Plasma Physics
BO-PBK: A comprehensive solver for dispersion relations of obliquely propagating waves in magnetized multi-species plasma with anisotropic loss-cone drift product-bi-kappa distribution
Wei Bai and Huasheng Xie
We present BO-PBK (BO-Product-Bi-Kappa), a new solver for kinetic dispersion relations of obliquely propagating waves in magnetized
plasmas with complex velocity distributions. It reformulates the linearized Vlasov-Maxwell system into a compact
eigenvalue problem, enabling direct computation of multiple wave branches and unstable modes without iterative initial-value searches. Key innovations include a unified framework supporting product-bi-kappa, kappa-Maxwellian, bi-Maxwellian, and hybrid distributions with multi-component and loss-cone features; a concise rational-form
eigenvalue formulation; and a 2–3 times reduction in
matrix dimensions compared to the BO-KM solver, with improved efficiency at larger kappa indices.
Benchmark tests confirm accurate reproduction of standard kinetic results and efficient resolution of waves and instabilities. BO-PBK thus provides a computationally efficient tool for wave and stability analysis in space and laboratory
plasmas.
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Applied Physics · Cross-listed from quant-ph
Single Flux Quantum Circuit Operation at Millikelvin Temperatures
Jason Walter, Adam C. Weis, Kan-Ting Tsai et al. (+6 more)
As
quantum computing processors increase in size, there is growing interest in developing cryogenic electronics to overcome significant challenges to system scaling. Single flux-
quantum (SFQ)
circuits offer a promising alternative to remote, bulky, and power-hungry room temperature electronics. To meet the need for digital
qubit control, readout, and co-processing, SFQ
circuits must be adapted to operate at millikelvin temperatures near
quantum processors. SEEQC's SFQuClass digital
quantum management approach proximally places energy-efficient SFQ (ERSFQ)
circuits and
qubits in a multi-chip module. This enables extremely low power dissipation, compatible with a typical dilution cryostat's limited cooling power, while maintaining high processing speed and low error rates. We report on systematic testing from 4 K to 10 mK of a comprehensive set of ERSFQ
cells, as well as more complex
circuits such as programmable counters and demultiplexers used in digital
qubit control. We compare the operating margins and error rates of these
circuits and find that, at millikelvin, bias margins decrease and the center of the margins (i.e., the optimal bias current value) increases by ~15%, compared to 4.2 K. The margins can be restored by thermal annealing by reducing Josephson junction (JJ) critical current Ic. To provide guidance for how
circuit parameters vary from 4.2 K to millikelvin, relevant analog process control monitors (PCMs) were tested in the temperature range of interest. The measured JJ critical current (of the PCM JJ arrays) increases by ~15% when decreasing temperature from 4.2 K to millikelvin, in good agreement with both theory and the empirically measured change in the center of bias margins for the tested digital
circuits.
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All authors Jason Walter, Adam C. Weis, Kan-Ting Tsai, Meng-Ju Yu, Naveen Katam, Alex F. Kirichenko, Oleg A. Mukhanov, Shu-Jen Han, Igor V. Vernik
Optics · Cross-listed from cond-mat.stat-mech
Geometry protected probabilistic structure in many-body dynamics
Yue Liu, Chushun Tian and Dahai He
Insomuch as statistical mechanics circumvents the formidable task of addressing many-body dynamics, it remains a challenge to derive macroscopic properties from a solution to
Hamiltonian equations for microscopic motion of an isolated system. Launching new attacks on this long-standing problem – part of
Hilbert's sixth problem – is urgently important, for focus of statistical phenomena is shifting from a fictitious ensemble to an individual member, i.e. a mechanically isolated system. Here we uncover a common probabilistic structure, the concentration of measure, in
Hamiltonian dynamics of two families of systems, the
Fermi-Pasta-Ulam-Tsingou (FPUT) model which is finite-dimensional and (almost) ergodic, and the Gross-Pitaevskii equation (GPE) which is infinite-dimensional and suffers strong ergodicity breaking. That structure is protected by the geometry of phase space and immune to ergodicity breaking, leading to counterintuitive phenomena. Notably, an isolated FPUT behaves as a thermal ideal gas even for strong modal interaction, with the thermalization time analogous to the Ehrenfest time in
quantum chaos, while an isolated GPE system, without any
quantum inputs, escapes the celebrated ultraviolet catastrophe through nonlinear wave localization in the mode space, and the Rayleigh-Jeans
equilibrium sets in the localization volume. Our findings may have applications in nonlinear optics and cold-atom dynamics.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Observation of Stable Bimeron Transport Driven by Spoof Surface Acoustic Waves on Chiral Metastructures
Huaijin Ma, Te Liu, Jiachen Sheng et al. (+3 more)
Topological quasiparticles, such as merons and bimerons, are characterized by non-trivial textures that exhibit remarkably robust transport against deformation, offering significant potential for information processing. While these phenomena have been explored in various systems, acoustic realizations remain challenging. Here, we report that acoustic meron topological textures were successfully realized using designed Archimedeanlike square spiral metastructures via the excitation of spoof surface acoustic waves (SSAWs). By applying mirror-symmetric combinatorial operations to the unit structures, we further construct composite
chiral metastructures that enable both one-dimensional and two-dimensional stable transport of acoustic bimerons. It is further revealed that bimeron transport originates from the locked opposite phase differences of SSAWs, induced by the handedness of the cavity resonant modes. The intrinsic robustness of the meron textures against structural defects is confirmed through the calculation of their topological charge. Our findings establish stable acoustic bimeron transport as a topologically resilient foundation for future acoustic information processing and storage technologies.
