Mesoscale and Nanoscale Physics
Acoustic Metamaterials with Positive and Negative Couplings: Modular and One Piece Architectures for Topological Models
Jackson Saunders and Camelia Prodan
We describe two 3D-printing approaches for realizing tight-binding models in acoustic metamaterials using H-shaped resonators: a modular system with tunable interconnections and an integrated one-piece design for reducing dissipation. The platform supports both positive and negative coupling through
geometric control, enabling accurate acoustic analogs of topological models. By tuning the coupling length (CL), we eliminate detuning effects and preserve particle-hole
symmetry. We further quantify the influence of the Total Coupling Area (TCA) on band
topology and derive conditions for constant-area coupling. The system was tested on SSH and Kitaev chains, revealing midgap edge and interface states, confirming topological behavior in both configurations.
Read the full abstract ▾
Soft Condensed Matter · Cross-listed from physics.chem-ph
Martini Mapper: An Automated Fragment-Based Framework for Developing Coarse-Grained Models within the Martini 3 Framework
Kevin V. Bigting, Shubhadeep Nag and Yaxin An
Coarse-graining (CG) reduces molecular details to extend the time and length scales of molecular dynamics simulations to microseconds and micrometers. However, the CG approaches have long been limited by the difficulty of constructing both accurate and transferable models efficiently, considering the large diversity of chemical structures of materials. Among CG force fields, Martini is the most widely used, as it retains essential chemical features while offering substantial computational efficiency. Its most recent version, Martini 3, expands chemical resolution through a much broader bead set, particularly for small molecules. However, this flexibility also complicates the mapping of organic molecules because of context-dependent rules and the lack of standardized procedures. To address this issue, we present an automated framework that builds Martini 3 models directly from SMILES (Simplified Molecular Input Line Entry System) strings by combining a curated bead dictionary with a hierarchical, rule-based
algorithm and molecule-specific bonded parameters. Our framework, Martini Mapper https://github.com/eliobaby/Martini_mapper, generated Martini 3 models for 6,280 molecules across six chemically diverse
datasets, including 1,689 systems with bond/angle parameters and additional large systems mapped at the topological level. A curated subset of 1,075 mapped structures was benchmarked using transfer free energies in hydrated octanol, hexadecane, and chloroform from water against reference data wherever available. We further examined the
benchmark with structural validation via SASA, yielding good agreement with experimental and atomistic reference data. The workflow can also map large molecules containing up to 172 heavy atoms, exceeding the capabilities of existing automated approaches. Our framework, therefore, enables Martini 3 structures for high-throughput simulations.
Read the full abstract ▾
Materials Science
Layer breathing Raman mode in two-dimensional van der Waals material $\mathrm{Cr_2Ge_2Te_6}$
Nilesh Choudhury, Sandeep, Neesha Yadav et al. (+2 more)
Two-dimensional (2D) van der Waals (vdW)
magnetic materials have emerged as key materials for next-generation magneto-electric and spintronic devices, where understanding the relationship between layer number,
lattice dynamics, and
magnetic interactions is very important. In this work, we report the observation of the layer breathing mode (LBM) in few-layer $\mathrm{Cr_2Ge_2Te_6}$, a
ferromagnetic semiconductor with thickness dependent electronic,
magnetic and optical properties, using Raman spectroscopy, which serves as a direct fingerprint of interlayer coupling and
lattice symmetry. Group-theoretical
symmetry analysis confirms that the CGT falls under the non-polar category of layered material. The
evolution of the LBM-frequency with increasing layer number (N) reveals a distinct softening trend, characteristic of weakening restoring forces in thicker flakes. By fitting the experimental Raman data using the Linear Chain Model (LCM), we quantitatively extract the interlayer force constant ($\mathrm{K_c}$), providing a measure of the vdW coupling strength between layers.
Read the full abstract ▾
All authors Nilesh Choudhury, Sandeep, Neesha Yadav, Mayank Shukla, Pintu Das
Soft Condensed Matter
Topological flowscape reveals state transitions in nonreciprocal living matter
Hyunseok Lee, EliseAnne Koskelo, Shreyas Gokhale et al. (+7 more)
Nonreciprocal interactions – where forces between entities are asymmetric – govern a wide range of nonequilibrium phenomena, yet their role in structural transitions in living and active systems remains elusive. Here, we demonstrate a transition between nonreciprocal states using starfish embryos at different stages of development, where interactions are inherently asymmetric and tunable. Experiments, interaction inference, and topological analysis yield a nonreciprocal state diagram spanning crystalline, flocking, and fragmented states, revealing that weak nonreciprocity promotes structural order while stronger asymmetry disrupts it. To capture these transitions, we introduce topological landscapes, mapping the distribution of structural motifs across state space. We further develop topological flowscapes, a dynamic framework that quantifies transitions between collective states and detects an informational rate shift from the experimental state transition. Together, these results establish a general approach for decoding nonequilibrium transitions and uncover how asymmetric interactions sculpt the dynamical and structural architecture of active and living matter.
