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Monday 31 August

Applied Physics · Cross-listed from physics.optics

Revealing antenna-molecule coupling using virtual gain from synthetic complex frequency analysis

Toby Severs Millard, Xiaofei Xiao, Mayela Romero-Gómez et al. (+6 more)

Synthetic complex frequency waves (CFWs) enhance spectral and spatial resolution by compensating loss through virtual gain. This approach is particularly useful in nano-photonics where loss is intrinsically linked to strong field confinement and system size. Here, we apply CFWs to metasurfaces composed of Fano-resonant plasmonic antennas with lithographically tunable coupling between the weak and strong coupling regimes and where loss may be reduced to the Drude damping limit. We quantitatively assess the impact of the virtual gain to find that, while reducing loss, internal coupling rates remain invariant. While the exceptional point associated with strong light-matter coupling is invariant under virtual gain, the cooperativity of Fano interference is enhanced. When the metasurfaces are functionalised with a molecular monolayer, CFWs are thus able to reveal a molecule's vibrational modes, even when obscured by loss, and allow direct extraction of the plasmon-molecule coupling strength. We thus use CFW analysis as a quantitative tool for revealing and assessing light matter-coupling.
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All authors Toby Severs Millard, Xiaofei Xiao, Mayela Romero-Gómez, Tom Aktaş-Vincent, Nathaniel J. Huáng, Chris C. Phillips, Stefan A. Maier, Olga Kazakova, Rupert F. Oulton

Sunday 30 August

Applied Physics · Cross-listed from cond-mat.soft

A unified geometric design framework for kirigami structures

Qinghai Jiang and Gary P. T. Choi

In recent years, kirigami metamaterials have been widely studied and applied in science and engineering. While various two- and three-dimensional kirigami design methods have been developed, most of them are only applicable to a limited class of kirigami structures. In this work, we develop a unified framework for kirigami design that encompasses a wide range of 2D-to-2D, 2D-to-3D, and 3D-to-3D shape-morphing effects, as well as additional geometric and physical properties such as compact reconfigurability and rigid deployability. In particular, by reformulating the design task as a length-based constrained optimization problem and solving it simultaneously for multiple target states of the kirigami structure, our unified design framework enables greater design flexibility and stronger theoretical support. Experimental results with a wide range of shape-morphing effects are presented to demonstrate the effectiveness of our framework. We further present a rigorous theoretical analysis of several key aspects of kirigami design, covering inertia transposition, aspect-ratio law, and angle defects, thereby elucidating important design rules and limitations. Altogether, our work paves a new way for the design of shape-morphing mechanical metamaterials.
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Applied Physics · Cross-listed from cs.LG

Diffusion-Based Inverse Design of Dielectric Resonator Metasurfaces for Shaping Smart Electromagnetic Environments

M. Tsukerman, K. Grotov, D. Vovchuk et al. (+1 more)

Future wireless systems are expected to transform the surrounding space from a passive propagation medium into a smart electromagnetic environment, where engineered surfaces control wave propagation, support wireless sensing, and create programmable electromagnetic fingerprints. A key challenge in realizing this vision is the inverse design of metasurfaces for tailored electromagnetic propagation. While forward analysis evaluates the response of a known geometry, the inverse task starts from a prescribed scattering signature and seeks a physically realizable structure that produces it. This inverse task is inherently nonlinear and often high-dimensional, while candidate solutions may be non-unique and provide no direct indication of practical realizability. Here, we introduce a conditional diffusion framework for inverse design of dielectric resonator metasurfaces from target angular scattering patterns. Trained on T-matrix simulated geometry-response pairs, the model learns a conditional distribution of geometries instead of a deterministic mapping, enabling multiple candidate designs for the ill-posed inverse problem. The best generated metasurface achieves a mean percentage error of 1.39%, outperforming CMA-ES optimization (4.1% after 10 h) while requiring only about one minute for after-training inference. The model also produces lower error distributions than deterministic neural baselines for out-of-distribution spectra, highlighting the potential of diffusion models for efficient metasurface design.
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All authors M. Tsukerman, K. Grotov, D. Vovchuk, P. Ginzburg

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

Harnessing the skyrmion Hall effect for low-power skyrmion transport in a tubular synthetic antiferromagnet

Ivan P. Miranda, Grzegorz J. Kwiatkowski, Jacob J. Mankenberg et al. (+4 more)

We show that optimal control can turn the skyrmion Hall effect from a source of typically unwanted transverse motion into a mechanism for reducing Ohmic losses in skyrmion transport. We consider a pair of antiferromagnetically coupled skyrmions confined to a tubular geometry, where their relative transverse displacement becomes a periodic internal coordinate. The skyrmion Hall effect drives this coordinate, while finite interlayer coupling makes the resulting relation between applied current and longitudinal velocity nonlinear, allowing different current protocols to produce the same prescribed average velocity. We determine which of these protocols minimizes Joule heating. Depending on the interlayer coupling and spin-transfer-torque parameters, the optimal current is either constant, with the skyrmion pair maintaining a fixed relative position, or time dependent, with the pair undergoing periodic relative motion around the tube. In either case, the additional internal degree of freedom created by the skyrmion Hall effect and interlayer coupling enables skyrmion transport at a lower power than in the uncoupled limit.
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All authors Ivan P. Miranda, Grzegorz J. Kwiatkowski, Jacob J. Mankenberg, Cecilia M. Holmqvist, Igor S. Lobanov, Valery M. Uzdin, Pavel F. Bessarab

