Statistical Mechanics
Kink-kink correlations in nonlinear quenches across a quantum critical point
Lakshita Jindal and Kavita Jain
When a
quantum system exhibiting a second order phase transition is quenched across the critical point in large but finite time, the dynamics are not adiabatic in the critical region and the Kibble-Zurek (KZ) mechanism provides a framework to determine local observables such as the mean defect density. However, to find higher-point functions, one has to go beyond the KZ paradigm asshown in recent works on one-dimensional transverse field Ising model (TFIM) following a linear quench. It has been found that (i) besides the KZ scale, the quench dynamics depend on another length scale that arises due to the finite phase difference between the low energy modes, and (ii) contrary to the expectations based on the KZ mechanism, in general, the correlation functions do not decay exponentially with distance. Motivated by these results for the linear quench, we are interested in understanding if these properties are universal, and consider the 1D TFIM when the transverse field varies algebraically in the vicinity of the critical field. We focus on the equal-time,longitudinal kink-kink correlation function at the end of the quench from the paramagnetic to the
ferromagnetic phase, and find that (i) the correlator depends only on the KZ length for superlinear quenches, otherwise an additional dephasing length is required to describe it, and (ii) the dephased correlator decays as a compressed exponential with an exponent that changes continuously with the quench exponent. Our results are obtained using an adiabatic perturbation theory, analytical arguments and exact numerical integration of the relevant equations.
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Materials Science
Diversity-Aware Active Learning Builds Materials Datasets for Current and Future Objectives
Rafael Espinosa Castañeda, Ashley Dale, Hongchen Wang et al. (+6 more)
Materials science data collection can be expensive, making
dataset reuse and long-term utility important for future discovery. In practice, data collection often prioritizes properties of current interest while other properties are excluded from the acquisition process. This can produce
datasets that are well suited for current objectives but lose information needed for properties of future interest. Here, we present how to construct
datasets that remain informative for both. We develop and evaluate acquisition frameworks that combine predictive disagreement with diversity in material features, predicted outcomes, or both. We test these approaches across four DFT
datasets and an experimental thermoelectric
dataset. Diversity inclusion in
dataset construction can reduce present and future objectives trade-off by preserving a broader range of materials and property behavior during acquisition. Across all
datasets, the Non-dominated Sorting Genetic
Algorithm II with disagreements and feature diversity (NSGA-II Dis. + diversity) framework developed in this work provides the most robust balance between current and future objectives. It maintains prediction performance above random sampling for current objectives while mitigating bias on excluded properties and, in many cases, improving their performance beyond random sampling. This diversity-aware acquisition framework provides a practical route to building materials
datasets with unbiased quality entries and mitigating cold-start limitations in subsequent modeling and discovery campaigns.
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All authors Rafael Espinosa Castañeda, Ashley Dale, Hongchen Wang, Yonatan Kurniawan, Hao Wan, Runze Zhang, Adji Bousso Dieng, Kangming Li, Jason Hattrick-Simpers
Strongly Correlated Electrons
Microscopic evidence for imaginary charge density wave in a kagome metal
S. Suetsugu, F. Hori, M. Shibata et al. (+9 more)
Dissipationless charge transport without any energy loss is one of the most fascinating phenomena in condensed matter physics. This extraordinary state manifests in two well-established systems:
superconductors and
quantum Hall systems. A proposed third category is associated with
chiral loop current order, characterized by the spontaneous formation of microscopic electric current loops. The microscopic origin of these currents stems from imaginary hopping terms, conceptualized as an imaginary charge density wave (iCDW). Despite extensive investigations, its existence remains highly controversial. Here we report site-selective spectroscopic evidence for a pure iCDW in the kagome nonmagnetic metal CsV$_3$Sb$_5$.
Nuclear quadrupole resonance spectra at out-of-plane $^{121}$Sb site sensitive to in-plane currents reveal anomalous broadening below $T^*\approx$120 K, coinciding with the nematic transition well above the real charge density wave (CDW). Under
magnetic fields, the spectra exhibit asymmetric lineshapes, demonstrating that this broadening purely originates from
magnetic effects rather than from electric quadrupolar effects associated with CDW fluctuations. The observed lineshapes are quantitatively consistent with ~1 mT local fields induced by
chiral loop currents, indicating spontaneous time-reversal
symmetry breaking. This microscopic identification of the long-sought pure iCDW establishes a novel form of
quantum order, potentially revolutionizing our understanding of exotic electronic states in
quantum materials.
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All authors S. Suetsugu, F. Hori, M. Shibata, S. Kitagawa, K. Ishida, T. Asaba, S. Nakazawa, Q. Li, H. -H. Wen, T. Shibauchi, H. Kontani, Y. Matsuda
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Planar chiral nanoantenna for excitation-chirality-controlled hot spot modulation and emitter-coupled circularly polarized emission
Abhik Chakraborty, Xiaofei Wu, Ankit Kumar Singh et al. (+5 more)
A planar
chiral plasmonic nanoantenna exhibiting an excitation-chirality-dependent hot spot in a nanogap is numerically investigated. Additionally, the underlying design principles are examined, providing a broadly applicable framework for engineering
chiral nanoantennas through controlled geometrical or modal asymmetry. The hot spot can be turned on and off by changing the handedness of the exciting circularly polarized light (CPL). This effect stems from the rationally designed interference of plasmonic modes excited by the linearly polarized orthogonal components of CPL. The hot spot exhibits maximal near-field dissymmetry factor (about -2) at a wavelength of 842 nm. The intensity at the hot spot can also be continuously modulated by varying the excitation ellipticity and handedness, approaching a modulation depth of 100%. These attributes enable chirality- and ellipticity-dependent switching and dynamic modulation of the plasmonic near field. Moreover, placing a
quantum emitter in the gap generates almost perfectly circularly polarized emission, offering a simple yet effective avenue to realize nanoscale circularly polarized single-
photon sources.
