Statistical Mechanics · Cross-listed from q-bio.PE
Fluctuating environments are sufficient to drive substantial variability in species abundance across locations
James F. D. Henderson and Andreas Tiffeau-Mayer
Species growing in environments that change in time and space will vary in their abundance across locations, even in the absence of persistent location preferences. Here we quantify this non-
equilibrium effect by studying a minimal model of a spatially compartmentalised community with time-averaged-neutral competition but location-dependent environmental fluctuations. We analytically derive distributions of two-point inequality, defined as the log-ratio of a species' abundance across a pair of locations. We characterise how the balance of relaxation via migration and fluctuation strength determine the bulk and extreme value statistics of these distributions in the two-patch and infinite-patch cases. We demonstrate the existence of a noise-induced transition to bimodal inequality, which depends on the correlation timescale of the environmental fluctuations. Finally, we discuss the evolutionary benefit of finite migration rates in environments with temporal correlations.
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Mesoscale and Nanoscale Physics
Graphene-capped bismuthene on SiC as a platform for correlated quantum spin Hall edge states
Huu Thoai Ngo, Zamin Mamiyev, Niclas Tilgner et al. (+4 more)
Epitaxial bismuthene on SiC(0001) hosts
symmetry-protected metallic edge states within a large bulk band gap, establishing it as a promising two-dimensional topological
insulator for hightemperature
quantum spin Hall (QSH) transport. Here we realize bismuthene islands by intercalating Bi beneath zero-layer
graphene on SiC(0001) followed by hydrogen treatment, yielding well-defined edges with controlled terminations. Spectroscopic measurements demonstrate that the edge states reside inside the bulk band gap and remain charge neutral. The
graphene overlayer interacts only weakly with the bismuthene, preserving its topological character while providing environmental protection. Notably, the one-dimensional edge channels exhibit signatures of enhanced electronic correlations relative to freestanding bismuthene, suggesting proximity-induced modification of the QSH edge physics. These results establish
graphene-capped bismuthene as a robust and tunable platform for correlated
quantum spin Hall states.
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All authors Huu Thoai Ngo, Zamin Mamiyev, Niclas Tilgner, Andres David Pena Unigarro, Sibylle Gemming, Thomas Seyller, Christoph Tegenkamp
Quantum Gases
Kosterlitz-Thouless transition in uniformly confined $^4$He
Filip Novotný, Marek Talíř, Balázs Szalai et al. (+1 more)
This study investigates the Kosterlitz-Thouless (KT) transition in superfluid $^4$He confined within uniform nanochannels. While the universal jump in superfluid density is a well-established phenomenon, predicting the absolute transition temperature ($T_{KT}$) based on film geometry has remained a long-standing challenge, often relying on empirical fits. Using on-chip nanofluidic Helmholtz resonators with channel heights of 10, 15, and 20 nm, we probe the transition using 4th sound resonant modes.We demonstrate that the observed shift in the transition temperature relative to the bulk lambda point ($T_{\lambda}$) is accurately accounted for by including two-dimensional thermal excitations, specifically 2D rotons. By incorporating these roton-like excitations into the static KT theory, we can predict absolute transition temperatures that align with our experimental measurements and historical data without invoking traditional coherence length scaling arguments. Furthermore, we show that the dynamical extension of the KT theory (AHNS) fully describes the dissipation peaks observed near the transition without requiring ad-hoc free
vortex contributions. These results provide compelling evidence that roton excitations, rather than correlation length scaling, govern the finite-size behaviour of confined superfluid $^4$He
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All authors Filip Novotný, Marek Talíř, Balázs Szalai, Emil Varga
Statistical Mechanics
Universality classes, Thermodynamics of Group Entropies, and Black Holes
Henrik Jeldtoft Jensen, Petr Jizba and Piergiulio Tempesta
Conventional Boltzmann–Gibbs statistical mechanics successfully describes systems with weak to moderate correlations, in which the number of accessible configurations $W(N)$ grows exponentially with the number of degrees of freedom $N$. However, this framework breaks down for systems for which the effectively occupied configuration space exhibits non-exponential growth. While numerous generalized
entropies have been proposed to address this limitation, a coherent link to classical thermodynamic laws has remained elusive. Here, we propose group
entropies as a unifying framework, defining universality classes of
entropies through the asymptotic scaling of $W(N)$, each yielding an extensive
entropy. We show that this approach provides the basis for a consistent thermodynamic formulation beyond the Boltzmann–Gibbs paradigm. In particular, by expressing these
entropies in terms of thermodynamic state variables, we demonstrate their consistency with classical thermodynamics, in close analogy to the emergence of the Clausius
entropy from the Boltzmann–Gibbs formalism. Focusing on the zeroth thermodynamic law, we identify the empirical temperature and, by using Carathéodory's formulation of the second law, we derive the associated absolute temperature. As an application, we analyse black-hole thermodynamics using the extensive group
entropy class corresponding to stretched-exponential behaviour of $W(N)$ and derive a negative heat capacity, known to be a hallmark property of black holes. This result holds for the stretched-exponential
entropies associated with both the Bekenstein–Hawking and Barrow
entropy scalings.
