Materials Science
The Effect of Geometry on Thermodynamic Response
Bojana Bokic, Sébastien R. Mouchet, Biljana Stankov et al. (+9 more)
At the nano- and microscale, various patterns influence and shape thermal and optical response, making them essential for the survival of various biological species. In addition, controlling thermal radiation is vital for a broad range of applications, such as thermal management, spectroscopy, optoelectronics, and energy conversion technologies. For this reason, there is strong pressure to elucidate the physics of thermal radiation at the nanoscale. In this article, we provide evidence that complex nanoscale geometries affect thermal management, leading to an unusual thermal response in heat-capacity measurements as a function of temperature. Beyond identifying the structural constraints associated with this unusual thermodynamic response, the current study introduces the possibility of shaping the apparent heat-capacity response through geometry without necessarily altering the system's chemistry.
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All authors Bojana Bokic, Sébastien R. Mouchet, Biljana Stankov, Sanja Ostojic, Nicolas Roy, Darko Vasiljevic, Yin Chang, Marija Radmilovic-Radjenovic, Branislav Radjenovic, Thierry Verbiest, Mohamed Hatifi, Branko Kolaric
Statistical Mechanics · Cross-listed from quant-ph
Davide Rinaldi, Mattia Moroder, Dario Gerace et al. (+2 more)
Fast and reliable
qubit reset is essential for the efficient operation of
quantum processors. Among the proposed strategies, Mpemba-effect-based protocols offer a simple route to accelerated relaxation, but provide limited insight into the optimality of the full reset dynamics.
Geometric approaches, by contrast, quantify optimality but do not generally suggest practical acceleration protocols. Here, we bridge these perspectives through a
geometric analysis of
entanglement-assisted
qubit reset. We show that entangling operations can redistribute local coherences across a multi-
qubit register, allowing the reduced state of each
qubit to follow a geodesic path towards the ground state. Remarkably, this locally optimal behaviour can emerge even when the collective
evolution becomes suboptimal in the full state space. We illustrate this interplay for different families of initial multi-
qubit states. Our results provide a
geometric perspective on Mpemba-inspired reset acceleration and clarify when extending two-
qubit protocols to larger registers provides a further advantage in the reset process.
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All authors Davide Rinaldi, Mattia Moroder, Dario Gerace, Giacomo Guarnieri, Steve Campbell
Materials Science
Repeated Growth and Hot Delamination of Single-Crystal Graphene: A Two-Kilometer Process-Design Assessment with hBN as a Separate Case
Rodney S. Ruoff
Large single
crystals of
graphene and hexagonal boron nitride (hBN) remain difficult to manufacture because batch growth and transfer limit area, throughput, and quality. This Perspective asks whether an atomically thin film could instead be grown, hot-delaminated, and regrown repeatedly on a long, reusable single-
crystal metal surface. No integrated process is demonstrated. Once rapid full-area growth is available, hot film removal is likely to become the rate-limiting step, whereas usable single-
crystal growth area sets the material produced per cycle. Two experiments determine whether the concept merits further development: rapid, damage-free delamination at or near the growth temperature, and acceptable film growth through repeated complete growth-dwell-peel-regrowth cycles. The analysis then examines the crystalline growth surface, layer control, interface and gas chemistries, product capture, quality criteria, energy, and scale. These provisional analyses expose known requirements, define early stop criteria, and guide experiments; they cannot anticipate every coupled constraint or failure mode.
Graphene is the quantitative baseline. hBN requires its own M(111), product thickness, apparatus, and scaling strategy. Pilot-scale development is justified only if the two central experiments succeed and the remaining gates can then be refined experimentally.
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Mesoscale and Nanoscale Physics
Switchable giant room-temperature nonlinear Hall effect in Bilayer Graphene
Margherita Melegari, Ignacio Gutiérrez-Lezama, Justin C. W. Song et al. (+1 more)
Utilizing
quantum second-order nonlinear transport for practical junction-free devices require materials with large and tunable nonlinearites at room temperature – a current materials platform challenge. Here, we report the nonlinear Hall effect (NLHE) in double-ionic gated bilayer
graphene devices that enable unusually strong inversion breaking. We observe NLHE that are readily switchable (on, off, and sign reversed) with second order nonlinear susceptibilities $\chi^{(2)}_{yxx}$ that reaches giant room-temperature values of $3\,10^{-3}\,\mu\mathrm{m}\,\mathrm{S/V}$, comparable to values commonly observed at low temperature in WTe$_2$ or in
graphene-based moiré superlattices, and three-to-four orders of magnitude larger than values reported in material systems recently employed in search of a room-temperature NLHE. Our devices produce corresponding THz voltage responsivities $\simeq 4\,10^{4}\,\mathrm{V/W}$, comparable to commercially available Schottky diodes. These are orders of magnitude better than for previously reported room-temperature NLHE devices rendering double-ionic gated bilayer
graphene a choice platform for junction-free nonlinear technology.
