Quantum Gases · Cross-listed from physics.optics
Nonlinear quadrupole topological insulators
Rujiang Li, Wencai Wang, Yongtao Jia et al. (+3 more)
Higher-order topological
insulators (HOTIs) represent a family of topological phases that go beyond the conventional bulkboundary correspondence. d-dimensional n-th order HOTIs maintain (d - n)-dimensional gapless boundary states (in particular, zero-dimensional corner states in the case of d = n = 2). HOTIs of the Wannier type cam be extended into the nonlinear regime. Another prominent class of HOTIs, in the form of multipole
insulators, was investigated only in the linear regime, due to the challenge of simultaneously achieving both negative hopping and strong nonlinearity. Here we propose the concept of nonlinear quadrupole topological
insulators (NLQTIs) and report their experimental realization in an electric
circuit lattice. Quench-initiated dynamics gives rise to nonlinear topological corner states and topologically trivial corner
solitons, in weakly and strongly nonlinear regimes, respectively. Furthermore, we reveal the formation of two distinct types of bulk
solitons, one existing in the middle finite gap under the action of weak nonlinearity, and another one found in the semi-infinite gap under strong nonlinearity. This work realizes another member of the nonlinear HOTI family, suggesting directions for exploring novel
solitons across a broad range of topological
insulators.
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All authors Rujiang Li, Wencai Wang, Yongtao Jia, Ying Liu, Pengfei Li, Boris A. Malomed
Materials Science
The prospects of nonthermal magnetization switching in near-compensated rare earth iron garnets
N. I. Gribova, D. O. Ignatyeva, N. A. Gusev et al. (+2 more)
Ultrafast
spin dynamics in a magnetically compensated rare earth iron garnet film driven by femtosecond optical pulses through the inverse Faraday effect is theoretically investigated. Numerical simulations based on the equations of motion for the Néel vector reveal the temporal
evolution of the system and its trajectories in the effective potential landscape tuned by external field and temperature. The results demonstrate a clear threshold behavior: weak pulses induce only oscillations around the initial
equilibrium state, while a stronger excitation results in a deterministic magnetization switching. The switching threshold is determined by the
magnetic state of the sample on its phase diagramme as well as on the
laser pulse helicity. This mechanism demonstrates a non-thermal and even non-absorptive pathway towards optomagnonic logic and
memory devices.
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All authors N. I. Gribova, D. O. Ignatyeva, N. A. Gusev, A. K. Zvezdin, V. I. Belotelov
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Rare Event Analysis of Large Language Models
Jake McAllister Dorman, Edward Gillman, Dominic C. Rose et al. (+2 more)
Being probabilistic models, during inference large
language models (LLMs) display rare events: behaviour that is far from typical but highly significant. By definition all rare events are hard to see, but the enormous scale of LLM usage means that events completely unobserved during development are likely to become prominent in deployment. Here we present an end-to-end framework for the systematic analysis of rare events in LLMs. We provide a practical implementation spanning theory, efficient generation strategies, probability estimation and error analysis, which we illustrate with concrete examples. We outline extensions and applications to other models and contexts, highlighting the generality of the concepts and techniques presented here.
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All authors Jake McAllister Dorman, Edward Gillman, Dominic C. Rose, Jamie F. Mair, Juan P. Garrahan
Mesoscale and Nanoscale Physics
Current precision in interacting hybrid Normal-Superconducting systems
Nahual Sobrino, Fabio Taddei, Rosario Fazio et al. (+1 more)
We study Andreev-mediated transport and current fluctuations in interacting normal-superconducting
quantum-dot systems. Using a generalized master equation based on real-time diagrammatics and full counting statistics, we compute the steady-state current, zero-frequency noise, and rate of
entropy production in the large superconducting-gap limit. We show how Coulomb interactions modify Andreev-mediated transport by renormalizing resonant conditions and suppressing superconducting coherence, leading to a pronounced reduction of current precision even when average currents are only weakly affected. These effects are particularly evident at high temperatures, where conventional Coulomb-blockade features are thermally smeared while fluctuation properties remain highly sensitive. By analyzing thermodynamic uncertainty relations, we demonstrate that violations of the
quantum bound present in the noninteracting regime are progressively reduced and eventually suppressed as interactions increase, whereas the recently proposed hybrid bound remains satisfied. Our results clarify how Coulomb interactions, and nonequilibrium fluctuations jointly determine transport properties in hybrid superconducting devices, and establish current precision as a robust
benchmark for interacting Andreev transport beyond the noninteracting limit.