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Statistical Mechanics · Cross-listed from hep-th
Analysis of Quartic Potential Problems Using Fredholm Integral Operators with Airy Functions
Ori J. Ganor
Fredholm integral operators that commute with the
Hamiltonians of certain
quantum mechanical systems with quartic potentials are introduced in closed analytical form. The operators are expressed in terms of the Airy function, and their
eigenvalues fall off exponentially. Using these operators we obtain an exact dual description in terms of infinite one-dimensional chains. The systems discussed include the anharmonic quartic oscillator as well as multivariable potentials and higher dimensional systems. We compute a few moments of the Fredholm operators, using
matrix models in the higher dimensional case, and we show how those can be used to approximate the energy spectrum and obtain estimates of the asymptotic behavior of the wavefunctions.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Electric Field Resolved Image Formation in a Widefield Optical Microscope
Arjun Ashoka, Juhwan Lim, Akshay Rao et al. (+1 more)
Visualizing the spatiotemporal
evolution of the electric field of light is fundamental to optics, from designing photonic devices to developing next-generation microscopes. However, we lack the experimental tools to directly access the electric field of light in the sample plane of an optical microscope. Here, we introduce an all-optical imaging modality that resolves the electric field of light in the plane of a traditional widefield transmission optical microscope with 100-attosecond temporal and 200-nanometer spatial resolution. With this we demonstrate the delayed buildup of scattering contrast and pulse broadening through and around a thick MoTe2 flake - dynamics inaccessible via standard simulations. We showcase our technique's versatility by additionally resolving the full in-plane vector electric field lines during photoexcitation as the optical pulse propagates through and around the MoTe2 flake.
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All authors Arjun Ashoka, Juhwan Lim, Akshay Rao, Dmitry A. Zimin
Quantum Gases · Cross-listed from physics.atom-ph
Characterization of Feshbach resonances in $^6\mathrm{Li}{-}^7\mathrm{Li}$ using improved interaction potentials
Jing-Chen Zhang, Paul Julienne and Yu Liu
We characterize Feshbach resonances in all isotopologues of the $\mathrm{Li}{-}\mathrm{Li}$ system with improved interaction potentials. Starting from spectroscopically accurate Morse/long-range (MLR) potential-energy curves for the singlet ($X^{1}\Sigma^{+}$) and triplet ($a^{3}\Sigma^{+}$) electronic states of $\mathrm{Li}_2$, we apply small phenomenological inner-wall adjustments (following Julienne and Hutson, Phys. Rev. A 89, 052715 (2014), arXiv:1404.2623v3) and fit the resulting potentials to threshold measurements for the $^{6}\mathrm{Li}{-}^{6}\mathrm{Li}$ and $^{7}\mathrm{Li}{-}^{7}\mathrm{Li}$ isotopologues, including binding energies, scattering lengths, and Feshbach resonance positions. Using the optimized potentials in coupled-channels scattering calculations, we predict and characterize s-wave Feshbach resonances in the $^{6}\mathrm{Li}{-}^{7}\mathrm{Li}$ isotopologue. In its lowest-energy hyperfine channel, all resonances are narrow ($\sim 0.01{-}0.1$ G), strongly closed-channel dominated, and predominantly triplet in electronic
spin character, in marked contrast to the homonuclear systems. These results provide a foundation for designing Raman optical-transfer pathways to produce ultracold $\mathrm{Li}_2$ molecules in deeply bound rovibrational levels of both the $X^1\Sigma^{+}$ and $a^3\Sigma^{+}$ potentials across all three isotopologues.
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Strongly Correlated Electrons
Large Electron Model: A Universal Ground State Predictor
Timothy Zaklama, Max Geier and Liang Fu
We introduce Large Electron Model, a single neural network model that produces variational wavefunctions of interacting electrons over the entire
Hamiltonian parameter
manifold. Our model employs the
Fermi Sets architecture, a universal representation of many-body fermionic wavefunctions, which is further conditioned on
Hamiltonian parameter and particle number. For interacting electrons in a two-dimensional harmonic potential, a single trained model accurately predicts the ground state wavefunction while generalizing across unseen coupling strengths and particle-number sectors, producing both accurate real-space charge densities and ground state energies, even up to $50$ particles. Our results establish a foundation model method for material discovery that is grounded in the variational principle, while accurately treating strong electron correlation beyond the capacity of density functional theory.
