loche, Mariana Rossi, Tiago J. Goncalves, Sandip De, Michele Ceriotti, Arslan Mazitov
Mesoscale and Nanoscale Physics
Scalable tight-binding model for strained graphene
Ming-Hao Liu, Christophe De Beule, Alina Mreńca-Kolasińska et al. (+4 more)
We generalize the scalable tight-binding model for
graphene, which allows for efficient
quantum transport simulations in the Dirac regime, to account for elastic strain. We show that the original scalable model with scaling factor $s$ is readily applicable to strained
graphene, provided that the displacement fields corresponding to the deformed
graphene lattice are properly scaled. In particular, we show that the long-wavelength theory remains invariant when the strain tensor is scaled by $s$. This is achieved in practice by scaling the in-plane displacement fields by $s$ while the out-of-plane displacements have to be scaled by $\sqrt{s}$. We confirm these scaling laws by extensive numerical simulations, starting with the pseudomagnetic field and the local density of states for different scaled
lattices. The latter allows us to study pseudo-Landau levels as well as hybrid Landau levels in the presence of an external
magnetic field. Finally, we consider
quantum transport simulations motivated by a recent experiment, where a uniaxial strain barrier is engineered in monolayer
graphene by vertically misaligned gates. Our work generalizes the scalable tight-binding model to allow for efficient modeling of
quantum transport in large-scale strained
graphene devices.
Read the full abstract ▾
All authors Ming-Hao Liu, Christophe De Beule, Alina Mreńca-Kolasińska, Hsin-You Wu, Aitor Garcia-Ruiz, Denis Kochan, Klaus Richter
Mesoscale and Nanoscale Physics
Anisotropic two-dimensional magnetoexciton with exact center-of-mass separation
Dang-Khoa D. Le, Hoang-Viet Le, Dai-Nam Le et al. (+4 more)
Excitons in anisotropic two-dimensional (2D) materials, defined by direction-dependent effective masses, are of pronounced interest for their roles in excitonic and magneto-optical phenomena. A perpendicular
magnetic field complicates the separation of center-of-mass (c.m.) and relative motions, especially when electron and hole masses are comparable. Conventional theories often employ an approximate c.m. separation using factorized wave functions, modifying
magnetic Hamiltonian terms and possibly introducing inaccuracies in magnetoexciton energy predictions. This work develops an exact analytical framework for c.m. and relative motion separation in anisotropic 2D magnetoexcitons, without resorting to the stationary-c.m. approximation. Starting from the full electron-hole
Hamiltonian in a homogeneous
magnetic field, the formalism uses the conserved pseudomomentum to derive a relative-motion
Hamiltonian, revealing new anisotropy-dependent couplings and
magnetic coefficients absent in approximate models. The resulting Schrödinger equation is treated via the Feranchuk-Komarov operator method and Levi-Civita transformation, allowing non-perturbative, systematically convergent solutions. Application to monolayer black phosphorus and titanium trisulfide, both freestanding and encapsulated in hexagonal boron nitride, yields magnetoexciton energies, diamagnetic coefficients, and probability densities for the ten lowest states across considerable
magnetic-field ranges. The results demonstrate the significant influence of anisotropy-dependent coupling on
magnetic response in systems with strong mass anisotropy. This formalism is generalizable to other anisotropic 2D
semiconductors, establishing a foundation for advanced magneto-optical studies.
Read the full abstract ▾
All authors Dang-Khoa D. Le, Hoang-Viet Le, Dai-Nam Le, Duy-Anh P. Nguyen, Thanh-Son Nguyen, Ngoc-Tram D. Hoang, Van-Hoang Le
Soft Condensed Matter
Ionic Liquid-Driven Modulation of DNA Brush Morphology on Nanoparticle Surfaces
Anuj Chhabra, Sandip Mandal, Yugang Zhang et al. (+3 more)
The morphology of DNA is strongly influenced by its surrounding environment, including factors such as pH, salt type and valency, and the presence of
polymers. Inorganic salts are known to reduce the DNA chain length through mechanisms like electrostatic screening and ion bridging. In contrast, ionic
liquids, a new class of organic salts, have previously been found to increase the DNA chain length, indicating a distinct mode of interaction between the ionic
liquid and DNA chains. This study utilizes self-assembled DNA-AuNPs as a model system to examine changes in the DNA chain morphology and the nanoscale interaction mechanisms in ionic
liquid environment. The DNA chain lengths are measured in solution using X-ray scattering measurements at varying concentrations of two imidazolium ([BMIM] acetate and [EMIM] acetate) based ionic
liquids. Additionally, Molecular Dynamics (MD) simulations are performed mimicking the experimental system. Our results suggest an interplay of electrostatic and groove-binding interactions governing the DNA chain morphology, which depends on IL concentration and the composition of the DNA chains. It has been found that for DNA chains with majority ssDNA, electrostatic interaction dominate, however with increasing composition of double strands, the DNA chains exhibits compaction due to non-electrostatic hydrophobic groove-binding mechanism.
