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Sunday 16 August

Applied Physics

A Passive Daytime Colored Radiative Cooler with DBR-Engineered Color Selectivity

Rajib Lochan Ghadei, Rohit Gupta and Rishi Maiti

Passive daytime colored radiative cooling (PDCRC) offers an attractive approach to thermal management while enabling structural coloration. However, achieving both strong daytime cooling and vivid, stable colors remains challenging. Here, we propose a lithography-free PDCRC comprising a polydimethylsiloxane (PDMS) emitter, SiC/SiO2 distributed Bragg reflector (DBR), MgF2 spacer, and Ag back reflector. The DBR and MgF2 spacer enable selective visible-spectrum reflection for cyan, magenta, and yellow (CMY) color generation, while the PDMS layer provides strong thermal emission within the atmospheric transparency window (8-14 micrometers). Finite-difference time-domain (FDTD) simulations, validated using the transfer matrix method (TMM), yield an average emissivity of 92% in the atmospheric window and an average reflectivity of 93.3% over 0.75-6 micrometers. CIE 1931 chromaticity analysis confirms high-contrast CMY colors with low color differences from standard subtractive primary colors. Under daytime conditions with a heat-transfer coefficient of 6 W m-2 K-1, the proposed cooler achieves cooling powers of approximately 140-145 W m-2 and a temperature reduction of about 12 degrees C below ambient. The color characteristics remain stable over a broad range of incidence angles, with only a gradual reduction in color intensity at larger angles, while the spectral response remains nearly insensitive to TE and TM polarizations. Simulations using meteorological conditions from different global cities further demonstrate robust cooling performance under diverse environmental conditions. The combination of high cooling performance, vivid coloration, simple multilayer architecture, and fabrication feasibility makes the proposed PDCRC promising for energy-efficient thermal management in buildings, vehicle coatings, wearable devices, and other outdoor applications.
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Saturday 15 August

Applied Physics · Cross-listed from math-ph

Disentangling Measurement Protocol from Material Physics in Isotypic and Anisotypic SiC/Si Heterojunctions: A Metrology-Driven Study for Betavoltaic Energy Conversion

Mikhail V. Dolgopolov

We compare isotypic (n-SiC/n-Si) and anisotypic (n-SiC/p-Si) heterojunctions using Kelvin probe force microscopy, scanning tunnelling spectroscopy, precision electrical measurements with a Keithley 2450 SourceMeter, and a 0.1 farad supercapacitor charge-storage test. Two-wire probing shows an enhanced low-bias current in the isotypic structures; four-wire Kelvin sensing removes the voltage-drop contribution of external leads and contacts and collapses this current to a much lower bulk and interface limited level. The high density of interface states detected by KPFM and STS, up to five times ten to the twelfth per square centimetre per electronvolt in dislocation-rich regions, provides a plausible origin for the enhanced local response. Anisotypic junctions exhibit a genuine diode-like current-voltage characteristic and an open-circuit voltage of about 1.2 volts under beta irradiation. In the capacitor test with the patented charge-pump converter, the anisotypic structure reaches 0.25 volts versus 0.05 volts for the isotypic one after 30 minutes, giving an energy ratio of about 25. We formulate a measurement-interpretation framework based on four-wire Kelvin sensing, generator polarity with cathode to LO, and high-impedance output-off state. Our results show that anisotypic SiC/Si heterojunctions are the preferred platform for betavoltaic conversion when measured correctly.
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Applied Physics · Cross-listed from physics.acc-ph

Relative and absolute dosimetric commissioning of the ELIMAIA–ELIMED laser-driven proton beamline at 23.4 MeV

G.A.P. Cirrone, G. Petringa, A. Kurmanova et al. (+12 more)

The development of laser-driven proton beamlines for biomedical and radiobiological applications requires traceable dosimetry and reliable online monitoring at the irradiation point. In this work, we report the relative and absolute dosimetric commissioning of the ELIMAIA–ELIMED laser-driven proton beamline at ELI Beamlines using an energy-selected proton beam with an average energy of about 24~MeV. Radiochromic-film measurements were used to characterize the transverse dose distribution, the depth–dose profile, and the proton energy spectrum at the irradiation point. The reconstructed spectrum was centred at $23.45~\mathrm{MeV}$ with a FWHM of $2.60~\mathrm{MeV}$, while the transverse dose distribution showed an approximately $5.5~\mathrm{mm}$ field size with a millimetre-scale homogeneous region. The Faraday Cup was used as the absolute reference detector for dose to water determination and for cross-calibrating the Dual-Gap Ionization Chamber, which was operated as the primary online dose monitor. The Integrating Current Transformer and Secondary Electron Monitor were evaluated as upstream relative beam monitors. An independent RCF–FC dose comparison performed over fifty consecutive shots yielded $30.45 \pm 3.5~\mathrm{cGy}$ from the FC and $36.46 \pm 1.8~\mathrm{cGy}$ from the EBT3 film. Dedicated G4ELIMED Monte Carlo simulations showed that the RCF positioned upstream of the FC perturbs the FC measurement through proton losses outside the FC acceptance and through an increase in the effective beam area at the FC entrance. Applying the resulting correction factor, $C_{\mathrm{MC}}=1.109$, reduced the residual difference between the FC- and RCF-derived doses to about $7\%$. These results establish the dosimetric chain of the ELIMAIA–ELIMED beamline under the present low-fluence commissioning conditions and identify the operational limits of the online monitoring system.
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All authors G.A.P. Cirrone, G. Petringa, A. Kurmanova, R. Catalano, A. Amato, A. Pappalardo, M.G. Guarrera, F. Schillaci, P. Blaha, F. Grepl, M. Tryus, A. Velyhan, L. Giuffrida, D. Margarone, G. Cuttone

