Computational Physics · Cross-listed from cond-mat.mtrl-sci
Rare-Earth Engineering of NaAlO3 Perovskites Unlocks Unified Optoelectronic, Thermoelectric, and Spintronic Functionalities
Muhammad Imran, Sikander Azam, Qaiser Rafiq et al. (+1 more)
Perovskite
oxides are promising for energy and
quantum technologies, but wide-gap hosts such as NaAlO3 suffer from deep-UV absorption and limited carrier transport. Using first-principles GGA+U+SOC calculations, we investigate Eu3+-, Gd3+-, and Tb3+-doped NaAlO3 and evaluate their electronic, optical, elastic, and thermoelectric properties. Rare-earth substitution is thermodynamically favorable (formation energies 1.2-1.6 eV) and induces strong f-p hybridization, reducing the pristine band gap (about 6.2 eV) to about 3.1 eV for Tb.
Spin-resolved band structures reveal Gd-driven half-
metallicity, Eu-induced
spin-selective
metallicity, and Tb-stabilized p-type semiconducting behavior. The optical spectra show a red-shifted absorption edge (about 2.0-2.2 eV), a large static dielectric response (epsilon1(0) about 95 for Eu), and plasmonic resonances near 4 eV, enabling visible-light harvesting. Elastic analysis indicates mild
lattice softening with preserved ductility (Pugh ratio B/G about 1.56-1.57). Thermoelectric performance is enhanced, with Seebeck coefficients greater than 210 uV/K for Eu and Tb and ZT about 0.45 at 500 K. These results identify rare-earth-doped NaAlO3 as a multifunctional perovskite platform for photovoltaics, photocatalysis, thermoelectrics, and spintronics.
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All authors Muhammad Imran, Sikander Azam, Qaiser Rafiq, Amin Ur Rahman
Atmospheric and Oceanic Physics
Beyond the Training Data: Confidence-Guided Mixing of Parameterizations in a Hybrid AI-Climate Model
Helge Heuer, Tom Beucler, Mierk Schwabe et al. (+3 more)
Persistent systematic errors in Earth system models (ESMs) arise from difficulties in representing the full diversity of subgrid, multiscale atmospheric convection and
turbulence. Machine learning (ML) parameterizations trained on short high-resolution simulations show strong potential to reduce these errors. However, stable long-term atmospheric simulations with hybrid (physics + ML) ESMs remain difficult, as neural networks (NNs) trained offline often destabilize online runs. Training convection parameterizations directly on coarse-grained data is challenging, notably because scales cannot be cleanly separated. This issue is mitigated using data from superparameterized simulations, which provide clearer scale separation. Yet, transferring a parameterization from one ESM to another remains difficult due to distribution shifts that induce large inference errors. Here, we present a proof-of-concept where a ClimSim-trained, physics-informed NN convection parameterization is successfully transferred to ICON-A. The scheme is (a) trained on adjusted ClimSim data with subtracted radiative tendencies, and (b) integrated into ICON-A. The NN parameterization predicts its own error, enabling mixing with a conventional convection scheme when confidence is low, thus making the hybrid AI-physics model tunable with respect to observations and reanalysis through mixing parameters. This improves process understanding by constraining convective tendencies across column water vapor, lower-tropospheric stability, and geographical conditions, yielding interpretable regime behavior. In AMIP-style setups, several hybrid configurations outperform the default convection scheme (e.g., improved precipitation statistics). With additive input noise during training, both hybrid and pure-ML schemes lead to stable simulations and remain physically consistent for at least 20 years.
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All authors Helge Heuer, Tom Beucler, Mierk Schwabe, Julien Savre, Manuel Schlund, Veronika Eyring
Optics
Enhanced Optical Kerr Effect in Metasurfaces Featuring Arrays of Rotated Rectangular Holes via Trapped-Mode Resonances
Andrey V. Panov
Recent advances in nanophotonics have demonstrated that various optical resonances in nanostructures can achieve strong field confinement with substantially suppressed scattering. This study investigates the optical Kerr effect (OKE) enhancement in high-refractive-index metasurfaces featuring non-BIC trapped-mode resonances, using gallium phosphide (GaP) as a model material. Three-dimensional finite-difference time-domain simulations reveal a significant enhancement of the effective second-order refractive index, reaching values up to 700 times greater than bulk GaP. The numerical results show strong electromagnetic field localization at the trapped-mode resonance, characterized by a wide transmittance dip (low Q-factor) and near-unity reflectance. Remarkable stability is observed, with the OKE enhancement maintaining less than 5% variation for moderate polarization angles and tolerating random nanohole rotations that model fabrication imperfections. Compared to bound states in the continuum (BIC), the non-BIC trapped mode demonstrates superior robustness to structural disorder while achieving comparable nonlinear enhancement. These findings suggest promising applications in reflective nonlinear optics, particularly for high harmonic generation and polarization-insensitive photonic devices.
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Biological Physics
Confinement reduces surface accumulation of swimming bacteria
Da Wei, Shiyuan Hu, Tangmiao Tang et al. (+3 more)
Many swimming bacteria naturally inhabit confined environments, yet how confinement influences their swimming behaviors remains unclear. Here, we combine experiments, continuum modeling and particle-based simulations to investigate near-surface bacterial swimming in dilute suspensions under varying confinement. Confinement reduces near-surface accumulation and facilitates bacterial escape. These effects are quantitatively captured by models incorporating the force quadrupole, a higher-order hydrodynamic singularity, that generates a rotational flow reorienting bacteria away from surfaces. Under strong confinement, bacterial trajectories straighten due to the balancing torques exerted by opposing surfaces. These findings highlight the role of hydrodynamic quadrupole interactions in near-surface bacterial motility, with implications for microbial ecology, infection control, and industrial applications.
