Applied Physics
Hierarchical resonators for localized charging in room-scale magnetoquasistatic wireless power systems
Takuya Sasatani, Alanson P. Sample and Yoshihiro Kawahara
Magnetoquasistatic wireless power transfer can deliver substantial power to mobile devices over near-field links. Room-scale implementations, such as quasistatic cavity resonators, extend this capability over large enclosed volumes, but their efficiency drops sharply for centimeter-scale or misoriented receivers because the
magnetic field is spatially broad and weakly coupled to small coils. Here, we introduce hierarchical resonators that act as selectively activated relays within a room-scale quasistatic cavity resonator, coupling to the ambient
magnetic field and re-emitting a stronger local field near a target receiver. This architecture enables localized power delivery to miniature devices without requiring global reshaping of the room-scale cavity mode. Experimentally, the hierarchical link improves power transfer efficiency by more than two orders of magnitude relative to direct room-scale transfer and delivers up to 500 mW of DC power to a 15 mm receiver. We further demonstrate selective multi-relay operation and field reorientation for furniture-embedded charging scenarios. These results establish a scalable route to reconfigurable wireless power delivery for miniature and batteryless devices in room-scale environments.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Current-tunable room temperature ferromagnetism and current-driven phase transitions
Jianping Guo, Peng Rao, Xinhao Huang et al. (+9 more)
It is generally assumed that the application of a charge-current in
ferromagnetic metals suppresses their
ferromagnetic order through trivial Joule heating. Here, we demonstrate that a charge current can instead enhance
magnetic ordering. Using a WTe2/Fe3Ge2Te (FGT) stack as a model system, we show that a charge current flowing in WTe2 controls the
ferromagnetic properties and
magnetic phase transition of the adjacent FGT via a current-induced effective
magnetic-field arising from orbital magnetization. Remarkably, the charge current drives a substantial enhancement of the Curie temperature, boosting it well above room temperature. Furthermore, we show that the charge-current enables controlled tuning of the phase transitions in FGT, which confirms the scaling behaviour of a ferromagnet-paramagnet phase transition. This work provides a pathway for integrating two-dimensional ferromagnets into spintronic functionalities at technologically relevant temperatures and for exploring novel current-driven phenomena in
ferromagnetic systems.
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All authors Jianping Guo, Peng Rao, Xinhao Huang, Tailai Xu, Yuxuan Guo, Jian Shao, Cheng Sun, Anton Orekhov, Thomas N. G. Meier, Johannes Knolle, Christian H. Back, Lin Chen
Atmospheric and Oceanic Physics
StretchCast: Global-Regional AI Weather Forecasting on Stretched Cubed-Sphere Mesh
Jin Feng
Global AI weather
forecasting still relies mainly on uniform-resolution models, making it hard to combine regional refinement, two-way regional-global coupling, and affordable training cost. We introduce StretchCast, a global-regional AI
forecasting framework built on a variable-resolution stretched cubed-sphere (SCS) mesh that preserves a closed global domain while concentrating resolution over a target region. Within this framework, we develop a one-step predictor, SCS_Base Model, and a rollout-oriented multistep predictor, SCS_FCST4 Model, to test the feasibility of SCS-based
forecasting and the benefit of joint multistep training. Experiments use ERA5 with 69 variables over 1998-2022. Because training compute remains limited, this study uses a coarse-resolution proof-of-concept configuration rather than a final high-resolution system. Even with only about 7,776 effective global grid
cells and roughly 0.875 degree resolution over the center-refined face, the 23M-parameter SCS_Base Model yields stable multivariate forecasts. With 83M parameters and training cost on the order of hours, SCS_FCST4 Model delivers competitive medium-range anomaly-correlation
evolution over the target region after unified reprojection, especially for geopotential height, specific humidity, and part of the lower-tropospheric winds, while maintaining smooth cross-face continuity and realistic multiscale structure in typhoon and spectral analyses. These results support StretchCast as a practical lightweight foundation for global-regional AI weather
forecasting.