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All authors Huaijin Ma, Te Liu, Jiachen Sheng, Kaiyan Cao, Jinpeng Yang, Jian Wang
Classical Physics
Revisiting the Acousto-Electric Effect
Ewan M Wright, John Mack, Alex Wendt et al. (+4 more)
The goal of this paper is to provide a new perspective on the acousto-electric effect by deriving a wave equation for the acoustic field that is akin to Stokes 1845 viscous wave equation and in which the
phonon-electron interaction provides the loss/gain term. We hope this new perspective may provide some insight into the workings of the acousto-electric effect, and we use it to build connections to other areas of research, in particular inertial motion superradiance and the Zel'dovich effect.
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All authors Ewan M Wright, John Mack, Alex Wendt, Austin Burrington, Will Roberts, Dalton Anderson, Matt Eichefield
Chemical Physics
Synchronous Differential Hot-charge Emission Spectroscopy: The Principle
Xuan Ji, Wen Chen and Xi Yu
Energy-level
alignment (ELA) at buried interfaces between electrode and molecular materials sets charge injection barriers, carrier selectivity, and ultimately device efficiency, yet it is challenging to quantify under operating conditions. Hot-charge emission spectroscopy (HotES) probes ELA by injecting ballistic carriers across a tunneling
oxide. Yet, the technique inherently convolutes the molecular response with a strong, energy-dependent tunneling background, complicating the isolation of the true ELA. We introduce synchronous differential HotES (sd-HotES), defined as the ratio of the differential conductance of the hot-charge and tunneling channels of the HotES. Physical modeling and numerical simulations validate that this ratio directly reconstructs the intrinsic molecular charge transmission, enabling the threshold-free and probe-bias-insensitive extraction of ELA. By effectively eliminating the masking tunneling background, sd-HotES substantially boosts detection sensitivity; weak spectral features previously hidden in conventional HotES become clearly resolvable, as demonstrated in lock-in simulations including realistic noise. This study establishes the fundamental operating principles of sd-HotES and highlights it as a powerful, broadly applicable strategy for accessing buried interface properties for the study of molecular and hybrid devices.
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Fluid Dynamics
The macroscopic contact angle of water on ice
W. Sarlin, D.V. Papa, R. Grivet et al. (+4 more)
Wettability quantifies the affinity of a
liquid over a substrate, and determines whether the surface is repellent or not. When both the
liquid and the solid phases are made of the same chemical substance and are at thermal
equilibrium, complete wetting is expected in principle, as observed for instance with drops of molten metals spreading on their solid counterparts. However, this is not the case for water on ice. Although there is a growing consensus on the partial wetting of water on ice and several estimates available for the value of the associated contact angle, the question of whether these values correspond to the
equilibrium angle without thermal effects is still open. In the present paper, we address this issue experimentally and demonstrate the existence of a macroscopic contact angle of water on ice using theoretical arguments. Indeed, when depositing water droplets on smooth ice layers with accurately controlled surface temperatures, we observe that spreading is unaffected by thermal effects and phase change close enough to the melting point. Whereas the short time \C{motion of the contact line} is driven by an inertial-capillary balance, the
evolution towards
equilibrium is described by a viscous-capillary dynamics and is therefore capillary - and not thermally - related. Moreover, we show that this contact angle remains constant for undercoolings below 1 K. This way, we show the existence of a non-zero
equilibrium contact angle of water on ice, that it is very close to 12$^\circ$. We anticipate this key finding to significantly improve the understanding of capillary flows in the presence of phase change, which is especially useful in the context of ice morphogenesis and of glaciology, but also in the aim of developing numerical methods for resolving triple-line dynamics.
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All authors W. Sarlin, D.V. Papa, R. Grivet, A. Rosenbaum, A. Huerre, T. Séon, C. Josserand
Optics
Multiple reentrant topological windows induced by generalized Bernoulli disorder
Ruijiang Ji, Yunbo Zhang, Shu Chen et al. (+1 more)
We investigate reentrant topological transitions in a one-dimensional Su-Schrieffer-Heeger chain with generalized Bernoulli disorder in the intradimer hopping amplitudes. Owing to its independently tunable values and probabilities, the multivalued disorder distribution provides a direct way to control the topological phase diagram. We show that increasing the disorder strength can split the nontrivial regime into multiple disconnected topological windows, whose number, widths, and locations are determined by the distribution parameters. The phase boundaries are derived analytically from the zero-mode inverse localization length and are governed by a weighted
geometric mean of the disordered hopping amplitudes, in agreement with numerical results from the reflection-
matrix topological
quantum number and the real-space winding number. We also show that the mean
chiral displacement dynamically identifies these reentrant windows. These results demonstrate how multivalued random disorder can organize and tune reentrant topological behavior in one-dimensional
chiral lattices.