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All authors Abhik Chakraborty, Xiaofei Wu, Ankit Kumar Singh, Fabian Scheidler, Min Jiang, Jürgen Popp, Bert Hecht, Jer-Shing Huang
Strongly Correlated Electrons
Interaction-controlled localization in one-dimensional chain: From edges to domain walls
Rahul Samanta, Sudin Ganguly and Santanu K. Maiti
Using Hartree-Fock mean-field approach, we study the role of on-site ($U$) and extended ($V$) Hubbard interactions on the existence and
evolution of edge modes in a half-filled Su-Schrieffer-Heeger (SSH) chain. We analyze the energy spectrum, local probability amplitudes, and site-resolved charge and
spin density profiles across topological, critical, and trivial hopping regimes. We find that the localization of bound states is controlled by the ratio $2V/U$, with edge
spin-density-wave modes for $U>2V$ and mid-chain charge-density-wave domain walls for $U<2V$, independent of band
topology. These results establish the correlation-driven origin of localized states in finite one-dimensional chains.
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Statistical Mechanics
Nonequilibrium Fluctuation-Response Theory in the Frequency Domain
Euijoon Kwon, Hyun-Myung Chun, Hyunggyu Park et al. (+1 more)
We establish a unified fluctuation-response theory in the frequency domain for nonequilibrium steady states governed by overdamped Langevin dynamics and Markov jump processes. The central identity is an exact fluctuation-response relation that reconstructs the power spectrum of general observables from local responses measured at the same frequency. This relation applies to state-dependent observables, current-like observables, and their combinations, and reveals how local dynamics shape global fluctuations. From this identity, we derive a hierarchy of relations in the frequency domain, including response uncertainty relations, kinetic and thermodynamic uncertainty relations, the
equilibrium fluctuation-dissipation
theorem, and Harada-Sasa relations. This establishes an overarching framework for fluctuation-response theory in the frequency domain. Applications to
stochastic networks and driven diffusive systems demonstrate how the theory decomposes fluctuation spectra into local contributions and reveals frequency-dependent tradeoffs between fluctuations, response, and dissipation.
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All authors Euijoon Kwon, Hyun-Myung Chun, Hyunggyu Park, Jae Sung Lee
Materials Science
Uncovering hidden bias in neutron diffraction residual strain measurements
Cole Franz, Michael B. Prime, Jeffrey Bunn et al. (+2 more)
When calculating residual strain via
neutron or X-ray diffraction, uncertainties propagated from the peak fit are often inadequate to describe the true scatter of measurements about a singular strain state, such as one that should describe a macroscopic continuum. Because diffraction is inherently a selective process, orientation dependent scatter arises from the sub-sampling of strong microstructure and strain gradients. This paper investigates the appropriateness of propagated uncertainties with reference to their original intention, i.e., noise about a mean value. Thirty-six unique orientations of strain measurements are taken at multiple locations within an additive friction-stir deposition component with fine-scale gradients (~200 um) of plastic strain, texture, and residual elastic strain. Multiple strain and stress calculation pathways are compared: direct substitution of three measurements into Hooke's law, direct inversion of any six unique orientations into the strain state tensor, and thirty-six measurement least-squares estimation. For the latter two cases, the appropriateness of the uncertainty interval is statistically evaluated based on a physical constraint: common agreement under the strain transformation law. For this sample, the direct inversion of six measurements retains a conservative estimate of the uncertainty. However, propagated uncertainties in the least-squares solution greatly underestimate the true experimental scatter. A simple pathway to estimate appropriate uncertainty intervals is suggested. These results demonstrate that interpretation of uncertainty in residual strain is strongly dependent on intrinsic, sample-dependent effects, and that oversampling orientations and statistical analysis can give more accurate results with realistic uncertainties.
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All authors Cole Franz, Michael B. Prime, Jeffrey Bunn, Andrew Payzant, Katharine Page
Quantum Gases
Geometrical control of topology with orbital angular momentum modes
Yunjia Zhai, Anselmo M. Marques, Ricardo G. Dias et al. (+2 more)
We study how the topological properties of a one-dimensional staggered
lattice, loaded into states with orbital angular momentum $l=1$, can be controlled simply by tuning the relative angle between sites. The original system under consideration can be depicted as a Creutz ladder model when unwrapping the different state circulations in a synthetic dimension. Depending on the hopping strengths of the chain, different topological regimes may be accessed by changing the ladder angle, as determined by the value of the winding number of the chain. We analytically and numerically explore the different available regimes, and determine the number of topologically protected edge states that exist in each case. We also study the emergence of band inversion across topological transitions and show that it agrees with the winding number calculations, thus serving as an additional topological marker. Then, we propose a realistic experimental implementation in a photonic waveguide system, where the topological transition manifests as a sudden change of the behavior of the propagation of light in the system.
