Strongly Correlated Electrons
Systematic study of multi-magnon binding energies in the FM-AFM $J_1$-$J_2$ chain
Satoshi Nishimoto
We present a systematic study of multi-
magnon bound states (MBSs) in the
spin-$\tfrac{1}{2}$ FM-AFM $J_1$-$J_2$ chain under
magnetic fields using the density-
matrix renormalization group method. As a quantitative measure of stability, we compute the
magnon binding energy $E_{\rm b}(M,p)$ for bound clusters of size $p$ over wide ranges of the frustration ratio $J_2/|J_1|$ and the normalized magnetization $M/M_{\rm s}$. Near saturation, we
benchmark our data against the analytic two-
magnon result and map out a clear hierarchy of $p$-
magnon states, whose phase boundaries follow an empirical scaling $J_{2,{\rm c}}(p;p\!+\!1)/|J_1|\!\approx\!0.34\,p^{-2.3}$ for large $p$. We further quantify the relation between the most stable $p$ and the zero-field pitch angle $\theta$, verifying the conjectured inequality $1/p>\theta/\pi>1/(p+1)$ up to $p \lesssim 9$. The binding energy shows pronounced suppression as $J_2/|J_1|\!\to\!1/4^+$ and, for some frustration values, attains a maximum below full saturation, indicating that partial depolarization enhances bound-
magnon mobility. Close to the FM instability, $E_{\rm b}(M_{\rm s},p)$ exhibits an empirical power-law vanishing consistent with a
quantum-Lifshitz scenario. Our results provide a comprehensive, experimentally relevant map of MBS stability across field and frustration, offering concrete guidance for inelastic probes in quasi-one-dimensional magnets.
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Soft Condensed Matter
Aging in the Flow Dynamics of Dense Suspensions of Contactless Microparticles
Jesús Fernández, Loïc Vanel and Antoine Bérut
This study demonstrates that the free-surface flow dynamics of dense piles of contactless silica microparticles depend on the resting period prior to flow. Microfluidic rotating drum experiments reveal that longer resting times lead to delayed flow onsets and reduced flow velocities, both evolving logarithmically with the resting time. These aging-like effects are more pronounced for thermally driven creep flows in piles with initial tilting angle below the athermal angle of repose, in contrast to piles initially tilted above this repose angle, where
gravity-driven flows tend to gradually erase aging effects. Moreover, we show that the packing fraction does not change during the resting period, and that aging occurs in both monodisperse and polydisperse piles, indicating that crystallization is not required for the time-dependent behavior to appear. Remarkably, vigorous agitation that re-disperses the particles fully restores the piles to their initial state, demonstrating that the observed effects are not due to sample degradation. These findings evidence a form of aging in quiescent suspensions intermediate between colloidal and granular media, where thermal fluctuations, still significant relative to particle weight, progressively stabilize the system, making it more resistant to flow and deformation.
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Mesoscale and Nanoscale Physics
Anyonic time exchange in hierarchical Hall states: emergent Luttinger scaling and cross-correlations at finite temperature
Aleksander Latyshev and Ines Safi
We address hierarchical fractional
quantum Hall edges coupled by a spatially local
quantum point contact within the Unified Nonequilibrium Perturbative (UNEP) framework. Without assuming a Tomonaga-Luttinger
liquid (TLL) tunneling correlator, we impose a local anyonic time-exchange (ATE) constraint with phase $\bar{\theta}$, yielding a nonequilibrium fluctuation-dissipation integral equation relating DC tunneling current and noise. For thermal initial states, detailed balance closes this equation for the current. Using the Wiener-
Hopf method, we find a unique physical solution of local TLL form, with scaling dimension $\delta$ determined by $\bar{\theta}=\pi\delta\pmod{\pi}$, emerging from the solution rather than being imposed via a TLL correlator. By contrast, ATE and inversion
symmetry alone fix the exchange monodromy but not the full transport dynamics. We then study the "anyon
collider" beyond Laughlin states at finite temperatures. Detailed balance is broken and noise becomes super-Poissonian, but the relation between nonequilibrium and
equilibrium correlators determines current and noise. The output cross-correlation and balanced generalized Fano factor depend on both $\delta$ and statistical phase $\theta$, identical to $\bar{\theta}$ for co-propagating modes with short-range interactions. A temperature-dependent current scale separates the zero-temperature asymptotic regime from the low-current regime, where the balanced Fano factor saturates to a function of $\theta$ and $\delta$ distinct from its zero-temperature value. This latter regime is particularly relevant to “anyon
collider” experiments. These complementary regimes constrain the statistical phase and scaling dimension, subject to the
symmetry $\delta\mapsto1-\delta$ at fixed $\theta$. For independent statistical phase and scaling dimension, the thermal crossover can reverse the sign of output cross-correlations.