Saturday 29 August

Applied Physics

Advancing Lead-Free FASnI3 Perovskite Solar Cells via Cu-Doped NiOx HTL Engineering: An Optoelectronic Analysis

Md. Faiaad Rahman, Jabed Hasan, Md. Ashaduzzaman Niloy et al. (+1 more)

Efficient lead-free perovskite solar cells remain limited by inefficient charge transport and significant recombination losses. In this work, copper (Cu) doped nickel oxide (NiOx) is employed as the hole transport layer (HTL) in a formamidinium tin iodide (FASnI3) perovskite solar cell to improve hole extraction and suppress carrier losses. The optoelectronic response of the proposed device architecture is evaluated through a coupled numerical framework combining finite-difference time-domain (FDTD) optical simulations with finite element method (FEM)-based electrical modeling. Electrical analysis solves the Poisson equation together with the drift-diffusion and carrier continuity equations, while accounting for radiative, non-adiative, and interfacial recombination mechanisms. Systematic optimization of the thicknesses and doping concentrations of the constituent layers was performed to establish a high-performance device configuration. Following optimization of layer dimensions and carrier densities, the device achieved a power conversion efficiency (PCE) of 24.71%. Integrating an anti-reflection coating (ARC) effectively suppressed reflection losses, yielding a 5.47% relative enhancement in PCE. Consequently, the optimized device achieved a peak PCE of 26.06%, with a short-circuit current density (Jsc) of 28.98 mA/cm2, an open-circuit voltage (Voc) of 1.051 V, and a fill factor (FF) of 85.64%. These findings demonstrate that Cu-doped NiOx functions as a highly promising HTL to boost charge collection and maximize overall efficiency in lead-free FASnI3 solar cells.
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All authors Md. Faiaad Rahman, Jabed Hasan, Md. Ashaduzzaman Niloy, Ahmed Zubair

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

Evaluating LLM-based AI agents integrated with materials synthesis tools: the case of atomic layer deposition

Angel Yanguas-Gil

This work provides an overview of the different strategies that can be used to evaluate the performance of AI models and agents based on large language models (LLMs) for materials synthesis. After providing a brief overview of the key technologies behind the current generation of AI agents based on LLMs, we summarize the different approaches to evaluating these models in the context of materials science and in particular on materials synthesis, with a specific emphasis on scenarios in which the models are directly integrated with experimental tools. We discuss evaluation strategies spanning knowledge and reasoning benchmarks, tool-use benchmarks, and closed loop benchmarks involving the interaction with experimental systems or realistic virtual tools. We use atomic layer deposition (ALD) as a case study, emphasizing how existing approaches in the literature both build from general approaches used beyond materials science and can be generalized to other materials synthesis techniques. Finally, we provide a practical evaluation framework to evaluate LLMs in the context of materials synthesis
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Applied Physics · Cross-listed from nlin.AO

Perturbation responses on topological synchrony in simplicial Kuramoto model

Abhijeet Kumar, Palash Kumar Pal and Dibakar Ghosh

Synchronization is conventionally understood as the emergence of a phase-locked collective state among interacting dynamical units. However, extending this notion to systems whose dynamical variables are defined on higher-dimensional simplices introduces fundamentally new constraints arising from the topology of the underlying simplicial complex. In the simplicial Kuramoto model, nontrivial topological cycles give rise to a higher dimensional harmonic subspace that is unaffected by the coupling and can therefore drift indefinitely, preventing a globally synchronized state. To resolve this we employ Hodge decomposition on simplicial Kuramoto dynamics and investigated the components. Despite this topological obstruction, we show that the simplicial Kuramoto model admits fixed-point states in the exact and coexact sectors of the Hodge decomposition above critical coupling strengths, which we derive analytically for both sectors. This decomposition provides a generalized notion of synchronization in which the non-harmonic components converge to fixed states. We further investigate the robustness of these fixed-point states to external perturbations. Excluding the drifting and non-interacting harmonic component, the perturbation response is governed by the spectrum of weighted Laplacian and recovers a Kirchhoff index dependence analogous to standard Kuramoto case. In contrast, the harmonic sector is non-dissipative, and consequently the fragility of the system increases with the dimension of this topological subspace. We characterize this effect numerically using triangulated tori with varying first Betti number and find a superlinear scaling relation between system fragility and the dimension of the harmonic sector.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci

Directional commensurability stabilizes structural superlubricity in patterned mesoscale interfaces

Viet Hung Ho, Ge Li, Melisa M. Gianetti et al. (+3 more)