Applied Physics · Cross-listed from cond-mat.mtrl-sci

DINO4DSTEM: A self-supervised framework for structural discovery in 4D-STEM

Daniel Khaykelson, Lothar Houben and Boris Rybtchinski

Nanodiffraction using 4D-STEM has become a key technique for quantitative nanoscale structural mapping in materials research, yet interpreting its high-dimensional datasets in structurally complex materials remains a major bottleneck. Existing analysis workflows typically rely on structural models, manual annotation, predefined classes, or sample-specific heuristics, limiting their ability to characterize heterogeneous complex materials. Here, we introduce DINO4DSTEM, a self-supervised machine learning framework that automatically discovers structurally meaningful states directly from raw diffraction data. Without structural models, manual labels, a predefined number of classes, or system-specific parameter tuning, the framework learns representations that organize diffraction patterns by their intrinsic structural similarities, transforming large collections of low-dose measurements into quantitative nanoscale structure maps. Across diverse datasets, DINO4DSTEM consistently identifies the dominant structural degrees of freedom, providing segmentation without human supervision. We applied the framework to the crystallization of indomethacin, a beam-sensitive, multidomain pharmaceutical system, revealing that crystallinity emerges from a partially ordered precursor and spans a continuous spectrum of structural order. The discovered nanoscale structural states are mapped to reveal the evolution of order across the specimen quantitatively. By replacing task-specific analysis with general self-supervised representation learning, DINO4DSTEM provides a broadly applicable framework for quantitative nanoscale structural mapping in complex materials, enabling the discovery of emergent structural organization in heterogeneous, beam-sensitive systems.
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Applied Physics

Voltage-Controlled Phosphate Precipitation Gating in Solid-State Nanopore Memristors

Weihong Wang, German Lanzavecchia, Ali Douaki et al. (+9 more)

Nanofluidic memristors preserve a record of electrical activity via ion migration and alterations in conductance that depend on the history of the device s state. These characteristics make them suitable for aqueous, energy efficient, and biologically compatible neuromorphic systems. To establish the viability of fluidic memristors for mimicking the brain s dynamic behavior, a more thorough understanding of the memristive materials and the underlying switching processes is required. In this study, we systematically examined a recently introduced memristive device based on inpore chemical reactions, where the combined influence of electrolyte composition and pore architecture on precipitation gated memory remains poorly understood. To address this, we constructed an asymmetric electrochemical system using CaCl2 and phosphate solutions separated by SiNx solid state nanopores. We explored how variations in pH, phosphate concentration, pore geometry, and voltage pulsing regimens affect the electrical characteristics and memristive performance. Comparison of the single pore and the array showed that parallel pores produced smoother pH and concentration dependent hysteresis and pulse responses, whereas the single pore retained larger, nonmonotonic changes.
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All authors Weihong Wang, German Lanzavecchia, Ali Douaki, Shukun Weng, Yanqiu Zou, Huaizhou Jin, Alberto Giacomello, Lorenzo Iannetti, Roman Krahne, Shangzhong Jin, Makusu Tsutsui, Denis Garoli

Friday 14 August

Applied Physics

Aperiodic temporal modulation for distortionless broadband impedance matching beyond the Bode-Fano limit

Martin Olguin-Lopez, Dimitrios L. Sounas, Nader Engheta et al. (+2 more)

The Bode-Fano bound sets a fundamental trade-off between bandwidth and reflection in passive, linear, time-invariant matching networks. We show that an aperiodically time-modulated reactive element can emulate the non-Foster response required to match a prescribed pulse, achieving reflectionless, nearly distortionless energy transfer beyond the Bode-Fano limit. The approach introduces a new constraint: a minimum dc bias that scales with pulse bandwidth, derived from the requirement that the modulated capacitance remain positive at all times. This modulation-bias bound replaces the classical bandwidth-reflection trade-off with a bandwidth-energy trade-off. A realistic circuit simulation confirms broadband matching with preserved waveform fidelity, demonstrating that the scheme is physically realizable and not merely a mathematical circumvention.
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All authors Martin Olguin-Lopez, Dimitrios L. Sounas, Nader Engheta, Andrea Alù, Mario J. Mencagli

Thursday 13 August

Applied Physics

Operator-Level Description of Transient Thermal Grating Dynamics Across Transport Regimes

Slobodanka Galovic and Steva Jacimovski

Transient thermal grating (TTG) experiments provide a powerful means of probing material properties and resolving their dynamics at small spatio-temporal scales through the temporal response to a spatially periodic excitation. However, quantitative interpretation of the measured transient requires a forward model that consistently connects energy deposition, subsequent transport, and detection within the finite space-time window of the experiment, for which such a formulation is still lacking in TTG. Here, we formulate a continuum, operator-based TTG forward model in which the physical processes from energy deposition to detection of the evolving spatial mode are treated within a unified transfer-function framework. Thermal transport dynamics is represented by a temporal memory kernel, allowing unresolved relaxation processes to be incorporated at the scale of experimental observability without imposing an a priori microscopic transport mechanism. The formulation provides a basis for inferring effective material properties and the dynamics resolved within the experimental window, which can subsequently be related to material-specific microscopic degrees of freedom and their interactions. In addition, analysis of the resulting TTG transients shows that the observability of flux memory is not equivalent to the presence of oscillations in the measured response. Oscillations provide a clear signature when finite flux-relaxation dynamics becomes resolved on the experimental time scale, whereas their absence does not imply the Fourier limit. Memory can instead remain observable through non-oscillatory modifications of the transient shape and characteristic time scales.
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Applied Physics · Cross-listed from cond-mat.mes-hall