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Strongly Correlated Electrons
Monte Carlo Sampling for Wave Functions Requiring (Anti)Symmetrization
Koyena Bose, Steven H. Simon and Ajit C. Balram
Many strongly correlated states, such as those arising in the fractional
quantum Hall effect and
spin liquids, are described by wave functions obtained by dividing particles into multiple clusters, constructing a readily evaluable wave function in each cluster, and (anti)symmetrizing across these clusters. We introduce a method to compute quantities such as energies and correlators, using Monte Carlo simulations for these states. Our framework overcomes the factorial scaling of explicit (anti)symmetrization, allowing for studies of systems beyond the reach of exact diagonalization.
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Superconductivity
Low-temperature electron dephasing rates indicate magnetic disorder in superconducting TiN films
A. I. Lomakin, E. M. Baeva, N. A. Titova et al. (+8 more)
We investigate electron transport and phase-breaking processes in thin titanium nitride (TiN) films of epitaxial quality. Previous studies show that a minute surface
magnetic disorder significantly reduces the critical temperature ($T_\mathrm{c}$) and broadens the superconducting transition as the film thickness and device size decrease. We measure electron dephasing rates via magnetoresistance from $T_\mathrm{c}$ to $\sim 4T_\mathrm{c}$ in various-thickness TiN films. Electron dephasing occurs on the picosecond timescale and is nearly independent of temperature, differing from the expected inelastic scattering due to the electron-
phonon and electron-electron interactions near $T_\mathrm{c}$, which occur over a nanosecond timescale. We propose
spin-flip scattering as a possible additional phase-breaking mechanism. The significant increase in the dephasing rate for the thinnest film indicates that
magnetic disorder resides near the surface of naturally oxidized films. Our research suggests that
magnetic disorder may be a significant contributor to RF dissipation in superconducting devices based on TiN.
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All authors A. I. Lomakin, E. M. Baeva, N. A. Titova, A. V. Semenov, A. V. Lubenchenko, M. A. Kirsanova, S. A. Evlashin, S. Saha, S. Bogdanov, A. I. Kolbatova, G. N. Goltsman
Disordered Systems and Neural Networks
Local Density of States as a Probe of Multifractality in Quasiperiodic Moiré Materials
Ricardo Oliveira, Nicolau Sobrosa, Pedro Ribeiro et al. (+2 more)
Quasiperiodic moiré materials provide a new platform for realizing critical electronic states, yet a direct and experimentally practical method to characterize this criticality has been lacking. We show that a multifractal analysis of the local density of states (LDOS), accessible via scanning tunneling microscopy, offers an unambiguous signature of criticality from a single experimental sample. Applying this approach to a one-dimensional quasiperiodic model, a stringent test case due to its fractal energy spectrum, we find a clear distinction between the broad singularity spectra $f\left(\alpha\right)$ of critical states and the point-like spectra of extended states. We further demonstrate that these multifractal signatures remain robust over a wide range of energy broadenings relevant to experiments. Our results establish a model-independent, experimentally feasible framework for identifying and probing multifractality in the growing family of quasiperiodic and moiré materials.
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All authors Ricardo Oliveira, Nicolau Sobrosa, Pedro Ribeiro, Bruno Amorim, Eduardo V. Castro
Soft Condensed Matter · Cross-listed from physics.bio-ph
Dynamic principles of concentration buffering through liquid-liquid phase separation
Logan de Monchaux-Irons, T-Y Dora Tang, Christoph A. Weber et al. (+1 more)
Living systems must maintain robust biochemical function despite fluctuations that span a wide range of timescales. Biomolecular condensates formed by
liquid-
liquid phase separation (LLPS) have been shown to buffer concentration fluctuations, but the principles governing their dynamic regulation remain unclear. We address this by probing the response of LLPS to oscillatory perturbations that mimic fluctuations across different timescales, establishing the first systematic frequency-domain analysis of concentration buffering by condensates. We find that condensates act as frequency-selective filters: the perturbed dilute phase behaves as a high-pass filter, while the dense phase attenuates both low- and high-frequency perturbations. We establish quantitative links between LLPS parameters including interaction strength, droplet size, and molecular diffusivity, and the timescale range over which condensates effectively buffer concentration fluctuations. These findings establish the fundamental dynamical limits of concentration buffering by LLPS, with implications for how
cells may use LLPS to adapt to fluctuating environments and for the design of synthetic condensates with programmable control properties.