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All authors Nahual Sobrino, Fabio Taddei, Rosario Fazio, Michele Governale
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Diffusiophoresis of a non-polar fluid droplet laden with soluble ionic surfactants
Subrata Majhi and Somnath Bhattacharyya
We investigate the diffusiophoresis of a non-polarizable droplet laden with soluble ionic surfactant, for which the surface charge arises from adsorption of surfactant at the fluid-fluid interface. Unlike previous studies that assume either a fixed surface charge or instantaneous
equilibrium between the interface and the adjacent electrolyte, we formulate the interfacial transport based on the mass-balance framework incorporating Langmuir adsorption-desorption kinetics and finite surface diffusivity. The coupled electrokinetic problem is solved using a perturbation approach. Analytical expressions for the droplet mobility and interfacial velocity are derived for insoluble surfactants. We demonstrate that assuming uniform, immobile surface charge leads to unphysical predictions, including negative chemiphoresis and singular mobility, whereas allowing the surface charge to evolve through interfacial surfactant redistribution yields continuous and physically consistent droplet diffusiophoresis. Interfacial kinetic exchange is found to play a central role. Increasing the desorption rate enhances surfactant redistribution and Marangoni stress, weakens the negative mobility, reverses the direction of motion through competition between electrophoretic and chemiphoretic contributions, and subsequently leads to a strong enhancement of positive mobility before eventual saturation in the transport-limited regime. The dependence of mobility on viscosity ratio and electrolyte composition of different salts further reveals how mixed electrolytes provides a robust means of tuning droplet motion. This study highlights the critical role of finite-rate surfactant dynamics and interfacial transport in determining the diffusiophoresis of fluid particles, with implications for manipulating droplets in microfluidic and varying-salinity environments.
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Materials Science
Damage accumulation induced metal-insulator transition through ion implantation of ScN thin films
Charlotte Poterie, Marc Marteau, Per Eklund et al. (+3 more)
Ion implantation is a powerful approach for tuning the electrical properties of materials through controlled doping and defect engineering, with applications in thermoelectrics and microelectronics. Scandium nitride (ScN) is particularly sensitive to irradiation-induced disorder, with transport properties spanning several orders of magnitude and multiple conduction mechanisms involved. In this study, we investigate the
evolution of electrical transport in epitaxial ScN thin films undergoing accumulated irradiation damage at an initial defect state. A phenomenological damage-accumulation model was successfully combined with temperature dependent resistivity and
Hall effect measurements to elucidate the impact of defect buildup on electrical transport and to provide physically grounded, quantitative insight into the nature and accumulation of irradiation-induced defects. It reveals two distinct defects-generation regimes of electrically active defects. At low doses, direct-impact damage produces stable and isolated acceptor-type complex defects, (VSc-X) with VSc a scandium vacancy and X denoting residual
impurities, leading to a gradual increase in resistivity. At higher doses, defect accumulation dominates through a multi-hit process, giving rise to point-defect buildup and carrier localization, resulting in hopping-dominated transport. This localized regime is thermally unstable and recovers upon low-temperature annealing. We further demonstrate that the residual defect landscape strongly influences both the critical dose for the metal-
insulator transition and the localization strength: films grown on Al2O3 exhibit an earlier transition and weaker localization than those grown on MgO. These results highlight ion implantation as an effective route for engineering disorder-induced localization in ScN, with the initial film quality playing a decisive role.
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All authors Charlotte Poterie, Marc Marteau, Per Eklund, Thierry Cabioch, Jean-Francois Barbot, Arnaud le Febvrier
Materials Science
Optimized Photoemission from Organic Molecules in 2D Layered Halide Perovskites
Muhammad S. Muhammad, Dilruba A. Popy, Hamza Shoukat et al. (+12 more)
In recent years, hybrid organic-inorganic metal halides have been at the forefront of materials research. Typically, the functional (e.g., optoelectronic) properties of hybrid halides are derived from the inorganic structural part, whereas the organic structural units can add extra advantages in terms of stability,
rigidity, and processability. Here, we report the design, synthesis, and characterization of two new hybrid materials in which the outstanding photophysical properties originate from the organic structural part. The new compounds, (C15H16N)2CdCl4 and ((Br)C15H15N)2CdCl4, have 2D layered Ruddlesden-Poppertype perovskite structures. These hybrids are blue-white light emitters just like their corresponding pure organic salts, but with much improved emission efficiencies. Optical spectroscopy and density functional theory (DFT) studies confirm that photoemission comes from the trans-stilbene organic cations. The photoluminescence
quantum yield (PLQY) values of these new materials are among the highest known, 50.83 % and 26.60 % for (C15H16N)2CdCl4 and ((Br)C15H15N)2CdCl4, respectively. This is up to a 5-fold increase as compared to the light emission efficiency of the precursor salt C15H16NCl (PLQY of 10.33 %). Alongside their outstanding optical properties, their environmental and thermal stability allow their consideration for potential practical applications such as radiation detection. This work shows that hybrid metal halides can be compositionally and structurally engineered to have highly efficient photoemission originating from the organic components for fast scintillation applications.
