Statistical Mechanics
Martingale theory for heat and phase-space contraction in heterogeneous diffusions
Jing Qin, Nariya Uchida and Édgar Roldán
We investigate martingale properties of heat dissipated by generic non-
equilibrium overdamped Langevin dynamics with multiple dimensions and transport coefficients that may depend explicitly on time and/or space. We find quantitative criteria that establish that heat dissipation may exhibit transient martingale (time-conserved), submartingale (time increasing), and supermartingale (time decreasing) properties in Langevin dynamics with drift coefficients with spatial non-linear dependencies. Furthermore, we reveal a tight link between the heat statistics at stopping (e.g. first-passage) times with that of a functional quantifying the phase-space contraction in the system dynamics. The theoretical results are used to predict the statistical properties of the heat dissipated by a spherical microscopic particle subject to
gravity and double-layer forces and hydrodynamically interacting with a rigid wall, whose validity is confirmed by numerical simulations. These results extend the scope of
stochastic energetics by revealing a non-trivial relation between heat fluctuations' statistical properties and the non-linear features of non-
equilibrium processes.
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Statistical Mechanics · Cross-listed from hep-th
Exploring multi-parameter optimization in FRG
A. Codello, G. P. Vacca and D. Zarrilli
The use of nonperturbative Wilsonian functional renormalization group (FRG) equations within an unavoidable approximation scheme produces physical results that depend on the choice of the coarse-graining regulator. This dependence of physical observables on the regulator can be minimized according to the principle of minimal sensitivity (PMS). For the 1PI formulation based on the Wetterich-Morris equation, we propose to investigate the optimal choice within a space of compactly supported
polynomial regulators parametrized by a set of variables. We test this approach using the derivative expansion of the effective average action up to fourth order, applying it to the scalar field theory representing the three-dimensional Ising universality class and minimizing the dependence of the anomalous dimension on the regulator. At fourth order, we find appreciable corrections to the critical exponents that improve the predictions, compared to previous one parameter analyses. We also observe families of compact regulators that rapidly converge towards an optimal functional form as a small number of parameters is progressively introduced.
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Materials Science
A Gaussian process coarse-grained potential for Na-montmorillonite
Yalda Pedram, Yaoting Zhang, Laurent Brochard et al. (+2 more)
Hydraulic transport in compacted bentonite is
diffusion-controlled and governed by the hydration and microstructure of sodium montmorillonite (Na-MMT). Experiments cannot resolve how platelet interactions govern pore structure, transport and stiffness, while existing coarse-grained models smooth hydration oscillations or require manual corrections. We develop a tabulated potential combining Morse interactions between platelet centre and edge sites with a Gaussian process regression correction trained on all-atom potentials of mean force. It captures the hydration-induced complexity of the potential-of-mean-force profiles, including the three-water (3-W) hydration minimum and transfers across geometries, layer-charge variants and unseen configurations. Applied to monodisperse and polydisperse Na-MMT assemblies at dry densities of 0.8-1.3 g cm^-3, the model captures the 3-W to 1-W transition, loss of non-interlayer porosity and
evolution of pore structure, random-walk tortuosity,
diffusion and stiffness. Predicted
diffusion agrees with compacted Na-bentonite measurements.
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All authors Yalda Pedram, Yaoting Zhang, Laurent Brochard, Chang Seok Kim, Laurent Karim Béland
Materials Science
First-principles theory of phonon renormalization from nonlinear electron-phonon interactions
Florian Kluibenschedl, Matthew Houtput, Jacques Tempere et al. (+3 more)
Electron-
phonon interactions renormalize
phonon frequencies and lifetimes and are central to the dynamical properties of solids. While these effects are usually described within linear electron-
phonon coupling, the role of nonlinear electron-
phonon interactions for
phonon properties remains largely unexplored. In this work, we study
phonon renormalization arising from the long-range linear one-electron-one-
phonon and the nonlinear one-electron-two-
phonon interactions within a diagrammatic framework. We derive the corresponding self-energy diagrams, which depend on the chemical potential and temperature, and evaluate them from first principles for the two polar
semiconductors LiF and KTaO$_3$. In both materials, the two interaction channels renormalize the
phonon spectrum in qualitatively distinct ways. The linear contribution is sharply localized near the Brillouin-zone center, whereas the nonlinear process couples an incoming
phonon to other branches throughout the spectrum. As a result, it renormalizes
phonons across the entire Brillouin-zone, with a pronounced temperature dependence governed by the thermal occupation of those branches. This behavior provides a clean experimental signature of the one-electron-two-
phonon coupling. While the nonlinear
phonon renormalization is small in LiF, it is somewhat larger in KTaO$_3$, which we attribute to its greater number of thermally populated
phonon branches at room temperature. Our results establish a general framework to assess nonlinear electron-
phonon effects on the
phonon properties in materials with stronger
lattice fluctuations, including soft
semiconductors such as lead-halide perovskites.