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All authors Da Wei, Shiyuan Hu, Tangmiao Tang, Yaochen Yang, Fanlong Meng, Yi Peng
Optics
Broadband, robust, and tunable beam splitter based on topological unidirectional surface magnetoplasmons
Lujun Hong, Chao Liu, Jun Wu et al. (+5 more)
Beam splitters are pivotal components in integrated microwave and photonic systems. However, conventional designs based on directional coupling or multi-mode interference often suffer from back scattering, frequency-dependent splitting ratios, and limited bandwidth. To overcome these limitations, here, we propose a new physical mechanism to achieve a broadband, robust, and tunable beam splitter by manipulating the mode coupling of the topological unidirectional surface magnetoplasmons (USMP) at the input and output waveguides. We show that the beam splitter not only exhibits strong robustness against obstacles but also achieves a broad bandwidth across nearly the entire USMP band with arbitrarily tunable and frequency-independent splitting ratios. Moreover, the operating band of the beam splitter can be actively tuned by adjusting the external
magnetic field, while its robust and broadband characteristics are retained. Our results extend the research frontier of beam splitters and may have potential applications in integrated photonic devices and modern communication systems.
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All authors Lujun Hong, Chao Liu, Jun Wu, Chaojian He, Kai Yuan, Xiaohua Deng, Song Yang, Zhen Gao
Optics
Valley polarization of graphene via the saddle point
Deepika Gill, Sangeeta Sharma, Peter Elliott et al. (+2 more)
Graphene, and other members of the monolayer Xene family, represent an ideal materials platform for "valleytronics", the control of valley localized charge excitations. The absence of a gap in these semi-metals, however, precludes valley excitation by circularly polarized light pulses, sharply circumscribing the possibility of a lightwave valleytronics in these materials. Here we show that combining a deep ultraviolet linearly polarized light pulse with a THz envelope can induce highly valley polarized states in
graphene. This dual frequency lightform operates by (i) the deep ultraviolet pulse activating a selection rule at the M saddle points and (ii) the THz pulse displacing the M point excitation to one of the low-energy K valleys. Employing both tight-binding and state-of-the-art time dependent density functional theory, we show that such a pulse results in a near perfect valley polarized excitation in
graphene, thus providing a route via the saddle point to a lightwave valleytronics in the gapless Xene family.
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All authors Deepika Gill, Sangeeta Sharma, Peter Elliott, Kay Dewhurst, Sam Shallcross
Optics · Cross-listed from cond-mat.mes-hall
Far-field radiation of bulk, edge and corner eigenmodes from a finite 2D Su-Schrieffer-Heeger plasmonic lattice
Álvaro Buendía, José Luis Pura, Vincenzo Giannini et al. (+1 more)
Subwavelength arrays of plasmonic nanoparticles allow us to control the behaviour of light at the nanoscale. Here, we develop an eigenmode analysis, employing a coupled electromagnetic dipole formalism, which permits us to isolate the contribution to the far-field radiation of each array mode. Specifically, we calculate the far-field radiation patterns by bulk, edge and corner out-of-plane eigenmodes in a finite 2D Su-Schrieffer-Heeger (SSH) array of plasmonic nanoparticles with out-of-plane dipolar resonances. The breaking of
symmetries in multipartite unit
cells is exploited to tailor the optical properties and far-field radiation of the resonant modes. We prove that the antisymmetric modes are darker and have higher Q-factors than their symmetric counterparts. Also, the out-of-plane nature of the dipolar resonances imposes that all bulk $\Gamma$-modes are dark, while corner and edge states need extra in-plane
symmetries to cancel the far-field radiation; radiation patterns in turn become more complex and concentrated along the array plane with increasing array size.
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All authors Álvaro Buendía, José Luis Pura, Vincenzo Giannini, José Antonio Sánchez Gil
Atmospheric and Oceanic Physics · Cross-listed from cs.CL
Ivan Kuznetsov, Jacopo Grassi, Dmitrii Pantiukhin et al. (+3 more)
Large
language models (LLMs) are increasingly deployed for
climate-related applications, where understanding internal climatological knowledge is crucial for reliability and misinformation risk assessment. Despite growing adoption, the capacity of LLMs to recall
climate normals from parametric knowledge remains largely uncharacterized. We investigate the capacity of contemporary LLMs to recall
climate normals without external
retrieval, focusing on a prototypical query: mean July 2-m air temperature 1991-2020 at specified locations. We construct a global grid of queries at 1{\deg} resolution land points, providing coordinates and location descriptors, and validate responses against ERA5 reanalysis. Results show that LLMs encode non-trivial
climate structure, capturing latitudinal and topographic patterns, with root-mean-square errors of 3-6 {\deg}C and biases of $\pm$1 {\deg}C. However, spatially coherent errors remain, particularly in mountains and high latitudes. Performance degrades sharply above 1500 m, where RMSE reaches 5-13 {\deg}C compared to 2-4 {\deg}C at lower elevations. We find that including geographic context (country, city, region) reduces errors by 27% on average, with larger models being most sensitive to location descriptors. While models capture the global mean magnitude of observed warming between 1950-1974 and 2000-2024, they fail to reproduce spatial patterns of temperature change, which directly relate to assessing
climate change. This limitation highlights that while LLMs may capture present-day
climate distributions, they struggle to represent the regional and local expression of long-term shifts in temperature essential for understanding
climate dynamics. Our evaluation framework provides a reproducible
benchmark for quantifying parametric
climate knowledge in LLMs and complements existing
climate communication assessments.
