Showing 1–50 of 197 results for author: Dong, C

Excitation of the lower-hybrid drift instability in the outflow of electron-only magnetic reconnection

Authors: B. K. Russell, K. Sakai, Y. Zhang, L. Gao, E. G. Blackman, W. Daughton, C. Dong, J. Katz, S. R. Klein, C. C. Kuranz, X. Li, X. M. Li, A. L. Milder, J. Ng, K. Orr, G. Pomraning, J. P. Schell, A. Stanier, J. Yoo, H. Ji

Abstract: We report experimental evidence for the lower-hybrid drift instability in the current sheet normal direction of electron-only magnetic reconnection. In our laser-driven capacitor-coil experiment, the system size ($\sim$3 ion skin depths) places it in the electron-only regime. Yet, Thomson scattering reveals out-of-plane electron drift oscillations at the local lower-hybrid frequency, with kinetic… ▽ More We report experimental evidence for the lower-hybrid drift instability in the current sheet normal direction of electron-only magnetic reconnection. In our laser-driven capacitor-coil experiment, the system size ($\sim$3 ion skin depths) places it in the electron-only regime. Yet, Thomson scattering reveals out-of-plane electron drift oscillations at the local lower-hybrid frequency, with kinetic energy density reaching $\sim$18% of the local magnetic energy density. Linear theory with the measured parameters predicts more than ten e-folding times of growth, indicating that the instability reaches the nonlinear regime within the measurement window. Supported by particle-in-cell simulations, these results demonstrate the importance of ions in the dissipation and energy transfer in electron-only reconnection where their significance has not been previously recognized. △ Less

Submitted 20 August, 2026; originally announced August 2026.

Comments: 8 pages, 4 figures

Control of Magnetic Reconnection in High Energy Density Plasmas

Authors: J. L. Latham, B. K. Russell, C. Dong, C. A. Walsh, K. G. Miller, P. T. Campbell, L. Willingale, P. Nilson, K. Krushelnick

Abstract: Magnetic reconnection governs the explosive release of magnetic energy in systems from the solar corona to fusion plasmas, yet controlling it in the laboratory has remained out of reach. Here we demonstrate active control of reconnection in high-power laser-driven plasmas using a third, relativistic-intensity laser pulse that injects filaments of electron current into the reconnecting system. Two… ▽ More Magnetic reconnection governs the explosive release of magnetic energy in systems from the solar corona to fusion plasmas, yet controlling it in the laboratory has remained out of reach. Here we demonstrate active control of reconnection in high-power laser-driven plasmas using a third, relativistic-intensity laser pulse that injects filaments of electron current into the reconnecting system. Two moderate-intensity lasers drive colliding magnetized plumes that reconnect, forming plasmoids in the current sheet as seen in proton deflectometry. The relativistic laser generates magnetic fields matching the polarity on either side of the layer, and, depending on its arrival time, either accelerates the breakup of the current sheet or suppresses reconnection. Arriving early, before the plumes strongly interact, it builds a pocket of magnetic pressure that repels them via flux pileup; arriving after the current sheet forms, it accelerates electrons that extend current filamentation instabilities into the upstream, causing rapid dissipation of the reconnecting magnetic field. This approach opens a route to steering magnetic energy flow in fusion plasmas and broadens the range of systems accessible to laboratory astrophysics. △ Less

Submitted 18 August, 2026; originally announced August 2026.

Comments: 23 pages, 6 figures

The FLARE Facility

Authors: Hantao Ji, Jongsoo Yoo, Peiyun Shi, Euichan Jung, Kush Maheshwari, Adam Robbins, Sunghyun Son, Adam Stanier, Yang Ren, Sayak Bose, Dylan Corl, Keith Corrigan, Robert Cutler, William Daughton, Robert Ellis, Geoffrey Gettelfinger, Ronald Hatcher, Philip Heitzenroeder, Frank Hoffmann, Jonathan Jara-Almonte, Michael Kalish, Thomas Kozub, Enrique Merino, Weiguo Que, Benjamin Smith , et al. (31 additional authors not shown)

Abstract: The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly… ▽ More The Facility for Laboratory Reconnection Experiments (FLARE) has been constructed to study magnetic reconnection in multiple X-line regimes relevant to space, astrophysical, and fusion plasmas. Building upon the successful design of the Magnetic Reconnection Experiment (MRX), FLARE features a larger physical volume, stronger magnetic fields, and an independent ohmic heating drive to significantly extend the accessible parameter space, targeting Lundquist numbers up to S ~ 10^5 and normalized system sizes up to λ~ 10^3. This paper details the facility's core engineering components, including the primary vacuum vessel, internal flux cores, highly segmented external coil systems, modular capacitor banks, and the safety interlock and control architecture. An initial diagnostic suite is presented, comprising high-resolution 2D magnetic probe arrays, triple Langmuir probes, a fully fiber-coupled interferometer, ion Doppler spectroscopy, and fast camera imaging. Initial operations demonstrate the device's experimental flexibility and reliability, successfully executing symmetric push-pull reconnection, spheromak merging, and asymmetric downstream configurations. Currently operating within "Stage 2.5" with S ~ 2,500 and λ~ 60 for anti-parallel reconnection, FLARE provides immediate access to the multiple X-line regimes. Planned hardware upgrades, advanced diagnostic additions, and integration with fully kinetic simulations will further expand its capabilities as it transitions into a collaborative user facility for the broader plasma science community. △ Less

Submitted 17 August, 2026; originally announced August 2026.

