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Physics Condensed Matter

cond-mat Watch Condensed Matter

Friday 5 June

Soft Condensed Matter · Cross-listed from math-ph

A survey on rigorous results for the dynamics of periodic FPU chains

Dario Bambusi, Andrea Carati and Alberto Maiocchi

In this paper we review some analytic results on the dynamics of the FPU system. In the first part of the paper, having in mind that the FPU Hamiltonian and the Toda Hamiltonian are close each other, we present some results on the action angle variables of the Toda system and deduce some stability properties for the dynamics of the FPU system. We first focus on the case of finitely many particles and then we study the limit $N\to\infty$. We present also some results on the continous limit of the Toda chain showing that it is well described by a couple of KdV equations. Then we study directly the dynamics of the function interpolating the FPU system and show that the dynamics is Hamiltonian and that the Hamiltonian is very close to a function of the first three Hamiltonians of the KdV hierarchy. In the second part of the paper we present some results valid in the thermodynamic limit, according to which the time autocorrelation functions of some suitably constructed observables decay slowly implying lower bounds on the thermalization times of the system.
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Statistical Mechanics

Phase lag enhances synchronization in coupled oscillators with inertia

Sudo Yi, Cook Hyun Kim, Heetae Kim et al. (+1 more)

The second-order Kuramoto model with inertia exhibits different dynamical behaviors than the first-order KM without inertia. A central difference is its lower synchronization due to the emergence of multiple synchronized clusters with different frequencies. We aim to investigate how such lowered synchronization can be improved by applying external perturbations to the system in a steady state, for example, a symmetry-breaking phase lag to a subset of oscillators. We find that this phase lag steers the primary cluster along a specific path and enables it to merge with higher-order clusters, thereby enhancing global synchronization. Our results reveal a mechanism by which controlled phase lag can improve entrainment in inertial oscillator systems, with possible implications for synchronization control in inertial oscillator networks.
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All authors Sudo Yi, Cook Hyun Kim, Heetae Kim, B. Kahng

Mesoscale and Nanoscale Physics

Light-tunable quantum metric non-linear Hall response in Berry dipole semimetals

Debashree Chowdhury and Awadhesh Narayan

We investigate the effect of light on quantum metric-mediated intrinsic nonlinear Hall conductivity in Berry dipole semimetals. We discover that light induces a tunable asymmetry in the off-diagonal part of the quantum metric, which is manifested by an asymmetry in the quantum metric dipole. We show that the nonlinear response can be tuned directly by the light amplitude. In particular, we note that the direction of the nonlinear Hall signal changes when the light amplitude is increased beyond a threshold value. Light thus emerges as a promising stimulus to control the quantum geometric response in topological semimetals.
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Materials Science

Iron-mediated on-surface synthesis of substrate-decoupled graphdiyne monolayers

Alice Cartoceti, Simona Achilli, Gianni Conti et al. (+9 more)

Graphdiynes are emerging two-dimensional sp-sp$^2$ carbon materials with electronic structures complementing those of graphene, yet their on-surface synthesis is limited by the persistence of metalated intermediates or yields disordered covalent networks. Here, we report an iron-assisted route to covalent hydrogenated graphdiyne monolayers on Au(111) from 1,3,5-tris(bromoethynyl)benzene. Low-temperature scanning tunnelling microscopy, X-ray photoelectron spectroscopy and density functional theory show that Fe scavenges chemisorbed Br byproducts forming FeBr$_2$, in turn promoting the removal of Au adatoms from the organometallic network, thus enabling its metalated-to-covalent conversion under mild thermal treatment. Subsequent annealing removes FeBr$_2$ and yields covalent, ordered domains weakly coupled to the substrate. Scanning tunnelling spectroscopy, combined with density functional theory, reveals a semiconducting gap of about 1.6 eV associated with carbon p$_z$ frontier orbitals. This Fe-mediated on-surface synthesis strategy provides a route to atomically precise, weakly substrate-coupled graphdiyne networks and offers a design principle for two-dimensional carbon semiconductors.
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All authors Alice Cartoceti, Simona Achilli, Gianni Conti, Eliecer Pelaez-Sifonte, Alessio Orbelli Biroli, Sabine Maier, Francesco Sedona, Paolo D'Agosta, Francesco Tumino, Andrea Li Bassi, Jorge Lobo-Checa, Carlo S. Casari

Statistical Mechanics

Fate of the Ising universality class under nonreciprocal interactions

M. Akritidis, A. Garcés, A. Vasilopoulos et al. (+3 more)

We study the critical behavior of a two-dimensional Ising model with nonreciprocal vision-cone interactions, which explicitly violate reciprocity and detailed balance. Extensive Monte Carlo simulations and dynamic renormalization-group analysis show that the asymptotic critical exponents remain fully consistent with the equilibrium Ising universality class over a broad range of nonreciprocal coupling strengths $\lambda$. In contrast, dimensionless quantities such as the Binder cumulant and the correlation-length ratio display pronounced anisotropic nonequilibrium corrections and systematically deviate from their equilibrium Ising values. The renormalization-group flow further demonstrates that the nonreciprocal perturbation is irrelevant at the Wilson-Fisher fixed point while generating a finite shift of the critical temperature proportional to $\lambda^2$. Our results demonstrate the remarkable robustness of two-dimensional Ising criticality against this class of directional interactions.
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All authors M. Akritidis, A. Garcés, A. Vasilopoulos, M. Carosi, D. Levis, N.G. Fytas