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All authors Florian Kluibenschedl, Matthew Houtput, Jacques Tempere, Cesare Franchini, Mikhail Lemeshko, Ragheed Alhyder
Materials Science
Spin-Lattice Dynamics and Interactions in Magnonic Spinels
Hari Paudyal, Yuri Suzuki, Michael E. Flatté et al. (+1 more)
Minimizing
magnetic damping while understanding
spin-
lattice interactions remains a key challenge for magnonics. We show site-specific Al/Li ordering in spinel ferrites drives a ferrimagnetic insulating state, quenching the Fermi-level density of states. Ab initio calculations reveal collective acoustic modes alongside sub-
lattice-selective optical modes on tetrahedral and octahedral networks, providing a microscopic understanding of substitution-driven
spin dynamics. Crucially, the low-frequency
magnon and acoustic
phonon modes intersect, driving strong hybridization for low-loss technologies.
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All authors Hari Paudyal, Yuri Suzuki, Michael E. Flatté, Durga Paudyal
Materials Science
Magnon-Phonon Dynamics in Multidimensional Antiferromagnetic Oxides
Yogendra Limbu, Michael E. Flatté and Durga Paudyal
Antiferromagnetic oxides offer a compelling paradigm for magnonics. Combining ab initio and
spin Hamiltonian modeling, we map Cr2O3 from bulk to monolayer limits, verifying stability via
phonon spectra. Contrary to previously predicted half-metallic ferromagnetic monolayer phases, we conclusively demonstrate that monolayer and bilayer configurations preserve an antiferromagnetic
semiconductor ground state despite systematic gap narrowing. Intersecting
magnon and
phonon branches drive strong hybridization, establishing low-dimensional Cr2O3 as an ideal platform for
quantum spintronics.
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Strongly Correlated Electrons
Lyapunov-controlled thermalization: an exact real-time example
Jonas Loy and Jan C. Louw
A verified Kubo-Martin-Schwinger (KMS) relation, after a drive has ceased, is not sufficient evidence to prove
equilibrium. We demonstrate this in a large-$N$ large-$q$ Sachdev-Ye-Kitaev (SYK) quench protocol. Although all post-quench
fermion correlators are exactly thermal, a second quench back to the initial
Hamiltonian reveals hidden
memory of the initial state. It is encoded in correlators connecting to times before the first quench. This
memory is an extensive nonequilibrium (NEQ) witness with its decay rate being the Lyapunov exponent $\lambda_L$. Thus $\lambda_L$ sets the rate at which the state becomes effectively indistinguishable from a Gibbs state. Despite being a
unitary interacting many-body system, the complete NEQ real-time
evolution is obtained exactly in the large-$N$, large-$q$ limit, making the setup ideal for analytically studying thermalization.
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Strongly Correlated Electrons
Multiconfigurational Analysis of Local Electronic Structure of $\mathrm{RuO_2}$ Using Relativistic Embedded Clusters
Zhosan I. A., Lomachuk Yu. V., Maltsev D. A. et al. (+2 more)
We present a multiconfigurational, relativistic embedded-cluster study of the local electronic structure of ruthenium dioxide ($\mathrm{RuO_2}$), a candidate altermagnetic material. Starting from free $\mathrm{Ru}$ ions, we progressively build up the local environment through a $\mathrm{Ru+Q_6}$ electrostatic model, a bare $\mathrm{[RuO_6]^{8-}}$ ligand model, and finally a high-accuracy $\mathrm{RuO_6}$@CTEP embedded cluster that reproduces the crystalline surroundings. All systems are treated at the SA-CASSCF and NEVPT2+SOC levels of theory to capture strong electron correlation and
spin-orbit coupling on an equal footing. While the formal local site
symmetry of the $\mathrm{Ru}$ sites in $\mathrm{RuO_2}$ is orthorhombic ($D_{2h}$), we find that the calculated $4d$-orbital energy spectrum and its splitting pattern behave much closer to the higher tetragonal ($D_{4h}$)
symmetry, preserving a strong quasi-degeneracy among the relevant $4d$ orbitals. Since the local $xy$ quadrupolar order responsible for altermagnetic
spin splitting in independent-particle models relies on this
symmetry reduction, its suppression by orbital quasi-degeneracy offers a natural explanation for why altermagnetism is not observed in bulk $\mathrm{RuO_2}$ experiments, in contrast to the robust altermagnetic signatures reported in strained thin films.
