Materials Science
Computational Determination of Optimal Growth Protocols for Metastable Polymorphs
Simon B. Hollweger, Anna Werkovits, Tadeas Lesovsky et al. (+1 more)
The reliable growth of a desired target structure remains a central challenge for organic-inorganic interfaces. Specific interface structures can exhibit properties that are superior compared to those of other possible interface structures, but identifying growth conditions that selectively produce a given surface structure is difficult, particularly when the target structure is thermodynamically metastable. Here, we demonstrate how time-dependent temperature and pressure protocols can be optimized to promote the high-yield formation of a metastable surface polymorph. To this end, we combine kinetic Monte Carlo simulations with a parameterized nucleation-and-growth model and apply optimal control theory to predict growth recipes that maximize the yield of the desired target structure. Applying this approach to a prototypical model of an organic molecules adsorbed on a metal surface, we identify experimentally plausible protocols that guide the system through phase space while avoiding kinetic growth regimes in which formation of the thermodynamically stable structure is favored. Compared to a manually optimized three-step protocol, the optimized control trajectory increases the yield of the desired metastable phase from 73 % to 97 % for the same total protocol duration.
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All authors Simon B. Hollweger, Anna Werkovits, Tadeas Lesovsky, Oliver T. Hofmann
Strongly Correlated Electrons
Pressure-Driven Structural Transitions without a Displacive Charge-Density Wave in La$_2$SmNi$_2$O$_7$
J. Huang, Sitaram Ramakrishnan, P. Rodière et al. (+7 more)
We investigated the structural properties of
bilayer nickelate La$_2$SmNi$_2$O$_7$ as a function of pressure and temperature. At ambient conditions, we show that the material crystallizes as a monoclinic superstructure distinct from the one previously reported and close to the pseudo-orthorhombic structure of pristine La$_3$Ni$_2$O$_7$. No signatures of satellite reflections associated with charge density wave (CDW) ordering are detected at low temperature. Upon compression, a sequence of pressure-induced structural transitions from monoclinic to orthorhombic 15 GPa and then tetragonal 21 GPa
symmetry is observed. Within the superconducting dome, the quality of the X-ray diffraction data enables structural refinements enabling theoretical models to understand the emergence of superconductivity.
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All authors J. Huang, Sitaram Ramakrishnan, P. Rodière, P. Toulemonde, Z. Rahmany, V. Balédent, B. Vignolle, Sourav Marik, P. Fertey, P. Foury-Leylekian
Soft Condensed Matter
Stability and equilibria of a compressible elastic membrane in Stokes flow
Sho Kawakami, Han Zhou, Po-Chun Kuo et al. (+2 more)
We formulate a continuum model for a compressible lipid-
bilayer membrane immersed in Stokes flow, replacing exact local area inextensibility by conservation of an areal phospholipid density. The membrane free energy combines Helfrich bending, spontaneous
curvature, and a finite area-compression penalty, so that membrane tension becomes a constitutive response to lipid-density variation rather than a Lagrange multiplier enforcing local area conservation. The resulting interfacial stress includes normal elastic forces and tangential Marangoni stresses generated by lipid redistribution; these stresses arise from membrane compressibility and can produce an effective negative tension when the local lipid density exceeds its preferred value. We further derive the linear stability of circular membranes in two dimensions and spherical membranes in three dimensions under full Stokes hydrodynamic coupling. In both cases, bending stabilizes the base shape, while excess lipid density destabilizes it by favoring increased membrane area. The first instability occurs in the lowest nontrivial shape mode, m = 2 in two dimensions and j = 2 in three dimensions. Energy expansions near onset show that the two-dimensional instability is a pitchfork bifurcation, whereas the three-dimensional instability is generically transcritical because prolate and oblate perturbations are geometrically distinct. These results provide a controlled compressible extension of classical vesicle mechanics and directly connect lipid-density variation, membrane tension, hydrodynamic coupling, and shape instability.
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All authors Sho Kawakami, Han Zhou, Po-Chun Kuo, Yoichiro Mori, Yuan-Nan Young
Strongly Correlated Electrons
What Makes Three-Dimensional Quantum Spin Liquids Possible?