Structural superlubricity, arising from lattice incommensurability, offers a promising route to eliminate friction and associated energy losses in mechanical systems. In real-world systems, roughness and wear currently pose severe limitations on its robustness and especially the contact size. Here, we consider patterned surfaces as a possible route to overcome some of these limitations. We show that the simplest choice of patterning, contacts made up of two incommensurate triangular-triangular patterns, fails at elevated loads because of the small number of load-bearing contacts, causing the maximum local contact pressure to exceed the strength of the superlubric coating. We introduce a square-triangular patterned interface that increases the number of load-bearing contacts and organizes them into continuous contact lines. When sliding along specific directions relative to these lines, superlubricity is maintained at significantly higher loads by reducing pressure-induced coating failure while also remaining somewhat tolerant to surface imperfections. These findings establish a mechanism for stabilizing structural superlubricity against coating failure and a design principle for engineering low-friction interfaces with enhanced load-bearing capacity and defect tolerance.
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All authors Viet Hung Ho, Ge Li, Melisa M. Gianetti, Bjørn Haugen, Graham L. W. Cross, Astrid S. de Wijn

Friday 28 August

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

Giant staggered Dzyaloshinskii-Moriya vectors emerged in synthetic antiferromagnets with spatially alternating stress

Yuuga Iwata, Kensuke Hayashi, Reiju Furumaki et al. (+3 more)

Dzyaloshinskii-Moriya (DM) interaction is a source of chiral magnetic physics, and it manifests microstructural symmetry which could link to exotic magnetic and electronic properties such as altermagnetism. For a new paradigm in magnetism and spintronics, it is crucial to have control on the DM interaction as well as ordering of the DM vectors which characterize the DM interaction. Here, we report on a strong interlayer DM interaction emerged in Co/Ru magnetic superlattices whose structural symmetry is unambiguously broken by alternating mechanical strains developed using the peculiar technique of our stress mechanism. Moreover, theoretical analyses reveal that our magnetic superlattices host a staggered order of the DM vectors. Our results indicate that the spatially varying strains with our breakthrough technique are quite effective in breaking the symmetry of the system and prove that it can control the DM interaction strength as well as the DM vector order.
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All authors Yuuga Iwata, Kensuke Hayashi, Reiju Furumaki, Satoshi Iihama, Masahiro Sato, Takahiro Moriyama

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

Electrochemical impedance spectroscopy of graphene nanogaps

Patrick A. McKee, Chris S. DeMellier, Robin N. Schipper et al. (+1 more)

Graphene nanogaps represent an emerging platform for nanoscale electrochemical and sensing devices, with potential applications in next-generation biomolecular sequencing. However, their interfacial behavior in aqueous environments remains poorly characterized, particularly with respect to frequency-dependent impedance and charge transport mechanisms at the graphene edge. We fabricate graphene nanogaps by controlled electrical breakdown in an inert atmosphere and study their electrochemical response. Upon exposure to ambient conditions, a surface contamination layer supports electrochemical activity within an adsorbed ultrathin conductive film between the graphene edges. Electrochemical impedance spectroscopy reveals distinct frequency-dependent responses consistent with a Warburg element associated with diffusion in this confined interfacial film. The impedance evolves systematically with liquid $\mathrm{p}H$, reflecting changes in electrochemical reaction-diffusion processes at the graphene edges. A quantitative equivalent-circuit model captures these effects and enables extraction of an effective nanogap length scale from impedance spectra, providing information complementary to that obtained from tunneling measurements.
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All authors Patrick A. McKee, Chris S. DeMellier, Robin N. Schipper, Henk W.Ch. Postma

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

Statistical Properties of a Fluctuation-Driven Nanomechanical Duffing Resonator

Monan Ma, Nathan Welles, Johnathon Barbish et al. (+5 more)

We investigate the fluctuating nonlinear dynamics of multiple modes of a nanomechanical doubly clamped beam resonator. Each mode is driven by Gaussian force noise centered around the resonance; the mode response is monitored while the force magnitude is increased, inducing a transition from harmonic to the nonlinear Duffing regime. To characterize the dynamics, we introduce an effective temperature based on the mode fluctuation amplitude. As the nonlinearity becomes prominent at large amplitudes, we observe a reduction in the effective thermal energy and a crossover in response statistics from Gaussian to platykurtic, consistent with the dynamics expected in a Duffing potential.
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All authors Monan Ma, Nathan Welles, Johnathon Barbish, Ismet I. Kaya, M. Selim Hanay, Oleksiy Svitelskiy, Mark R. Paul, Kamil L. Ekinci

Applied Physics · Cross-listed from quant-ph

Beyond sensitivity: mechanism-resolved error budgets for designing quantum sensors

Nima Leclerc, Marco Capelli, Kevin James Rietwyk et al. (+14 more)