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All authors Margherita Melegari, Ignacio Gutiérrez-Lezama, Justin C. W. Song, Alberto F. Morpurgo
Mesoscale and Nanoscale Physics
Observation of dodecagonal replica bands in 30$^{\circ}$-twisted bilayer WSe$_2$
Christian Valentiner-Branth Fokdal, Chakradhar Sahoo, Thomas S. Nielsen et al. (+6 more)
Twisted bilayers of two-dimensional (2D) transition metal dichalcogenides are promising systems for achieving tunable quasicrystalline orders with emergent properties. The underpinning electronic structure and scattering processes in 2D quasicrystals with multiorbital dodecagonal replica bands have so far not been determined. Here, we utilize angle-resolved photoemission spectroscopy (ARPES) with micrometer spatial resolution to directly observe replica bands in 30$^{\circ}$-twisted bilayer WSe$_2$. The
symmetry and intensity distribution of the observed replicas are explained by interlayer Umklapp scattering from bottom to top WSe$_2$ layers. Our spectral function measurements are consistent with the presence of a van Hove singularity adjacent to the $\mathrm{K}$-valleys, which underlines the possibility of inducing electronic reconstructions in bilayers with a large interlayer twist angle.
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All authors Christian Valentiner-Branth Fokdal, Chakradhar Sahoo, Thomas S. Nielsen, Alfred J. H. Jones, Zhihao Jiang, Kenji Watanabe, Takashi Taniguchi, Marcin Mucha-Kruczyński, Søren Ulstrup
Materials Science
Self-selective growth of GaAs1-xBix on GaAs zinc blende/wurtzite nanowire heterostructures
Rohit Yadav, Sebastian Lehmann, Vidar Flodgren et al. (+5 more)
Site-selective nanostructure growth and material incorporation at the atomic scale offer a promising pathway for engineering
quantum materials and nanodevices. Here, GaAs nanowires (NWs) with an axial
heterostructure of alternating zinc blende (Zb) and wurtzite (Wz)
crystal phases are employed as templates for site-selective Ga and Bi overgrowth. Using X-ray photoemission electron microscopy (XPEEM) with nanoscale spatial resolution, we map elemental distribution and local chemical bonding to reveal the incorporation behavior of Bi atoms in {110} Zb and {11-20} Wz facets. Bi incorporation proceeds through an anion-exchange process, where Bi atoms replace As, forming local Ga-Bi bonds and producing a thin GaAs1-xBix shell. We observe
crystal-phase-dependent Bi incorporation, with higher Bi concentration in the Zb segments than in the neighboring Wz segments within the same NW. Furthermore, the Zb segment with higher Bi content exhibits reduced susceptibility to oxidation compared with the Wz segment, resulting in increased Ga-oxide in the Wz surfaces. This study highlights GaAs NW Zb/Wz
heterostructures as a template for controlled growth of GaBi and GaAs1-xBix nanostructures with tailored functionalities for
quantum applications
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All authors Rohit Yadav, Sebastian Lehmann, Vidar Flodgren, Evangelos Golias, Alexei Zakharov, Kimberly A. Dick, Anders Mikkelsen, Rainer Timm
Materials Science
A review of simulation, measurement techniques, and development in chip thermal design
Junnian Zhou, Feng Zhou and Shengying Yue
As integrated
circuits advance toward higher power densities, three-dimensional integration, and heterogeneous packaging, chip thermal management has become a key bottleneck limiting device performance, reliability, and lifetime. This article systematically reviews numerical simulation methods and experimental measurement techniques for chip thermal design, with particular emphasis on the technical challenges associated with multiscale and multiphysics coupling, thermal boundary resistance measurement, and high-heat-flux cooling. We first introduce macro- and device-scale thermal simulation methods, including equivalent thermal-
circuit models, the finite element method, and computational fluid dynamics, and discuss the application of
phonon transport theory and molecular dynamics at microscopic scales. We then examine the advantages and limitations of infrared thermography, thermoreflectance, Raman thermometry, and embedded sensors. Current limitations include the enormous computational cost, inaccurate multiscale coupling, expensive experimental facilities, and the physical limits of conventional cooling technologies. Finally, we discuss emerging directions, including AI-accelerated thermal simulation, embedded microchannel
liquid cooling, two-phase cooling, advanced high-thermal-conductivity materials, and multiphysics co-design, with the aim of advancing chip thermal management toward greater efficiency and intelligence.