Yasir Iqbal and Ronny Thomale
Quantum spin liquids are often introduced through a low-dimensional intuition: weak coordination and strong zero-point motion frustrate conventional
magnetic order. This view has shaped much of the field, but it misses another route to
quantum disorder. In many frustrated magnets, the more natural starting point is not a fluctuating version of an ordered state, but a locally constrained
manifold of low-energy configurations. Within such a
manifold,
quantum dynamics can generate an emergent gauge theory, with fractionalized excitations and collective modes absent in ordinary magnets. Here we ask why such phases can be stable in three spatial dimensions. We argue that three-dimensional
quantum spin liquids need not be regarded as fragile exceptions to the tendency of 3D magnets to order. They can arise when local constraints suppress premature order selection, coherent tunneling processes connect the constrained
manifold, and the
topology of gauge defects permits a deconfined regime. For compact gauge theories, three dimensions can even reverse the usual dimensional intuition: regimes that are unstable or fine-tuned in lower dimensions may become stable over finite regions of parameter space. We organize the discussion around constraint-driven Coulomb phases, weak harmonic order-by-disorder selection, and the role of
spin-orbit or multipolar interactions in generating the required microscopic dynamics. We close with experimental diagnostics, candidate materials, and open theoretical questions for three-dimensional
quantum spin liquids
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Materials Science
Color Centers in Cubic Boron Nitride
William Stenlund, Joel Davidsson, Viktor Ivády et al. (+2 more)
Cubic boron nitride (c-BN) is a wide-bandgap
semiconductor (WBGS) with potential applications in both power electronics and
quantum technologies. Color centers in WBGS can be used as single
photon emitters and
quantum sensors. Several zero
phonon lines have been measured in c-BN experiment but not yet identified. To systematically probe the combinatorially complex chemical space of defects, we generate a large-scale point defect data set for c-BN. We apply density functional theory calculation implemented in a high-throughput workflow Automatic Defect Analysis and Qualification (ADAQ) to broadly screen for point defect complexes containing s- or p-elements. More than 8000 defects have been calculated in different charge and
spin states. The calculated properties are stored in defect database and are then filtered to find defects with properties similar to the NV-center in diamond. More accurate calculations using hybrid functionals are then performed on a selected set of promising defects to further assess their suitability for
quantum technology. In particular, we reexamined the ONVB defect which likely explains the GC-2 line. The hybrid calculations also suggest other defect candidates with bright emission, such as two carbon defects and the NaB- defect.
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All authors William Stenlund, Joel Davidsson, Viktor Ivády, Rickard Armiento, Igor A. Abrikosov
Other Condensed Matter · Cross-listed from physics.optics
Mid-IR single- and dual-electro-optic comb generation with an ultrafast modulator
Gia-Long Ngo, Luca Lucia, Stefano Pirotta et al. (+9 more)
Mid-infrared (mid-IR) frequency combs are powerful tools for molecular sensing, industrial monitoring, and precision spectroscopy, yet their development beyond 5 um remains limited. Electro-optic modulation offers a promising path toward compact, agile comb generation, but extending this approach into the mid-infrared has been hindered by the lack of practical, high-performance modulators. Here we present an approach that leads to efficient generation of mid infrared frequency combs around 9 um, by employing ultrafast, room temperature, free space electro optic intensity modulators. By driving a single modulator with short electrical pulse trains, we realize both single- and dual-comb operation from a continuous-wave
quantum cascade
laser, providing a compact and versatile platform for mid-IR spectroscopy. This scheme produces combs with tunable repetition rates down to the megahertz range with direct observation on an electrical spectrum analyzer without any interferometer. As a proof of concept, we perform single- and dual-comb spectroscopy of a germanium etalon and an ammonia
cell, achieving resolution far beyond that of conventional
Fourier-transform infrared (FTIR) spectrometers and highlighting the potential of this approach for precise measurements in the long-wavelength molecular-fingerprint region. These results establish high-performance mid-IR modulators as a promising route toward practical, energy-efficient frequency-comb systems for sensing and spectroscopy.
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All authors Gia-Long Ngo, Luca Lucia, Stefano Pirotta, Mario Malerba, Lianhe H Li, Stefano Barbieri, Victor Merupo, Edmund H Linfield, Benoit Darquié, Jean-Michel Manceau, Adel Bousseksou, Raffaele Colombelli
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Dissipative preparation and stabilization of d-mode multinomial cat states
S. Zhao and A. Metelmann
Engineering dissipation with tailored steady states has become a powerful approach for preparing and stabilizing
quantum states. In this framework, engineered dissipative processes continuously steer a system towards desired target states while suppressing unwanted noise. However, extending this idea to multimode systems is challenging and remains largely unexplored, although this class of states is a powerful resource for
quantum sensing and
quantum information processing applications. Here, we propose a general method to design the required dissipative processes for the generation of multimode cat states in bosonic systems. We show that the engineered dissipation prepares such states from the
vacuum with high fidelity and robustly stabilizes them against decoherence. As a result, their lifetime is extended by several orders of magnitude compared to natural decay times, which in turn enhances their applications in
quantum techonologies. We specifically focus on the preparation and stabilization of two-mode binomial cat states and discuss a pathway for the implementation in superconducting
circuit. However, our scheme can also scale up to arbitrary d-mode multinomial cat states associated to $\mathfrak{su}(d\ge2)$
algebras, and thus, our scalable framework provides a feasible route towards stabilizing compact nonclassical states.