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All authors Ivan Kuznetsov, Jacopo Grassi, Dmitrii Pantiukhin, Boris Shapkin, Thomas Jung, Nikolay Koldunov
Medical Physics
MRI-derived quantification of hepatic vessel-to-volume ratios in chronic liver disease using a deep learning approach
Alexander Herold, Daniel Sobotka, Lucian Beer et al. (+12 more)
Background: We aimed to quantify hepatic vessel volumes across chronic liver disease stages and healthy controls using deep learning-based
magnetic resonance imaging (MRI) analysis, and assess correlations with biomarkers for liver (dys)function and fibrosis/portal hypertension. Methods: We assessed retrospectively healthy controls, non-advanced and advanced chronic liver disease (ACLD) patients using a 3D U-Net model for hepatic vessel
segmentation on portal venous phase gadoxetic acid-enhanced 3-T MRI. Total (TVVR), hepatic (HVVR), and intrahepatic portal vein-to-volume ratios (PVVR) were compared between groups and correlated with: albumin-bilirubin (ALBI) and model for end-stage liver disease-sodium (MELD-Na) score, and fibrosis/portal hypertension (Fibrosis-4 [FIB-4] score, liver stiffness measurement [LSM], hepatic venous pressure gradient [HVPG], platelet count [PLT], and spleen volume). Results: We included 197 subjects, aged 54.9 $\pm$ 13.8 years (mean $\pm$ standard deviation), 111 males (56.3%): 35 healthy controls, 44 non-ACLD, and 118 ACLD patients. TVVR and HVVR were highest in controls (3.9; 2.1), intermediate in non-ACLD (2.8; 1.7), and lowest in ACLD patients (2.3; 1.0) ($p \leq 0.001$). PVVR was reduced in both non-ACLD and ACLD patients (both 1.2) compared to controls (1.7) ($p \leq 0.001$), but showed no difference between CLD groups ($p = 0.999$). HVVR significantly correlated indirectly with FIB-4, ALBI, MELD-Na, LSM, and spleen volume ($\rho$ ranging from -0.27 to -0.40), and directly with PLT ($\rho = 0.36$). TVVR and PVVR showed similar but weaker correlations. Conclusions: Deep learning-based hepatic vessel volumetry demonstrated differences between healthy liver and chronic liver disease stages and shows correlations with established markers of disease severity.
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All authors Alexander Herold, Daniel Sobotka, Lucian Beer, Nina Bastati, Sarah Poetter-Lang, Michael Weber, Thomas Reiberger, Mattias Mandorfer, Georg Semmler, Benedikt Simbrunner, Barbara D. Wichtmann, Sami A. Ba-Ssalamah, Michael Trauner, Ahmed Ba-Ssalamah, Georg Langs
Fluid Dynamics
Effect of Stokes number on erosion on Pelton buckets for sediment-laden flows
Aron Dagur Beck and Elena Vagnoni
With increased glacial melting and the need to maintain sediment continuity for ecosystem health, sediment-laden flows through hydropower plants are becoming increasingly problematic, particularly due to erosion on runner blades and buckets. A widely used mitigation strategy is the use of filters to protect Pelton turbines. However, these filters lead to rapid sediment accumulation in reservoirs, which must be drained frequently to maintain storage capacity. The high cost of such drainage operations calls for longer intervals between them, without compromising runner integrity, as erosion-induced stress concentrations may cause bucket rupture. A better understanding of the causes of runner erosion under varying operational and sediment conditions is essential to allow more sediment to pass through the hydraulic machine safely. This study investigates how sediment-laden flow through the nozzle affects particle distribution in the jet for different Stokes numbers. Furthermore, it analyses how a realistic particle size and spatial distribution in the impacting jet compares to the assumption of a uniform particle distribution with particles of mean size when simulating bucket erosion in Pelton wheels. The results show that the particle distribution in the jet follows a similar axisymmetric shape for low Stokes numbers whereas at higher Stokes numbers it becomes asymmetric. Additionally, it is shown that imposing uniform particle distribution with particles of mean diameter under-predicts tip- and splitter erosion when simulating the erosion on the bucket but is captured by imposing the realistic size and spatial distribution.
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Data Analysis and Statistics · Cross-listed from cs.CR
Composition Law of Conjugate Observables in Random Permutation Sorting Systems
Yurang R. Kuang
We present the discovery of a fundamental composition law governing conjugate observables in the Random Permutation Sorting System (RPSS). The law links the discrete permutation count Np and the continuous elapsed time T through a functional relation connecting the characteristic function of timing distributions to the probability generating function of permutation counts. This framework enables
entropy purification, transforming microarchitectural timing fluctuations into uniform randomness via
geometric convergence. We establish convergence
theorems with explicit bounds and validate the results experimentally, achieving Shannon
entropy above 7.9998 bits per byte and chi-square uniformity across diverse platforms. The composition law provides a universal foundation for generating provably uniform randomness from general-purpose computation, securing cryptographic purity from emergent computational dynamics.