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All authors Zhosan I. A., Lomachuk Yu. V., Maltsev D. A., Moiseev I. A., Andreev O. Yu
Statistical Mechanics
Formal Fluctuation-Response Relations for Non-Stationary Systems: The Dynamic Conjugate Variable
Igor M. Sokolov
Fluctuation-response relations (FRRs) connect the linear response of a system to an external perturbation with properties of spontaneous fluctuations in the unperturbed system. We provide a simple derivation of FRRs for non-stationary dynamics following an almost standard way based on introducing a variable conjugated to perturbation (a dynamic conjugate). The derivation relies solely on the Markovianity of the underlying dynamics, with the only additional assumption that the transition PDF of the process is differentiable with respect to the strength of a constant, time- independent perturbation. The structure of this conjugate variable is however unusual: it is a two-time one, and reduces to a usual single-time conjugate in stationary situations. We show how several known results follow from this approach.
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Materials Science · Cross-listed from physics.chem-ph
Truncated automatic sparse differentiation for machine learning interatomic potentials
Marcel F. Langer, Adrian Hill and Michele Ceriotti
Machine learning interatomic potentials (MLIPs) learn the mapping from atomic positions to potential energy. The forces, the negative gradient of this energy, drive molecular dynamics and are readily obtained using automatic differentiation. Higher-order derivatives, most notably the Hessian, describe collective motion and allow the direct prediction of experimental observables, but are considered computationally inaccessible for large systems. We suggest a solution: in physical systems, interactions decay with distance, and most MLIPs build on this locality through message passing up to a finite receptive field. This implies both sparsity of higher-order derivatives and their decay with distance. This structure can be exploited using automatic sparse differentiation (ASD). We explain how to compute the sparsity pattern for MLIP derivatives and demonstrate that, for multiple foundation MLIPs, ASD computes full Hessians of large porous materials exactly, but with modest speedups at best. The larger gains come from truncated ASD: discarding small, but nonzero, Hessian entries between distant atoms yields order-of-magnitude speedups with negligible impact on predicted observables.
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Soft Condensed Matter · Cross-listed from physics.chem-ph
Collective Ion Dynamics from Finite-Volume Fluctuations in Model Explicit-Solvent Electrolytes
Jeongmin Kim
Understanding how collective ion transport emerges from
equilibrium fluctuations is central to electrolyte statistical mechanics. Finite-volume fluctuations provide an accessible route to this information, but their interpretation is complicated because they mix wave numbers and collective fields. Here, we extend the finite-volume counting framework for inferring collective ion
diffusion by combining the exact window projection with an inertial independent-particle reference, and apply it to a symmetric 1:1 solvent primitive model. The growth of ion-number fluctuations between the ballistic and plateau regimes appears nearly ideal, but this apparent ideality results from compensation between negative structural and positive dynamical excess contributions. The coupled ion-number–solvent relaxation further reveals a signed redistribution between solvent-associated and solvent-orthogonal projections that is largely hidden in the total response. The inferred collective
diffusion depends on observation length and dynamical closure: measured structure alone does not systematically improve the estimate, whereas the coupled-field description reduces the high-concentration discrepancy. These results provide a basis for analyzing more realistic electrolytes with mutually coupled ion-number, charge, and solvent fluctuations.
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Strongly Correlated Electrons
Unconstrained compact lattice QED$_{2+1}$ coupled to phonons: Gauss sectors, orthogonal semimetal, and deconfined criticality
João C. Inácio and Fakher F. Assaad
Gauge theoretic descriptions of 2D
quantum magnets are defined on a restricted physical
Hilbert space by imposing Gauss's law. In this work, we study an unconstrained compact
lattice QED$_{2+1}$ coupled to bond
phonons, in which local Gauss operators are conserved, but their
eigenvalues are not a priori fixed. Using exact auxiliary-field
quantum Monte Carlo simulations at $N_f = 2$, we investigate how the physical Gauss sector becomes energetically favourable, and how this process is connected to confinement and
symmetry breaking. We identify an orthogonal semimetallic (OSM) phase, in which
fermions striped off their gauge charge and form a Dirac
liquid. This phase mixes various Gauss sectors, and becomes unstable when Gauss's law is explicitly enforced. Upon the imposition of Gauss's law, compactness allows for monopole excitations carrying antiferromagnetic (AFM) and valence-bond-solid (VBS)
quantum numbers. Gauge field fluctuations and spinon-
phonon coupling tune between the competition of such monopoles and generate a phase diagram with OSM, AFM and VBS orders. The transitions out of the OSM phase coincide with the dynamical generation of Gauss's law, while the competition between AFM and VBS charged monopoles produces a transition consistent with deconfined
quantum criticality. Thus our results establish that upon the projection to the physical
Hilbert space, deconfinement in compact
lattice QED$_{2+1}$ is always unstable towards either AFM or VBS order.
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Quantum Gases
Unified hydrodynamics for density and spin supersolids
Ashwath N. Madhusudan, Au-Chen Lee, P. B. Blakie et al. (+1 more)
Two-component supersolids can exhibit in-phase or out-of-phase component density modulations, corresponding to density and
spin supersolids, respectively. We formulate a general hydrodynamic theory for the collective dynamics of multicomponent supersolids, guided by their broken
symmetries and conservation laws. We
benchmark it against microscopic calculations for a binary dipolar condensate confined to an infinite tube, finding quantitative agreement for the sound speeds of all three Goldstone branches throughout the density- and
spin-supersolid regions. The resulting relations link collective-mode measurements to elastic coefficients and superfluid fractions.
