Materials Science
Facet-Dependent Electronic Properties and Interfacial Point Defect Interactions in WS$_2$/ZnO Heterostructures
Dedi Sutarma and Peter Kratzer
Aiming at two-dimensional materials for high-efficiency optoelectronics, WS$2$/ZnO
heterostructures are computationally screened for their facet-dependent electronic properties and interfacial defect thermodynamics using first-principles hybrid functional calculations. Interface comparison identifies the non-polar ($10\overline{1}0$) $m$-plane as the optimal substrate facet, maintaining a direct 2.42~eV bandgap and a robust type-I band
alignment. Isolated sulfur ($\mathrm{V_S}$) and interfacial oxygen ($\mathrm{V_O}$) vacancies introduce deep non-radiative recombination centers. Conversely, zinc vacancies ($\mathrm{V{Zn}}$) act as shallow acceptors near the valence band edge, contributing to unintentional $p$-type behavior. Analysis of defect pairs reveals that neutral vacancies cluster across the van der Waals gap due to favorable binding energies. Under $n$-type conditions, defects stabilize as charged species. Although inter-layer Coulomb repulsion weakens the binding energy of $(\mathrm{V_S} - \mathrm{V_{Zn}})''''$ pairs, their formation energy drops to 2.61~eV under anion-poor conditions, making the $-4$ cluster the most thermodynamically abundant defect pair at the interface. Furthermore, native $\mathrm{V_{Zn}}$ prevents the
Fermi level rise typically induced by interstitial hydrogen ($\mathrm{H_i}$), distributing donated electrons into shallow acceptor states and preserving host band edge
rigidity. These findings establish a microscopic framework for substrate selection and defect engineering in 2D/3D hybrid light-emitting diodes.
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Strongly Correlated Electrons
Superfluidity without charge order in the attractive Hubbard model on the kagome lattice
Xiaodong Jin, Yingping Mou and Rubem Mondaini
Using auxiliary-field
quantum Monte Carlo simulations, we study the zero-temperature attractive Hubbard model on the kagome
lattice at various relevant electronic fillings. The low-energy physics at $2/3$-density is influenced by the Dirac point at the
Fermi energy, wherein we unveil a superfluid transition at a critical attractive interaction $U_c/t=-4.58(3)$, which belongs to the
chiral-XY universality class. This U(1)
symmetry-breaking is not accompanied by charge order, even for substantially large interaction strengths, in a regime where a description in terms of hardcore
bosons becomes increasingly suitable. An investigation of the latter shows that charge ordering at $1/3$-filling only occurs at interaction strengths much larger than those corresponding to the mapping to the original fermionic model. Additionally, for densities exhibiting van Hove singularities in the non-interacting density of states, our results show that any attractive interaction gives rise to superfluidity, yet again without charge ordering, contrary to recent studies employing mean-field theory.
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Materials Science
Accurate Prediction of the $\alpha \to \beta$ Phase Transformation Temperature in Tin via Full Anharmonic Treatment
Petr Šesták, Matous Mrovec and Martin Friák
Predicting the $\alpha \to \beta$ (grey-to-white) transition temperature in tin presents a longstanding challenge for atomistic simulations, with existing theoretical approaches over- or underestimating the experimental boundary (286 K) by up to several hundred Kelvin. In this work, we construct an Atomic Cluster Expansion (ACE) potential trained on density functional theory data to evaluate the finite-temperature free energies of both phases. Evaluated on the same potential energy surface, the quasi-harmonic approximation predicts a transformation temperature of 377 K, whereas full thermodynamic integration, which accounts for explicit vibrational anharmonicity, yields 288 K. This shift directly quantifies the explicit anharmonic free energy, which is substantial for metallic $\beta$-Sn but negligible for semiconducting $\alpha$-Sn. The anisotropic anharmonicity in $\beta$-Sn is corroborated by its excess heat capacity, temperature-driven renormalization of its vibrational spectrum, and deviations of its atomic forces and displacements from the harmonic reference. Our results demonstrate that capturing full
lattice anharmonicity is essential for predicting the phase stability of tin, while the absolute transition temperature remains limited by the accuracy of the underlying 0 K energetics.
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Statistical Mechanics
Samuel H. Pickering, Max McGinley, Bhavik Kumar et al. (+1 more)
Influence
matrices encode the action exerted on local subsystems by the rest of an extended
quantum many-body system during their
evolution. Thus, knowledge of the influence
matrix facilitates computationally efficient simulations of local dynamics. Here we propose a new systematic approach to generating
quantum circuits with complex dynamics for which the influence
matrices can be written down exactly. In contrast to previous frameworks of this kind, such as dual-
unitary circuits, the resulting influence
matrices are non-Markovian, exhibiting nontrivial temporal correlations. We explicitly construct a broad family of
circuits of this kind, based on dressing free-
fermion (matchgate)
circuits with appropriately chosen interaction terms. We show that, contrary to previous solvable instances, these
circuits produce patterns of correlations that closely resemble that of typical many-body systems. Our approach can be directly interpreted in terms of an error correction scheme where the terms breaking the solvability of the influence
matrices play the role of errors.