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Atomic Physics · Cross-listed from hep-ph
Atomic Observables Induced by Cosmic Fields
Sebastian Lahs, Daniel Comparat, Fiona Kirk et al. (+1 more)
The existence of
cosmic fields made from yet unknown light
bosons is predicted in many extensions to the Standard Model. They are especially of interest as possible constituents of dark matter. To detect such light and weakly interacting fields, atomic precision measurements offer one of the most sensitive platforms. In this work, we derive which atomic observables are sensitive to what kind of
cosmic field couplings. For this we consider fields that couple either through scalar, pseudoscalar, vector, axial vector, or tensor couplings. We derive the corresponding non relativistic atomic potentials. Based on their
symmetry properties, these can induce direct energy shifts or induce atomic electric dipole,
magnetic dipole, electric quadrupole as well as
nuclear Schiff and anapole moments.
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All authors Sebastian Lahs, Daniel Comparat, Fiona Kirk, Benjamin Roberts
Physics and Society · Cross-listed from cs.LG
DemandCast: Global hourly electricity demand forecasting
Kevin Steijn, Vamsi Priya Goli and Enrico Antonini
This paper presents a machine learning framework for electricity demand
forecasting across diverse geographical regions using the gradient boosting
algorithm XGBoost. The model integrates historical electricity demand and comprehensive weather and socioeconomic variables to predict normalized electricity demand profiles. To enable robust training and evaluation, we developed a large-scale
dataset spanning multiple years and countries, applying a temporal data-splitting strategy that ensures benchmarking of out-of-sample performance. Our approach delivers accurate and scalable demand forecasts, providing valuable insights for energy system planners and policymakers as they navigate the challenges of the global energy transition.
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Optics
Accurate and Noise-Robust Wavefront Reconstruction with an Optical Vortex Wavefront Sensor
Magdalena Łukowicz, Aleksandra Korzeniewska, Kamil Kalinowski et al. (+3 more)
The term wavefront sensor refers to the entire class of devices capable of measuring the optical wavefront of the incoming beam. Although numerous solutions have been proposed so far, recent advances in structured light have opened new development possibilities through controlled modification of optical field amplitude and phase. We present an alternative approach to angle-based sensing, introducing optical
vortices stable phase singularities within each subaperture of the Shack-Hartmann (S-H) architecture. Rather than changing the fundamental angle-based operating principle, it transforms the tracked quantity and its detection method. The presence of a singularity enables a dedicated tracking
algorithm that outperforms conventional methods without increasing computational complexity. We evaluated its performance against the conventional S-H across a broad SNR range (from 2 to 22), corresponding to shot noise limited to high saturation regimes, demonstrating lower mean residual phase variance across all conditions. This work demonstrates that structured beam shaping can extend the capabilities of traditional S-H architectures without requiring fundamental redesign.
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All authors Magdalena Łukowicz, Aleksandra Korzeniewska, Kamil Kalinowski, Rafał Cichowski, Rosario Porras-Aguilar, Mateusz Szatkowski
Optics
Hot-carrier generation in bimetallic Janus nanoparticles
Hanwen Jin, Chengcheng Xiao, Matias Herran et al. (+3 more)
Energetic electrons and holes generated from the decay of localized surface plasmons in metallic nanoparticles can be harnessed in nanoscale devices for photocatalysis, photovoltaics or sensing. In this work, we study the generation of such hot carriers in bimetallic Janus nanoparticles composed of Au, Ag and Cu using a recently developed atomistic modelling approach that combines a solution of the macroscopic Maxwell equation with large-scale
quantum-mechanical tight-binding models. We first analyze spherical Janus nanoparticles whose unique hot-carrier spectrum can be associated with the spectra of the two hemispheres and the interface coupling and find that under
solar illumination the Ag-Au system exhibits the highest hot-carrier generation rate. For dumbbell-shaped Janus nanoparticles, we observe a significant increase in hot-carrier generation with increasing neck size. This is caused by a dramatic enhancement of the electric field in the neck region. We also study the dependence of hot-carrier generation on the light polarization and find that the largest generation rates are obtained when the electric field is perpendicular to the interface between the two metals due to the maximal dipole coupling with the electric field. The insights from our study will guide the experimental design of efficient hot-carrier devices based on bimetallic Janus nanoparticles.
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All authors Hanwen Jin, Chengcheng Xiao, Matias Herran, Emiliano Cortes, Shiwu Gao, Johannes Lischner
Optics
Upscaling Tomographic Volumetric 3D Printing via Virtual Stitching of Coordinated Projections
Hossein Safari, S. Kaveh Hedayati, Aminul Islam et al. (+1 more)
Tomographic volumetric 3D printing offers layer free, rapid fabrication of objects with high design freedom, but is limited to relatively small curing volumes because of the optical constraints imposed by an assumed need for telecentricity. We present a method to virtually stitch multiple projections from different light sources to build a single workpiece. To avoid the built in requirement for telecentricity and thus the need for an index matching vat, projections are produced by a graphics processing unit accelerated raytracing solver. The method accounts for non ideal light propagation, including nontelecentricity, reflection, refraction, attenuation, as well as any output power mismatch among projectors.Tomographic volumetric 3D printing offers layer free, rapid fabrication of objects with high design freedom, but is limited to relatively small curing volumes because of the optical constraints imposed by an assumed need for telecentricity. We present a method to virtually stitch multiple projections from different light sources to build a single workpiece. To avoid the built in requirement for telecentricity and thus the need for an index matching vat, projections are produced by a graphics processing unit accelerated raytracing solver. The method accounts for non ideal light propagation, including nontelecentricity, reflection, refraction, attenuation, as well as any output power mismatch among projectors.