Read the full abstract ▾
All authors Hyunseok Lee, EliseAnne Koskelo, Shreyas Gokhale, Junang Li, Chenyi Fei, Chih-Wei Joshua Liu, Lisa Lin, Jorn Dunkel, Dominic J. Skinner, Nikta Fakhri
Mesoscale and Nanoscale Physics
Effective Hamiltonians for Ge/Si core/shell nanowires from higher order perturbation theory
Sebastian Miles, A. Mert Bozkurt, Dániel Varjas et al. (+1 more)
We theoretically explore the electronic structure of holes in cylindrical Germanium/Silicon core/shell nanowires using a perturbation theory approach. The approach yields a set of interpretable and transferable effective low-energy models for the lowest few sub-bands up to fifth order for experimentally relevant growth directions. In particular, we are able to resolve higher order cross terms e.g., the dependency of the effective mass on the
magnetic field. Our study reveals orbital inversions of the lowest sub-bands for low-
symmetry growth directions, leading to significant changes of the lower order effective coefficients. We demonstrate a reduction of the direct Rashba
spin-orbit interaction due to competing
symmetry effects for low-
symmetry growth directions. Finally, we find that the effective mass of the confined holes can diverge yielding quasi flat bands interesting for correlated states. We show how one can tune the effective mass of a single
spin band allowing one to tune the effective mass selectively to its divergent points.
Read the full abstract ▾
All authors Sebastian Miles, A. Mert Bozkurt, Dániel Varjas, Michael Wimmer
Strongly Correlated Electrons
Evidence for atomic-scale vibron-mediated electron bunching
A. Maiti, M. Amato, V. S. Stolyarov et al. (+5 more)
Due to the Coulomb blockade effect, electrons rarely bunch during transport, a phenomenon observed only in a few specially engineered mesoscopic configurations. In this work, we introduce an atomically resolved shot-noise study to demonstrate the possibility of electron bunching through vibrational coupling which takes place in an atomically sized nano-electro-mechanical system. Using tunnelling spectroscopy, we observe signatures of vibron-assisted tunnelling on an Fe
impurity in Bi$_2$Se$_3$. Notably, simultaneous shot-noise measurements at the centre of the vibrating
impurity reveal super-Poissonian noise. In the absence of alternative sources of super-Poissonian noise, this implies vibronic-coupling-induced bunching of electrons during the tunnelling process through the
impurity, as theoretically predicted decades ago. As a future outlook, if coherence between electrons can be implemented, vibron-mediated electron bunching at single atomic sites may be exploited as a local injection source of $N$-paired electrons.
Read the full abstract ▾
All authors A. Maiti, M. Amato, V. S. Stolyarov, H. Aubin, J. Estève, F. Pistolesi, M. Aprili, F. Massee
Strongly Correlated Electrons
Floquet Engineering Magnetism and Superconductivity in the Square-Lattice Hubbard Model
Jan-Niklas Herre, Takuya Okugawa, Ammon Fischer et al. (+2 more)
We study the interplay of
magnetic order and superconductivity in the square-
lattice Hubbard model under periodic driving with circularly polarized light. Formulating diagrammatic techniques based on the random-phase approximation in terms of Floquet Green's functions, allows us to analyze fluctuation-driven unconventional pairing for weak-to-moderate interactions. The interplay of repulsive interactions and photo-assisted hopping of electrons gives rise to a rich
magnetic phase diagram featuring an
antiferromagnetic-to-
ferromagnetic transition prior to a Floquet Lifshitz transition. Close to the
antiferromagnetic transition, topological $d+id$-wave superconductivity prevails in the phase diagram for a wide range of drive parameters. At intermediate-to-high frequency driving near the Floquet Lifshitz transition, superconducting orders are tuned from
spin-singlet $d$-wave to
spin-triplet $p$-wave character, providing an effective protocol for Floquet engineering topological superconductivity.
Read the full abstract ▾
All authors Jan-Niklas Herre, Takuya Okugawa, Ammon Fischer, Christoph Karrasch, Dante M. Kennes
Materials Science · Cross-listed from quant-ph
2025 Quantum Diamond Workshop Findings Report
Danielle A. Braje, Matthew L. Markham, Jennifer M. Schloss et al. (+2 more)
This report synthesizes the outcomes of a two-day workshop held in Washington, D.C. in May, 2025 that convened researchers, industry representatives, and government stakeholders to examine the current state and future directions of
quantum diamond technologies. The workshop's goals were to assess the most promising use cases, to identify the key technical and structural challenges limiting adoption, and to chart potential pathways for aligning application needs with diamond material and device development. Through a series of technical presentations and open discussions, participants explored both near-term demonstrations and long-term infrastructure needs, highlighting the critical role of coordination between material suppliers, device engineers, and end users. The goal of this report is to distill those insights into a coherent set of cross-cutting themes, challenges, and strategic actions that can guide government, industry, and academic efforts to accelerate the maturation and commercialization of
quantum diamond technologies.