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All authors Samuel H. Pickering, Max McGinley, Bhavik Kumar, Bruno Bertini
Materials Science
Stacking Polarity-Controlled Interlayer Photocarrier Dynamics in MoSe2/MoS2 Heterostructures
Gbenga S. Agunbiade, Ting Zheng and Hui Zhao
Control of interlayer photocarrier dynamics is central to optoelectronic applications of van der Waals
heterostructures, yet deterministic and spatially uniform tuning strategies remain limited. Here we show that stacking polarity provides a global control parameter for photocarrier dynamics in MoSe$_2$/MoS$_2$
heterostructures. By comparing hexagonal (2H) and rhombohedral (3R) MoS$_2$
bilayers and engineering opposite interface terminations in 3R stacking, we resolve stacking-dependent interlayer charge-transfer dynamics using ultrafast pump–probe spectroscopy. While charge transfer in the 2H
heterostructure occurs faster than the experimental resolution, the 3R
heterostructures show time-resolvable charge transfer that slows from $0.25$ to $0.37$~ps depending on stacking polarity. Furthermore, the interlayer
exciton lifetime is tuned from $\sim$$40$ to $\sim$$170$~ps. These effects arise from stacking-induced layer polarization in 3R MoS$_2$, which modulates interfacial wavefunction overlap.
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Statistical Mechanics
Interacting hydrodynamic modes in spinless fermions with dephasing noise
Fabian H.L. Essler and Patrik Penc
We study the non-
equilibrium dynamics of spinless
fermions with dephasing noise in the framework of a many-particle Lindblad equation. Using a mapping to the exactly solvable one-dimensional Hubbard model with purely imaginary tunneling amplitude we analyze the Heisenberg-picture dynamics of operators quartic in
fermions and determine their hydrodynamic projections. We construct the relevant diffusive eigenoperators explicitly and show that, in the quartic sector, they can be interpreted as interacting pairs of bilinear hydrodynamic modes. As a consequence, translationally invariant quartic operators generically exhibit non-vanishing diffusive late-time tails, unlike translationally invariant bilinears. Our results show that the hydrodynamic tails of microscopic operators cannot in general be inferred from
symmetry constraints or coarse-grained fluctuating hydrodynamics alone; they also depend crucially on the spatial structure and effective size of the hydrodynamic eigenoperators.
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Soft Condensed Matter · Cross-listed from physics.plasm-ph
Variational approach to Yukawa fluids. II. Instantaneous elastic moduli and sound velocities
S. A. Khrapak and A. G. Khrapak
The variational approach based on the Bogoliubov inequality using the fluid of hard spheres as a reference system is implemented to evaluate instantaneous shear, bulk and longitudinal elastic
moduli, as well as related sound velocities of Yukawa fluids. The remarkable accuracy of this method is documented. In addition, we evaluate the adiabatic sound velocity from an appropriate equation of state and discuss its relation to the longitudinal and bulk sound velocities obtained from the corresponding instantaneous elastic
moduli. The transition between weakly coupled and strongly coupled regimes is analyzed in detail.
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Strongly Correlated Electrons
Charge-6e superconductivity from doping SU(3) spin liquids
Yan-Qi Wang, Boran Zhou, Hui Yang et al. (+1 more)
We propose doping $SU(3)$-symmetric
spin liquids as a route toward charge-$6e$ superconductivity. This generalizes the idea of constructing charge-$4e$ superconductivity from doped $SU(4)$-symmetric phases. As a concrete platform, we study a
bilayer triangular-
lattice Hubbard model with $SU(3)$
spin symmetry and interlayer
antiferromagnetic exchange. Using complementary parton constructions, we analyze doped $\mathbb{Z}_3$
quantum spin liquid and $SU(3)$-related
chiral spin liquids. Doping a $\mathbb{Z}_3$
quantum spin liquid can produce an orthogonal metal with a gauge invariant
fermi surface of charge-$3e$ fermionic trions. Pairing these trions gives a time-reversal-symmetric charge-$6e$
superconductor. Doping Abelian $SU(3)_1$ and $SU(6)_1$
chiral spin liquids yields
chiral charge-$6e$
superconductors with and without residual Abelian topological order, respectively. Doping a non-Abelian $SU(3)_2$
chiral spin liquid leads to a non-Abelian
chiral charge-$6e$
superconductor intertwined with $SO(3)_{-3}$ topological order and supporting non-Abelian $h/(6e)$ superconducting
vortices. We also identify several other phases, including $\mathbb{Z}_3$ orthogonal metal,
quantum anomalous
Hall (
crystal) phases enriched by $\mathbb{Z}_3$ or $\mathbb{Z}_2$ topological order, $SU(3)$-breaking charge-$2e$
superconductors, composite
fermi liquid coupled to non-Abelian gauge field, and descendant
chiral spin liquids. Our results identify doped $SU(3)$
spin liquids as a natural setting where
symmetry, fractionalization, and
topology cooperate to produce charge-$6e$ superconductivity.