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Quantum Gases · Cross-listed from physics.atom-ph
Measuring the Sr$^+$ 5s$_{1/2}$ Landé $g$-factor Using Singlet-Triplet Oscillations in a Circular Rydberg State of Strontium
Baptiste Muraz, Mathis Pepin, Corentin Guimard et al. (+3 more)
Circular states of strontium are promising platforms for
quantum technologies. They exhibit much longer lifetimes than
laser-accessible Rydberg states and possess an optically active ionic core that can be manipulated with
laser light. Here we trap circular states in optical tweezers by exploiting the dynamical polarizability of the ionic core. We measure the decay of the orbital component of a n=51 circular state and observe singlet-triplet
spin oscillations arising from the interplay of vector light shifts induced by the optical tweezers,
spin-orbit coupling associated with the Rydberg electron, and the difference in Landé $g$-factor between the ionic core and the Rydberg electrons. By observing the two electron
spin dynamics, we measure the
spin-orbit interaction and the correction $\delta g \sim$ 10^(-5) of the Landé $g$-factor of the Sr$^+$ 5s$_{1/2}$ ionic core electron with respect to that of a free electron. This provides a first high-precision measurement of $g_{\textrm{Sr}^+, 5s_{1/2}}$ = 2.002290(1).
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All authors Baptiste Muraz, Mathis Pepin, Corentin Guimard, Michel Brune, Brice Bakkali-Hassani, Sébastien Gleyzes
Superconductivity
Stabilization of Interband Phase Solitons in Two-Band Noncentrosymmetric Superconducting Rings
Yuriy Yerin, Boris Malomed, Stefan-Ludwig Drechsler et al. (+1 more)
Two-band
superconductors maintain a relative interband phase which can carry winding
soliton excitations in a superconducting ring, supported by independent winding numbers in the two bands. In rings of
superconductors obeying the inversion
symmetry the interband phase
solitons are metastable states, separated from the uniform ground state by the energy of screening currents. In this work we find that, breaking the inversion
symmetry strongly enough, one can make the
soliton a true ground state. In that case, a magneto-electric coupling, absent in centrosymmetric materials, contributes critically above a certain threshold, a relevant, free-energy term, odd with respect to the winding number, which biases the energy balance in favor of a particular winding sign. Once the bias outweighs the energy cost that originally made the
soliton metastable, a phase
soliton with a finite winding number becomes the ground state, with chirality set by the applied field. In current–flux measurements performed in
equilibrium states, the effect is demonstrated by field-odd
soliton branches, that replace the metastable ones existing in mesoscopic rings, built by two-component
superconductors, realizing a magneto-electric analog of the Little–Parks fluxoid-branch physics in the interband relative-phase sector.
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All authors Yuriy Yerin, Boris Malomed, Stefan-Ludwig Drechsler, F. Sebastian Bergeret
Statistical Mechanics
Brownian yet non-Gaussian diffusion through equilibrium nonlinear friction
Jakob Mihatsch and Andreas M. Menzel
In Brownian yet non-Gaussian
diffusion (BnGD) the mean squared displacement grows linearly in time. However, the displacement statistics do not follow a normal distribution throughout. Typically, they are non-Gaussian at intermediate times, before they cross over to Gaussian in the long-time regime. We demonstrate that nonlinear friction under correctly applied
stochastic equilibrium conditions provides an explanation of this phenomenon also for homogeneous environments.
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Disordered Systems and Neural Networks
Neural Renormalization Group Flow for Percolation
Anaclara Alvez, Luca Camagna, Sergio Chibbaro et al. (+4 more)
Machine learning offers a possible route to data-driven real-space renormalization when the relevant observables are nonlocal and difficult to prescribe explicitly. We explore this idea for two-dimensional site percolation developping a supervised, scale-shared neural architecture. The model recursively applies the same learned coarse-graining rule across scales, producing a latent field from which the crossing probability is predicted, while a corresponding fine-graining decoder reconstructs the largest-cluster mask. Trained only on small
lattices, the model extrapolates to substantially larger systems, recovers the spanning cluster with high fidelity, and produces observables obeying the expected finite-size scaling near the critical point. We observe that to get such performance it is key that the learned latent representation exhibits critical fluctuations and scale-dependent flows consistent with the renormalization-group structure of percolation.