Strong photoresponse of edge two-dimensional electrons in a magnetic field

Sergey A. Mikhailov and Wladislaw Michailow

Electrons in two-dimensional electron gases in the presence of an out-of-plane magnetic field propagate along the edge with a high velocity of the order of the Fermi velocity. Under microwave and terahertz radiation, photon absorption by these electrons provides a pathway to realising sensitive radiation detection. Here, we develop a detailed quantum theory of the photocurrent generated in such a system by an incident electromagnetic wave and propose an experimental geometry for observing the predicted phenomenon. By using suitably arranged radiation confinement structures, a strong photocurrent generation efficiency can be obtained. We also demonstrate that the resulting photoresponse in III-V semiconductor structures can be orders of magnitude higher than that measured in graphene.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci

Thickness-dependent secondary-electron emission from suspended MoS$_2$ membranes in the helium ion microscope

Cyan Kim, David Lister, Philip Jackle et al. (+1 more)

Secondary-electron (SE) emission in the helium ion microscope (HIM) becomes sensitive to membrane thickness when the sample is thin enough for He-ion transmission and when the SEs emitted from the bottom surface are collected. We correlated the total SE intensity of suspended, nanometer-thick MoS$_2$ flakes on lacey carbon with thickness measured independently by electron energy-loss spectroscopy. The response peaks at 40-55 nm, with an apparent back-to-front SE signal ratio reaching 4.7. The peaked, thickness-dependent component is attributed primarily to SE emission at the bottom surface of the flake, rather than to transmitted ions striking instrument surfaces. Applying SRIM ionization profiles, an asymmetric SE-escape model with a longer escape depth on the exit side reproduces the response. We find an effective exit-side escape depth of approximately 10 nm, five times the assumed 2 nm entrance value, suggesting that deposited energy reaches the exit surface far more efficiently than the entrance surface or that the SRIM model's energy deposition profile is shifted by an effect such as channeling. The correlation provides a rapid thickness screen for suspended membranes and a route to testing low-energy ion-solid interaction models in thin materials.
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All authors Cyan Kim, David Lister, Philip Jackle, Karen L. Kavanagh

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Thermal transport in crystals: from the quantum Dyson equation to mesoscopic phonon hydrodynamics

Enrico Di Lucente, Michele Simoncelli and Nicola Marzari

Thermal transport in dielectric, non-magnetic crystals is mediated by quantized lattice vibrations, which drift and interact when driven out of equilibrium by a temperature gradient. This phenomenon can be described at multiple theoretical levels, ranging from fully quantum descriptions to semiclassical and mesoscopic continuum approaches. This review rigorously discusses the theoretical steps and approximations connecting these levels, bridging quantum phonon Dyson and Kadanoff-Baym equations and semiclassical Boltzmann transport formalism, and discussing the coarse-graining procedures that yield mesoscopic viscous heat equations for non-diffusive, hydrodynamic heat transport in devices. We show how the Guyer-Krumhansl and dual-phase-lag equations emerge as special linear-isotropic-band and inviscid limits of the viscous heat equations, respectively; most importantly, we demonstrate that these equations predict not only Poiseuille flow and second sound, but also more exotic effects such as negative thermal resistance, steady-state thermal backflow and vortices. We highlight how combining these frameworks with first-principles simulations connects microscopic phonon physics to observable non-diffusive heat-transport phenomena and guides their detection, amplification, and control. We recast the viscous heat equations in terms of Helmholtz and biharmonic equations solved analytically, and use this to discuss similarities and differences between the macroscopic behavior of the phonon fluid and other hydrodynamic systems, such as classical and electron fluids, focusing on compressibility, vorticity, and their influence on phonon hydrodynamics. We conclude with a roadmap to generalize the tools used to describe phonon hydrodynamics to other quasiparticles, motivating future advances in collective quantum transport phenomena in solids.
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Applied Physics

Origin of effective non-Fourier heat conduction phenomena in heterogeneous materials

Róbert Kovács

Phenomenological models of non-Fourier heat conduction often lack a strict microstructural foundation, leading to ambiguities when modeling complex heterogeneous materials. In this study, we derive a continuum heat equation beyond Fourier's law using spatial volume averaging for a two-component system. We analytically prove that the experimentally observed static and dynamic thermal diffusivity arise directly from the distinct material properties, concluding that heterogeneous media are inherently over-diffusive. The resulting heat equation is thermodynamically compatible, and the microstructural origin allows the calculation of non-Fourier transport coefficients. Furthermore, we demonstrate that finite-sample boundaries introduce higher-order spatial non-localities, thereby explaining the size dependence of over-diffusion. We validate the model against experimental data across metal and carbon foams, rocks, and metal-organic frameworks.
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Applied Physics · Cross-listed from physics.optics

Bioinspired Microactuators Fabricated via One-step Meniscus-guided 3D Nanoprinting

Seong-Jae Eom, Vasanthan Devaraj, Sunghyun Kwak et al. (+4 more)