Read the full abstract ▾
All authors Danielle A. Braje, Matthew L. Markham, Jennifer M. Schloss, Michael A. Slocum, Ronald L. Walsworth
Materials Science
Edwards Localization
Riccardo Fantoni
We study the localization problem in
quantum stochastic mechanics. We start from the Edwards model for a particle in a bath of scattering centers and prove static localization of the ground state wavefunction of the particle in a one dimensional square well coupled to Dirac delta like scattering centers in arbitrary but fixed positions. We see how the localization increases for increasing coupling $g$ and increasing number of scattering centers at constant density. Then we choose the scattering centers positions as pseudo random numbers with a uniform probability distribution and observe an increase in the localization of the average of the ground state over the many positions realizations. We discuss how this averaging procedure is consistent with a picture of a particle in a Bose-Einstein condensate of of non interacting
boson scattering centers interacting with the particle with Dirac delta functions pair potential. We then study the dynamics of the ground state wave function. We conclude with a discussion of the affine quantization version of the Lax model which reduces to a system of contiguous square wells with walls in arbitrary positions independently of the coupling constant $g$.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Vector magnetometry using cavity-enhanced microwave readout in nitrogen-vacancy diamond
Reginald Wilcox, David Phillips, Matthew Steinecker et al. (+6 more)
We demonstrate $4\pi$-steradian vector
magnetic field sensing using an ensemble of nitrogen-vacancy (NV) centers in a single-
crystal diamond coupled to a microwave (MW) cavity. The MW cavity enhances the
spin-
photon coupling which enables efficient, high-contrast
spin-state readout via MW interrogation and removes the need for bulky optical collection components. An applied AC bias
magnetic field lifts the zero-field degeneracy of the four crystallographic NV orientations, allowing each orientation to be individually addressed and used for vector reconstruction of the
magnetic field. The resulting magnetometer has a 40% contrast (20x higher than typical for optical
spin-ensemble readout) and achieves a single-axis sensitivity of 250 pT/$\sqrt{\mathrm{Hz}}$ which is flat from DC to 1 kHz. Noise models of the composite
spin-cavity system establish MW amplitude noise as the dominant noise source and predict a thermal noise limit of 2 pT/$\sqrt{\mathrm{Hz}}$.
Read the full abstract ▾
All authors Reginald Wilcox, David Phillips, Matthew Steinecker, Erik Eisenach, Corey Hawkins, Linh Pham, Jennifer Schloss, Dirk Englund, Danielle Braje
Materials Science
Human-AI collaborative autonomous synthesis with pulsed laser deposition for remote epitaxy
Asraful Haque, Daniel T. Yimam, Jawad Chowdhury et al. (+10 more)
Autonomous laboratories typically rely on data-driven decision-making, occasionally with human-in-the-loop oversight to inject domain expertise. Fully leveraging AI
agents, however, requires tightly coupled, collaborative workflows spanning hypothesis generation, experimental planning, execution, and interpretation. To address this, we develop and deploy a human-AI collaborative (HAIC) workflow that integrates large
language models for hypothesis generation and analysis, with collaborative policy updates driving autonomous pulsed
laser deposition (PLD) experiments for remote epitaxy of BaTiO$_3$/
graphene. HAIC accelerated the hypothesis formation and experimental design and efficiently mapped the growth space to
graphene-damage. In situ Raman spectroscopy reveals that chemistry drives degradation while the highest energy plume components seed defects, identifying a low-O$_2$ pressure low-temperature synthesis window that preserves
graphene but is incompatible with optimal BaTiO$_3$ growth. Thus, we show a two-step Ar/O$_2$ deposition is required to exfoliate ferroelectric BaTiO$_3$ while maintaining a monolayer
graphene interlayer. HAIC stages human insight with AI
reasoning between autonomous batches to drive rapid scientific progress, providing an
evolution to many existing human-in-the-loop autonomous workflows.
Read the full abstract ▾
All authors Asraful Haque, Daniel T. Yimam, Jawad Chowdhury, Ralph Bulanadi, Ivan Vlassiouk, John Lasseter, Sujoy Ghosh, Christopher M. Rouleau, Kai Xiao, Yongtao Liu, Eva Zarkadoula, Rama K. Vasudevan, Sumner B. Harris
Quantum Gases
Coherent-state path integrals in quantum thermodynamics
Luca Salasnich and Cesare Vianello
In these notes, we elucidate some subtle aspects of coherent-state path integrals, focusing on their application to the
equilibrium thermodynamics of
quantum many-particle systems. These subtleties emerge when evaluating path integrals in the continuum, either in imaginary time or in Matsubara-frequency space. Our central message is that, when handled with due care, the path integral yields results identical to those obtained from the canonical
Hamiltonian approach. We illustrate this through a pedagogical treatment of several paradigmatic systems: the bosonic and fermionic harmonic oscillators, the single-site Bose-Hubbard and Hubbard models, the weakly-interacting Bose gas with finite-range interactions, and the BCS
superconductor with finite-range interactions.