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All authors Anaclara Alvez, Luca Camagna, Sergio Chibbaro, Cyril Furtlehner, François Landes, Gianluca Manzan, Lorenzo Mensi
Strongly Correlated Electrons
Interlayer-engineering of Charge Order Wave Vector in Kagome Metals
Muntafa M. Mahi, Quazi D. M. Khosru, M. Zahid Hasan et al. (+2 more)
Charge orders in the kagome metals AV$_3$Sb$_5$ sit at the center of a rich phase diagram that also includes superconductivity, nematicity, and signatures of time-reversal-
symmetry breaking. Yet even the basic question of which charge ordering wave vectors are intrinsic, and which are selected by dimensionality and
lattice coupling, remains unsettled. Importantly, the microscopic origin of different charge orders and, in particular, the relationship between the robust bulk $2 \times 2$ charge order and the controversial $4 \times 1$ modulation, which is primarily resolved by surface probes, remains unresolved. Here, we use first-principles calculations to study the role of interlayer coupling in CsV$_3$Sb$_5$ by tuning the interlayer separation from the monolayer limit to the bulk limit. In the monolayer AV$_3$Sb$_5$ (A = Rb, Cs), the
phonon spectrum exhibits no instability at the M point; instead, the dominant
lattice instability occurs at q = (1/4, 0, 0), consistent with a $4 \times 1$ modulation. As interlayer coupling increases in CsV$_3$Sb$_5$, an M-point
phonon progressively softens and becomes unstable already near c = 12.24 Å, evolving into the strong $2 \times 2$ instability characteristic of the bulk. These results identify interlayer coupling as a control parameter at a fixed stoichiometry that links competing $4 \times 1$ and $2 \times 2$ tendencies, providing a unified framework for understanding why multiple charge-order wave vectors coexist and compete in kagome metals.
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All authors Muntafa M. Mahi, Quazi D. M. Khosru, M. Zahid Hasan, Mahbub Alam, Md Shafayat Hossain
Materials Science
Instability of two-dimensional nonrelativistic altermagnets
Zhejunyu Jin and Peng Yan
Altermagnets (AMs) are collinear compensated magnets that exhibit momentum-dependent
spin splitting without requiring a net magnetization. Since local
magnetic moments and exchange-driven order do not rely on relativistic effects, altermagnetism can be naturally formulated in a nonrelativistic
spin-group framework. This raises a basic question: can two-dimensional altermagnetic order be stabilized by purely exchange interactions in the absence of
spin-orbit-induced anisotropy? We address this question by applying Bogoliubov's inequality to a minimal $d$-wave altermagnetic
spin model. We show that the anisotropic exchange pattern responsible for altermagnetism still contributes only a quadratic long-wavelength term to the Bogoliubov denominator. Consequently, short-ranged exchange interactions alone cannot stabilize long-range altermagnetic order in two dimensions when continuous
spin-rotation
symmetry is preserved. In contrast, the corresponding three-dimensional system has a finite small-momentum contribution and is not ruled out by the Mermin-Wagner argument.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Circular Dichroism Spectroscopy of Single Objects: Problems, Artifacts, and Corrections
Stefan Goppelt, Lisa M. Günther and Jürgen Köhler
Molecular aggregates are at the basis of a broad range of functional systems, including photosynthetic light-harvesting complexes, organic photovoltaics, optoelectronic devices, and molecular sensors. Their structural organization, however, is often difficult to resolve because intrinsic heterogeneity. In this context, circular dichroism (CD) spectroscopy is particularly powerful because of its sensitivity to the three-dimensional organization of molecular building blocks. Extending CD measurements from ensembles to individual objects therefore offers a unique approach to probing supramolecular architecture in heterogeneous, non-crystallizable systems. However, without spatial and orientational averaging, measurements are highly sensitive to imbalances between left- and right-circularly polarized excitation, deviations from ideal circular polarization, and polarization imperfections coupled to linear dichroism, which creates spurious CD signals. Here, we present a systematic theoretical and experimental framework for understanding, quantifying, and controlling artifacts in single-object CD spectroscopy. We develop a mathematical description of the principal artifact mechanisms, identify their origins in practical implementations, including Pockels-
cell-based polarization modulation, and establish strategies for their minimization. We validate this framework using an experimental implementation capable of acquiring CD spectra from individual molecular aggregates over 690-785 nm. Our results demonstrate that reliable single-object CD measurements are achievable when polarization-related artifacts are rigorously characterized and controlled. This Tutorial Review provides a unified theoretical framework and practical guide for single-object CD spectroscopy and its application to single-particle chirality, supramolecular photonics, and biophotonics.
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Other Condensed Matter
Non-Hermitian Skin Effect from Radiative Coupling in a Reciprocal Chiral Medium
Kin Hung Fung, Changhao Meng, Yixin Xiao et al. (+1 more)
We show that long-range radiative coupling in a passive chiral medium produces an unusual non-Hermitian skin effect in a chain of dipoles. The skin-mode profile consists of a long-range light-line branch-cut contribution, a non-exponential factor $1/[n(\ln n)^2]$ with $n$ being the site number. Finite-chain calculations show that part of the open-boundary spectrum contracts toward the Bloch spectrum, whereas the number of boundary-localized modes remains extensive. The retarded radiative coupling makes both the real-space profile and the finite-size spectral signatures of boundary localization depart from standard finite-range and pure exponential coupling theory.