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All authors Logan de Monchaux-Irons, T-Y Dora Tang, Christoph A. Weber, Thomas C.T. Michaels
Statistical Mechanics · Cross-listed from math.PR
Beneath the kinetic interpretation of noise
Carlos Escudero and Helder Rojas
Diffusion theory establishes a fundamental connection between
stochastic differential equations and partial differential equations. The solution of a partial differential equation known as the Fokker-Planck equation describes the probability density of the
stochastic process that solves a corresponding
stochastic differential equation. The kinetic interpretation of noise refers to a prospective notion of
stochastic integration that would connect a
stochastic differential equation with a Fokker-Planck equation consistent with the Fick law of
diffusion, without introducing correction terms in the drift. This work is devoted to identifying the precise conditions under which such a correspondence can occur. One of these conditions is a structural constraint on the
diffusion tensor, which severely restricts its possible form and thereby renders the kinetic interpretation of noise a non-generic situation. This point is illustrated through a series of examples. Furthermore, the analysis raises additional questions, including the possibility of defining a
stochastic integral inspired by numerical
algorithms, the behavior of
stochastic transport equations in heterogeneous media, and the development of alternative models for anomalous
diffusion. All these topics are addressed using
stochastic analytical tools similar to those employed to study the main problem: the existence of the kinetic interpretation of noise.
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Mesoscale and Nanoscale Physics
Quantifying robustness and locality of Majorana bound states in interacting systems
William Samuelson, Juan Daniel Torres Luna, Sebastian Miles et al. (+4 more)
Protecting
qubits from perturbations is a central challenge in
quantum computing. Topological
superconductors with separated Majorana bound states (MBSs) provide a strong form of protection that only depends on the locality of perturbations. While the link between MBS separation, robust degeneracy, and protected braiding is well understood in non-interacting systems, recent experimental progress in short
quantum-dot-based Kitaev chains highlights the need to establish these connections rigorously for interacting systems. We do this by defining MBSs from many-body ground states and show how their locality constrains their coupling to an environment. This, in turn, quantifies the protection of the energy degeneracy and the feasibility of non-abelian braiding.
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All authors William Samuelson, Juan Daniel Torres Luna, Sebastian Miles, A. Mert Bozkurt, Martin Leijnse, Michael Wimmer, Viktor Svensson
Materials Science
The effects of high-temperature ion-irradiation on early-stage grain boundaries serrations formation in Ni-based alloys
M. Frelek-Kozak, K. Mulewska, M. Wilczopolska et al. (+5 more)
Nickel based superalloys display outstanding properties such as excellent creep strength, remarkable fracture toughness parameters, and corrosion resistance. For this reason, Ni based materials are considered as materials dedicated to the IV generation of
nuclear reactors. Although these materials seem promising candidates, their radiation resistance and impact of radiation damage on the deformation mechanism are still not fully understood. In this work, two commercially available nickel based
alloys, Hastelloy X and Haynes 230, were investigated. Structural and mechanical properties have been described by means of SEM and EBSD, TEM, and nanoindentation tests. Radiation damage has been performed by Ar ion with energy 320keV with two doses up to 12dpa. Obtained results have revealed a hardening effect for both levels of damage. However, more intensive effects were observed for Hastelloy X. Moreover, a significant change in precipitates morphology in Hastelloy X has been observed. It has been proposed that structural differences between both
alloys determine the type of occurring radiation induced processes. Excess energy deposited into materials structure during ion irradiation can lower the temperature of nucleation of high temperature phases, which initiates the formation of grain boundary serrations.
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All authors M. Frelek-Kozak, K. Mulewska, M. Wilczopolska, D. Kalita, W. Chrominski, A. Zaborowska, L. Kurpaska, J. Jagielski
Mesoscale and Nanoscale Physics
Sub-10 nm Quantification of Spin and Orbital Magnetic Moment Across the Metamagnetic Phase Transition in FeRh Using EMCD
Jan Hajduček, Veronica Leccese, Ján Rusz et al. (+9 more)
Electron
magnetic circular dichroism (EMCD) in transmission electron microscopy (TEM) enables element-specific measurement of
spin and orbital
magnetic moments, analogous to X-ray
magnetic circular dichroism (XMCD). While the EMCD technique offers unmatched spatial resolution, its quantitative accuracy remains under scrutiny, particularly in beam-splitter geometries with convergent probes. Here, we systematically evaluate the limits of quantitative EMCD analysis using the first-order magnetostructural transition in the functional phase-change material FeRh as a tunable
magnetic reference. Unlike previous EMCD studies primarily focused on elemental ferromagnets such as Fe, we demonstrate its applicability to a correlated material exhibiting coupled structural and
magnetic order. We demonstrate that the extracted orbital-to-
spin moment ratio ($m_\text{L}/m_\text{S}$) remains consistent with XMCD
benchmarks for TEM probes down to approximately 6 nm, thereby establishing the validity range for reliable quantification. For nm-sized probes with higher convergence angles, we observe an enhanced $m_\text{L}/m_\text{S}$, which we attribute to a combination of instrumental factors and sensitivity to nanoscale heterogeneity within the probed volume. Our results confirm that EMCD provides quantitative agreement with macroscale techniques under suitable conditions, while uniquely enabling spatially confined measurements of local
magnetic moments in functional
magnetic materials, and allowing the study of interfacial, defect-mediated, or phase-separated magnetism that is inaccessible to
photon-based methods.