Read the full abstract ▾
All authors Anuj Chhabra, Sandip Mandal, Yugang Zhang, Oleg Gang, Prabal K. Maiti, Sunita Srivastava
Mesoscale and Nanoscale Physics
On-surface synthesis and aromaticity of large cyclocarbons
Lisanne Sellies, Marco Vitek, Yueze Gao et al. (+12 more)
Molecular rings of N carbon atoms, that is, cyclo[N]carbons, or C$_N$, can be formed by tip-induced chemistry [1-7]. Because of their monocyclic geometry, cyclocarbons are fundamentally important for testing theoretical models of aromaticity [8-11]. Here, we synthesized large cyclo[N]carbons, with N up to 88, by tip-induced chemistry on a NaCl surface and studied their aromaticity by measuring their transport gaps by scanning tunnelling spectroscopy. We first generated C$_{20}$ and C$_{22}$, and then fused multiple cyclocarbons [5-7] by means of atom manipulation, obtaining C$_{42}$, C$_{44}$, C$_{46}$, C$_{66}$ and C$_{88}$. In agreement with predictions obtained using a finely tuned density functional [12-15] and large active space approximate configuration interaction calculations executed on
quantum hardware [16, 17], we observe a substantially smaller transport gap for C$_{20}$ (N = 4n) compared to C$_{22}$ (4n+2), and for C$_{44}$ (4n) relative to C$_{42}$ (4n+2). In larger cyclocarbons, the oscillation of the transport gap between anti-aromatic N = 4n and aromatic N = 4n+2 cyclocarbons becomes smaller, and is expected to eventually vanish with increasing N, indicating non-aromaticity. Our experimental results show that aromaticity persists at N = 42, and theory predicts ring currents comparable in magnitude to that of benzene in cyclocarbons of this size. In the future, such large cyclocarbons could be used to study conductance,
quantum interference, and the effects of aromaticity in single atomic carbon wires and
circuits.
Read the full abstract ▾
All authors Lisanne Sellies, Marco Vitek, Yueze Gao, Fabian Paschke, Florian Albrecht, Jakob Eckrich, Beren Dempsey, Stefano Barison, Leonard-Alexander Lieske, Samuele Piccinelli, Alberto Baiardi, Ivano Tavernelli, Harry L. Anderson, Igor Rončević, Leo Gross
Strongly Correlated Electrons
Graph neural network force fields for adiabatic dynamics of lattice Hamiltonians
Yunhao Fan and Gia-Wei Chern
Scalable and
symmetry-consistent force-field models are essential for extending
quantum-accurate simulations to large spatiotemporal scales. While descriptor-based neural networks can incorporate
lattice symmetries through carefully engineered features, we show that graph neural networks (GNNs) provide a conceptually simpler and more unified alternative in which discrete
lattice translation and point-group
symmetries are enforced directly through local message passing and weight sharing. We develop a GNN-based force-field framework for the adiabatic dynamics of
lattice Hamiltonians and demonstrate it for the semiclassical Holstein model. Trained on exact-diagonalization data, the GNN achieves high force accuracy, strict linear scaling with system size, and direct transferability to large
lattices. Enabled by this scalability, we perform large-scale Langevin simulations of charge-density-wave ordering following thermal quenches, revealing dynamical scaling and anomalously slow sub–Allen–Cahn coarsening. These results establish GNNs as an elegant and efficient architecture for
symmetry-aware, large-scale dynamical simulations of correlated
lattice systems.