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All authors Yan-Qi Wang, Boran Zhou, Hui Yang, Zhi-Qiang Gao
Soft Condensed Matter · Cross-listed from physics.plasm-ph
Variational approach to Yukawa fluids. I. Thermodynamics
S. A. Khrapak and A. G. Khrapak
The excess energy,
entropy, and pressure of a strongly coupled Yukawa fluid are calculated from the variational approach using the fluid of hard spheres as a reference system. As in the case of the one-component
plasma, the Percus-Yevick virial
entropy is appropriate for such calculations and delivers remarkable agreement with available results from molecular dynamics simulations. The agreement with the molecular-dynamics results is particularly impressive in the strongly coupled regime, making this approach a useful predictive tool when numerical data are scarce or not yet available. As an application of the variational approach, we estimate the location of the melting curve in the regime of sufficiently strong screening.
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Statistical Mechanics
Non-monotonic diffusion from nonequilibrium driving
Manish Patel, Ritwick Sarkar, Urna Basu et al. (+1 more)
The
stochastic dynamics of interacting particles far from
equilibrium remains a fundamental challenge in statistical physics. While reciprocal interactions often permit effective one-body descriptions, such reductions generally fail for nonreciprocal interactions, which are ubiquitous in driven and active systems. We develop a unified theoretical framework for interacting particles with reciprocal and nonreciprocal couplings, applicable to the principal classes of active matter, including run-and-tumble, active Brownian, and active Ornstein-Uhlenbeck particles. As a minimal example, we study a passive particle driven by an active particle. On a periodic ring, we show analytically that the driven particle is always diffusive at long times, independent of the microscopic driving mechanism. Analytical predictions and numerical simulations reveal a nonmonotonic dependence of the effective diffusivity on the driving activity, giving rise to both enhanced and suppressed transport. Remarkably, the same behavior occurs in an
equilibrium system driven out of
equilibrium by coupling the driving particle to a higher local temperature. Our framework quantitatively captures both systems, identifies the common mechanism underlying the nonmonotonic transport, and establishes a unified description of transport under active and passive nonequilibrium driving.
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All authors Manish Patel, Ritwick Sarkar, Urna Basu, Debasish Chaudhuri
Materials Science
Pressure-Induced Irreversible Disorder in $\beta^{\prime}$-Mn$_3$(PO$_4$)$_2$: A High-Pressure X-ray Diffraction and Density-Functional Theory Study
Ana Melissa P. Brito, Neha Bura, Pablo Botella et al. (+7 more)
The high-pressure structural behavior of $\beta^\prime$-Mn$_3$(PO$_4$)$_2$ was investigated using synchrotron X-ray diffraction up to 20 GPa combined with density-functional theory calculations. At ambient conditions, $\beta^\prime$-Mn$_3$(PO$_4$)$_2$ crystallizes in a monoclinic structure that exhibits strongly anisotropic compression. The pressure dependence of the unit-
cell volume was described using a third-order Birch–Murnaghan equation of state, and the principal axes of compressibility were determined. Above 14.1 GPa, significant broadening and weakening of the diffraction peaks are attributed to the onset of irreversible pressure-induced structural disorder associated with the loss of long-range crystallographic order. The disordered state persists after decompression to ambient pressure, demonstrating the irreversible nature of the transformation. The calculations accurately reproduce the experimental compressional behavior and provide insights into the microscopic structural
evolution under pressure. Compression is mainly accommodated through distortions of the Mn–O polyhedra, whereas the PO$_4$ tetrahedra behave as comparatively rigid units. Several initially penta-coordinated Mn sites progressively evolve toward octahedral coordination under compression, while selected MnO$_6$ polyhedra exhibit anomalous distortions and elastic softening preceding the onset of disorder. Elastic constant calculations further reveal that the crystalline phase becomes mechanically unstable near the experimentally observed transition pressure. The combined experimental and computational results suggest that the HP response of $\beta^\prime$-Mn$_3$(PO$_4$)$_2$ is influenced by the interplay between framework complexity, anisotropic polyhedral compressibility, and elastic instability, providing new insight into pressure-induced structural degradation in structurally complex phosphate frameworks.
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All authors Ana Melissa P. Brito, Neha Bura, Pablo Botella, Robert Oliva, Alanna Khesley L. da Costa, Fabiana V. da Motta, Mauricio R. D. Bomio, Alfonso Munoz, Joao Elias Rodrigues, Daniel Errandonea
Statistical Mechanics · Cross-listed from physics.chem-ph
Bosonic Condensed Phase Real-time Dynamics from Ring Polymer Molecular Dynamics
Yotam M. Y. Feldman, Sourav Karmakar, Sutirtha Paul et al. (+3 more)
We present a method for approximating real-time correlation functions and
quantum transport coefficients of bosonic condensed phases. The direct evaluation of
quantum real-time correlation functions in the path integral formulation is impossible due to a severe dynamical sign problem. Evaluating imaginary-time correlation functions and inverting them using analytic continuation is famously ill-posed. Ring
polymer molecular dynamics (RPMD) provides an alternative approach resulting in accurate approximations for real-time correlation functions of condensed phases but neglects exchange effects. In this work, we develop a bosonic RPMD method, which is exact in the harmonic, short time, and high temperature limits. A critical enabling observation is that the Kubo-transformed correlation function for
bosons is real only when the correlated observables are symmetric under exchange. We
benchmark the method on harmonic and anharmonic model systems and then use it to directly obtain the Lieb-Liniger gas density-density real-time correlation functions at various temperatures and momentum transfers. This work enables the direct simulation of finite-temperature, real-time dynamics of large bosonic condensed phases using RPMD for the first time.