Materials Science

Electric-field induced trends of exchange interactions in transition-metal trilayers

Moinak Ghosh, Stefan Heinze and Souvik Paul

Using density functional theory, we have performed a systematic study of the Heisenberg pairwise exchange interaction and the beyond Heisenberg multi-spin higher-order exchange interactions in unsupported transition-metal trilayers in the presence of external electric fields. The systems consist of a hexagonal atomic Fe layer sandwiched between 4$d$ (Ru, Rh, and Pd) and 5$d$ (Ir) transition-metal layers. Both fcc and hcp stackings of the 4$d$ overlayer have been taken into account. To scan a large part of the magnetic phase space, we have calculated the energy dispersion of spin spirals without and with applied electric fields up to $\pm 1.0$ V/Å. We find that the energy dispersion remains qualitatively the same upon applying the electric fields and the magnetic ground state remains unchanged. The exchange constants obtained by fitting the energy dispersions exhibit a linear dependence on the electric field up to values of about $\pm 0.5$ V/Å. The sign of the calculated pairwise and higher-order exchange constants remain unchanged with electric field, however, their values and field induced variation are sensitive to the 4$d$ overlayer. The changes are on the order of a few percent for the nearest-neighbor exchange constant and up to a few ten percent for beyond nearest-neighbor constants. The higher-order exchange constants are calculated based on the total energies of multi-$Q$ states, such as the $uudd$ and the 3$Q$ state. Similar to the pairwise exchange constants, we find a nearly linear field dependence of the higher order constants at small electric fields and variations of up to ten percent. We study the spin-dependent screening of the electric field for the three trilayers based on the spin- and orbital-decomposed electronic states.
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Materials Science

Characterization of Nonlinear Dynamics in Semiconductors in Frequency Domain using Modulated Photoexcitation

Attia Awan, Rong Tang, Zhou Kang et al. (+1 more)

Carrier dynamics in semiconductors is inherently complex owing to the coexistence of different excited species, such as free carriers and excitons, and their interactions among themselves and with traps and phonons. It is usual to use time-resolved responses to identify the processes that contribute to the dynamics. However, the responses often are non-exponential, leading to ambiguity in the interpretation. Here, we propose a frequency domain method to characterize nonlinear dynamics in semiconductors using CdSe as the test system. We show that by analyzing the frequency components in the total photoluminescence induced by a pair of phase-modulated beams, the parameters, such as rates of different types of recombination of free carriers and excitons, can be evaluated. The method can be used as a simple diagnostic tool to characterize ultrafast processes that are relevant to the functionality of semiconductor devices.
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All authors Attia Awan, Rong Tang, Zhou Kang, Khadga Jung Karki

Mesoscale and Nanoscale Physics

Spin SWAP operation in double quantum dots at the LaAlO3/SrTiO3 interface

A. Sierant, J. Czarnecki, B. Szafran et al. (+1 more)

Progress in the fabrication of nanoscale transition-metal-oxide heterostructures makes these platforms promising candidates for the realization of spin qubits, mainly due to the $d$-character of their electronic structures, which could potentially result in a reduction of hyperfine interactions and spin decoherence. Here, we present a systematic study of spin control within the SWAP operation in double quantum dots embedded in a two-dimensional electron gas at the LaAlO$_3$/SrTiO$_3$ interface. Our analysis starts with a study of single-electron spin dynamics, focusing on the influence of spin-orbit and interorbital coupling on the spin evolution. In this case, our findings are supported by semiclassical calculations based on the Bloch equations, which show good agreement with full quantum mechanical simulations. We then simulate the SWAP operation by analyzing the crossover between two regimes: (i) large quantum dots, where the electronic structure is dominated by the $d_{xy}$ orbitals and the spin dynamics is affected primarily by Rashba-type spin-orbit interaction; and (ii) small quantum dots, where higher-energy orbitals $d_{xz/yz}$ contribute to the electronic structure, leading to a significant reduction in the SWAP fidelity. In the first regime, particularly relevant from the application point of view, we analyze in detail the anisotropy of the SWAP operation induced by the spin-orbit coupling.
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All authors A. Sierant, J. Czarnecki, B. Szafran, P. Wójcik

Mesoscale and Nanoscale Physics

Layer-Polarization-Driven Metal-Insulator Transition in multi-band Graphene Moire' Superlattices

Harsimran Kaur Mann, Simrandeep Kaur, Harsimran Singh et al. (+7 more)