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Materials Science
Orbital to charge current conversion in copper oxide heterostructures
S. Vojkovic, K. Cancino, G. Rodríguez et al. (+8 more)
We investigate the orbital-to-charge current conversion in CoFeB|CuO
bilayers as a function of CuO thickness, employing orbital pumping via
ferromagnetic resonance. The dynamic injection of orbital angular momentum into the CuO layer generates a transverse voltage through the Inverse Orbital
Hall Effect (IOHE). By systematically varying the CuO thickness from 2 nm to 30 nm, we observe a pronounced dependence of the IOHE-induced voltage on the CuO layer thickness, indicating efficient orbital-to-charge conversion. These results highlight the key role of the orbital degree of freedom in orbitronics and provide insights into the potential of transition-metal
oxides for next-generation orbitronic devices.
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All authors S. Vojkovic, K. Cancino, G. Rodríguez, E. Burgos, G. Herrera, C. Gonzalez-Fuentes, J. Palma, T. V. M. Sreekanth, J. Denardin, R. L. Rodríguez-Suárez, S. Oyarzún
Statistical Mechanics
Enhancing entanglement asymmetry in fragmented quantum systems
Lorenzo Gotta, Filiberto Ares and Sara Murciano
Entanglement asymmetry provides a quantitative measure of
symmetry breaking in many-body
quantum states. Focusing on inhomogeneous $U(1)$ charges, such as dipole and multipole moments, we show that the typical asymmetry is bounded by a universal fraction of its maximal value. Multipole charges naturally arise in systems with
Hilbert-space fragmentation, where the dynamics splits into exponentially many disconnected sectors. Using the commutant
algebra formalism, we generalize
entanglement asymmetry to account for fragmentation. While the asymmetry grows logarithmically for conventional
symmetries, it can scale extensively in fragmented systems and distinguish classical from
quantum fragmentation. We derive general upper bounds for the asymmetry and identify states that saturate them. To study the typical behavior of the asymmetry, we consider the ensemble of random
matrix product states. By identifying the bond dimension with an effective time parameter, we qualitatively reproduce recent results on asymmetry dynamics in random
quantum circuits, suggesting a universal behavior for the asymmetry of $U(1)$ charges in local ergodic systems.
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Statistical Mechanics · Cross-listed from quant-ph
Local decoder for the toric code via signal exchange
Louis Paletta
Local decoders provide a promising approach to real-time
quantum error-correction by replacing centralized classical decoding, with significant hardware constraints, by a fully distributed architecture based on a simple, local update rule. We propose a new local decoder for Kitaev's toric code: the 2D signal-rule, that interprets odd parity stabilizer measurements as defects, attracted to each other via the exchange of binary signals. We present numerical evidence of exponential suppression of the logical error rate with system size below a threshold, under a phenomenological noise model with data and measurement errors at each iteration. The construction achieves a significantly improved threshold and optimal finite-size scaling relative to hierarchical schemes. It also provides a lightweight alternative to windowed local decoder constructions while maintaining strong performance, thus enabling a streamlined architecture for a two-dimensional local
quantum memory.
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Statistical Mechanics
Strong Zero Modes via Commutant Algebras
Sanjay Moudgalya and Olexei I. Motrunich
Strong Zero Modes (SZMs) are (approximately) conserved quantities that result in (approximate) double degeneracies in the entire spectra of certain
Hamiltonians, with the Majorana zero mode of the transverse-field Ising chain being a primary example. In this work, we discover via a systematic search that many examples of SZMs can be understood as
symmetries in the commutant
algebra framework, which reveals novel algebraic structures hidden in
Hamiltonians with well-known SZMs, including the transverse-field Ising chain. Our findings unify the understanding of different examples of SZMs in the literature, demystify their connections to ground state phases of matter, and reveal novel
symmetries in simple models, such as exact quasilocal $U(1)$
symmetries that sometimes accompany the SZMs such as in the
spin-1/2 XY model for certain parameter values. Moreover, while analytically tractable SZMs have mostly been demonstrated only for non-interacting or integrable models, the algebraic structures revealed in this work can be exploited to construct integrability-breaking interactions that exactly preserve these SZMs. Such non-integrable models are expected to show more clear dynamical signatures of SZMs without the interference of other conserved quantities that appear in integrable models, and we discuss many examples, including those of novel hydrodynamic modes associated with such
symmetries for some special parameter values. We also show that while this commutant understanding extends to the non-interacting limit of the celebrated Fendley SZM in the
spin-1/2 XYZ chain, the SZM in the interacting case cannot be understood in this framework. This suggests that there are two types of SZMs – those that survive integrability breaking and those that do not. We close by using this commutant understanding to construct an alternate proof of the Fendley SZM, which might be of independent interest.
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Strongly Correlated Electrons
Trion liquid and its photoemission signatures
Noam Ophir and Anna Keselman
We study the formation of a trion
liquid in doped low-dimensional
semiconductors with strong electron-hole interactions and analyze its signatures in angle-resolved photoemission spectroscopy (ARPES). We show that this strongly correlated state of matter forms naturally in the vicinity of the phase boundary between a normal band
insulator and an excitonic
insulator upon doping. By studying the photoemission spectrum, we show that a partially occupied trion band gives rise to an in-gap feature in the ARPES spectrum with vanishing spectral weight at the
Fermi energy. We demonstrate our findings using a 1D microscopic model employing exact, unbiased,
matrix product state (MPS)-based calculations.