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All authors Ruijiang Ji, Yunbo Zhang, Shu Chen, Zhihao Xu
Plasma Physics
FGE: A Fast Free-Boundary Grad-Shafranov Evolutive Solver
Cosmas Heiß, Antoine Merle, Francesco Carpanese et al. (+5 more)
Accurate and rapid simulation of the free boundary tokamak
plasma equilibrium evolution is essential for modern
plasma control, stability analysis, and scenario development. This paper presents the Free-Boundary Grad-Shafranov Evolutive (FGE) code, a highly flexible and control-oriented solver designed to address the challenges posed by advanced
plasma configurations across a range of devices. FGE evolved from the FBT and LIUQE codes and is part of the MEQ suite, sharing many of the low-level optimized functions. It self-consistently solves the free-boundary Grad-Shafranov equation coupled with
circuit equations for external conductors and models for
plasma profile
evolution. The code implements a fully non-linear, Newton-based framework with multiple, highly optimized solver options, state representations, and residual formulations that enable rapid computation across different simulation setups. A key capability is the self-consistent integration of various 0D and 1D current
diffusion equations (CDEs) to model the resistive
evolution of the
plasma current profile as well as the ability to model
plasmas with multiple
magnetic axes (Doublets). Furthermore, FGE allows to linearize the
plasma dynamics around a given
equilibrium to generate a state-space model suitable for controller design and analysis. Numerical studies are presented demonstrating the code's speed of convergence and validating its performance against experimental data. Furthermore,
benchmarks against the RAPTOR and KINX codes for profile
evolution and vertical growth rate estimates are presented highlighting FGE's capabilities for both prediction and analysis.
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All authors Cosmas Heiß, Antoine Merle, Francesco Carpanese, Federico Felici, Craig Donner, Stefano Marchioni, Alessandro Mari, Olivier Sauter
Atomic Physics
Thermal one-loop self-energy correction for hydrogen-like systems: Relativistic approach
M. A. Reiter, D. A. Solovyev, A. A. Bobylev et al. (+2 more)
Within a fully relativistic framework, the one-loop self-energy correction for a bound electron is derived and extended to incorporate the effects of external thermal radiation. In a series of previous works, it was shown that in
quantum electrodynamics at finite temperature (QED), the description of effects caused by blackbody radiation can be reduced to using the thermal part of the
photon propagator. As a consequence of the non-relativistic approximation in the calculation of the thermal one-loop self-energy correction, well-known
quantum-mechanical (QM) phenomena emerge at successive orders: the Stark effect arises at leading order in $\alpha Z$, the Zeeman effect appears in the next-to-leading non-relativistic correction, accompanied by diamagnetic contributions and their relativistic refinements, among other perturbative corrections. The fully relativistic approach used in this work for calculating the SE contribution allows for accurate calculations of the thermal shift of atomic levels, in which all these effects are automatically taken into account. The hydrogen atom serves as the basis for testing a fully relativistic approach to such calculations. Additionally, an analysis is presented of the behavior of the thermal shift caused by the thermal one-loop correction to the self-energy of a bound electron for hydrogen-like ions with an arbitrary
nuclear charge $Z$. The significance of these calculations lies in their relevance to contemporary high-precision experiments, where thermal radiation constitutes one of the major contributions to the overall uncertainty budget.
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All authors M. A. Reiter, D. A. Solovyev, A. A. Bobylev, D. A. Glazov, T. A. Zalialiutdinov
Fluid Dynamics
Inertial rotation of a small oblate spheroid in a simple shear flow
Ziqi Wang, Xander M. de Wit, Davide Di Giusto et al. (+5 more)
We compare experiments and fully-resolved particle simulations designed to match the experimental conditions of a weakly inertial, neutrally buoyant, moderately oblate spheroid in shear flow under confinement. The study revisits an apparent discrepancy observed in earlier experiments, where a trajectory starting close to tumbling appeared to remain near the tumbling orbit, whereas weak-inertia theory predicts attraction to log-rolling for this particle shape. Experimental and numerical results are benchmarked against theory valid for asymptotically small particle Reynolds numbers and for unconfined systems. By accounting for confinement and inertia, together with sensitivity to initial conditions, and the finite observation time, we provide a consistent interpretation of the theoretical, experimental, and numerical results. Specifically, we show that log rolling is the only stable long-time orbit for the moderately oblate spheroid considered here; neither confinement nor finite inertia changes this orbit selection. Instead, inertia tends to accelerate the drift toward log rolling, whereas confinement reduces it, with the confinement effect being dominant in the present parameter range.
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All authors Ziqi Wang, Xander M. de Wit, Davide Di Giusto, Laurence Bergougnoux, Elisabeth Guazzelli, Cristian Marchioli, Bernhard Mehlig, Federico Toschi
Fluid Dynamics
Birth of a bubble: Drop impact onto a thin liquid film for an immiscible three-fluid system
Pierre-Antoine Maës, Alidad Amirfazli and Christophe Josserand
When a drop impacts a solid substrate or a thin
liquid film, a thin gas disc is entrapped due to surface tension, the gas disc retracts into one or several bubbles. While the
evolution of the gas disc for impact on solid substrate or film of the same fluid as the drop have been largely studied, little is known on how it varies when the
liquid of the film is different that of the drop. We study numerically the latter unexplored area, focussing on the contact between the drop and the film, leading to the formation of the air bubble. The volume of fluid method was adapted to three fluids in the framework of Basilisk solver. The numerical simulations show that the deformation of the
liquid film due to the air cushioning plays a crucial role in the bubble entrapment. A new model for the contact time and the entrapment geometry was deduced from the case of the impact on a solid substrate. This was done by considering the deformation of the thin immiscible
liquid layer during impact depending mainly on its thickness and viscosity. The lubrication of the gas layer was found to be the major effect governing the bubble entrapment. However the film viscosity was also identified as having a critical role in bubble formation and
evolution; the magnitude of its influence was also quantified.