Read the full abstract ▾
Strongly Correlated Electrons
Tensor-network methodology for real-space super-moiré excitons
Anouar Moustaj, Yitao Sun, Tiago V. C. Antão et al. (+2 more)
Computing excitonic spectra in quasicrystal and super-moiré systems constitutes a formidable challenge due to the exceptional size of the excitonic
Hilbert space. Here, we demonstrate a tensor-network method for the real-space Bethe-Salpeter
Hamiltonian, allowing us to access the spectra of an excitonic $10^{18}$-dimensional
Hamiltonian, and enabling the direct computation of bound-
exciton spectral functions for systems exceeding one billion
lattice sites, several orders of magnitude beyond the capabilities of conventional approaches. Our method combines a tensor-network encoding of the real-space Bethe-Salpeter
Hamiltonian with a Chebyshev tensor network
algorithm. This strategy bypasses explicit storage of the
Hamiltonian while preserving full real-space resolution across widely different length scales. We demonstrate our methodology for one- and two-dimensional super-moiré systems, achieving the simultaneous resolution of atomistic and mesoscopic structures in the excitonic spectra in billion-size systems, showing
exciton miniband formation and moiré-induced spatial confinement. Our results establish a real-space methodology enabling the simulation of excitonic physics in large-scale quasicrystal and super-moiré
quantum matter.
Read the full abstract ▾
All authors Anouar Moustaj, Yitao Sun, Tiago V. C. Antão, Lumen Eek, Jose L. Lado
Statistical Mechanics
On the upper critical dimension of the KPZ universality class: KPZ and related equations on a fully connected graph
J. M. Marcos, J. J. Meléndez, R. Cuerno et al. (+1 more)
We investigate the infinite-dimensional limit of nonequilibrium surface growth by numerically integrating
stochastic growth equations on a fully connected graph. In particular, we study the Edwards-Wilkinson (EW), Kardar-Parisi-Zhang (KPZ), and tensionless KPZ (TKPZ) equations. Using a network discretization adapted to the all-to-all interaction
topology, we analyze the global roughness, height-fluctuation statistics, time power spectra, and two-time correlations. For the EW equation, we obtain an exact expression for the roughness that matches the numerical simulations and shows that the interface becomes flat as the number of nodes in the graph, $N$, tends to infinity. We also compute analytically the time power spectrum, show that height fluctuations are Gaussian, and derive an explicit expression for the two-time height autocorrelation function, indicating that the aging behavior is trivial. For the KPZ equation, finite-size and strong-coupling effects can cause deviations from EW behavior at moderate system sizes $N$, often accompanied by numerical instabilities; however, these differences disappear as $N$ increases. In the large-$N$ limit, KPZ dynamics converges to EW behavior, as the four observables analyzed exhibit identical scaling properties. Overall, our results indicate that on a fully connected graph the KPZ nonlinearity is irrelevant as $N\to\infty$, leading to EW-like dynamics with asymptotically flat interfaces. These findings are interpreted in the context of the upper critical dimension of the KPZ universality class.
Read the full abstract ▾
All authors J. M. Marcos, J. J. Meléndez, R. Cuerno, J. J. Ruiz-Lorenzo
Mesoscale and Nanoscale Physics
Layer-polarized Transport via Gate-defined 1D and 0D PN Junctions in Double Bilayer Graphene
Wei Ren, Xi Zhang, Shiyu Guo et al. (+6 more)
We fabricate twisted double
bilayer graphene devices with zero twist angle and a set of local top and bottom gates aligned perpendicularly to each other. A 1D PN junction can be electrostatically defined when the gate voltages applied to the top gates are the same but different on the bottom gates. Resistance peaks are observed at finite doping instead of at the charge neutrality points, exhibiting an unconventional broken-cross shape that arises from layer polarization of the P and N region, which can be further enhanced with finite
magnetic fields. A 0D point junction (PJ) can be electrostatically defined by applying different gate voltages to the top and bottom gates, such that the P and N sides of the device are connected at a single point in the center of the device. As finite
magnetic field B increases, the
quantum Hall (QH) states are selectively brought into contact or away from each other depending on their layer polarization, leading to unconventional
quantum oscillations which characterize the layer-polarized band-crossing. Our work provides new insights into understanding band-structure
evolution and layer polarization in twisted
bilayers and paves the way for new device functionality based on manipulating layer-polarized electronic states.