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All authors Yotam M. Y. Feldman, Sourav Karmakar, Sutirtha Paul, Jacob Higer, Adrian Del Maestro, Barak Hirshberg
Strongly Correlated Electrons
Scaling universal Fermi network toward ground states: A diffusion-Monte-Carlo assessment
Yu-Sheng Li, Saskia Poldmaa, Tzen Ong et al. (+4 more)
In this work, we show that
Fermi Sets—a provably universal neural network architecture for fermionic wavefunctions—can be systematically scaled up to find interacting ground states through energy minimization in a variational Monte Carlo framework. By further performing fixed-phase
diffusion Monte Carlo (DMC) on the optimized neural network wavefunction, we demonstrate that as the network size increases, the variational energy systematically decreases while the energy improvement from DMC collapses monotonically to zero, indicating convergence to the ground state. We illustrate the scaling of
Fermi Sets accompanied by the DMC assessment for interacting electrons in jellium and in a
quantum dot under high
magnetic fields.
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All authors Yu-Sheng Li, Saskia Poldmaa, Tzen Ong, Ahmed Abouelkomsan, Tay-Rong Chang, Hsin Lin, Liang Fu
Other Condensed Matter
Topological Classification of Non-Normalizable Vector Fields
Philipp Gessler, Alessandro Pignedoli, Alexander Neuhaus et al. (+3 more)
Topological classification of physical vector fields conventionally relies on field normalization and homotopy-based invariants. However, when field amplitudes vanish, normalization becomes ill-defined, preventing a direct topological characterization. Here, we introduce a general framework for the topological classification of non-normalizable $n$-dimensional vector fields with compactifiable base spaces by transforming them into $(n+1)$-dimensional normalized vector fields. This construction extends homotopy-based classification to fields containing amplitude zeros. We explicitly demonstrate the approach for one-, two-, and three-dimensional non-normalized vector fields and derive the corresponding topological invariants. The resulting topological charges are robust under continuous deformations and can change only when the
embedding structure becomes singular. Our framework provides a unified route to the topological characterization of non-normalizable fields and opens the door to the study of topological phenomena in a broad range of systems, including
magnetic textures, ferroelectrics, electromagnetic fields, and wave systems.
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All authors Philipp Gessler, Alessandro Pignedoli, Alexander Neuhaus, Frank-J. Meyer zu Heringdorf, Maria Azhar, Karin Everschor-Sitte
Quantum Gases · Cross-listed from quant-ph
Lowering the implementation barrier of neutral-atom quantum computing with agentic workflows
Constantin Dalyac, Alexandre Dauphin, Loïc Henriet et al. (+1 more)
Quantum computers are moving from research laboratories to industrial machines accessible via the cloud and integrated into high-performance computing facilities. However, translating theoretical
quantum protocols into hardware experiments remains a major bottleneck, requiring expertise across protocol design, compilation, simulation, and cloud execution. Here, we introduce an agentic workflow that automates this pipeline on neutral-atom
quantum processors (here two Pasqal QPUs available on the cloud) while keeping the researcher in the loop for critical validation. In three case studies from many-body physics and optimization, the
agent went from published paper or patent to a QPU campaign run overnight. In particular, human intervention was crucial to ensure scientific validity: the
agent selected an inadequate observable in one experiment and constructed a plausible but incorrect hardware diagnosis in another, with both failures detected only through domain-expert review. Finally, we use a second
agent to classify a corpus of 633 Rydberg-array arXiv papers and show that nearly half are implementable on present-day QPUs while identifying specific hardware upgrades needed for the rest. Together, these results demonstrate that agentic workflows provide a practical bridge between theoretical ideas and physical hardware, opening
quantum experimentation to a much broader scientific community.
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All authors Constantin Dalyac, Alexandre Dauphin, Loïc Henriet, Christophe Jurczak
Soft Condensed Matter
Physics-Guided Interpretable Machine Learning Framework for Anomalous Transport in Crowded Media with Tunable Flexibility
Zakiya Shireen and Sujin B. Babu
Transport in crowded media is governed by the interplay of multiple physical mechanisms. Quantitatively disentangling their individual and coupled contributions remains a longstanding challenge because the evolving microstructure continuously modifies their relative influence. Here, we develop a physics-guided interpretable machine-learning framework that couples Brownian Cluster Dynamics simulations with surrogate machine-learning models and SHAP-based interpretation to quantitatively disentangle the individual and coupled effects of total volume fraction, explorer fraction, and template bond flexibility on explorer-particle transport. We demonstrate the framework using binary colloidal systems in which explorer particles diffuse through a template network formed by irreversible bonds with tunable flexibility. Structural descriptors, mean-squared displacement, intermediate scattering functions, and displacement distributions reveal that network formation localizes explorer particles through enhanced transient caging. Bond flexibility emerges as an independent regulator of post-network relaxation by promoting local bond rearrangements that facilitate the release of transiently caged particles without altering the irreversible network
topology. Although crowding and composition dominate the overall transport response, quantitative attribution reveals how the relative contributions of crowding, composition, and template bond flexibility evolve as the confining environment develops. Beyond establishing bond flexibility as a distinct control parameter for relaxation in heterogeneous colloidal networks, this work provides a general physics-guided interpretable machine-learning framework for quantitatively disentangling coupled physical mechanisms in complex transport phenomena.