Quantum sensors are specified by a headline sensitivity, yet applications also demand accuracy and reliability. The dominant limiter of one metric is often known, but no method resolves how interacting mechanisms combine into a signed, per-mechanism budget for each metric. We introduce a framework that computes a sensor's sensitivity, accuracy, and robustness from one open-system simulation and attributes each to its limiting mechanism. For a nitrogen-vacancy diamond ensemble the attribution inverts across metrics: dephasing limits sensitivity, the thermal ground-state shift limits accuracy, and optical leakage limits robustness. At identical sensitivity the recovered-field bias spans $8$ to $1500$\,nT, so tuning to sensitivity alone can miss the accuracy target by two orders of magnitude. The same modeling transfers to a cesium optically pumped magnetometer recording a human magnetocardiogram. As a digital twin, it predicts the gain from addressing each limiter, so sensors can be designed to the required metrics.
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All authors Nima Leclerc, Marco Capelli, Kevin James Rietwyk, Mark Dong, Dmitry Lyakh, Geoffrey Iwata, Brandon Rodenburg, Sean Oliver, Benedikt Kloss, Jin-Sung Kim, Stefan Bogdanovic, Yunheng Chen, Meysam Sharifzadeh Mirshekarloo, Cedric Weber, Marcus Doherty, Ethan Pratt, Joseph Hagmann

Applied Physics

Synergy between laser linewidth and frequency chirp in mesospheric magnetometry based on the sodium laser guide star

Yucheng Yang, Chunyang Lei, Kai Guo et al. (+1 more)

Mesospheric sodium magnetometry with a laser guide star measures the geomagnetic field near 90~km. Its sensitivity hinges on laser linewidth and chirp, yet prior work optimized these two parameters only separately. We use velocity-resolved density-matrix simulations of Larmor-synchronous pulsed Na D$_2$ pumping to scan both parameters jointly. Linewidth and chirp exhibit a synergy: when chirping carries the recoil-mitigation role, the return flux stays within 1% of its peak across linewidths of 2–10~MHz. The flux-optimal chirp is $0.19~\mathrm{MHz/\upmu s}$, one fifth of the continuous-wave rate; this synergy guides high-sensitivity mesospheric magnetometer design.
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All authors Yucheng Yang, Chunyang Lei, Kai Guo, Shuai Wang

Applied Physics · Cross-listed from physics.optics

Correlation Swapping: a correlator for independent thermal light sources

Wanting Hou, Jilun Zhao, Zhiyuan Ye et al. (+4 more)

Optical intensity correlation is a fundamental property of light and an essential resource for numerous optical applications. In this work, we introduce the concept of classical correlation swapping, a classical analogue of quantum entanglement swapping, to generate all-purpose spatial correlations between two independent thermal light sources. Using a spatially unresolved Mach-Zehnder interferometer and a medium variable, we theoretically and experimentally demonstrate the feasibility of the correlator with two distinct schemes for independent pseudo-thermal light beams. Notably, the resulting photon correlations can be readily tailored to exhibit either bunching (peak) or anti-correlated (dip) characteristics, with a significantly reduced number of post-selection measurements. Leveraging this classical correlator, we further demonstrate the first classical ghost imaging experiment using uncorrelated or unknown light. Numerical simulations also confirm that the correlator can not only operate well in other spatial degrees of freedom (e.g., orbital angular momentum) but also be used to establish specific spatial correlations between pseudo-thermal light sources possessing distinct correlation properties. This work opens a new avenue for harnessing uncorrelated classical light in correlation-based optical applications.
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All authors Wanting Hou, Jilun Zhao, Zhiyuan Ye, Hong-Chao Liu, Hai-Bo Wang, Jun Xiong, Kaige Wang

Applied Physics · Cross-listed from physics.optics

High-performance silicon-metal laser welding resisting extreme conditions

Jiawei Yin, Markus Blothe, Hagen P. Kohl et al. (+3 more)

Reliable material joining is essential for countless industrial applications. While femtosecond laser welding provides a route beyond conventional bonding methods, demonstrations of silicon-metal joints are rare due to nonlinear propagation effects and have so far been limited to shear joining strengths of a few MPa. Here, we demonstrate high-strength silicon-Kovar laser welding using sub-nanosecond pulses. By optimizing the focal position, the welding pattern, the laser polarization, and the metal roughness, remarkable shear joining strengths up to 15.8 MPa are achieved. The silicon-metal joints withstand temperatures of up to 500 {\deg}C and are hermetically sealed. Together with the remarkable strength values, the resistance to harsh environments underpins the applicability of silicon-metal welding in various fields including aerospace, nuclear science, and metallurgy.
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All authors Jiawei Yin, Markus Blothe, Hagen P. Kohl, Christina Schütze, Stefan Nolte, Maxime Chambonneau

Applied Physics

Beating the nonreciprocal isolation limit of integrated circulators by Floquet leakage interference

Zhe Zhang, Haoye Qin, Junda Wang et al. (+5 more)