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All authors Jan Hajduček, Veronica Leccese, Ján Rusz, Jon Ander Arregi, Alexey Sapozhnik, Jáchym Štindl, Francesco Barantani, Paolo Cattaneo, Antoine Andrieux, Vojtěch Uhlíř, Fabrizio Carbone, Thomas LaGrange
Statistical Mechanics
Asymptotic versus mesoscopic spectral dimensions in networks and inhomogeneous structures
Lorenzo Grimaldi, Pablo Villegas, Alessandro Vezzani et al. (+3 more)
"Every object that biology studies is a system of systems." (François Jacob, 1974). Most networks feature intricate architectures originating from tinkering, a repetitive use of existing components where structures are not invented but reshaped. Linking the properties of primitive components to the emergent behavior of composite networks remains a key open challenge. Here, we show that modular compositions generically decouple the spectral and Fiedler dimensions, so that networks with identical thermodynamic exponents can exhibit parametrically different equilibration dynamics.
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All authors Lorenzo Grimaldi, Pablo Villegas, Alessandro Vezzani, Raffaella Burioni, Davide Cassi, Andrea Gabrielli
Materials Science
Predicting the 3D microstructure of SOFC anodes from 2D SEM images using stochastic microstructure modeling and CNNs
Léon F. Schröder, Sabrina Weber, Lukas Fuchs et al. (+2 more)
The 3D microstructure of solid
oxide fuel
cell anodes significantly influences their electrochemical performance, but conventional methods for acquiring high-resolution microstructural 3D data such as focused ion beam scanning electron microscopy (FIB-SEM) are costly in both time and resources. In contrast, obtaining 2D images, such as from scanning electron microscopy (SEM), is more accessible, though typically providing insufficient information to accurately characterize the 3D microstructure. To address this challenge, we propose a novel approach that predicts the 3D microstructure from 2D SEM images. The presented method utilizes a low-parametric 3D model from
stochastic geometry to generate a large number of virtual 3D microstructures and employs a physics-based SEM simulation tool to obtain the corresponding 2D SEM images. By systematically varying the underlying model parameters, a large
dataset can be generated to train convolutional neural networks (CNNs). By doing so, we can statistically reconstruct the 3D microstructure from 2D SEM images by drawing realizations from the
stochastic 3D model using the predicted model parameters. In addition, we conducted an error analysis on key geometrical descriptors to quantitatively evaluate the accuracy and reliability of this stereological prediction tool.
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All authors Léon F. Schröder, Sabrina Weber, Lukas Fuchs, Volker Schmidt, Benedikt Prifling
Soft Condensed Matter
Transitions between liquid crystalline phases investigated by dielectric and infra-red spectroscopies
Aleksandra Deptuch, Natalia Osiecka-Drewniak, Anna Paliga et al. (+5 more)
The
liquid crystalline 11OS5 compound, forming the nematic phase and a few smectic phases, is investigated by broadband dielectric spectroscopy and infra-red spectroscopy. The dielectric relaxation times, ionic conductivity, and positions of infra-red absorption bands corresponding to selected intra-molecular vibrations are determined as a function of temperature in the range from isotropic
liquid to a
crystal phase. The correlation coefficient
matrix and k-means cluster analysis of infra-red spectra are tested for detection of phase transitions. The density-functional theory calculations are carried out for interpretation of experimental infra-red spectra. The performance of various basis sets and exchange-correlation functionals is compared, including both agreement of scaled calculated band positions with experimental values and computational time. The inter-molecular interactions in the
crystal phase are inferred from the experimental IR spectra and density-functional theory calculations for dimers in head-to-head and head-to-tail configurations. The experimental temperature dependence of the C=O stretching band suggests that the head-to-tail configuration in a
crystal phase is more likely. A significant slowing down of the flip-flop relaxation process is observed at the transition between the smectic C and hexagonal smectic X phases.