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All authors Ashwath N. Madhusudan, Au-Chen Lee, P. B. Blakie, R. N. Bisset
Materials Science
Strain-Induced Metal-to-Insulator Transition in Antiferromagnetic SrCrO$_3$ Thin Films
S. Jöhr, A. Carta, J. Moreno et al. (+11 more)
Antiferromagnetic (AF) metals are rare, yet they combine properties attractive for spintronic devices like robustness against stray fields and electrical readout. Among AF metal oxide candidates, SrCrO$_3$ remains largely unexplored due to its notoriously difficult synthesis. In this paper, we demonstrate the growth of high-quality SrCrO$_3$ thin films by magnetron sputtering on substrates that impose a wide range of tensile and compressive strains.
Muon spin relaxation experiments, supported by x-ray
magnetic dichroism, unveil the emergence of an AF phase with dilute
magnetic disorder at low temperatures, while resistivity measurements confirm the simultaneous metallic ground state of SrCrO$_3$ under low strain. As both compressive and tensile strain increase, a metal-to-
insulator transition is induced in the films, while the onset of the
magnetic transition temperature remains unchanged. Moreover, an intriguing resistivity upturn, accompanied by a change in the dominant charge-carrier type, occurs at a temperature that correlates with strain. These observations suggest a complex strain-dependent band structure, with strain-induced Jahn-Teller distortions or tilting of the CrO$_6$ octahedra that emerge depending on the sign of the strain, as inferred from density functional theory calculations.
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All authors S. Jöhr, A. Carta, J. Moreno, A. Suter, Z. Salman, A. Panda, J. Spring, G. De Luca, J. Herrero-Martin, B. Mundet, C. Piamonteze, M. Gabay, C. Ederer, M. Gibert
Materials Science
Tuning the Coercive Field in Ferroelectric Hf0.5Zr0.5O2-Al2O3 Heterostructures via Interfacial Charge Dynamics
Marshall B. Frye, Chanyoung Kim, Jeong-Woo Sun et al. (+8 more)
Interleaving dielectric layers into ferroelectric Hf0.5Zr0.5O2 (HZO) films increases the
memory window (MW) beyond what is accounted for by the dielectric constants. Determining the physical mechanisms behind these MW improvements is critical to reaching the full potential of HZO FeNAND. Here, we show that MW improvements stem from the interfacial charge dynamics enabled by oxygen vacancies at the interlayer interface. X-ray photoelectron spectroscopy(XPS) etching experiments demonstrate increased off-stoichiometry at the interface, with a 2.3x increase in oxygen vacancies. Polarization-dependent XPS and first-order reversal curves(FORC) show that tunneling between interfacial defect states causes a bidirectional internal bias of 0.56MV/cm. The impact of defects is further corroborated through phase-field modeling(PFM), which only recreates the coercive fields, FORC, and internal bias for defect densities and tunneling barrier heights that are consistent with experiment, quantitatively capturing an internal electric field of 0.55 MV/cm. The phase field models are then used to simulate 36 devices with varied charge densities and dielectric thickness to provide a predictive framework for further improvements in the MW of interlayer HZO. These findings redefine the role of defects in ferroelectric HZO from deleterious to engineerable and provide critical insights into how to tune ferroelectric device architectures for improved
memory.
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All authors Marshall B. Frye, Chanyoung Kim, Jeong-Woo Sun, John Wellington-Johnson, Lance Fernandes, Prasanna Venkatesan Ravindran, Bogdan Dryzhakov, TaeYoung Song, Mengkun Tian, Asif I. Khan, Lauren M. Garten
Strongly Correlated Electrons
Collective Charge-\(2e\) Bosonic Excitations in Charge-Ordered Systems
Ping Tang
Charge order is conventionally characterized by a static modulation of the electronic density, while its collective excitations remain less developed from a quasiparticle perspective than those of
spin-ordered systems. Here, we formulate the collective excititations of charge order within an effective charge-pseudospin model, in which the charge-ordered ground state is represented by staggered pseudospin order. Quantizing fluctuations around this ordered state via a Holstein–Primakoff transformation, we reveal two branches of bosonic quasiparticles with degenerate, gapped dispersions that carry opposite quantized electric charges $\pm 2e$. We therefore term these charge-$2e$
bosons “bichargons,” closely paralleling the two
magnon branches of a bipartite antiferromagnet that carry opposite
spin angular momenta. We show that a temperature gradient drives the
diffusion of thermally excited bichargons, generating a charge Seebeck response when the degeneracy between the oppositely charged branches is lifted by tuning the chemical potential away from the charge-neutrality point. In contrast, despite carrying finite electric charges, a thermal bichargon gas remains electrically insulating under a static electric field because bichargon quasiparticle number is not conserved. An ac electric field, however, can parametrically generate coherent pairs of oppositely charged bichargons that support a finite dc drift current in the presence of a bias electric field, offering a bosonic analogue of photoconductivity mediated by photoexcited electron–hole pairs in
semiconductors. Our results establish bichargons as a new class of collective bosonic charge carriers in charge-ordered systems and extend the quasiparticle paradigm of
magnons in
spin-ordered systems to the charge sector, with electric charge replacing
spin angular momentum as the transported quantity.