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Fluid Dynamics · Cross-listed from cond-mat.soft
Surfactant reorientation under shear: dynamic surface tension and droplet deformation
Alexandra J. Hardy, Abdallah Daddi-Moussa-Ider and Elsen Tjhung
Surfactants are amphiphilic molecules that are generally anisotropic rather than spherical. Their orientation is therefore governed by the interplay between shear-induced reorientation, thermal rotational
diffusion, and energetic
alignment with the interface. The relative importance of these processes is characterized by the rotational Peclet number, $Pe_r$. We show that this microscopic coupling between flow and surfactant orientation can give rise to new macroscopic interfacial phenomena, including a shear-dependent effective surface tension and non-trivial droplet deformation. To investigate this mechanism, we develop a phase-field model that incorporates both the surfactant concentration and its local average orientation (polarization field). Using perturbation theory, we derive an analytical expression for the effective surface tension, which depends not only on the surfactant concentration but also on the local shear rate. We then employ a hybrid numerical method to study the deformation of a surfactant-covered droplet under imposed shear flow. For small $Pe_r$, droplet deformation can be accurately captured by a modified Taylor and Maffettone-Minale theories. For large $Pe_r$, shear-induced reorientation strongly distorts the surfactant polarization, and the droplet deformation progressively approaches that of a pure (surfactant-free) droplet.
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Plasma Physics
Optimization of Laser Irradiation Uniformity for the Double-Cone Ignition Scheme with MULTI-3D simulations
Yicheng Wang, Yiwen Yang, Fuyuan Wu et al. (+3 more)
The double-cone ignition (DCI) scheme holds a promising perspective for
laser driven fusion energy and astrophysics. However, optimizing the
laser irradiation uniformity under the constraints of limited
laser beams and a given cone angle remains to be explored. We utilized the three-dimensional radiation hydrodynamics program MULTI-3D to simulate the interaction process between the
laser and
plasma shell. By employing
Bayesian optimization for the pointing position of the incident
laser beams, we achieved a
laser irradiation scheme with nonuniformity less than 5%. This study can provide references for experiments and offer valuable insights for other
laser fusion schemes.
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All authors Yicheng Wang, Yiwen Yang, Fuyuan Wu, Yuhan Wang, Rafael Ramis, Jie Zhang
Optics
Frozen Surface Modes on a Moving Interface
S. Azar, M. J. Bhaseen, A. V. Zayats et al. (+1 more)
Spatio-temporal modulation enables synthetic motion at effective velocities approaching the speed of light, providing new regimes for light-matter interaction. Traditional Cherenkov-type effects arise when the velocity of an emitter matches or exceeds the phase velocity of electromagnetic modes supported by a medium. Here, we study dispersive systems in which phase and group velocities differ markedly. Specifically, we explore the case of group-velocity matching for surface waves, where the emitter moves at the same velocity as the flow of energy. This gives rise to frozen surface modes which are stationary in the emitter frame, accompanied by resonant energy accumulation. The result is a dramatic increase of the local density of optical states, the power extracted from the emitter, and the optomechanical forces and torques it experiences. Since surface modes naturally exhibit slow group velocities, this is accessible at lower relative speeds than phase-velocity effects. This phenomenon provides a route to enhanced light-matter interaction via real or synthetic motion.
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All authors S. Azar, M. J. Bhaseen, A. V. Zayats, F. J. Rodríguez-Fortuño
Fluid Dynamics · Cross-listed from cond-mat.soft
Penetration of Rigid Rods, Flexible Rods, and Granular Jets into Low-Density Granular Media
J.E. Benítez-Zamudio, S. Hidalgo-Caballero and F. Pacheco-Vázquez
The penetration of projectiles into granular materials has been mainly studied using spherical intruders. Here we explore the dynamics of rods penetrating vertically in a two-dimensional granular bed composed of expanded polystyrene spheres. The experiments were performed using rigid rods, flexible rods and vertical arrays of non-cohesive particles, and the dynamics for the three cases was compared. In contrast to the vertical penetration observed for a single spherical projectile, high speed
videos reveal that a rod rapidly deviates from its initial vertical direction due to inhomogeneities of the bed packing fraction. Then, the rod rotates due to the torque induced by the resistance force and follows a curved trajectory until be aligned horizontally at a final depth. A short rod tends to deviate faster than a longer rod due to the smaller moment of inertia. Moreover, long flexible rods always lose their vertical
alignment and experience buckling, whereas rigid rods of the same size penetrate deeper before being deviated. On the other hand, experiments and molecular dynamics simulations show that a initially vertical array of grains also loses its verticality and stops adopting a final horizontal configuration. The granular array penetrates considerably less than the rods of equivalent mass, and the stopping mechanism is based on vertical-to-horizontal momentum transfer during a collisional process of the constituting particles.