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All authors Muhammad S. Muhammad, Dilruba A. Popy, Hamza Shoukat, John M. Lane, Neeraj Rai, Vojtech Vanecek, Zdeneek Remes, Romana Kucerkova, Vladimir Babin, Chenjia Mi, Yitong Dong, Mark D. Smith, Novruz G. Akhmedov, Daniel T. Glatzhofer, Bayram Saparov
Strongly Correlated Electrons
Investigation of the Electronic Structure and Spin-State Crossover in LaCoO3 Using Photoemission Spectroscopy
Sayari Ghatak, Abhishek Das, Andrei Gloskovskii et al. (+1 more)
Photoemission spectroscopy is a powerful technique for studying electronic structure and
spin-state transitions, as it reveals changes in the orbital configuration accompanying a
spin-state crossover. In this report, we combine excitation-energy-, temperature-, and geometry-dependent photoemission measurements to probe the electronic structure of LaCoO3 across its thermally driven
spin-state transition. By systematically comparing valence-band spectra across a wide
photon-energy window - from surface-sensitive soft x-ray photoemission spectroscopy (SXPS) to bulk-sensitive hard x-ray photoemission spectroscopy (HAXPES) - we identify the Co 3d-derived feature (A) along with the O 2p-dominated features (B and C), and explain their relative
evolution in terms of
photon-energy-dependent photo-ionization cross-section ratios. The thermally induced
spin-state crossover is demonstrated using temperature-dependent SXPS valence-band spectra, which show a progressive suppression of the feature A with heating. Geometry-dependent HAXPES measurements further clarify how the signature of the
spin-state transition in LaCoO3 is intricately linked to the orbital-selective response of the t2g and eg states. Additionally, angular-dependent photo-ionization cross-section analysis provides a consistent description of the polarization dependence observed in HAXPES. Finally, configuration-interaction analysis of the Co 2p core-level spectra reveals that LaCoO3 evolves from a predominantly low-
spin ground state at low temperature to a mixed low-
spin/high-
spin configuration at elevated temperatures, with the high-
spin fraction reaching about 30 percent at 400 K. The temperature
evolution of the core-level line shape thus establishes Co 2p photoemission as a sensitive quantitative probe of
spin-state transitions in LaCoO3.
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All authors Sayari Ghatak, Abhishek Das, Andrei Gloskovskii, Dinesh Topwal
Materials Science
Bridgman method grown $Cs_2Li_3I_5$: an inter-alkali metal scintillator with high lithium content
Katerina Krehlikova, Vojtech Vanecek, Robert Kral et al. (+5 more)
In this study, we report on the growth of ternary caesium lithium iodide ($Cs_2Li_3I_5$, CLI) bulk
crystals, both undoped and doped with thallium (Tl) and indium (In), using the miniaturised vertical Bridgman method (mVB). X-ray Powder Diffraction (XRPD) confirmed the presence of the ternary CLI phase in all three
crystals, with CLI : In appearing homogeneous structure-wise throughout the entire ingot. Measurements of radioluminescence (RL), photoluminescence emission (PL), photoluminescence excitation (PLE) spectra, and photoluminescence decay kinetics (PL decay) demonstrated that the primary luminescence centers originate from the
matrix itself. When doped with thallium, the efficiency of the luminescence was significantly increased. Furthermore, CLI : Tl and CLI : In
crystals exhibited emission spectra similar to those of their doped caesium iodide counterparts, CsI : Tl and CsI : In, respectively. The main component of the PL decay was 523 ns, 557 ns, and 554 ns for the undoped, Tl+-doped, and In+-doped
crystals, respectively. It is worthy of note that only CLI : Tl exhibited a single exponential decay. Differential Scanning Calorimetry (DSC) measurements revealed two endothermic peaks corresponding to the eutectic and liquidus temperature for CLI and CLI : In, indicating that this ternary compound has a congruent melting behaviour. Finally, the melting point of CLI was estimated to be approximately 220 {\deg}C.
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All authors Katerina Krehlikova, Vojtech Vanecek, Robert Kral, Romana Kucerkova, Petra Zemenova, Jan Rohl{\i}cek, Petr Prusa, Katerina Rubesova
Materials Science
In-depth study of spectroscopic properties of new $Pr^{3+}$-ion doped low-phonon sesquisulfide $Lu_2S_3$ material for mid-IR laser sources
Martin Fibrich, Jan Sulc, Lubomír Havlak et al. (+6 more)
$Lu_2S_3$ material from the family of sesquisulfide hosts appears to be a promising low-
phonon material for use as a
laser gain medium allowing for a
laser emission over a broad spectral range from ultraviolet to far mid-infrared wavelengths. In this paper, a praseodymium-ion doped $Lu_2S_3$ single
crystal grown by micro-pulling down technique is investigated with focus on its spectroscopic properties. The Raman, excitation, and luminescence spectra are presented. By selective excitation of the main energy levels of $Pr^{3+}$-ions, 26 luminescence transitions of the $Pr:Lu_2S_3$
crystal spanning the 0.49 to 5.5 $\mu$m wavelength range have been identified. The correct assignment of the observed luminescence spectra to the respective $Pr^{3+}$ energy-level transitions was confirmed by the calculation of the optimized squared reduced-
matrix elements for the tensor operators U(k) and L + gS.