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Mesoscale and Nanoscale Physics
Strain-Programmable Interior Topological Channels
Jiawei Xia and Shuze Zhu
Topological channels are typically pinned to physical edges or heterogeneous interfaces. Physical edges expose the channels to localized disorder, whereas interface-based designs generally involve material or structural discontinuities. These constraints limit
geometric tunability and can compromise microscopic transport quality. Here we show that smooth strain can program topological channels within a single-component homogeneous
lattice through a mechanically constrained inverse-design framework. A strain-dependent Dirac mass provides a direct
geometric control principle: its zero contour defines the channel path, the contour-crossing topological mismatch fixes the net chirality, and the normal mass gradient sets the confinement width following an inverse-square-root scaling law. Unlike conventional pinned channels, these strain-engineered interior channels permit continuous control over channel geometry and confinement. We demonstrate the approach in a strained Haldane model, realizing straight channels at prescribed orientations, designed curved paths, and multichannel networks associated with higher-Chern-number phases. The resulting channels exhibit quantized transmission and spatial decoupling from boundary-localized disorder, establishing strain as a mechanical design field for programmable interior topological transport.
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Strongly Correlated Electrons
Kinetically induced order from mobility-constrained excitations
Aprem P. Joy and Urban F.P. Seifert
A fascinating feature of strongly correlated systems is that excitations may carry nontrivial
quantum numbers under emergent
symmetries which, in some cases, may strongly constrain their motion. We show that such constrained excitations can play a central role in driving
symmetry-breaking long-range order through a kinetic mechanism: coupling to a local order-parameter field activates the mobility of otherwise constrained excitations, and condensation of the order parameter then enables a large gain in kinetic energy, thereby stabilizing a phase with long-range order. We illustrate this mechanism in two settings: (i) a dimerization instability in a
spin chain with a magnetization dipole conservation law, and (ii) itinerant magnetism of electrons in the Kitaev-Kondo model, where charge carriers couple to local moments that form a
spin liquid. This mechanism becomes operative whenever a finite density of mobility-constrained excitations is present, either through non-
equilibrium preparation or thermal activation. In the latter case, we argue that increasing temperature can, counterintuitively, promote order by enhancing the kinetic-energy gain of thermally activated excitations.
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Materials Science
Integrating moment tensor potentials with finite-element modeling for heat transfer prediction in FLiBe-based molten salt systems
Mikhail Polovinkin, Ksenia Abramova, Oksana Rahmanova et al. (+8 more)
Molten fluoride salts are promising heat-transfer media for advanced molten salt reactors (MSRs), where reliable thermophysical property determination is critical for component design and safety. We present an integrated multiscale framework that couples machine-learning-driven atomistic simulations with finite-element (FE) modeling to predict the heat-transfer performance of FLiBe-based salts in a linear heat exchanger. At the atomistic scale, Moment Tensor Potentials (MTPs), actively trained on ab initio data, are developed for pure FLiBe (66-34 and 74-26 LiF-BeF2 mol%), FLiBe-LaF3, and FLiBe-UF4. These potentials are used in molecular dynamics simulations to obtain temperature- and composition-dependent transport properties (density, viscosity, thermal conductivity, and isobaric heat capacity), which are mapped as inputs to a three-dimensional FE model of the experimental thermal loop. The FE model with literature transport properties reproduces the experimental heat-transfer behavior of pure FLiBe to within 10% in the laminar regime and 18% in the transitional and turbulent regimes, validating the end-to-end pipeline for this composition. The same model with MTP-MD-derived transport properties systematically overestimates the heat-transfer coefficient by 25-28%, an offset consistent with the MTP-MD biases on thermal conductivity and viscosity. Applied to the ternary systems FLiBe-LaF3 and FLiBe-UF4 over 0-5 mol%, the MTP-MD-driven FE model predicts a mean reduction in heat-transfer efficiency of 8-11% relative to pure FLiBe, with UF4 exhibiting the strongest effect. The qualitative ordering of the three systems is the more robust result; the absolute value of the 8-11% figure is contingent on the MTP accuracy. The framework is complementary to high-temperature experiments and provides a physics-based pathway for the rapid screening of MSR coolant formulations.
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All authors Mikhail Polovinkin, Ksenia Abramova, Oksana Rahmanova, Farit Valiev, Andrey Isakov, Andrey Goryachikh, Alexander Galashev, Yurii Zaikov, Dmitrii Maksimov, Alexander Shapeev, Nikita Rybin
Quantum Gases · Cross-listed from physics.atom-ph
Near-deterministic loading of molecular arrays by microwave-assisted collisions
Etienne F. Walraven, Kang Feng, Jonas Rodewald et al. (+2 more)
Molecular tweezer arrays offer great prospects for
quantum simulation, sensing, and computing, and would benefit from methods that enhance loading efficiency. Whereas light-assisted collisions underpin enhanced loading methods for atomic tweezer arrays, this approach cannot be directly extended to molecular arrays due to collisional loss. We show how this collisional loss can be suppressed by shelving molecules in rotationally or vibrationally excited states, so that a shelved molecule interacts with a newly loaded molecule through a repulsive van der Waals interaction. By introducing microwave assisted collisions, we show how to control the final states and the energy released in a collision between a pair of molecules. Following this controlled collision, one of the two molecules can be ejected, and we explore several strategies for ensuring deterministic ejection. Our schemes rely on currently available techniques for
laser-coolable molecules, and we predict achievable filling fractions up to 96%, paving the way for scalable molecular arrays.