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Optics
Fine Structures of Berry Curvature and Unquantized Valley Chern Numbers in Valley Photonic Crystals
Wei Dai, Taiki Yoda, Yuto Moritake et al. (+1 more)
Valley photonics has emerged as a promising platform in topological photonic systems, yet the topological nature of valley-dependent phenomena remains unsettled. Theoretically, inter-valley scattering may occur with structural imperfections, and global Chern numbers vanish due to time-reversal
symmetry. As a result, valley-dependent
topology is locally defined around K(K') points in the half-Brillouin zone (HBZ). While half-integer valley Chern numbers have been widely assumed, their quantization and topological validity remain controversial. Here, we systematically investigate a continuous spectrum of valley photonic
crystal designs by evaluating their Berry
curvatures, valley Chern numbers, and angular momenta. We show that valley Chern numbers are generically unquan-tized and instead form a continuous spectrum varying with structural parameters. We further reveal previously unexplored fine structures in the Berry
curvature distribution in momentum space. The unquantized valley Chern numbers are attributed to inter- and intra-valley cancellation of Berry
curvature, highlighting the absence of a protecting mechanism for quantization. Our results call for a reassessment of valley-dependent
topology and provide a more rigorous framework for interpreting valley-related photonic phenomena.
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All authors Wei Dai, Taiki Yoda, Yuto Moritake, Masaya Notomi
Physics Education
Roller coaster dynamics – from point particles to a continuum model using Lagrange density
Michael Kaschke and Holger Cartarius
Analyzing the motion of a roller coaster allows for an instructive introduction of various theoretical concepts in a concrete and enjoyable context. We start by modeling the roller coaster train as a point particle. We then develop more realistic models for the train and finally we show how to introduce a continuum limit in a simple way. These studies instructively illustrate the relationships between different formalisms (Newtonian mechanics, Lagrangian mechanics of the first and second kind, as well as continuous Lagrangian mechanics using a Lagrangian density). We derive the equations of motion in all considered models and calculate the forces acting on the track and on the passengers. Numerical results are also provided and discussed.
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Fluid Dynamics
Reconfigurable kirigami mesostructure enables modulation of lift and drag
Agathe Schmider, Tom Marzin and Sophie Ramananarivo
Flexible surfaces can modulate fluid forces through deformation, enabling passive adaptation to flow conditions. Here we show that kirigami sheets, planar surfaces patterned with arrays of parallel slits, provide a simple route to tunable aerodynamics by transforming into three-dimensional porous meso-architectures that can be reversibly reconfigured in flow. When exposed to crossflow, parallel-cut kirigami buckle out of plane to form a
lattice of inclined plate-like elements. Experiments reveal that this architecture generates not only drag but also a substantial transverse lift force, even when the sheet is held perpendicular to the incoming flow. Because the mesostructure can switch between distinct states, a single sheet produces large and selective variations in drag and lift under identical flow conditions, in some cases partially decoupling these forces. The evolving mesostructure also alters the scaling of forces with flow speed, influencing both instantaneous loads and their velocity dependence. Force measurements collapse when expressed in terms of the Cauchy number, identifying stiffness, set by the cutting pattern, as the dominant control parameter, a relationship captured by a continuum elastic model. These results show how kirigami architectures encode aerodynamic functionality and behavior directly through their structure, providing a scalable platform for surfaces with reprogrammable fluid forces.