Read the full abstract ▾
Quantum Gases
Stable Quantum Vortices in Lee-Huang-Yang Dipolar Superfluids
S. Sabari, R. Radha, Lauro Tomio et al. (+1 more)
The nucleation and dynamics of
vortices in the quasi-two-dimensional rotating dipolar Bose-Einstein condensate are explored by taking into account the Lee-Huang-Yang (LHY) correction to the mean-field (MF) theory. Assuming approximate cancellation of the MF interactions, we focus on the formation of a pure LHY superfluid. The effect of rotational frequency $\Omega $ is investigated numerically by determining the corresponding number of stable
vortices in the superfluid, together with the respective energy per particle $E$ and chemical potential $\mu $. The LHY superfluid provides a deep minimum of $E$ and $\mu $, indicating that it is a remarkably robust state of
quantum matter. By fixing the LHY interaction strength, an exact single-
vortex critical frequency is found, along with the respective chemical potential. A notable feature, observed when creating the LHY superfluid with fewer than five
vortices, which is understood as being due to the superfluid's nonlinearity and trapping aspect ratio, is the large frequency ranges admitting the production of two and four
vortices, as compared to the small frequency ranges to obtain one and three
vortices.
Read the full abstract ▾
All authors S. Sabari, R. Radha, Lauro Tomio, B. A. Malomed
Mesoscale and Nanoscale Physics
STEM EBIC as a Quantitative Probe of Semiconductor Devices
Sebastian Schneider, Sebastian Beckert, René Hammer et al. (+3 more)
Electron beam-induced current (EBIC) imaging in the scanning transmission electron microscope (STEM), STEM-EBIC, provides direct access to carrier transport at the nanoscale. While well established in bulk SEM geometries, its application to thin TEM lamellae remains largely unexplored. Here, we present a systematic STEM-EBIC study of silicon photodiode lamellae prepared by gallium and xenon focused ion beam (FIB) milling. We directly visualize the p-n junctions in thin cross sections and extract effective
diffusion lengths for electrons and holes as a function of local thickness. The values are orders of magnitude smaller than those obtained by SEM-EBIC on bulk silicon, reflecting pronounced surface recombination and FIB-induced surface modifications. Current-voltage measurements further reveal severe deviations from the expected diode-like behavior, which we attribute to ohmic metal-
semiconductor contacts in the emasurement setup. Our analysis establishes STEM-EBIC as a quantitative probe of carrier transport in nanoscale devices.
Read the full abstract ▾
All authors Sebastian Schneider, Sebastian Beckert, René Hammer, Markus König, Grigore Moldovan, Darius Pohl
Materials Science
The Interoperability Challenge in DFT Workflows Across Implementations
S. K. Steensen, T. S. Thakur, M. Dillenz et al. (+11 more)
Interoperability and cross-validation remains a significant challenge in the computational materials discovery community. In this context, we introduce a common input/output standard designed for internal translation by various workflow managers (AiiDA, PerQueue, Pipeline Pilot, and SimStack) to produce results in a unified schema. This standard aims to enable engine-agnostic workflow execution across multiple density functional theory (DFT) codes, including CASTEP, GPAW,
Quantum ESPRESSO, and VASP. As a demonstration, we have implemented a workflow to calculate the open-
circuit voltage across several battery cathode materials using the proposed universal input/output schema. We analyze and resolve the challenges of reconciling energetics computed by different DFT engines and document the code-specific idiosyncrasies that make straightforward comparisons difficult. Motivated by these challenges, we outline general design principles for robust automated DFT workflows. This work represents a practical step towards more reproducible and interoperable workflows for high-throughput materials screening, while highlighting challenges of aligning electronic properties, especially for non-pristine structures.