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Optics
Nonperturbative regime of low-order harmonic generation in intense low-frequency laser field
S. A. Bondarenko and V. V. Strelkov
We find the atomic response to the intense femtosecond
laser pulse via solving numerically the three-dimensional non-stationary Schrödinger equation (TDSE) for a model atom and calculating its dipole moment. For weak quasi-static fields, the response is well described by a perturbation approach, but for intensities higher than about $0.6 \, \, 10^{14}$ W/cm$^2$ the accuracy of this description is unsatisfactory, regardless of the order of non-linearity taken into account. We suggest fitting the numerical TDSE solution results with a Padé expansion, and show that this approximation describes the response well both in the perturbative regime and beyond it for intensities approximately up to $1.4 \, \, 10^{14}$ W/cm$^2$. To consider the non-perturbative nonlinearity beyond the quasi-static limit we use the model of nonlinear oscillator with the restoring force defined by the found Padé expression. Our model fails to predict the behaviour of the nonlinear refractive index in the nonperturbative domain, but it describes well the nonperturbative growth of the efficiency with the
laser intensity for other nonlinear optical processes, namely, the third and fifth harmonic generation in the IR field and the optical rectification in a two-color field.
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Optics
Leveraging Pre-trained Neural Network Models for the Classification of Tumor Cells Analyzed by Label-free Phase Holotomographic Microscopy
Leonor V. C. Losa, Temple A. Douglas, Lia Santos et al. (+4 more)
Can a single label-free image reveal whether cancer
cells were exposed to chemotherapy? We present an innovative methodology on the label-free and high-resolution imaging properties of phase holotomographic microscopy coupled with neural network models for the classification of cancer
cells. Using 3D phase holotomographic microscopy, we imaged live A549 lung cancer
cells with and without paclitaxel, converted stacks to 2D maximum-intensity projections, and evaluated pre-trained convolutional networks (VGG16, ResNet18, DenseNet121, and EfficientNet-B0) for binary classification of treatment status. EfficientNet-B0 achieved 96.9 % accuracy on unsegmented images. Refractive index analysis revealed bimodal distribution in treated
cells, reflecting heterogeneous biophysical responses to paclitaxel exposure and supporting the network's ability to detect subtle, label-free indicators of drug action. As further proof-of-concept, the same pipeline separated holotomographic images of label-free, high versus low-graded urothelial cancer
cells with high accuracy (90.6 %). These findings highlight the potential of integrating label-free holotomographic imaging with deep learning techniques for rapid and efficient classification of tumor
cells, paving the way for advancements in treatment optimization and personalized diagnostic strategies.
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All authors Leonor V. C. Losa, Temple A. Douglas, Lia Santos, Raquel Monteiro, Isabel Calejo, Raphael F. Canadas, Jana B. Nieder
Applied Physics · Cross-listed from eess.SP
Effective Electromagnetic Degrees of Freedom in Backscatter MIMO Systems
Philipp del Hougne
While the definition of the effective electromagnetic degrees of freedom (EEMDOFs) of a static linear multiple-input multiple-output (
MIMO) system is well established, the counterpart for a backscatter
MIMO (BS-
MIMO) system is so far missing. A BS-
MIMO system encodes the input information into the loads of backscatter elements. Due to mutual coupling, the mapping from load configuration to observed fields is fundamentally non-linear, which complicates the analysis of BS-EEMDOFs. We introduce a definition of BS-EEMDOFs based on the Jacobian of the observed fields with respect to the load configuration. We derive a closed-form expression from multiport network theory which demonstrates that the number of BS-EEMDOFs is fundamentally a distributed variable, whose distribution depends on the mutual coupling between the backscatter elements and the coherent illumination. The modes associated with BS-EEMDOFs lie in the column space of the end-to-end channel
matrix from backscatter array ports to receiver ports, but the number of BS-EEMDOFs is generally different from the number of
benchmark EEMDOFs associated with the same array being coherently fed rather than tunably terminated. The dependence on the coherent illumination yields optimized coherent illumination as a control knob for the number of BS-EEMDOFs. We present numerical and experimental results for the evaluation and optimization of the number of BS-EEMDOFs in different
radio environments with reconfigurable intelligent surfaces.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Polaron-Driven Spin Funneling through Rashba-Split Bands in Mixed-Phase Quasi-Two-Dimensional Ruddlesden-Popper Perovskites
Sushovan Sarkar, Koushik Gayen, Ashish Soni et al. (+1 more)
Metal halide perovskites (MHPs) exhibit pronounced
spin-orbit coupling (SOC) as a result of their heavy metal constituents, leading to distinctive electronic properties such as Rashba type band splitting which make them promising candidates for next generation spintronic applications. Here, using circularly polarized luminescence (CPL) and polarization dependent pump-probe spectroscopy, we found that
spin polarization is present across all phases of our two-dimensional (2D) Ruddlesden-Popper (RP) mixed-phase perovskites, (C6H7SNH3)2 (CH3NH3)n-1PbnI3n+1 (n=1-4), irrespective of the number of inorganic layers. The origin of these
spin polarized bands is attributed to the Rashba effect. Interestingly, the highly disordered nature of this system facilitates remarkably efficient ultrafast funneling of photoexcited
spin-polarized
excitons from the pure 2D phase (n=1) to higher-n phases at room temperature. We demonstrate that significant polaron formation due to the inherent soft
crystal lattice and higher
exciton-
phonon interaction is responsible for the observed
spin funneling effect in mixed-phase 2D RP perovskites. Polaron act as a protective mechanism for
spin-polarized
excitons, preserving their
spin information through the screening of omnipresent
phonon-induced momentum scattering. These findings not only offer valuable guidance for the design of 2D RP perovskites with pronounced Rashba effects but also unveil a compelling class of solution-processed perovskites capable of efficient
spin-preserving energy transport at room temperature.