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Optics
Observation of topological vortex solitons on disclinations
A.V. Kireev, K. Sabour, V.O. Kompanets et al. (+13 more)
Vortex-carrying wave fields play a crucial role in photonics due to unusual propagation properties and interactions with matter, which enable numerous practical applications ranging from optical tweezers and imaging to information encoding and transmission. Localized
vortex-carrying beams propagating in nonlinear optical media may form self-sustained excited states-
vortex solitons-which are, however, usually prone to instabilities and require high powers for their stabilization in non-topological materials. Using fs-
laser written aperiodic waveguide arrays, we demonstrate that photonic topological
insulators with disclinations admit the formation of stable and thresholdless
vortex solitons with tunable shapes. These unique materials belong to a class of higher-order topological
insulators and allow the propagation of localized, topologically protected excitations at the disclination core, enabling disorder-resistant transmission of signals and energy. We show that
vortex solitons bifurcate from the superposition of topologically protected linear edge states at the disclination core and remain stable in the entire forbidden topological gap. Realized topological
vortex solitons with
symmetries that are inaccessible in periodic
lattices are the first example of excited
soliton states with non-trivial phase structure in a topological
insulator. Our findings shine a light on the interplay between nonlinearity, the angular momentum degree of freedom of light, and the material
topology.
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All authors A.V. Kireev, K. Sabour, V.O. Kompanets, S.Y. Alyatkin, N.S. Kostyuchenko, S.A. Zhuravitskii, N.N. Skryabin, I.V. Dyakonov, A.A. Kalinkin, K.A. Sitnik, S.K. Ivanov, S.P. Kulik, S.V. Chekalin, P.G. Lagoudakis, V.N. Zadkov, Y.V. Kartashov
Instrumentation and Detectors
Integration and characterization of Readout Electronics System for dN/dx Measurement with Drift Chamber Prototype
Dongcheng Cai, Qicai Li, Mingyi Dong et al. (+10 more)
To explore the feasibility of high-precision particle identification using the cluster counting technique for the drift chamber, a dedicated readout electronics system with low noise, high bandwidth, and high sampling rate is required. This paper presents the design and performance evaluation of a scalable readout prototype developed for this application. The system architecture integrates a custom front-end with a $1.3\ \text{GSps}$ waveform sampling backend, implemented within a modular 120-channel framework. Laboratory characterization of the 40-channel prototype demonstrates a $-3$ dB analog bandwidth of $460\ \text{MHz}$ and an Equivalent Noise Input current of $0.81\ \mu\text{A}_\text{rms}$. These specifications are essential for preserving the fast temporal features of ionization signals. Furthermore, the system achieves an intrinsic timing jitter of $0.87\ \text{ns}$, which satisfies the timing precision requirements for drift distance measurement. Joint experiments with a drift chamber prototype using
cosmic rays verified the system's capability to resolve discrete ionization peaks within piled-up waveforms. These results confirm that the readout electronics provide the signal fidelity and temporal resolution necessary for future cluster counting
algorithm development.
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All authors Dongcheng Cai, Qicai Li, Mingyi Dong, Weile Gong, Mengyang Ji, Hongbin Liu, Wenyu Pan, Linghui Wu, Dewei Xu, Yimie Yuan, Hongyu Zhang, Guang Zhao, Yubin Zhao
Computational Physics
Temperature dependence of the dynamic structure factor of the electron liquid via analytic continuation
Thomas Chuna, Maximilian P. Böhme and Tobias Dornheim
We present new analytic continuation results for the dynamic structure factor $S(\mathbf{q},\omega)$ of the uniform electron
liquid based on quasi-exact ab initio path integral Monte Carlo (PIMC) data for the imaginary-time density–density correlation function $F(\mathbf{q},\tau)$ across a broad range of temperatures. For this purpose, we employ both a traditional maximum
entropy method solver, and a pre-optimized sparse Gaussian kernel representation as it has been implemented in the recent PyLIT package [Benedix Robles et al., Comp.~Phys.~Comm.~319, 109904 (2026)], and we identify potential advantages and disadvantages in both. We expect our results to be interesting for a broad range of topics, including the interpretation of x-ray Thomson scattering experiments with extreme states of matter and the construction of improved exchange–correlation kernels for linear-response time-dependent density functional theory.