Read the full abstract ▾
All authors S. K. Steensen, T. S. Thakur, M. Dillenz, J. M. Carlsson, C. R. C. Rego, E. Flores, H. Hajiyani, F. Hanke, J. M. G. Lastra, W. Wenzel, N. Marzari, T. Vegge, G. Pizzi, I. E. Castelli
Statistical Mechanics · Cross-listed from hep-th
Integrability for the spectrum of Jordanian AdS/CFT
Sibylle Driezen, Fedor Levkovich-Maslyuk and Adrien Molines
Jordanian deformations offer rare integrable realisations of non-AdS holography, whose solvability methods differ from conventional AdS/CFT examples. Here we study the $\mathfrak{sl}(2,R)$ sector of the Jordanian deformed $AdS_5\times S^5$ string and its weak-coupling
spin chain counterpart: the $\mathrm{XXX}_{-1/2}$ model with a non-abelian Jordanian Drinfel'd twist. While the twist breaks the usual highest-weight structure that underlies conventional Bethe ansätze, we show that the complete spectrum remains solvable within the Baxter framework. We argue that the functional form of the $TQ$-relation is unchanged, yet the structure of the $Q$-functions is nontrivially modified. This allows us to obtain analytic expressions at arbitrary
spin chain length $J$, which match the deformed string spectrum at the one-loop level and to subleading order in the large-$J$ expansion, despite the severely reduced
symmetry. Our results provide nontrivial tests of the Jordanian AdS/CFT correspondence and lay the groundwork for implementing the Separation of Variables program in non-abelian Drinfel'd-twisted models.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Efficient computation of quantum time-optimal control
Andrei A. Stepanenko, Kseniia S. Chernova, Maxim Mazanov et al. (+1 more)
We present an approach to compute time-optimal control of a
quantum system which combines
quantum brachistochrone and Lax pair techniques and enables efficient investigation of large-scale
quantum systems. We illustrate our method by finding the
quantum speed limit for a single-particle excitation in a nearest-neighbor-coupled
qubit lattice with switchable couplings and fixed sum of their squares. We obtain the solution for a finite system with up to 10 000
qubits and for the effectively infinite
lattice closed into ring. As another application of our method, we derive the
quantum speed limit for a
lattice with time-independent couplings.
Read the full abstract ▾
All authors Andrei A. Stepanenko, Kseniia S. Chernova, Maxim Mazanov, Maxim A. Gorlach
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Collective Enhancement of Photon Blockade via Two-Photon Interactions
Lijuan Dong, Aanal Jayesh Shah, Peter Kirton et al. (+2 more)
Analogous to Coulomb blockade for electrons,
photon blockade is a key
quantum optical effect in which the presence of one
photon prevents the transmission of subsequent ones through a nonlinear medium. Beyond its fundamental interest,
photon and multi-
photon blockade are actively studied as mechanisms for generating technologically-relevant
quantum states of light. Although
photon blockade typically requires achieving strong light-matter coupling, increasing the number of atoms fails to enhance antibunching. Here, we analyze the optical transmission properties of a
quantum resonator that embeds a two-
photon-coupled ensemble of emitters, combining an approximate analytical approach with full
quantum numerical simulations. We show that when light and matter are coupled via a two-
photon interaction, both single- and multi-
photon blockade can benefit from a collective enhancement. We propose different driving schemes in which the second or third-order correlation functions are strongly suppressed with increasing atom number. Differently from established methods, this collective enhancement of non-classical properties occurs with
unitary transmission and is ultimately constrained only by decoherence. This demonstrates that collective two-
photon couplings are a powerful mechanism for realizing
photon blockade even in platforms where individual strong coupling is not achievable.
Read the full abstract ▾
All authors Lijuan Dong, Aanal Jayesh Shah, Peter Kirton, Hadiseh Alaeian, Simone Felicetti
Mesoscale and Nanoscale Physics
RF-Squad: A radiofrequency simulator for quantum dot arrays
Tara Murphy, Katarina Brlec, Giovanni Oakes et al. (+5 more)
Spins in
semiconductor quantum dots offer a scalable approach to
quantum computing; however, precise control and efficient readout of large
quantum dot arrays remain challenging, mainly due to the hyperdimensional voltage space required for tuning multiple gates per dot. To automate this process, large
datasets are required for testing and training autotuning
algorithms. To address the demand for such large
datasets, we introduce RF-Squad, a physics-based simulator designed to realistically replicate radiofrequency (RF) reflectometry measurements of
quantum dot arrays, with the ability to go beyond the Constant Interaction Model (CIM) and simulate physical phenomena such as tunnel coupling, tunnel rates, and
quantum confinement. Implemented in JAX, an accelerated linear
algebra library, RF-Squad achieves high computational speed, enabling the simulation of a 100x100 pixel charge stability diagram of a double
quantum dot (DQD) in 52.1 $\pm$0.2 milliseconds at the CIM level. Using optimization
algorithms, combined with it's layered architecture, RF-Squad allows users to balance physical accuracy with computational speed, scaling from simple to highly detailed models.
Read the full abstract ▾
All authors Tara Murphy, Katarina Brlec, Giovanni Oakes, Lorenzo Peri, Henning Sirringhaus, Henry Moss, M. Fernando Gonzalez Zalba, David Wise
Materials Science
Visible and Terahertz Nonlinear Responses in the Topological Noble Metal Dichalcogenide PdTe2
George J. de Coster, Lucas Lafeta, Stefan Heiserer et al. (+5 more)
Nonlinear processes can offer pathways to next-generation sensors and frequency mixing devices to overcome modern imaging, detection, and communication challenges. In this article, we report on strong second and third-order nonlinear optical responses in visible and terahertz (THz) light in single
crystals of the noble metal dichalcogenide PdTe$_2$. We find that buried conduction and valence topological surface states of PdTe$_2$ lead to resonant optical second-harmonic generation. On the other hand, although the nonlinear responses obtained with THz excitation are not close to this resonance, they can be clearly observed in reflection geometry, even in the presence of broadband excitation, where optical filters are not necessary to observe the enhanced odd-order higher harmonic output. By carefully considering the radiative photocurrent framework of stimulated THz emission, we are able to extract fingerprints of both second- and third-order processes in the THz regime, and show that PdTe$_2$ is a promising material candidate for
radio frequency rectification, frequency mixing, and beam focusing.