Graphene/hBN moiré superlattices provide a highly tunable platform for exploring emergent quantum phases in low-dimensional systems. Here, we investigate the moiré superlattice formed between hBN and ABA-stacked trilayer graphene (TLG), an inherently multi-band system. We demonstrate that the moiré potential is not merely a perturbation but a tool to hybridize the distinct massless and massive electronic sectors of TLG. By applying a perpendicular displacement field to tune layer polarization, we drive a fundamental reconstruction of the electronic band structure. Specifically, increasing the displacement field evolves the system from a multi-band regime to an effectively single-band regime at low energies, accompanied by a metal–insulator transition at the hole-doped secondary Dirac point. This transition originates from a redistribution of carriers across graphene layers that selectively enhances their coupling to the extrinsic moiré potential. Quantum capacitance measurements provide direct evidence for the suppression of the density of states at the hole-side secondary Dirac point, consistent with gap opening and the emergence of a displacement-field-tuned band gap. Theoretical calculations reproduce these observations and identify layer-selective coupling to the moiré potential as the underlying mechanism. These results demonstrate electrical control of an emergent insulating phase in a low-dimensional moiré system, and highlight that layer polarization and layer-selective coupling in multi-band moiré heterostructures provide a powerful route for engineering topological and correlated phases through band structure reconstruction and electron interactions.
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All authors Harsimran Kaur Mann, Simrandeep Kaur, Harsimran Singh, Yashashwani Garg, Amogh Waghmare, Mohit Kumar Jat, Kenji Watanabe, Takashi Taniguchi, Manish Jain, Aveek Bid

Statistical Mechanics

A Machine-Learning Based Approach to the Evaluation of the Critical Scaling Behavior of Anisotropic Spin Systems

Alina A. Chubarova, Ivan A. Mamonov, Marina V. Mamonova et al. (+2 more)

Computational models adequately representing phase transitions and evaluating the critical system parameters are essential for the understanding of the properties of a wide range of materials. Here we propose a machine learning (ML)-based approach to the identification of the critical point in anisotropic spin systems. Our approach implies training of a convolutional neural network (CNN) model from the correlation matrices obtained by Monte Carlo simulations. Next, the pretrained model is employed as a fast estimator of the critical temperature, which can be extracted in several complementary ways from the CNN model inference, this way improving the robustness of the analysis. The ML-based estimates obtained in this study are in very good agreement with the reference Monte Carlo simulation results, while computational costs are about 10x lower compared to the classical thermodynamic approach.
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All authors Alina A. Chubarova, Ivan A. Mamonov, Marina V. Mamonova, Mikhail I. Bogachev, Pavel V. Prudnikov

Strongly Correlated Electrons · Cross-listed from quant-ph

Scalable Quantum Algorithms for Gutzwiller Projection

Byungmin Kang, Hyunwoong Kwon, Vito W. Scarola et al. (+1 more)

Quantum simulation requires highly accurate input states. Gutzwiller-projected Bardeen-Cooper-Schrieffer (BCS) states provide physically motivated input states for solving strongly correlated lattice models, but their preparation on a quantum computer is hindered by the non-trivial nature of the Gutzwiller projection. We construct scalable quantum algorithms for this task by combining a circuit construction for arbitrary BCS states with the amplitude amplification for Gutzwiller projection (AAGP) procedure. AAGP yields a quadratic reduction in the number of projection queries compared with measurement-based postselection and leads to substantially improved fault-tolerant resource scaling. For projected BCS states optimized for the square-lattice $t$-$J$ model, we find that the projected-state weight decreases exponentially with system size, but the quadratic improvement is still large enough at physically relevant finite sizes to make a decisive practical difference. In particular, for a 100-site benchmark, AAGP reduces the required number of projection queries by about seven orders of magnitude. These results establish AAGP as an enabling input-state preparation protocol for projected BCS states in quantum simulation.
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All authors Byungmin Kang, Hyunwoong Kwon, Vito W. Scarola, Kwon Park

Materials Science · Cross-listed from physics.optics

Circular Raman responses from angular-momentum inequivalence in CoSi

Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki et al. (+8 more)

Circularly polarized Raman scattering in solids exhibits distinct phenomena such as Raman optical activity (ROA) and chiral-phonon-induced frequency splitting, whose relationship has remained unclear. Here we show that these seemingly different responses can be understood within a common framework based on the inequivalence of phonon states carrying opposite crystal angular momenta. Using helicity-resolved Raman spectroscopy of the chiral crystal CoSi, we find that ROA and frequency splitting arise from different symmetry channels, namely axial multipolar symmetry and structural chirality, respectively. First-principles calculations reproduce both effects and clarify their symmetry origins. These results establish angular-momentum inequivalence as a unifying principle of circular Raman responses and link helicity-resolved Raman spectroscopy to the angular-momentum structure of chiral phonons in topological materials.
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All authors Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki, Hikaru Watanabe, Rikuto Oiwa, Ryotaro Arita, Satoshi Iwasaki, Yoshiki Yasuoka, Yusuke Kousaka, Yoshihiko Togawa, Takuya Satoh

Statistical Mechanics

Impact of capacity volatility and input substitutability on supply chain resilience

Jaeseok Hur, Juha Jang, Meesoon Ha et al. (+1 more)