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Statistical Mechanics
Variance of the $SIS$ Epidemic on Networks: A Diffusion Approximation
Lucija Nora Farkaš, Sebastian Morel Balbi, Hrvoje Štefančić et al. (+2 more)
Functional laws of large numbers (FLLNs) describe the mean-field trajectory of epidemics on networks, but say nothing about the fluctuations around it. These fluctuations are governed by moments of the degree distribution not relevant at the level of the mean. A rigorous functional central limit
theorem (FCLT) exists for the susceptible–infected ($SI$) process on configuration-model graphs, but no analogue exists for $SIS$, where recovery reintroduces vertices into the susceptible pool with partially known neighborhoods, breaking the clean neighborhood distribution the $SI$ derivation relies on. We develop a tractable variance approximation for Markovian $SIS$ on configuration-model graphs, combining Gleeson's approximate master equation (AME) framework with a van Kampen system-size expansion in the spirit of the $SI$ FCLT. We derive a closed drift and
diffusion matrix for a reduced susceptible/$SI$-edge/$SS$-edge count vector and obtain the time-dependent covariance via the associated Langevin/Lyapunov equation. Validation against Gillespie simulation across Poisson, regular, and power-law networks shows close agreement, with deviations near the epidemic threshold and in strongly heterogeneous networks.
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All authors Lucija Nora Farkaš, Sebastian Morel Balbi, Hrvoje Štefančić, István Zoltán Kiss, Vinko Zlatić
Mesoscale and Nanoscale Physics
Many-body quantum chaos in excitonic spectra from first principles
Daniel Hernangómez-Pérez and Rafael A. Molina
We demonstrate that realistic excitonic many-body
Hamiltonians obtained from first-principles GW-Bethe-Salpeter equation calculations can exhibit
quantum chaos governed by random-
matrix universality. Considering a prototypical van der Waals
heterostructure (WS$_2$-
graphene), with and without
lattice disorder, we analyze their energy-resolved spectral correlations and identify a disorder-driven crossover from regular to complete chaotic dynamics. We show that while pristine samples exhibit incomplete chaos (non-ergodicity) due to an approximate valley
symmetry that restricts excitonic mixing, the presence of disorder-induced electronic flat bands act as a catalyst for valley mixing to drive the system into a fully developed chaotic (ergodic) regime with reduced
symmetry. Crucially, fluctuations in many-body oscillator strengths are shown to follow universal Porter-Thomas statistics, directly linking the underlying
quantum chaos and experimentally accessible optical observables. Finally, by examining long-range spectral correlations, we estimate the Thouless time associated to excitonic mixing across the entire many-body bandwidth. Our results establish
excitons as a highly tunable platform for probing many-body ergodicity and its spectroscopic signatures in realistic interacting 2D materials.
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Materials Science
Anomalous Structural Response of Quasi-One-Dimensional Antiferromagnetic Metal KMn6Bi5 under high pressure
Hanming Ma, Qingxin Dong, Tong Shi et al. (+11 more)
We report high-pressure single-
crystal X-ray diffraction measurements on the quasi-one-dimensional (Q1D)
antiferromagnetic metal KMn6Bi5 up to 12.5 GPa, revealing the detailed pressure
evolution of its atomic coordination environment. We find that the
lattice exhibits pronounced anisotropic compressibility-the relative changes in the a and b
lattice parameters reach a/a0=0.91 and b/b0 = 0.94 at 12.5 GPa-and a distinct structural anomaly emerges near 11 GPa without any
symmetry-breaking. Detailed structural analysis further uncovers an anomalous hardening of the Mn nanotubes between 5 and 11 GPa, followed by a configuration optimization of the Mn/Bi nanotubes around 11 GPa. These features correlate closely with the reported pressure-temperature phase diagram of KMn6Bi5 and compare favorably with the chemical pressure effects induced by substituting K with Na, Rb, or Cs. Our findings provide key microscopic insights into how coordination environment modulation governs the stability of electronic orders in low-dimensional systems.
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All authors Hanming Ma, Qingxin Dong, Tong Shi, Xiaoli Ma, Zhongjin Wu, Shaoheng Ruan, Pengtao Yang, Zhaoming Tian, Jianping Sun, Yoshiya Uwatoko, Genfu Chen, Xiaohui Yu, Bosen Wang, Jinguang Cheng
Other Condensed Matter · Cross-listed from gr-qc
Dark energy genesis: modeling dissipative effects in primordial cosmology
Pietro Pellecchia, Alejandro Perez and Salvatore Ribisi
In various approaches to
quantum gravity, spacetime geometry is understood to emerge from more fundamental discrete structures at the Planck scale. As sometimes posited, their presence could lead to dissipative effects in the smooth effective sector. In this paper, we develop the idea of non-conservation in
gravity, by introducing an effective cosmological model within unimodular
gravity, in which a varying cosmological constant arises as a consequence of dissipation. We show that this requires to incorporate hidden degrees of freedom – termed
quantum gravity defects – that act as an effective bath for the matter fields. To illustrate the viability of the framework, we study the case of an Ohmic bath inspired by the Caldeira-Leggett model for Brownian motion, leading to a
diffusion equation for the matter energy density. The results show that, starting from a
primordial universe with no dark energy, dissipation can account for the generation of a small positive cosmological constant.