Read the full abstract ▾
All authors George J. de Coster, Lucas Lafeta, Stefan Heiserer, Cormac Ó Coileáin, Zdenek Sofer, Achim Hartschuh, Georg S. Duesberg, Paul Seifert
Materials Science · Cross-listed from cs.LG
Data-efficient U-Net for Segmentation of Carbide Microstructures in SEM Images of Steel Alloys
Alinda Ezgi Gerçek, Till Korten, Paul Chekhonin et al. (+2 more)
Understanding reactor-pressure-vessel steel microstructure is crucial for predicting mechanical properties, as carbide precipitates both strengthen the
alloy and can initiate cracks. In scanning electron microscopy images, gray-value overlap between carbides and
matrix makes simple thresholding ineffective. We present a data-efficient
segmentation pipeline using a lightweight U-Net (30.7~M parameters) trained on just 10 annotated scanning electron microscopy images. Despite limited data, our model achieves a Dice-Sørensen coefficient of 0.98, significantly outperforming the state-of-the-art in the field of metallurgy (classical image analysis: 0.85), while reducing annotation effort by one order of magnitude compared to the state-of-the-art data efficient
segmentation model. This approach enables rapid, automated carbide quantification for
alloy design and generalizes to other steel types, demonstrating the potential of data-efficient deep learning in reactor-pressure-vessel steel analysis.
Read the full abstract ▾
All authors Alinda Ezgi Gerçek, Till Korten, Paul Chekhonin, Maleeha Hassan, Peter Steinbach
Mesoscale and Nanoscale Physics
Theoretical study of orbital torque: Dependence on ferromagnet species and nonmagnetic layer thickness
Daegeun Jo and Peter M. Oppeneer
The manipulation of magnetization in
ferromagnetic metals (FMs) through orbital torque (OT) has emerged as a promising route for energy-efficient
magnetic devices without relying on heavy metals. While Ti and Cu are among the most extensively studied light nonmagnetic metals (NMs) for OT devices, theoretical calculations of the resulting torque have remained limited. Here, we present a systematic and quantitative theoretical study of current-induced torques in Ti/FM and Cu/FM (FM = Co, Ni)
bilayers using realistic tight-binding models derived from ab initio electronic structures. We find that the torque in Ti/FM is larger for Ni than for Co, but this trend does not necessarily hold in Cu/FM, revealing that the FM dependence of OT is not universal but varies with the orbital current source. Moreover, the dependence of OT on NM thickness clearly indicates its NM bulk origin in both Ti- and Cu-based systems. Notwithstanding, the quantitative characteristics of OT cannot be explained by a simplified picture based on the individual bulk properties of the NM or FM layers. These results provide microscopic insight and practical guidance for designing light-metal-based orbitronic devices.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Lattice Resonances in Periodic Arrays of Time-Modulated Scatterers
María Blanco de Paz, Juan R. Deop-Ruano, Diego M. Solís et al. (+1 more)
Lattice resonances are collective optical modes supported by periodic arrays of scatterers, arising from their coherent interaction enabled by the underlying periodicity. Owing to their collective nature, these resonances produce optical responses that are both stronger and spectrally narrower than those of individual scatterers. While such phenomena have been extensively studied in conventional time-invariant systems, recent advances in time-varying photonics present new opportunities to exploit and enhance the extraordinary characteristics of these collective modes. Here, we investigate
lattice resonances in periodic arrays of time-modulated scatterers using a simple framework based on the dipolar approximation and time-Floquet theory, where each scatterer is modeled as a harmonic oscillator with periodically varying optical properties. We begin by analyzing the response of an individual scatterer, leveraging our model to identify the complex eigenfrequencies that define its dynamics. We show that, for the appropriate modulation amplitude and frequency, the imaginary part of one of these eigenfrequencies vanishes, leading to amplification. Building on this, we extend our analysis to a periodic array to investigate the effect of the interplay between temporal modulation and
lattice resonances. In contrast to isolated scatterers, the collective nature of
lattice resonances introduces a markedly more intricate spectral dependence of the amplification regime. Notably, this amplification emerges at substantially lower modulation strengths, facilitated by the enhanced light-matter interaction and increased lifetime provided by these collective resonances. Our work establishes a simple theoretical framework for understanding collective
lattice resonances in time-modulated arrays, enabling dynamic control and amplification of these modes.