We introduce a bioinspired microactuator fabricated via a one-step meniscus guided 3D nanoprinting technique. This technique directly produces a freestanding three dimensional composite architecture by integrating a rigid nanoparticle framework with a hygroscopic polymer matrix in a single, assembly free process. Inspired by the functional integration of rigid and compliant components in insect exoskeletal joint, our design synergistically combines load-bearing strength and humidity-driven swelling in a single microscale pillar. Comprehensive experiments, including comparative control structures and microscopic analysis, elucidated the actuation mechanism: the nanoparticle scaffold provides mechanical support while the polymeric phase provides volumetric expansion, yielding large reversible elongation under humidity with preserved structural integrity. The resulting AuNP PVP microactuator shows humidity responsive actuation at the microscale, with representative demonstrations of repeated humidity cycling and load lifting up to approximately 800 times its estimated own weight under the tested conditions. Variant geometries such as hinged pillars demonstrate how axial swelling can be converted into bending motion, and an optical configuration shows how actuation can modulate reflected light signals. This nanoprinting approach provides a simple strategy for constructing bioinspired soft microactuators with humidity-responsive deformation and potential applicability in microscale sensing, optical modulation, and adaptive microdevices.
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All authors Seong-Jae Eom, Vasanthan Devaraj, Sunghyun Kwak, Hyeon-Seok Seo, Thomas Zentgraf, Won-Geun Kim, Jong-Min Lee

Applied Physics

Vertical Gallium Oxide Isolated Source Electrode Field Effect Transistors (ISEFET) Without Planarization or Mid-Gap Acceptor Blocking Layers

Akilesh Srikanth, Md Saklain Morshed, Chandan Joishi et al. (+2 more)

We propose and demonstrate the first vertical Gallium oxide device architecture without the use of planarization etch back processes or mid-gap acceptor regions. The Isolated Source Electrode Field Effect Transistor (ISEFET) incorporates a dielectric blocking layer to access an isolated source pad extending from the top fin metal. Scaled multi-fin channels were formed by electron beam lithography with a width of 200 nm along with the source pads and then etched to a trench depth of ~1.2 um. The fabricated devices showed enhancement mode operation with threshold voltage of 2 V and on-off ratio > 1e7 with excellent gate modulation characteristics. The resulting device proved to be comparable to existing vertical transistors and suitable for high-throughput prototyping and large-scale manufacturing of future Gallium oxide and other wide bandgap semiconductor devices.
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All authors Akilesh Srikanth, Md Saklain Morshed, Chandan Joishi, Ahmad E. Islam, Siddharth Rajan

Wednesday 12 August

Applied Physics · Cross-listed from eess.SP

Feasibility and Convex Design of Probe-Position Matching in a Scanning X-Band Radar Array

William Khalili Jr

The probe position of a microstrip element is normally chosen from the isolated-element input resistance. This paper replaces that procedure with a decision available before any array optimisation. A single Floquet unit-cell solution at one arbitrary probe position is decomposed into a feed inductance, a transformer ratio carrying the probe position, and an array-loaded resonator. Three closed-form results follow. The set of input impedances reachable by probe position and resonant length is a disk in the impedance plane. An exact match to a real reference Z0 exists if and only if Rp >= Z0 + Xp^2/Z0. When this fails, the best attainable reflection follows from the image of that disk under the bilinear map. Admitting one series reactance as a second variable, the worst-case reflection over a scan sector is shown to be quasiconvex and globally solvable by bisection. The results are applied to a sixteen-element X-band array and the corresponding 16x24 lattice. For the array considered, the isolated interior element is matched to -16.94 dB while the broadside active reflection is -6.6 dB. For the two-dimensional lattice the criterion is violated at every scan angle, and the minimax design improves the worst-case sector reflection from -2.6 to -11.1 dB. Both matching designs are predictions of the extracted circuit model and have not been re-solved in the full-wave model.
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Applied Physics

Measurement of third-order elastic constants using thermal modulation of ultrasonic waves

Bibo Zhong and Jinying Zhu

Third-order elastic constants (TOEC) play an important role in nonlinear material characterization, but measurements of TOEC are laborious with large error margins. This Letter presents the equations of wave velocity changes caused by homogeneous temperature variation and uniaxial stress in isotropic media and the expression of TOEC in terms of thermally induced velocity change and thermal strain. TOEC of an aluminum sample were experimentally determined by measuring ultrasonic wave velocity changes in the uniaxial loading test and the thermal modulation test. Experimental results showed good agreement between the two test methods. Owing to the simple test setup and high measurement sensitivity, the thermal modulation test is a potential experimental method to determine TOEC and absolute acoustic nonlinearity parameters.
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2608.12244 · 12 Aug · 1. Corrected a sign typo in Eq. (6d) relative to the original APL publication. 2. The final TOEC values might be affected by minor temperature variations during testing; for further discussion, see Zhu et al., Nondestructive Testing and Evaluation, 41(7), 4066-4089 (2026), DOI: 10.1080/10589759.2025.2551866

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Applied Physics · Cross-listed from physics.med-ph

A 2D Hydrothermodynamic Analytical Model for Rapid Tumor Ablation using High-Intensity Focused Ultrasound