Supply chains are intrinsically vulnerable to stochastic shocks due to their sequential production dependencies. Building on the Feld-Barthelemy framework, we investigate how capacity volatility and input substitutability determine critical demands in stochastic supply chains. By modeling production capacity with a truncated normal distribution, we show that in long supply chains, reducing capacity volatility is often more effective than increasing average capacity, emphasizing the need for firm-level synchronization. Furthermore, introducing a modified Leontief-type production function reveals that input substitutability effectively disperses stochastic shocks. Supplier diversification inherently raises critical demands, even under fixed maximum capacities, by introducing the effect of network topology that independently enhances the resilience of physical stock. Our findings demonstrate that mitigating capacity volatility and structurally diversifying supply routes are just as crucial to supply chain resilience as traditional inventory expansion.
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All authors Jaeseok Hur, Juha Jang, Meesoon Ha, Hawoong Jeong

Strongly Correlated Electrons

Complex Temperature-dependent Thermal Conductivity in a Sawtooth Chain Magnet Fe$_\mathrm{2}$SiSe$_\mathrm{4}$

Kunya Yang, Feihao Pan, Liran Wang et al. (+12 more)

Geometrically frustrated magnets provide an ideal platform for exploring the interplay between lattice geometry and spin degrees of freedom. Here, we investigate the interactions between lattice and spin via thermal-transport measurements on the triangular sawtooth-lattice olivine magnet Fe$_\mathrm{2}$SiSe$_\mathrm{4}$, which exhibits successive magnetic transitions at $T_1 = 110$ K (antiferromagnetic) and $T_2 = 50$ K (ferrimagnetic). Although phonons dominate the thermal conductivity, its temperature dependence displays a pronounced double-peak structure arising from spin-phonon coupling. In the intermediate temperature range between $T_1$ and $T_2$ , resonant scattering of phonons by magnetic excitations around 5 meV produces a broad maximum around 60 K. Below $T_2$, the resonant spin-phonon scattering is strongly suppressed, leading to a rapid increase in thermal conductivity upon cooling and a pronounced low-temperature peak near 11 K, characteristic of heat transport governed by conventional phonon scattering mechanisms. Notably, this low-temperature peak is enhanced by a factor of $\sim 5$ compared to the broad maximum at higher temperatures. These results demonstrate the strong sensitivity of thermal transport to spin-lattice interactions and highlight spin-phonon scattering as an effective mechanism for tailoring thermal conductivity in geometrically frustrated magnets.
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All authors Kunya Yang, Feihao Pan, Liran Wang, Chenglin Shang, Ying Zhu, Xiancai Hu, Sanjiang He, Xinrun Mi, Long Zhang, Aifeng Wang, Yisheng Chai, Frederic Hardy, Christoph Meingast, Peng Cheng, Mingquan He

Materials Science · Cross-listed from physics.chem-ph

Distilling first-principles accuracy into compact machine learning potentials for condensed-phase chemistry

Sijia Chen, Niamh O'Neill, Benjamin X. Shi et al. (+1 more)

Accurate machine learning interatomic potentials (MLIPs) have made first-principles-quality potential energy surfaces increasingly accessible for condensed-phase chemistry, but their inference cost can still limit the sampling needed to compute experimentally relevant observables. In this work, we combine transfer learning and knowledge distillation to construct compact "student" models that retain the accuracy of much larger "teacher" models obtained by applying transfer learning to foundation models. The resulting students reduce production simulation cost by roughly an order of magnitude, making high-accuracy sampling practical for challenging condensed-phase problems. We demonstrate this across three problems of increasing sampling complexity: finite-temperature NPT simulations of ice Ih, classical and path-integral simulations of liquid water over 240-370 K, and path-integral umbrella-sampling simulations of water dissociation at the anatase TiO2(101)/water interface. In all cases, the distilled students reproduce the target observables of their teachers more reliably than models of the same size trained directly on the limited reference data. The liquid-water student, distilled from a {\Delta}-learned CCSD(T)-quality teacher, reproduces thermodynamic, structural, transport, and nuclear quantum properties over the full temperature range studied. At the TiO2/water interface, distillation makes PIMD umbrella sampling practical and shows that nuclear quantum effects lower the dissociation barrier by roughly 2 kcal/mol and shift the molecular-dissociated free energy difference into quantitative agreement with recent solid-state 17O NMR measurements. Our work demonstrates how knowledge distillation can make accurate MLIPs practical for the sampling methods needed to connect condensed-phase reaction thermodynamics with experiment, notably for interfacial chemistry and catalysis.
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All authors Sijia Chen, Niamh O'Neill, Benjamin X. Shi, Venkat Kapil

Superconductivity

Magnetic Field Walls in Flat-band Superconductors

Guodong Jiang, Aaron Dunbrack, Tero T. Heikkilä et al. (+1 more)