Time-modulation using semiconductor switches is a promising route to magnetless integrated nonreciprocal devices, as they can offer large modulation depths and high speeds. Yet, chip-scale devices are capped by the finite off-state capacitance of the switches, which induces detrimental leakage of the input wave to the isolated port, imposing a ceiling on the nonreciprocal isolation. Such leakage has largely constrained the development of nonreciprocal integrated systems at high frequency. Here, we beat this limit by using Floquet interference between leakages. In a time-Floquet switched-resonator circulator, two coherent leakages reach the isolated port: the release of the stored wave at the resonator's ring-down frequency, and the direct input leakage at the carrier frequency. We show that it is possible to create conditions under which the two leakages destructively interfere, and even completely cancel, yielding perfect isolation despite operating with non-ideal semiconductor switches. We experimentally confirm leakage interference in a 65-nm CMOS microwave Floquet circulator, reaching 40-dB isolation, which is more than 20 dB higher than the natural switch isolation. We also demonstrate that leakage interference has inherently fast dynamics, establishing itself within a single modulation period, allowing us to reverse the circulation chirality in 0.6~ns. Our results pave the way toward high-frequency integrated chips with ultra-high nonreciprocal isolation.
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All authors Zhe Zhang, Haoye Qin, Junda Wang, Qiaolu Chen, Zhechen Zhang, Alireza Mafi, Ahsan Altaf, Romain Fleury

Applied Physics · Cross-listed from cond-mat.soft

How a polymer filling enhances the rate and selectivity of colloid permeation across mesopores

Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter et al. (+2 more)

Polymer-functionalised mesopores are an emerging technology for colloid separation, sensing and delivery. Their potential is strikingly illustrated in living cells, where nuclear pore complexes (NPCs) control biocolloid transport between the nucleus and the cytosol. Even colloids much smaller than the biopolymer-filled NPC channel are effectively blocked, but some larger colloids with distinct surface features rapidly permeate. Simplistically, one may expect any polymer filling to obstruct and slow down colloid transport. We demonstrate how a polymer filling that attracts colloids and extends beyond the mesopore, thus maximizing colloid capture, can instead increase permeation compared to a bare pore. We also define how polymer-filled mesopores can effectively gate colloids according to their size and surface features. Our findings provide a basic physical explanation for the exquisite permselectivity of NPCs, and a rational design strategy for novel mesopore-based separation, sensing, catalysis and drug delivery devices with enhanced performance features.
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All authors Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter, Leonid I. Klushin, Oleg V. Borisov

Applied Physics · Cross-listed from physics.optics

Compact Variational Neural Networks for Spectral Inference from a Single Nonlinear 2D Perovskite Photodetector

Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam et al. (+4 more)

Spectroscopy conventionally separates optical frequencies before detection, imposing persistent constraints on footprint, complexity and scalability. Here we establish an alternative paradigm in which the nonlinear optoelectronic dynamics of a single two-dimensional perovskite photodetector physically encode the incident optical field and machine learning performs the inverse spectral reconstruction. Using a planar fluorinated phenethylammonium lead iodide (F-PEAI) photodetector, we exploit wavelength- and irradiance-dependent current-voltage signatures arising from the coupled effects of photocarrier generation, trapping, interfacial transport and field-dependent carrier dynamics. A compact variational encoder-decoder preserves the functional and history-dependent structure of these responses by independently projecting forward and reverse voltage sweeps onto a truncated Legendre-polynomial basis before mapping them through a probabilistic latent representation to continuous spectral parameters. Trained on fewer than 400 experimental voltage sweeps, the model generalises to excitation wavelengths excluded from training, reconstructing wavelength with $R^2=0.958$ and a mean absolute error of 8.1 nm, while recovering log-normalised irradiance with $R^2=0.987$. Voltage-resolved analysis further reveals that wavelength and irradiance are encoded differently across the nonlinear device response, with distinct bias regions carrying complementary optical information. These results establish nonlinear material and interface dynamics as a computational resource for spectroscopy and point towards hardware-algorithm co-design in which materials, interfaces and inference architectures are engineered jointly to maximise information content, enabling compact spectroscopic systems without dispersive optics or detector arrays.
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All authors Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam, Rosanna Mastria, Francesco Saverio Difeo, Monica Felicia Craciun, Saverio Russo

Applied Physics

Extending the operating window of scanning electron microscopy through an integrated electron-optical architecture for high-temperature and near-ambient-pressure environments

Yue Chai, Honglong Zhao, Xinning Tian et al. (+2 more)

Scanning electron microscopy (SEM) under simultaneously high-temperature, near-ambient-pressure (NAP), and reactive-gas environments requires coordinated control of vacuum isolation, electron-beam transmission, signal generation, and thermal management, constraints that have long limited the operating window of environmental scanning electron microscopy (ESEM). Here we establish an integrated electron-optical architecture that combines a multistage differential-pressure pathway, front-stage pressure transition, detector optimization, thermal management, and a gas-focusing sampling architecture into a unified ESEM platform. Pressure distribution and electron-beam transmission are quantitatively validated through computational fluid dynamics (CFD), Monte Carlo electron-gas scattering analysis, and direct beam-current measurements, while detector optimization and thermionic-electron suppression preserve stable imaging under elevated pressure and temperature. The resulting system enables stable SEM imaging at pressures up to 20,000 Pa and high-temperature imaging up to 1,400 degrees C, continuous observation of hydrated biological specimens, and synchronized SEM-QMS operando characterization using local gas sampling. These developments establish a general electron-optical framework for extending ESEM toward realistic operando environments where elevated temperature, reactive gases, structural evolution, and gas-phase chemistry can be investigated simultaneously.
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All authors Yue Chai, Honglong Zhao, Xinning Tian, Chao Ang, Zhu-Jun Wang