Read the full abstract ▾
All authors Wei Ren, Xi Zhang, Shiyu Guo, Jeongsoo Park, Jack Tavakley, Daochen Long, Kenji Watanabe, Takashi Taniguchi, Ke Wang
Statistical Mechanics · Cross-listed from quant-ph
Minimal-backaction work statistics of coherent engines
Milton Aguilar, Franklin L. S. Rodrigues and Eric Lutz
Determining the work statistics of
quantum engines is challenging due to measurement backaction. We here show that a dynamic
Bayesian network-based measurement scheme, which preserves
quantum coherence within an engine cycle, is minimally invasive, in the sense that the averaged measured state over one cycle exactly coincides with the unmeasured state. It therefore provides a general framework to investigate energy exchange statistics in
quantum machines. This stands in contrast to the standard two-point measurement protocol, whose backaction can be so strong that it generally fails to reproduce the average work output of a coherent motor. It may even alter its mode of operation, causing it to cease functioning as an engine under observation. We further demonstrate that recently proposed universal fluctuation bounds do not necessarily apply to coherent machines.
Read the full abstract ▾
Strongly Correlated Electrons
Quantum-geometry-driven exact ferromagnetic ground state in a nearly flat band
Taisei Kitamura, Hiroki Nakai, Hosho Katsura et al. (+1 more)
We construct a Hubbard model with a nearly flat band whose
quantum geometry can be tuned independently of the energy dispersion and the Coulomb interaction. We show that, when the nearly flat band is half-filled, the exact ground state of the model exhibits ferromagnetism and that this ferromagnetism is stabilized by the
quantum metric through the
spin stiffness. Furthermore, we demonstrate that tuning the
quantum geometry alone drives a
magnetic phase transition. Our nonperturbative results without resorting to mean-field approximations reveal the
quantum-
geometric origin of ferromagnetism and the underlying many-body physics in dispersive-band systems.
Read the full abstract ▾
All authors Taisei Kitamura, Hiroki Nakai, Hosho Katsura, Ryotaro Arita
Soft Condensed Matter
A Vibrated Compacting Granular System: A DEM Light Scattering Comparison
Linnea Heitmeier and Jan Philipp Gabriel
We perform Discrete Element Method (DEM) simulations of granular particles (polystyrene spheres) vibrated inside a cubic container. The study investigates the
evolution of the packing fraction with and without rotational friction at different shaking amplitudes. The mean-squared displacement (MSD) is used to analyze the particles' diffusive, subdiffusive, and superdiffusive behavior. By monitoring both the dynamics and density
evolution, one can observe the system's glassification. The comparison with experiments shows that the MSDs from the simulations are significantly higher than the MSDs measured by Diffusing Wave Spectroscopy (DWS) \cite{kunzner2025dynamics}. Following our finding that the rotational MSD is of the same order of magnitude as the MSD measured in DWS experiments, we propose that the experimental signal is not dominated by translational motion but rather by rotational particle dynamics. This provides access to a relevant particle property that has previously been difficult to measure directly. Finally, we conclude that the system reaches a dynamically constrained state well before random close packing, with particle displacements already below the Lindemann length.
Read the full abstract ▾
Materials Science
Pathway to lowest-energy structures and stress relaxation for the surface triple junction of copper
Ipen Demirel, Yuan Fang, Yan Liu et al. (+5 more)
The behavior of surface triple junctions (STJ) at emergent grain boundaries on free surfaces is critical to the microstructure
evolution, and therefore to the stability of next generation interconnects. Yet, despite this significant importance, its lowest-energy structure and local stress have remained persistently unknown. Here, we fill this critical gap through high-resolution experimental mapping of the local surface deformation at STJs of a symmetrical tilt grain boundaries with [111] rotation axis and misorientation angles 13.17{\deg}, the analysis of the local core-shifted structure and stress relaxation, and ergodic searching metastable structures accordingly with the molecular-statics (MS) calculation. The computation clearly shows the zipped Y-shaped notch as the lowest-energy structures for this group of STJs, the line profile of which is consistent with the experimental observation. This energetic preference was well explained by the stress delocalization mechanism and was tested for a wide range of boundaries with even deeper core-shift depth using machine learning methods based on the data obtained from MS calculation. By revealing the elusive thermodynamics of STJs, our findings advance the research field by redefining the energetic framework for capillary driven structure
evolution and providing foundation for understanding kinetically diffusive deformation and for engineering thin-film interconnects and related materials.