Comments: 47 pages, 25 figures, 7 tables

Simultaneous Mars-orbit observations reveal Kelvin-Helmholtz instability-driven bulk atmospheric ion escape

Authors: Chi Zhang, Chuanfei Dong, Gangkai Poh, Jasper Halekas, Xuanye Ma, Ruhunusiri Suranga, Kathleen G. Hanley, Han-Wen Shen, Hongyang Zhou, Xinmin Li, Liang Wang, Jiawei Gao, Shannon Curry, Christian Mazelle

Abstract: Atmospheric ion escape driven by the solar wind is a key process controlling the long-term loss of the Martian atmosphere. Localized plasma clouds can carry substantial fluxes of planetary ions away from Mars, representing episodes of bulk escape. However, their origin has remained unclear due to the absence of simultaneous upstream measurements. Using joint observations from the MAVEN and Tianwen… ▽ More Atmospheric ion escape driven by the solar wind is a key process controlling the long-term loss of the Martian atmosphere. Localized plasma clouds can carry substantial fluxes of planetary ions away from Mars, representing episodes of bulk escape. However, their origin has remained unclear due to the absence of simultaneous upstream measurements. Using joint observations from the MAVEN and Tianwen-1 missions, which provide real-time upstream monitoring, we present direct evidence that these plasma clouds are nonlinear wave packets generated by the Kelvin-Helmholtz instability (KHI). The spatial scale of KH waves is constrained for the first time via two-point measurements. Ion fluxes within plasma clouds are one to two orders of magnitude higher than those in typical steady-state escape channels. Our results indicate that KHI is an important process for solar wind coupling to planetary upper atmospheres and plays a crucial role in shaping atmospheric ion escape for unmagnetized planets. △ Less

Submitted 4 August, 2026; originally announced August 2026.

Final assessment of radioactive impurities in the JUNO detector

Authors: Thomas Adam, Fengpeng An, Costas Andreopoulos, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, João Pedro Athayde Marcondes de André, Didier Auguste, Nikita Balashov, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Beretta, Antonio Bergnoli, Nikita Bessonov, Daniel Bick, Lukas Bieger, Svetlana Biktemerova, Thilo Birkenfeld, Simon Blyth, Manuel Böhles, Anastasia Bolshakova, Mathieu Bongrand, Matteo Borghesi , et al. (549 additional authors not shown)

Abstract: The Jiangmen Underground Neutrino Observatory (JUNO) collaboration has completed the construction of the 20,000-ton liquid scintillator detector and the associated muon veto detector system. To meet the physics objectives, the materials used in the detector must exhibit low radioactive contamination. The single-event rate in the fiducial volume (R $<$ 17.2 m) of the scintillator is required to be… ▽ More The Jiangmen Underground Neutrino Observatory (JUNO) collaboration has completed the construction of the 20,000-ton liquid scintillator detector and the associated muon veto detector system. To meet the physics objectives, the materials used in the detector must exhibit low radioactive contamination. The single-event rate in the fiducial volume (R $<$ 17.2 m) of the scintillator is required to be approximately 7 Hz for energies above 0.7 MeV, resulting in an accidental coincidence background of about 1 event per day for reactor neutrino physics analyses. Since the beginning of the construction phase, we have screened the natural radioactivity content of thousands of materials, to select those that meet the design background budget. The radioactive impurity concentrations of the materials ultimately used in the JUNO detector are summarized in this paper. The construction of the entire detector and the subsequent filling of the liquid scintillator were completed in August 2025. From the initial data, the total count rate of natural radioactivity within the detector's fiducial volume has met the requirements and is sufficient to support the reactor antineutrino analysis. △ Less

Submitted 19 July, 2026; originally announced July 2026.

Plasma Flow Generation and Particle Acceleration from Expanding Magnetic Bubbles

Authors: Yang Zhang, Brandon K. Russell, Geoffrey Pomraning, Lan Gao, Xiaocan Li, Adam Stainer, William Daughton, Chuanfei Dong, Liang Wang, Peiyun Shi, Kian Orr, Hantao Ji

Abstract: Impulsive plasma dynamics in the laboratory are often driven by rising electric currents, yet their quantitative plasma response has not been well established. By means of fully kinetic particle-in-cell simulations and laser-driven capacitor-coil experiments, we show that a rising current expels plasma, forming an expanding magnetic bubble and accelerating particles. The expansion front velocity s… ▽ More Impulsive plasma dynamics in the laboratory are often driven by rising electric currents, yet their quantitative plasma response has not been well established. By means of fully kinetic particle-in-cell simulations and laser-driven capacitor-coil experiments, we show that a rising current expels plasma, forming an expanding magnetic bubble and accelerating particles. The expansion front velocity scales with the Alfvén speed determined by the magnetic field at its inner edge and the plasma density at its outer edge. This mechanism establishes impulsive current drive as a fundamental way that generates plasma flows and accelerates particles in laboratory plasmas, with potential relevance to astrophysics. △ Less

Submitted 19 June, 2026; originally announced June 2026.