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All authors Sushovan Sarkar, Koushik Gayen, Ashish Soni, Suman Kalyan Pal
Classical Physics · Cross-listed from cond-mat.mtrl-sci
Halide Perovskite-Chalcohalide Nanocrystal Heterostructures as a Platform for the Synthesis and Investigation of the CsPbCl3-CsPbI3 Epitaxial Interface
Nikolaos Livakas, Irina Skvortsova, Juliette Zito et al. (+10 more)
Halide exchange in lead-based halide perovskites has been studied extensively. While mixed Cl-Br or Br-I
alloy compositions can be formed with no miscibility gaps, this is precluded for mixed Cl-I compositions, due to the large difference in Cl and I ionic radii. Here, we exploit perovskite-chalcohalide CsPbCl3-Pb4S3Cl2
heterostructures to study the Cl-I exchange and isolate new types of intermediate structures. The epitaxial interface between the Pb4S3Cl2 chalcohalide and the CsPbCl3 perovskite domain significantly influences the intermediate stages of halide exchange in the perovskite domain, leading to coexisting CsPbCl3 and CsPbI3 domains, thereby delivering segmented CsPbI3-CsPbCl3-Pb4S3Cl2 energetically favorable
heterostructures, with partial iodide alloying of the CsPbCl3 domain and at the perovskite-chalcohalide interface. The I:CsPbCl3 domain between CsPbI3 and Pb4S3Cl2 enables a gradual
lattice expansion across the
heterostructure. This design accommodates interfacial strain, with a 5.6% mismatch at the CsPbCl3-CsPbI3 interface and a 3.4% mismatch at the perovskite-chalcohalide interface. Full halide exchange leads to CsPbI3-Pb4S3Cl2
heterostructures. Both in intermediate and fully exchanged
heterostructures, the CsPbI3 domain is emissive. In the intermediate structures, the band
alignment between the two perovskite domains is type-I, with carriers photogenerated in the CsPbCl3 domain quickly transferring to the CsPbI3 domain, where they can recombine radiatively.
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All authors Nikolaos Livakas, Irina Skvortsova, Juliette Zito, Yurii P. Ivanov, Aswin Asaithambi, Andrea Toma, Annick De Backer, Muhammad Imran, Sandra Van Aert, Giorgio Divitini, Ivan Infante, Sara Bals, Liberato Manna
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Nanocrystals Heterostructures based on Halide Perovskites and Metal Sulfides
Nikolaos Livakas, Juliette Zito, Yurii P. Ivanov et al. (+4 more)
We report the synthesis of nanocrystal
heterostructures composed of CsPbCl3 and PbS domains sharing an epitaxial interface. We were able to promote the growth of a PbS domain (in competition with the more commonly observed Pb4S3Cl2 one) on top of the CsPbCl3 domain by employing Mn2$^+$ ions, the latter acting most likely as scavengers of Cl$^-$ ions. Complete suppression of the Pb4S3Cl2 domain growth was then achieved by additionally selecting an appropriate sulfur source (bis(trimethylsilyl)sulfide, which also acted as scavenger of Cl$^-$ ions), and reaction temperature. In the
heterostructures, emission from the perovskite domain was quenched, while emission from the PbS domain was observed, pointing to a type-I band
alignment, as confirmed by calculations. These
heterostructures in turn could be exploited to prepare second-generation
heterostructures through selective ion exchange on the individual domains (halide ion exchange on CsPbCl3, cation exchange on PbS). We demonstrate the cases of Cl$^-$ to Br$^-$ and Pb2$^+$ to Cu$^+$ exchanges, which deliver CsPbBr3@PbS and CsPbCl3@Cu2-xS epitaxial
heterostructures, respectively.
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All authors Nikolaos Livakas, Juliette Zito, Yurii P. Ivanov, Clara Otero Martínez, Giorgio Divitini, Ivan Infante, Liberato Manna
Applied Physics
Application of Time-Controlled Critical Point in Pressure Reducing Valves. A Case Study in North Spain
Andres Ortega-Ballesteros, David Munoz-Rodriguez, Maria-Jesus Aguilera-Urena et al. (+2 more)
Potable water utilities are currently making great efforts to reduce leakage rates and assure long-term supply to the population due to the challenges of
climate change, growing population and water shortage scenarios that have been on them over the last years. One of the most employed methods to reduce leakage includes the installation of pressurereducing valves along the water distribution network and the utilization of pressure management schemes. Pressure management includes different types of control models, which are applied according to the requirements of each site. The most advanced and sophisticated scheme is critical point control, which relies on a flow signal from a measuring device or online communication between the critical point and the valve. This paper proposes the utilization of a seasonal autoregressive integrated moving average, or the SARIMA model, to correlate pressure at the outlet of the valve and pressure on the critical point of the area supplied, aiming to set a fixed pressure in the critical point. The SARIMA model is developed according to historical data logged in the field and then validated. Later, the SARIMA model was tested on a real location in the village of Noja, Spain. The analysis of the field test results prove that the proposed model is feasible to be used since there is no significance difference between the target values set in the critical point and the real values measured in the field. The research proves that the SARIMA model can be used as an alternative for critical point control in water distribution networks when no flow signal is available or when communication between the critical point and the pressure reducing valve is not an option.