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All authors Etienne F. Walraven, Kang Feng, Jonas Rodewald, Michael R. Tarbutt, Tijs Karman
Statistical Mechanics
Fluctuation-dissipation violations in mean-field non-reciprocal spin glasses
Ot Garcés and Demian Levis
We study the out-of-
equilibrium dynamics of the spherical Sherrington-Kirkpatrick model with non-reciprocal asymmetric couplings. Rather than assuming stationarity, we derive the conditions under which the dynamical mean-field equations admit stable time-translational invariant solutions. We analytically solve the asymptotics of the correlation and response functions in the symmetric, uncorrelated and antisymmetric limits, showing that the fluctuation-dissipation
theorem is generically violated in the presence of non-reciprocity despite exponential relaxation, due to broken detailed balance rather than aging. Numerical results for generic asymmetry allow us to interpolate between these solvable limit cases, revealing faster dynamics as the asymmetry increases, together with oscillatory dynamics driven by antisymmetric couplings. These results provide a reference framework for understanding the dynamics of disordered, non-reciprocal systems, disentangling two distinct origins of fluctuation-dissipation violations.
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Statistical Mechanics
Macroscopic wall pressure and microscopic contact load in crowds without egress: social-group cohesion and boundary buffering
Bo-Shiun Shen and Son-Hsien Chen
Crowd safety in confined venues is usually evaluated through evacuation performance or pre-collision avoidance, while direct mechanical hazards in dense gatherings without egress remain poorly understood. We study an Elastic Reorientation Model (ERM), a Social Force Model (SFM), and their coupled dynamics. Post-collision behavior is represented by social-group cohesion ($\gamma_g$) and wall buffering ($\gamma_w$), while risk is quantified by the macroscopic wall line pressure ($P_{\text{wall}}$) and the microscopic maximum per-
agent collision impulse ($\delta p_{\text{max}}$). In the ERM, cohesion and wall buffering generally reduce $P_{\text{wall}}$ by retaining
agents in the bulk, but large groups exhibit a high-$\delta p_{\text{max}}$ hazard window at intermediate cohesion. As $\gamma_g\rightarrow1$, local pairing suppresses cluster growth and shifts kinetic energy from relative to center-of-mass motion, reducing $\delta p_{\text{max}}$. SFM pushing and sliding amplify $\delta p_{\text{max}}$, especially when
agent-
agent and
agent-wall interactions coexist, while active driving raises $P_{\text{wall}}$ through near-wall accumulation. The coupled dynamics produces a wall-pressure/contact-load ($P$-$p$) trade-off. Finite-size scaling reveals an independent-
agent-induced phase boundary at $\gamma_w=0.5$, characterized by a susceptibility discontinuity, and a grouped-
agent-induced continuous phase boundary along a finite segment of $(1-\gamma_w)(1-\gamma_g)=0.5$, characterized by divergent susceptibility and terminating at a critical point. Both disappear in the social-force-free ERM, showing that they emerge from the coupled ERM+SFM dynamics. These results provide mechanistic guidance for crowd-risk mitigation and safety planning in high-density venues without egress.
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Quantum Gases
Tunable state-dependent interactions in collisionally stable mixtures of polar molecules
Hubert J. Jóźwiak, Hanwei Yang, Eugen Dizer et al. (+2 more)
We propose encoding a pseudo-
spin-$1/2$ system in the ground ($v=0$) and first excited ($v=1$) vibrational states of polar molecules. Double microwave shielding simultaneously shields molecules in both states, suppressing two-body losses by orders of magnitude while strictly avoiding three-body recombination. The microwave dressing is state-dependent and results in highly tunable, long-range dipolar Ising exchange ($J_z$), density-density ($V$), and
spin-density ($W$) interactions. These interaction length scales readily exceed the typical interparticle spacing, pushing the molecules deep into the strongly interacting regime. In bulk gases, this enables the exploration of itinerant
quantum magnetism and
quantum droplets with novel anisotropic
spin textures; in optical
lattices, it naturally realizes extended Hubbard and $t$-$J_z$ models, opening new directions in
quantum simulation.
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All authors Hubert J. Jóźwiak, Hanwei Yang, Eugen Dizer, Arthur Christianen, Tijs Karman
Quantum Gases
Ro-vibrational van der Waals interaction between ultracold polar molecules
Kang Feng, Hanwei Yang, Hubert J. Jóźwiak et al. (+1 more)
We describe the ro-vibrational van der Waals interaction between ultracold polar molecules. This interaction is strong, leading to fast elastic collisions and orders of magnitude suppression of collisional loss. This enables evaporative cooling of
Fermi mixtures of molecules in different ro-vibrational states, without active shielding by applying external fields. The scheme is compatible with microwave shielding, where it enables controlled state dependent interactions, opening up new opportunities for
quantum simulation and
impurity physics. The interaction can also be used to stabilize fermionic molecules in optical
lattices, to control interactions in synthetic dimensions, for enhanced tweezer loading, and direct infrared shielding.