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Optics
Super-pupil beam engineering for enhanced confinement of azimuthally polarized depletion beams
Costanza Agazzi, Nick Toledo-García, Estela Martín-Badosa et al. (+5 more)
Fluorescence depletion microscopy techniques require optical fields with a well-defined and spatially confined central intensity minimum to achieve sub-diffraction lateral resolution. Here, we present the design and experimental implementation of an azimuthally polarized, doughnut-shaped depletion beam based on super-pupil engineering principles. By tailoring the radial amplitude distribution at the entrance pupil to approximate a Bessel-type target function, the resulting focal field exhibits a tighter central doughnut compared to conventional circularly or azimuthally polarized beams. The designed pupil field distribution is implemented using a phase-only spatial light modulator operated in a double-pass configuration, enabling independent modulation of orthogonal polarization components via complex-field
holographic encoding. Analytical modeling of the designed field predicts an estimated resolution gain of approximately 24% and a reduction in required depletion power of approximately 42% relative to a canonical circularly polarized Laguerre-Gaussian beam. Although the engineered field exhibits pronounced sidelobes, these do not preclude its use as a depletion beam, since lateral resolution is strongly influenced by the spatial confinement and effective suppression of the central intensity minimum for a given depletion intensity.
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All authors Costanza Agazzi, Nick Toledo-García, Estela Martín-Badosa, Mario Montes-Usategui, David Maluenda, Jordi Tiana-Alsina, Rosario Martínez-Herrero, Artur Carnicer
Optics
Extreme Linewidth Narrowing in Diamond Raman Lasers Enables the Generation of 35 W at 589 nm with Hz-Scale Intrinsic Linewidth
Osama Terra, Adam Sharp, Aidan Connaughton et al. (+5 more)
High-power
lasers with narrow linewidth and high beam quality in the visible spectrum are essential for emerging
quantum and space technologies. Here we report significant advances in diamond Raman
lasers, generating diffraction-limited yellow light at 589 nm with output power up to 35 W and enhanced single-frequency stability. The optical-to-optical efficiency from the pump reaches 47.7%, representing a record efficiency for this class of devices. More importantly, the extreme linewidth-narrowing of Raman lasing in diamond enables a reduction in frequency noise exceeding six orders of magnitude, resulting in a measurement-limited intrinsic linewidth of 6 Hz at the maximum power. The
laser is further stabilized to the sodium D2a saturation-absorption transition, making it well-suited for sodium-based space and
quantum experiments. These results represent a major step toward continuous-wave, high-power, single-frequency
laser sources across the visible spectrum that combine ultranarrow linewidth, high efficiency, and near-diffraction-limited beam quality for advanced
quantum and space applications.
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All authors Osama Terra, Adam Sharp, Aidan Connaughton, Mark Ferrier, Jipeng Lin, Tiago A. Ortega, David J. Spence, Richard P. Mildren
Plasma Physics
Tearing and Kelvin-Helmholtz dynamics in fully kinetic particle-in-cell simulations of electron-scale current sheets
Sushmita A. Mishra and Gurudatt Gaur
We investigate the stability and nonlinear
evolution of localized electron-scale current sheets using fully kinetic, electromagnetic particle-in-
cell (PIC) simulations in two and three dimensions. By varying the current-sheet thickness, we examine how it influences the dominant instability and subsequent nonlinear dynamics. In two dimensions, the
evolution is governed by electron inertial tearing, with growth rates in good agreement with linear electron magnetohydrodynamics (EMHD) predictions. In three dimensions, however, a thickness-dependent transition emerges. For wider current sheets, a velocity-shear-driven Kelvin-Helmholtz-type instability dominates the early and intermediate
evolution, leading to
vortex formation and strong modulation of the current layer, followed by the re-emergence of tearing at later times. In contrast, thinner sheets remain tearing-dominated throughout, with no transition to a shear-driven regime, although their effective growth rate is reduced relative to linear predictions, suggesting the influence of mode coupling and three-dimensional effects. These results establish a thickness-dependent transition from tearing-dominated to shear-driven dynamics and reveal a nonlinear sequence of instability
evolution in fully kinetic systems, providing new insight into the competition between
curvature-driven and shear-driven instabilities in electron-scale current sheets.