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Strongly Correlated Electrons
Transformer Neural-Network Quantum States for lattice models of spins and fermions: Application to the Ancilla Layer Model
Riccardo Rende, Alexander Nikolaenko, Luciano Loris Viteritti et al. (+2 more)
We introduce a variational wave function based on Neural-Network
Quantum States (NQS) to study
lattice systems whose local
Hilbert space contains both
spin and fermionic degrees of freedom. Our approach is based on the use of the
Transformer architecture, which can naturally handle composite local
Hilbert spaces through a tokenization procedure closely inspired by techniques from natural
language processing. The neural network predicts a set of fermionic orbitals that depend on the
spin configuration in a backflow-inspired manner. We apply the method to the one-dimensional Ancilla Layer Model, consisting of a chain of mobile
spin-$1/2$
fermions coupled to a two-leg
spin-$1/2$ ladder. For open boundary conditions, we achieve excellent quantitative agreement with Density
Matrix Renormalization Group (DMRG) results across the full range of parameters considered. We find a phase in which the chain forms an effectively decoupled Luttinger
liquid (LL), and a LL* phase with a distinct
Fermi wavevector in which the mobile
fermions are Kondo screened by one leg of the ladder, while the other leg forms the critical Bethe
spin liquid. The LL* is the analog of the phase describing the pseudogap in two dimensions. We also find a Luther-Emery (LE) phase, where the LL* state becomes unstable toward the formation of a
spin gap. The
Transformer Ansatz maintains comparable accuracy for periodic boundary conditions, where tensor-network methods are computationally more demanding. Together, these findings establish
Transformer-based NQS as an accurate and scalable variational framework for correlated
lattice systems with composite local
Hilbert spaces and highlight their potential for studying higher-dimensional models where boundary effects and heterogeneous local structures pose significant challenges.
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All authors Riccardo Rende, Alexander Nikolaenko, Luciano Loris Viteritti, Subir Sachdev, Ya-Hui Zhang
Statistical Mechanics
Low-temperature transition of 2d random-bond Ising model and quantum infinite randomness
Akshat Pandey, Aditya Mahadevan, A. Alan Middleton et al. (+1 more)
At low temperatures, the classical two-dimensional random bond Ising model undergoes a frustration-driven ferromagnet-to-paramagnet transition controlled by a zero-temperature fixed point separating ferromagnet and
spin glass phases. We show that this critical point can be understood through a renormalization group transformation that constructs the ground state of the Ising model through a sequence of
Hamiltonians that, starting with an unfrustrated model, iteratively adds in frustration until the target
Hamiltonian is reached. Via a mapping of the thermodynamics of the 2d Ising model to the spectral properties of a related Hermitian
matrix – the
Hamiltonian of a noninteracting
quantum problem – this RG procedure corresponds to an iterative diagonalization of the
quantum Hamiltonian. The flow toward zero temperature in the Ising picture manifests as a flow toward infinite randomness in the spectrum of the
quantum Hamiltonian, with the log gap of the
Hamiltonian scaling as a power of the system size: $\log \varepsilon_{\it min}^{-1} \sim L^\psi$. The tunneling exponent $\psi$ is equal to the
spin stiffness exponent $\theta_c$ characterizing the zero-temperature fixed point.
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All authors Akshat Pandey, Aditya Mahadevan, A. Alan Middleton, Daniel S. Fisher
Mesoscale and Nanoscale Physics
Jan Kunc, Bohdan Morzhuk, Veronika Stará et al. (+6 more)
The realization of high-fidelity organic-inorganic
quantum emulators is frequently hindered by the interfacial imperfections introduced during device fabrication. Here, we demonstrate a robust nanofabrication protocol that restores the atomic-scale purity of epitaxial
graphene on SiC to UHV-equivalent levels, as confirmed by Low-Energy Electron Diffraction, and Microscopy. This pristine interface enables the emergence of macroscopic excitonic coherence in epitaxial overlayers of 2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), a model molecular system characterized by intense electron-
phonon coupling. Through a combination of high-sensitivity
Fourier Transform Photo-current Spectroscopy, photoluminescence, and dynamic Raman mapping, we resolve a complex vibronic
manifold governed by Davydov splitting. We show that the $P6_3/m$ crystalline
symmetry of the HMTP overlayer lifts the degeneracy of the HOMO-LUMO transition, creating discrete bright and dark excitonic branches. Using an analytical tight-binding model parameterized by ARPES-derived intermolecular coupling and Raman vibrational modes validated by molecular dynamics simulations, we quantify the polarization energy, the Huang-Rhys factor, and Herzberg-Teller corrections to the Franck-Condon model. Our results reveal that the dark-state branch dominates the radiative channel, following a polaron-mediated relaxation pathway consistent with Kasha's rule. By reconciling macroscopic device architecture with UHV-level surface science, this work establishes a scalable platform for the study of dark-
exciton dynamics and the development of solid-state molecular
quantum memories.