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All authors Andres Ortega-Ballesteros, David Munoz-Rodriguez, Maria-Jesus Aguilera-Urena, Francisco Javier de los Santos-Zarco, Alberto-Jesus Perea-Moreno
Chemical Physics · Cross-listed from astro-ph.EP
A Fast, Parallelized, GPU-Accelerated Photochemical Model, XODIAC, with Built-in Equilibrium Chemistry and Multiple Chemical Networks for Exoplanetary Atmospheres
Priyankush Ghosh, Sambit Mishra, Shubham Dey et al. (+3 more)
The launch of the James Webb Space
Telescope (JWST) has delivered high-quality atmospheric observations and expanded the known chemical inventory of exoplanetary atmospheres, opening new avenues for atmospheric chemistry modeling to interpret these data. Here, we present XODIAC, a fast, GPU-accelerated, one-dimensional photochemical model with a built-in
equilibrium chemistry solver, an updated thermochemical database, and three chemical reaction networks. This framework enables comparative atmospheric chemistry studies, including the newly developed XODIAC-2025 network, a state-of-the-art C-H-O-N-P-S-Metals network, linking 594 species through 7,720 reactions. The other two are existing, publicly available C-H-O-N-S and C-H-O-N-S-Metals networks, from the established photochemical models VULCAN and ARGO, respectively, which are commonly used in the community. The XODIAC model has been rigorously benchmarked on the well-studied hot Jupiter HD 189733 b, with results compared against these two models. Benchmarking shows excellent agreement and demonstrates that, when the same chemical network and initial conditions are used, the numerical scheme for solving atmospheric chemistry does not significantly affect the results. We also revisited the atmospheric chemistry of HD 189733 b and performed a comparative analysis across the three networks. Sulfur chemistry shows the least variation across networks, carbon chemistry shows slightly more, and phosphorus chemistry varies the most, primarily due to the introduction of unique PHO and PN pathways comprising 390 reactions in the XODIAC-2025 network. These findings highlight XODIAC's capability to advance exoplanetary atmospheric chemistry and provide a robust framework for comparative exoplanetology.
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All authors Priyankush Ghosh, Sambit Mishra, Shubham Dey, Debayan Das, Paul B. Rimmer, Liton Majumdar
Medical Physics
Optimal experimental design with k-space data: application to inverse hemodynamics
Miriam Löcke, Ahmed Attia, Dariusz Ucínski et al. (+1 more)
Subject-specific cardiovascular models rely on parameter estimation using measurements such as 4D Flow MRI data. However, acquiring high-resolution, high-fidelity functional flow data is costly and taxing for the patient. As a result, there is growing interest in using highly undersampled MRI data to reduce acquisition time and thus the cost, while maximizing the information gain from the data. Examples of such recent work include inverse problems to estimate boundary conditions of aortic blood flow from highly undersampled k-space data. The undersampled data is selected based on a predefined sampling mask which can significantly influences the performance and the quality of the solution of the inverse problem. While there are many established sampling patterns to collect undersampled data, it remains unclear how to select the best sampling pattern for a given set of inference parameters. In this paper we propose an Optimal Experimental Design (OED) framework for MRI measurements in k-space, aiming to find optimal masks for estimating specific parameters directly from k-space. As OED is typically applied to sensor placement problems in spatial locations, this is, to our knowledge, the first time the technique is used in this context. We demonstrate that the masks optimized by employing OED consistently outperform conventional sampling patterns in terms of parameter estimation accuracy and variance, facilitating a speed-up of 10x of the acquisition time while maintaining accuracy.
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All authors Miriam Löcke, Ahmed Attia, Dariusz Ucínski, Cristóbal Bertoglio
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Learning Thermoelectric Transport from Crystal Structures via Multiscale Graph Neural Network
Yuxuan Zeng, Wei Cao, Yijing Zuo et al. (+7 more)
Graph neural networks (GNNs) are designed to extract latent patterns from graph-structured data, making them particularly well suited for
crystal representation learning. Here, we propose a GNN model tailored for estimating electronic transport coefficients in inorganic thermoelectric
crystals. The model encodes
crystal structures and physicochemical properties in a multiscale manner, encompassing global, atomic, bond, and angular levels. It achieves state-of-the-art performance on
benchmark datasets with remarkable extrapolative capability. By combining the proposed GNN with ab initio calculations, we successfully identify compounds exhibiting outstanding electronic transport properties and further perform interpretability analyses from both global and atomic perspectives, tracing the origins of their distinct transport behaviors. Interestingly, the decision process of the model naturally reveals underlying physical patterns, offering new insights into computer-assisted materials design.