Read the full abstract ▾
All authors Ipen Demirel, Yuan Fang, Yan Liu, Haitian Shan, Xiaopu Zhang, Yuchuan Shao, Jianda Shao, John J. Boland
Quantum Gases
Classical field simulation of vortex lattice melting in a two-dimensional fast rotating Bose gas
Sálvio Jacob Bereta, Lucas Madeira, Mônica A. Caracanhas et al. (+2 more)
We present a classical field simulation study of the thermal melting of a two-dimensional
vortex lattice in a rotating Bose gas, focusing on the role of finite-size effects on the melting temperature. This work constitutes a numerical continuation of the recent experimental investigation reported in [Physical Review Letters 133, 143401 (2024)], which addressed the thermal melting of a
vortex lattice in a quasi-two-dimensional Bose gas. Using the
stochastic projected Gross-Pitaevskii equation in a harmonic plus quartic trap, we simulate the finite-temperature
equilibrium state and extract
vortex configurations from density snapshots. Clear signatures of the two-step Kosterlitz–Thouless–Halperin–Nelson–Young melting scenario are identified. Our simulations enable a detailed characterization of the crystalline, hexatic, and
liquid phases through correlation functions quantifying the translational and orientational order and through defect statistics. Finite-size effects are shown to play a crucial role at lower rotation frequencies, affecting the proliferation of
lattice defects.
Read the full abstract ▾
All authors Sálvio Jacob Bereta, Lucas Madeira, Mônica A. Caracanhas, Hélène Perrin, Romain Dubessy
Mesoscale and Nanoscale Physics
Configurational control of photon emission from a molecular dimer
Maximilian Kögler, Nicolas Néel and Jörg Kröger
Tin-phthalocyanine molecules adsorbed on a NaCl ultrathin film on Au(111) exhibit electrofluorescence excited by a current across a scanning tunneling microscope junction. Exploring the dependence of the molecular monomer
photon yield on the injected current evidences the one-electron excitation process underlying the neutral-
exciton luminescence.
Photon spectra of the monomer exhibit vibrational progression and hot luminescence, while the dimer electrofluorescence spectroscopic fine structure results from the coupling of the adjacent optical transition dipoles. The
photon yield of the dimer is significantly altered upon changing the configurational state of one of the two molecules. In one of the bistable configurations light emission is amplified compared to the monomer, and it is reduced in the other.
Read the full abstract ▾
Materials Science · Cross-listed from physics.chem-ph
A Relationship between the Molecular Parity-Violation Energy and the Electronic Chirality Measure
Juan J. Aucar, Alessandro Stroppa and Gustavo A. Aucar
When the weak-forces producing parity-violating effects are taken into account, there is a tiny energy difference between the total electronic energies of two enantiomers ($\Delta E_{PV}$), which might be the key to understand the
evolution of the biological homochirality. We focus on the electronic chirality measure ($ECM$), a powerful descriptor based on the electronic charge density, for quantifying the chirality degree of a molecule, for a representative set of
chiral molecules, together with their E$_{PV}$ energies. Our results show a novel, strong and positive correlation between $\Delta E_{PV}$ and $ECM$, supporting a subtle interplay between the weak-forces acting within the
nuclei of a given molecule and its chirality. These findings suggest that experimental investigations for molecular parity violation detection should consider molecules with as large $ECM$ values as possible, and may support that a
chiral signature is imprinted on life by fundamental physics via the parity-violating weak interactions.
Read the full abstract ▾
Strongly Correlated Electrons
Local integrals of motion encoded in a few eigenstates
J. Pawłowski, P. Łydżba and M. Mierzejewski
Many properties of a
quantum system can be obtained from just a single eigenstate of its
Hamiltonian. For example, a single eigenstate can be used to determine whether a system is integrable or chaotic and, in the latter case, to establish its thermal properties. Focusing on the XXZ model, we show that the local integrals of motion, which lie at the heart of integrability, can also be estimated from a small number of eigenstates. Moreover, as the system size increases, fewer eigenstates are required, so that in the thermodynamic limit, the integrals of motion can be obtained from a vanishingly small fraction of all eigenstates. Interestingly, this property does not extend to integrals of motion arising solely from
Hilbert space fragmentation, as found in the folded XXZ model, where the majority of eigenstates has to be used. This represents one of the few fundamental differences known between integrability and
Hilbert space fragmentation.