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All authors Kin Hung Fung, Changhao Meng, Yixin Xiao, C. T. Chan
Mesoscale and Nanoscale Physics
Topologically protected perfect crossed Andreev reflection in flux-engineered quantum wire junctions
Abhiram Soori
Generating non-locally entangled electron pairs via Cooper-pair splitting is vital for solid-state
quantum information processing. However, isolating the underlying crossed Andreev reflection (CAR) is challenging due to competing transport processes like electron tunneling (ET) and local Andreev reflection (AR). Here, we propose a flux-tunable four-terminal normal metal-
superconductor junction that achieves deterministic, 100% efficient CAR. We demonstrate that at exactly half a
magnetic flux
quantum ($\phi=\pi$), exact destructive Aharonov-Bohm and Peierls interferences structurally forbid ET and AR respectively. By tuning the central junction hopping, electron reflection is also suppressed to zero. Using the Cauchy argument principle, we prove that this suppression manifests as a quantized topological winding number, guaranteeing a topologically protected unit CAR probability. We establish that this regime is characterized by a strictly positive cross-correlation shot noise, providing an unambiguous experimental signature of Cooper-pair splitting. Furthermore, this perfect CAR is nearly broadband within the superconducting gap and remarkably robust against structural disorder, offering a highly resilient architecture for deterministic nonlocal
entanglement generation.
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Statistical Mechanics · Cross-listed from quant-ph
Adiabatic Otto-like quantum thermodynamical cycle in the non-quasi-static regime
Salvador J. Robles-Pérez and Salvador Castillo-Rivera
We show a finite-time Otto-like
quantum thermodynamic cycle that preserves the adiabatic population structure of a time-dependent harmonic oscillator in the non-quasi-static regime. In the conventional energy representation, finite-rate driving induces non-adiabatic population redistribution and leaves residual excitations after the
Hamiltonian has returned to its initial value. We show that this difficulty can be avoided by formulating the dynamics in the Lewis-Riesenfeld invariant representation, without modifying the physical
Hamiltonian through auxiliary counterdiabatic driving. For a parametric Mathieu protocol,
quantum inertia produces a mismatch between the spatial width of the working mode and its transient dressed energy scale. We propose an experimental implementation of this scheme in a trapped-ion Paul trap using stimulated Raman interactions, with independent control of the
laser detuning and beam intersection angle. This provides a finite-time implementation in which the invariant population structure is preserved while the physical trap frequency evolves non-quasi-statically. Our results establish a clear distinction between adiabatic operation and quasi-static driving, providing a route toward finite-time
quantum thermal cycles that retain the adiabatic energy structure without requiring the quasi-static limit.
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Materials Science
A solid-solution approach for room-temperature bulk plasticity in KTa1-xNbxO3
Alexander Frisch, Jiawen Zhang, Martin Setvin et al. (+3 more)
Dislocations are being engineered into perovskite oxides to harvest versatile functional properties. One major bottleneck, however, persists: perovskite oxides that can be engineered with dislocations, particularly via mechanical deformation at room temperature in bulk scale, have so far been limited to only three materials: SrTiO3 (2001, Brunner et al.), KNbO3 (2016, Mark et al.), and KTaO3 (2024, Fang & Zhang et al.). Here, we propose a simple and effective approach by using solid solution to significantly extend the range of materials. We showcase KTa1-xNbxO3 (0<x<1) perovskite oxides for their bulk plasticity at room temperature by constructing a closed-loop validation workflow that includes
crystal growth, Brinell indentation, bulk compression, and transmission electron microscopy characterization. Our findings are expected to unlock the materials toolbox for dislocation-tuned functionality of perovskite oxides.
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All authors Alexander Frisch, Jiawen Zhang, Martin Setvin, Xuping Wang, Wenjun Lu, Xufei Fang
Superconductivity
Strain-driven orbital-selective reconstruction and bicollinear-to-stripe evolution in FeTe
Zhenfeng Ouyang, Yin Chen, Yi-Heng Tian et al. (+4 more)
FeTe, as a representative parent material among iron-based
superconductors, provides an ideal platform for exploring the interplay among orbital-selective correlations, magnetism, and unconventional superconductivity. However, a unified picture of the correlated electronic structure and magnetism of FeTe under strain remains to be fully clarified. Here, combining density functional theory plus dynamical mean-field theory and Heisenberg model analysis, we uncover an orbital-selective reconstruction of the correlated electronic structure and reveal a strain-driven trajectory from bicollinear to stripe antiferromagnetism (AFM) via an intermediate competing staggered $n$-mer AFM regime in FeTe. Moderate strain gives rise to a regime where more coherent quasiparticles coexist with suppressed local moments. Further strain drives FeTe into an incoherent correlated regime with robust local moments and Fe-$3d_{z^2}$-dominated low-energy states. These results establish a strain-driven trajectory across distinct
magnetic and correlated electronic states in FeTe.
