Materials Science
Carrier Localization in Pnictogen-Based Chalcohalides from Defect-Bound Hot Polarons
Xiaoyu Guo, Junzhi Ye, Cibrán Lopez Alvarez et al. (+19 more)
Pnictogen-based
solar absorbers have gained prominence as promising nontoxic and stable alternatives to lead-halide perovskites (LHPs), but are severely limited by carrier localization, preventing their performance from approaching those of LHPs. Recent efforts have uncovered routes to overcome carrier localization, but these early efforts only considered intrinsic factors. Herein, we push beyond these limited early efforts, examining the role of defects, not only on cold carriers but also hot carriers. Focusing on the structurally one-dimensional pnictogen chalcohalide BiSBr, we find that whilst this material intrinsically does not exhibit carrier localization, vacancies introduced during synthesis or post-treatment lead to pronounced extrinsic self-trapping via the formation of defect-bound hot polarons-excited charge-carriers strongly coupled to local defect-induced vibrational modes. These above-gap defect states divert hot carriers from cooling to the band edge, thus depleting the mobile carrier population. Our findings establish the key role of defect-bound hot polarons in mediating extrinsic localization and offer new mechanistic insights into the interplay between defects,
lattice coupling, and excited-state charge-carrier transport, which are critical to designing efficient perovskite-inspired
solar absorbers.
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All authors Xiaoyu Guo, Junzhi Ye, Cibrán Lopez Alvarez, Maciej Oskar Liedke, Maik Butterling, Mutibah Alanazi, Yi-Teng Huang, Jiajie Wu, Zhilong Zhang, Lars Van Turnhout, Yorrick Boeije, Bofeng Xue, Qingyu Wang, Hugh Lohan, Seán R. Kavanagh, Andreas Wagner, Eric Hirschmann, Robert A. Taylor, Akshay Rao, Edgardo Saucedo, Claudio Cazorla, Robert L. Z. Hoye
Strongly Correlated Electrons
Field-induced multipolar character in the dipolar ground state of the honeycomb rare-earth chalcohalide NdOF
Tiantian Liu, Yanzhen Cai, Mingtai Xie et al. (+6 more)
Field-tunable reconstruction of crystalline electric field (CEF) doublets offers a promising avenue for inducing multipolar character, while its observation in real materials has been little explored so far. Here we establish the honeycomb rare-earth chalcohalide NdOF as such a platform. Raman spectroscopy identifies four CEF excitations at 1.7, 15.6, 19.2, and 80.9~meV, and a Zeeman–CEF analysis reproduces their nonlinear field splitting into seven branches. Magnetization and susceptibility over 0.1–9~T are well described by a CEF model for the total angular momentum $J = 9/2$
manifold, confirming the robustness of the extracted CEF scheme. These results demonstrate a field-driven continuous
evolution of the ground-state doublet from dipolar to dipolar-multipolar character, with pressure providing a complementary tuning knob, establishing NdOF as a model system for exploring the controlled induction of multipolar components in rare-earth magnets.
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All authors Tiantian Liu, Yanzhen Cai, Mingtai Xie, Helin Mei, Anmin Zhang, Feng Jin, Jianting Ji, Zheng Zhang, Qingming Zhang
Materials Science
Topological spin-texture transitions in van der Waals magnets revealed by X-ray Fourier transform holography
Sourav Chowdhury, Soumyaranjan Dash, Michael Schneider et al. (+14 more)
Nontrivial topological
spin-textures, such as skyrmions, merons, bimerons, and skyrmioniums, are envisioned as robust building blocks for future
memory and logic devices. Controllable transformations between these states require a
quantum-mechanical description of electronic degrees of freedom and atomic-scale insight beyond existing phenomenological models. Here, we report an atomic-scale investigation of topological phase transitions and their protection in the two-dimensional van der Waals ferromagnet Fe$_3$GeTe$_2$ (FGT) using a combined experimental-theoretical approach. Synchrotron-based
Fourier transform holography directly images labyrinth domains, isolated skyrmions, mixed labyrinth-skyrmion phases, and skyrmion bags with high spatial resolution. We compare these observations to simulations based on an electronic
lattice Hamiltonian that captures both
metallicity and relativistic
spin-orbit coupling in FGT. By systematically exploring a broad range of temperatures and
magnetic fields, we map the mechanisms governing topological transitions and their stability. This sequential-integrated experimental-theoretical framework advances understanding of
spin-texture interactions and enables precise control of external tuning parameters. Our results establish a platform for creating, stabilizing, and manipulating topological states, paving the way for engineered
spin-texture transitions in next-generation spintronic technologies.
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All authors Sourav Chowdhury, Soumyaranjan Dash, Michael Schneider, Christopher Klose, Chithra H. Sharma, Lisa-Marie Kern, Tim A. Butcher, Josefin Fuchs, Santanu Pakhira, Samik DuttaGupta, Takashi Taniguchi, Kenji Watanabe, Sujit Das, Sanjeev Kumar, Bastian Pfau, Amir-Abbas Haghighirad, Moritz Hoesch
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Open Problem: Separating Geometric and Algorithmic Compression via Cayley-Table Completion
Dongsung Huh
Modern statistical learning theory and deep learning characterize generalization primarily in terms of continuous capacity control (e.g., norm-based regularization, margin maximization, low-rank bias). While highly successful in continuous domains, deep learning consistently fails to extrapolate exact algorithmic or discrete algebraic rules, reflecting a missing inductive bias toward algorithmic complexity minimization. We propose the Cayley-table completion as the canonical testbed for this missing bias, serving as the discrete algebraic counterpart to
matrix completion. Just as
matrix factorization combined with weight decay yields an implicit
geometric bias toward low linear rank, recent results demonstrate that operator-valued tensor factorizations paired with a flatness prior yield an implicit algorithmic bias toward exact discrete associativity. We pose the open problem of establishing formal exact recovery bounds for Cayley-table completion, and challenge the community to generalize continuous flatness priors to autonomously discover broader discrete algorithmic axioms without combinatorial search.