Read the full abstract ▾
Statistical Mechanics
Information-fluctuation inequalities for collective response
Kristian Stølevik Olsen
Hidden
stochastic effects acting uniformly on a many-particle system can generate strong correlations and macroscopic relative fluctuations that persist at large system sizes, even when the particles themselves remain causally independent. Here we derive a universal upper bound on relative fluctuations for a large class of observables, formulated in terms of a generalized mutual information between observable states and the hidden variable. This information-fluctuation inequality provides general insights into the principles governing collective response induced by global disorder. We demonstrate the result with applications to non-interacting Brownian gases exposed to various types of dynamical disorder.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Identifying field-tunable surface resonance states on black phosphorus
Dongming Zhao, Byeongin Lee, Junho Bang et al. (+3 more)
Surface resonance states are electronic states localized near the surface while remaining hybridized with bulk bands. These states can strongly modify the electric-field response of
semiconductors. Here, we demonstrate using scanning tunneling spectroscopy that on black phosphorus, surface resonance states near the valence-band edge dominate the screening of a strong external electric field. We observe in the tunneling conductance spectrum a pronounced dip with an energy continuously tunable by the local electric field in the tunneling junction. Meanwhile, we also notice that the bulk band edges remain effectively pinned, indicating efficient surface screening and suppression of bulk band bending. We interpret the conductance dip as the consequence of a field-dependent tunneling barrier: as the external electric field drives the surface resonance band into the band gap, the coupling between the surface resonance states and the bulk states is suppressed, leading to a reduced tunneling probability. Our simplified model based on this mechanism reproduces our main experimental findings. Our results highlight surface-localized states as a critical component in the electrostatic response of
semiconductors, which must be taken into consideration in the design and operation of nanoscale
semiconductor devices.
Read the full abstract ▾
All authors Dongming Zhao, Byeongin Lee, Junho Bang, Claudia Felser, Jian-Feng Ge, Doohee Cho
Materials Science
Defect dependent dynamic nanoindentation hardness of copper up to 25 000 s-1
Hendrik Holz, Lalith Kumar Bhaskar, Tobias Brink et al. (+4 more)
Metals exhibit an upturn in strength at strain rates of approximately 1000 s-1 - 3000 s-1, governed by rapid dislocation multiplication, interactions and storage. This phenomenon is strongly influenced by the initial dislocation density before testing. However, the role of immobile dislocations arranged in low-angle grain boundaries (LAGBs) on deformation under such extreme conditions remains unexplored, despite their ubiquity in engineering materials. Here, we employ high strain rate nanoindentation targeted at an LAGB with tilt and twist components in copper
crystals with different dislocation densities. We demonstrate that Taylor hardening remains valid over a wide range of strain rates. It was found that the influence of LAGBs on mechanical properties is within the scatter of the measurements. However, slip traces of indents close to the LAGB suggest that the LAGB acts as a barrier to dislocations. Molecular dynamics simulations further confirm these findings. The measured activation volume and low strain rate re-indentation onto indents performed at different higher strain rates give insights into the deformation mechanism. This work provides new insight into the interplay between microstructure and high strain rate deformation.
Read the full abstract ▾
All authors Hendrik Holz, Lalith Kumar Bhaskar, Tobias Brink, Dipali Sonowane, Gerhard Dehm, James P. Best, Rajaprakash Ramachandramoorthy
Materials Science · Cross-listed from quant-ph
Mapping g-factors and complex intervalley coupling in Si/SiGe by conveyor-mode shuttling
Mats Volmer, Tom Struck, Arnau Sala et al. (+7 more)
As silicon
spin qubit chips are increasing in
qubit number and area, methods for the screening of
qubit related material parameters become vital. Here we demonstrate the two-dimensional mapping of small variations of the electron g-factor of
quantum dots formed in planar Si/SiGe
quantum wells with precision better than $10^{-3}$ and with nanometer lateral resolution. We scan the electron g-factor across a 40 nm $\times$ 400 nm area and observe two g-factors per QD site which obey a striking
symmetry and bimodal distribution across the area. These two g-factors relate to valley states of the electron in the
quantum dot in agreement with a recent theoretical model. Using conveyor-belt shuttling of entangled electron
spin pairs, complementary to the mapping of the local valley-splitting, we map the g-factor. We compare g-factor and valley splitting maps measured on the same device, and extract the complex intervalley coupling parameter along the shuttle trajectories applying a theoretical model of g-factor dependence on intervalley coupling. These maps will allow unprecedented insights into the
spin-valley dynamics during
qubit manipulation, readout and shuttling and serve as a
benchmark for the engineering of Si/SiGe
heterostructures for large-scale
quantum chips.