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All authors Martin Fibrich, Jan Sulc, Lubomír Havlak, Vítezslav Jarý, Robert Kral, Vojtech Vanecek, David Vyhlidal, Helena Jelinkova, Martin Nikl
Strongly Correlated Electrons
Physical properties of RhGe and CoGe single crystals synthesized under high pressure
Shangjie Tian, Xiangjiang Dong, Bowen Zhang et al. (+4 more)
Chiral topological semimetals hosting multifold
fermions and exotic surface states represent a frontier in topological materials research. Among them, noncentrosymmetric cubic B20 compounds-notably transition-metal silicides and germanides-offer a unique platform for realizing
symmetry-protected topological phases and unconventional optoelectronic responses. Here, we report the physical properties of RhGe and CoGe single
crystals with B20 structure in detail. Transport measurements reveal metallic behavior with characteristic
Fermi-
liquid scaling at low temperatures, while magnetization results confirm paramagnetism in both compounds. In addition, both of materials exhibit low carrier concentrations with small electronic specific heat coefficient, indicating their semimetal feature with weak electronic correlations. Such high-quality CoGe and RhGe single
crystals provide a material platform to explore the
evolution of multifold
fermions and the instability of helicoid-arc surface states with
spin-orbit coupling and surface environment in B20 material systems.
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All authors Shangjie Tian, Xiangjiang Dong, Bowen Zhang, Zhijun Tu, Runze Yu, Hechang Lei, Shouguo Wang
Mesoscale and Nanoscale Physics
Chirality Driven Ratchet Currents in Two-Dimensional Tellurene with an Asymmetric Grating
M. D. Moldavskaya, L. E. Golub, Chang Niu et al. (+2 more)
The emergence of the terahertz (THz) ratchet effect is a rapidly expanding field of research that utilizes broken spatial
symmetry in low-dimensional materials to rectify alternating current (AC) induced by THz fields into direct current (DC). This mechanism is highly promising for next-generation, room-temperature terahertz applications, particularly in high-speed, sensitive detection and imaging. In this work, we explore a ratchet effect generated in two dimensional tellurene, a novel promising
semiconductor material consisting of helical atomic chains, creating a structure with inherent chirality. As a key result, the DC circular ratchet current flowing in the
chiral axis direction $c$ is determined by the helicity of the radiation and can be reversed by switching the helicity from right to left handed. The circular ratchet effect excited by THz
laser radiation is demonstrated for room temperature. The effect is demonstrated at various gate voltages when the
Fermi level lies in vicinity of the Weyl point in the conduction band, in the band gap, and in the valence band with almost
parabolic energy dispersion. The results are described by the developed microscopic theory based on the Boltzmann kinetic equation approach.
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All authors M. D. Moldavskaya, L. E. Golub, Chang Niu, Peide D. Ye, S. D. Ganichev
Strongly Correlated Electrons
Quasi-one-dimensional spin excitations in the iron pnictide NaFe$_{0.53}$Cu$_{0.47}$As
Yifan Wang, David W. Tam, Weiyi Wang et al. (+8 more)
Spectroscopic measurements in model one-dimensional (1D) correlated systems offer insights for understanding their two-dimensional counterparts, which include the cuprate and iron pnictide/chalcogenide
superconductors. A major challenge is the identification of such correlated systems with dominantly 1D physics. In this work, inelastic
neutron scattering measurements on NaFe$_{0.53}$Cu$_{0.47}$As single
crystal directly reveal quasi-1D
spin excitations, resulting from atomic order that lead to
magnetic Fe and nonmagnetic Cu chains. The dominant exchange interaction is
antiferromagnetic along the chain ($SJ_{\rm \parallel}\approx90.1(3)$~meV), whereas the inter-chain couplings are much weaker ($SJ_{\rm \perp}\approx-2.4(1)$~meV and $SJ_{\rm c}\approx0.15(5)$~meV). The quasi-1D
spin excitations in NaFe$_{0.53}$Cu$_{0.47}$As stem from both the Néel and stripe vectors, with Néel excitations sensitive to Fe
impurities on the Cu site. The
spin excitations in quasi-1D NaFe$_{0.53}$Cu$_{0.47}$As and quasi-2D FeSe exhibit a striking resemblance, suggesting a common origin for their coexistent stripe and Néel excitations. Our findings demonstrate
magnetic dilution in NaFeAs leads to dimension reduction of its
magnetic degree of freedom, presenting a strategy for discovering low-dimensional
quantum materials.