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Applied Physics
Hot LO Phonon-Induced RF Nonlinearity in GaN High-Electron-Mobility Transistors
Ankan Ghosh Dastider, Matt Grupen, Nicholas C. Miller et al. (+1 more)
Hot longitudinal optical (LO)
phonons in GaN have recently been identified as a major factor degrading the DC performance of GaN high-electron-mobility transistors (HEMTs) by 30-60%, despite their ultrafast decay. However, their impact on large-signal RF performance, particularly RF linearity, remains poorly understood. Using full-band transport simulations of a fabricated GaN HEMT, we show that even ultrafast LO
phonons with a lifetime of 30 fs degrade the output 1-dB compression point and the third-order output intercept power by ~3 dB compared to the case without LO
phonon heating. Furthermore, our analysis reveals that improvements in transconductance ($g_\textrm{m}$) flatness do not necessarily translate into improved RF linearity because multiple nonlinear mechanisms contribute to the transistor response, and their combined effect cannot be captured by $g_\mathrm{m}$ flatness alone. This work clarifies a persistent ambiguity in the literature regarding using $g_\mathrm{m}$ flatness as a proxy for RF linearity and establishes intrinsic
phonon-induced limits on the RF performance of GaN HEMTs.
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All authors Ankan Ghosh Dastider, Matt Grupen, Nicholas C. Miller, Shaloo Rakheja
Medical Physics
Extending Regression Without Truth to Integrate Ground-Truth Measurements for Evaluating Quantitative Imaging Methods with Patient Data
Yan Liu and Abhinav K. Jha
Objective evaluation of quantitative imaging (QI) methods with patient data is often hindered by the lack of gold standards. To address this challenge, a class of regression-without-truth (RWT) techniques have been developed. These techniques assume that the true and measured values are linearly related and estimate the linear-relationship parameters without access to true values. However, reliable estimation of these parameters typically requires many patient samples, which can be expensive and time consuming to obtain, and even impossible in settings such as studies with rare diseases or with new clinical imaging procedures. Thus, there is an important need for strategies to perform evaluation of quantitative imaging methods with a small number of patient samples. In this context, we note that
datasets with known ground truth, such as physical phantom studies, could be available. In this manuscript, we propose an approach that integrates information from both patient data without ground truth and known-ground-truth
datasets to perform objective evaluation of QI methods. We validated the proposed approach using numerical studies, which showed that the proposed approach yielded improved performance in ranking QI methods compared with RWT technique. The results demonstrate the potential of the proposed approach for evaluating QI methods when patient data are limited and motivate further validation with clinically realistic simulation studies and clinical data.
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Medical Physics
Comparing evaluation of quantitative imaging methods using reference standards vs. regression-without-truth-based technique
Yan Liu and Abhinav K. Jha
Clinical translation of quantitative imaging (QI) methods requires objective evaluation of these methods on reliably measuring the underlying true quantitative values. Ideally, such evaluation would be performed using ground truth or gold standards. However, in clinical practice, ground truth is generally unavailable, and obtaining gold standards for large patient cohorts is often impractical or infeasible. In these scenarios, evaluation using well-accepted or commonly used methods for measuring the quantitative values that may have bias and/or measurement error, referred to as reference standards, is a common alternative. However, the error in reference standards might lead to inaccurate results in evaluating the QI methods. To address the challenge of evaluation without a gold standard, a class of regression-without-truth (RWT)-based techniques has also been proposed. These techniques compare QI methods without requiring ground truth and have demonstrated promise across multiple applications. This raises an important question: how does evaluation using reference standards vs. RWT-based techniques compare? Our work, which investigates this question using controlled numerical experiments, showed that when the measurement error of the reference standard exceeded a certain level, evaluation with a RWT-based technique outperformed evaluation with reference standards. This study provides insights for selecting appropriate evaluation strategies when gold standards are unavailable and motivates further investigation in clinically realistic settings.
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Instrumentation and Detectors
Time Resolution of a Novel Ultra-fast Graphene-Optimized 4H-SiC PIN
Suyu Xiao, Hui Liang, Congcong Wang et al. (+2 more)
Silicon carbide detectors exhibit good detection performance such as fast time resolution, high radiation tolerances, high breakdown voltage and low temperature sensitivity and have been studied for detection applications. Meanwhile, transient current technique (TCT) is a direct and effective method to evaluate the time resolution of
semiconductor detectors. Conventional metal electrodes for TCT testing employ window structures, which lead to non-uniform electric field distribution and deteriorated time resolution.