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All authors Hossein Safari, S. Kaveh Hedayati, Aminul Islam, Yi Yang
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Higher-Order-Phonon Scattering Governs Targeted Control of Heat Conduction in Bulk Boron Arsenide
Tianhao Li, Yangjun Qin, Dongkai Pan et al. (+3 more)
Conventional approaches for modulating thermal conductivity usually rely on structural modifications and therefore cannot achieve reversible in situ regulation. Targeted
phonon excitation has recently emerged as a promising strategy for dynamically tuning thermal transport, but its applicability has so far been demonstrated mainly in two-dimensional systems. Here, we extend this strategy to a three-dimensional bulk material by taking boron arsenide (BAs) as a representative example. Based on first-principles calculations and
phonon Boltzmann transport analysis, we show that targeted
phonon excitation modulates the thermal conductivity of bulk BAs in a strongly frequency-dependent manner. Within the three-
phonon-only framework, the modulation at 300 K is weak but clearly bidirectional. However, once four-
phonon scattering is included, the modulation changes qualitatively to a predominantly suppressive behavior. In the combined three-
phonon plus four-
phonon (3ph+4ph) framework, the strongest suppression occurs at 20.5 THz, where the relative thermal conductivity decreases to 0.828 and 0.415 for excitation intensities of 5 and 25, respectively. By comparing the 3ph-only and 3ph+4ph results, we show that four-
phonon scattering plays a decisive role in determining the net modulation effect by raising the intrinsic scattering background and promoting a more systematic excitation-induced increase in the scattering of low-frequency heat-carrying
phonons.
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All authors Tianhao Li, Yangjun Qin, Dongkai Pan, Shixian Liu, Han Meng, Nuo Yang
Applied Physics
A controllable anti-P-pseudo-Hermitian mechanical system and its application
Yanzheng Wang, Jianlei Zhao, Qian Wu et al. (+5 more)
A novel anti-P-pseudo-Hermitian mechanical system that integrates piezoelectric actuators and sensors with non-reciprocal coupling into mechanical beams is proposed. This configuration enables the system to exhibit programmable exceptional points (EPs), which are critical for enhancing sensitivity in sensing applications. Our theoretical analysis, supported by numerical simulations and experimental validation, demonstrates the system's capability to detect minute mass variations and identify surface cracks with high precision. This advancement not only contributes to the field of non-Hermitian physics but also paves the way for the development of next-generation mechanical sensors leveraging EP physics.
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All authors Yanzheng Wang, Jianlei Zhao, Qian Wu, Xiaoming Zhou, Heng Jiang, Weiqiu Chen, Mu Wang, Guoliang Huang
Computational Physics · Cross-listed from eess.SY
Topology optimization of nonlinear forced response curves via reduction on spectral submanifolds
Hongming Liang, Matteo Pozzi, Jacopo Marconi et al. (+2 more)
Forced response curves (FRCs) of nonlinear systems can exhibit complex behaviors, including hardening/softening behavior and bifurcations. Although
topology optimization holds great potential for tuning these nonlinear dynamic responses, its use in high-dimensional systems is limited by the high cost of repeated response and sensitivity analyses. To address this challenge, we employ the spectral submanifolds (SSMs) reduction theory, which reformulates the periodic response as the
equilibria of an associated reduced-order model (ROM). This enables efficient and analytic evaluation of both response amplitudes and their sensitivities. Based on the SSM-based ROM, we formulate optimization problems that optimize the peak amplitude, the hardening/softening behavior, and the distance between two saddle-node bifurcations for an FRC. The proposed method is applied to the design of nonlinear MEMS devices, achieving targeted performance optimization. This framework provides a practical and efficient strategy for incorporating nonlinear dynamic effects into the
topology optimization of structures.
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All authors Hongming Liang, Matteo Pozzi, Jacopo Marconi, Shobhit Jain, Mingwu Li
Plasma Physics
Ion Stochastic Heating by Low-frequency Alfvén Wave Spectrum
Jingyu Peng and Jiansen He
Finite-amplitude low-frequency Alfvén waves are commonly found in
plasma environments, such as space
plasmas, and play a crucial role in ion heating. The nonlinear interaction between oblique Alfvén wave spectra and ions has been studied. As the number of wave modes increases, ions are more likely to exhibit chaotic motion and experience
stochastic heating. The
stochastic heating threshold in the parameter space can be characterized by a single parameter, the effective relative
curvature radius $P_{{eff.}}$. The results show excellent agreement with the chaotic regions identified through test particle simulations. The anisotropic characteristics of
stochastic heating are explained using a uniform solid angle distribution model. The
stochastic heating rate $Q=\dot{T}$ is calculated, and its relationship with wave conditions is expressed as $Q/(\Omega_i m_i v_A^2) = H(\alpha) \tilde{v}^3 \tilde{B}_w^2 \tilde{\omega}_1$, where $\alpha$ is propagating angle, $\Omega_i$ is the gyrofrequency, $m_i$ is the ion mass, $v_A$ is the Alfvén speed, $\tilde{v}$ is the dimensionless speed, $\tilde{B}_w$ is the dimensionless wave amplitude, and $\tilde{\omega}_1$ is the lowest dimensionless wave frequency.