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All authors Yifan Wang, David W. Tam, Weiyi Wang, R. A. Ewings, J. Ross Stewart, Masaaki Matsuda, Chongde Cao, Changle Liu, Rong Yu, Pengcheng Dai, Yu Song
Mesoscale and Nanoscale Physics
Probing valley quantum oscillations via the spin Seebeck effect in transition metal dichalcogenide/ferromagnet hybrids
Xin Hu, Yuya Ominato and Mamoru Matsuo
We theoretically investigate
spin-valley-locked tunneling transport in a transition-metal dichalcogenide/
ferromagnetic-
insulator heterostructure under a perpendicular
magnetic field, driven by the
spin Seebeck effect. We demonstrate that
spin-valley coupling together with the
magnetic-field-induced valley-asymmetric Landau-level structure enables the generation of a valley-polarized
spin current from valley-selective
spin excitation. We compare the
spin current and the valley-polarized
spin current in the conduction and valence bands and clarify their distinct microscopic origins. We predict pronounced
quantum oscillations of the valley-polarized
spin current, providing a clear experimental signature of quantized valley states.
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Statistical Mechanics
Second law of thermodynamics in closed quantum many-body systems
Yuuya Chiba, Yasushi Yoneta, Ryusuke Hamazaki et al. (+1 more)
The second law of thermodynamics for adiabatic operations – constraints on state transitions in closed systems under external control – is one of the fundamental principles of thermodynamics. On the other hand, it is recently established that even pure
quantum states can represent thermal
equilibrium. However, pure
quantum states do not satisfy the second law in that they are not passive, i.e., work can be extracted from them if arbitrary
unitary operations are allowed. It therefore remains unresolved how
quantum mechanics can be reconciled with thermodynamics. Here, based on our key
quantum-mechanical notions of thermal
equilibrium and adiabatic operations, we address the emergence of the second law for adiabatic operations in the thermodynamics limit. We first introduce infinite-observable macroscopic thermal
equilibrium (iMATE); a
quantum state, including pure states, is in iMATE if the expectation values of all additive observables agree with their
equilibrium values. We also introduce a macroscopic operation as
unitary evolution generated by a time-dependent additive
Hamiltonian, which is regarded as corresponding to adiabatic operations. Employing these concepts, we show that no extensive work can be extracted from any
quantum state in iMATE through any macroscopic operations. Furthermore, we introduce a
quantum-mechanical form of
entropy density such that it agrees with thermodynamic
entropy density for any
quantum state in iMATE. We then prove that for any initial state in iMATE, this
entropy density cannot be decreased by any macroscopic operations, followed by a time-independent relaxation process. Our theory thus proves two different forms of the second law, by adopting macroscopically reasonable classes of observables,
equilibrium states, and operations. We also discuss the time scales of macroscopic operations in these results.
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All authors Yuuya Chiba, Yasushi Yoneta, Ryusuke Hamazaki, Akira Shimizu
Mesoscale and Nanoscale Physics
Resonant absorption and linear photovoltaic effect in ferroelectric moiré heterostructures
V. V. Enaldiev and Z. Z. Alisultanov
Twisted
bilayers, featuring interfacial ferroelectricity in the form of array of polar domains, combined with incommensurate two-dimensional layers in a single van der Waals
heterostructures allows for generation of purely electrostatic moiré superlattice potentials in the latter. We study electronic and optoelectronic properties of such
heterostructures composed of
graphene stacked with the twisted ferroelectric
bilayers and show that doping of
graphene substantially affects mini-band structures because of screening of free carriers. We demonstrate that formation of van Hove singularities in density of states modifies linear and second-order responses of the structures leading to resonant absorption and linear photovoltaic effect, respectively. The latter is generated solely by a shift photocurrent, arising only with account of virtual optical transitions, whereas an injection photocurrent is forbidden by
symmetry.
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Statistical Mechanics · Cross-listed from q-bio.PE
Habitat heterogeneity and dispersal network structure as drivers of metacommunity dynamics
Davide Bernardi, Alice Doimo, Giorgio Nicoletti et al. (+5 more)
Spatial structure and species interactions jointly shape the dynamics and biodiversity of ecological systems, yet most theoretical models either neglect spatial heterogeneity or sacrifice analytical tractability. Here, we provide a unified microscopic, mechanistic framework for deriving effective metapopulation and metacommunity models from individual-based ecological dynamics on arbitrary dispersal networks. The resulting coarse-grained description features an effective dispersal kernel that encodes both microscopic dynamical parameters and network
topology. Based on this framework, we demonstrate exact analytical results for species persistence in both homogeneous and heterogeneous landscapes, including a generalization of the classical concept of metapopulation capacity to non-uniform local extinction rates. Incorporating stochasticity arising from finite carrying capacities, we obtain a reduced one-dimensional description that reveals universal finite-size scaling laws for extinction times and fluctuations. Extending the approach to multiple competing species, we prove that in homogeneous environments monodominance can be avoided only in a fine-tuned, marginally stable coexistence state, and that the classic metapopulation capacity gives only a necessary but not sufficient condition for persistence. We demonstrate that heterogeneous habitats can support stable coexistence, but only above a critical level of heterogeneity. Finally, we outline how additional ecological processes can be systematically incorporated within the same formalism. Together, these results provide analytical
benchmarks and a general route for constructing spatially explicit ecological theories based on an interpretable underlying mechanistic foundation.