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Statistical Mechanics
Charged Abelian Higgs phase transitions in three-dimensional compact lattice U(1) gauge models with multicharge scalar matter
Claudio Bonati, Filippo Mariani and Ettore Vicari
We consider three-dimensional (3D)
lattice Abelian
Higgs models, with compact U(1) gauge variables coupled to a doubly-charged $N$-component complex scalar field (CLAH). We focus on their phase transitions between the disordered-confined (DC) and ordered-deconfined (OD) phases. When they are continuous they belong to the 3D Abelian
Higgs (AH) universality class associated with the stable charged fixed point (CFP) of the renormalization-group flow of the 3D AH field theory, or scalar electrodynamics, describing $N$-component complex scalar fields minimally coupled to a U(1) gauge field. This CFP exists only for a sufficiently large number of components, i.e., $N \ge N_d^*$, where the integer $N_d^*$ depends on the spatial dimension $d$ (for example $N_4^*=183$). To estimate $N_3^*$, we look for the minimum number $N_{\rm cL}$ of scalar components of 3D doubly-charged CLAH models developing continuous transitions along their DC-OD transition line. For this purpose, we present finite-size scaling analyses of Monte Carlo simulations for $N\in[4,10]$, up to
lattice sizes $L\approx 100$. The results provide evidence of continuous DC-OD transitions for $N=10$, and weak first-order transitions for $N\le 7$. They are not conclusive for $N=8,\,9$. Therefore, we estimate $N_{\rm cL}=9(1)$.
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Mesoscale and Nanoscale Physics
Macroscopic evidence of spatial modulation of conductivity in a microtextured ferromagnetic film
C.P. Quinteros, L. Avilés-Félix, D. Goijman et al. (+5 more)
A 75 nm-thick Fe0.5Pt0.5 film is a
ferromagnetic metal showing striped
magnetic domains in remanence at room temperature. The magnetoresistance is characterized by varying the external temperature and the in-plane
magnetic field intensity, thereby affecting its
magnetic structure. Qualitatively, the resistivity is well described by using the generalized Ohm's law. High-field magnetotransport properties are successfully explained by considering the competition between the expected metallic behavior and the electron-
magnon interaction. In the low-field condition, we size the contribution of the
magnetic texture to the macroscopic magnetotransport response by introducing a new quantity. Consistent with the microscopic modulation of the lateral conduction, low-field measurements reveal inhomogeneities attributed to the spatial distribution of
ferromagnetic domains and domain walls. By carefully analyzing the macroscopic response near the coercive field, the additional contribution to the resistivity is attributed to the domain walls themselves. In fact, this term could surpass the anisotropic term at low temperatures. In summary, this study demonstrates that spatial
magnetic inhomogeneities are not only macroscopically measurable but also comparable in magnitude to other regularly considered terms, mainly at low temperatures.
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All authors C.P. Quinteros, L. Avilés-Félix, D. Goijman, L. Saba, D. Pérez Morelo, L. Granja, M. Granada, J. Milano
Disordered Systems and Neural Networks
Estimates of ground state energies for the quantum SK and 2D-EA models, using deGennes-Suzuki-Kubo mean-field annealing dynamics
Soumyaditya Das, Soumyajyoti Biswas and Bikas K. Chakrabarti
We perform large scale
quantum annealing of the Sherrington-Kirkpatrick (SK)
spin glass up to a system size $N=40000$ to estimate its ground state energy using the deGennes-Suzuki-Kubo mean-field
quantum Ising dynamics, extending the earlier results (reported in Eur. Phys. J. B 98, 226 (2025)). Here we numerically solve the deGennes-Suzuki-Kubo annealing dynamics to obtain the
spin configurations and subsequently the ground state energy for a given system size at the end of the annealing, starting from a
quantum paramagnetic state. The method shows high efficiency, with an overall algorithmic cost of $O(N^3)$ in estimating the energy of the ground state. We later extend this
quantum annealing study to estimate the ground state energies (starting again from the
quantum paramagnetic phase, annealing down to any desired low value of the transverse field) for the Edwards-Anderson (EA)
spin glass model on a square
lattice.