D. Tsiklauri

We establish a self-consistent 2D hydrothermodynamic analytical model for high-intensity focused ultrasound tumor ablation. Expanding compressible Navier-Stokes equations to second order demonstrates that a stationary cellular matrix suppresses acoustic streaming ($\mathbf{v}_2 = 0$). This constraint forces the absorbed wave momentum flux to convert entirely into localized, time-averaged static pressure gradients ($\nabla \langle p_2 \rangle = \mathbf{F}_2$), bridging non-linear hydrodynamics with thermodynamic dissipation. Solving the non-diffusive Pennes bioheat equation under a $1.0\,\text{s}$ top-hat pulse reveals that a spherically focusing geometry ($\propto 1/r^2$) overrides exponential damping past a critical geometric threshold ($r_{\text{crit}} = 2x_0$), preventing upstream skin overheating. We derive an optimization criterion where the absorption coefficient matches half the inverse target depth ($\alpha = 1/2x_0$). Solving the non-isothermal Arrhenius integral yields a sharp lesion boundary radius at $r_b = 0.75\,w_0$, where the volume average reaches $72.1^\circ\text{C}$ while the core peaks at $90.0^\circ\text{C}$. Post-pulse 2D free-space Green's function convolution confirms immediate monotonic thermal decay ($\partial \theta/\partial t' < 0$) outside this boundary. This closed-form framework provides explicit scaling laws for non-invasive wave-matter thermal confinement, bypassing computationally heavy numerical simulations.
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Applied Physics · Cross-listed from eess.SP

Effects of Tool Wear on the Surface Texture in Turning: A Feature Characterization Approach Based on ISO 21920-2

Alexander Müller, Maximilian Berndt, Hagen Schmidt et al. (+5 more)

The surface texture of a turned component acts as a fingerprint of both the process parameters and the tool wear condition, imaging the cutting edge. Classical surface parameters such as $R_\mathrm{a}$ or $R_\mathrm{q}$ describe the topography only globally and allow no spatially resolved evaluation of the process-induced deterministic structures. This work investigates how far the feature characterization standardized in ISO 21920-2 makes this wear information accessible and physically interpretable. The database comprises roughness profiles of twelve AlTiN-coated carbide inserts (CNMG120408) machining normalized AISI 1045 steel, measured at nine wear states over the entire tool life, with three replicate profiles per state. The correlation of standardized field and feature parameters with crater wear, flank wear, and cutting time is first examined. Watershed segmentation is then adapted to extract the rotational tool grooves and evaluate their geometry statistically. A newly developed mean-feature approach decomposes the profile into a deterministic and a stochastic component. Wear-induced changes are almost entirely carried by the deterministic component, and within it by the trailing flank of the cutting groove. A comparison with confocal measurements confirms that the mean feature reconstructs the engaged cutting edge geometry, with the trailing-flank steepening attributable to notch wear on the secondary cutting edge. An exhaustive evaluation of more than 920,000 feature characterization combinations and multivariate models reveals that the groove-level mean maximum absolute gradient $\overline{R_\mathrm{dt}}_\mathrm{groove}$ alone explains 83-90% of the variance of the wear indicators, so that a single, physically motivated parameter suffices for robust wear estimation. A follow-up study will investigate inline monitoring using scattered light sensors.
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All authors Alexander Müller, Maximilian Berndt, Hagen Schmidt, Lars Müller, Matthias Eifler, Eberhard Kerscher, Benjamin Kirsch, Jörg Seewig

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Thermoelastic Harvesting Outperforming Thermoelectric Generators Below 100 {\deg}C

Bruno Neumann, Andreas Henschke, Morik Nikolic et al. (+1 more)

Low-grade waste heat below 100 degC is one of the largest untapped opportunities in solid-state energy conversion. Three ferroic routes are candidates for recovering this resource: thermomagnetic, pyroelectric, and thermoelastic harvesters. The last has remained the most unexplored, despite decades of progress on the underlying NiTi shape-memory alloy wires. Three system-design changes close this gap: a protagonist-antagonist architecture that recovers the energy for prestraining, a continuously tunable prestrain mechanism that sets the force-strain balance, and transversal water flow that decouples cycle frequency from wire length. The resulting harvester delivers a directly measured power density of 366 mW/cm^3 with respect to the active material, about 1.7 times the next-best thermoelastic device, ahead of every reported thermomagnetic and pyroelectric generator, and outperforming the best thermoelectric generators in this temperature range also with respect to power per material cost. The system maps the parameter space directly through force and displacement measurements, without using material-property estimates, giving a quantitative picture of how the alloy responds while the device is doing work.
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All authors Bruno Neumann, Andreas Henschke, Morik Nikolic, Sebastian Fähler

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Electronic structure, band offset, and interface electron population of the LaInO$_3$/BaSnO$_3$ system

G. Hoffmann, A. A. Riaz, C. Kalha et al. (+7 more)

Perovskite oxides and their heterostructures exhibit a wide range of functional properties. Among these materials, BaSnO$_3$/LaInO$_3$ heterostructures form high-mobility two-dimensional electron gases (2DEGs) at their interfaces. In particular, room-temperature electron mobilities exceeding 100~cm$^2$/Vs were enabled by recent advances in thin-film growth. This work presents a combined experimental and theoretical study of the electronic structure of BaSnO$_3$, LaInO$_3$, and BaSnO$_3$/LaInO$_3$ heterostructures with varying LaInO$_3$ overlayer thicknesses. Soft and hard X-ray photoelectron spectroscopy (SXPS and HAXPES) measurements are combined with densities of states (DOS) derived from hybrid density functional theory (DFT) calculations. The analysis of core, semi-core, and valence states allows to arrive at a comprehensive understanding of the chemical bonding and electronic structure in the parent oxides as well as the formed heterostructures. For the BaSnO$_3$/LaInO$_3$ heterostructure, the band offset and population of 2DEG states at the interface is directly probed using HAXPES.
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All authors G. Hoffmann, A. A. Riaz, C. Kalha, A. Gloskovskii, C. Schlueter, O. Brandt, W. Aggoune, C. Draxl, O. Bierwagen, A. Regoutz