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Materials Science
Enhanced hydrogen response of copper-doped TiO$_2$ synthesised by helium-assisted magnetron sputtering
Akash Kumar, Nirmal Kumar, David Kolenatý et al. (+4 more)
Cu-doped TiO$_2$ thin films for hydrogen sensing were synthesised by reactive DC magnetron sputtering in Ar/O$_2$/He mixtures, with the He fraction used as a control parameter for film growth. By combining normal-angle deposition (NAD) and glancing-angle deposition (GLAD) with post-deposition annealing, the effects of He on microstructure formation and sensor performance were examined. X-ray diffraction and electron microscopy revealed that He promotes nanostructuring,
lattice expansion in as-deposited NAD films, increased porosity after annealing, and a stronger anatase character in the final
oxide layers. These structural changes, which enhance the reactive surface area, lead to improved hydrogen sensing at 300\,$^\circ$C in 1~vol.\,% H$_2$. The response of NAD films increased from 1.4 to 6.0 simply by replacing part of the argon with helium, whereas GLAD films showed only a modest increase. The observed nanostructuring is discussed in terms of a simulation-supported growth scenario involving energetic backscattered He, a reduced hammering effect, and cooling-related suppression of adatom mobility, which together favour the formation of a more open sensing layer. Helium-assisted sputtering represents a useful physical route for tailoring
oxide thin films for gas-sensing applications.
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All authors Akash Kumar, Nirmal Kumar, David Kolenatý, Mina Farahani, Jiří Rezek, Tomáš Kozák, Stanislav Haviar
Mesoscale and Nanoscale Physics
One-dimensional carbon nanostructures with periodic graphitic nitrogen substitution
Nicolò Bassi, Shantanu Mishra, Zheng Zhang et al. (+8 more)
Heteroatom substitution is a powerful route to tune the chemical and electronic properties of carbon nanomaterials. In particular, replacement of an sp2 hybridized carbon atom in the
graphene lattice with a nitrogen atom (denoted as graphitic nitrogen) induces substantial changes in the electronic properties. These include changes in the band structure that can influence electronic transport, and magnetism. A key requirement for applications is both the periodic and precise incorporation of the heteroatoms in extended carbon
lattices. Here, we report the on-surface synthesis and characterization of two one dimensional carbon nanostructures, a
polymer and a
graphene nanoribbon, consisting of periodically incorporated graphitic nitrogen atoms. The on-surface reactions toward formation of the nanostructures were monitored by scanning tunneling microscopy. The bond-resolved chemical structures of the reaction intermediates and products were investigated by atomic force microscopy, which enabled atomic-scale visualization of the graphitic nitrogen sites. The electronic properties of the nanostructures were studied by scanning tunneling spectroscopy and density functional theory calculations. Our analyses revealed the presence of localized nitrogen-centered electronic states. In the gas phase where the nanostructures are in a neutral charge state, these states undergo
spin polarization leading to an open-shell ground state. Upon adsorption on Au(111), the nanostructures exhibit electron transfer to the surface, which resulted in a closed-shell ground state. Our results demonstrate a straightforward and generally applicable route to synthesize graphitic nitrogen-substituted carbon nanomaterials with potential applications in spintronics, catalysis and energy storage.
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All authors Nicolò Bassi, Shantanu Mishra, Zheng Zhang, Xiao-Ye Wang, Feifei Xiang, Nils Krane, Carlo A. Pignedoli, Klaus Müllen, Pascal Ruffieux, Akimitsu Narita, Roman Fasel
Materials Science
NanoBTE: Fast Iterative Solution of the Phonon Boltzmann Transport Equation for Nanoscale Heat Transport
Hongjiang Chen, Hai-Xuan Lin, Xiaole Tian et al. (+7 more)
Nanoscale heat dissipation has become a critical challenge in advanced
semiconductor devices, where
phonon transport can strongly deviate from the classical
Fourier description due to the boundary scattering and ballistic effects. In this work, we propose NanoBTE, a deterministic finite-volume solver for the non-gray
phonon Boltzmann transport equation under the relaxation-time approximation. The solver supports complex two- and three-dimensional geometries, band-resolved
phonon properties, discrete-ordinates angular quadrature, volumetric heat generation, and multiple
phonon boundary conditions, including thermalizing, diffuse, and specular reflections. %To improve the efficiency of multiscale simulations, both sequential and synthetic iterative schemes are implemented, where the latter couples the microscopic
phonon transport equation with a macroscopic
diffusion-type temperature equation to accelerate convergence in near-diffusive regimes. Both sequential and synthetic iterative options are implemented for the steady-state solution. Furthermore, NanoBTE adopts a band-direction task decomposition strategy, enabling efficient MPI-based CPU parallelization and GPU acceleration of the dominant sparse transport operations.
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All authors Hongjiang Chen, Hai-Xuan Lin, Xiaole Tian, Hongyu Chen, Juan Zhang, Shengyao Yan, Hezhu Shao, Yu Wu, Junjie Liu, Hao Zhang
Materials Science
Data-driven multi-objective optimization for alloy recycling using factorization machines and quantum annealing
Thomas Plehn, Katrin Bugelnig, Silvana Tumminello et al. (+2 more)
Quantum annealing has the potential to provide practical
quantum advantage for complex optimization tasks. Here, we present a systematic assessment of an integrated factorization-machine and
quantum-annealing workflow (FM+QA) for a technologically relevant application: multi-objective Pareto optimization in metal up-cycling through
alloy design. To address the non-convex nature of the Pareto front, we employ the recently proposed data-driven Tchebycheff scalarization (DDTS) scheme. Our results show that FM+QA extends the applicability of QUBO-based optimization to data-driven materials discovery problems with multiple competing objectives. In particular, we analyze the scaling behavior of the approach and compare
quantum annealing with classical simulated annealing using both regular binary encoding and one-hot encoding. Finally, we provide a critical perspective on the problem sizes and encoding strategies for which
quantum-annealing-based optimization may become practically beneficial in the near future.