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Disordered Systems and Neural Networks
Enhanced Density Fluctuations Near a Disordered Chiral Topological Transition
Hai-Tao Ding, Sen Mu, Leong-Chuan Kwek et al. (+2 more)
The universal statistics of density fluctuations of localized
quantum states may offer unprecedented opportunities to probe and understand
quantum transport in connection with dimensionality, coherence,
symmetry and disorder. To date, the possible role of topological phase transitions in the fluctuation statistics is not studied yet. Using a Su-Schrieffer-Heeger chain subject to off-diagonal disorder (so that
chiral symmetry is preserved), this work investigates how a disorder driven topological phase transition impacts on the spatial fluctuations of the logarithmic wave-packet density $\ln P(r)$ at distance $r$ from the initial excitation. Away from the transition, in both topological and trivial localized phases, the standard deviation follows the conventional one-dimensional scaling $\sigma[\ln P(r)]\sim r^{\theta}$ with $\theta\simeq 1/2$. Near the transition, however, the fluctuation growth is enhanced: the fitted exponent $\theta$ increases above $1/2$ in a nonmonotonic manner before returning close to $1/2$ at criticality. We interpret this behavior from the energy-resolved density of states and localization length. Near the transition, several energy sectors carry appreciable spectral weight and exhibit competitive decay rates, preventing a single localization scale from dominating the accessible wave-packet tail and thereby enhancing the fluctuations of $\ln P(r)$. Our results establish wave-packet fluctuation statistics as a dynamical diagnostic of disordered
chiral topological transitions and motivate broader studies of fluctuation phenomena in disordered topological
quantum systems.
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All authors Hai-Tao Ding, Sen Mu, Leong-Chuan Kwek, Gabriel Lemarié, Jiangbin Gong
Soft Condensed Matter
The flow deep within granular piles
Aqib Khan and Prabhu R Nott
Grain piles embody the complex mechanics and kinematics of disordered granular materials, including solid-like and fluid-like behaviours, complex kinematics, and preparation history-dependent stress variation. It is widely believed that the bulk of a growing pile is static and flow is confined to a thin layer at the surface, but very few studies have investigated the subsurface kinematics. Here we study the flow within conical grain piles by flow imaging experiments and particle dynamics simulations. We provide direct evidence of continuous plastic flow deep within piles as grains are poured from above, and show that the direction of flow varies smoothly from vertical at the
symmetry axis to parallel to the surface at the periphery. Our findings provide new insight into the kinematics and rheology of granular media, including the nature of creep in seemingly solid-like regions, and have important implications for geophysical phenomena such as landslides and industrial processes.
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Materials Science
Optical Cooling of Nuclear Spins in a CdTe/CdZnTe Quantum Well: The Impact of Kinetic Local Fields on Cooling Efficiency
V. M. Litvyak, P. S. Bazhin, R. André et al. (+1 more)
The efficiency of optical cooling of
nuclear spins in a CdTe/CdZnTe
quantum well is investigated as a function of an external
magnetic field. Our results confirm that there is indeed an optimal external
magnetic field for optical cooling. We associate it with the kinetic local field $B_{KL}$ defined by the heating rate of the
spin-
spin reservoir due to the fluctuations of the hyperfine interaction. We also propose an experimental technique for measuring $B_{KL}$. For our sample we find that $B_{KL}=1.0\pm0.4$ G and it is independent of the electron polarization and pump power. The measured values of the kinetic local fields are in good agreement with a theoretical calculation $B_{KL} = 0.7$ G, taking into account indirect
spin-
spin interactions of Cd and Te
nuclear spins and their considerably different hyperfine constants. The hyperfine constants of the
magnetic isotopes of Cd and Te in CdTe are estimated.
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All authors V. M. Litvyak, P. S. Bazhin, R. André, K. V. Kavokin
Soft Condensed Matter
Microfluidic Oscillatory Rheology of Transported Soft Particles
Matteo Milani, Joshua D. McGraw, Anke Lindner et al. (+1 more)
Microfluidic channels have emerged as useful tools to control dynamic forcing on transported microscale objects, as encountered in emulsions, biological flows, and other soft matter systems. Tailored channel designs enable precise interfacial and bulk rheological measurements of complex materials over a wide range of forcing timescales. After a brief overview of recent experiments illustrating these techniques, we discuss perspectives for future research in this direction, including the study of lubrication films in highly confined droplets, the measurement of fast relaxation dynamics of complex interfaces, and the high-throughput rheological characterization of microscopic soft matter systems ranging from single macromolecules to
cells.
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All authors Matteo Milani, Joshua D. McGraw, Anke Lindner, Stefano Aime
Statistical Mechanics · Cross-listed from quant-ph
Gate Parameter Lee-Yang Zeros and Dynamical Phases in Quantum Circuits
Yunfeng Jiang, Chang Liu, Yu Wu et al. (+1 more)
We propose gate-parameter Lee-Yang zeros of Loschmidt amplitudes as probes of dynamical phases in finite
quantum circuits. We study Floquet
circuits constructed from two-
qubit fSim gates with identical parameters, for which the Loschmidt amplitude becomes a rational function of the gate parameters after a suitable change of variables. At fixed system size and large
circuit depth, the zeros in one complexified gate parameter, with the other held fixed, condense onto limiting curves. In contrast to conventional Loschmidt or Fisher zeros in complex time, these zeros live directly in the complex plane of a tunable gate parameter. We show that the limiting set has two origins: a state-dependent component controlled by overlaps with Floquet eigenstates, and a universal component fixed by the Floquet spectrum. As the remaining gate parameter is varied, the universal zero set reorganizes abruptly, providing a finite-
qubit diagnostic of a dynamical phase transition. We demonstrate this behavior in a Bethe ansatz solvable brickwork
circuit and in longer-range fSim
circuits outside this solvable structure. The mechanism follows from the Beraha-Kahane-Weiss
theorem together with local unitarity, and is therefore spectral rather than a special consequence of integrability.