Applied Physics · Cross-listed from cond-mat.mtrl-sci

Magneto-optical magnetoelectric voltage sensor

Michael P. Path and Jeffrey McCord

Applications in high-voltage and electromagnetically harsh environments require reliable galvanically isolated voltage sensing, which can be achieved using optical readout. While established optical voltage sensors rely on electro-optic effects or piezoelectric strain with direct optical detection, strain-mediated magnetoelectric coupling combined with magneto-optical readout offers an alternative voltage sensing principle that remains largely unexplored. Here, such a sensor based on a bismuth-substituted yttrium iron garnet magneto-optical indicator film mechanically coupled to a piezoelectric actuator is presented. Voltage induced stress results in changes of the out-of-plane magnetization via magnetoelastic coupling which is detected through magneto-optical Faraday rotation. A critical state of the domain structure is set via an applied bias field, in which voltage-induced nucleation and domain-wall motion dominates the response. In this high sensitivity regime, both AC and DC voltage readout modes are demonstrated, based on either voltage-driven magnetization reversal or voltage-induced modifications of the magnetization loop shape. Equivalent voltage noise densities in the millivolt per root hertz range are achieved. The results establish strain-mediated magneto-optical voltage sensing as a distinct approach to optically isolated voltage measurement.
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Applied Physics · Cross-listed from cs.CV

Automated binary classification of hazelnut X-ray images: A deep-learning benchmark for quality assessment

Giancarlo Sportelli, Nicola Belcari, Roberta Pace et al. (+4 more)

Non-destructive X-ray imaging can reveal internal hazelnut defects that are difficult to detect by external inspection alone; however, automated interpretation remains challenging because of subtle radiographic differences among classes, marked class imbalance, and limited annotated data. Here, we present a benchmark for binary hazelnut quality classification (healthy versus defective) based on 799 segmented single-kernel X-ray images (224 x 224 pixels, grayscale), grouped into 101 acquisition units. Seven single-model configurations and ten probability-aggregation ensembles were evaluated using a group-wise split-rotation protocol across five data splits generated using different random seeds. Decision thresholds were selected on the validation set, and performance was assessed deterministically on validation and test sets. Under the expert-reassessed annotation condition, the average-probability ensemble of the binary cross-entropy-trained convolutional neural network and frozen Swin Transformer achieved the highest mean balanced accuracy (86.3% +/- 1.8%, five seeds), with several other ensembles providing comparable performance. Across methods, substantial split-to-split variability was observed, indicating that multi-split evaluation is essential for reliable model comparison at this dataset scale. Expert reassessment of ambiguous samples improved the performance of all 17 evaluated methods by 2.8-8.1 percentage points, while having only a limited effect on cross-split variance. The results highlight both the potential of deep learning for automated X-ray-based hazelnut quality assessment and the importance of rigorous evaluation and label curation in small, imbalanced agricultural imaging datasets.
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All authors Giancarlo Sportelli, Nicola Belcari, Roberta Pace, Umberto Bernardo, Sharmin Sultana, Alessandra Toncelli, Matteo Giaccone

Applied Physics · Cross-listed from physics.optics

Near-Unity Excitation and Radiative Efficiencies in Electroluminescence Without External Carrier Injection

Rui Li, Xinrui Li, Jiachen Xie et al. (+8 more)

Electroluminescence occurring without external charge injection is typically characterized by weak emission and excessive driving voltage, due to low excitation and radiative recombination efficiencies. Here, we demonstrate non-injecting electroluminescence (NI-EL) that challenges this conventional perception. To achieve this, we introduce an operational paradigm that leverages remote, state-abundant charge reservoirs, which elevates the excitation efficiency close to unity - a greater-than-20-fold improvement over the benchmark. This strategy is augmented by quantum dots (QDs) with nonmonotonically graded shells, raising the high-field radiative efficiency by approximately 7-8-fold. The resultant RGB NI-EL devices uniformly exhibit bright and efficient pulsed emissions, with key metrics including: a turn-on threshold of 3.7 Vrms for red; a luminance of 291,628 nits and a power efficiency of 302.6 lm/W for green, with light-outcoupling enhancement; and, for blue, the superior emitter stability of the first QD-based blue NI-EL over its light-emitting diode counterpart. The minimal dielectric loss, sub-100 ns response time, and external EL efficiency of up to 45.4% further reinforce the mechanism-performance causality. These results overcome the inherent mechanistic limitations of NI-EL and establish performance that rivals or surpasses injection-type EL, including AC- or DC-driven variants, positioning NI-EL as a promising platform for high-performance pulsed light sources.
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All authors Rui Li, Xinrui Li, Jiachen Xie, Pingjun Xu, Wen Li, Congcong Liu, Zheng Ge, Longjia Wu, Xingtong Chen, Zheming Liu, Song Chen

Applied Physics

A Frequency-Space Terahertz Transceiver Chip for Multi-Agent Communications and Spatial Awareness

Xiaoyue Xia, Zhicheng Lin, Hao Guo et al. (+7 more)