Journal ref: Phys. Rev. Research 8, 023317 (2026)

Doppler-shifted X-ray Spectroscopy of Nonradiative Electron Capture in Relativistic Collisions of Xe54+ Ions with Kr and Xe Atoms

Authors: Bian Yang, Deyang Yu, Konstantin N. Lyashchenko, Caojie Shao, Zhongwen Wu, Mingwu Zhang, Oleg Yu. Andreev, Junliang Liu, Zhangyong Song, Yingli Xue, Wei Wang, Fangfang Ruan, Yehong Wu, Rongchun Lu, Chenzhong Dong, Xiaohong Cai

Abstract: We present an angular-resolved Doppler spectroscopy study of nonradiative electron capture in relativistic collisions of bare Xe54+ ions with Kr and Xe gas targets at the HIRFL-CSR storage ring. The energy spectra and angular distributions of X-rays emitted from fast-moving down-charged projectiles were measured at five observation angles of 35°, 60°, 90°, 120°, and 145° and three collision energi… ▽ More We present an angular-resolved Doppler spectroscopy study of nonradiative electron capture in relativistic collisions of bare Xe54+ ions with Kr and Xe gas targets at the HIRFL-CSR storage ring. The energy spectra and angular distributions of X-rays emitted from fast-moving down-charged projectiles were measured at five observation angles of 35°, 60°, 90°, 120°, and 145° and three collision energies of 95, 146, and 197 MeV/u by employing the effect of Doppler shift. The transition intensities of Xe53+ ions with small energy differences were precisely determined. In symmetric Xe54+ \to Xe collisions, the transition intensities of Xe53+ and Xe52+ ions were identified when X-rays emitted by projectiles overlapped with K X-rays arising from target ionization. The anisotropy parameters of the K{α_1}(+M2) transition were derived from the angular emission patterns of the corresponding spectral lines. The relative populations of the L, M, and N-shell excited levels of Xe53+ and Xe52+ were further deduced from the intensity ratios of I(Ly-β)/I(Ly-α), I(Ly-γ)/I(Ly-α), and I(Kα)/I(Ly-α). The energy dependence of the population of excited projectile levels was obtained for both targets. Furthermore, the experimental results were compared with theoretical calculations of nonradiative single- and double-electron capture based on the relativistic eikonal approximation and the independent-electron approximation. These findings provide valuable insights into the magnetic-sublevel population and n-resolved state-selective population of excited states produced in relativistic collisions of highly charged heavy ions with multi-electron atoms. △ Less

Submitted 14 June, 2026; originally announced June 2026.

Direct Observations of Magnetic Reconnection in the Solar Wind Current Sheets near Mars

Authors: Chi Zhang, Chuanfei Dong, Xinmin Li, Han-Wen Shen, Jasper Halekas, Tai Phan, Christian Mazelle, Yuki Harada, Hongyang Zhou, Jiawei Gao, Liang Wang, Shannon Curry, David L. Mitchell

Abstract: Magnetic reconnection is a fundamental and ubiquitous process in astrophysical plasmas that converts magnetic energy into plasma kinetic and thermal energy. Throughout the heliosphere, the solar wind is permeated with current sheets (CSs), providing a natural laboratory for investigating this process. Using measurements from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we repo… ▽ More Magnetic reconnection is a fundamental and ubiquitous process in astrophysical plasmas that converts magnetic energy into plasma kinetic and thermal energy. Throughout the heliosphere, the solar wind is permeated with current sheets (CSs), providing a natural laboratory for investigating this process. Using measurements from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we report the first direct observations of magnetic reconnection occurring within the solar wind CSs near Mars. Specifically, MAVEN observed the classic Petschek-type reconnection exhaust regions, evidenced by bifurcated magnetic field signatures and Alfvenic ion outflows. Notably, the observed exhaust region appears to be large-scale, significantly exceeding the typical thickness of solar wind CSs near Mars. This suggests that magnetic reconnection may significantly broaden the CS. Our results underscore the ubiquity of magnetic reconnection across heliocentric distances and may provide new insights into the large-scale evolution of the solar wind and the development of turbulence within it. △ Less

Submitted 14 June, 2026; originally announced June 2026.

Journal ref: The Astrophysical Journal Letters, Vol. 1004, L45 (2026)

Precipitation diffusion downscaling and application to out-of-distribution simulations with and without stratospheric aerosol injection

Authors: Cameron Dong, James W. Hurrell, Elizabeth A. Barnes

Abstract: Stratospheric aerosol injection (SAI), a possible climate engineering strategy where reflective particles are injected into the stratosphere, has been explored to mitigate global warming and its associated risks, such as the intensification of extreme precipitation events. However, current Earth system models (ESMs) often used to simulate SAI and other climate change scenarios are too coarse to pr… ▽ More Stratospheric aerosol injection (SAI), a possible climate engineering strategy where reflective particles are injected into the stratosphere, has been explored to mitigate global warming and its associated risks, such as the intensification of extreme precipitation events. However, current Earth system models (ESMs) often used to simulate SAI and other climate change scenarios are too coarse to properly assess such risks. Traditional statistical downscaling methods, used to project higher resolution impacts, may be biased and unrealistic. To address this, we train a deep learning diffusion downscaler to generate 0.25° contiguous United States (CONUS) daily precipitation using historical and future climate simulations from the Mesoscale Atmosphere-Ocean Interaction in Seasonal-to-Decadal Climate Prediction (MESACLIP) project, then apply the diffusion downscaler to out-of-distribution CESM2 simulations with and without SAI. The diffusion model generates realistic downscaled precipitation using either MESACLIP or CESM2 inputs. It also faithfully recreates the climate change projections of extreme precipitation in MESACLIP. Diffusion-downscaled projections of the future CESM2 SAI scenarios suggest that SAI could nearly cut in half the CONUS-average increase in yearly max precipitation, compared to the non-SAI scenario. However, there is considerable regional variation and internal variability, with SAI modeled to only slightly reduce increases in extreme precipitation frequency in the Mid Atlantic and the Pacific Northwest, but mitigating most intensification in other regions. Future application of diffusion downscaling to a wider variety of SAI scenarios would provide valuable insight into how proposed SAI strategies may affect precipitation variability on fine spatial scales for regional impact assessments. △ Less

Submitted 22 May, 2026; originally announced May 2026.