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All authors Yunfeng Jiang, Chang Liu, Yu Wu, Yang Zhang
Materials Science
Sustainability-Aware Discovery of Dual-Atom Hydrogen Evolution Catalysts via a Unified Machine Learning Framework for Activity and Carbon Cost
Yanmei Zang, Hyun Gyu Park, Gi Beom Sim et al. (+8 more)
Catalyst discovery for green hydrogen has optimized activity alone, deferring economic and environmental costs to stages where they disqualify otherwise promising candidates. Here we introduce a unified machine learning framework that screens catalytic activity and monetized carbon cost in a single pipeline. A machine learning potential predicts hydrogen
evolution activity and stability at density-functional-theory accuracy. A second model, trained on published estimates of the social cost of carbon, converts each candidate's
embodied CO2 into a monetary burden. Screening 460
graphene-supported dual-atom catalysts across 23 transition metals and 20 nitrogen-coordination motifs yields 26 active, synthesizable candidates. The two axes then conflict. The most active candidates span Mn-, Fe-, Zr-, Cr-, Cu-, Ni-, Ti-, Nb-, V-, Pd-, Au-, and Rh-based catalysts, indistinguishable in adsorption energy yet spanning a 58,000-fold range in carbon cost. Joint optimization selects Mn2@2Nf and Zr2@2Nc, matching the best precious-metal activity at tens-of-thousands-fold lower carbon cost, independent of catalyst loading.
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All authors Yanmei Zang, Hyun Gyu Park, Gi Beom Sim, Tae Hyeon Park, Ho Jin Lee, Xiaorong Zou, D. ChangMo Yang, Soohaeng Yoo Willow, Hye Jung Kim, Sunbin Yoo, Chang Woo Myung
Materials Science
Breaking Bipartite and Time Reversal Symmetries by Fusing Porphine Unit in-between two Zigzag-edge Graphene Nanoribbons
R. K. Rohit, Jisvin Sam and Sudipta Dutta
Hybrid structure of two zigzag-edge
graphene nanoribbons with a fused porphine ring in between, results in two distinct nearly degenerate ground states: a semiconducting
antiferromagnetic state and a conducting
ferromagnetic state with unequal and opposite
Fermi velocities of majority and minority
spins, the former having slightly higher stability. Such ground states result from the broken bipartite
symmetry induced by the porphine ring. The incorporation of different transition metal atoms in the porphine cavity reduces their energy difference but keeps their electronic properties mostly unchanged. The splitting of the $d$-orbitals in the distorted square-planar ligand field of porphine produces a high
spin ground state that breaks the global time reversal
symmetry ($\mathcal{T}$). The opposite
Fermi velocities of the majority and minority
spins in the
ferromagnetic ground state and lower sensitivity of the conducting majority
spin channel to the edge disorder, make this class of quasi-one-dimensional hybrid structures promising for dual
spin-filtering device applications.
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Statistical Mechanics
Criticality in the disordered $N$-color Ashkin-Teller model
Youssef Makoudi and Gesualdo Delfino
The $N$-color Ashkin-Teller model corresponds to $N$ Ising models coupled by four-
spin interactions. We consider the two-dimensional case in presence of quenched disorder and use scale invariant scattering theory to determine all the solutions of the exact renormalization group fixed points equations. The weak disorder sector is characterized by a solution that, for any fixed $N$ larger than 1, is a line of fixed points with Ising thermal exponents and continuously varying
magnetic exponents. The number of fixed point solutions allowed by the
symmetries of the model increases at strong disorder illustrating the growing dependence on the distributions of the two random couplings. The presence of some critical exponents which do not depend on the
symmetry parameter $N$ confirms this type of superuniversality as a peculiar feature of random criticality.
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Materials Science · Cross-listed from cs.CV
Low-Magnification SEM May Suffice: Interpretable Deep Learning for Multi-Scale Fracture-Cause Classification in Zirconia-Toughened Alumina
Julian Schmid, Pawel Astankow, Tom Vater et al. (+3 more)
Reliable identification of fracture origins in alumina
matrix composite hip and knee implants is critical for quality assurance and patient safety, yet current fractographic workflows are time-consuming, partly subjective, and reliant on high-magnification scanning electron microscopy (SEM). We present an interpretable
vision-
transformer (ViT) workflow for automated classification of fracture causes in an alumina
matrix composite (BIOLOX delta, CeramTec GmbH) widely used in total joint replacements. A
dataset of 8,493 SEM images (50x-10,000x) was curated from five years of in-production burst and proof tests and annotated into three defect categories defined along the manufacturing chain: green body, hard machining, and material defects. Under severe class imbalance, the fine-tuned ViT reached an accuracy of 0.907 and a macro-F1 of 0.888 in stratified five-fold cross-validation, with a two-stage perceptual-hash/SSIM leakage audit confirming negligible specimen overlap. Notably, performance at low magnification (50x) was comparable to that at high magnification (1k-10kx), indicating that macro-scale features - mirror geometry and hackle line fields - already encode sufficient diagnostic signal. Grad-CAM attributions consistently localised on canonical fractographic cues (mirrors, hackles, pores, machining marks), aligning with established fractographic criteria. Together, these results position interpretable ViTs as a complementary tool for ceramic-implant quality assurance, enabling low-magnification pre-screening and reducing reliance on time-intensive high-magnification inspection.