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All authors Yunjia Zhai, Anselmo M. Marques, Ricardo G. Dias, Verònica Ahufinger, David Viedma
Soft Condensed Matter
Nonlinear phonon dispersion in disordered solids and non-Debye vibrational spectra
Edan Lerner and Eran Bouchbinder
All solids, whether crystalline or disordered, support elastic wave propagation with a linear dispersion relation in the long-wavelength limit. These waves, corresponding to low-frequency
phonons, feature a vibrational density of states that follows Debye's classical model. Deviations from Debye's predictions with increasing frequency can emerge from
phonon dispersion nonlinearity and from non-phononic vibrational modes, which exist in non-crystalline solids due to structural disorder. Both nonlinear
phonon dispersion in disordered solids and its relative contribution to non-Debye anomalies, most notably manifested by the controversial
boson peak, remain poorly understood. Here we show that nonlinear
phonon dispersion in a broad range of disordered solids, including elastic networks and various glasses, emerge from a mesoscopic, disorder-induced lengthscale, which also controls wave attenuation. We subsequently use analysis and large-scale computer simulations to quantitatively determine the relative contributions of nonlinear
phonon softening and non-phononic vibrations to the onset of non-Debye anomalies and to the
boson peak. We show that the relative magnitude of the two contributions strongly depends on the strength of disorder of the solid, e.g., controlled by the thermal history upon glass formation, and that for realistic laboratory glasses both pieces of physics significantly contribute to the
boson peak. These findings constitute basic progress in understanding disordered solids.
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Strongly Correlated Electrons
Symmetric estimator for discrete self-energy of discrete many-body systems
Aleksandrs Zacinskis, Frank T. Ebel, Mathias Pelz et al. (+5 more)
We derive a discrete spectral representation of the single-particle self-energy using a discrete evaluation of Kugler's symmetric improved
estimator. Our construction can be used on both the real and the complex (Matsubara) frequency axis. It is guaranteed to remain causal at the numerical level, in contrast to standard approaches that may generate unphysical negative spectral weight or require additional broadening. Our representation can be used for any
Hamiltonian; here we apply it to
quantum impurity models and in dynamical mean-field theory. The latter is formulated with a discrete hybridization function throughout its self-consistency loop. In both cases and across various numerical methods, we obtain significantly improved accuracy for a range of
impurity properties.
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All authors Aleksandrs Zacinskis, Frank T. Ebel, Mathias Pelz, Fabian B. Kugler, Karsten Held, Jan von Delft, Maurits W. Haverkort, Andreas Gleis
Materials Science
Temperature dependence of the Gibbs energies of formation of point defects in B2 MoTa from ab initio calculations
Xiang Xu, Fritz Körmann, Sergiy Divinski et al. (+2 more)
Using B2 MoTa, the strongest B2 former among group V/VI refractory binaries, as a model system, we compute temperature-dependent Gibbs energies of formation of vacancies and antisites from ab initio calculations up to 3000 K at the stoichiometric composition. We explicitly account for thermal electronic excitations, vibrational anharmonicity, and electron-vibration coupling. The key finding is that the temperature dependence of the Gibbs energies of vacancy formation exhibits a pronounced sublattice asymmetry. Specifically, the Gibbs energy of formation of a Mo-site vacancy decreases by 1.1 eV from 0 to 3000 K, whereas the decrease for a Ta-site vacancy amounts to 2.1 eV, almost a factor of two larger. Two contributions of distinct origin govern the temperature dependence of this asymmetry: a quasiharmonic contribution associated with the chemical-potential imbalance set by the two antisite structures and an anharmonic contribution associated with the local vibrational response of the vacancy structures. The asymmetry in anharmonic vibrations is traced back to an enlarged local vibrational distribution of the first-nearest neighbors around the Ta-site vacancy. In contrast to the vacancies, the Gibbs energies of antisite formation vary only weakly with temperature.
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All authors Xiang Xu, Fritz Körmann, Sergiy Divinski, Blazej Grabowski, Xi Zhang
Soft Condensed Matter · Cross-listed from physics.optics
Characterization of Photopolymerized Microscopic Chiral Structures Using Photonic Orbital Angular Momentum
Jing Xu, Rik Strobbe, Yovan de Coene et al. (+2 more)
The controlled fabrication and chiroptical characterization of microscale
chiral structures remain central challenges in photonics, sensing, and metamaterial engineering. Here we demonstrate an accessible, low-cost platform that combines digital micromirror device-enabled maskless photolithography with capillarity-induced self-assembly to produce
polymer chiral microstructures of deterministic handedness, and a
liquid-
crystal spatial light modulator to generate
vortex beams for their characterization via helical dichroism (HD). Using a standard 532 nm
laser, we observe HD signals of approximately 30% for microstructures with a characteristic diameter of about 15 micrometers. Rigorous finite-difference time-domain simulations performed on three-dimensional geometries reconstructed from high-resolution Scanning Electron Microscopy data reproduce the experimental HD spectra and confirm the role of structural handedness in driving the differential orbital angular momentum (OAM) response. Near-mirror-symmetric HD spectra for opposite-handed enantiomers, combined with a vanishing response for achiral controls, establish OAM as a robust and spatially selective
chiral probe at the microscale. Crucially, both fabrication and characterization rely on equipment standard in an optics laboratory, without recourse to femtosecond sources, plasmonic substrates, or costly photoresists. These results open practical pathways toward OAM-driven
chiral sensing, enantioselective detection, and photonic logic devices.