Ultra-Confinement of Polaritons in Single Atomic Layer Ag Photonic Quantum Dots

Authors: Xinyi Li, Tetyana Ignatova, Chengye Dong, Krishnan Mekkanamkulam Ananthanarayanan, Rinu Abraham Maniyara, Arpit Jain, Furkan Turker, Vinay Kammarchedu, Aida Ebrahimi, Joshua A. Robinson, Slava V. Rotkin

Abstract: Light scattering by two-dimensional (2D) van der Waals heterostructures (vdWHs) is immense, especially given their infinitesimal volume, thus enabling strong light-matter interactions. Surface 2D polariton waves manifest through large concentration of electromagnetic field in vertical direction, normal to their propagation. By confining vdWH materials into 2D photonic shapes, one can manipulate an… ▽ More Light scattering by two-dimensional (2D) van der Waals heterostructures (vdWHs) is immense, especially given their infinitesimal volume, thus enabling strong light-matter interactions. Surface 2D polariton waves manifest through large concentration of electromagnetic field in vertical direction, normal to their propagation. By confining vdWH materials into 2D photonic shapes, one can manipulate and compress light in lateral directions. Scattering-type scanning near-field optical microscopy is a perfect tool for direct imaging of the propagating polaritons and studying the properties of confined polaritons in nanostructures. Though, thus far the quantitative analysis, such the wavelength extraction, has been challenged for confined polaritons by incapability of mapping of the wave period on sub-wavelength scale and difficulty of identifying an adequate substrate's "background" to subtract. Here, an analytical approach is developed to reveal the local propagation constant of confined polaritons under abovementioned constraints and map it with the sub-wavelength resolution. Applied to analysis of the SiC/2D-Ag/EG (epitaxial graphene) photonic nanostructures, the technique uncovered that the polaritons are highly confined in both vertical ($\simλ$/50) and lateral directions ($\simλ$/40) by 2D metal. △ Less

Submitted 20 May, 2026; originally announced May 2026.

State-resolved electron capture in low-energy Ar2+-Ar/N2 collisions

Authors: Shucheng Cui, Dadi Xing, Xiaolong Zhu, Dongmei Zhao, Dalong Guo, Yong Gao, Shaofeng Zhang, Chenzhong Dong, Xinwen Ma

Abstract: As a fundamental process in atomic physics, charge exchange relies on quantum state-resolved data that is crucial for various fields such as astrophysics and plasma physics. However, there remains a g in the research on multi-electron target systems. This study aims to investigate the dynamic mechanisms of single/double electron capture in collisions between Ar2+ ions and Ar atoms or N2 molecules… ▽ More As a fundamental process in atomic physics, charge exchange relies on quantum state-resolved data that is crucial for various fields such as astrophysics and plasma physics. However, there remains a g in the research on multi-electron target systems. This study aims to investigate the dynamic mechanisms of single/double electron capture in collisions between Ar2+ ions and Ar atoms or N2 molecules at an energy of 40 keV, thereby supplementing high-precision experimental data in this field. The experiment is conducted on the electron beam ion source (EBIS) platform at the Institute of Modern Physics, Chinese Academy of Sciences, using the cold target recoil ion momentum spectroscopy (COLTRIMS) technique. An ion beam containing ground-state Ar2+ (3s^2 3p^(4 3) P) and metastable Ar2+ (3s^2 3p^(4 1) D,(_^1)S) is used as the projectile, colliding with a supersonic Ar/ N2 mixed gas target. Three-dimensional momentum of recoil ions is reconstructed through coincidence measurements of recoil ions and scattered ions, and the Q-value and scattering angle distribution are calculated. Theoretical comparisons are performed using the molecular Coulombic over barrier model (MCBM). △ Less

Submitted 7 May, 2026; originally announced May 2026.

Journal ref: Acta Phys. Sin. 2025, 74(24):240702

Embedded underwater front-end electronics for the 3-inch photomultipliers in the JUNO experiment

Authors: Cédric Cerna, Miao He, Xiaoshan Jiang, Juan Pedro Ochoa-Ricoux, Frédéric Perrot, Angel Abusleme, Thomas Adam, Fengpeng An, Costas Andreopoulos, Giuseppe Andronico, João Pedro Athayde Marcondes de André, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Didier Auguste, Nikita Balashov, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Beretta, Antonio Bergnoli, Nikita Bessonov, Daniel Bick, Lukas Bieger, Svetlana Biktemerova , et al. (576 additional authors not shown)

Abstract: The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator-based, low-radioactivity, multi-purpose neutrino detector located 693 meters (1800 m.w.e.) underground in the Guangdong province, China. To detect scintillation light produced in the target, the detector is equipped with 17,612 20-inch photomultipliers (PMTs), forming the Large PMT system (LPMT). In addition, 25,… ▽ More The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator-based, low-radioactivity, multi-purpose neutrino detector located 693 meters (1800 m.w.e.) underground in the Guangdong province, China. To detect scintillation light produced in the target, the detector is equipped with 17,612 20-inch photomultipliers (PMTs), forming the Large PMT system (LPMT). In addition, 25,600 3-inch photomultipliers (the Small Photomultiplier System or SPMT) are deployed in the gaps between the LPMTs. This paper presents the design and performance of the underwater front-end electronics developed for the SPMT system. It details the individual electronics boards and their key components, the inter-board interfaces, the system-level design, and the firmware architecture that supports data acquisition and control. It also outlines mechanical and thermal integration, board validation procedures, and system performance metrics. The readout chain includes digitization of 128 PMT channels per unit, synchronized time-stamping, charge measurement, event packaging, and bandwidth management. Comprehensive validation confirms the system's readiness to meet JUNO's stringent physics goals. The underwater electronics achieve noise levels as low as 0.04 photoelectrons with minimal crosstalk (below 0.4%) and a bandwidth of 57 MB/s, ensuring reliable single photo-electron detection and operation under high-rate conditions. The SPMT system has now been fully integrated and installed in JUNO. Its commissioning and physics performance will be reported in a future publication. △ Less