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All authors Julian Schmid, Pawel Astankow, Tom Vater, Julius Beck, Robert Cichon, Danny Krautz
Statistical Mechanics · Cross-listed from physics.soc-ph
Community detection in subject-subject networks from psychometrics data
Arianna Armanetti, Luca Cecchetti, Eiko Fried et al. (+2 more)
Identifying subgroups of respondents in psychometric data is traditionally addressed with Latent Class Analysis, which requires the number of classes to be specified a priori and can perform poorly when strong inter-item correlations violate local independence assumptions. We propose a network-theoretic alternative based on community detection in subject-subject similarity networks. To suppress the systematic artifacts induced by the factor structure of the items, the similarity is computed in a low-dimensional factor-score space and the null model for modularity maximisation is obtained by removing the leading (global) mode of the similarity
matrix, rather than via the standard Newman–Girvan model. The significance of a detected partition is then assessed against a column-wise resampling null through four complementary observables: the modularity, the differential
entropy of the eigenvector point cloud at two neighbourhood scales, and the overlap of the within- and between-community similarity histograms. On a synthetic
benchmark with controlled mixture signal, all four metrics correctly identify the homogeneous case as null-compatible – including the demanding regime of a
dataset dominated by a single factor – and exhibit a graded departure from the null as the cluster separation grows. Applied to 14 widely used psychometric scales, the pipeline isolates a small group of
datasets supporting a genuine and directly interpretable modular structure, while the remaining scales fall either in a mixed-signal regime or in one compatible with a single homogeneous community. The significance analysis is independent of the specific community-detection
algorithm and provides an operational way to test for modular subject-level structure in questionnaire data.
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All authors Arianna Armanetti, Luca Cecchetti, Eiko Fried, Diego Garlaschelli, Miguel Ibáñez-Berganza
Soft Condensed Matter
A trick of the tail: how electrostatics helps a DNA repair enzyme to localize on nucleosomes
Safwen Ghediri, Guillaume Brysbaert, Fabrizio Cleri et al. (+1 more)
Electrostatic interactions are key to the recognition processes of
proteins and DNA and have been previously documented for the action of repair enzymes. Uracil-DNA glycosylase (UDG) is the first in a sequence of enzymes that act in the base-excision repair process (BER) and whose task is the extraction of uracil bases from
nuclear DNA. The question of how the molecule targets uracil bases in chromatin, in particular in the condensed
protein-DNA complexes of nucleosomes, has only recently become a subject of detailed studies. Here we show that the presence of an arginine anchor motif on the N-terminal tail of UDG can favor its localization on nucleosomes by binding to their acidic patches on their top and bottom surfaces via electrostatic interactions. We argue that this mechanism can play a key role in the detection of uracil defects in nucleosomal DNA.
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All authors Safwen Ghediri, Guillaume Brysbaert, Fabrizio Cleri, Ralf Blossey
Mesoscale and Nanoscale Physics
Zeeman Pumping of Higgs Bosons in the Balian–Werthamer State
Qiao-Ru Xu
Based on equations of motion of an SO(5) pseudo-
spin, we demonstrate a
quantum quench protocol using the
magnetic pulse to excite an $\textit{undamped}$ heavy
Higgs boson in the Balian–Werthamer superfluid (or
superconductor). To achieve that, it is essential to include the dipolar interaction in the effective
Hamiltonian and to calculate the ground state self-consistently. The pumped heavy
Higgs mode has the twisted angular momentum $J=2$ with the projection $J^{\,}_z=0$ and couples to a well-known light
Higgs mode ($J=1$, $J^{\,}_z=0$). The numerical method of 26-point Lebedev quadrature is implemented concretely so as to observe the real-time coupled oscillation.
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Disordered Systems and Neural Networks
Geometry and localization: Probing Localization Landscape Theory on the Bethe Lattice
Lorenzo Tonetti, Leticia F. Cugliandolo and Marco Tarzia
The Localization Landscape Theory (LLT) offers a classical analogy for understanding Anderson localization through an effective confining potential, whose percolation threshold has been proposed to mark the mobility edge. While this correspondence shows striking numerical agreement in three dimensions, its theoretical foundations remain an open question. In this work, we extend the analysis of the LLT on the Bethe
lattice presented in~\cite{Tonetti2026}. In this setting in both the Anderson localization transition and the LLT percolation problem admit exact solutions. Our analysis reveals that the two transitions are distinct, with markedly different critical behaviors. Notably, the LLT percolation transition falls into the standard mean-field universality class, in sharp contrast with the unconventional critical behavior of the Anderson transition on the Bethe
lattice. Nonetheless, the LLT framework reproduces several exact results, capturing nontrivial features of the very low-disorder regime: it predicts the position of the isolated
eigenvalue, the minimal disorder at which both the LLT percolation curve and the mobility edge first appear, and the Aizenman–Warzel lower bound for localization. We also study the dependence of the LLT percolation threshold on the energy shift, evaluate the LLT prediction for the Density of States, and derive several results on the statistical properties of the variables controlling the problem. Finally, we develop an extreme-value analysis showing that the LLT prediction for the Density of States overestimates the amplitude of the tails close to the boundary of the continuous spectrum. These findings provide an exact analytical
benchmark showing that, despite its
geometric appeal, the LLT does not generally reproduce the
quantum critical properties of Anderson localization, while still offering a powerful tool to understand its very low-disorder regime.