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All authors Thomas Plehn, Katrin Bugelnig, Silvana Tumminello, Daniel Barragan-Yani, David Melching
Statistical Mechanics · Cross-listed from physics.optics
Griffiths Anomalous Absorption in Sparse-Loss Photonic Lattices
Stefano Longhi
Light absorption in photonic
lattices with sparsely distributed loss sites exhibits behavior analogous to Griffiths physics. Under uniform excitation, the transmitted power shows a stretched-exponential decay and a non-monotonic dependence on the loss strength, with an optimal loss rate that maximizes absorption. This behavior arises from rare, long loss-free segments that act as weakly coupled, long-lived photonic channels, rather than from exceptional point physics or interference effects. Using a minimal tight-binding model with binary quenched dissipation, we show that rare regions produce a universal Griffiths-type subexponential decay. Sparse-loss photonic
lattices thus provide an accessible platform to observe disorder-induced anomalous absorption and rare-region Griffiths physics.
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Quantum Gases
Effective potentials for polar molecules under non-orthogonal dual microwave fields
Fulin Deng, Xinyuan Hu, Su Yi et al. (+1 more)
Dual-microwave shielding has emerged as a powerful tool for stabilizing ultracold polar molecules while tuning their intermolecular interactions. However, the two microwave fields are generally not perfectly orthogonal in experiments. Such misalignment introduces an in-plane component of the linearly polarized microwave, whose frequency differs from that of the elliptically polarized field. This component prevents complete cancellation of the dipole-dipole interaction and, more critically, renders the single-molecule dressed state intrinsically time-dependent, so that the conventional time-independent scattering framework is no longer available. Here we develop a Floquet theory that yields an analytic effective potential and enables accurate scattering calculations for polar molecules in non-orthogonal dual microwave fields. We find that, though misalignment weakens the shielding moderately, inelastic losses remain strongly suppressed under experimentally relevant conditions. Meanwhile, misalignment provides additional tunability of the interaction anisotropy and strength, which has been directly applied to recent experimental observations on the gas-to-droplet transition~[Z. Shi et al, arXiv:2508.20518 (2025)] and
Fermi-surface deformation in microwave-shielded molecular gases~[S. Biswas et al, arXiv:2602.22447]. The framework is not restricted to dual-microwave shielding and can be generalized straightforwardly to arbitrary multi-frequency driving, providing a versatile tool for manipulating ultracold polar molecules under complex microwave configurations.
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All authors Fulin Deng, Xinyuan Hu, Su Yi, Tao Shi
Materials Science
Martensitic Transformation in Crystal-Amorphous Superlattices of NiTi Shape Memory Alloy
Bhavna Singh and Shivam Tripathi
Shape
memory alloys (SMAs) exhibit unique thermo-mechanical properties arising from reversible martensitic transformation. Tailoring these properties through coherent second phases is effective but is often limited by the difficulty of identifying thermodynamically compatible phases.
Crystal-amorphous superlattices (CAS), in which the second phase is derived from the base material itself, provide an attractive alternative. However, the influence of partial amorphization on martensitic transformation and thermo-mechanical behavior remains largely unexplored. Here, large-scale molecular dynamics simulations are used to investigate temperature- and stress-induced martensitic transformations in CAS-NiTi with different crystalline phase fractions. Partial amorphization fundamentally modifies the transformation pathway, introducing an initial continuous (second-order-like) transformation before the conventional first-order martensitic transformation. The amorphous phase also enhances transformation reversibility, reducing the thermal hysteresis from 275 K in fully crystalline NiTi to 95-110 K in CAS-NiTi. Simultaneously, the elastic modulus and the critical stress for stress-induced martensitic transformation increase by approximately 60-90 percent, depending on the crystalline fraction. These improvements originate from heterogeneous nucleation at
crystal-amorphous interfaces, retained austenite that promotes the reverse transformation, and mechanical constraint imposed by the amorphous phase. These findings establish
crystal-amorphous superlattices as a promising microstructural design strategy for tailoring the thermo-mechanical performance of shape
memory alloys.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Geometric modulation of transition and survival intensities in non-Hermitian systems
Ryu Frieson, Takashi Oka and Hideaki Obuse
The time
evolution of non-Hermitian systems is generally nonunitary. Dynamics governed by time-dependent non-Hermitian
Hamiltonians lead to a variety of novel phenomena, one of which is state amplification or suppression induced by the complex Berry phase. Here, we extend the framework of
geometric modulation to multi-level systems and show that both transition and survival intensities can be modulated. We apply our theory to the non-Hermitian Landau-Zener (LZ) problem. First, we show that, in the half-LZ problem, both the transition and survival probabilities exhibit nonreciprocity due to the complex Berry phase. In the non-Hermitian standard LZ problem, only the survival intensity is known to exhibit nonreciprocity, whereas the transition intensity does not. However, the physical origin of this nonreciprocal behavior remains unclear. In this work, we show that the nonreciprocity originates from the complex Berry phase.