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Mesoscale and Nanoscale Physics
Disorder-induced modulation of the nonlinear Hall effect in Weyl semimetals
Juan A. Cañas, Daniel A. Bonilla and A. Martín-Ruiz
We study the effects of impurity scattering on the nonlinear Hall response of Weyl semimetals within the semiclassical Boltzmann approach. We derive the rectified and second-harmonic conductivity tensors for a general momentum-dependent transport relaxation time and evaluate this quantity microscopically for short-range, Gaussian, screened Coulomb, and
magnetic impurities. For scalar disorder, the relaxation time is isotropic and chirality independent. The nonlinear Hall response is then determined by the anomalous velocity associated with the Berry
curvature, and a finite net response requires energetically inequivalent Weyl nodes to avoid cancellation between opposite chiralities. Polarized
magnetic impurities lead to a qualitatively different behavior. We find that interference between the first- and second-order Born amplitudes generates a helicity-dependent anisotropic correction to the relaxation time. This anisotropy changes the tensor structure of the nonlinear Hall conductivity and gives rise to a finite second-harmonic current for suitable orientations of the electric field relative to the impurity polarization. For representative parameters, however, the anisotropic contribution is several orders of magnitude smaller than the dominant isotropic response. These results establish how the microscopic form of impurity scattering enters the nonlinear Hall response of Weyl semimetals through the transport relaxation time.
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Statistical Mechanics · Cross-listed from physics.comp-ph
Correlation-Free Transition Path Sampling through Shooting Point Generation Guided by Committor Learning
Maximilian Negedly, Sebastian Falkner, Alessandro Coretti et al. (+1 more)
Studying the dynamical behavior of a system often depends on characterizing how it transitions between long-lived states. Because such transitions are rare, observing them usually requires specialized enhanced sampling techniques. Transition Path Sampling (TPS) is a well-established method for generating reactive trajectories, which is simple to implement and does not require the definition of a preconceived reaction coordinate. However, its efficiency is limited by its sequential nature and the resulting correlations between sampled paths. Previous work addressed this limitation by combining TPS with a sampling scheme based on conditioned Boltzmann Generators, a generative machine learning model capable of sampling a given target probability distribution. This approach produces uncorrelated transition paths but relies on an accurate reaction coordinate, which is rarely known in advance. Building on recent advances in committor learning, specifically on the Artificial Intelligence for Molecular Mechanism Discovery (AIMMD) method, in this work we introduce GenAIMMD, an iterative
algorithm that actively and self-consistently learns the ideal reaction coordinate (the committor) and trains a conditioned Boltzmann Generator to sample from arbitrary bias windows along it. GenAIMMD thereby provides a correlation-free and fully parallelizable path sampling scheme that does not require prior knowledge of the system's transition mechanism. We apply GenAIMMD to a two-dimensional toy model and a higher-dimensional
polymer system. In both cases, GenAIMMD succeeds in training the Boltzmann Generator and learning the committor.
Benchmark results show a substantial increase in performance compared to standard TPS.
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All authors Maximilian Negedly, Sebastian Falkner, Alessandro Coretti, Christoph Dellago
Strongly Correlated Electrons
Non-Thermal Effects in Fermionic Atoms Coupled to Open Cavities
Jules Sueiro and Marco Schiro
We study a Fermi-Hubbard model coupled to a open dissipative single cavity mode. Using Keldysh diagrammatics we derive and solve the
quantum kinetic equations for the
fermions, taking the bosonic cavity mode as a source of non-
equilibrium noise and dissipation. In absence of Hubbard interactions we show that the
fermions reach generically a non-
equilibrium steady-state, characterized by a non-thermal distribution function. Quite interestingly we demonstrate that the latter exactly nullifies the heat-current between
fermions and cavity mode. We discuss the regimes of parameters where a low-frequency effective temperature description emerges and how the fluctuations affect the mean-field phase diagram for the superradiance phase transition. Finally we include Hubbard interaction in the weak-coupling regime and show that it leads to a crossover towards a full
equilibrium distribution.