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Soft Condensed Matter
An exact density-functional closure for the two-dimensional discrete wormlike chain
Benaoumeur Bakhti
We formulate an exact density-functional description of the angularly discretized two-dimensional (2D) discrete wormlike chain (DWLC) under tension. The central result is a bond-local closure connecting the nearest-neighbor pair distribution $C_{i,i+1}^{rs}$ to the single-site angular densities $\rho_i^r$: $C_{i,i+1}^{rs}C_{i,i+1}^{00}/(C_{i,i+1}^{r0}C_{i,i+1}^{0s})=e^{\bar\beta\,rs}$, with the bond coupling $\bar\beta=\beta\kappa\varepsilon^2/a$. This relation follows directly from the connected Boltzmann weight of the quadratic bending interaction and permits exact integration of the
entropy functional. Variational minimization then yields coupled self-consistent equations for the one- and two-site angular distributions, which we solve by fixed-point iteration. We establish the equivalence of this density-functional formulation to the exact transfer-
matrix solution: the two approaches reproduce the angular marginals and force-extension curves to machine precision. The formulation also recovers the continuum 2D wormlike-chain behavior, including the rigid-rod and random-coil limits of the mean-square end-to-end distance. Using the segment length and persistence length taken directly from Mazur's short-DNA molecular-dynamics study, without additional fitting, the predicted bend-angle statistics agree with the simulation data within the estimated uncertainty. The closure structure extends naturally to nonharmonic local bending interactions and can also be interpreted inversely, allowing measured nearest-neighbor angular correlations to constrain effective coarse-grained bending potentials. These properties establish a direct connection between conformational statistics and local interactions and provide a density-level framework for treating interacting semiflexible-
polymer systems.
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Statistical Mechanics · Cross-listed from physics.data-an
Inverse generalised spin models of answers to questionnaires
Arianna Armanetti, Luca Cecchetti, Paolo Sarti et al. (+2 more)
Network psychometrics conceptualises psychological constructs as emergent properties of systems of interacting items. Energy-based probabilistic models have gained popularity as models of these interactions, but their psychometric application has so far been limited to binary responses, bilinear interactions, and approximated inference methods. To fill these gaps, we here infer and analyse three generalized-
spin models of ordinal questionnaire data: the Ising, Blume-Capel (BC), and Blume-Emery-Griffiths (BEG) models. These are maximum-
entropy models that accommodate ordinal responses on Likert-type scales with an arbitrary number of options, allowing for single-site anisotropy (BC, BEG) and bi-quadratic item interactions (BEG). We prove the concavity of the maximum likelihood estimation of their parameters, as well as the gauge invariance of the Ising and BC models. We introduce a
stochastic gradient ascent
algorithm for maximum likelihood inference, and apply this procedure to eleven psychometric and sociological questionnaire
datasets. Evaluating the predictive ability of the inferred models reveals that the BEG model systematically outperforms Factor Analysis and the other
spin models in capturing the distributions of factors and distances of subject answers to the mean, across all
datasets. By leveraging a competitive interplay between the quadratic and bi-quadratic energy terms, the BEG model uniquely captures individual average-extremist response styles, alongside standard latent factor positioning. Moreover, only the
spin models can account for the non-concavity and multi-modality of factor histograms in the most polarizing questionnaires. Finally, the analysis reveals other highly non-linear traits of ordinal data—such as the fat-tailed distribution of Mahalanobis distances to the mean—that escape satisfactory description by both factor and
spin models.
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All authors Arianna Armanetti, Luca Cecchetti, Paolo Sarti, Diego Garlaschelli, Miguel Ibáñez-Berganza
Materials Science
Spin-Orbit Coupling Effects on the Structural and Electronic Properties of Planar Pentagonal p-MS$_{2}$ (M = Si, Ge, and Pb)
Phuc-Dang Truong, Cao-Huu-Tai Nguyen, Nguyen-Bao-Tran Ngo et al. (+5 more)
Spin-orbit coupling (SOC) plays an important role in determining the structural and electronic properties of recently proposed two-dimensional planar pentagonal materials. In this work, density functional theory calculations are employed to investigate SOC effects in p-MS$_{2}$ systems (M = Si, Ge, and Pb). Our results indicate that the p-SiS$_{2}$ structure is likely unstable, except for p-GeS$_{2}$ and p-PbS$_{2}$. A detailed j-resolved (total angular momentum) orbital analysis reveals that SOC enhances electronic localization, leading to a slight structural contraction and a reconstruction of electronic states near the
Fermi level, this effect becoming stronger for heavier M atoms. While p-GeS$_{2}$ remains metallic, SOC drives a metal-
semiconductor transition in p-PbS$_{2}$ and opening a quasi-direct band gap of about 0.475 eV. In addition, the conduction band minimum state of p-PbS$_{2}$ exhibits pronounced anisotropy along the S-S bonds. These findings provide insight into SOC-driven structural and electronic reconstruction in planar pentagonal chalcogenides p-MS$_{2}$ and suggest that p-PbS$_{2}$ may be a promising candidate for gas-sensing applications.