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Chemical Physics
Graphene nanowindows as a basis for creating mechanically robust nanohydroxyapatite bone lamellar scaffolds
Radovan Kukobat, Ranko Škrbić, Sanja Jovičić et al. (+13 more)
The role of
graphene nanowindows in the nanohydroxyapatite bone scaffold preparation is important for the preparation of mechanically robust scaffolds and implementation in bone recovery. Here, we report a
graphene-nanohydroxyapatite (G-nHAP) scaffold synthesized by the hydrothermal method, along with its formation mechanism and promising in vivo applications. The G-nHAP scaffold exhibits excellent mechanical strength comparable to that of cancellous bone. The nHAP was grown on 2D layers of
graphene with nanowindows. The role of nanowindows was to attract electrostatically Ca2+, PO43+, and OH- precursors of nHAP, forming a layered structure of G-nHAP, in which nHAP nanorods of 23.8 nm in diameter and 84.7 nm in length were placed between
graphene layers, as evidenced with molecular dynamic simulations. In vivo study showed mature and mineralized bone and osteoid after six weeks. This demonstrates the role of
graphene nanowindows in the formation of nHAP scaffolds that are promising for future implementation in bone tissue regeneration.
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All authors Radovan Kukobat, Ranko Škrbić, Sanja Jovičić, Milka Matičić, Aneta Stojmenovski, Marko Bulajić, Saša Marin, Darko Bodroža, Dragana Stević, Suzana Gotovac Atlagić, Nenad Ignjatović, Fernando Vallejos-Burgos, Elisa Mercadelli, Jessica Ponti, Francesco Fumagalli, Andrea Valsesia
Plasma Physics
Full-wave computation of SUb-atmospheric Radio-frequency Engine (SURE)
Dingzhou Li, Lei Chang and Ye Tao
Near-space, which covers altitudes from 20 to 100 kilometers, has been receiving more and more
attention because of its special strategic value. Airships and high-altitude balloons are two common types of low-speed vehicles that operate in this region. They can be used for jobs like monitoring, communication, and remote sensing, but they need efficient propulsion systems to work well. Earlier, we proposed a new type of electric propulsion system that can ionize the surrounding air to create
plasma and produce thrust for near-space vehicles. However, in past experiments, not enough was known about how certain parameters affect power absorption and electromagnetic behavior. Therefore, in this study, we used computer simulations to examine how gas pressure (200 to 1000 Pa), input power (200 to 600 W), frequency (13.56 to 52.24 MHz), and different gas types ($Ar$, $N_2$, $H_2$, $He$) influence inductively coupled
plasma inside a quartz tube. We especially focused on comparing two
antenna designs: one with a single turn and one with five turns. In all the simulations, the single-turn
antenna consistently absorbed power better than the five-turns
antenna. Higher frequencies significantly influence both
plasma power absorption and
magnetic field characteristics. The optimal power absorption occurs at a filling gas pressure of 400 Pa. When varying the input power, we observed an initial decrease followed by an increasing trend, which may be related to ionization mechanisms. In comparisons among different gas types, the inelastic collision mechanisms in molecular gases lead to a notable reduction in
plasma power absorption efficiency. The results from this work will help guide the design of future experiments for this electric propulsion concept.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Three-Dimensional Electrostatic and Quantum-Confinement Modeling of Silicon Nanowire Double Quantum Dots
Nilesh Pandey, Dipanjan Basu, Leonard F Register et al. (+1 more)
We present a three-dimensional simulation study of silicon nanowire double
quantum dots (DQDs) with leads at T = 2 K, which extends beyond traditional effective mass or quasi-1D and quasi-2D approaches typically applied to bulk or planar geometries. A 3-D Poisson solver is self-consistently coupled to 2-D Schrodinger along slices normal to transport (width * thickness) to obtain spatially varying subbands and wavefunctions at T = 2 K. The slice approximation is justified by the large aspect ratio (Ltot/W > 20) and by the small (< 1.2 percent) wavefunction variation observed along the transport direction. The resulting effective conduction-band profile is imported into a full-wave, open-boundary Schrodinger solver to compute the transmission spectrum T(E), and the tunnel coupling (tc) is evaluated from the bonding and antibonding splitting of the first two resonances in T(E). The simulations show that narrow dots (W = 5 nm) provide strong confinement and robust single-electron localization but require higher plunger-gate voltage, whereas wider dots (W = 20 nm) load electrons at lower bias but form shallower, more delocalized states. The tunnel coupling decreases as the dot width and length are increased, due to the reduced wavefunction overlap between the dots, and saturates once W > 2LPG, when longitudinal confinement is dominated by the plunger gate length. The simulated tunnel coupling trend agrees with experimental data reported for the Si DQD device.
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All authors Nilesh Pandey, Dipanjan Basu, Leonard F Register, Sanjay K Banerjee
Instrumentation and Detectors · Cross-listed from hep-ex
Constraints on inelastic dark matter from the CDEX-1B experiment
Y. F. Liang, L. T. Yang, Q. Yue et al. (+85 more)
We present limits on
spin-independent inelastic weakly interacting massive particles (WIMP)-
nucleus scattering using the 737.1 kg$\cdot$day
dataset from the CDEX-1B experiment. Expected
nuclear recoil spectra for various inelastic WIMP masses $m_\chi$ and mass splittings $\delta$ are calculated under the standard
halo model. An accurate background model of CDEX-1B is constructed by simulating all major background sources. The model parameters are then determined through maximum likelihood estimation and Markov chain Monte Carlo fitting. The resulting 90% confidence level upper limits on the WIMP-nucleon cross section $\sigma_{\mathrm{n}}$ exclude certain DAMA/LIBRA allowed regions: the $\chi^2 < 4$ regions for $\delta < 30$ keV at $m_\chi = 250$ GeV and the $\chi^2 < 9$ region for $\delta < 50$ keV at $m_\chi = 500$ GeV. The method is applicable to other inelastic dark matter scenarios, and the upcoming CDEX-50 experiment is expected to improve sensitivity by four orders of magnitude.