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All authors Jing Xu, Rik Strobbe, Yovan de Coene, Renaud A. L. Vallée, Koen Clays
Materials Science
From Defects to Devices: Design Guidelines for High-Performance Diamond-Based Solar Cells and Single-Dopant Diodes
Matúš Kaintz and Antonio Cammarata
This work establishes key technological guidelines for designing diamond-based optoelectronic devices, derived from a first-principles investigation of two architectures: a PIN junction with a boron-vacancy-boron (BVB) intermediate-band absorber, and a PN junction based on phosphorus-vacancy (PV) defects. For the PIN
solar cell, practical design principles include: i) aligning incident light in the xz-plane to exploit anisotropic absorption; ii) using graded junctions to mitigate tunnelling losses at abrupt interfaces; iii) targeting an absorber thickness of ~500 nm to balance absorption and carrier extraction; and iv) leveraging the high transparency of both contact layers for bifacial device configurations. For the PN diode, the PV-doped diamond operates via
impurity-band conduction, making it suitable for degenerate p-type applications such as tunnel diodes or asymmetric junctions, while its temperature-dependent Seebeck anisotropy and sign-reversal offer opportunities for thermal management applications. When paired with phosphorus-doped n-type regions, these defects enable single-dopant junctions that significantly simplify device manufacturing. Using density functional theory with GW corrections, Bethe-Salpeter equation calculations and carrier transport modelling coupled to device electrostatics via a Poisson solver, we show that the BVB defect introduces intermediate bands without degrading diamond's high carrier mobility or thermal conductivity, while PV-doping provides high conductivity at room temperature through
impurity-band transport. Overall, both defect-engineered systems preserve diamond's superior transport and thermal properties even after doping, offering viable pathways for high-performance diamond optoelectronics. These guidelines provide a practical foundation for fabricating efficient diamond-based photovoltaic and diode devices.
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Soft Condensed Matter
Local elastic perturbation of colloidal suspensions near the colloidal glass transition
Piotr Habdas, Rachel E. Courtland and Eric R. Weeks
Isolated microscopic
magnetic particles are used to induce local perturbations in dense colloidal suspensions by rotating an external magnet. Confocal microscopy enables tracking of both the
magnetic probe particle and adjacent colloidal particles. A probe particle moves with a circular trajectory. Knowing the external force and measuring the amplitude and phase of the probe motion allows us to infer the storage and loss
moduli of colloidal suspensions at various volume fractions. These measurements are in qualitative agreement with previous results from conventional rheology. To further analyze the system's response, the oscillatory amplitude of colloidal particles is evaluated as a function of distance from the probe, revealing a 1/r decay in amplitude, consistent with a homogeneous viscoelastic material. These observations confirm that continuum descriptions of the colloidal samples are effective down to length scales comparable to the particle diameter.
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Superconductivity
Symmetry-resolved superconducting diode response
Qiong Qin, Jie Wu and Congjun Wu
The superconducting diode effect manifests as nonreciprocal properties of critical currents, yet a systematic tensorial framework for its
symmetry-governed responses remains lacking. We develop such a framework by relating the angular harmonics of critical currents to the
magnetic field. Crystalline
symmetries constrain the dipolar response to be purely antisymmetric (
Hall-like) in Rashba
superconductors with $C_{3v}$, $C_{4v}$, or $C_{6v}$
symmetry, whereas they require a diagonal, traceless tensor in Dresselhaus
superconductors with $D_{2d}$
symmetry. For systems with fourfold
symmetry, the octupole response appears at linear order, whose response tensors take symmetric off-diagonal and identity forms for $C_{4v}$ and $D_{2d}$
symmetries, respectively. Furthermore, nematicity activates otherwise forbidden tensor components, providing a sensitive probe of rotational
symmetry breaking in
superconductors. At cubic order in the
magnetic field, the nonlinear response tensors likewise exhibit distinct
symmetry-dependent patterns. Our framework establishes a
symmetry-resolved characterization of the superconducting diode effect and provides a route to probing the underlying electronic structure and
symmetry-breaking orders.
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Materials Science
Efficient Quasi-Resonant, Polarization-Selective Excitation of GaN Quantum Emitters
Nilesh Dalla, Paweł Kulboka, Michał Kobecki et al. (+6 more)
Defect centers in GaN emerge as bright sources of single-
photons which recently have been demonstrated to optically interface a localized
spin. However, the structure and composition of these defects as well as their efficient excitation techniques were not a subject of thorough studies. This work presents evidence that by tuning the excitation
laser energy to specific resonance values the excitation efficiency can be enhanced, resulting in relative increase of photoluminescence intensity by up to an order of magnitude. The resonances can be selectively addressed with linearly polarized light, while the emission dipole remains unchanged, enabling polarization-controlled enhancement. These results establish an efficient way of excitation for GaN-based emitters, thereby increasing the generation rate of
photons. The data is consistent with excitation via localized vibrational modes associated with point-defect complexes, establishing a practical quasi-resonant route to brighter, polarization-addressable operation of GaN defect emitters and clarifying their energy-level structure.