Future indoor embodied-intelligence systems require scalable hardware platforms that support both high-capacity multi-agent connectivity and mutual spatial awareness. The terahertz (THz) spectrum offers abundant bandwidth and inherent spatial selectivity for integrated sensing and communication (ISAC); however, conventional phased arrays and programmable metasurfaces rely on dense beamforming networks, element-level control, or external THz illumination, making scalable multibeam operation challenging. Here, we report a fully integrated 208-258GHz 65-nm CMOS THz transceiver chip that monolithically integrates broadband front ends with heterogeneous leaky-wave metasurface (HLM) apertures within a 1.5mm by 4.9mm area. The HLM generates strongly dispersive leaky modes, enabling 75 degree frequency-controlled beam scanning with only four meta-atoms. Co-design of frequency-domain and spatial-domain mixing achieves spectrally clean frequency-to-space mapping for spatial-frequency division multiple access (SFDMA) communication. The THz chip demonstrates multi-agent simultaneous transmission and reception, two-dimensional localization, and sensing-enhanced communication, providing a scalable hardware platform for future THz embodied-intelligence networks.
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All authors Xiaoyue Xia, Zhicheng Lin, Hao Guo, Siran Wang, Jingyuan Zhang, Xinyu Fang, Ka Fai Chan, Shum Kam Man, Geng-Bo Wu, Chi Hou Chan

Applied Physics · Cross-listed from physics.chem-ph

Simulating Ionic Liquid Fragmentation in Electrospray Thrusters with Foundation Models

Ziyu Huang

Predicting the products of ionic-liquid impacts on extractor surfaces is important for electrospray-thruster lifetime analysis, yet available atomistic methods require a compromise between chemical fidelity and computational cost. Reactive force fields enable high-throughput sampling but do not explicitly resolve electronic charge redistribution and may miss relevant reaction pathways during impact, whereas mixed quantum–classical density-functional-theory molecular dynamics (DFT/MD) can capture charge redistribution and neutral-product formation at substantially higher computational cost. Pretrained atomistic foundation models have recently emerged as a potential route toward DFT-like chemical fidelity at considerably lower cost. Here, we benchmark two pretrained machine-learning interatomic potentials, MACE-MP-0 (medium) and MACE-POLAR-1, against DFT/MD and ReaxFF for geometry optimization of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF$_4$) and for 10-100 eV impacts on a model Au extractor surface. The models reproduce several collision outcomes observed in DFT/MD, including ionic dissociation, high-energy covalent fragmentation, and, in particular, HF formation through neutralization-like chemistry that is not captured in the ReaxFF simulations. In the computational-performance benchmark, MACE-POLAR-1 and MACE-MP-0 (medium) completed each 2~ps trajectory in 5.12 and 2.54~min, respectively, corresponding to wall times approximately four orders of magnitude shorter than the DFT/MD reference under the reported benchmark conditions. These results support pretrained machine-learning potentials as a practical intermediate-cost approach for chemically resolved electrospray-impact simulations and motivate targeted fine-tuning with DFT data for broader applications in electrospray-thruster and electric-propulsion modeling.
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Tuesday 11 August

Applied Physics · Cross-listed from physics.ins-det

Cusp-singularity-enhanced Coriolis effect for ultrasensitive chip-scale gyroscopes

Sen Zhang, Dingbang Xiao, Fei Wang et al. (+8 more)

Gyroscopes, as fundamental inertial sensors, are crucial for rotation measurements in consumer electronics, automotive, and aerospace industries, with the most widely used kind relying on the Coriolis effect. The chip-scale Coriolis vibratory gyroscopes (CVGs) show reduced size, weight, and cost, but remain far lower performance than traditional macroscale CVGs, as the weak intrinsic Coriolis factor sets a fundamental limit on scaling the sensitivity against the inherently louder Brownian noise in microchips compared to the macroscale ones. Here, to overcome this physical limit, for the first time, we propose and experimentally demonstrate the use of third-order singularities lying within cusp catastrophes in the phase-tracked oscillations of an on-chip CVG to facilitate a cubic-root scaling of the Coriolis-effect-induced frequency modulation. Employing this effect, we achieve a three-order-of-magnitude enhancement in the Coriolis factor, yielding a 253-fold improvement in signal-to-noise ratio and a 297-fold increase in precision. Moreover, the cusp singularity enables a previously unattainable ultrasensitive phase-modulated sublinear measurement, achieving a world-record signal-to-noise ratio performance for silicon-chip gyroscopes. These findings not only provide revolutionary advancements in gyroscope technologies, by filling the gap in observing and controlling the singularity-enhanced Coriolis effect, but also shed new light on other ultrasensitive sensing applications.
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All authors Sen Zhang, Dingbang Xiao, Fei Wang, Ran Huang, Lei Yu, Ning Zhou, Kaixuan He, Xuezhong Wu, Franco Nori, Hui Jing, Xin Zhou

Applied Physics · Cross-listed from physics.ins-det

Compact nondestructive generator for microsecond-class ultrafast pulsed magnetic fields

Y. Ishii, A. Ikeda, H. Sun et al. (+2 more)

The sweep rate of pulsed magnetic fields is a key factor in exploring of nonequilibrium phenomena in matter. However, the nondestructive generation of ultrafast pulsed magnetic fields is challenging because of the large time constants associated with the large inductance and capacitance of conventional pulsed magnetic field generators, as well as the residual inductance of the power devices and the system itself. We have developed a new compact pulsed magnetic field generator using commercially available state-of-the-art ultrafast power devices, enabling the generation of ultrafast pulsed magnetic fields up to approximately 1 T with a pulse duration of 3.8 $\mu$s. We present the performance of the newly developed system and compare the experimentally obtained magnetic field waveforms with the results of a simple circuit simulation. In addition, we demonstrate magnetization measurements on cobalt powder and Faraday rotation measurements on CdS single crystal using the developed system.
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All authors Y. Ishii, A. Ikeda, H. Sun, H. Oike, Y. H. Matsuda

Applied Physics

SERS study of single-live-cell electrical permeabilization dynamics via plasmonic nanotubes