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All authors Zhenfeng Ouyang, Yin Chen, Yi-Heng Tian, Jia-Ming Wang, Rong-Qiang He, Kai Liu, Zhong-Yi Lu
Quantum Gases
Emptiness formation in the Lieb-Liniger gas: hydrodynamic instantons and a conjectured rate function
Boris A. Khanikati and Alexander G. Abanov
We study the emptiness formation probability (EFP) in the ground state of the repulsive one-dimensional Lieb-Liniger Bose gas. For a macroscopic empty interval of length $2R$, its leading asymptotic behavior is described by a rate function $f(\gamma_0)$, defined by $-\log P(R)\sim(\rho_0R)^2f(\gamma_0)$, where $\rho_0$ is the mean density and $\gamma_0$ is the dimensionless interaction strength. We propose a parameter-free integral equation for $f(\gamma_0)$. Starting from the exact dual-field Fredholm-determinant representation of the EFP, we show how the conjectured kernel arises formally and identify the uniform asymptotic statement that remains to be proven for a rigorous derivation. The
conjecture reproduces the Tonks-Girardeau and weak-coupling limits, as well as the first correction obtained independently in both limits. It also agrees at the few-percent level with numerical minimization of the Lieb-Liniger hydrodynamic action over more than four orders of magnitude in coupling. The numerical calculation yields the corresponding emptiness instantons and their astroid-like
vacuum regions.
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Statistical Mechanics
When dissipative steady states admit thermodynamic occupation laws
Tetsu Ichitsubo
Non-
equilibrium steady states (NESSs) generally lack thermodynamic occupation laws because finite stationary circulation and a globally exact rate-ratio field cannot coexist for the same Markov generator. Here we construct a sector-separated geometry that overcomes this incompatibility without arresting dissipation.
Entropy-production exposure-and-separation excludes the
entropy-producing state~$0$ from the conditional occupation
manifold while retaining it in the dissipative full graph; physical returns $i\to0\to0^\ast$ become effectively Markovian in the strong-bias/rapid-reset (SR) limit. For a thermodynamically complete conditional
manifold, autonomous redistribution (AR) eliminates residual futile circulation, making the rate-ratio one-form exact. Thermodynamic calibration gives $X_i=\beta(\Delta\mu- \mathcal F_i^{\mathrm{cost}})$ and $p_i=e^{X_i}/Z_\mathcal{C}$, with $Z_\mathcal{C}=1+\sum_i e^{X_i}$. Full-graph probabilities factorize exactly as $P_\alpha=(1-P_0)p_\alpha$. In the SR limit, the kinetic factor tends to unity while $p_\alpha\to e^{X_\alpha}/Z_\mathcal C$, yielding $P_\alpha\to p_\alpha$ while finite dissipation persists. Near AR, integrability is lost linearly in residual cycle current whereas dissipation begins quadratically. In the binary zero-cycle-rank limit, occupation redistributes autonomously under maintained $\Delta\mu$ bias, yielding the inverted Fermi–Dirac law, which is applied to thermal smearing in
quantum-dot
lasers. The framework provides constructive acquisition conditions and failure diagnostics for thermodynamic occupation laws in dissipative NESSs.
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Soft Condensed Matter
Influence of twist direction and large deformation on soft material torsional contact
Yucai Hu, Pengfei Li, Michele Ciavarella et al. (+2 more)
Shear-induced contact area reduction is widely observed in soft contacts, yet recent torsional experiments have revealed a more complex non-monotonic
evolution in which the contact area first increases and then decreases with twist angle. The mechanism responsible for this initial area increase and the role of large deformation in the overall area
evolution remain unclear. In this study, we experimentally investigate the torsional contact response of soft Polydimethylsiloxane (PDMS) spheres by combining forward-backward twist tests with a systematic variation of the curing-
agent-to-base ratio to tune material softness and deformation level. The loading-unloading tests show that the torsional interface is strongly irreversible: during unloading, the contact area follows a decrease-increase-decrease path rather than retracing the loading branch, and repeatable petal-like edges appear, indicating a wrinkle-induced surface instability. By decreasing the mixing ratio, we find that larger deformation strengthens the area-reduction contribution and eventually suppresses the initial area increase, leading to a monotonic area decrease during loading for sufficiently soft PDMS. Softer PDMS also exhibits lower shear strength, weaker torque oscillations, and improved repeatability. The results provide experimental evidence that large deformation can drive shear-induced contact area reduction, while the origin of the initial area increase remains unresolved. These findings narrow the possible mechanisms (e.g., triboelectrification) responsible for the initial area increase and provide a stringent
benchmark for frictional contact models of soft interfaces.