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All authors Jan Kunc, Bohdan Morzhuk, Veronika Stará, Devanshu Varshney, Mykhailo Shestopalov, Kryštof Matějka, Martin Rejhon, Jiří Novák, Jan Čechal
Materials Science
Unraveling Lithium Dynamics in Solid Electrolyte Interphase: From Graph Contrastive Learning to Transport Pathways
Qiye Guan and Yongqing Cai
Fast lithium transport across the solid-state electrolyte (SSE)/lithium metal anode interface is critical for high-performance all-solid-state batteries. Uncovering the complex lithium dynamics governed by diverse local environments in the solid electrolyte interphase (SEI) is fundamental for performance optimization. However, a general framework for characterizing these distinct local environments and the associated transport mechanisms remains lacking. Here, we develop GET-SEI, a general framework that discovers local atomic environments without predefined labels through Graph contrastive learning (GCL), models lithium transition kinetics via Extended dynamic mode decomposition (EDMD), and quantifies reactive lithium flux through Transition path theory (TPT). Applied to different SSE/Li systems, including sulfides (Li6PS5Cl/Li, Li10GeP2S12/Li) and
oxides (Li7La3Zr2O12/Li), the GET-SEI reveals dominant transport pathways and kinetic bottlenecks in each system, providing quantitative metrics for evaluating lithium transport efficiency. As novel high-performance SSEs continue to emerge, GET-SEI offers a widely applicable, interpretable tool for targeted SEI engineering.
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Other Condensed Matter · Cross-listed from quant-ph
Single-photon emitters and spin-photon interfaces in silicon
Kilian Sandholzer, Ian Berkman, Peter Deák et al. (+5 more)
Single
photons enable the distribution of
quantum information over large distances and thus play a major role in
quantum technologies such as communication and computing. Solid-state emitters are practical and efficient sources of single
photons that can be manufactured in large numbers. When combined with a
spin, the resulting
spin-
photon interfaces can store
quantum states for extended periods and serve as the basis for
quantum networks and repeaters. Among the many host materials explored over the past few decades, silicon stands out for its advanced nanofabrication, the maturity of its integrated photonics and microelectronics, and its high isotopic purity, which leads to exceptionally long
spin coherence. These properties position silicon single-
photon emitters and
spin-
photon interfaces among the most promising hardware platforms for implementing
quantum networks and distributed
quantum information processors. This review summarizes the current state of the art and open challenges towards coherent single-
photon sources and scalable
spin-
photon interfaces based on color centers and erbium dopants in nanophotonic silicon structures.
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All authors Kilian Sandholzer, Ian Berkman, Peter Deák, Carlos Errando-Herranz, Petros-Panagis Filippatos, Adam Gali, Andreas Gritsch, Andreas Reiserer
Materials Science
Hsin-Mei Ho, Michael Lorke and Peter Kratzer
Heterostructures composed of transition metal dichalcogenides (TMDCs) and organic molecules have been extensively explored for optoelectronic devices. To maximize their application potential, it is essential to investigate the electronic band structures, which govern the charge response of the interfaces to external perturbations. Based on $GW$ calculations, we present a study of organic-inorganic
heterostructures with anthracene molecules adsorbed on monolayer MoS2. Building on previous investigations of organic molecule self-assembly at surfaces, we systematically analyze anthracene configurations with various molecular orientations and surface coverages. Partially self-consistent $GW_0$ provides qualitatively different level
alignments from those in DFT. Whereas the systems with sparse, horizontally adsorbed anthracenes exhibit type-I
alignment, densely packed anthracenes in the head-on position lead to type-II
alignment, which indicates the strong dependence of quasiparticle corrections on the interfacial configuration. These findings highlight the importance of level-
alignment predictions for both interpreting experiments and guiding the design of organic-inorganic
heterostructures.
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Quantum Gases
Universal Behavior on the Relaxation Dynamics of Far-From-Equilibrium Quantum Fluids
Sarah Sab, Michelle A. Moreno-Armijos, Arnol D. García-Orozco et al. (+6 more)
Investigating the initial conditions that lead many-body
quantum systems to an out-of-
equilibrium state is fundamental for understanding their thermalization dynamics. In this work we observe the relaxation for two regimes of excitation that can drive the turbulent Bose-Einstein condensate into two distinct final states, and are defined by the amount of energy injected into the system. The subcritical regime is characterized by a lower injection of energy, which can lead to an inverse particle cascade and, consequently, to the BEC mode repopulation during the relaxation process. The supercritical regime is marked by a higher energy injection, that may lead to the BEC dissolution and a final thermal state. In both cases we observe relaxation stages that exhibit the same key features: a direct cascade, a non-thermal fixed point with the same exponents, a prethermalization region and, finally, the thermalization of the system. In the final thermalization stage, universal scaling is observed for both regimes, even though their final states are completely different. By analyzing the coherence length of our turbulent cloud, we clearly visualize the recovery and the loss of the coherence for the subcritical and supercritical regimes after relaxation. These results indicate that the
evolution of
turbulence occurs independent of its initial conditions and of the final state achieved.