Thursday 27 August

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

Frequency Synchronization Circuit Model for Analog Vector-Matrix Multiplication in the Frequency Domain

Taeju Lee, Scott T. Habermehl, Timothy W. Caplice et al. (+3 more)

This work introduces a frequency synchronization circuit model for analog vector-matrix multiplication in the frequency domain. The frequency synchronization is implemented by coupling oscillators through all-to-all connections. Each oscillator is implemented using complementary cross-coupled transconductance pairs and RC high-pass filters. In this work, the frequency synchronization is achieved not only using oscillators alone but also through a configuration in which oscillators and resonator models (i.e., MEMS/NEMS resonators) are combined. While addressing the frequency synchronization of all the coupled oscillators, a partial synchronization is also discussed by controlling the coupling strength of a selected subset of oscillators. This frequency synchronization analysis focuses on the small-signal analysis using analog circuit and resonator models, thereby enabling an understanding of the synchronized frequency defined by the parameters of the analog circuit and resonator models.
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All authors Taeju Lee, Scott T. Habermehl, Timothy W. Caplice, Michael L. Roukes, Philip X.-L. Feng, Kenneth L. Shepard

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

Physics-informed learning for the inverse problem in resonant ultrasound spectroscopy

Alejandro Cubillos Muñoz, Manuela Rivas and Julian Rincon

Inferring elastic constants from resonant ultrasound spectra is a nonlinear and typically overdetermined inverse problem based on finite spectral data. We formulate the Rayleigh-Ritz inverse problem as a constrained inverse-isospectral problem on the set of physically admissible elasticity tensors. This induces effective low-dimensional variables for the inverse map on the admissible elasticity manifold: length and elastic scales, aspect-ratio coordinates, scale-free spectral features, and stability-respecting elastic ratios. We use these variables to construct a physics-informed learning pipeline in which a regression model acts only on reduced spectral and geometric features, while scale recovery and final elastic-constant reconstruction are imposed analytically. For the full cubic benchmark, the reconstructed constants have MAE values of $20.37(35.15)$, $24.30(41.33)$, and $2.13(3.66)~\mathrm{GPa}$ for $C_{11}$, $C_{12}$, and $C_{44}$. In the fixed-geometry benchmark, the corresponding cubic MAPE values are $4.14(3.87)\%$, $8.31(8.50)\%$, and $2.44(2.86)\%$, while the isotropic values are $4.0(3.6)\%$ and $0.4(0.3)\%$ for the bulk and shear moduli. The inverse problem then becomes a constrained regression problem in variables adapted to the geometry, scaling, crystal symmetry, and thermodynamic stability of Hookean elasticity.
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Applied Physics

Compact Modeling of Oxide-Semiconductor, 2D Material, Carbon Nanotube, and Cryogenic Transistors with Experiment Verification

Chien-Ting Tung

This paper presents a unified compact model for emerging transistor technologies, including oxide-semiconductor field-effect transistors (OSFETs), 2D material FETs (2DFETs), carbon nanotube FETs (CNFETs), and cryogenic MOSFETs. A unified charge-density formulation is developed to account for quantum confinement, trap charges, and band-tail states in channel charge calculations. A physics-based transport model is introduced to seamlessly capture carrier transport from the long-channel diffusive regime to the short-channel ballistic limit. Scaling models are incorporated to accurately describe 2D electrostatic effects. Cryogenic operation is modeled through the inclusion of band-tail states and temperature-dependent mobility and threshold voltage. The proposed model is validated against experimental data from the fabricated OSFETs with multiple channel lengths and published measurements of 2DFETs, CNFETs, and cryogenic MOSFETs. Excellent agreement is demonstrated across diverse device architectures, operating conditions, and material systems.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci

Exact branch-transfer criterion for common-mode Thomson heat cancellation in thermoelectric couples

Peng Kang, Da Wan, Shulin Bai et al. (+7 more)