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Statistical Mechanics
Finite-Time Thermodynamics of Battery Discharging: Power-Efficiency Trade-Off and Optimization
Rui-Han Liu, Yun-Qian Lin and Yu-Han Ma
Battery discharging is governed by a fundamental trade-off between output power and energy conversion efficiency due to internal dissipation. In this paper, we demonstrate that such a trade-off universally yields a
parabolic envelope $P\propto\eta(1-\eta)$. The efficiency at maximum power is exactly one half, mirroring the well-known half-Carnot limit in finite-time thermodynamics. To extend this bound into practical operational rules, we formulate a multistage constant-current discharging (MSCD) schedule subject to simultaneous real-time load demands and a global discharging deadline. Analytical resolution via the Karush–Kuhn–Tucker conditions reveals a remarkably compact optimal policy: $I_{i}^{\star}=\max(I_{i}^{-},I_{0})$. Under this rule, stages limited by external demand run exactly at their minimum required currents, while all remaining stages are elevated to a uniform baseline $I_{0}$ fixed by the deadline constraint. By tracing the dissipation–time Pareto front, we quantify how internal resistance shifts the operational boundaries and sharpens the trade-off corner. This analysis establishes a rigorous thermodynamic baseline for the scheduling layer of battery management systems, offering natural extensions to nonlinear models incorporating temperature and state-of-charge dependencies.
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Mesoscale and Nanoscale Physics
Comparative Evaluation of Encapsulation Methods for Endohedral Doping of Single-Wall Carbon Nanotubes
Cristian M. Borja-Peña, Martin Magg, Hussein Slim et al. (+10 more)
Single wall carbon nanotubes (SWCNTs) are promising building blocks for nanoelectronic and optoelectronic devices, yet reliable and stable doping, particularly n type, remains challenging due to strong environmental sensitivity and competing extrinsic effects. Encapsulation of charge transfer molecules within the SWCNT cavity offers a promising route to stable doping while preserving the nanotubes outer surface for subsequent processing. Here, we systematically investigate the filling of arc discharge SWCNTs with the electron donor tetrathiafulvalene and electron acceptor tetracyanoquinodimethane, comparing different methods for filling, including melt filling, solution reflux, and
vacuum phase sublimation. We follow the entire processing workflow from raw, unfilled powders to aqueous dispersions and employ density gradient ultracentrifugation to separate filled from empty nanotubes as well as metallic from semiconducting ones. Encapsulation efficiency and electronic modification are assessed using absorption spectroscopy, resonant Raman scattering, thermogravimetric analysis, X-ray photoelectron spectroscopy and electron paramagnetic resonance. Finally, we introduce a complementary
vacuum-phase method that removes externally adsorbed molecules without extensive solvent washing, enabling cleaner encapsulated systems.
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All authors Cristian M. Borja-Peña, Martin Magg, Hussein Slim, Yamaldi M. Bakary, Timm Swoboda, Cedric Desroches, Denys Kurylo, Kazuhiro Yanagi, Marianna Sledzinska, Benjamin S. Flavel, Salomé Forel, Wim Wenseleers, Sofie Cambré
Materials Science
Self-Driven Atomic Dispersion in Graphitic Layers
Zhaoxi Chen, Yulu He, Zhuoran Yao et al. (+9 more)
Carbon-supported single-atom catalysts maximize metal utilization, but how metal nanoparticles transform into isolated atoms within carbon remains unclear. We show that metal nanoparticles can undergo a self-driven dispersion process under hydrocarbon oxidation conditions, transforming into single atoms that are confined in carbon
matrix. Using Pt-catalysed hydrocarbon oxidation as a model, we combine operando electron microscopy, near-ambient-pressure X-ray photoelectron spectroscopy and mass spectrometry to track coupled structural and chemical
evolution. Graphitic carbon grows at step edges of Pt nanoparticle, continuously reconstructing Pt surface and generating undercoordinated sites for atom release. In-situ generated CO accumulates at the metal-carbon interface, weakening bonding and facilitating self-amplified atom release and migration. Defective carbon overlayers then trap, stabilize and transport liberated atoms, while oxidative etching preserves interfacial access of reaction-gas. Similar behaviour across other metals suggests a general atomization pathway for single-atom catalyst synthesis, yielding products with electrocatalytic hydrogen production activity beyond standard commercial
benchmarks.