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Statistical Mechanics
Khinchin's ergodicity and typicality in statistical mechanics
Dario Lucente, Marco Baldovin, Giacomo Gradenigo et al. (+1 more)
The formulation of statistical mechanics in terms of ensembles, originally proposed by Gibbs, has proved to be extremely effective in describing the
equilibrium state of many-particle systems, in the most diverse contexts (critical phenomena,
quantum mechanics, biophysics, just to mention a few). The reasons of this success are still debated, and the connection between dynamics and probability in large systems remains somehow elusive. Indeed, in order to derive the main results of
equilibrium statistical mechanics, strong assumptions on the ergodicity of the dynamics are usually required. Nonetheless, empirical observations seem to suggest that the predictions of the theory hold true even when such assumptions are not verified. In this paper we reconsider the point of view put forward by Khinchin, stating that the only relevant ingredients for the validity of statistical mechanics are the large number of degrees of freedom in the system and the choice of extensive observables, irrespectively of the details of the microscopic dynamics. In particular, the presence of dynamical chaos is not required. To this aim, we discuss some analytical and numerical results on a couple of classical integrable systems, the harmonic chain and the Toda model, showing that many important features predicted by
equilibrium statistical mechanics, as for instance Maxwell-Boltzmann distribution, are found even in absence of chaos.
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All authors Dario Lucente, Marco Baldovin, Giacomo Gradenigo, Angelo Vulpiani
Strongly Correlated Electrons
Emergent Surface Kondo Flat Band Driven by Competing Interactions in a Topological Ferromagnet
Nazar Zaremba, Susmita Changdar, Haojie Guo et al. (+28 more)
A central goal of modern condensed matter physics is to uncover new
quantum states of matter arising from the intertwined effects of strong electron correlations, magnetism, and band
topology. Heavy-
fermion phases, generated by Kondo interactions, represent one of the most remarkable manifestations of electronic correlations, and topological heavy-
fermion states have been identified in several non-
magnetic materials. Yet, the consequences of their competition with
magnetic order have remained largely unexplored. Here, we reveal a new phenomenon: the spontaneous spatial separation of correlated
quantum phases. By showing that magnetism can drive distinct strongly correlated electronic states to coexist in different regions of a single material, our work establishes a previously unknown mechanism for organizing
quantum matter and opens a new direction in the study of correlated topological systems. Using bulk-sensitive probes, we show that UAsS
crystals are, in the bulk, metallic ferromagnets with only moderate correlation-driven band renormalizations. First-principles calculations reveal a topological electronic structure hosting both nodal lines and Weyl points, pointing to a rich underlying
topology. Angle-resolved photoemission spectroscopy (ARPES) measurements are consistent with these predictions, resolving the nodal lines and Weyl crossings. In striking contrast, surface-sensitive ARPES and scanning tunneling microscopy/spectroscopy (STM/STS) measurements reveal a pronounced flat band pinned at the Fermi level, accompanied by a sharp resonance – hallmarks of an emergent, strongly correlated Kondo state not captured by first-principles calculations.
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All authors Nazar Zaremba, Susmita Changdar, Haojie Guo, Iñigo Robredo, Daniel Lozano-Gomez, Andreas Leithe-Jasper, Rui Lou, Yurii Prots, Mitja Krnel, Markus König, Konstantin Semeniuk, Berit H. Goodge, Yuri Grin, Andrii Kuibarov, Oleksandr Suvorov, Alexander Fedorov, Adam Pikul, Ivan Soldatov, Rudolf Schäfer, Bernd Büchner, Oksana Kvitnitskaya, Yurii Naidyuk, Louis Lamm, Meike Pfeiffer, Elena Hassinger, Matthias Vojta, Sergey Borisenko, Miguel M. Ugeda, Jeroen van den Brink, Eteri Svanidze, Maia G. Vergniory
Quantum Gases · Cross-listed from quant-ph
State-Selective Floquet Memory in Degenerate Manifolds
Ayan Sahoo, Argha Debnath and Debraj Rakshit
In order to understand which initial states retain
memory under periodic driving, it is necessary to depart from the ideal limit giving rise to invariant structures and work inside near-degenerate
manifolds. We show that degeneracy itself is not conclusive and what actually matters is how perturbations, such as structural and driving imperfections, acts on the projected multiplet. For systems decoupling into the local clusters in the ideal limit, the projections can be computed within degenerate perturbation theory. There the stability is decided by two criteria: the coupling can not connect the state with other degenerate partners in the
manifold, either by kinetic blocking, or more generally, by diagonalizing the projected coupling, and the drive's local selection rule must admit only transfer energies detuned from Floquet sidebands, in which case the projected drive generator exactly vanishes. We formalize these understandings in a periodically driven clean, short-ranged alternating XXZ chain and demonstrate a set of results that include, long-lived states, both of product form and entangled across the clusters, a periodic family of sideband resonances, and an explicit example showing opposite fates for states with identical energy and charges.