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All authors Kang Feng, Hanwei Yang, Hubert J. Jóźwiak, Tijs Karman
Soft Condensed Matter
Crack-Tip Opening as a Probe for Length-Scale Separation in Geometrically Nonlinear Solids
Raúl Lazo-Molina, Mokhtar Adda-Bedia, Mohit Pundir et al. (+2 more)
Soft elastic solids are highly deformable materials where fracture is driven by the complex coupling of
geometric and material nonlinearities. While
geometric nonlinearity (GNL) arises kinematically from the intrinsic capacity of solids to undergo large deformations, material nonlinearity stems from the constitutive behavior unique to each class of materials. Because GNL is a universal feature of all highly deformable solids, establishing its standalone impact is a prerequisite for understanding nonlinear fracture. Here, we focus on brittle soft solids to study the role of GNL alone on the near-tip fields of a static crack under mode I plane-strain conditions, providing a canonical baseline for integrating material nonlinearities in future investigations. By utilizing a compressible St. Venant-Kirchhoff material model, we analyze crack behavior under large deformations in the absence of material nonlinearity. We propose a robust postprocessing methodology based on the crack-tip opening displacement (CTOD) profile and derive asymptotic analytical solutions. Our results reveal a distinct near-tip region where the CTOD departs from classical linear elastic predictions, transitioning into a nonlinear regime dictated by Poisson's ratio. Using a matched-asymptotics approach, we define a physical nonlinear length scale $\lambda_\mathrm{nl}$ that bounds this region and scales quadratically with the far-field stress intensity factor $K_I$. We show that GNL acts as an intrinsic strain-stiffening mechanism sufficient to trigger energy partitioning, effectively shielding the crack tip and imparting an apparent toughening. Ultimately, we conclude that the geometrically nonlinear material model serves as a foundational framework for the broader study of nonlinear elastic fracture mechanics.
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All authors Raúl Lazo-Molina, Mokhtar Adda-Bedia, Mohit Pundir, Rodrigo Arias, David S. Kammer
Disordered Systems and Neural Networks · Cross-listed from physics.optics
Time-Reversal Invariant Topological Photonic Alloy
Feng Ruili, Qu Tiantao, Wu Xianbin et al. (+4 more)
Conventional approaches generate
quantum spin Hall (QSH) and
quantum valley
Hall (QVH) effects by breaking spatial inversion
symmetry across the entire photonic
crystal. Consequently, modulating the bulk transmission gaps within these periodic frameworks typically requires global modification of structural parameters throughout the
lattice, severely limiting device reconfigurability and post-fabrication adaptability. In this work, we demonstrate that global inversion
symmetry breaking is not a prerequisite for inducing topological phases. Instead, local and minimal
symmetry breaking is sufficient. Using a photonic
alloy platform based on random substitutional disorder in a parallel-plate waveguide, we show that a disorder-driven local breaking of z-direction mirror
symmetry and a local breaking of in-plane
symmetry are capable of opening topological gaps to trigger QSH and QVH phase transitions, respectively, thereby supporting robust helical edge states and valley kink states. Rigorous topological characterization via the reflection-phase winding method reveals a striking size-dependent scaling behavior in both configurations, where the threshold doping concentration required to trigger the topological phase transition asymptotically vanishes in the thermodynamic limit. By enabling flexible, on-demand bulk gap engineering simply through random doping tuning rather than global structural reconfigurations, this photonic
alloy platform not only deepens understanding of disorder induced topological physics but also offers a scalable, highly efficient design strategy for integrated topological optical communications.
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All authors Feng Ruili, Qu Tiantao, Wu Xianbin, Shi Xiaoxuan, He Mujun, Zhang Lei, Chen Jun
Other Condensed Matter
Critical Ripples and Dirac Fermions in Crystalline Membranes
Sebastián Bahamondes, Rodrigo Soto-Garrido, Enrique Muñoz et al. (+1 more)
Crystalline membranes hosting Dirac
fermions, with
graphene as the paradigmatic example, combine two low-energy sectors with sharply different dynamics: nonrelativistic flexural
phonons and relativistic-like Dirac quasiparticles. We develop the low-energy field theory of this coupled system at charge neutrality and determine how this dynamical mismatch controls the coupling between the two sectors. In the long-wavelength flat phase, rotational
symmetry ties the renormalization of the leading local scalar strain–density coupling to the scale-dependent bending
rigidity, causing its dimensionless strength to decrease logarithmically. At the same time, flexural modes become parametrically slower than the Dirac
fermions, so the resulting fermionic feedback vanishes as a power law.The flat phase is therefore stable against this perturbation. The physics changes when elastic interactions or electronic softening destabilize the membrane at a finite wavelength, selecting a ripple pattern formed by modes at $\pm\mathbf{Q}$. For an isolated pair of ordering wavevectors, provided that commensurability-induced phase pinning is irrelevant, the transition is governed by the bosonic Wilson–Fisher fixed point, while the Dirac
fermions remain spectators. A genuinely hybrid electronic–structural critical point arises instead when
symmetry permits a mass-type Dirac bilinear to share the ripple's momentum and
quantum numbers, including horizontal-reflection parity. The transition is then described by the
chiral-XY Gross–Neveu–Yukawa universality class. Using the known one-loop critical exponents, we characterize this transition, determine the induced secondary elastic distortion, and show that the fermionic and bosonic velocities lock in the isotropic continuum limit.