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All authors Nilesh Dalla, Paweł Kulboka, Michał Kobecki, Jan Misiak, Paweł Prystawko, Tomasz Kazimierczuk, Piotr Kossacki, Henryk Turski, Tomasz Jakubczyk
Mesoscale and Nanoscale Physics
Guidelines for band gap opening in graphene superlattices with periodic {\pi}-vacancy distribution
Diyan Unmu Dzujah, Hongde Yu and Thomas Heine
Periodic $\pi$-vacancies in
graphene superlattices (GSLs) provide a
symmetry-based route to band-gap opening in
graphene by modifying the $\pi$-band dispersion. However, the
symmetry conditions that determine whether a vacancy motif can open a band gap remain unclear. Here, we investigate periodic $\pi$-vacancy GSLs using a nearest-neighbor tight-binding model with one $p_z$ orbital per carbon site to identify the
symmetry requirements for gap opening. $\pi$-vacancies, representing functionalized, substituted, or missing carbon sites, are modeled as site deletions in the $\pi$ basis, with all hopping
matrix elements to and from the deleted sites set to zero. We focus on $\pi$-vacancy motifs with $C_2$ and $C_3$ point-group
symmetry. A $3n \times 3n$ GSL, where $n=1,2,3,\ldots$ is the integer scaling factor multiplying the honeycomb primitive-
cell vectors, folds $K$ and $K'$ to $\Gamma$ and can therefore open a band gap. For $C_3$-type vacancies, the Dirac cones remain pinned at high-
symmetry points and thus stay at $\Gamma$ in folded $3n$ GSLs. In contrast, $C_2$-type vacancies that reduce the global point group of the GSL to $D_{2h}$ by preserving a pair of perpendicular mirror
symmetries, $\sigma_v \perp \sigma_d$, can also constrain the Dirac cones to $\Gamma$. When the $\sigma_v$ and $\sigma_d$ mirror planes are absent, the cones are allowed to shift away from $\Gamma$ to $(\pm \Delta q,\pm \Delta q)$ in the $3n$ superlattice.
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Mesoscale and Nanoscale Physics
Magnetic Brightening and Nanoscale Imaging of Spin-Polarized Helical Edge Modes
Samuel Haeuser, Richard H. J. Kim, Lin-Lin Wang et al. (+9 more)
Efficient sub-10 nm electric transport remains a major challenge for nanoelectronics due to high losses and impedance mismatches in conventional Drude metals. Despite their promise of dissipationless, reflection-free conduction, topologically protected
chiral edge modes remain little explored in their nanoscale
spin polarized transport-particularly regarding real-space visualization,
magnetic field tunability, and high-frequency edge conductivity. Here, we report
magnetic brightening and nanoscale visualization of highly
spin-polarizable infrared helical edge states using cryogenic magneto-infrared scattering-type scanning near-field optical microscopy (cm-IR-sSNOM). Our measurements reveal
magnetic field-induced near-field conductivity at step edges, uncovering
quantum spin Hall spin-splitting modes with enhanced infrared polarizability and slightly narrowed near-field profiles. In addition, the infrared edge electrodynamic response scales nearly linearly with atomic layer number, providing compelling evidence that
magnetic-field-induced gaps do not disrupt individual-layer edge states at energies of around 100 meV. These results sharply contrast with microwave and DC transport, where even small magnetically induced gaps decrease edge conduction. Magnetically tunable, topologically robust high-frequency edge modes open a pathway toward ultralow-loss nanoscale interconnects and
quantum logic architectures for next-generation microelectronics, spintronics and
quantum information science.
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All authors Samuel Haeuser, Richard H. J. Kim, Lin-Lin Wang, Thomas Koschny, Pedro M. Lozano, Genda Gu, Randall K. Chan, Joong-Mok Park, Martin Mootz, Liang Luo, Qiang Li, Jigang Wang
Soft Condensed Matter
Understanding the Dynamics of Evaporation-Driven Colloidal Self-Assembly
Junyu Yang, Abhinav Naga, Xitong Zhang et al. (+1 more)
Complex colloidal cluster morphologies are desirable for the fabrication of advanced materials, such as photonic
crystals and meta-materials, and can be formed through evaporation-driven packing. By coupling
lattice Boltzmann and discrete element methods, here we elucidate the rich interplay between fluid and particle dynamics during evaporation-driven self-assembly of spherical colloidal particles. We construct a regime diagram for a wide range of evaporation rates, interparticle friction coefficients, and particle numbers, identifying parameter regimes for open, closed, and minimal moment of inertia cluster configurations. Analyzing the competition between capillary, hydrodynamic, normal, and friction forces, we show that interparticle friction can exert a disproportionately strong influence on the final packing outcome despite being considerably smaller in magnitude than other forces at play. Our simulation results further highlight the potential for tuning colloidal cluster configurations via their dynamic trajectories.