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All authors Y. F. Liang, L. T. Yang, Q. Yue, K. J. Kang, Y. J. Li, H. P. An, Greeshma C., J. P. Chang, H. Chen, Y. H. Chen, J. P. Cheng, J. Y. Cui, W. H. Dai, Z. Deng, Y. X. Dong, C. H. Fang, H. Gong, Q. J. Guo, T. Guo, X. Y. Guo, L. He, J. R. He, H. X. Huang, T. C. Huang, S. Karmakar, Y. S. Lan, H. B. Li, H. Y. Li, J. M. Li, J. Li, M. C. Li, Q. Y. Li, R. M. J. Li, X. Q. Li, Y. L. Li, B. Liao, F. K. Lin, S. T. Lin, J. X. Liu, R. Z. Liu, S. K. Liu, Y. D. Liu, Y. Liu, Y. Y. Liu, H. Ma, Y. C. Mao, A. Mureed, H. Pan, N. C. Qi, J. Ren, X. C. Ruan, M. B. Shen, H. Y. Shi, M. K. Singh, T. X. Sun, W. L. Sun, C. J. Tang, Y. Tian, H. F. Wan, G. F. Wang, J. Z. Wang, L. Wang, Q. Wang, Q. Wang, Y. F. Wang, Y. X. Wang, H. T. Wong, Y. C. Wu, H. Y. Xing, K. Z. Xiong, R. Xu, Y. Xu, T. Xue, Y. L. Yan, N. Yi, C. X. Yu, H. J. Yu, X. Yu, M. Zeng, Z. Zeng, F. S. Zhang, P. Zhang, P. Zhang, Z. Y. Zhang, M. G. Zhao, J. F. Zhou, Z. Y. Zhou, J. J. Zhu
Instrumentation and Detectors
Aluminum-Based Superconducting Tunnel Junction Sensors for Nuclear Recoil Spectroscopy
Spencer L. Fretwell, Connor Bray, Inwook Kim et al. (+31 more)
The BeEST experiment is searching for sub-MeV sterile
neutrinos by measuring
nuclear recoil energies from the decay of $^7$Be implanted into superconducting tunnel junction (STJ) sensors. The
recoil spectra are affected by interactions between the radioactive implants and the sensor materials. We are therefore developing aluminum-based STJs (Al-STJs) as an alternative to existing tantalum devices (Ta-STJs) to investigate how to separate material effects in the
recoil spectrum from potential signatures of physics beyond the Standard Model. Three iterations of Al-STJs were fabricated. The first had electrode thicknesses similar to existing Ta-STJs. They had low responsivity and reduced resolution, but were used successfully to measure $^7$Be
nuclear recoil spectra. The second iteration had STJs suspended on thin SiN membranes by backside etching. These devices had low leakage current, but also low yield. The final iteration was not backside etched, and the Al-STJs had thinner electrodes and thinner tunnel barriers to increase signal amplitudes. These devices achieved 2.96 eV FWHM energy resolution at 50 eV using a pulsed 355 nm (~3.5 eV)
laser. These results establish Al-STJs as viable detectors for systematic material studies in the BeEST experiment.
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All authors Spencer L. Fretwell, Connor Bray, Inwook Kim, Andrew Marino, Benjamin Waters, Robin Cantor, Ad Hall, Pedro Amaro, Adrien Andoche, David Diercks, Abigail Gillespie, Mauro Guerra, Cameron N. Harris, Jackson T. Harris, Leendert M. Hayen, Paul Antoine Hervieux, Geon Bo Kim, Annika Lennarz, Vincenzo Lordi, Jorge Machado, Peter Machule, David McKeen, Xavier Mougeot, Francisco Ponce, Chris Ruiz, Amit Samanta, José Paulo Santos, Joseph Smolsky, Caitlyn Stone-Whitehead, Joseph Templet, Wouter Van De Pontseele, William K. Warburton, K. G. Leach, S. Friedrich
Optics
Super resolving binary-source hypothesis testing with a double-clad fiber coupler
John S. Wallis, David R. Gozzard, Alex M. Frost et al. (+3 more)
We present a technique for binary spatial mode demultiplexing, using a double-clad fiber coupler as an optical mode sorter, for hypothesis testing for one or two point sources in an incident optical field. By directly coupling an optical field through a double-clad fiber coupler, we demultiplex the field into the fundamental mode and a superposition of higher-order modes. We use the ratio of multi-mode to single-mode power to distinguish between single and double point sources. In a tabletop demonstration of the technique, we demonstrate the capability to accurately identify the presence of two sources separated below the Rayleigh limit for relative brightnesses from 0 dB to -20 dB. For sources with less than 5 dB difference in their relative powers, our imaging protocol can correctly determine the presence of a second optical source even when the two sources have separations 50x smaller than the Rayleigh limit. These results highlight the potential of this technique as a simple tool for super-resolving classification of a pair of point emitters, especially in the context of astronomical imaging for binary systems.