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All authors Yucai Hu, Pengfei Li, Michele Ciavarella, Yue Wu, Yang Xu
Strongly Correlated Electrons
Thermally quenched metastability in metal-insulator transitions via elemental substitution
Hiroshi Oike, Yasunori Takahashi, Keisuke Shibuya et al. (+5 more)
Thermal quenching inhibits equilibration toward the thermodynamic ground state during phase transitions, revealing metastable phases such as structural glasses and quenched
alloys. Whether such thermally quenched metastability can be realized in metal-
insulator transitions has remained an open question because these transformations are governed by collective electronic reorganization rather than atomic
diffusion. We demonstrate that rapid cooling exceeding 10$^9$ K s$^{-1}$ kinetically avoids the metal-
insulator transition, stabilizing a long-lived metastable metallic phase in tungsten-substituted VO$_2$. Temperature-dependent relaxation reveals nucleation-dominated kinetics with a thermal activation barrier introduced by tungsten substitution. Our results establish elemental substitution as a route to thermally quenched metastability in metal-
insulator transitions, expanding metastable phase control to electronic phases.
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All authors Hiroshi Oike, Yasunori Takahashi, Keisuke Shibuya, Masaki Nakano, Tatsuki Hanada, Motoaki Hirayama, Hiroko Tokoro, Fumitaka Kagawa
Materials Science
Atomic investigations on the mechanical properties of CoCrNi medium-entropy alloy nanowires
Yang Yu
This work investigated the mechanical properties of CoCrNi medium-
entropy alloy (MEA) nanowires under uniaxial tensile loading along three crystallographic orientations [100], [110] and [111]. The face-centered cubic (FCC) single-
crystal CoCrNi nanowires exhibit pronounced anisotropy Molecular dynamics simulations were employed to provide atomic-level insights into the plastic deformation mechanism. The surface effect causes dislocations to nucleate at the free surface and slip inward. The temperature effect was also considered. Under identical
geometric configurations,
crystal orientations, and temperatures, interatomic interactions govern key mechanical properties such as Young's modulus and yield strength. Simulation results reveal a strong linear correlation between the average atomic force and mechanical performance across eight representative FCC metallic nanowires (Al, Au, Ag, Cu, Ni, Al19Mg
alloy, FeCoCrCuNi high-
entropy alloy (HEA), and CoCrNi MEA). This study delivers novel insights into the mechanical behavior of metallic nanowires and offers guidance for the rational design of
alloy nanowires.
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Statistical Mechanics · Cross-listed from astro-ph.CO
Approximating the peculiar velocity distribution of dark matter halos with Tsallis statistics
Jun Pan and Ming Li
Dark matter
halos, which host
galaxies and
galaxy clusters, have peculiar velocities far from thermal
equilibrium. Characterizing the nonlinear and non-Gaussian features of this velocity distribution improves our understanding of the gravitational
evolution of the
cosmic web and supports related cosmological applications. We endeavor to establish a connection between the peculiar velocity distribution of
halos and nonequilibrium statistical mechanics, with the objective of obtaining a model that is both concise and accurate for practical applications. We extracted
halo samples from large N-body simulations and performed maximum-likelihood fits to the peculiar velocity distributions using a two-parameter Tsallis model, derived from non-extensive statistical mechanics. On the theoretical side, we reformulated the
halo distribution in the superstatistics framework by means of a generalized Gram-Charlier expansion based on the gamma distribution. For
halo peculiar velocities below 1000 km/s, the Tsallis model achieves 5 percent accuracy over z=0-2, with performance improving toward lower
redshifts. Our results show that the
halo velocity distribution becomes increasingly non-Gaussian and departs further from
equilibrium over time. The best-fit parameters depend only weakly on mass, though low-mass
halos exhibit slightly stronger non-Gaussianity. The two parameters, especially the velocity dispersion, offer promising probes of cosmological parameters. Theoretically, we find that in general the
halo peculiar velocity distribution function is expressible as a superposition of a series of Tsallis distribution functions, while simulation results demonstrate that the zeroth-order approximation, namely a single Tsallis function, already achieves sufficient accuracy.
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Other Condensed Matter · Cross-listed from physics.optics
Beyond geometric symmetry: Broadband linear relations in wave scattering
Malte Röntgen, Sucui Luo, Xuelong Chen et al. (+4 more)
The design and control of wave scattering, that is, of the reflection and transmission parameters of a device, is of ubiquitous importance. These parameters generally change with varying frequency, though certain frequency-independent linear relations may exist between them. Reciprocity and
geometric symmetry (reflections, rotations, etc.) are classic and well-known examples that are present in many devices and significantly ease their design. In this work, we go beyond these and introduce a new class of relations that cannot be induced by reciprocity or
geometric symmetry. Choosing networks of waveguides as our workhorse, we discuss the conditions and consequences of such novel behaviour and showcase suitable example setups. We further experimentally test our predictions using coaxial cables and find excellent agreement in the broad frequency range between 0 and 1 GHz. Our work not only deepens the theoretical understanding of waveguide network dynamics, but also opens new avenues for applications in broadband signal processing,
quantum information, and integrated photonics.