Read the full abstract ▾
All authors Mats Volmer, Tom Struck, Arnau Sala, Jhih-Sian Tu, Stefan Trellenkamp, Davide Degli Esposti, Giordano Scappucci, Hendrik Bluhm, Łukasz Cywiński, Lars R. Schreiber
Materials Science
Probing Materials Knowledge in LLMs: From Latent Embeddings to Reliable Predictions
Vineeth Venugopal, Soroush Mahjoubi and Elsa Olivetti
Large
language models are increasingly applied to materials science, yet fundamental questions remain about their reliability and knowledge encoding. Evaluating 25 LLMs across four materials science tasks – over 200 base and fine-tuned configurations – we find that output modality fundamentally determines model behavior. For symbolic tasks, fine-tuning converges to consistent, verifiable answers with reduced response
entropy, while for numerical tasks, fine-tuning improves prediction accuracy but models remain inconsistent across repeated inference runs, limiting their reliability as quantitative predictors. For numerical regression, we find that better performance can be obtained by extracting
embeddings directly from intermediate
transformer layers than from model text output, revealing an “LLM head bottleneck,” though this effect is property- and
dataset-dependent. Finally, we present a longitudinal study of GPT model performance in materials science, tracking four models over 18 months and observing 9–43% performance variation that poses reproducibility challenges for scientific applications.
Read the full abstract ▾
Statistical Mechanics
Beyond the Big Jump: A Perturbative Approach to Stretched-Exponential Processes
Alberto Bassanoni and Omer Hamdi
The problem of sums of independent, identically distributed random variables with stretched-exponential tails exhibits a dynamical phase transition and has recently reemerged in the context of active transport and condensation phenomena. We develop a perturbative expansion for the distribution of the sum that systematically extends the Big Jump Principle beyond its asymptotic regime. The expansion yields explicit higher order corrections that describe moderate deviations, bridging the gap between typical Gaussian fluctuations and the far-tail behavior dominated by single big jump events. In this sense, our approach is complementary to the classical Edgeworth expansion, which provides corrections to the Gaussian core, whereas we construct systematic corrections to the big jump regime. The leading terms reveal the scaling structure governing the crossover between typical and condensed fluctuations, in agreement with large deviation predictions but without relying on its asymptotic limit. We further extend the framework to continuous-time random walks (CTRWs), where stretched-exponential jump statistics combined with
stochastic renewal times generate nontrivial propagators through subordination. This setting is particularly relevant for transport processes with non-Gaussian displacement statistics, where super-exponential or Laplace-like tails emerge from the interplay of rare large jumps and temporal fluctuations. All analytical predictions are supported by numerical simulations.
Read the full abstract ▾
Quantum Gases
Orbital-Dependent Dimensional Crossover of a $p$-Wave Feshbach Resonance
Hang Yu, Liao Sun, Shaokun Liu et al. (+3 more)
We report the observation of a dimensional crossover of a $p$-wave Feshbach resonance in an ultracold,
spin-polarized $^6$Li
Fermi gas confined by a one-dimensional optical
lattice. Using high-resolution atom-loss spectroscopy, we resolve the orbital doublet associated with the $\ml=0$ and $|\ml|=1$ scattering channels over a wide range of
lattice depths. In the weak-confinement regime, the atom loss signal associated with the $|\ml|=1$ branch is stronger, consistent with the twofold orbital degeneracy of the three-dimensional system. As the
lattice confinement increases, the relative loss weight of the two orbital branches evolves continuously toward the quasi-two-dimensional limit, indicating a progressive suppression of relative motion along the
lattice direction. In addition, we observe a systematic confinement dependence of the orbital splitting between the two resonance branches. These results provide an experimental characterization of orbital-dependent $p$-wave scattering in reduced dimensions and motivate future microscopic studies of confined anisotropic scattering.
Read the full abstract ▾
All authors Hang Yu, Liao Sun, Shaokun Liu, Shuai Peng, Jiaming Li, Le Luo
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Engineering symmetry-protected topological states in waveguide arrays
Lavi K. Upreti
The topological classification of a system depends on the discrete
symmetries of its
Hamiltonian. In Floquet photonic waveguide arrays, the abstract
symmetries of the Altland–Zirnbauer (AZ) scheme –
chiral, particle-hole, and time-reversal (for photonics, $z$-reversal) – arise from structural properties of the
lattice, yet a systematic correspondence has not been established. Here, we illustrate this correspondence for a simpler system of one-dimensional waveguide arrays with real coupling coefficients, showing how bipartite structure and $z$-reflection
symmetry alone determine the whole AZ class. We further demonstrate that non-bipartite networks – lacking conventional particle-hole
symmetry,
chiral symmetry, and $z$-reversal
symmetry – can nonetheless support topologically protected boundary states at quasienergy $\varepsilon = \pi$, even in one dimension. The protecting
symmetry – shifted-particle-hole
symmetry – applies equally to higher-dimensional Floquet waveguides.