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All authors Davide Bernardi, Alice Doimo, Giorgio Nicoletti, Prajwal Padmanabha, Andrea Rinaldo, Samir Suweis, Sandro Azaele, Amos Maritan
Strongly Correlated Electrons
Three-dimensional spin-orbital liquids
Anna Sandberg, Lukas Rødland and Maria Hermanns
Spin-orbital
liquids provide an exactly solvable route to three-dimensional Z2
quantum spin liquids beyond the original Kitaev setting. Built from higher-dimensional Clifford-
algebra representations,
spin-orbital
Hamiltonians can be realized on both three- and four-coordinated
lattices, giving rise to phases with 3 and 2 itinerant Majorana
flavors, respectively. We demonstrate that these models host a rich set of gapless Majorana metals, characterized, in particular, by topological
Fermi surfaces, nodal lines, and Weyl semimetal phases. We analyze the stability of these structures under physically motivated perturbations and identify generic splitting patterns and topological transitions driven by
symmetry breaking and
flavor mixing. This yields a unified organizing framework for three-dimensional Majorana metals in fractionalized
spin liquids.
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Soft Condensed Matter
Self-assembly of flexible patchy nanoparticles in solution
Guoqing Meng, Liyuan Chen, Sihang Guo et al. (+3 more)
The self-assembly of
polymer grafted nanoparticles is more and more used in the field of functional materials. However, there is still a lack of analysis on the dynamic transformation paths of different self-assembly morphologies, which makes it impossible to achieve further precise regulation and targeted design in experiments and industrial production. In this work the effects of patchy property, grafted chain length, ratio and grafting density on the self-assembly behavior and structure of
polymer grafted flexible patchy nanoparticles are investigated by dissipative particle dynamics simulation method through the construction of coarse-grained model of
polymer grafted ternary nanoparticles. The influence and regulation mechanisms of these factors on the self-assembly structure transformation of flexible patchy nanoparticles are systematically studied, and a variety of structures such as dendritic structure, columnar structure, and
bilayer membrane are obtained. The self-assembly structure of flexible patchy nanoparticles obtained in this work (such as
bilayer membrane structure) provides a potential application basis for designing drug carriers. By precisely regulating the specific structural characteristics of the system, it is possible to achieve efficient loading of drugs and targeted delivery functions, thus significantly improving the bioavailability and effect of drugs.
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All authors Guoqing Meng, Liyuan Chen, Sihang Guo, Junxing Pan, Yingying Wang, Jinjun Zhang
Superconductivity
Spin splitting, Kondo correlation and singlet-doublet quantum phase transition in a superconductor-coupled InSb nanosheet quantum dot
Xingjun Wu, Ji-Yin Wang, Haitian Su et al. (+6 more)
We realize a
superconductor-coupled
quantum dot (QD) in an InSb nanosheet, a 2D platform promising for studies of topological superconductivity. The device consists of a
superconductor-QD-
superconductor junction, where a bottom
bilayer gate defines the QD and allows tuning of its coupling to the superconducting leads. The QD exhibits large $g$-factors and strong
spin-orbit coupling. Transport measurements reveal Coulomb diamond-shaped differential conductance features with even-odd alternating sizes and pronounced conductance lines associated with the superconducting gap, confirming a few-electron,
superconductor-coupled regime. At an odd electron occupation, Kondo signatures emerge, including a zero-bias peak that splits with
magnetic field and is logarithmically suppressed at elevated temperatures. We further observe a doublet-singlet
quantum phase transition, manifested by a clear change of Andreev bound states from crossing to anticrossing as the coupling strength increases. These results underscore the rich physics of InSb nanosheet QDs and their promise for topological
quantum devices.
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All authors Xingjun Wu, Ji-Yin Wang, Haitian Su, Han Gao, Shili Yan, Dong Pan, Jianhua Zhao, Po Zhang, H. Q. Xu
Statistical Mechanics
Sixth order modification of the Cahn-Hilliard equation
P. O. Mchedlov-Petrosyan, L. N. Davydov and O. A. Osmaev
We consider the sixth-order convective-viscous Cahn-Hilliard equation, different from the standard fourth-order Cahn-Hilliard equation due to the modified expression for the thermodynamic potential. In such modified thermodynamic potential the coefficient at the square gradient term is order-parameter-dependent. It also contains the square of the
Laplacian. This results in a sixth-order differential equation and additional nonlinear terms in the equation. We obtained several exact static- and traveling wave solutions and studied the dependence of solutions on the parameters of the system.