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All authors Sarah Sab, Michelle A. Moreno-Armijos, Arnol D. García-Orozco, Gabriel V. Fernandes, Ying Zhu, Amilson R. Fritsch, Hélène Perrin, Sergey Nazarenko, Vanderlei S. Bagnato
Materials Science
Efficient first-principles modeling of complex molecular crystals at sub-chemical accuracy
Benjamin X. Shi, Kristina M. Herman, Flaviano Della Pia et al. (+5 more)
Molecules can form myriad crystalline polymorphs, each with distinct properties affecting their performance across diverse applications, from pharmaceuticals to functional materials and more. Predicting the thermodynamically most stable polymorph from first principles remains a formidable challenge. It requires methods that scale to large, technologically-relevant molecules while achieving very high accuracy (below 1 kJ/mol) on relative
lattice energies. Such accuracy, often termed sub-chemical accuracy, is generally beyond the reach of the workhorse density functional theory (DFT). In this work, we introduce a framework, combining advances in correlated wavefunction theory (cWFT) and the many-body expansion, to deliver accurate, cost-effective predictions of complex molecular
crystals. For 23 organic molecules and 13 ice polymorphs, we predict
crystal lattice energies to within experimental uncertainties at costs comparable to hybrid DFT, while being several orders of magnitude more efficient than previous cWFT approaches. We extend this approach to a set of large, drug-like molecules including axitinib and ROY, previously inaccessible to cWFT and where DFT is insufficient, achieving sub-chemical accuracy on the relative energies between challenging polymorphs. With the reference data generated throughout this work, we have been able to further parametrize a DFT functional with unprecedented accuracy aligning with our predictions. This cWFT framework as well as DFT functional are made openly available, providing new ranking tools to facilitate efficient high-throughput screening of molecular
crystal polymorphs.
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All authors Benjamin X. Shi, Kristina M. Herman, Flaviano Della Pia, Venkat Kapil, Andrea Zen, Peter R. Nagy, Sotiris Xantheas, Angelos Michaelides
Mesoscale and Nanoscale Physics
Controlling Terahertz Spintronic Photocurrents in 2D-Semiconductor|Ferromagnet Heterostructures through a Functional Hybrid Interface
A. Alostaz, R. Rouzegar, Eddie Harris-Lee et al. (+9 more)
A profound understanding of terahertz (THz)
spin and charge currents in
heterostructures involving ferromagnets (FMs) and two-dimensional (2D) materials promises emerging applications in high-speed sensing and data processing. Yet, ultrafast experimental insights remain very limited. Here, we study the efficient photo-generation of THz
spin and charge currents in
bilayers made from the transition-metal dichalcogenide (TMD) MoS2 and the FM Co. We find that the efficiency of current generation strongly depends on the pump
photon energy, as previously reported. Surprisingly, however, we observe that the current dynamics remain identical for pump
photon energies above and below the MoS2 band gap. Supported by ab-initio calculations, we conclude that an interfacial hybrid metallic layer forms at the MoS2/Co boundary that has a pronounced
photon-energy-dependent absorptance. Thus, the hybrid interfacial layer effectively acts like a pump-energy transducer that increases the
spin-current generated in the nearby Co. Our results uncover the vital role of interfacial hybridization as a yet unexplored mechanism for efficient generation of ultrafast photocurrents in 2D-TMD|FM structures.
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All authors A. Alostaz, R. Rouzegar, Eddie Harris-Lee, Xinhou Chen, Shijie Wang, Kuan Eng Johnson Goh, D. E. Buergler, H. Yang, Elbert E. M. Chia, S. Sharma, T. Kampfrath, T. S. Seifert
Strongly Correlated Electrons
Anomalous Diffusion and Superdiffusion in Integrable Spin Chains via a Soliton Gas Mapping
Andrew Urilyon, Romain Vasseur, Sarang Gopalakrishnan et al. (+1 more)
We introduce a multi-species
soliton gas in which each species has a distinct effective scattering length, and the repulsive scattering shift is set by the smaller of the two colliding particles. We argue that this model shares key quasiparticle and scattering features with the XXZ
spin chain. We show that fixing only the functional decay of bare velocities with particle size is sufficient to reproduce the XXZ
spin-transport phase diagram:
diffusion (with anomalous fluctuations) in the anisotropic regime and superdiffusion at the isotropic point. We then demonstrate that the statistics of charge transfer differs qualitatively from that of particle trajectories. For large particles, trajectories are Gaussian in the diffusive regime and appear to exhibit KPZ statistics at the isotropic point, providing a direct microscopic signature of KPZ physics in integrable quasiparticle motion. In contrast, charge-transfer fluctuations are anomalous in the anisotropic regime, while they cross over to Gaussian statistics at late times at the isotropic point, reconciling non-Gaussian trajectory fluctuations with Gaussian charge-transfer statistics. Our results establish this
soliton gas as a minimal framework for anomalous
spin and charge transport in integrable systems, and offer new insight into the origin of KPZ fluctuations in isotropic integrable models.