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All authors Zhaoxi Chen, Yulu He, Zhuoran Yao, Jian Liu, Jun Cai, Ziyi Fan, Wenjun Zhang, Lei Lei, Zupeng Chen, Bo Yang, Zhi Liu, Zhu-Jun Wang
Mesoscale and Nanoscale Physics
Substrate-Mediated Persistent Photodoping in WSe2/hBN Field-Effect Transistors Enabled by Defect States in SiO2
Sung-Ha Kim, Seong-Yeon Lee, Tae-Jeong Kim et al. (+6 more)
Photodoping plays an important role in determining the optoelectronic response of two-dimensional
semiconductor devices; however, the origin of the responsible trap states remains unclear. In this work, we investigate UV-induced photodoping in multilayer WSe2 field-effect transistors (FETs) based on WSe2/hBN
heterostructures on SiO2/p-Si substrates. Wavelength-dependent measurements reveal pronounced n-type photodoping under 405 nm illumination, whereas the effect is orders of magnitude weaker under 640 nm excitation and for p-type photodoping. Furthermore, when the SiO2 layer is removed, both n-type and p-type photodoping are strongly suppressed, demonstrating that the
oxide layer is essential for persistent photodoping. Analysis of defect-state distributions in amorphous SiO2, together with first-principles calculations for hBN defects, shows that the experimental observations cannot be explained by defects in hBN. Instead, the results indicate that defect states in the SiO2 substrate act as charge reservoirs that facilitate charge transfer and long-term carrier trapping. These findings highlight the dominant role of substrate-related trap states in UV-induced photodoping and photogating behavior in WSe2 FET devices.
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All authors Sung-Ha Kim, Seong-Yeon Lee, Tae-Jeong Kim, Beomkyu Shin, Young-Jun Yu, Kenji Watanabe, Takashi Taniguchi, Soungmin Bae, Ki-Ju Yee
Strongly Correlated Electrons
Winding charge density wave: intertwining of structural chirality and phase topology of electronic order
Shun Asano and Youichi Yanase
We propose a class of
chiral charge density waves (CDWs), dubbed winding CDWs, that exhibit macroscopic chirality despite a single ordering wavevector. In screw-symmetric
chiral crystals,
chiral phonons drive a Peierls instability that selects a definite
crystal angular momentum channel, thereby endowing the CDW with an integer azimuthal phase winding dictated by the selection rule governing electron-
phonon coupling. We further extend this framework to achiral
crystals with discrete rotational
symmetry and demonstrate that spontaneous
symmetry breaking stabilizes a winding CDW with either handedness, realizing an achiral-to-
chiral phase transition. Our results reveal a fundamental link between the geometry of
chiral structures and the phase
topology of electronic orders.
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Strongly Correlated Electrons
Quantum magnetism of the spin-1 kagome-lattice antiferromagnet
Katsuhiro Morita
We investigate the
spin-1 kagome-
lattice Heisenberg antiferromagnet using large-scale Lanczos diagonalization and the finite-temperature Lanczos method. The zero-temperature magnetization process exhibits plateaus at $m=0$, $1/3$, $7/9$, and $8/9$, where $m$ is the normalized magnetization. The $m=0$ plateau is identified as a trimer valence-bond-
crystal state, while the high-field plateaus at $m=7/9$ and $8/9$ are identified as
magnon crystals. In particular, the $m=8/9$ plateau corresponds to the exact localized-
magnon crystal state. A smoothed zero-temperature magnetization curve constructed using the Gaussian-kernel smoothing method indicates magnetization jumps at the lower-field edge of the $m=1/3$ plateau and at the upper-field edges of the $m=7/9$ and $8/9$ plateaus. At finite temperatures, the specific heat exhibits a double-peak structure with peaks around $T/J\simeq0.1$ and $T/J\simeq1.1$, and the low-temperature peak may be related to trimer valence-bond-
crystal ordering. The finite-temperature magnetization curves show that the $m=1/3$ plateau remains visible at low temperatures, whereas the high-field plateaus are rapidly smeared out by thermal effects. These results provide
benchmark data for thermodynamic and high-field magnetization measurements in candidate
spin-1 kagome-
lattice materials.
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Mesoscale and Nanoscale Physics
Effects of Impurity Scattering on Orbital Hall Conductivity and Orbital Transport in Ru-based Alloys
Yumin Yang, Yanxu Chen, Wenqi Xu et al. (+1 more)
The role of
impurity scattering in the generation and transport of orbital current remains less established than in conventional
spin Hall systems. Here we investigate Ru-based nonmagnet/ferromagnet
bilayers in which the
impurity scattering is tuned by Cu or Ti alloying. According to SOT measurement and thickness-dependent drift-
diffusion analysis, we extract the effective orbital
Hall conductivity and the orbital
diffusion length. We find that the orbital
Hall effect in polycrystalline Ru is dominated by intrinsic mechanism that is moderately robust against weak disorder but suppressed by stronger
alloy disorder. However, the orbital
diffusion length remains nearly unchanged at approximately 14 nm over the investigated
impurity range. This behavior indicates that orbital transport is not governed simply by an
impurity scattering. Together with previous temperature-dependent measurements, our results show that static
impurities and dynamic
lattice disorder affect orbital transport through distinct microscopic channels. These results provide new insight into how disorder governs orbital generation and transport, and offer experimental guidance for developing high-efficient orbitronic materials.