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All authors Junyu Yang, Abhinav Naga, Xitong Zhang, Halim Kusumaatmaja
Soft Condensed Matter · Cross-listed from physics.optics
Band-Selective LDOS Engineering of Yb/Er Upconversion: an Electromagnetic-Kinetic Diagnostic Framework
Yuxiang Zhang, Mayte Gómez-Castaño, Agustín Mihi et al. (+3 more)
A persistent challenge in plasmonic upconversion is decoupling pump-field enhancement from emission-side local-density-of-optical-states (LDOS) engineering to achieve selective band manipulation. Here, we show that a corrugated SU8/Au/Al2O3 grating coated with a NaYF4:Yb/Er upconversion nanoparticle (UCNP) monolayer realizes a truly band-selective platform. A broad plasmonic resonance near 670 nm modulates the red Er 3 + 3+ decay rate by $\pm$15% as a function of the Al2O3 spacer thickness, while leaving the green transition experimentally invariant (< 1% change). Simultaneously, the 980 nm pump field is monotonically suppressed below free-space levels, ensuring that steady-state and time-resolved observables cleanly probe the emission-side LDOS without pump interference. We analyze this system using a coupled electromagnetic-kinetic framework that integrates finite-difference time-domain (FDTD) calculations of Purcell factors and pump fields with a six-level Yb/Er rate-equation model. The framework quantitatively reproduces the 670 nm plasmonic resonance, the red-band decay-rate modulation, and the monotonic decrease of the green/red intensity ratio. Crucially, the model serves as a powerful diagnostic tool: it overpredicts a green-band rate reduction, but systematic parametric testing rules out
geometric (apex smoothing) and material (grain-boundary damping, interband loss) imperfections as the cause. Instead, it isolates the residual discrepancy to measurement-versus-model factors (finite-aperture angular averaging) and missing non-radiative kinetic channels, establishing a clear roadmap for the rational design and validation of future plasmonic-UCNP architectures.
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All authors Yuxiang Zhang, Mayte Gómez-Castaño, Agustín Mihi, Serge Ravaine, Xiaogang Liu, Renaud A. L. Vallée
Materials Science
A Two-Step Chemical Vapor Deposition Process for the Synthesis of an Ir(111)/Borophene/2D-Hexagonal Boron Nitride Heterostructure by Intrinsic Segregation
Marko A. Kriegel, Karim M. Omambac, Smruti R. Mohanty et al. (+10 more)
We report on a two-step ultrahigh
vacuum chemical vapor deposition synthesis of a vertical Ir(111)/borophene/hexagonal boron nitride
heterostructure, using borazine as a single-source precursor. The process takes advantage of the finite solubility of boron in Ir: low precursor pressure at high temperature first establishes a boron reservoir in the near-surface region of the substrate, whereas subsequent growth at higher precursor pressure promotes the formation of a closed hexagonal boron nitride monolayer. During cooldown, the reduced boron solubility drives segregation to the surface, resulting in the formation of a borophene monolayer beneath the hexagonal boron nitride overlayer. The
heterostructure, with micron sized grains, homogeneously covers the entire Ir substrate. The study is performed by complementary spot profile analysis low-energy electron diffraction, low-energy electron microscopy, and scanning tunneling microscopy measurements. This intrinsic segregation-assisted growth concept provides a promising route toward scalable synthesis of high-quality, vertical
heterostructures of two-dimensional materials.
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All authors Marko A. Kriegel, Karim M. Omambac, Smruti R. Mohanty, Tobias Hartl, Stefan Schulte, Niels Ganser, Pascal Dreher, Alexandra Rödl, Steffen Franzka, Germán Sciaini, Thomas Michely, Frank-J. Meyer zu Heringdorf, Michael Horn-von Hoegen
Materials Science · Cross-listed from physics.optics
Unraveling the Defect Physics of SiC Micropipe Sidewalls by Non-Line-of-Sight Confocal Spectromicroscopy: Amphoteric Giant Traps
Irwan Saleh Kurniawan, Russel Cruz Sevilla, Ruth Jeane Soebroto et al. (+6 more)
Micropipes are among the most detrimental defects in SiC wafer and are closely linked to catastrophic device failure. However, the microscopic defect nature of their internal sidewalls and the mechanism of the associated leakage current remain poorly understood, because their high-aspect-ratio geometry severely restricts direct optical probing. Here, we develop a non-line-of-sight confocal multiple-reflection spectromicroscopy technique combined with direct defect photoionization to unravel the defect physics of micropipe sidewalls. We show that these sidewalls host a high density of donor-like and acceptor-like deep-level states, giving rise to ultrabroad emission bands composed of intrinsic DAP-like recombination and detrapping-mediated free-to-bound transitions. Unlike conventional defect luminescence, the DAP-like emission remains dominant even at room temperature across all excitation powers. This behavior is attributed to rapid carrier capture by the sidewall defects, as evidenced by fast-rising and nanosecond-scale decay dynamics, along with coupled carrier kinetics. These results suggest that micropipe sidewalls can serve as extended amphoteric
giant traps and carrier reservoirs, facilitating leakage current through trap-assisted transport. Our work provides a nondestructive optical approach for directly probing high-aspect-ratio extended defects and offers deep mechanistic insight into their defect physics and leakage mechanisms.