Read the full abstract ▾
All authors María Blanco de Paz, Juan R. Deop-Ruano, Diego M. Solís, Alejandro Manjavacas
Mesoscale and Nanoscale Physics
ARPES signatures of trions in van der Waals materials
Giuseppe Meneghini, Maja Löwe, Raul Perea-Causin et al. (+5 more)
Angle-resolved photoemission spectroscopy (ARPES) has recently emerged as a direct probe of excitonic correlations in two-dimensional
semiconductors, resolving their dispersion and dynamics in energy-momentum space, including dark
exciton states inaccessible to optical techniques. However, the ARPES fingerprint of charged
excitons (trions), which plays a key role in all doped and gated 2D material systems, has remained unknown so far. We present a first theoretical analysis of trion signatures in monolayer transition-metal dichalcogenides, highlighting how the additional charge carrier modifies the spectral position and shape relative to neutral
excitons in ARPES spectra. Interestingly, we further predict that mass-imbalanced trions yield a characteristic double-peak structure, clearly separated in energy and line shape from neutral
excitons. The predicted temperature dependence of these features offers guidance for experimental investigations aimed at identifying trionic states, thereby establishing a framework for ARPES studies of many-body Coulomb complexes in doped two-dimensional
semiconductors.
Read the full abstract ▾
All authors Giuseppe Meneghini, Maja Löwe, Raul Perea-Causin, Jan Philipp Bange, Wiebke Bennecke, Marcel Reutzel, Stefan Mathias, Ermin Malic
Materials Science
Metavalent Bonding-Induced Phonon Hardening and Giant Anharmonicity in BeO
Xuejie Li, Yuzhou Hao, Yujie Liu et al. (+6 more)
The search for materials with intrinsically low thermal conductivity ($\kappa_L$) is critical for energy applications, yet conventional descriptors often fail to capture the complex interplay between bonding and
lattice dynamics. Here, first-principles calculations are used to contrast the thermal transport in covalent zincblende (zb) and metavalent rocksalt (rs) BeO. We find that the metavalent bonding in rs-BeO enhances
lattice anharmonicity, activating multi-
phonon scattering channels and suppressing
phonon transport. This results in an ultralow $\kappa_L$ of 24 W m$^{-1}$ K$^{-1}$ at 300 K, starkly contrasting with the zb phase (357 W m$^{-1}$ K$^{-1}$). Accurately modeling such strongly anharmonic systems requires explicit inclusion of temperature-dependent
phonon renormalization and four-
phonon scattering. These contributions, negligible in zb-BeO, are essential for high-precision calculations of the severely suppressed $\kappa_L$ in rs-BeO. Finally, we identify three key indicators to guide the discovery of metavalently bonded, incipient-metallic materials: (i) an NaCl-type
crystal structure, (ii) large Grüneisen parameters ($\textgreater$2), and (iii) a breakdown of the Lyddane-Sachs-Teller relation. These findings provide microscopic insight into thermal transport suppression by metavalent bonding and offer a predictive framework for identifying promising thermoelectrics and phase-change materials.
Read the full abstract ▾
All authors Xuejie Li, Yuzhou Hao, Yujie Liu, Shengying Yue, Xiaolong Yang, Turab Lookman, Xiangdong Ding, Jun Sun, Zhibin Gao
Materials Science · Cross-listed from physics.app-ph
Multi-wavelength transparent microfluidics for UV-visible spectroscopy and X-ray scattering studies of photoactive systems
Benedetta Marmiroli, Sumea Klokic, Barbara Sartori et al. (+3 more)
Microfluidic devices are increasingly used in synchrotron-based experiments to deliver and probe
liquid samples, offering advantages such as minimal sample consumption and reduced radiation damage. Despite their growing use, few devices have been specifically designed for monitoring
liquids under photoexcitation, a promising approach for fast structural transitions. Here, a microfluidic device that is transparent to X-rays in one direction, and simulaneously transmits UV and visible light in the perpendicular direction is presented. The device is fabricated using lamination and UV lithography on a dry-film resist, eliminating the need for cleanroom facilities and simplifying production. Its multi-wavelength transparency was validated through UV-visible spectroscopy, where photoexcitation at different wavelengths induced reversible trans-to-cis isomerization of azobenzene and fluoro-azobenzene. X-ray transparency was validated through Small Angle X-ray Scattering (SAXS) measurements on hemoglobin and CO-ligated hemoglobin sensitive to quaternary structural changes. These resusts confirm the suitability of the device for resolving
protein structures and photoinduced conformational dynamics. The design further supports, as some proof of concept results show, temperature-jump and time resolved pump-probe experiments, providing a versatile platform for studying structural
evolution in
liquid samples using synchrotron SAXS.