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All authors Malte Röntgen, Sucui Luo, Xuelong Chen, Chenyu Zhang, Ruotao Ye, Tianshu Jiang, Wenlong Gao
Disordered Systems and Neural Networks
Dynamical phase selection controls compute scaling in looped transformers
Gunn Kim
A looped
transformer performs inference by iterating a weight-tied map, making its computation a dynamical process whose cost is set by the resulting inference dynamics. Here we show that networks with identical architecture and objective, trained to identical accuracy, nevertheless realize distinct dynamical phases depending strongly on initialization, and that the bifurcation defining each phase determines how test-time compute scales. The phases are distinguished by their bifurcation mechanisms, including a saddle-node fold and a Neimark-Sacker-type transition to bounded nonstationary motion. In the fold phase, a one-dimensional normal-form reduction predicts both the relaxation-time and spectral-gap amplitudes from local derivatives of the trained map, yielding the parameter-free relation $\tau(\varepsilon)[1-\lambda_{\max}(-\varepsilon)]\to\pi$. Composed with a regular distribution of problem difficulty, the same critical slowing down produces the workload-level tail $P(\tau>N)\sim N^{-2}$. In the Neimark–Sacker phase, the fold scaling law disappears rather than merely changing its prefactor. Thus, test-time compute is not determined by architecture alone. It is governed by the dynamical phase of the solution found by training.
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Disordered Systems and Neural Networks · Cross-listed from math.CO
Random Recursive Simplicial Complexes
P. L. Krapivsky and M. Lucas
We investigate random recursive simplicial complexes growing by adding, at each step, a vertex together with a simplex formed by joining the new vertex with a randomly chosen existing simplex. We also add all faces of the new simplex to ensure that the resulting object remains a simplicial complex. If the choice of an existing simplex is uniform among simplices of dimension $<m$, the number $S_d$ of simplices of any admissible dimension $d\leq m$ is an asymptotically self-averaging random variable. This feature allows us to determine the asymptotic growth law of the average of $S_d$ when the number of vertices diverges. We also probe the degree distribution, examine the probabilities of various extreme outcomes, and analyze the characteristics of the first vertex.
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Strongly Correlated Electrons
Field-amplified readouts of weak altermagnetic exchange in MnF$_2$
Guowen Jiang, Feilong Wang, Yunhua Wang et al. (+4 more)
MnF$_2$, the textbook two-sublattice antiferromagnet, has reemerged as a prototypical altermagnet, yet the sublattice-odd exchange that defines this identity remains under active debate: it enters the
magnon splitting only in quadrature with the dipole–dipole interaction, its magnitude suppressed and its sign erased. An overdetermined first-principles total-energy mapping resolves this scale as a seventh-neighbor imbalance $\delta{J_7}\simeq+8~\mu$eV. The resulting
Hamiltonian, with the dipole–dipole interaction included explicitly, reproduces the low-energy gap and the visible finite-momentum splitting. A longitudinal field $B\parallel c$ then acts as a linear amplifier of the hidden scale, opening two signed, field-linear readouts. The first is the compensation field $B^\ast(\mathbf Q)$, the position of minimum splitting, which is equal and opposite at the rotation-related partner momenta: a shift from zero field is itself evidence of a finite imbalance, its side gives the sign, and its magnitude, $|B^\ast|\simeq0.34$~T here, gives the scale. The second is the fixed-field contrast of the partner splittings, $\simeq0.14$~meV at $1$~T, six times the zero-field excess: a sign check from just two spectra. Both readouts survive a $0.12$~meV energy resolution, and the construction carries over to any easy-axis collinear altermagnet, bringing $\mu$eV altermagnetic exchange within present instrumental reach.
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All authors Guowen Jiang, Feilong Wang, Yunhua Wang, Fawei Zheng, Bin Xi, Hong-Gang Luo, Jize Zhao
Strongly Correlated Electrons
Competition between Geometrical Frustration and the Kondo Effect in CePdAl Revealed by High-Resolution Magnetization
Yusei Shimizu, Shota Nakamura, Yoichi Ikeda et al. (+4 more)
CePdAl is a heavy-
fermion compound with a quasi-kagome structure, where geometrical frustration competes with the Kondo effect. Using a high-sensitivity magnetometer, we observe clear first-order metamagnetic transitions without magnetization plateaus in CePdAl at 80 mK, indicating a lifting of frustration through the suppression of the Kondo effect and
spin flips of ordered moments under fields. An anomaly in the nonlinear
magnetic susceptibility at 4.3 T suggests nondipolar correlations in the polarized paramagnetic state. Furthermore, we found no evidence of non-Fermi-
liquid behavior in the high-field region, where the antiferromagnetic order is completely suppressed. These findings establish the essential thermodynamic constraints for understanding the field-induced
spin-
liquid state in CePdAl.
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All authors Yusei Shimizu, Shota Nakamura, Yoichi Ikeda, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara, Yosikazu Isikawa