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All authors Irwan Saleh Kurniawan, Russel Cruz Sevilla, Ruth Jeane Soebroto, Hsiu-Ying Huang, Hsiu-Ming Hsu, Ji-Lin Shen, Sheng Hsiung Chang, Wen-Chung Li, Chi-Tsu Yuan
Materials Science · Cross-listed from physics.optics
Emergence of Localized Surface Plasmons in Unpatterned Hyperdoped Polycrystalline Silicon
Mohamad Bahsoun, Jesse Groenen, Gonzague Agez et al. (+7 more)
The ability to engineer localized surface plasmon resonances at large scale usually relies on precise nanoscale patterning. Here, we demonstrate that mid-infrared plasmonic responses can instead emerge in unpatterned polysilicon films composed of nanometric (5-50 nm) grains, challenging established design paradigms and eliminating the need for external nanostructuring. Using tailored out-of-
equilibrium annealing conditions, we show that hyperdoped polysilicon layers exhibit enhanced light-matter interactions that can be tuned across the mid-infrared range. By combining advanced electron microscopy, infrared spectroscopy and finite-difference time-domain electrodynamic simulations, we demonstrate that these remarkable optical properties originate from naturally formed metal-dielectric interfaces at grain boundaries, which support localized surface plasmon resonances. Importantly, this result is universal and can be extended to any doped
semiconductor system, regardless of the synthesis technique, provided that the grain size remains in the nanometric range. This work opens up a new field in plasmonics centered on polycrystalline
semiconductors, paving the way for cost-effective systems that are fully compatible with microelectronic and photovoltaic technologies, and capable of significantly reshaping light-matter interactions in the infrared range.
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All authors Mohamad Bahsoun, Jesse Groenen, Gonzague Agez, Sébastien Joulié, Cécile Marcelot, Robin Cours, Sébastien Kerdiles, Mathieu Opprecht, Caroline Bonafos, Jean-Marie Poumirol
Statistical Mechanics · Cross-listed from cs.LG
Concurrence of Symmetry Breaking and Nonlocality Phase Transitions in Diffusion Models
Yifan F. Zhang, Fangjun Hu, Guangkuo Liu et al. (+2 more)
Diffusion models undergo a phase transition in a critical time window during generation dynamics, with two complementary diagnoses of criticality. The
symmetry breaking picture views the critical window as when trajectories bifurcate into different semantic minima of the energy landscape, whereas the nonlocality picture views the critical window as when local denoising fails. We study whether two notions of such phase transitions are concurrent in modern
diffusion transformers. By evaluating the dynamics and outcomes of the generation trajectory, we observe a near-simultaneous occurrence of the non-locality and
symmetry breaking critical times. Our work is the first to unify the two notions of phase transitions in practice: it provides a concrete diagnostic for when and why
diffusion models rely on conditioning and global denoising, enabling principled evaluation of model efficiency and guiding the design of architectures and sampling schemes that avoid unnecessary computation.
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All authors Yifan F. Zhang, Fangjun Hu, Guangkuo Liu, Mert Okyay, Xun Gao
Statistical Mechanics · Cross-listed from cs.LG
Improving FMQA via Initial Training Data Design Considering Marginal Bit Coverage in One-Hot Encoding
Taiga Hayashi, Yuya Seki, Kotaro Terada et al. (+3 more)
Factorization machine with quadratic-optimization annealing (FMQA) is a black-box optimization method that combines a factorization machine (FM) surrogate with QUBO-based search by an Ising machine. When FMQA is applied to integer or discretized continuous variables via one-hot encoding, uniform random initial sampling can leave many binary variables never active in the initial training data, and the corresponding FM parameters receive no direct gradient updates from the observed responses. We address this by designing the initial training data to achieve complete marginal bit coverage, namely, ensuring that every binary variable obtained by one-hot encoding takes the value one at least once. We use two space-filling sampling methods, Latin hypercube sampling (LHS) and the Sobol' sequence, yielding LHS-FMQA and Sobol'-FMQA. On the human-powered aircraft wing-shape optimization
benchmark with 17 and 32 design variables, both proposed methods achieved numerically higher mean final cruising speeds than the baseline FMQA, with the advantage more pronounced on the 32-variable problem.
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All authors Taiga Hayashi, Yuya Seki, Kotaro Terada, Yosuke Mukasa, Shuta Kikuchi, Shu Tanaka
Statistical Mechanics · Cross-listed from hep-th
Expectation values after an integrable boundary quantum quench
Zoltán Bajnok, Dávid Fülepi and Máté Lencsés
We investigate an integrable boundary quench, in which one integrable boundary condition is suddenly switched to another. We develop a general framework for analyzing the resulting real-time dynamics based on form factors of bulk and boundary-changing operators. We first study the problem at the conformal point of the Lee-Yang model and then extend the analysis to its massive perturbation, where we examine the time
evolution of the pre-quench
vacuum and compute the
vacuum-to-
vacuum matrix elements of local operators inserted after the quench. The analytical results are validated by numerical calculations using the truncated conformal space approach adapted to boundary-changing situations.