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Mesoscale and Nanoscale Physics
Coplanar Lateral Gating MoS2 on SrTiO3: A Unified Platform for Classical and Quantum Devices
Prasad Muragesh, Manav Murali, Venkatesha Modur Ramachandra et al. (+1 more)
Atomically thin transition-metal dichalcogenides, such as MoS2, offer a promising route to surpass the scaling limits of silicon owing to their excellent electrostatic control and resilience to short-channel effects. Realizing this potential depends critically on gate-stack engineering, where strong gate coupling must be achieved without compromising the pristine two-dimensional interface. Here, we demonstrate a coplanar lateral-gating architecture for MoS2 field-effect transistors fabricated directly on single-
crystal SrTiO3. The exceptionally high permittivity of SrTiO3 enhances gate-channel coupling. The coplanar geometry eliminates the need for a separate gate
insulator, reducing interface disorder. Owing to the
quantum paraelectric nature, the SrTiO3 dielectric constant increases upon cooling, enhancing the gate coupling, leading to a decrease in threshold voltage and subthreshold swing an effect that contrasts with conventional FET architectures. The dielectric-free MoS2 surface, combined with enhanced electrostatic control, makes this architecture a promising platform for low-power two-dimensional electronics and cryogenic
quantum devices.
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All authors Prasad Muragesh, Manav Murali, Venkatesha Modur Ramachandra, Madhu Thalakulam
Statistical Mechanics
Universal 1/f Noise in the Power Spectra of Energy Time-series in Solvated DNA Dynamics
Harsh Sahu, Deepika Sardana, Pramod Kumar et al. (+3 more)
We investigate energy fluctuations of solvated DNA in three conformations: G-quadruplex, Hairpin, and Duplex. Our comprehensive molecular dynamics (MD) simulations demonstrate that the time-series of interaction energies for DNA self, DNA-water and DNA-ion show 1/f noise with a universal decay exponent $\beta \simeq 0.90$. We show that DNA
topology and structural rigidity modulate its dynamic coupling with the surrounding hydration shell and mobile counter-ions. This coupling critically shapes the 1/f noise profile: DNA self energies in flexible structures (G-quadruplex, Hairpin) display pronounced low-frequency modes absent in the rigid Duplex. These findings reveal how the interplay between DNA
topology and environmental coupling governs different
stochastic behavior in biologically relevant forms of DNA.
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All authors Harsh Sahu, Deepika Sardana, Pramod Kumar, Ajay Kumar Chand, Sobhan Sen, Sanjay Puri
Materials Science
Ultralow-Tensile Strain Enables Exciton Funneling and Energy Transfer to Boost MoSe2 Photoluminescence Quantum Yield
Gayatri, Mehdi Arfaoui, Debashish Das et al. (+14 more)
Strain engineering is a powerful route for controlling the
exciton dynamics in van der Waals (vdW)
heterostructures (HSs). The interlayer energy transfer (ET) process is another key factor in controlling the photocarrier relaxation pathways in vdW HSs. In this work, we combine these two processes to achieve an 8-fold enhancement to the relative photoluminescence (PL)
quantum yield (QY) in a HS formed from monolayers of ReS2 and MoSe2, separated by a thin hBN interlayer, placed onto an hBN bubble. We achieve this enhancement by applying only 0.1% biaxial tensile strain, which results in efficient
exciton funneling and an increased transition dipole moment. Our experimental data are supported by first-principles density-functional theory and coherent transfer-
matrix method calculations, ruling out optical interference as the dominant origin of the enhancement. This work provides an innovative route for enhancing the PL QY of vdW materials via interplay between the tensile strain and the ET process.
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All authors Gayatri, Mehdi Arfaoui, Debashish Das, Mateusz Raczyński, Marta Bilska, Piotr Tatarczak, Aleksandra Krystyna Dąbrowska, Tomasz Kazimierczuk, Takashi Taniguchi, Kenji Watanabe, Piotr Kossacki, Andrzej Wysmołek, Saroj Kumar Nayak, Adam Babiński, Johannes Binder, Maciej R. Molas, Arka Karmakar
Mesoscale and Nanoscale Physics
Predictive Structure to Thermal Conductivity Modeling Framework for BEOL Interconnect Stacks in Advanced Technology Nodes Enabled by Extensive Layer Resolved Thermal Measurements
Zifeng Huang, Yiyang Sun, Tianyu Jia et al. (+2 more)
The increasing structural complexity of BEOL interconnect stacks in advanced integrated
circuits demands a structure-aware thermal conductivity (ąppa}) modeling framework. However, generalizable models derived from layer-resolved thermal measurements that quantitatively capture the dependence of ąppa} on interconnect structures remain lacking, limiting predictive thermal analysis. Here, we establish an experimentally derived, structure-aware ąppa} modeling framework enabled by time-domain thermoreflectance measurements with ~100 nm depth resolution. Statistical analysis of a compiled
dataset comprising over 40 experimentally measured layer-resolved ąppa} values across diverse BEOL layers reveals a generalizable empirical structure-to-ąppa} relationship, enabling predictive modeling based on interconnect structure. An intra-layer three-dimensional ąppa} distribution model based on effective medium theory and realistic layouts further resolves spatial ąppa} variations within practical interconnect layers. Together, these models establish an experimentally derived, structure-aware ąppa} modeling framework for predictive and generalizable thermal analysis of advanced interconnect stacks and 3D ICs.