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All authors John S. Wallis, David R. Gozzard, Alex M. Frost, Benjamin P. Dix-Matthews, Nicolas Maron, Joshua J. Collier
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Dimension- and Facet-Dependent Altermagnetic Biferroics and Ferromagnetic Biferroics and Triferroics in CrSb
Long Zhang and Guoying Gao
Altermagnets have recently garnered significant interest due to their vanishing net
magnetic moment and non-relativistic momentum-dependent
spin splitting. However, altermagnetic (AM) multiferroics especially triferroics remain scarce. We investigate the experimentally synthesized non-van der Waals CrSb as a model system to explore the effects of dimensionality and facet orientation on its ferroic properties. NiAs, MnP, wurtzite (WZ), zincblende (ZB), and rocksalt (RS) phases are considered. Using first-principles calculations, we predict the altermagnetism of CrSb in MnP phase which has comparable stability with experimental NiAs phase. Both NiAs- and MnP-phase (110) facets exhibit AM-ferroelastic (FC) biferroics, while the WZ-phase bulk and (001) facets host
ferromagnetic (FM) or AM-ferroelectric (FE) biferroics. Notably, the WZ-phase (110) facets are identified as FM/AM-FE-FC triferroics, with moderate energy barriers of 0.129 and 0.363 eV atom-1 for FE and FC switching, respectively. Both FE and FC switching can reverse the AM
spin splitting in
antiferromagnetic (AFM) configurations while preserving the high
spin polarization in FM states. The
magnetic anisotropy is highly tunable, exhibiting either uniaxial or in-plane behavior depending on the phase, dimension, and facet. This work establishes a framework for designing AM multiferroics through polymorphic, dimensional, and facet engineering, offering promising avenues for multifunctional spintronic applications.
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Optics
Voxel-scale quantum state control in nanorod ensembles using reconfigurable needle beams
G. A. Mantashian, D. B. Hayrapetyan and P. A. Mantashyan
Precisely addressing single nanostructures inside dense ensembles remains a bottleneck for scalable photonic and
quantum information devices. Here we demonstrate, through comprehensive finite element and variational Monte-Carlo modelling, that a reconfigurable three-dimensional array of needle shaped beams can selectively switch the
quantum optical response of individual InAs nanorods embedded in GaAs. By tuning the local non resonant intensity pattern the
exciton and biexciton energies were calculated, electromagnetically induced transparency (EIT) windows were examined, and correspondingly near-field diffraction carpets were dynamically reshaped. A single parameter the activation ratio between illuminated and dark nanorods provides continuous control over photoluminescence peak position (80 meV) and EIT bandwidth (six times). We further predict fully programmable Talbot self-imaging in nanorod arrays with sub-wavelength pitch. Importantly, the observed Talbot carpets enable spatially resolved identification of which nanorods were excited, offering a powerful diagnostic for verifying structured-light activation schemes. The concept offers a low crosstalk, wafer scale route toward reconfigurable
quantum emitters, tunable diffractive optics and on-chip slow-light components.
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Fluid Dynamics
Scalings and simulation requirements in two-phase flows
Luis H. Hatashita, Pranav Nathan and Suhas S. Jain
In this work, important two-phase flow scalings are derived, which enable the quantification of grid-point and time-step requirements as functions of Re, We, and Ca numbers. The adequate grid resolution is determined in the inertia-dominated regime with the aid of high-fidelity simulations of stationary two-phase homogeneous isotropic
turbulence by evaluating convergence of total interfacial area, size distribution, SMD, and
curvature distribution. Although standards for DNS for single-phase
turbulence flow exist, there is a lack of similar guidance in two-phase flows. Therefore, length scale ratios of the Kolmogorov-Hinze to the Kolmogorov scale of \eta_{KH}/\eta \sim We_{L}^{-3/5}Re_{L}^{3/4} in the inertia-dominated regime and the Kolmogorov-viscous to Kolmogorov scale of \eta_{KV}/\eta \sim Ca_{L}^{-1}Re_{L}^{3/4} for the viscous-dominated regime, are constructed. These scalings imply a computational cost increase like We_{L}^{12/5} and Ca_{L}^4, in the inertia-dominated and viscous-dominated regimes, respectively. A novel dimensionless number, coined as the ratio of interface scales (Ris), is proposed to aid in the classification of the
turbulence regimes in the presence of an interface. Convergence of the total interfacial area, size distribution, SMD, and
curvature distribution are observed for grid resolutions of k_{\max} \eta_{KH} \geq 60$ for second-order schemes. Furthermore, it is observed that this lower bound is the minimum required to capture intermittent events responsible for the increase of instantaneous total interfacial area. This criterion will be a valuable tool for determining grid resolution and time-step requirements a-priori for DNS of two-phase flows and for estimating the corresponding computational cost. This work provides guidelines and best practices for numerical simulations of two-phase flows, which will accelerate physics discovery and model development.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Probing Phase Diagrams of Ordered Two-Dimensional Ice
Bingzheng Wu, Jianming Wu, Sai Duan et al. (+1 more)
Water, a ubiquitous and fundamental substance, plays a critical role across a wide range of disciplines from physics and chemistry to biology and engineering. Despite theoretical predictions of several phases of two-dimensional (2D) ice confined between idealized hydrophobic walls, experimental validation has been limited to the square phase, whose structural origin remains controversial. Here, we propose a realistic nanoconfinement setup using wide-bandgap hexagonal boron nitride (h-BN) as the capping layer and Cu(111) as the substrate. This protocol enables scanning tunneling microscope (STM) to resolve the atomic-scale arrangement of water molecules beneath the h-BN layer, overcoming the limitations of conventional techniques. Simulated STM images unambiguously identify all ordered flat 2D ice phases, as well as coexisting phases, and effectively distinguish them from potential contaminants. These findings establish a robust framework for experiment to systematically probe the phase structures of 2D ice, opening an avenue for studying nanoconfined water under ambient conditions.
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All authors Bingzheng Wu, Jianming Wu, Sai Duan, Xin Xu