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Statistical Mechanics
Fooling the Landauer bound with a demon biased thermal bath
Salambô Dago and Ludovic Bellon
The Landauer principle establishes a fundamental lower bound on the energetic cost of the erasure of a one-bit
memory in thermal
equilibrium. Here, we experimentally demonstrate how this bound can be effectively circumvented by introducing a hysteresis in the feedback-generated virtual potential of a micro-resonator acting as the information bit. By tuning the hysteresis, we engineer a non-
equilibrium steady state with an adjustable effective temperature, enabling erasure processes that consume over 20 percents below the Landauer bound. Our results reveal that the hysteresis acts as an embedded Maxwell demon, exploiting temporal and spatial information to reduce the system's
entropy and the thermodynamic transformation cost. This approach provides a versatile platform for exploring the interplay between feedback, information, and energy in
stochastic systems.
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Mesoscale and Nanoscale Physics
Optically tunable nonlinear mechanical damping in an optomechanical resonator
Hideki Arahari, Motoki Asano, Hiroshi Yamaguchi et al. (+1 more)
We theoretically propose and experimentally demonstrate optically tunable nonlinear mechanical damping in a cavity optomechanical system utilizing a partly resolved sideband regime. Optomechanical coupling provides a delayed nonlinear backaction to the mechanical modes, resulting in nonlinear mechanical damping. This optically induced nonlinear damping is observed in the frequency and time domains, and we show using both theory and experiment that it can be tuned via
laser detuning. Specifically, we observe positive nonlinear damping in the blue-detuned regime and negative nonlinear damping in the red-detuned regime. We also observe optically mediated cross-nonlinear damping between two mechanical modes: the amplitude of one mode modulates the damping of the other. The presented results show a tunable scheme of nonlinear mechanical damping that will be applicable to various non-trivial systems, governed by nonlinear, nonequilibrium, and non-Hermitian phenomena.
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All authors Hideki Arahari, Motoki Asano, Hiroshi Yamaguchi, Hajime Okamoto
Quantum Gases
Emulation of the dynamics of bound electron exposed to strong oscillatory laser field with Bose-Einstein Condensates
Ziheng Ma, Jia Li, Rui Jin et al. (+1 more)
This paper employs a Bose-Einstein condensates to simulate the dynamical response of bound electrons in a strongly oscillating pulsed
laser field. We investigate the excitation dynamics of Bose-Einstein condensates with repulsive interaction confined in a potential well with finite depth and width driven by a strong oscillatory pulse field. By numerically solving the Gross-Pitaevskii equation with Crank-Nicolson method and split operator method, we obtain the time-dependent wavefunction and therefore the
evolution of density distribution in real space and that in momentum space, and the occupation distribution in energy space. It is shown that cold atoms with weak interaction oscillate as a whole body in a finite space when the amplitude of pulse drive is not strong enough. During the
evolution atoms occupy the bound states with larger probability. Increasing the driving strength or atomic interactions promotes the excitation of atoms into continuum states and their
diffusion out of the potential well, leading to complex structures or even interference-like patterns in the momentum distribution. The number of cycles in the pulse envelope plays a crucial role in the dynamical behavior: High-frequency driving can suppress
diffusion and maintain localization. Furthermore, repulsive atomic interactions can enhance high-harmonic generation yields by several orders of magnitude. This study offers a new perspective for
quantum simulations of ultrafast dynamics in strong fields and reveals the regulatory role of interactions in condensates on non-
equilibrium dynamical processes.
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All authors Ziheng Ma, Jia Li, Rui Jin, Yajiang Hao
Statistical Mechanics
Classical Resolution of the Gibbs Paradox from the Equal Probability Principle: An Informational Perspective
Zheng Zhang
The Gibbs paradox is a conventional paradox in classical statistical mechanics, typically resolved by invoking
quantum indistinguishability through the 1/N! correction. In this letter, we present a resolution within classical ensemble theory, which relies solely on the equal probability principle and does not invoke the 1/N! correction. Our resolution can be naturally interpretated from a purely informational perspective, where the Gibbs
entropy is explicitly regarded as the Shannon
entropy, quantifying ignorance rather than disorder. From this informational perspective, we also clarify the connection between information and extractable work in the gas mixing processes. Our work opens a new avenue to reconsider the role of information in statistical mechanics.