Submitted 1 June, 2026; v1 submitted 28 April, 2026; originally announced April 2026.

Comments: Submitted to Nucl. Instrum. Methods Phys. Res. A

Properties and Radial Evolution of Solar Wind Turbulence Near Mercury's Orbit

Authors: Xinmin Li, Chuanfei Dong, Lina Z. Hadid, Sae Aizawa, Chi Zhang, Hongyang Zhou, Liang Wang, Jiawei Gao, James A. Slavin

Abstract: We present a comprehensive statistical study of the radial evolution of solar wind turbulence near Mercury's orbit using long-term magnetic field measurements from the MESSENGER mission. Owing to Mercury's highly elliptical orbit and the spacecraft's repeated, extended residence in the upstream solar wind, the data set provides more than 17,000 hours of observations, enabling robust statistics acr… ▽ More We present a comprehensive statistical study of the radial evolution of solar wind turbulence near Mercury's orbit using long-term magnetic field measurements from the MESSENGER mission. Owing to Mercury's highly elliptical orbit and the spacecraft's repeated, extended residence in the upstream solar wind, the data set provides more than 17,000 hours of observations, enabling robust statistics across well-defined heliocentric distance intervals (0.31-0.47 au). We find that inertial-range spectral slopes remain close to -3/2 throughout Mercury's orbit, showing no significant radial evolution. Combined with low magnetic compressibility, this result indicates a stable, predominantly Alfvenic inertial-range cascade already established here. In contrast, kinetic-range spectral slopes exhibit clear radial evolution, becoming progressively shallower with increasing heliocentric distance, highlighting the greater sensitivity of kinetic-scale turbulence to heliocentric conditions. The ion-scale spectral break frequency decreases with distance in the spacecraft frame, while its normalized form increases relative to the local proton cyclotron frequency, demonstrating that the break is not tied to proton cyclotron frequency but reflects evolving local plasma conditions. Magnetic compressibility shows a similar frequency dependence at all distances, with a subtle radial enhancement of compressive fluctuations at kinetic scales. Autocorrelation analysis reveals strong anisotropy, with the correlation times of field-aligned magnetic fluctuations increasing with heliocentric distance, while those of perpendicular fluctuations remain shorter and nearly invariant. Together, these results demonstrate a clear scale-dependent radial evolution of solar wind turbulence near Mercury-s orbit, providing new constraints on the development of kinetic processes in the inner heliosphere. △ Less

Submitted 23 June, 2026; v1 submitted 22 April, 2026; originally announced April 2026.

Journal ref: The Astrophysical Journal Letters, Vol. 1005, L1 (2026)

Automated Classification of Plasma Regions at Mars Using Machine Learning

Authors: Yilan Qin, Chuanfei Dong, Hongyang Zhou, Chi Zhang, Kaichun Xu, Jiawei Gao, Simin Shekarpaz, Xinmin Li, Liang Wang

Abstract: The plasma environment around Mars is highly variable because it is strongly influenced by the solar wind. Accurate identification of plasma regions around Mars is important for the community studying solar wind-Mars interactions, region-specific plasma processes, and atmospheric escape. In this study, we develop a machine-learning-based classifier to automatically identify three key plasma region… ▽ More The plasma environment around Mars is highly variable because it is strongly influenced by the solar wind. Accurate identification of plasma regions around Mars is important for the community studying solar wind-Mars interactions, region-specific plasma processes, and atmospheric escape. In this study, we develop a machine-learning-based classifier to automatically identify three key plasma regions--solar wind, magnetosheath, and induced magnetosphere--using only ion omnidirectional energy spectra measured by the MAVEN Solar Wind Ion Analyzer (SWIA). Two neural network architectures are evaluated: a multilayer perceptron (MLP) and a convolutional neural network (CNN) that incorporates short temporal sequences. Our results show that the CNN can reliably distinguish the three plasma regions, whereas the MLP struggles to separate the solar wind and magnetosheath. Therefore, the CNN-based approach provides an efficient and accurate framework for large-scale plasma region identification at Mars and can be readily applied to future planetary missions. △ Less

Submitted 18 April, 2026; originally announced April 2026.