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All authors Andrew Urilyon, Romain Vasseur, Sarang Gopalakrishnan, Jacopo De Nardis
Statistical Mechanics
Kinetic energy fluctuations and specific heat in generalized ensembles
Sergio Davis, Catalina Ruíz, Claudia Loyola et al. (+2 more)
We derive an exact generalization of the well-known Lebowitz–Percus–Verlet (LPV) formula that relates the kinetic energy fluctuations of an isolated system to its specific heat. Our general formula, obtained by the application of expectation identities, is valid for arbitrary steady–state ensembles and system sizes, expressing the relative variance of the kinetic energy in terms of the variance of total energy and the microcanonical specific heat. The usual microcanonical LPV formula can be readily recovered as a particular case where energy fluctuations vanish. We test the validity of the generalized formula by performing Monte Carlo simulations of a superstatistical system of harmonic oscillators, as well as by exact calculation of energy variances in a uniform–energy ensemble, discussing its relevance to systems exhibiting negative heat capacity and ensemble inequivalence, as encountered in finite
nuclei and self–gravitating models. Our results may provide useful in the study of non-
equilibrium phase transitions in finite systems.
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All authors Sergio Davis, Catalina Ruíz, Claudia Loyola, Carlos Femenías, Joaquín Peralta
Disordered Systems and Neural Networks
Topological Gyromorphs
Laura Gómez Paz, Justin Schirmann, Adam Yanis Chaou et al. (+2 more)
Gyromorphs are a new class of disordered systems that combine an amorphous-like absence of translational order with quasi-long-range rotational order. Gyromorphs can outperform quasicrystals or hyperuniform arrangements in forming isotropic band gaps, suggesting an avenue to realize robust disordered topological phases. However, gyromorphs lack exact rotational
symmetry, which is only realized on average, posing an obstacle for existing real-space invariants to correctly diagnose topological gyromorphs. In this work we show that gyromorphs can host higher-order topological insulating (HOTI) phases protected by average rotational
symmetry, and we develop and systematically compare tools for diagnosing topological phases protected by such
symmetry. We introduce
symmetry indicators of the effective
Hamiltonian based on average rotational
symmetries which, when combined with the spectral localizer and a scattering invariant, draw a consistent topological phase diagram. Our work unlocks gyromorphs as a novel platform to study topological phases beyond
crystals, quasicrystals, and amorphous materials.
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All authors Laura Gómez Paz, Justin Schirmann, Adam Yanis Chaou, Isidora Araya Day, Adolfo G. Grushin
Statistical Mechanics
Crossover from generalized to conventional hydrodynamics in nearly integrable systems under relaxation time approximation
Saikat Santra, Maciej Łebek and Miłosz Panfil
Upon breaking the integrability, the equations of generalized hydrodynamics (GHD) are supplemented by a Boltzmann collision term. Such terms are typically complicated and stem from a perturbative treatment of integrability-breaking terms in the
hamiltonian. In our work, we study a simplified version of the collision operator in a form of relaxation time approximation familiar from kinetic theory. We explicitly compute transport coefficients which characterize the Navier-Stokes (NS) hydrodynamic regime emerging at large space-time scales. We also thoroughly study the crossover between GHD and NS hydrodynamic descriptions, identifying relevant characteristic space-time scales for the transition. In particular, we show how the emergence of NS hydrodynamics is visible in dynamics of conserved and non-conserved charge densities, and in hydrodynamic two-point functions.
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Quantum Gases
Lee-Huang-Yang dynamics emergent from a direct Wigner representation
King Lun Ng, Maciej Bartłomiej Kruk and Piotr Deuar
We demonstrate how the beyond-mean-field Lee-Huang-Yang (LHY) corrections and its related physics can be naturally incorporated into the representation of an ultracold Bose gas using the truncated Wigner approach without invoking effective energy terms or local density approximation. By generating a Bogoliubov ground-state representation with appropriately tailored bare interaction strength $g_0$ and condensate density $n_0$, the expected initial energy and densities are obtained while retaining access to
quantum effects beyond the reach of the extended Gross-Pitaevskii equation (EGPE) formulation. This approach enables the study of correlations, coherence decay, single realisations, and the onset of
quantum fluctuation effects with growing interaction strength. Numerical demonstrations for a weakly interacting single-component Bose gas show that observables deviate significantly from both the plain GPE and the EGPE incorporating LHY corrections. In regimes of strong interaction, many of the interference effects predicted by the GPE and EGPE are suppressed, and the EGPE offers no improvement over the plain GPE compared to the full Wigner model. In the weakly interaction limit, the EGPE appears accurate but resolving its deviation from mean-field results requires extensive ensemble averaging.