Graphene features high optical transmittance, ultrahigh carrier mobility, and excellent radiation resistance, making it an ideal transparent electrode material for
semiconductor detectors. In this work, a
graphene-optimized ring electrode (G/RE) 4H-SiC PIN detector and a reference ring electrode (RE) 4H-SiC PIN detector are fabricated. TCT measurements demonstrate that
graphene integration improves the time resolution consistency, reducing the time resolution from 38 ps (reference RE detector) to 21 ps (G/RE detector) at the maximum scanning distance, while also achieving effective noise suppression. The
graphene integration improves the stability of time resolution by 87% compared to the reference detector. Notably, the achieved time resolution of 21 ps is comparable to that of state-of-the-art 4H-SiC low-gain avalanche detectors (LGADs), which typically exhibit time resolutions better than 35 ps under single minimum ionizing particle (MIP) equivalent injection conditions, further validating the effectiveness of
graphene-based electrode design.
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All authors Suyu Xiao, Hui Liang, Congcong Wang, Zhenyu Jiang, Lin Zhu
Chemical Physics
ADEPT-PolyGraphMT: Automated Molecular Simulation and Multi-Task Multi-Fidelity Machine Learning for Polymer Property Generation and Prediction
Sobin Alosious, Yuhan Liu, Jiaxin Xu et al. (+4 more)
The discovery of
polymers with targeted properties is challenged by the vast chemical design space and the limited availability of consistent, high-quality data across multiple properties. In this work, an integrated
polymer informatics framework is presented that combines the Automated molecular Dynamics Engine for
Polymer simulaTions (ADEPT) workflow with multi-task and multi-fidelity machine learning (PolyGraphMT).
Polymer repeat units are represented as molecular graphs and processed using a graph neural network to learn structure-property relationships. Starting from SMILES representations for monomers, ADEPT automates the construction of atomistic models and the evaluation of their properties using molecular dynamics simulations and density functional theory calculations. The simulation data are combined with curated experimental data and group contribution theory estimates to construct a unified
dataset of approximately 62,000
polymer property values spanning 28 properties. Using this
dataset, inter-property correlations are analyzed, and multi-task learning strategies are evaluated for joint property prediction. The results show that multi-task models achieve performance comparable to single-task models in data-rich regimes and exhibit superior accuracy as training data become limited. In addition, fidelity-aware training improves predictive accuracy when combining experimental and computational data sources. The trained models are further applied to large-scale property prediction for
polymers in the PolyInfo database and the PI1M virtual
polymer library, producing physically consistent property distributions across a broad chemical space. Overall, the proposed framework provides a structured approach for scalable prediction and screening of
polymer properties across multiple property types and data fidelity levels.
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All authors Sobin Alosious, Yuhan Liu, Jiaxin Xu, Gang Liu, Renzheng Zhang, Meng Jiang, Tengfei Luo
Chemical Physics
A theoretical and experimental assessment of adiabatic losses in force-gradient-detected magnetic resonance of nitroxide spin labels
Michael C. Boucher, Peter Sun, Eric W. Moore et al. (+1 more)
We recently introduced a new theoretical description of Landau–Zener–Stückelberg–Majorana (LZSM) transitions that accounts for both adiabatic and
spin-dephasing losses during sweeps through resonance. Here, we use this new description to assess signal loss due to cantilever tip motion in
magnetic resonance force microscopy experiments on electron
spins. We derive equations for
spin-induced cantilever frequency shifts that account for the time-dependent magnetization present during cantilever-synchronized periods of irradiation and relaxation. We show that a frequency shift can be created by either a force- or force-gradient coupling mechanism, depending on the periodicity and timing of the microwave irradiation; the frequency shift decreases when the
spin-
lattice relaxation time becomes shorter than the cantilever oscillation period. Equations were validated by comparing with the magnetization computed by numerically integrating the time-dependent Bloch equations. Numerical simulations incorporating the new equations were compared to frequency-shift electron-
spin signals collected as a function of
magnetic field, tip-sample separation, microwave power, and microwave timing. The simulations quantitatively describe the observed signals with essentially no free parameters. Finally, motivated by our new frequency-shift equations, we present a new experimental
spin-excitation protocol that eliminates spurious signals arising from direct microwave excitation of the cantilever in a
magnetic resonance force microscope experiment.
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All authors Michael C. Boucher, Peter Sun, Eric W. Moore, John A. Marohn