Comments: 14 pages, 4 figures

Physics-Informed Neural Operator for Electromagnetic Inverse Scattering Problems

Authors: Q. C. Dong, Zi-Xuan Su, Qing Huo Liu, Wen Chen, Zhizhang, Chen

Abstract: This paper proposes a physics-informed neural operator (PINO) framework for solving inverse scattering problems, enabling rapid and accurate reconstructions under diverse measurement conditions. In the proposed approach, the dielectric property is represented as a learnable tensor, while a neural operator is employed to predict the induced current distribution. A hybrid loss function, consisting o… ▽ More This paper proposes a physics-informed neural operator (PINO) framework for solving inverse scattering problems, enabling rapid and accurate reconstructions under diverse measurement conditions. In the proposed approach, the dielectric property is represented as a learnable tensor, while a neural operator is employed to predict the induced current distribution. A hybrid loss function, consisting of the state loss, data loss and total-variation (TV) regularization, is constructed to establish a fully differentiable formulation for a joint optimization of network parameters and dielectric property. To demonstrate the framework's generality and flexibility, PINO is implemented using three representative neural operators, i.e., the Fourier Neural Operator (FNO), the enhanced Fourier Neural Operator (U-FNO) and the Factorized Fourier Neural Operator (F-FNO). Compared with conventional approaches, the proposed framework offers a simpler formulation and universal modeling capability, making it readily applicable to various measurement scenarios, including multi-frequency and phaseless inversion. Numerical simulations demonstrate that the proposed PINO achieves high accuracy and robust reconstruction across samples with and without phase information, under single-frequency and multi-frequency settings in the presence of noise. The results demonstrate that PINO consistently outperforms conventional contrast-source inversion (CSI) methods and provides an efficient, unified solution to complex electromagnetic inverse-scattering problems. △ Less

Submitted 26 March, 2026; originally announced March 2026.

Hierarchy of extreme-event predictability in turbulence revealed by machine learning

Authors: Yuxuan Yang, Chenyu Dong, Gianmarco Mengaldo

Abstract: Extreme-event predictability in turbulence is strongly state dependent, yet event-by-event predictability horizons are difficult to quantify without access to governing equations or costly perturbation ensembles. Here we train an autoregressive conditional diffusion model on direct numerical simulations of the two-dimensional Kolmogorov flow and use a CRPS-based skill score to define an event-wise… ▽ More Extreme-event predictability in turbulence is strongly state dependent, yet event-by-event predictability horizons are difficult to quantify without access to governing equations or costly perturbation ensembles. Here we train an autoregressive conditional diffusion model on direct numerical simulations of the two-dimensional Kolmogorov flow and use a CRPS-based skill score to define an event-wise predictability horizon. Enstrophy extremes exhibit a pronounced hierarchy: forecast skill persists from $\approx 1$ to $> 4$ Lyapunov times across events. Spectral filtering shows that these horizons are controlled predominantly by large-scale structures. Extremes are preceded by intense strain cores organizing quadrupolar vortex packets, whose lifetime sharply separates long- from short-horizon events. These results identify coherent-structure persistence as a governing mechanism for the predictability of turbulence extremes and provide a data-driven route to diagnose predictability limits from observations. △ Less

Submitted 14 March, 2026; originally announced March 2026.

Nonlinear Nanophotonic Chip-space Interfaces: On-chip Generation of Structured, Topological and Spatiotemporal Lights Via Nonlinear Čerenkov Radiation

Authors: Dunzhao Wei, Bo Chen, Shuai Wan, Yixuan Wang, Jiantao Ma, Pi-Yu Wang, Chun Chang, Guixin Qiu, Zelin Tan, Xiaoshan Huang, Yan Chen, Tian Jiang, Qiwen Zhan, Fang Bo, Songnian Fu, Xuehua Wang, Chun-hua Dong, Jin Liu

Abstract: Miniaturized and reconfigurable interfaces between confined optical modes within integrated photonic chips and structured light propagating in free space would serve as a cornerstone for fundamental optical science and modern photonic technology. In this work, we exploit the anisotropic nonlinear susceptibility tensors associated with thin-film lithium niobate to construct nanophotonic chip-space… ▽ More Miniaturized and reconfigurable interfaces between confined optical modes within integrated photonic chips and structured light propagating in free space would serve as a cornerstone for fundamental optical science and modern photonic technology. In this work, we exploit the anisotropic nonlinear susceptibility tensors associated with thin-film lithium niobate to construct nanophotonic chip-space interfaces capable of flexibly generating and multi-dimensionally engineering structured light via injections of photons to on-chip waveguides. By harnessing the nonlinear Čerenkov radiation in integrated nonlinear microring resonators, we successfully tailor the spatial profile, polarization state, emission wavelength, topological charge and temporal wave packet of structured optical vortices, exhibiting reconfigurabilities and tuning ranges far beyond the state-of-the-art. To further showcase the capabilities of our platform, we use a single pump to generate tunable optical skyrmions via the spin-orbit coupling and multi-state integrated vortex microcombs in the visible range via synergistic $χ^{(2)}$ and $χ^{(3)}$ nonlinear optical processes. Our work bridges the research fields of structured light and integrated nonlinear optics, providing unprecedented opportunities for spatiotemporal light generation and on-chip multidimensional nonlinear optics. △ Less

Submitted 6 March, 2026; originally announced March 2026.