Superconductors of different types have distinct magnetic properties; for example, they can form Abrikosov vortices or alternating normal-superconducting domains. We predict that, in flat bands, a superconducting phase exhibiting walls of magnetic flux is stable in an applied magnetic field. This phase relies on the lack of a single particle energy penalty for forming condensates of any momentum in flat bands and, consequently, their superconducting free energy being a negative and periodic function of the vector potential at low temperatures. Using a minimal lattice-periodic model of free energy, we study two types of soliton modes of the wall phase: the kink and breather solitons. They determine the lower critical field and the high-field behavior of the wall phase, respectively. The competition between the walls and vortices in flat bands is also discussed. Our results suggest that flat bands help sustain superconductivity in the presence of large magnetic fields.
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All authors Guodong Jiang, Aaron Dunbrack, Tero T. Heikkilä, Päivi Törmä

Thursday 4 June

Materials Science · Cross-listed from cs.AI

PhononBench-MP40: a spectrum-resolved benchmark dataset for phonon stability

Wen-Kao Li, Ze-Feng Gao and Zhong-Yi Lu

Imaginary phonon modes remain a practical bottleneck in computational materials screening because otherwise plausible structures can be locally dynamically unstable under a chosen workflow. Here we present PhononBench-MP40, a spectrum-resolved benchmark dataset of Materials Project-derived crystals for workflow-defined phonon stability. The dataset starts from 47,969 MP40 workflow tasks and provides 46,899 completed records with paired stability labels and local phonopy YAML spectra, including 16,683 Stable records and 30,216 completed-phonon unstable records. A further 1,067 relaxation failures are reported separately rather than merged into the completed phonon denominator. The release centers on the local YAML spectrum: the stability label, the lowest sampled frequency and any threshold-dependent relabeling are derived from that spectrum. The dataset is openly available through Science Data Bank at https://doi.org/10.57760/sciencedb.38735. A companion GitHub repository provides the calculation code and lightweight access utilities. PhononBench-MP40 provides an auditable reference for workflow-defined stability classification, minimum-frequency analysis, threshold studies and failure-aware triage, while keeping the reference workflow, data schema and interpretation boundaries explicit.
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Soft Condensed Matter

Shear-Induced Structural Convergence but Formation-History-Dependent Yielding in Sequentially Gelled Binary Colloidal Networks

Alexander Kaltashov and Safa Jamali

Multicomponent colloidal gels can exhibit mechanical responses that depend not only on interaction strengths but also on the temporal pathway by which their networks form. Here, we use particle-based simulations to investigate the steady-shear deformation of binary colloidal gels assembled by sequential gelation with tunable delay time and dominant interspecies attractions. Although varying the gelation delay produces markedly different quiescent morphologies, ranging from well-mixed networks to coarse shell-core structures, steady shear drives the systems toward structurally convergent, mixed states as quantified by cluster, connected-component, and coordination analyses. This structural convergence, however, does not imply rheological equivalence. The transient stress response remains strongly dependent on gelation delay and interspecies attraction strength. For moderate interspecies attractions, increasing delay enhances the stress overshoot, particularly at high shear rates. For stronger interspecies attractions, initially heterogeneous gels exhibit two-step yielding at low shear rates, indicating distinct deformation and restructuring processes. These results show that sequential gelation can imprint a persistent rheological memory in binary colloidal gels, even when shear substantially erases differences in common structural descriptors.
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Strongly Correlated Electrons

Stability and thermodynamic properties of bound magnetic polarons in ferromagnetic semiconductors: Beyond the Gaussian approximation

Henryk Bednarski

The Gaussian approximation for thermodynamic fluctuations of host magnetization fails for ferromagnetic semiconductors like GdN near their Curie temperature $T_c$, producing unphysical instabilities in the bound magnetic polaron (BMP) free energy. We extend the Dietl-Spalek theory beyond the Gaussian level by incorporating full cubic and quartic anharmonic terms of the Ginzburg-Landau-Wilson functional. We develop two complementary generalizations: (i) a perturbative non-local treatment for finite spin correlation length, and (ii) a non-perturbative resummation of local fluctuations into a closed exponential form. The latter is rigorously justified by a novel polaronic Ginzburg criterion. By including variational optimization of the donor orbital radius, we quantitatively describe magnetic self-trapping. Applied to GdN ($T_c \approx 55$ K), our theory eliminates Gaussian divergences and predicts thermodynamically stable, ferromagnetically ordered BMPs with spontaneous internal spin splitting persisting deep into the paramagnetic phase. For realistic exchange coupling ($J_c = 400$ meV), this robust local ordering survives up to $T^* \approx 155-160$ K. Pronounced orbital contraction signals magnetic self-trapping, with a characteristic kink in the optimal Bohr radius at $T_{char} \approx 79$ K. We reveal a critical exchange threshold ($J_c \approx 330$ meV) triggering cooperative collapse into a highly localized small polaron state, and identify an optimal donor-concentration window near the metal-insulator transition maximizing $T^*$. These results establish a microscopic mechanism for persistent BMP-mediated ferromagnetism well above bulk $T_c$ via polaron percolation, suggesting clear experimental signatures (optical spin splitting, anomalous magnetoresistance) testable in GdN and related compounds.
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Mesoscale and Nanoscale Physics

Hierarchical Disorder in Moiré Exciton Photoluminescence Probed by Spectral-Descriptor Correlations