Read the full abstract ▾
All authors Benedetta Marmiroli, Sumea Klokic, Barbara Sartori, Marie Reissenbuechel, Alessio Turchet, Heinz Amenitsch
Other Condensed Matter · Cross-listed from quant-ph
Photon correlation Fourier spectroscopy of a B center in hBN
Aymeric Delteil, Stéphanie Buil and Jean-Pierre Hermier
The potential of solid-state
quantum emitters for applications critically depends on several key figures of merit. One of the most important is the
quantum coherence of the emitted single
photons, which can be compromised by fast dephasing and spectral
diffusion. In hexagonal boron nitride (hBN), blue-emitting color centers (or B centers) are seen as favorable in this regard, in the light of prior studies mainly based on resonant excitation. Yet, their coherence properties in the more accessible regime of non-resonant excitation (or photoluminescence) has not been extensively characterized. Here, we investigate the coherence and spectral
diffusion of the photoluminescence from a B center in the continuous wave regime using
photon correlation
Fourier spectroscopy. We determine that the emission lineshape consists in a homogeneous contribution, whose linewidth increases with the
laser power, and which is broadened by spectral
diffusion at a timescale of 10 to 100 microseconds. At low power and short time, the emission line is only a factor ~2 above the
Fourier limit, while at long times, the inhomogeneous linewidth increases up to more than a gigahertz. Our work deepens the understanding of decoherence processes of this preeminent family of
quantum emitters in hBN.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Relaxation toward an Ideal Chern Band through Coupling to a Markovian Bath
Bruno Mera and Tomoki Ozawa
We propose a microscopic, weak-coupling mechanism by which generic Chern bands asymptotically relax toward ideal bands. We consider coupling interacting electrons to a Caldeira-Leggett-like Ohmic bosonic bath. Using the Born-Markov approximation, we analytically show that, upon taking the leading order contribution in momentum of the form factor, Slater determinant states of a Chern band under Hartree-Fock approximation evolve toward Slater determinant states corresponding to an ideal Chern band. We also numerically validate our proposal by performing simulation of a massive Dirac model with the extended Hubbard interaction, showing that the Berry
curvature and
quantum metric co-evolve toward saturation of the trace condition. Our proposal provides a concrete dissipative mechanism for driving Chern bands toward ideal
quantum geometry, a fundamental building block for the stabilization of fractional Chern
insulators.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Interlinking helical spin textures in nanopatterned chiral magnets
Luke Alexander Turnbull, Max Thomas Birch, Marisel Di Pietro Martínez et al. (+15 more)
Nanoscale topologically non-trivial magnetization configurations generate significant interest due to both the fundamental properties of their knotted structures and their potential applications in ultra-efficient computing devices. While such textures have been widely studied in two dimensions, three-dimensional (3D) systems can yield more complex configurations, resulting in richer
topologies and dynamic behaviors. However, reliably nucleating these 3D textures has proven challenging, and so far, 3D configurations such as
vortex rings and hopfions can often only be observed forming spontaneously in relatively uncontrolled manners. Here, we demonstrate that through the 3D nanopatterning of
chiral single
crystal helimagnets into nano-
tori, the controlled formation of a
magnetic double helix can be achieved. This surface-localized topological state is stabilized by the interplay of intrinsic exchange interactions of the single
crystal with the extrinsic emergent effects of the patterned geometry. These double helices host
magnetic defects akin to supercoiling in circular DNA and climbing vines. We expect this study to serve as a foundation for future research combining single
crystal systems with 3D nanopatterning, offering a new degree of control over emergent phenomena in nanoscale magnets and wider
quantum material systems.
Read the full abstract ▾
All authors Luke Alexander Turnbull, Max Thomas Birch, Marisel Di Pietro Martínez, Rikako Yamamoto, Jeffrey Neethirajan, Marina Raboni Ferreira, Elina Zhakina, Hayden Jeffrey Binger, Young-Gwan Choi, Rachid Belkhou, Simone Finizio, Markus Weigand, Dieter Suess, Daniel Alexander Mayoh, Geetha Balakrishnan, Claas Abert, Sebastian Wintz, Claire Donnelly
Materials Science · Cross-listed from cs.LG
Toward Multi-Fidelity Machine Learning Force Field for Cathode Materials
Guangyi Dong and Zhihui Wang
Machine learning force fields (MLFFs), which employ neural networks to map atomic structures to system energies, effectively combine the high accuracy of first-principles calculation with the computational efficiency of empirical force fields. They are widely used in computational materials simulations. However, the development and application of MLFFs for lithium-ion battery cathode materials remain relatively limited. This is primarily due to the complex electronic structure characteristics of cathode materials and the resulting scarcity of high-quality computational
datasets available for force field training. In this work, we develop a multi-fidelity machine learning force field framework to enhance the data efficiency of computational results, which can simultaneously utilize both low-fidelity non-
magnetic and high-fidelity
magnetic computational
datasets of cathode materials for training. Tests conducted on the lithium manganese iron phosphate (LMFP) cathode material system demonstrate the effectiveness of this multi-fidelity approach. This work helps to achieve high-accuracy MLFF training for cathode materials at a lower training
dataset cost, and offers new perspectives for applying MLFFs to computational simulations of cathode materials.
Read the full abstract ▾