Thermoelectric p- and n-type legs are commonly paired by matching their Seebeck magnitudes, although a cooler responds to heat transported through its complete electrical and thermal network. We decompose the leg coefficients into differential thermopower $\alpha=S_p-S_n$ and common thermopower $M=(S_p+S_n)/2$. In a connected steady-state scalar thermoelectric network, a temperature-independent co-shift applied to every electrically active segment is an exact terminal null. A temperature-dependent perturbation of the legs relative to fixed leads is instead physical. At fixed current and shared isothermal endpoints, its first-order cold-port response is the action of $\Gamma_m=T\,dm/dT$ on the difference between the p- and n-branch oriented collection measures. We prove that every continuous $\Gamma_m$ cancels if and only if these measures are equal. In the constant-property, linear-common-mode limit, matching $R_i/K_i^{\rm leg}$ is sufficient and does not require identical legs. One- and two-dimensional calculations confirm the analytic reductions within their stated domains. For split thermal pads, the analysis gives the exact array law $\Delta Q_{c,\Sigma}=\sum_j C_jI_j\Delta T_{c,j}$ and, for series elements with isothermal hot pairs, $I\Delta V_\Sigma=-\Delta Q_{c,\Sigma}$. A representative seven-pair model gives corresponding increments of 7.87 mW and $-2.80$ mV. Branch transfer and endpoint topology therefore provide distinct material-pairing and device-test criteria for common-mode Thomson heat.
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All authors Peng Kang, Da Wan, Shulin Bai, Wei Yin, Peng Wang, Chenglong Wen, Zhen Li, Yu Liu, Lei Zheng, Li-Dong Zhao

Applied Physics

Hyperuniformity as a unifying organizational principle across diatom architectures

Eric Ballestero, Chiara Gazzola, Raj Kumar Pal et al. (+2 more)

Diatom frustules have long fascinated scientists for the extraordinary beauty, diversity, and functionality of their intricate silica architectures. Yet, the spatial organization of these structures has so far been primarily described in terms of morphology, symmetry, and crystallographic order, leaving common statistical properties across distinct diatom architectures largely unexplored. By analyzing diatom frustules through the lens of hyperuniformity for the first time, we reveal a striking commonality across their remarkable diversity: all analyzed genera exhibit signatures of suppressed long-wavelength density fluctuations. Specifically, we find that these architectures range from strongly ordered Class I to disordered Class III hyperuniform systems. We show that local order, spatial correlations, and long-range fluctuation suppression can vary partially independently, giving rise to a continuous spectrum of multiscale architectures. Our multiscale approach reveals that hyperuniformity can be reliably characterized in finite biological structures, beyond what conventional asymptotic diagnostics can resolve. Together, these results prove that hyperuniformity provides a unifying statistical framework for describing diatom diversity beyond conventional classifications of structural order.
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All authors Eric Ballestero, Chiara Gazzola, Raj Kumar Pal, Vicent Romero-Garc{\i}a, Marco Miniaci

Applied Physics

Diamond quantum-sensing platform with integrated boron-doped diamond microwave antenna and thermometer

Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi et al. (+5 more)

Wide-field nitrogen-vacancy (NV) magnetic imaging at cryogenic temperatures requires microwave excitation and reliable knowledge of the temperature near the sensing region. Here, we report an integrated diamond quantum-sensing platform combining an ensemble of NV centers with a boron-doped diamond (BDD) microwave antenna and thermometer formed on the same diamond substrate. The BDD antenna provides microwave excitation for optically detected magnetic resonance measurements, and the BDD thermometer monitors the thermal environment near the NV sensing region. The BDD thermometer detected laser-induced local heating that was not clearly resolved by a stage-mounted thermometer. Using this platform, we imaged the temperature-dependent Meissner response of multiple cuprate superconductors while recording the temperature. These results demonstrate that the integrated BDD–NV platform provides a practical approach for cryogenic wide-field magnetic imaging with integrated microwave delivery and local thermometry.
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All authors Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi, Shinobu Onoda, Kensei Terashima, Takao Watanabe, Yoshihiko Takano, Keigo Arai

Applied Physics

Diatom frustules as naturally occurring resonant microarchitectures: revealing vibrational eigenmodes across pennate and centric species

Chiara Gazzola, Dame Fall, Stefano Stassi et al. (+3 more)

Diatom frustules, the hierarchically structured, species-specific silica exoskeletons of diatom microalgae, are among Nature's most sophisticated examples of bottom-up self-assembly, exhibiting nanoscale porosity, multifunctional mechanical and optical properties, and a morphological diversity that spans nearly three orders of magnitude in size. Despite growing interest in their optical and static mechanical properties, the elastodynamic behaviour of frustules has remained largely unexplored. Here we report the first experimental detection and spatially resolved reconstruction of vibrational eigenmodes in diatom frustules, combining laser Doppler vibrometry with morphology-faithful finite-element models informed by scanning electron microscopy (SEM) and focused-ion-beam scanning electron microscopy (FIB-SEM). Two morphologically contrasting taxa were investigated as model systems: the pennate diatom Rhaphoneis amphiceros and the centric diatom Stictodiscus californicus var. nitida, spanning the two principal branches of diatom diversity. Four eigenmodes were identified for R. amphiceros in the 5.90-14.17 MHz range and three for S. californicus in the 9.96-17.62 MHz range; the simulations yield a complete modal landscape for each species, including modally split and nearly degenerate eigenmodes arising from deviations from ideal symmetry, and show quantitative agreement with the experimentally measured mode shapes and resonant frequencies. These results establish diatom frustules as a class of naturally occurring resonant microarchitectures, and open new avenues for their integration as bio-derived functional elements in nanomechanical and MEMS/NEMS applications.
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All authors Chiara Gazzola, Dame Fall, Stefano Stassi, Marc Duquennoy, Marc Serra Garcia, Marco Miniaci