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All authors Aleksandra Deptuch, Natalia Osiecka-Drewniak, Anna Paliga, Natalia Górska, Anna Drzewicz, Katarzyna Chat, Mirosława D. Ossowska-Chruściel, Janusz Chruściel
Strongly Correlated Electrons
Metallic island array as synthetic quantum matter: fractionalized entropy and thermal transport
Nitay Hurvitz, Gleb Finkelstein and Eran Sela
The surprisingly rich physics of a single Coulomb-blockaded metallic island, when coupled to
quantum Hall edge channels, is now well established – giving rise to charge fractionalization and multi-channel
quantum impurity behavior. Here, we show that qualitatively new physics emerges in arrays of such elements. We consider a 1D chain of $N$ metallic islands, focusing on thermodynamic signatures such as quantized
entropy and anomalous thermal conductance. Universal and robust behavior emerges for energy scales smaller than the charging energy of the islands. In particular, we demonstrate that for the bulk filling factor of $\nu=1$, the islands could support a finite heat flow without temperature difference between them. Upon pinching the array with a
quantum point contact, we predict an
entropy change that scales with the number of islands as $\Delta S = \frac{1}{2}k_B \log (N+1)$, which can be measured using charge detection. This fractional
entropy suggests the emergence of a novel type of excitations in the array.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Phenomenological Noise Models and Optimal Thresholds of the 3D Toric Code
Ji-Ze Xu, Yin Zhong, Miguel A. Martin-Delgado et al. (+2 more)
Three-dimensional (3D) topological codes offer the advantage of supporting fault-tolerant implementations of non-Clifford gates, yet their performance against realistic noise remains largely unexplored. In this work, we focus on the paradigmatic 3D toric code and investigate its fault-tolerance thresholds in the presence of both Pauli and measurement errors. Two randomly coupled
lattice gauge models that describe the code's correctability are derived, including a random 2-form $\mathbb{Z}_2$ gauge theory. By exploiting a generalized duality technique, we show that the 3D toric code exhibits optimal thresholds of $p^{X,M}_{th} \approx 11\%$ and $p^{Z,M}_{th} \approx 2\%$ against bit-flip and phase-flip errors, respectively. These threshold values show modest reductions compared to the case of perfect measurements, establishing the robustness of the 3D toric code against measurement errors. Our results constitute a substantial advance towards assessing the practical performance of 3D topological codes. This contribution is timely and in high demand, as rapid hardware advancements are bringing complex codes into experimental reach. Moreover, our work highlights the interdisciplinary nature of fault-tolerant
quantum computation and holds significant interest for
quantum information science, high-energy physics, and condensed matter physics.
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All authors Ji-Ze Xu, Yin Zhong, Miguel A. Martin-Delgado, Hao Song, Ke Liu
Statistical Mechanics · Cross-listed from math.PR
Long time behaviour of one facilitated kinetically constrained models: results and open problems
Fabio Martinelli, Assaf Shapira and Cristina Toninelli
Kinetically constrained models (KCMs) are interacting particle systems introduced in the '80s by physicists to have accessible
stochastic models with glassy-type dynamics. The key mechanism behind the complex
evolution of these otherwise simple models is the so-called dynamical facilitation, a feature embedded into the models via appropriate kinetic constraints. KCMs are reversible with respect to a Bernoulli product measure, and the analysis of their stationary
evolution has witnessed significant progress in the last decade. Unfortunately, in the interesting regime when the
equilibrium density of the facilitating vertices is small, many fundamental questions concerning the non-stationary
evolution of even the simplest models remain unsolved. In this paper, we discuss some of these questions, along with partial new results and
conjectures, for the one facilitated model and its variants, as well as for the biased annihilating branching process.
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Materials Science
Ultralow-Cost magnetocaloric compound for Cryogenic Cooling
Wei Liu, Benjamin Theisel, Yulia Klunnikova et al. (+2 more)
Cost-effective materials are essential for large-scale deployment. The emerging magnetocaloric hydrogen liquefaction technology could transform the
liquid hydrogen industry due to its potential in achieving higher efficiency. Most studies of the cryogenic magnetocaloric effect (MCE) have focused on resource-critical rare-earth-based compounds. Here we report on an ionic magnetocaloric compound FeCl$_2$ which is based on ultralow-cost elements, as a candidate working material for hydrogen liquefaction. FeCl$_2$ shows both inverse and conventional MCE. From 0 to 1.5 T, the inverse effect yields a positive
magnetic entropy change ($\Delta S_T$) of about 5 J/kg/K near 20 K, then declines toward zero at higher fields. In contrast, the conventional (negative) response strengthens with field. The $\Delta S_T$ reaches 18.6 J/kg/K near 20 K in
magnetic fields of 5 T. This value exceeds most light rare-earth-based compounds and approaches that of heavy rare-earth-based compounds. In
magnetic fields of 5 T, the adiabatic temperature change reaches about 3.6 K. The large $\Delta S_T$, along with the low cost of the elements in FeCl$_2$, are prerequisites for inexpensive industrial-scale production, giving the prospect of a practical magnetocaloric candidate for hydrogen liquefaction in the 20 $\sim$ 77 K temperature window.
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All authors Wei Liu, Benjamin Theisel, Yulia Klunnikova, Konstantin Skokov, Oliver Gutfleisch
Materials Science
Vacancy diffusion on a brominated Si(100) surface: Critical effect of the dangling bond charge state
T. V. Pavlova and V. M. Shevlyuga
Silicon dangling bonds (DBs) on an adsorbate-covered Si(100) surface can be created in a scanning tunneling microscope (STM) with high precision required for a number of applications. However, vacancies containing DBs can diffuse, disrupting precisely created structures. In this work, we study the
diffusion of Br vacancies on a Si(100)-2$\times$1-Br surface in an STM under typical imaging conditions. In agreement with previous work, Br vacancies diffuse at a positive sample bias voltage. Here, we demonstrated that only vacancies containing a positively charged DB hop across the two atoms of a single Si dimer, while vacancies containing neutral and negatively charged DBs do not. Calculations based on the density functional theory confirmed that positively charged Br (and Cl) vacancies have a minimum activation barrier. We propose that
diffusion operates by both one-electron and two-electron mechanisms depending on the applied voltage. Our results show that the DB charge has a critical effect on the vacancy
diffusion. This effect should be taken into account when imaging surface structures with charged DBs, as well as when studying the
diffusion of other atoms and molecules on the Si(100) surface with vacancies in an adsorbate layer.