Katsunori Wakabayashi

Hyperspectral photoluminescence (PL) maps of moiré transition-metal dichalcogenide heterobilayers encode rich information about the underlying disorder, but extracting it is hampered by the ambiguity of assigning individual spectral peaks. We show that the spatial correlations among a set of simple, peak-decomposition-free spectral descriptors – such as the centroid energy, the dominant-peak energy, and a sharp-line fraction – provide a peak-decomposition-free route to infer features of that disorder. Different descriptors act as filters that select different components of a multi-scale disorder landscape – a smooth, micron-correlated background and a dense set of localized traps – and therefore acquire different spatial correlation lengths. The central prediction is a correlation-length hierarchy, $\xi(E_{\rm cent}) \ge \xi(E_{\rm dom})$, which we derive by splitting the dominant-peak energy into a smooth background part and a short-range trap-switching fluctuation. The same picture explains the measured inter-descriptor correlations, including the near-perfect anticorrelation $\rho_{\rm S}(\Delta E_{\rm cd}, R_{\rm HL}) \approx -0.978$, which we show to be a robust geometric trend for spectra dominated by a common emission-envelope asymmetry. Benchmarked against phenomenological simulations, Hamiltonian diagonalization, and the measured MoSe$_2$/WSe$_2$ descriptor correlations, the framework turns descriptor maps into a quantitative, peak-decomposition-free probe of slow disorder and local traps in moiré excitons and, more broadly, in disordered semiconductor emitters.
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Materials Science

Atomic-scale phase-field modeling for 2D ferroelectrics including non-Gaussian fluctuations

Kairi Masuda and Yu Kumagai

Atomic-scale phase-field modeling extends the phase-field framework down to the level of individual atoms by treating the probability density of atomic vibrations as a field variable and constructing a corresponding free-energy functional from this atomic field together with interatomic potentials. In this way, the framework has the potential to visualize local thermodynamic states with atomic-level resolution, just as conventional phase-field modeling has served as a computational microscope for free energy, stress, and related quantities at mesoscopic scales. However, existing formulations mainly assume Gaussian probability distributions for atomic vibrations, which limits their applicability to more complex and heterogeneous systems such as surfaces. In this work, we generalize the atomic-scale phase-field methodology by extending the free-energy functional to include non-Gaussian fluctuations. We apply this approach to monolayer SnTe in the NVT ensemble and show that the predicted equilibrium polarization is in better agreement with molecular dynamics simulations and that the ferroelectric-to-paraelectric phase transition is successfully reproduced. Furthermore, by decomposing the entropy on a per-atom basis, we visualize atomically resolved maps of local entropy and find that Sn atoms contribute more strongly to the entropy than Te atoms at high temperature, which is a driving factor of the ferroelectric-to-paraelectric phase transition. These results broaden the applicability of phase-field approaches to a wider range of atomic systems and suggest a route toward an atom-resolved theory of phase transitions based on high-resolution thermodynamics.
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Materials Science

Reactivity-Informed Machine Learning for Performance Prediction and Design Space Exploration of Alkali-Activated Slag

Qiyao He, Zhanzhao Li and Kai Gong

Establishing quantitative relationships among mix design, raw material properties, curing conditions, and performance remains a long-standing challenge in cementitious materials, particularly for alkali-activated materials with variable precursor and activator chemistry. Here, we curated the largest literature-derived alkali-activated slag (AAS) dataset to date, comprising over 3100 compressive strength records, 155 chemically distinct ground granulated blast-furnace slags (GGBSs), and 24 attributes incorporating precursor chemistry, fineness, and reactivity. Multiple machine learning (ML) algorithms were benchmarked across progressively enriched feature scenarios, demonstrating that integrating GGBS compositions, fineness, curing conditions, and specimen geometry improves predictive performance. The average metal oxide dissociation energy (AMODE), a physically interpretable representation of precursor reactivity, provides a compact alternative descriptor to explicit oxide compositions while enabling comparable predictive performance. Model interpretation revealed physically consistent trends from heterogeneous data, including non-monotonic effects of Na2O dosage and silicate modulus, reduced predicted strength at higher water content and larger specimen size, and coupled oxide-level effects more coherently represented by AMODE than by individual oxide contents. Statistically constrained design space exploration reveals reactivity-dependent trade-offs among strength, embodied CO2 emissions, and cost. The design maps identify high-strength regions with substantially lower CO2 emissions than OPC-based references at similar cost. Overall, this work demonstrates how reactivity-informed ML can extract physically meaningful trends from heterogeneous AAS data and guide source-dependent binder design. The curated dataset is publicly accessible to support advances in cement and concrete research.
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Materials Science

Engineering magnetic anisotropy and ferromagnetism in topological Kagome metal GdV6Sn6 via Nd substitution

Santosh Karki Chhetri, M.M. Sharma, Jian Wang et al. (+4 more)