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All authors Zifeng Huang, Yiyang Sun, Tianyu Jia, Runsheng Wang, Zhe Cheng
Strongly Correlated Electrons
Pressure-induced electronic and structural evolution of EuIrGe3
N.S.Dhami, V. Baledent, I. Batistic et al. (+10 more)
We investigated the pressure-induced
evolution of the electronic and
crystal structure of the noncentrosymmetric BaNiSn3-type antiferromagnet EuIrGe3 using x-ray absorption spectroscopy, synchrotron x-ray diffraction complemented by density functional theory calculations, and electrical resistivity measurements. The Eu L3-edge spectra reveal a continuous increase in the mean Eu valence under compression, accompanied by modifications of the Ge and Ir electronic states. High- pressure x-ray diffraction shows anisotropic
lattice compression in the tetragonal (I4mm) phase and provides evidence for a structural phase transition above 38 GPa. The experimentally deter- mined
lattice and equation-of-state parameters are in good agreement with the DFT calculations. Electrical resistivity measurements reveal a monotonic increase in the antiferromagnetic ordering temperatures up to 18 GPa, indicating that the antiferromagnetic ground state remains robust despite the increasing contribution of the nonmagnetic Eu3+ configuration to the intermediate va- lence state. These results demonstrate that EuIrGe3 exhibits a pressure response distinct from EuCoGe3 and EuRhGe3, highlighting the important role of the transition metal d-electron states in the pressure-induced electronic and structural
evolution of the EuT Ge3 family
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All authors N.S.Dhami, V. Baledent, I. Batistic, C. M. N. Kumar, D. Kaczorowski, L. Nataf, J. M. Ablett, J.-P. Rueff, J. P. Itie, P. Fertey, S. R. Shieh, P. Popcevic, Y. Utsumi Boucher
Materials Science
A Computational Method to Simulate Electrostatic Actuation in Polycatenated Architected Materials
Mateus Maciel Vivaldi and Alexandre F. Fonseca
A novel class of polycatenated architected materials (PAMs) has recently emerged, exhibiting distinctive mechanical properties such as stress-strain hysteresis and a geometry-driven transition between solid-like and fluid-like behavior. Although finite element models exist for conventional PAMs, none currently account for electrostatic effects. Here, we propose and qualitatively validate a computational framework to simulate the structure, dynamics, and mechanical response of electrostatically charged PAMs. Our approach successfully reproduces electrostatic actuation in close agreement with experiments, and reveals that electrostatic charges enable a reversible fluid-to-solid transition while also providing a means to estimate electrostatic stiffness. Notably, stiffness enhancements of up to sevenfold are achieved upon charging. This work expands the design space of PAMs and offers a predictive tool for actively controllable mechanical metamaterials.
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Soft Condensed Matter
Inferring interactions between active particles using harmonic traps
Arnaud Compagnie, Joscha Mecke, Ivo Buttinoni et al. (+1 more)
Quantifying the interactions between active Janus particles remains a challenge that needs to be addressed to describe their collective behaviour. Inspired by a photonic force microscopy setup where two active Janus particles are confined in separate optical tweezers, we derive the steady-state probability distribution of each particle bearing signatures of the pair phoretic interaction, which can be generalised to a broader range of interactions. This approach allows us to infer interaction forces and torques from positional configurations without any knowledge of the particle orientations. Unraveling the distance-dependent interaction between active particles is essential to harnessing them as building blocks for advanced materials with dynamic properties.
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All authors Arnaud Compagnie, Joscha Mecke, Ivo Buttinoni, Hartmut Löwen
Superconductivity
Superconductivity in Pb2-xBixPd Single Crystals
S. Srivastava and R. P. Singh
Chemical substitution provides an effective route to tune the structural and superconducting properties and to explore the
evolution of superconductivity across related materials. In this work, we investigate the effect of Pb/Bi mixing on superconductivity in possible topological
superconductors \ch{Pb2Pd} and $\beta$-\ch{Bi2Pd}, by synthesizing and characterizing single
crystals of \ch{Pb_{2-x}Bi_{x}Pd} ($0.2\le x\le1.8$). Increasing Bi content triggers a structural phase transition from non-symmorphic ($I4/mcm$, $x<1$) to layered ($I4/mmm$, $x\ge1$) and induces a monotonic expansion of the
lattice parameters. Across the doped range, all superconducting samples behave as weakly-coupled type-II
superconductors exhibiting isotropic s-wave superconducting gaps.
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