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Materials Science
PBr3 Adsorption and Dissociation on the Si(100) Surface
Vladimir M. Shevlyuga, Yulia A. Vorontsova and Tatiana V. Pavlova
The adsorption of PBr3 on the Si(100)-2$\times$1 surface was studied by scanning tunneling microscopy (STM) and density functional theory (DFT). The PBr3 molecule completely dissociates on the Si(100) surface at room temperature into P and Br atoms. In most cases, the dissociated molecule was observed in STM on three neighboring Si dimers. DFT calculations confirm that the PBr3 molecule can completely dissociate at room temperature. After annealing the sample to 400$^{\circ}$C, phosphorus is incorporated into silicon, as evidenced by the Si atoms ejected to the surface. These findings are useful for the insertion of individual phosphorus atoms into silicon by PBr3 adsorption through a halogen mask.
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Statistical Mechanics · Cross-listed from hep-th
Thermodynamics and statistical mechanical ensembles of black holes and self-gravitating matter
Tiago V. Fernandes
Black holes exist all over our Universe, possessing a very wide range of masses. At the moment, they serve as a probe to test general relativity at astrophysical scales, but in the future they may also give us information about
gravity at the microscale. Black holes seem to have thermodynamic properties, such as the Bekenstein-Hawking
entropy, which are important when considering black holes with size of a few centimeters or smaller. Since
entropy in statistical mechanics is related to the number of microstates of a system, several questions arise: what gives rise to the black hole
entropy? Can it be explained by a
quantum description of
gravity? In order to further study these questions, the connection between thermodynamics and
gravity must be explored at the microscale. In this doctoral thesis, we aim to understand this connection using two descrip-tions that yield the thermodynamics of curved spacetimes. We start by imposing the first law of thermodynamics to a charged self-gravitating matter thin shell in higher dimensions and choose equations of state which allow the study of the black hole limit and the recovery of black hole thermodynamics. Furthermore, we use the Euclidean path integral approach to
quantum gravity to construct statistical ensembles of black hole spacetimes and self-gravitating matter, in order to study semiclassically the phase transitions between hot matter and black holes. We show the power of the formalism in obtaining the thermodynamic properties of curved spacetimes. Namely, we study the canonical and grand canonical ensemble of charged black holes inside a cavity, which may have a finite or infinite radius. We construct ensembles of a self-gravitating matter thin shell, both in anti-de Sitter and in asymptotically flat spaces, in order to understand the thermodynamic features of the shell and the possible phase transitions to black hole configurations.
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Mesoscale and Nanoscale Physics
Thermoelectric properties of interacting double quantum dots
Nahual Sobrino
We investigate the thermoelectric transport properties of an interacting parallel double
quantum dot in the Coulomb-blockade regime. Building on an analytical solution based on an equation-of-motion technique, we extend the formalism for the asymmetrically coupled situation and provide compact closed-form expressions for steady-state currents together with the differential conductance, Seebeck coefficient, and thermal conductance. We determine the operating points that maximize efficiency and output power of the system, clarifying their relation to standard near-
equilibrium ZT expressions. We further study the thermal rectification in both the open- and closed-
circuit configurations and derive an expression for the open-
circuit case. Interaction-induced resonances are understood in terms of the poles of the resulting Green's function, generating gate and bias dependent regions of enhanced efficiency at finite power, negative differential thermal conductance, and finite thermal rectification.
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Materials Science
Unlock Anionic Behavior of Calcium Through Pressure Engineering
Yang Lv, Junwei Li, Jianfu Li et al. (+6 more)
An isolated calcium (Ca) atom has empty d-orbitals under ambient conditions. However, s-d band hybridization has been observed in both elemental Ca and compounds by manipulating thermodynamic conditions. Here, we reveal that the Ca 3d-band can even capture electrons from halogen atoms under pressure, exhibiting anionic behaviors in iodides. We predict a CsCl-type monovalent CaI at above 50 GPa by employing first-principles structural searching and successfully identified the phase at 84 GPa using in situ X-ray diffraction. We further reveal that, due to the effect of orbital broadening, unusual charge transfer from the 5p orbitals of I to the 3d orbitals of Ca in CaI, gradually reverses the ionicity of Ca and becomes the anionic ICa at 485 GPa. Multivalent Ca stabilizes a set of metallic iodides with eight- to ten-fold iodine hyper-coordination. Our findings demonstrate that the valence states of Ca can vary from negative to +2, suggesting much greater complexity of Ca chemistry under ultrahigh pressures.