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Statistical Mechanics
Role of mass fluctuations in the diffusion of clusters of Brownian particles with activity
Daniela Moretti, Pasquale Digregorio, Giuseppe Gonnella et al. (+1 more)
Motivated by the anomalous
diffusion observed in clusters of active Brownian particles (ABPs), where the center-of-mass
diffusion coefficient scales as $D\sim N^{-1/2}$ with respect to the number $N$ of particles in the cluster, we derive a minimal theoretical framework starting from the single-particle Langevin equations. The model consists of two coupled
stochastic equations: one for the cluster center-of-mass trajectory and one for the mass
evolution $N(t)$, explicitly accounting for
stochastic displacements induced by particle attachment and detachment. We specialize and validate the framework against ABP simulations of isolated clusters in stationary conditions, where $N(t)$ follows a Gaussian process with mean $N_0$, variance $\propto N_0^\beta$, and persistence time $\propto N_0^\kappa$. Analytical solution of the coupled equations yields the long-time
diffusion coefficient as the sum of two contributions: a conventional term $\propto N_0^{-1}$) due to thermal noise plus summation of active forces, and a fluctuation-driven term $\propto N_0^{-\delta}$ with $\delta=2-2/d-\beta+\kappa$, where $d$ is the spatial dimension. We demonstrate that anomalous scaling emerges whenever the second term becomes dominant. The model predicts $D\sim N^{-\alpha}$ with $\alpha=0.63\pm0.06$, in good quantitative agreement with large-scale ABP simulations.
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All authors Daniela Moretti, Pasquale Digregorio, Giuseppe Gonnella, Antonio Suma
Mesoscale and Nanoscale Physics
Spin-wave bandgap engineering via mode hybridization in dipolar-coupled YIG film/CoFeB nanodisk magnonic crystals
Junyoung Hyun, Krzysztof Szulc, Mateusz Zelent et al. (+5 more)
We investigate
spin-wave transport in hybrid two-dimensional magnonic
crystals comprising a low-damping yttrium iron garnet (YIG) film coupled to a periodic array of CoFeB nanodisks. Using propagating
spin-wave spectroscopy, super-Nyquist magneto-optical Kerr effect microscopy, and micromagnetic simulations, we demonstrate the formation of pronounced and tunable bandgaps that do not originate from conventional Bragg scattering. Instead, these gaps arise from hybridization between the fundamental magnonic-
crystal mode and in-plane transverse standing modes induced by the periodic nanodisk array. The spectral position and width of these gaps are controlled by
geometric parameters and by the
magnetic state of the nanodisks, including their
vortex configuration, which governs both static and dynamic dipolar coupling. For larger
lattice periods, additional gaps emerge through hybridization with modes quantized both transverse and parallel to the
spin-wave propagation direction, reflecting dispersion folding in two dimensions. Our results establish mode hybridization as a versatile mechanism for engineering
spin-wave band structures beyond the constraints of Bragg scattering and provide a pathway toward reconfigurable magnonic devices based on dipolar-coupled hybrid architectures.
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All authors Junyoung Hyun, Krzysztof Szulc, Mateusz Zelent, Nikolai Kuznetsov, Lukáš Flajšman, Maciej Krawczyk, Paweł Gruszecki, Sebastiaan van Dijken
Soft Condensed Matter
Predicting the Brittle-to-Ductile Transition in Amorphous Polymers
Valeriy V. Ginzburg, Oleg Gendelman and Alessio Zaccone
Brittle-ductile transition (BDT) is an important characteristic of amorphous (and semicrystalline)
polymers. For a given strain rate, at temperatures above BDT, the
polymers exhibit strain softening followed by yield and strain hardening, while at temperatures below BDT, the same materials exhibit brittle failure at relatively low strains. Surprisingly, today there is no simple model describing BDT as a function of
polymer chemistry, sample history, deformation type, and strain rate. Experimental data suggest that BDT is often, though not always, associated with the beta-transition. We formulate a simple scalar model to describe the visco-elasto-plastic shear stress-strain curves as functions of temperature and strain rate. We also show that within this model, there is always an upper bound on the strain rate where the material can have a uniform viscoplastic flow; this upper bound is taken to represent the BDT. We stipulate that this upper bound is inversely proportional to the Johari-Goldstein beta-relaxation time. Using our "general" Sanchez-Lacombe "two-state, two-(time)scale" (SL-TS2) model, we compute the BDT for three
polymers (polystyrene, poly(methylmethacrylate), and poly(vinylchloride)) and found a good agreement with experimental data.
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Superconductivity
Nonlocal transport phenomena in coupled quasiperiodic Kitaev chains
Koki Mizuno
We investigate the topological phases in a coupled one-dimensional p-wave superconducting Fibonacci quasicrystal modeled by the quasiperiodic Kitaev chain. Recent studies have shown that the coupled system can host topological edge modes with Majorana
fermions and enhance their topological protection, depending on the pattern of quasiperiodicity. In this work, we elucidate the topological phases of the coupled system and demonstrate the dependence of differential conductance on the lead connecting pattern employing the Keldysh formalism and the recursive Green's function method. Our findings reveal the emergence of topological phases in the coupled system, which are characterized by the presence of Majorana edge modes and the seepage of the Majorana wave function. Furthermore, we identify a new topological phase transition induced by quasiperiodicity in the coupled system.
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