Kagome metals with the formula RM6X6 (R = rare-earth, M = 3d transition metal, and X = Sn/Ge) provide a rich platform for exploring magnetic and electronic phenomena, with tunable properties enabled by the combination of rare-earth elements and transition metals. In this study, we report the structural, electrical and magnetic properties of Kagome metal (NdxGd1-x)V6Sn6. We demonstrate that substituting lighter Nd atoms at the Gd site tunes the complex magnetic ground state of GdV6Sn6 into a ferromagnetic-like one. Moreover, the isotropic magnetization of GdV6Sn6 becomes anisotropic, with the c-axis emerging as the easy axis. Transport measurements reveal a strong coupling between magnetism and electronic properties, with negative magnetoresistance observed at low magnetic fields in all compositions. In addition, a fourfold anisotropy component tends to emerge in end compounds at higher magnetic fields. These findings highlight the role of rare-earth substitution in tuning magnetic anisotropy and magneto-transport behaviour in RM6X6 compounds, featuring a non-magnetic Kagome layer, with potential implications for spintronic and topological applications.
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All authors Santosh Karki Chhetri, M.M. Sharma, Jian Wang, Dinesh Upreti, Gokul Acharya, Md Rafique Un Nabi, Jin Hu

Disordered Systems and Neural Networks

Persistent currents in signed directed networks

Davide Cipollini and Guido Caldarelli

Network theory can be fruitfully used to describe quantum coherence in physical systems. To that purpose we introduce persistent currents in signed directed networks by interpreting the signed magnetic Laplacian as an effective Hamiltonian and the associated edge phases as a discrete gauge field. In a canonical ensemble, persistent currents arise as thermodynamic responses to variations of gauge-invariant fluxes. We show that these fluxes are naturally defined on the cycle space of the network, and that the resulting currents are constrained to the divergence-free subspace and decompose onto independent cycles. This formulation provides a direct generalization of persistent currents from rings and lattices to arbitrary topologies. Detection of persistent currents provides a signature of the quantum phase coherence supported by the network, and a direct signature of the geometry of its cycle space. Such a mapping, not only allows a practical way to deal with quantum coherence for a variety of situations in the field of quantum technologies, but it also allows a physical interpretation of the importance of the Laplacian operator in graph theory, linking its role to the one of Hamiltonian (i.e. a tight-binding one) in physical systems. To test the power of the method, we construct a signed directed network that reproduces the Hofstadter butterfly spectrum.
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Soft Condensed Matter

Beyond Snap-Fit: Optimizing the Lifting Capabilities of a Partial Cylindrical Shell

Grace K. Curtis, Ian M. Griffiths and Dominic Vella

The cylindrical snap-fit is a ubiquitous fastening method that is both simple to manufacture and assemble, and yet secure. It consists of a partial cylindrical shell that `snaps' onto a cylindrical object. We build on previous work to describe the mechanics of the cylindrical snap-fit as a naturally curved thin elastic shell placed atop a rigid cylinder; we investigate the shell's behaviour when subject to a point force pushing it onto or pulling it off the cylinder. We classify the possible contact regimes according to whether the shell has a nonzero lifting capacity. We term situations with lifting capacity `grip-fits' and show that this includes both the snap-fit and a `stick-fit' regime, which allows lifting despite not having the characteristic `snap'. Regimes without lifting capacity are also characterized for completeness. We show that the different regimes may be characterized entirely by the shell/cylinder geometry and the coefficient of friction. We then consider different metrics for the lifting performance in the grip-fit regime. Our analysis reveals the trade-offs between assembly force, disassembly force, lifting force, and clamping force, providing design principles for secure lifting, easy detachment, and safe handling of fragile objects.
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Materials Science · Cross-listed from astro-ph.HE

Plasticity of Neutron Star Crusts

Matthew E Caplan, Nevin T Smith, Ashley J Bransgrove et al. (+1 more)

We use first-principles molecular dynamics simulations to study the deformation and breaking of neutron star crusts. When simulating with strain rates several orders of magnitude slower than prior work, we find a new regime of steady plastic flow beyond the breaking point that is independent of the initial crystal structure. Polycrystals exhibit a robust transition from linear elasticity to perfect plastic flow at shear strains of $\epsilon = 0.05$, while monocrystals break at $\epsilon = 0.11$ and then flow plastically. The universal post-break plasticity may arise because the crystal self-consistently assumes a defect density to accommodate the imposed strain rate. If broken crusts can re-anneal to large crystal sizes, crust breaking may repeat with implications for magnetar bursts and flares.
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All authors Matthew E Caplan, Nevin T Smith, Ashley J Bransgrove, Charles J Horowitz

Mesoscale and Nanoscale Physics · Cross-listed from physics.flu-dyn

Fluctuation-induced and quantum effects in nanofluidic transport

Adrien Sutter, Peter Gispert, Baptiste Coquinot et al. (+2 more)