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Materials Science
Microscopic Origin of the Ultralow Lattice Thermal Conductivity in Vacancy-Ordered Halide Double Perovskites Cs$_2BX_6$ ($B$ = Zr, Pd, Sn, Te, Hf, and Pt; $X$= Cl, Br, and I)
Lingzhi Cao, Yateng Wang, Zhonghao Xia et al. (+1 more)
Vacancy-ordered halide double perovskites Cs$_2BX_6$ have recently attracted significant
attention due to their intrinsically ultralow
lattice thermal conductivity ($\kappa_{\mathrm{L}}$), which is highly desirable for thermal insulation and thermoelectric applications. In this work, we systematically investigate the anharmonic
lattice dynamics and thermal transport properties of Cs$_2BX_6$ ($B$ = Zr, Pd, Sn, Te, Hf, and Pt; $X$ = Cl, Br, and I) using state-of-the-art first-principles calculations, based on a unified theory of thermal transport for
crystals and glasses. All studied compounds are found to exhibit ultralow $\kappa_{\mathrm{L}}$ below 1.0~W\,m$^{-1}$\,K$^{-1}$ at room temperature and large derivation from the conventional $T^{-1}$ temperature dependence. Our analysis combining with machine-learning approach show that low sound velocities (1100 – 1600~m\,s$^{-1}$), which originates from the intrinsically weak chemical bonding, play a crucial role in suppressing heat transport of the most compounds, instead of the strong scattering of rattling
phonon modes expected from the large void in the structure. Furthermore, the influence of $B$ and $X$-site elements on
phonon dispersion, anharmonicity, and scattering phase space is clarified. Our results provide microscopic insights into the origin of ultralow $\kappa_{\mathrm{L}}$ in Cs$_2BX_6$ and offer guiding principles for the rational design of halide-based materials with tailored thermal transport properties.
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All authors Lingzhi Cao, Yateng Wang, Zhonghao Xia, Jiangang He
Statistical Mechanics
Tensor network dynamical message passing for epidemic models
Cheng Ye, Zi-Song Shen and Pan Zhang
While epidemiological modeling is pivotal for informing public health strategies, a fundamental trade-off limits its predictive fidelity: exact
stochastic simulations are often computationally intractable for large-scale systems, whereas efficient analytical approximations typically fail to account for essential short-range correlations and network loops. Here, we resolve this trade-off by introducing Tensor Network Dynamical Message Passing (TNDMP), a framework grounded in a rigorous property we term Susceptible-Induced Factorization. This theoretical insight reveals that a susceptible node acts as a dynamical decoupler, factorizing the global
evolution operator into localized components. Leveraging this, TNDMP provides a dual-mode algorithmic suite: an exact
algorithm that computes local observables with minimal redundancy on tractable
topologies and a scalable and tunable approximation for complex real-world networks. We demonstrate that widely adopted heuristics, such as Dynamical Message Passing (DMP) and Pair Approximation (PA), are mathematically recoverable as low-order limits of our framework. Numerical validation in synthetic and real-world networks confirms that TNDMP significantly outperforms existing methods to predict epidemic thresholds and steady states, offering a rigorous bridge between the efficiency of message passing and the accuracy of tensor network formalisms.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Local Certification of Many-Body Steady States
Miguel Frías Pérez and Antonio Acín
We present a relaxation-based method to bound expectation values on the steady state of dissipative many-body
quantum systems described by master equations of the Lindblad form. Instead of targeting to represent the entire state, we promote the reduced density
matrices to our variables and enforce the constraints that are imposed on them by consistency with a global steady state. The resulting constraints have the form of a semidefinite program, which allows us to efficiently bound the values a given expectation value can take in the steady state. Our results show fast convergence of the bounds with the size of the reduced density
matrices, giving very competitive predictions for the steady state of several one- and two-dimensional models for an arbitrary number of particles.
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Statistical Mechanics
Inferring Microscopic Explanatory Structures from Observational Constraints via Large Deviations
Akihisa Ichiki
We study how macroscopic observational constraints restrict admissible microscopic explanatory structures when no intrinsic order or dynamics is assumed a priori. Starting from an unordered collection of measurement outcomes, we formulate inference as a constrained large deviation problem, selecting probability assignments that minimize relative
entropy with respect to a reference measure determined solely by the measurement setup. We show that among all microscopic structures compatible with a given macroscopic constraint, those rendering the observation statistically most typical are selected. As an explicit illustration, we demonstrate how ordered microscopic structures can emerge purely from inference under constraint, even when the reference measure is fully permutation symmetric. Order is thus not assumed but inferred, serving here only as an illustrative example of a broader class of relational explanatory hypotheses constrained by observation.
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Statistical Mechanics
Relativity of Observation: Operational Intensive Variables in Nonequilibrium Thermodynamics
Akihisa Ichiki
We formulate nonequilibrium thermodynamics in which intensive variables acquire operational meaning through measurement protocols consistent with local reciprocity. Using physical
equilibrium as a reference, conjugate observables are constructed by continuously adjusting devices along the local tangent space of the statistical
manifold. In this relativity of observation, Onsager reciprocity holds locally, allowing inference-based Lagrange multipliers to be directly measured. This provides a systematic method to extend operational definitions of intensive variables to nonequilibrium states, highlighting their context-dependent nature and offering a concrete experimental strategy.
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