Read the full abstract ▾
Quantum Gases
Experimental engineering of Floquet topological phases in a one-dimensional optical lattice
Pengju Zhao, Yudong Wei, Zhongshu Hu et al. (+3 more)
Periodic driving enables realization of topological phases without static counterparts. We experimentally realize and detect a one-dimensional anomalous Floquet topological phase in an optical
lattice, using multi-frequency control to manipulate the relative sign structure of the gap windings $(W_0,W_\pi)$ associated with the $0$ and $\pi$ quasienergy gaps. We develop a
lattice-depth modulation scheme that induces staggered nearest-neighbor $s$-$p$ orbital couplings and realize a minimal nontrivial Floquet
topology under single-tone driving. Introducing a second tone, its relative phase controls the effective coupling signs in the $0$ and $\pi$ gaps, thereby tuning the corresponding windings to add and produce a high-winding phase or to cancel while retaining nontrivial gap indices. We read out $(W_0,W_\pi)$ with a band-inversion-surface (BIS)-resolved Ramsey protocol assisted by
lattice-position shaking, which measures relative Floquet phases on the BISs. Controlled quenches further confirm phase-dependent band modifications even at quasimomenta far from resonance. These results establish multi-frequency control with a tunable relative phase as a quantitative route to engineering anomalous Floquet
topology, and demonstrate phase-coherent coexistence of distinct drive modalities.
Read the full abstract ▾
All authors Pengju Zhao, Yudong Wei, Zhongshu Hu, Shengjie Jin, Xuzong Chen, Xiong-jun Liu
Statistical Mechanics
U-Net based particle localization in granular experiments: Accuracy limits and optimization
Fahad Puthalath, Matthias Schröter, Nicoletta Sanvitale et al. (+2 more)
Identifying the positions of granular particles from experimental images is often complicated by their partial overlap in two dimensional projections. Uneven backgrounds and inhomogeneous illuminations can add to the challenge. Conventional image-processing methods are often unable to analyze such images. We show that a deep neural network with an U-Net architecture can provide precise particle positions with a high detection rate. For our challenging test image the network correctly identifies 97.7% of the particles while only creating 2.7 % of false positives. The training of the U-Net requires a number of target images where the position of all particles have been identified by humans. Those positions are then indicated in the target images by setting a small number of mask pixels to white in an otherwise black image. We demonstrate that the design of these masks critically determines performance: mask size controls the resolution of overlapping particles, anti-aliased masks enable subpixel accuracy, and systematic human labeling biases set a measurable lower bound on achievable precision. Our final network achieves an accuracy of the particle coordinate of 3.7% of the particle diameter.
Read the full abstract ▾
All authors Fahad Puthalath, Matthias Schröter, Nicoletta Sanvitale, Matthias Sperl, Peidong Yu
Disordered Systems and Neural Networks
Symmetry-Induced Logarithmic Relaxation in the Quantum Kicked Rotor
Julien Hébraud, Floriane Arrouas, Bruno Peaudecerf et al. (+6 more)
We study the effect of discrete
symmetries on coherent multiple scattering in the
quantum kicked rotor. When the initial momentum is set to zero – as in recent Bose-Einstein condensate experiments – the effective pseudo-disorder becomes even under momentum inversion. The resulting discrete mirror
symmetry of the dynamics profoundly alters spectral correlations: it generates quasi-degenerate Floquet doublets localised at opposite momenta, whose exponentially small splittings produce a hierarchy of exponentially large dynamical timescales. The coherent backscattering and forward-scattering peaks then exhibit a striking non-monotonic
evolution and strongly asymmetric contrasts, followed by an exceptionally slow logarithmic relaxation toward a common asymptotic value – a hallmark of glassy dynamics, here emerging in a fully coherent
quantum system. That such archetypal glass-like behaviour arises from a single discrete
symmetry constraint reveals an unexpected and deep connection between
quantum coherence and slow relaxation phenomena.
Read the full abstract ▾
All authors Julien Hébraud, Floriane Arrouas, Bruno Peaudecerf, Juliette Billy, David Guéry-Odelin, Olivier Giraud, Bertrand Georgeot, Gabriel Lemarié, Christian Miniatura