Comments: To appear in Nature Materials

Angular distribution of Kα x rays following nonradiative double electron capture in relativistic collisions of Xe54+ ions with Kr and Xe atoms

Authors: Bian Yang, Deyang Yu, Konstantin N. Lyashchenko, Caojie Shao, Zhongwen Wu, Mingwu Zhang, Oleg Yu. Andreev, Junliang Liu, Zhangyong Song, Yingli Xue, Wei Wang, Fangfang Ruan, Yehong Wu, Rongchun Lu, Chenzhong Dong, Xiaohong Cai

Abstract: We present experimental study of nonradiative double electron capture processes in collisions of 95 and 146 MeV/u bare xenon ions with krypton and xenon gaseous atoms at the HIRFL-CSR storage ring. Angular distributions of the characteristic Kα radiation of the down-charged projectile ions Xe52+* are measured, which are closely related to the magnetic sublevel population of the excited 1s2l_j stat… ▽ More We present experimental study of nonradiative double electron capture processes in collisions of 95 and 146 MeV/u bare xenon ions with krypton and xenon gaseous atoms at the HIRFL-CSR storage ring. Angular distributions of the characteristic Kα radiation of the down-charged projectile ions Xe52+* are measured, which are closely related to the magnetic sublevel population of the excited 1s2l_j states of Xe52+*. It was found that the Kα1 radiation shows pronounced anisotropic and is sensitive to the collision energies and the target atoms, whereas the Kα2 radiation gives rise to isotropic. Moreover, obviously difference in the anisotropy parameters of Lyman-α1 of Xe53+* ions and Kα transitions of Xe52+* ions separately following nonradiative single and double electron capture into the L-shell levels of projectiles is obtained and discussed. △ Less

Submitted 4 March, 2026; originally announced March 2026.

Comments: 19 pages, 7 figures

Multi-Condition Digital Twin Calibration for Axial Piston Pumps : Compound Fault Simulation

Authors: Chang Dong, Jianfeng Tao, Chengliang Liu

Abstract: Axial piston pumps are indispensable power sources in high-stakes fluid power systems, including aerospace, marine, and heavy machinery applications. Their operational reliability is frequently compromised by compound faults that simultaneously affect multiple friction pairs. Conventional data-driven diagnosis methods suffer from severe data scarcity for compound faults and poor generalization acr… ▽ More Axial piston pumps are indispensable power sources in high-stakes fluid power systems, including aerospace, marine, and heavy machinery applications. Their operational reliability is frequently compromised by compound faults that simultaneously affect multiple friction pairs. Conventional data-driven diagnosis methods suffer from severe data scarcity for compound faults and poor generalization across varying operating conditions. This paper proposes a novel multi-condition physics-data coupled digital twin calibration framework that explicitly resolves the fundamental uncertainty of pump outlet flow ripple. The framework comprises three synergistic stages: in-situ virtual high-frequency flow sensing on a dedicated rigid metallic segment, surrogate model-assisted calibration of the 3D CFD source model using physically estimated ripple amplitudes, and multi-objective inverse transient analysis for viscoelastic unsteady-friction pipeline parameter identification. Comprehensive experiments on a test rig demonstrate that the calibrated digital twin accurately reproduces both single-fault and two representative compound-fault. These results establish a high-fidelity synthetic fault-generation capability that directly enables robust zero-shot fault diagnosis under previously unseen operating regimes and fault combinations, thereby advancing predictive maintenance in complex hydraulic systems. △ Less

Submitted 15 March, 2026; v1 submitted 27 February, 2026; originally announced March 2026.

Comments: More content will be added; this paper will be updated in 1-3 months

Transition of Magnetic Reconnection Regimes in Partially Ionized Plasmas

Authors: Liang Wang, Chuanfei Dong, Yi-Min Huang, Yue Yuan, Xinmin Li, Yang Zhang

Abstract: Magnetic reconnection in partially ionized plasmas plays a crucial role in a wide range of solar, astrophysical, and laboratory environments. While reconnection in such plasmas is commonly characterized by the ion-neutral coupling strength and the ionization fraction $χ=n_{i}/(n_{i}+n_{n})$, most previous studies have focused primarily on the former. A systematic exploration of the ionization frac… ▽ More Magnetic reconnection in partially ionized plasmas plays a crucial role in a wide range of solar, astrophysical, and laboratory environments. While reconnection in such plasmas is commonly characterized by the ion-neutral coupling strength and the ionization fraction $χ=n_{i}/(n_{i}+n_{n})$, most previous studies have focused primarily on the former. A systematic exploration of the ionization fraction, particularly in combination with ion-neutral coupling, is still lacking. This study presents the first systematic scan of the two-dimensional parameter space defined by ion-neutral collisionality and ionization fraction, enabling investigation of the transition from strongly coupled reconnection to faster, decoupled reconnection. To achieve this, we employ a new three-fluid, five-moment numerical model that treats electrons, ions, and neutrals as separate species on an equal footing. We find that in the strongly coupled regime, the reconnection rate is consistent with a $χ^{1/4}$ scaling. As collisionality decreases, the system transitions to a fast, ionization-independent regime. On the other hand, in the weakly coupled and fast-reconnection regimes, the current sheet approaches an ion-inertial-scale thickness rather than the expanded hybrid scale $d_{i}χ^{-1/2}$ predicted by fully coupled analytic fluid theories. The identified critical thickness and the resulting onset of fast reconnection agree reasonably well with recent fully kinetic simulations and laboratory experiments. In addition, we show that, over a wide range of coupling strengths, the ion outflow velocities remain Alfvénic, scaling with the appropriate ion or hybrid Alfvén speed, while the hybrid outflow velocity scales as $χ^{1/2}$ when normalized by ion Alfvén speed. △ Less

Submitted 4 August, 2026; v1 submitted 27 February, 2026; originally announced February 2026.