The hydrodynamic wall has traditionally been considered a featureless object, whose only role is to provide a boundary for fluid flow. Yet, there is now ample evidence that at nanometer scales, liquid flows are sensitive to the wall's internal – in particular, electronic – degrees of freedom. Here, after reviewing the experimental evidence for nanoscale liquid-electron couplings, we present the theoretical advances that have allowed for their quantitative understanding. We discuss how a quantum description of the liquid-solid interface reveals the influence of electron dynamics on classical fluid transport, in the form of the fluctuation-induced quantum friction effect. Quantum friction is at the root of liquid-electron coupled transport phenomena, that may be combined into a hydro-electronic transport matrix. We present analytical formulas for the hydro-electronic transport coefficients, that allow for their quantitative estimation in practical cases; we further outline the potential consequences of coupled liquid-electron transport for the water-energy nexus. Fluctuation-induced and quantum effects at liquid-solid interfaces represent an emerging interface between fluid dynamics and condensed-matter physics, and a largely uncharted territory for both theory and experiment.
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All authors Adrien Sutter, Peter Gispert, Baptiste Coquinot, Lydéric Bocquet, Nikita Kavokine

Materials Science

Symmetry-Protected Phonon Topology and Low Lattice Thermal Conductivity in Square-Octagonal Chalcogenides

Nair Surabhi Suresh, Mondal Chiranjith, Alam Aftab et al. (+1 more)

Unconventional lattice geometries provide an effective platform for realizing symmetry-protected topological phonon states that can strongly influence lattice heat transport. In this work, we explore the relationship between topological phonon band features and thermal transport in square–octagonal (so) chalcogenide monolayers, namely MoS2 and SnS, by combining first-principles calculations with phonon Boltzmann transport theory. Symmetry analysis reveals the presence of nontrivial phonon band topology in the form of symmetry-protected nodal lines. Crossings between nodal lines carrying different symmetry eigenvalues produce fourfold Dirac points that enhance the phonon group velocity (vg), whereas nearly flat nodal lines lead to strong suppression of vg. The coexistence of these features, together with substantial phonon softening and enhanced anharmonic scattering around the topological band crossings, markedly suppresses the lattice thermal conductivity ($\kappa_l$). As a result, room-temperature $\kappa_l$ values of 4.0 W/mK for so-SnS and 18.7 W/mK for so-MoS2 are obtained, representing reductions by more than a factor of two and eight, respectively, relative to their hexagonal phases. Our results uncover a direct connection between phonon band topology and heat transport in two-dimensional materials, highlighting lattice symmetry and topological band engineering as promising routes for tailoring thermal properties. These findings further suggest opportunities for designing topological phononic and thermoelectric devices with controllable heat flow.
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All authors Nair Surabhi Suresh, Mondal Chiranjith, Alam Aftab, Singh Nirpendra

Strongly Correlated Electrons

Field-rigid Ising antiferromagnetism with giant spin-flip fields in Van der Waals UOTe

Zackary Rehfuss, Shannon Gould, Joanna Blawat et al. (+9 more)

Van der Waals antiferromagnets provide a route to thickness-controlled magnetic order, but few combine high-temperature Ising order with conducting, correlated, and topological electronic structure. Here we show that UOTe realizes this combination. Magnetic susceptibility reveals a strongly anisotropic paramagnetic response, while neutron diffraction establishes c-axis antiferromagnetic order below $T_N \simeq 150$ K with an order-parameter exponent $\beta = 0.14$, close to the two-dimensional Ising value. Torque magnetometry further shows that the ordered state remains well described by a uniaxial antiferromagnet below the high-field transition. Pulsed-field magnetization up to 73 T shows that the ordered state survives to very large fields applied along the c axis before entering a broad metamagnetic regime that begins near 50 T, and remains unsaturated at the highest measured field. Angle-dependent proximity detector oscillator measurements show that the metamagnetic instability is set by the field component along the ordered moment direction, providing direct evidence for Ising-like field rigidity. UOTe therefore establishes a field-rigid Ising antiferromagnet with giant spin-flip fields in a compensated Van der Waals metal, where high-temperature c-axis order, quasi-two-dimensional magnetic criticality, Kondo-associated uranium 5f hybridization, metallic transport, and symmetry-enabled topology coexist in a single material.
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All authors Zackary Rehfuss, Shannon Gould, Joanna Blawat, Christopher Broyles, George Xu, Yiqing Hao, Huibo Cao, Thao Dinh, Suyang Xu, Dave Graf, John Singleton, Sheng Ran

Quantum Gases

Riemann Rarefaction Waves in a Strongly Interacting Fermi Gas

Eric A. Wolf and Martin Zwierlein

We investigate the expansion of a homogeneous, strongly interacting Fermi gas released into vacuum in a “shock tube” geometry. At unitarity, where the gas is scale invariant and nearly inviscid, we find that the resulting rarefaction wave dynamics are self-similar and in excellent agreement with Riemann's solution of the Euler equation for all temperatures probed. Probing interactions away from unitarity within the BEC-BCS crossover, we observe increasing deviations from the Riemann solution as viscosity increases. However, even on the BCS side, where the sound diffusivity is increased twenty-fold, self-similarity is still approximately preserved. This may reflect how 1D Navier-Stokes rarefaction flows approach Euler self-similar solutions at long times. Our work demonstrates the utility of strongly interacting Fermi gases for the study of nonlinear hydrodynamics in a highly controllable setting.
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