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All authors Yuxuan Zeng, Wei Cao, Yijing Zuo, Fang Lyu, Wenhao Xie, Tan Peng, Yue Hou, Ling Miao, Ziyu Wang, Jing Shi
Physics and Society
Learning-based Link Prediction Methods Integrating Network Topological Features and Embedding Representations
Zi-Xuan Jin, Jun-Fan Yi and Ke-Ke Shang
Link prediction, as a frontier task in complex network
topology analysis, aims to infer the existence of latent links between node pairs based on observed nodes and structural information. We propose an ensemble link prediction model that integrates network
topology features and
embedding representations (TELP), designed to overcome the limitations of conventional heuristic methods in capturing node attributes and deep structural patterns, as well as the weak interpretability and limited generalization of learning-based approaches. TELP leverages a multi-stage architecture. Local connectivity patterns are captured through network-type-aware selection of homogeneous and heterogeneous
topology features, which also promotes interpretability. To incorporate global structure, Node2Vec
embeddings are generated and fused with these
topology features, resulting in comprehensive multi-dimensional representations. Building on this enriched feature space, an ensemble of logistic regression, random forest, and XGBoost models is deployed to maximize predictive performance and robustness. Experiments on nine classical
benchmark networks demonstrate that TELP achieves superior AUC and AP performance compared with traditional heuristic approaches and mainstream graph neural network models, while ablation studies further confirm that feature fusion and ensemble strategies are essential for optimal performance.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Full Electrical Switching of a Freestanding Ferrimagnetic Metal for Energy-Efficient Bipolar Neuromorphic Computing
Li Liu, Peixin Qin, Xiang Wang et al. (+11 more)
Flexible electronics and neuromorphic computing face key challenges in material integration and function retention. In particular, freestanding membranes suffer from slow sacrificial layer removal and interfacial strain, while neuromorphic hardware often relies on area-intensive dual-device schemes for bipolar synaptic weights. Here, we present a universal strategy based on water-soluble Sr4Al2O7 sacrificial layers, enabling the rapid release of freestanding ferrimagnetic metal membranes, which exhibit deterministic
spin-orbit torque switching characteristics with well-preserved perpendicular
magnetic anisotropy and are potential for next-generation ultrafast information technology. Extending this approach, we realize single-device ferrimagnetic synapses exhibiting intrinsic bipolar resistive switching. When implemented in a ResNet-18 architecture, these devices achieve 92% accuracy on CIFAR-10 - comparable to floating-point software models - while halving device counts relative to differential-pair implementations. These results establish a scalable platform linking flexible spintronics with compact, high-performance neuromorphic systems, offering foundational advances for next-generation electronics and
brain-inspired hardware.
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All authors Li Liu, Peixin Qin, Xiang Wang, Xiaobo She, Shaoxuan Zhang, Xiaoning Wang, Hongyu Chen, Guojian Zhao, Zhiyuan Duan, Ziang Meng, Qinghua Zhang, Qiong Wu, Yu Liu, Zhiqi Liu
Atmospheric and Oceanic Physics
How do cold pools influence the size of tropical cyclone embryos?
Hao Fu
The size of tropical cyclone (TC) embryos is an essential predictor of TC genesis. Recent studies have identified cold pools and planetary rotation as factors that increase and decrease TC embryo size. While the planetary rotation effect has been depicted using a quasi-geostrophic (QG) model, the cold pool effect still lacks a theoretical model. This paper presents a cloud chain model to derive the length scale regarding the influence of cold pools on the TC embryo
vortex. Within the model, the amount of rain evaporation during a single convective event determines the wind speed and humidity at the cold pool edge, influencing the amount of sub-cloud moisture convergence for the next-generation convection and, therefore, the intensity of the next-generation cold pool. A perturbation analysis shows that cold pools exhibit a nonlocal dependence on air-column humidity, with the influence range determined by the cold pool size and a convective
memory weight. The
memory weight relies on the sum of the contributions of mechanical lifting and thermodynamic forcing to convective initiation. A crucial parameter is the ratio of rain evaporation to surface evaporation in a cold pool. By coupling the cloud chain model with the QG equation, an analytical expression for the TC embryo size is obtained. The theory captures the trend but overestimates the TC embryo size in cloud-permitting simulations. The deviation might be due to the oversimplification in estimating the fractional contribution of cold pools to convective initiation.
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Optics
Phase-multiplexed optical computing: Reconfiguring a multi-task diffractive optical processor using illumination phase diversity
Xiao Wang and Aydogan Ozcan
We report a monochrome multi-task diffractive network architecture that leverages illumination phase multiplexing to dynamically reconfigure its output function and accurately implement a large group of complex-valued linear transformations between an input and output aperture. Each member of the desired group of T unique transformations is encoded and addressed with a distinct 2D illumination phase profile, termed "phase key", which illuminates the input aperture, activating the corresponding transformation at the output field-of-view. A common diffractive optical network, optimized with T phase keys, demultiplexes these encoded inputs and accurately executes any of the T distinct linear transformations at its output. We demonstrate that a diffractive network composed of N = 2 x T x Ni x No optimized diffractive features can realize T distinct complex-valued linear transformations, accurately executed for any complex field at the input aperture, where Ni and No refer to the input/output pixels, respectively. In our proof-of-concept numerical analysis, T = 512 complex-valued transformations are implemented by the same monochrome diffractive network with negligible error using illumination phase diversity. Compared with wavelength-multiplexed diffractive systems, phase-multiplexing architecture significantly lowers the transformation errors, potentially enabling larger-scale optical transformations to be implemented through a monochrome processor. Phase-multiplexed multi-task diffractive networks would enhance the capabilities of optical computing and machine-
vision systems.