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All authors Yang Lv, Junwei Li, Jianfu Li, Yong Liu, Jianan Yuan, 1 Jiani Lin, Saori Kawaguchi-Imada, Qingyang Hu, Xiaoli Wang
Soft Condensed Matter
Polymorphic self-poisoning in poly(lactic acid): a new phenomenon in polymer crystallization
Shu-Gui Yang, Xiang-bing Zeng, Feng Liu et al. (+1 more)
Self-poisoning (SP) is ubiquitous in
polymer crystallization, but has so far manifested itself visibly only as minima in growth rate vs. temperature in either monodisperse systems where e.g. unstable folded chains obstruct crystallization of stable extended chains, or in periodically segmented chains where unstable stems with n-1 segments disturb deposition of stable stems with n segments. Here we report a new type of self-poisoning found in poly(lactic acid) (PLA), where a less stable
crystal form (alpha') disturbs growth of the stable form (alpha). While alpha requires strict up-down order of the polar chains, alpha' does not, hence is kinetically favoured. Unexpectedly, below the temperature of the growth rate minimum the lamellar thickness increases rather than drops, as in all other reported cases of
polymer crystallization with decreasing temperature. A growth rate equation model is developed, giving good match with experiments, but revealing an unexpectedly low fold surface free energy of alpha' form. Due to SP of alpha, most practical fast-cooling processing gives the low-modulus alpha'-form grown close to Tg, explaining generally poor mechanical properties of the bio-friendly PLA.
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All authors Shu-Gui Yang, Xiang-bing Zeng, Feng Liu, Goran Ungar
Materials Science · Cross-listed from physics.comp-ph
ComProScanner: A multi-agent based framework for composition-property structured data extraction from scientific literature
Aritra Roy, Enrico Grisan, John Buckeridge et al. (+1 more)
Since the advent of various pre-trained large
language models, extracting structured knowledge from scientific text has experienced a revolutionary change compared with traditional machine learning or natural
language processing techniques. Despite these advances, accessible automated tools that allow users to construct, validate, and visualise
datasets from scientific literature extraction remain scarce. We therefore developed ComProScanner, an autonomous multi-
agent platform that facilitates the extraction, validation, classification, and visualisation of machine-readable chemical compositions and properties, integrated with synthesis data from journal articles for comprehensive database creation. We evaluated our framework using 100 journal articles against 10 different LLMs, including both open-source and proprietary models, to extract highly complex compositions associated with ceramic piezoelectric materials and corresponding piezoelectric strain coefficients (d33), motivated by the lack of a large
dataset for such materials. DeepSeek-V3-0324 outperformed all models with a significant overall accuracy of 0.82. This framework provides a simple, user-friendly, readily-usable package for extracting highly complex experimental data buried in the literature to build machine learning or deep learning
datasets.
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All authors Aritra Roy, Enrico Grisan, John Buckeridge, Chiara Gattinoni
Statistical Mechanics
Predictive Indicator of Critical Point in Equilibrium and Nonequilibrium Magnetic Systems
Tianyi Zhang, Caihua Wan and Xiufeng Han
Determining critical points of phase transitions from partial data is essential to avoid abrupt system collapses and reducing experimental or computational costs. However, the complex physical systems and phase transition phenomena have long hindered the development of unified approaches applicable to both
equilibrium and nonequilibrium phase transitions. In this work, we propose predictive indicators to determine critical points in
equilibrium and nonequilibrium
magnetic systems based on frequency-dependent response function. For
equilibrium phase transition, such as magnetization switching under
magnetic field, the static magnetization response function to a perturbing
magnetic field diverges at the critical field, serving as a noise-resilient predictive indicator that also reflects the transition order and critical exponents. In contrast, for nonequilibrium phase transition, such as magnetization switching driven by
spin-transfer torque, static response fails to signal criticality. Instead, the dynamic response at
ferromagnetic resonance frequency diverges at the critical point, which is also robust against thermal noise. We further demonstrate that these static and dynamic indicators can be unified in the frame of first-order linear differential systems, offering a generalizable strategy for predicting criticality in both
equilibrium and nonequilibrium transitions.
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Statistical Mechanics
Self-diffusion in confined systems
Manuel Mayo, María Isabel García de Soria, Pablo Maynar et al. (+1 more)
The self-
diffusion process of a hard sphere fluid confined by two parallel plates separated by a distance on the order of the particle diameter is studied. The starting point is a closed kinetic equation for the distribution function that takes into account the effects of the confinement and that is valid in the low-density limit. From it, the Boltzmann-Lorentz equation that describes the dynamics of some tagged particles when the whole system is in
equilibrium is derived. An equation that describes the
diffusion in the directions parallel to the walls is deduced by applying the Zwanzig-Mori projection technique to the Boltzmann-Lorentz equation, obtaining an explicit expression for the self-
diffusion coefficient that depends on the height of the system. A very good agreement between its theoretical prediction and Molecular Dynamics simulation results is obtained for the whole range of heights.