Yuge Liang, Peilin Xin, Enock Adjei Agyekum et al. (+6 more)

There is a growing demand for minimally invasive methods to analyze intracellular processes and signaling activities in individual living cells, including the identification of tumorigenic cell subpopulations. However, most conventional analytical methods require cell lysis, precluding repeated measurements in the same cell over time, or rely on exogenous labels and reporters that may perturb cellular function. Various applications based on vertical nanotubes have been developed that enable live cell monitoring and analysis by electroporation with low voltages. However, the extent and duration of membrane permeability and kinetics of membrane repair remain elusive. Here, we built a plasmonic platform with the capacity of surface enhanced Raman spectroscopy (SERS) to monitor the electroporation-induced membrane permeability dynamics in individual live cells attached onto 100-nm diameter nanotubes of 2 um height. Fibronectin was employed as extracellular matrix (ECM)-coating to facilitate cell attachment onto nanotubes. Using fluorescent-dye delivery as an independent validation method, we show that the fabricated nanostructures induce localized electrical permeabilization of the plasma membrane and enable monitoring of its subsequent recovery. We further use SERS to track molecular changes at the membrane during permeabilization and resealing. The SERS spectra provide molecular-level insight into changes in membrane-associated components and the ECM during electroporation and subsequent membrane recovery. Real time monitoring of pulse induced molecular changes holds great promise for characterizing intracellular signaling, cellular states, and cellular heterogeneity at the single cell level, including the identification of tumorigenic subpopulations. This capacity could facilitate the development of novel biosensing assay.
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All authors Yuge Liang, Peilin Xin, Enock Adjei Agyekum, Jiaming Zhang, Yingqi Zhao, Jinglai Duan, Francesco De Angelis, Aki Manninen, Jianan Huang

Applied Physics · Cross-listed from cond-mat.mes-hall

Dynamics of amorphous membranes in the two-dimensional limit

Liga Jasulaneca, Alberto Martín-Pérez, Hongji Zhang et al. (+7 more)

Atomically thin mechanical resonators have been realized predominantly in crystalline two-dimensional (2D) materials, such as graphene, where long-range crystalline order sets their elastic properties and defines their nonlinear resonant behavior. Extending these concepts to the amorphous 2D limit has remained largely unexplored. Here, we demonstrate that monolayer amorphous carbon (MAC) forms suspended membranes that support optothermal actuation and sensitive interferometric readout across both linear and nonlinear regimes of its resonant motion. We resolve thermomechanical motion, driven resonances, and multimode spectra in MAC nanodrums. The frequencies of fundamental vibration modes correspond to unusually low pretensions, placing monolayer MAC nanodrums in a regime where geometric nonlinearities, stress heterogeneity, and mode coupling emerge at comparatively low drive powers. Consistently, we observe pronounced nonlinear dynamics, including hardening, softening, and mixed Duffing responses, nonlinear damping, parametrically excited modes, and signatures of intermodal coupling. These results establish MAC as a robust nanoelectromechanical platform and open an experimental route to disorder-governed nanomechanics in the 2D amorphous limit.
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All authors Liga Jasulaneca, Alberto Martín-Pérez, Hongji Zhang, Prertahn Munireternam, Natalia A. Mamchik, Chee-Tat Toh, Artem K. Grebenko, Barbaros Özyilmaz, Makars Šiškins, Farbod Alijani

Applied Physics · Cross-listed from cond-mat.stat-mech

Equilibrium Distributions for Strongly Nonlinear Many-Body Systems

Jialin Zhang, Yong Zhang and Hong Zhao

Obtaining equilibrium distributions of nonlinear systems is essential for accurately computing macroscopic observables. Conventional theoretical corrections are typically limited to weak nonlinearities, where interaction terms can be treated as effectively uncorrelated perturbations and the random phase approximation applies. In this Letter, we develop a framework to determine equilibrium distributions based on the generalized energy equipartition principle. Our approach recovers existing corrections in the weakly nonlinear regime and, crucially, remains valid for strong nonlinearities, where perturbative contributions become correlated and conventional approaches break down. Numerical simulations of the nonlinear Schrödinger equation, the Majda-McLaughlin-Tabak model, and the Fermi-Pasta-Ulam-Tsingou model demonstrate accurate corrections for nonlinearities more than an order of magnitude stronger than those accessible to conventional theories.
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Monday 10 August

Applied Physics · Cross-listed from cs.ET

Unsupervised Detection of Groundwater Storage Anomalies in Ghana Using GRACE Satellite Data

George Yamoah Afrifa, Theophilus Ansah-Narh and Marcellin Atemkeng

Groundwater variability in Ghana remains poorly characterized due to limited long-term in-situ observations. This study investigates groundwater storage anomalies using GRACE-derived data from 2004-2024 combined with statistical analysis and unsupervised machine learning. Groundwater anomalies were standardized using Z-scores, while an ensemble-based Isolation Forest framework was applied for anomaly detection. The results revealed substantial temporal variability, with persistent groundwater deficits during 2004-2009 followed by increasing positive anomalies after 2018. A total of 12 anomalous months were identified, comprising 5 deficit and 7 surplus events, with the strongest anomalies associated with groundwater deficits. Spatial analysis showed more frequent deficit anomalies in northern Ghana and stronger surplus occurrence in southern regions. Comparison with statistical thresholds further indicated that the machine learning framework captured additional subtle deviations beyond conventional threshold-based methods. Overall, the integration of GRACE observations with unsupervised anomaly detection provides a practical framework for groundwater monitoring in data-scarce environments.
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