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Accelerator Physics
A Capacitor Model of the Helical Deflector: Revisiting Shamaev's Proposal and the Textbook Model
Hayk L. Gevorgyan
An RF helical deflector is a type of electron and ion optics device that applies a time-dependent rotating transverse electric or
magnetic field by means of sinusoidal RF voltage applied on two opposite conducting helical structures (wires, ribbons or other) to deflect a charged-particle beam into an elliptical trajectory, a bunch into a partial elliptical arc, and a single particle to a point on the ellipse. It is a perspective indirect timing system being concurrent for reaching picosecond time resolution, and have promise being excellent candidate for high precision time-of-flight detection. As a timing system, it converts the temporal structure, i.e., the arrival time trajectory of an electron beam into a spatial pattern — particularly, an ellipse in the case of a single-frequency RF voltage and continuous electron pencil beam. I propose a capacitor model of an RF helical deflector and compare it with the existing textbook model [1,2], interpret them and provide understanding of them. Furthermore, I analyze the latter, finding analytical formulas for the applied electric field, ellipse sizes (semi-axes) and rotation angle, lengths of the ellipse line, corresponding to the duration of electron pencil bunches or beams. The present article touches the topics of getting circle on resonance limit, of deflection sensitivity and of time measurement using RMS or average arc lengths.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Freestanding Thin-Film Materials
Li Liu, Peixin Qin, Guojian Zhao et al. (+7 more)
Freestanding thin films, a class of low-dimensional materials capable of maintaining structural integrity without substrates, have emerged as a forefront research focus. Their unique advantages-circumventing substrate clamping, liberating intrinsic material properties, and enabling cross-platform heterogeneous integration-underpin this prominence. This review systematically summarizes core fabrication techniques, including physical delamination (e.g.,
laser lift-off, mechanical exfoliation) and chemical etching, alongside associated transfer strategies. It further explores the induced strain modulation mechanisms, extreme mechanical properties and interface decoupling effects enabled by these films. Representative case studies demonstrate breakthrough applications in flexible/ultrathin electronics, ultrahigh-sensitivity sensors and the exploration of novel
quantum states. Critical challenges regarding scalable fabrication, precise interface control, and long-term stability are analyzed, concluding with prospects for emerging applications in bio-inspired intelligent devices,
quantum precision sensing, and
brain-inspired neural networks.
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All authors Li Liu, Peixin Qin, Guojian Zhao, Zhiyuan Duan, Jingyu Li, Sixu Jiang, Xiaoyang Tan, Xiaoning Wang, Ziang Meng, Zhiqi Liu
Optics
Wide field-of-view and large depth-of-field metalenses
Louis Martin-Monier, Zhaoyi Li, Fan Yang et al. (+5 more)
The ability to visualize both macroscopic and microscopic features over an extended field of view is essential for endoscopic imaging and other applications ranging from machine
vision to microscopy. However, miniaturizing endoscopes introduces inherent trade-offs between size and optical performance, including field-of-view (FOV), depth-of-field (DOF), and resolution. These constraints limit the use of microendoscopes in clinical settings such as early cancer detection within narrow, hard-to-access anatomical regions, including the lung, ovaries, and pancreas. State-of-the-art microendoscopes typically rely on microlens assemblies that increase both cost and size. Their large f-numbers also hinder the collection of high-resolution information from live tissue. In this work, we present two compact metalens designs that provide wide FOV, extended DOF, and high resolution, enabled by custom-tailored point spread functions (PSFs). The devices achieve a full 172 degrees FOV, an extended DOF from 0.4 mm to beyond 300 mm, and a resolution of 30 line pairs per millimeter, all within a 1 mm x 1 mm x 0.2 mm footprint. A key advantage of our approach is the ability to transition seamlessly between low and high magnification without mechanical refocusing. Final images are reconstructed through backend deconvolution, highlighting the potential of hybrid imaging systems that integrate computational techniques with flat-optics components.
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All authors Louis Martin-Monier, Zhaoyi Li, Fan Yang, Mikhail Shalaginov, Luigi Ranno, Jia Xu Brian Sia, Tian Gu, Juejun Hu
Fluid Dynamics
Half-explicit Runge-Kutta integrators for variational multiscale turbulence modeling: Toward higher-order accuracy in space and time
Yujie Sun, Chi Ding and Ju Liu
The residual-based variational multiscale (VMS) formulation has achieved remarkable success in large-eddy simulation of turbulent flows. However, its temporal discretization has largely remained limited to second-order implicit schemes. The present work aims at advancing this direction through the introduction of Runge-Kutta (RK) schemes within the VMS framework in a mathematically consistent manner. Guided by the Rothe method, the half-explicit RK scheme is employed as its accuracy is theoretically guaranteed for index-2 differential-algebraic equations. Owing to the explicit treatment of the nonlinear term, the resulting spatial problem exhibits a structure analogous to that of the Darcy equation. Following the philosophy of the VMS analysis, a subgrid-scale model is derived without invoking linearization based on perturbation series and related assumptions. The analysis further reveals that the parameter in the subgrid model is independent of the spatial mesh size.
Fourier analysis demonstrates that the Rothe method, compared with the conventional vertical method of lines, provides improved dissipation and dispersion properties and exhibits a larger stability region for convection-dominated regimes. In the Taylor-Green
vortex benchmark, the proposed schemes demonstrate superior performance as a large-eddy simulation model, achieving higher fidelity in predicting the kinetic energy
evolution, energy spectra, and
vortex structures than the conventional VMS formulation. Simulations of the open cavity flow further show that the proposed schemes can accurately capture the periodic limit cycle caused by the supercritical
Hopf bifurcation, confirming its effectiveness and fidelity for highly sensitive flow instability problems.
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