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All authors Manuel Mayo, María Isabel García de Soria, Pablo Maynar, José Javier Brey
Quantum Gases · Cross-listed from nucl-th
Data-driven exploration of the neutron $^3\text{P}_2$ pairing gap using Cassiopeia A neutron star observational data: Direct $\chi^2$ minimization
Yoonhak Nam and Kazuyuki Sekizawa
The rapid cooling observed in the Cassiopeia~A
neutron star (Cas~A NS) is one of the most stringent tests for
neutron-
star cooling theory. While Cooper-pair breaking and formation (PBF)
neutrino emission is a leading candidate, uncertainties remain regarding the PBF efficiency factor $q$ and the
neutron ${}^{3}\mathrm{P}_{2}$ pairing gap. This work explores in a data-driven manner how the optimized gap shape responds to variations of the PBF emissivity parameter $q$ within a fixed cooling setup. We introduce a novel gap parametrization, in which each parameter carries direct physical meaning and controls the gap amplitude, peak location, width, and asymmetry. Using a Fortran-based cooling code and the BSk24 equation of state, we perform parameter-space exploration guided by the Cas~A NS data. Global optimization is carried out with Optuna's tree-structured Parzen
estimator, followed by local refinement using the Nelder–Mead method. The optimized solutions yield physically reasonable gaps with peak amplitudes $\Delta_{\max}\approx0.5$–$0.6~\mathrm{MeV}$. Although the multi-objective formulation explores the parameter space more broadly, the single-objective $\chi^{2}$-only optimization achieves the lowest $\chi^{2}$. For $M_{\mathrm{NS}}=1.4\,M_{\odot}$, increasing $q$ drives the optimized gap and critical-temperature profiles toward smoother and more localized shapes, improving consistency with the observed trend. Models with $q\gtrsim0.4$ reproduce the decline rate within the $1\sigma$ confidence interval, whereas the baseline case $q\simeq0.19$ lies near the $3\sigma$ level. Our results suggest larger effective PBF emissivities than the baseline estimate, although robust constraints on $q$ require future
Bayesian inference including uncertainties in mass, envelope composition, equation of state, pairing microphysics, and age offset. (Shortened due to the arXiv abstract length limit.)
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Strongly Correlated Electrons
Critical fluctuations and conserved dynamics in a strange ferromagnetic metal
Jin Zhan, Yongjun Zhang, Jiawen Zhang et al. (+9 more)
The origin of the strange metallic behavior observed in a wide range of
quantum materials is an open challenge to condensed matter physics. Historically, strange metals were uniquely associated with
antiferromagnetic quantum critical points (QCPs), but a new generation of materials reveals their association with uniform order parameters, such as ferromagnetism, valley or nematic order, suggesting a deeper common denominator. At a QCP, order parameter fluctuations are characterized by the dynamical critical exponent $z$, which quantifies the space-time scaling asymmetry. Here, we report the observation of a divergence in the Grüneisen ratio at the QCP of the strange-metal ferromagnet CeRh$_6$Ge$_4$ with a dynamical critical exponent $z=3$, signaling that the underlying
quantum singularity involves a conserved degree of freedom. Yet the magnetization of this easy-plane ferromagnet is not conserved. We argue that the $z=3$ strange criticality requires a description beyond the Landau paradigm, proposing a link with the gauge modes of the small-to-large
Fermi surface transition and the associated gauge charge of the delocalizing heavy electrons.
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All authors Jin Zhan, Yongjun Zhang, Jiawen Zhang, Yu Liu, Zhiyong Nie, Yuxin Chen, Lin Jiao, Yashar Komijani, Michael Smidman, Frank Steglich, Piers Coleman, Huiqiu Yuan
Disordered Systems and Neural Networks
Nonergodic extended phase for waves in three dimensions
Marcus Prado, Romain Bachelard, Robin Kaiser et al. (+1 more)
Wave transport in complex media is determined by the nature of quasimodes at the microscopic level. In three dimensional disordered media, waves generally undergo a phase transition from
diffusion to Anderson localization, characterized by exponentially localized modes. A remarkable exception are electromagnetic waves, whose vector-like nature prevents Anderson localization to occur. Here we demonstrate that both scalar and vector (electromagnetic) waves exhibit a non-ergodic extended phase characterized by fractal quasimodes, for a broad range of disorder strengths. While electromagnetic waves remain in the non-ergodic extended phase at high disorder strength, scalar waves eventually enter a localized regime. These results pave the way for the engineering of anomalous wave transport phenomena in disordered media without spatial correlations.
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All authors Marcus Prado, Romain Bachelard, Robin Kaiser, Felipe A. Pinheiro