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All authors Yumin Yang, Yanxu Chen, Wenqi Xu, Dahai Wei
Materials Science
Chiropiezoelectric Energy Harvesting from Lattice-Handedness-Controlled Selenium Nanowires
Oleksii Ohiienko, Wookjin Jung and Jihyeon Yeom
The growth of wearable electronics, soft robotics, and Internet-of-Things systems has intensified the demand for inorganic piezoelectric materials that harvest weak biomechanical energy. Advances through composition optimization, defect engineering, strain engineering, and orientation control have improved existing electromechanical responses, but have not introduced a new mechanism for enhancing piezoelectricity. Here we propose atomic chirality engineering as a design principle for inorganic piezoelectric nanomaterials. Unlike conventional strategies that modify composition or morphology, atomic chirality alters the handedness of the
crystal lattice itself, adding a degree of freedom for controlling dipole
alignment, electromechanical coupling, and potentially
spin-dependent transport. Using atomically
chiral trigonal selenium nanowires as a model system, we show that
crystal handedness alone changes piezoelectric performance at identical chemical composition. Piezoresponse force microscopy resolved a consistent enantiomeric difference, with right-handed D-Se nanowires reaching a higher effective piezoelectric coefficient than their left-handed counterparts, and flexible nanogenerators and self-powered acoustic sensors built from the two enantiomers produced distinct outputs under identical deformation. This work establishes atomic chirality as a distinct route for designing piezoelectric materials, one that may extend across non-centrosymmetric inorganic
semiconductors for sustainable energy harvesting and wearable sensing.
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Statistical Mechanics · Cross-listed from cs.LG
Out-of-distribution Neural Inference in Dynamical Ising Models
Yuan-Bin Zhu, Shuang Qiao and Shi-Ju Ran
Neural networks are increasingly used to infer hidden physical structure from dynamical observations, yet it remains unclear whether their out-of-distribution performance reflects transferable physical rule learning. We address this question in a controlled inverse problem: reconstructing interaction graphs of a kinetic Ising model from Glauber magnetization trajectories. Across convolutional, graph,
Transformer, and hybrid architectures, we find that data-driven training produces distinct and reproducible statistical strategies under
topology and temperature shifts. Edge-population diagnostics reveal that
Transformer-based models tend to preserve the link density of the training ensemble, whereas convolutional models can collapse toward sparse- or no-link predictions that appear out-of-distribution stable by exploiting the majority no-link class. Thus, high in-distribution accuracy and apparent out-of-distribution robustness do not necessarily imply a learned dynamics-to-structure rule. Instead, neural reconstruction can be governed by architecture-dependent statistical priors. Our results identify a concrete failure mode of standard data-driven learning in physical inverse problems and motivate rule-guided principles for machine-learning-assisted scientific discovery.
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Soft Condensed Matter
Entropy functional universality: Correlation, response, many-body interaction, multi-component, quantum, hyperfunctional, and Ornstein-Zernike structure
Matthias Schmidt
We give a comprehensive account of the recent
entropy functional theory for the
equilibrium statistical mechanics of classical many-body systems (arXiv:2606.28240). The approach is formally exact and based on a joint grand potential minimization principle for the one-body density and the global pair distance distribution. These variational fields depend respectively on position and on scalar distance, which retains the low computational complexity of standard density functional theory. Correlation effects are contained in a unique excess
entropy functional, which is universal across all systems with pairwise interparticle potentials. Functional differentiation yields entropic direct correlation functionals that generate entropic response and fluctuation correlation functions via coupled Ornstein-Zernike equations. Two alternative proofs are given for the existence and uniqueness of the underlying metadensity functional map, based on generalizations of either Levy's constrained search method or Mermin-Evans proof by contradiction. Simple excess
entropy approximations yield the standard mean-field and second-virial excess free energy density functionals. We describe exact entropic functional line integrals, make connections to the recent one-body fluctuation profiles, and generalize the
entropy approach beyond pairwise interparticle potentials via parametric dependence or reduction operators. We also lay out the formulation for multi-component systems, the hyperfunctional for general observables, and the
quantum entropy functional.
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Superconductivity
When Repulsion Creates Pairing: A New Perspective on Unconventional Superconductivity
Patrick Navez
Despite the repulsive Coulomb law and the Pauli statistics that do not favor bound states, attraction between electrons or holes is nevertheless possible in the context of many body interaction and of valley potential landscapes, reminiscent of exotic superconducting materials. In particular, in 1965, Kohn and Luttinger published a note revealing that the dynamical screening of the repulsive Coulomb interaction leads, under certain conditions, to an effective attraction necessary for the formation of Cooper pairs. We propose such a formalism adapted to the cuprates, where the screening arises from the superexchange dynamics of virtual holes in the oxygen orbitals of the $Cu O_2$ plane. Inspired from the Bardeen-Copper-Schrieffer (BCS) theory, we can derive some predictions for the temperature-doping phase diagram (pseudo-gap, strange metal, antiferromagnetism, superconducting, and normal states) in semi-quantitative agreement with observations.
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