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All authors Phuc-Dang Truong, Cao-Huu-Tai Nguyen, Nguyen-Bao-Tran Ngo, Khanh-Van Huynh, Jan Minar, Worawat Meevasana, Yen-Mi Tran, Trung-Phuc Vo
Materials Science
Transition metal (group V) doping induced spin and valley polarization in MoS$_2$ monolayer
Shivani Kumawat, Sunil Kumar and B. K. Mani
Doping in two-dimensional materials has emerged as an effective tool for modulating their electronic properties and thereby enabling their multifunctional applications. In this work, we present a first-principles study on induced effective
magnetic moment and
metallicity in MoS$_2$ monolayer by substitutional doping of group-5 transition metal (TM) elements – V, Nb and Ta. From our study, we observe that the V doping induces half-
metallicity, whereas metallic characteristics are observed in the case of Nb and Ta doping. Moreover, V and Ta-doped MoS$_2$ monolayers are observed to show total induced
magnetic moments of 0.922 and 0.624 $\mu_{\rm B}$, respectively. Importantly, the combined effects of strong
spin-orbit coupling (SOC), broken inversion
symmetry, and structural asymmetry is observed to lead to a permanent valley polarization in the V- and Ta-MoS$_2$ systems. In particular, we observed a valley polarization of 121 and 21 meVs for V and Ta-doped MoS$_2$, respectively. Furthermore, an enhanced piezoelectric coefficient for the doped systems is observed compared to pristine MoS$_2$. Notably, the simultaneous presence of half-
metallicity, substantial valley polarization, and enhanced piezoelectricity in V-doped MoS$_2$ establishes this system as a promising multifunctional platform for next-generation spintronic, valleytronic, and piezoelectric nanodevices. Overall, our findings provide fundamental insights into engineering coupled
spin-valley-mechanical degrees of freedom in two-dimensional materials for advanced
quantum and nanoelectronic applications.
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Disordered Systems and Neural Networks · Cross-listed from cs.LG
Kernel Renormalization in Bayesian Deep Neural Networks: the Equivalent Wishart Ansatz in the Proportional Regime
Paolo Baglioni, Christian Keup, Vincenzo Zimbardo et al. (+4 more)
The scaling limit where both the size of the training set $P$ and the width $N$ of a deep neural network grow at the same rate, the so-called proportional-width regime, has been intensely studied for shallow, single-hidden-layer networks. However, extending these non-perturbative results from shallow architectures to deep non-linear networks has proven very challenging. Here we present an effective approximate approach to predict the generalization performance of
Bayesian multi-layer perceptrons (MLPs) of fixed depth $L$ on arbitrary high-dimensional data. We propose an equivalent Wishart Ansatz to capture the dominant
stochastic fluctuations of the hierarchical empirical kernels of MLPs. This allows us to perform a large deviation analysis for the partition function of MLPs in the proportional limit, expressed in terms of a renormalized NNGP kernel. In this description, even strong representation learning in the proportional limit is encoded in at most $L$ scalar order parameters, determined self-consistently. Extending the approach to convolutional architectures (CNNs), we identify a hierarchical local kernel renormalization mechanism, which allows to quantify more complex data-dependent transformations of the large-width kernel in CNNs due to finite-width effects. We test our effective theory against sampling experiments from the
Bayesian posterior of finite deep neural networks with depths $L \sim O(10)$ and $P\sim O(10^3)$ on classic
benchmark datasets, finding overall very good agreement together with two distinct types of systematic deviations.
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All authors Paolo Baglioni, Christian Keup, Vincenzo Zimbardo, Rosalba Pacelli, Alessandro Vezzani, Raffaella Burioni, Pietro Rotondo
Strongly Correlated Electrons · Cross-listed from quant-ph
Channel-agnostic finite-temperature phase estimation averaged over variable grids: reconstruction of Green's function for dynamical mean-field theory
Taichi Kosugi, Hirofumi Nishi, Keito Kasebayashi et al. (+2 more)
For treating correlated electronic systems on
quantum computers, we propose a
quantum-classical hybrid scheme for dynamical mean-field theory (DMFT). In the
quantum part of the scheme, we use modified
quantum phase estimation (QPE)
circuits suitable for the one-particle Green's function (GF) at a finite temperature so that we can extract spectral amplitudes and the excitation energies without knowing the excitation channel invoked at each measurement. In the classical part of the scheme, we adopt an approach that estimates reasonably the GF based on the data collected from the QPE sampling. We dub the approach the QPE averaged over variable grids (QAVG), that may help one to reconstruct the GF via optimization of trial parameters and modeling the probability distributions for various settings of the QPE
circuits. We apply the QAVG-DMFT scheme to SrVO$_3$ to demonstrate its validity via numerical simulations.