Applied Physics

Ternary-Valued Finite-Difference Time-Domain Method: Asymptotic Agreement with the Yee Scheme Through Noise-Shaped Quantisation

Ivan S. Maksymov

I show that finite-difference time-domain (FDTD) dynamics can be reproduced using field variables restricted to the ternary alphabet ${-1,0,+1}$. The integration is carried out by a state accumulator, while quantisation is done by a second-order noise-shaped encoder with a separate error register. The Courant number $S$ plays two roles: it is the exact fixed-point ratio and also sets the encoder's oversampling ratio. When $S$ is chosen as a power of two, each cell update requires neither run-time multiplication nor floating-point arithmetic, and each emitted field symbol is represented by just two bits. The ternary scheme converges asymptotically to the standard Yee scheme as $S$ decreases towards zero. I report wall-clock and instruction counts relative to a floating-point reference, long-time energy integrations over $2\times10^{5}$ steps and the $S$ required to achieve a prescribed accuracy for the driven mode. Extending the approach to acoustics, Virieux-type elastodynamics and Schrodinger-equation solvers is a prospective direction towards a broader class of quantised physics solvers for resource-constrained and specialised hardware.
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Applied Physics · Cross-listed from cond-mat.mes-hall

Magnon-induced phononic Chern insulator

Rui-Chang Shen, Yihao Yang and Haoran Xue

High-frequency artificial phononic crystals offer a low-loss platform compatible with on-chip integration, yet realizing Chern phononic phases at GHz frequencies remains challenging. Here, we propose a magnon-induced phononic Chern insulator in a honeycomb phononic crystal hybridized with ferromagnetic islands at the hexagon centers. A circularly polarized Kittel mode couples to the surrounding phonons with a phase winding, which breaks time-reversal symmetry and opens a full Chern gap. In the large-detuning regime, this mechanism leads to an effective Haldane-type phononic model with magnon-induced complex hopping. By tuning the magnon-phonon interaction, the full hybrid system accesses Chern phases with tunable Chern numbers |C|=1 and |C|=2. The predicted gaps can exceed realistic phonon and magnon linewidths, enabling their observation in GHz acoustic devices. Our work establishes chiral magnon–phonon hybridization as a route to magnetically reconfigurable topological phononics.
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Applied Physics · Cross-listed from quant-ph

Isotropic Nanoscale Quantum Sensor at Room-Temperature

Daniel T. Möller, Baha Sakar, Ekrem T. Güldeste et al. (+9 more)

Color-center based quantum sensors provide nanoscale resolution under ambient conditions, yet their applicability remains limited. Because the quantization axes are locked to the host lattice, conventional color centers suffer severe signal loss in off-axis magnetic fields. To address this, we report an isotropic magnetometer enabled by the neutrally charged nitrogen-vacancy center (NV0) in diamond. Here, spin-to-charge dynamics yield an NV0-dark spin pair whose quantization axis dynamically aligns with the external field. Read out through NV charge-state-selective fluorescence, this system exhibits microsecond room-temperature coherence and nanotesla sensitivity for arbitrary field directions. We demonstrate alignment-free mapping of steep field gradients and single paramagnetic micro-targets, alongside isotropic readout from randomly oriented nanodiamonds. Resolving longstanding orientation constraints, this platform unlocks unrestricted nanoscale magnetometry across life sciences and quantum materials.
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All authors Daniel T. Möller, Baha Sakar, Ekrem T. Güldeste, Dhruv Wadhwani, Olt Gashi, Daniel A. García Vaca, Mokessh K. Ciwan, Simone P. Crozier, Christian Laube, Sirswa K. Shree Ram, Matteo Slaviero, Nabeel Aslam

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

The Effect of Geometry on Thermodynamic Response

Bojana Bokic, Sébastien R. Mouchet, Biljana Stankov et al. (+9 more)

At the nano- and microscale, various patterns influence and shape thermal and optical response, making them essential for the survival of various biological species. In addition, controlling thermal radiation is vital for a broad range of applications, such as thermal management, spectroscopy, optoelectronics, and energy conversion technologies. For this reason, there is strong pressure to elucidate the physics of thermal radiation at the nanoscale. In this article, we provide evidence that complex nanoscale geometries affect thermal management, leading to an unusual thermal response in heat-capacity measurements as a function of temperature. Beyond identifying the structural constraints associated with this unusual thermodynamic response, the current study introduces the possibility of shaping the apparent heat-capacity response through geometry without necessarily altering the system's chemistry.
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All authors Bojana Bokic, Sébastien R. Mouchet, Biljana Stankov, Sanja Ostojic, Nicolas Roy, Darko Vasiljevic, Yin Chang, Marija Radmilovic-Radjenovic, Branislav Radjenovic, Thierry Verbiest, Mohamed Hatifi, Branko Kolaric