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All authors Sebastián Bahamondes, Rodrigo Soto-Garrido, Enrique Muñoz, Vladimir Juričić
Mesoscale and Nanoscale Physics
Abhijit Halder, Harsh Varshney, Snehamoyee Hazra et al. (+7 more)
Quantum oscillations offer a direct probe of
Fermi-surface
topology and electronic degeneracy, yet disentangling both simultaneously across the Lifshitz transitions of multiband systems has remained an open experimental challenge. Here, we use Shubnikov-de Haas spectroscopy on a high-mobility, dual-gated Bernal-stacked tetralayer
graphene (B-4LG) device to quantitatively reconstruct the complete sequence of six distinct
Fermi-surface
topologies-gully, annular, singly connected, and multiband pockets. The extracted oscillation frequencies determine the extremal momentum-space areas and their
spin, valley, and gully-resolved degeneracies, in quantitative agreement with our tight-binding calculations. We further show that a perpendicular
magnetic-field, combined with displacement-field lifts the valley degeneracy through an orbital-Zeeman coupling, producing a single-particle valley splitting of several $meV$, far larger than in
bilayer or trilayer
graphene. Our work demonstrates a framework for tracking
Fermi-surface
topologies and their
flavor degeneracies in multiband
quantum materials.
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All authors Abhijit Halder, Harsh Varshney, Snehamoyee Hazra, Santu Kumar Bera, Souvik Chakraborty, Ujjal Roy, Takashi Taniguchi, Kenji Watanabe, Amit Agarwal, Anindya Das
Soft Condensed Matter
Physical Mechanism of Vacuole Formation in Liquid Droplets
Pranay Jaiswal, Ivar S. Haugerud, William Verstraeten et al. (+3 more)
Vacuoles have been observed in
liquid droplets across variety of experimental systems, ranging from biomolecular condensates composed of
proteins and RNA, to synthetic coacervates formed by charged
polymers or synthetic nanostars. These vacuoles are long-lived domains depleted of droplet material, and their formation is puzzling because the associated increase in interfacial area is thermodynamically unfavorable. Using theory, we show that vacuoles form through a generic mechanism: a local spinodal instability within the droplet. We demonstrate this mechanism in several experimentally relevant scenarios, including temperature quenches and droplets coupled to chemical processes occurring either inside or outside the droplet. Using non-
equilibrium thermodynamics, we develop a theoretical framework that identifies the physicochemical conditions controlling whether vacuoles form and how big vacuoles can become. Our results suggest molecular designs and chemical pathways that promote vacuolation, enabling multi-compartment formation with engineered functions such as enhanced surface catalysis and compartment fission.
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All authors Pranay Jaiswal, Ivar S. Haugerud, William Verstraeten, Kerstin Göpfrich, Job Boekhoven, Christoph A. Weber
Mesoscale and Nanoscale Physics
Quantum metric quadrupoles in elemental bismuth thin films
Rhonald Burgos Atencia, Pavlo Makushko, Gabriele Naselli et al. (+11 more)
The nonlinear transport properties of solids are deeply rooted in the
quantum geometry of their electronic wavefunctions, which is encoded in the
quantum geometric tensor. Its real part, known as the
quantum metric, has been recently identified as a primary origin of nonlinear transport in
quantum materials where time-reversal and inversion
symmetries are not simultaneously present. Consequently, the influence of the
quantum metric on the largest class of materials – non-
magnetic and centrosymmetric systems – has remained entirely elusive. Here, we demonstrate that third-order transport in centrosymmetric materials hosting relativistic
fermions is governed by
quantum metric quadrupoles (QMQs). We show that these QMQs can originate from both the non-Abelian
quantum geometry of bulk three-dimensional Dirac
fermions and the Abelian
quantum geometry of
spin-orbit-coupled surface states. In stark contrast to all zero-field nonlinear transport signatures known to date, the current driven by these QMQs persists as a robust, non-vanishing observable even in highly scalable polycrystalline thin films. We experimentally validate this
quantum metric footprint by measuring nonlinear transport in thin films of elemental bismuth, observing a robust, surface-dominated, and broadband third-harmonic generation that persists up to room temperature. Our findings uncover a hidden role of the
quantum metric in polycrystalline systems, establishing third-order nonlinear transport as a high-precision diagnostic tool of wavefunction geometry under ambient conditions.
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All authors Rhonald Burgos Atencia, Pavlo Makushko, Gabriele Naselli, Debottam Mandal, Paul Chekhonin, Sergey Kovalev, Steffen Kober, Zhe Wang, Igor Veremchuk, Oleksiy Pashkin, Fabian Ganss, Maria Teresa Mercaldo, Denys Makarov, Carmine Ortix