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All authors Taichi Kosugi, Hirofumi Nishi, Keito Kasebayashi, Hiroki Takahashi, Yu-ichiro Matsushita
Strongly Correlated Electrons · Cross-listed from quant-ph
Error-corrected phase estimation averaged over variable grids on a trapped-ion quantum computer: hyperacuity spectra of a CO molecule adsorbed onto $\chi$-Fe$_5$C$_2$
Taichi Kosugi, Hirofumi Nishi, Keito Kasebayashi et al. (+2 more)
Quantum phase estimation (QPE) is an underlying technology for extracting the excitation spectra of many-electron systems, yet its practical use on current hardware is hindered by low grid resolution and environmental noises. Here we propose QPE averaged over variable grids (QAVG), a vernier-type approach that combines low-resolution QPE with multiple origin shifts and physically motivated continuous parametrization to reconstruct the spectra accurately. We introduce this approach into an end-to-end workflow for the ab initio-based model system for a CO molecule adsorbed onto the $\chi$-Fe$_5$C$_2$ surface. We perform experiments on Quantinuum H2-2 using both physical QPE
circuits and logical QPE
circuits encoded in the Steane code with offline bit-flip correction. We demonstrate that QAVG accurately reconstructs the spectra with deviations much smaller than the nominal QPE resolution, even when the noisy histograms are used. The cost landscapes averaged over the shifted grids substantially suppress the local minima arising from the spectral leakage, thereby stabilizing the optimization of trial parameters. These results indicate that QAVG provides a robust route to
quantum simulations of correlated spectra toward the era of early-fault-tolerant
quantum computers.
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All authors Taichi Kosugi, Hirofumi Nishi, Keito Kasebayashi, Hiroki Takahashi, Yu-ichiro Matsushita
Mesoscale and Nanoscale Physics
Generation of Bloch Points with Controlled Spin Texture Using Geometrical Boundary Conditions
Naëmi Leo, Daniel Wolf, Alicia Estela Herguedas Alonso et al. (+16 more)
Bloch points are three-dimensional topological singularities in magnetization that play a key role in topological transformations of
spin textures, such as skyrmion creation or annihilation. While
topology often enforces the existence of Bloch points in confined geometries like cylindrical nanowires, deterministic control over their position and
magnetic configuration remains challenging. Here we demonstrate the generation of Bloch points with controlled
spin texture by engineering geometrical boundary conditions in three-dimensional nanomagnets. By introducing a chirality interface between two three-dimensional double-helix nanowires of opposite handedness, forming a kinked, non-collinear structure, we impose competing topological constraints that uniquely define the magnetization configuration surrounding the Bloch point. A saturating
magnetic field nucleates head-to-head or tail-to-tail domain configurations at the chirality interface, producing a Bloch-point domain wall with deterministic polarity, circulation and helicity. This geometrical approach enables full three-dimensional control of Bloch point domain walls allowing deterministic engineering of their
spin texture and its selective coupling to current-induced Oersted fields.
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All authors Naëmi Leo, Daniel Wolf, Alicia Estela Herguedas Alonso, Oleksandr Zaiets, Jakub Jurczyk, Takeaki Gokita, John Fullerton, Dedalo Sanz-Hernandez, Claire Donnelly, Andrea Sorrentino, Eva Pereiro, Lucia Aballe, Peter Fischer, Rachid Belkhou, Claas Abert, Dieter Suess, Axel Lubk, Aurelio Hierro-Rodriguez, Amalio Fernández-Pacheco
Superconductivity
Thickness-driven crossover from conventional to chiral nonreciprocal superconductivity in kagome metal CsV3Sb5
Wei Zhang, Jiangbo Luo, Nikolai Peshcherenko et al. (+10 more)
Superconductivity and its potential applications are governed by the
symmetry of the superconducting order parameter. In the kagome metal CsV3Sb5, most bulk studies indicate conventional s-wave pairing. However, ultrathin flakes exhibit nonreciprocal transport, in particular a zero-field superconducting diode effect, which requires broken inversion and time-reversal
symmetries. Here, using thickness dependent transport measurements, we observe the emergence of non-reciprocal second-harmonic magnetotransport signals and a zero-field superconducting diode effect, accompanied by a pronounced reduction of the out-of-plane coherence length with decreasing thickness. Upper critical field measurements further reveal a dimensional crossover from three-dimensional superconductivity in bulk to two-dimensional superconductivity in thin flakes. These findings indicate a thickness-induced
chiral superconducting phase that breaks both inversion and time-reversal
symmetries in the two-dimensional limit. Our work not only clarifies long-standing controversies regarding the pairing
symmetry in CsV3Sb5, but also establishes thin-flake kagome
superconductors as a versatile platform for engineering nonreciprocal
quantum devices and exploring emergent topological phases.
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All authors Wei Zhang, Jiangbo Luo, Nikolai Peshcherenko, Zheyu Wang, Chun Wai Tsang, Kwing To Lai, King Yau Yip, Kenji Watanabe, Takashi Taniguchi, Junxiong Hu, Yang Zhang, Swee K. Goh, A. Ariando
Materials Science
Finite-temperature micromagnetic model bridging atomic- and macro-scale magnetism
R. Kiefe and J. S. Amaral
A multi-scale finite-temperature micromagnetic model is presented, based on the Landau-Lifshitz equation and the Bernoulli differential equation. This model accurately reproduces classic Maxwell magnetostatics of paramagnets for high temperatures and accurately reproduces standard micromagnetics described by the conventional Landau-Lifshitz model in ferromagnets. The Landau-Lifshitz-Bernoulli (LLBe) model can, by design, directly couple atomic-scale simulations with micromagnetics and output consistent predictions of bulk
magnetic properties at finite temperatures, from below to above the material's Curie temperature. The LLBe model is validated against established solvers: MUMAX3 for zero-temperature micromagnetics, and FEMCE for high-temperature classic magnetostatics. We present an application of the LLBe model by simulating Heat-Assisted
magnetic recording on a thin
magnetic track with local heating, demonstrating the multi-scale finite-temperature capabilities of the LLBe.
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