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Soft Condensed Matter
Anisotropic Diffusion in Lyotropic Chromonic Liquid Crystal using Fluorescence Recovery After Photobleaching
Kyu Hwan Choi, Jiyong Cheon, Joonwoo Jeong et al. (+1 more)
Anisotropic
diffusion governs transport in a wide range of soft and biological materials, where microstructure and molecular interactions jointly shape how matter moves. Here, we quantitatively investigate anisotropic molecular transport in lyotropic chromonic
liquid crystals (LCLCs) using fluorescence recovery after photobleaching (FRAP). Disodium cromoglycate (DSCG) serves as a model LCLC system, and
diffusion is measured across isotropic, nematic, and columnar phases as concentration and temperature are varied. To disentangle the roles of microstructure and molecular interactions, we employ two fluorescent tracers with distinct affinities for the LCLC aggregates: Acridine Orange (AO), which intercalates into DSCG aggregates, and Bodipy, which interacts weakly and remains largely in the aqueous phase.
Fourier-space FRAP analysis independently resolves the parallel and perpendicular
diffusion coefficients for both dyes relative to the
liquid-
crystal alignment. In the nematic phase,
diffusion becomes anisotropic, with faster transport along the
liquid-
crystal director. As the DSCG concentration increases, AO dye molecules that are strongly coupled to the aggregates exhibit a slowdown in all directions, reflecting enhanced packing and steric confinement of the LC microstructure. In contrast, weakly interacting Bodipy dye molecules display enhanced transport along the
alignment direction as the DSCG concentration increases in the nematic regime, suggesting the emergence of microscopic channels that guide motion, analogous to transport in oriented porous media. These results reveal how the evolving microstructure of LCLCs controls effective
diffusion and provide a quantitative framework for understanding and designing anisotropic transport in aligned soft materials.
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All authors Kyu Hwan Choi, Jiyong Cheon, Joonwoo Jeong, Sho C. Takatori
Statistical Mechanics · Cross-listed from nlin.CD
Basin Metamorphosis in Coupled Phase Oscillators
Jin Yan, Ayumi Ozawa, Hiroshi Kori et al. (+1 more)
We investigate the global basin structure of twisted states in nearest-neighbor coupled phase oscillators with a common phase shift $\alpha$. As $\alpha$ increases, basin boundaries become progressively more complex, with their fractal dimension growing toward that of the full ambient phase space. We
conjecture that the basins eventually become riddled-like as the system approaches the limit $\alpha\to \frac{\pi}{2}$, where the dynamics becomes volume-preserving. We characterize the transient dynamics via the stabilization time of the winding number and demonstrate that it grows with system size. The scaling accelerates at larger phase shifts, transitioning from logarithmic to power-law behavior. We further analyze the dynamical origin of these long transients. Our results demonstrate how a single phase-shift governs fractal basin complexity and provide new insights into the global geometry and transient dynamics of multistable, yet non-chaotic, coupled phase oscillators.
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All authors Jin Yan, Ayumi Ozawa, Hiroshi Kori, Yuzuru Sato
Materials Science
Elucidating different $NO_{2}$ sensing mechanisms in oxidized PbS nanocrystals
Fernando M. Fernandes, Fouad El Haj Hassan, Sophie Hermans et al. (+1 more)
In this work we provide an in-depth analysis of the sensing mechanisms of $NO_{2}$ by lead-sulfide nanocrystals (PbS-NCs). A detailed model for the sorption mechanism is proposed, and the correlation is established between experimental sensing characteristics and the surface composition, based on both experimental characterization and ab initio (DFT) simulations. We demonstrated how the sensitivity and the sensing dynamic response can be tuned by a post-deposition multistep dry-thermal process at mild temperature, that alternates
vacuum-assisted annealing and heating in open-air. Sensors with different surface compositions were fabricated, and their dynamic response was characterized at low concentration of $NO_{2}$ (0.5 ppm) in air, at ambient temperature. DFT simulations indicate that both surface stoichiometry and oxidation critically govern $NO_{2}$ interaction on PbS, with sulfur-rich terminations favoring weaker binding and faster desorption, while intermediate oxidation enhances interaction and overoxidation leads to surface passivation, in agreement with the measured experimental sensing dynamics. By linking surface composition, adsorption chemistry, and resistance transduction within a single framework, this work provides clear indications to design room-temperature, low-ppm $NO_{2}$ microsensors fabricated through a simple and scalable processes.
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All authors Fernando M. Fernandes, Fouad El Haj Hassan, Sophie Hermans, Benoît Hackens