Comments: 9 pages, 5 figures

Near-optimal discrimination of displaced squeezed binary signals using displacement, inverse-squeezing, and photon-number-resolving detection

Authors: Enhao bai, Jian Peng, Tianyi Wu, Kai Wen, Fengkai Sun, Chun Zhou, Yaping Li, Zhenrong Zhang, Chen Dong

Abstract: We propose an inverse-squeezing Kennedy receiver for discriminating binary phase-shift-keyed displaced squeezed vacuum states. The receiver combines a Kennedy-type nulling displacement, an orthogonally oriented inverse-squeezing operation and photon-number-resolving detection with a maximum-a-\emph{posteriori} threshold rule. Its key mechanism is that the inverse-squeezing stage converts transmitt… ▽ More We propose an inverse-squeezing Kennedy receiver for discriminating binary phase-shift-keyed displaced squeezed vacuum states. The receiver combines a Kennedy-type nulling displacement, an orthogonally oriented inverse-squeezing operation and photon-number-resolving detection with a maximum-a-\emph{posteriori} threshold rule. Its key mechanism is that the inverse-squeezing stage converts transmitter-side squeezing into enhanced photon-number contrast, or equivalently an effective coherent-state energy gain, that can be directly exploited at the measurement stage. Under ideal equal-prior conditions, the receiver surpasses the standard quantum limit for squeezed-state binary phase-shift keying at approximately $N\approx 0.3$, outperforms the Helstrom bound of coherent-state binary phase-shift keying at approximately $N\approx 0.4$, and reaches the 1\% error level near $N\approx 0.6$. We further analyze its performance under realistic imperfections, including finite detector efficiency, dark counts, channel phase diffusion, receiver thermal noise and transmission loss. The results show that adaptive thresholding preserves robust performance against detector and noise imperfections over practical parameter ranges, whereas transmission loss progressively suppresses the squeezing-enabled advantage. These findings indicate that, for the fixed source parametrization adopted in this work, the proposed receiver is most advantageous in the low-loss regime, especially at low source energies. △ Less

Submitted 11 May, 2026; v1 submitted 13 January, 2026; originally announced January 2026.

Spectral Properties and Energy Injection in Mercury's Magnetotail Current Sheet

Authors: Xinmin Li, Chuanfei Dong, Liang Wang, Sae Aizawa, Lina Z. Hadid, Chi Zhang, Hongyang Zhou, James A. Slavin, Jiawei Gao, Mirko Stumpo, Wei Zhang

Abstract: Mercury's magnetotail hosts a thin and highly dynamic current sheet (CS), where magnetic reconnection and strong fluctuations frequently occur. Here, we statistically analyze magnetic field power spectra across 370 magnetotail CSs observed by MESSENGER. About 20% of the events are quasi-laminar, showing single power-law spectra, whereas 80% are turbulent, exhibiting a spectral break separating ine… ▽ More Mercury's magnetotail hosts a thin and highly dynamic current sheet (CS), where magnetic reconnection and strong fluctuations frequently occur. Here, we statistically analyze magnetic field power spectra across 370 magnetotail CSs observed by MESSENGER. About 20% of the events are quasi-laminar, showing single power-law spectra, whereas 80% are turbulent, exhibiting a spectral break separating inertial and kinetic ranges. A dawn-dusk asymmetry is identified: inertial-range slopes are systematically shallower on the dawnside, whereas kinetic-range slopes are steeper, indicating more developed turbulence there, consistent with the higher occurrence of reconnection-related processes on the dawnside. Component analysis shows that the transverse components, orthogonal to the tail-aligned principal field (BX), display shallow slopes near -1 in the inertial range, suggesting energy injection at ion scales rather than a classical inertial range. These results demonstrate that Mercury's unique plasma environment fundamentally reshapes the initiation of turbulence and the redistribution of energy in the magnetotail. △ Less

Submitted 25 December, 2025; originally announced January 2026.

Journal ref: Geophysical Research Letters, 53, e2025GL120144 (2026)

Magic wavelengths and triple magic trapping conditions for $5s^2~^1\!S_0$ and $5s5p~^3\!P_{0,2}$ states of Sr atoms

Authors: Yan-Min Wang, Qing-Yi Liu, Yong-Bo Tang, Lei Wu, Deng-Hong Zhang, Chen-Zhong Dong, Jun Jiang

Abstract: The static and dynamic electric dipole polarizabilities of the $5s^2~^1\!S_0$ and $5s5p~^3\!P_{0,2}$ states of Sr atoms are calculated using the relativistic configuration interaction plus the many-body perturbation theory (RCI+MBPT) method. Magic wavelengths are determined for the transitions $5s^2~^1\!S_0\rightarrow 5s5p~^3\!P_{0}$, $5s^2~^1\!S_0\rightarrow 5s5p~^3\!P_{2}$, and… ▽ More The static and dynamic electric dipole polarizabilities of the $5s^2~^1\!S_0$ and $5s5p~^3\!P_{0,2}$ states of Sr atoms are calculated using the relativistic configuration interaction plus the many-body perturbation theory (RCI+MBPT) method. Magic wavelengths are determined for the transitions $5s^2~^1\!S_0\rightarrow 5s5p~^3\!P_{0}$, $5s^2~^1\!S_0\rightarrow 5s5p~^3\!P_{2}$, and $5s5p~^3\!P_0\rightarrow 5s5p~^3\!P_{2}$. A comprehensive study is conducted on the dependence of magic wavelengths on the angle between the laser polarization and the magnetic field. Furthermore, the conditions for realizing triple magic trapping at 813.4~nm for the $5s^2~^1\!S_0$, $5s5p~^3\!P_{0}$ and $5s5p~^3\!P_{2}$ states are investigated. In the case of linearly polarized light, when the angle ($θ_p$) between the laser polarization direction and the magnetic field is $79.1(0.7)^\circ$, triple magic trapping for the $5s^2~^1\!S_0$, $5s5p~^3\!P_{0}$, and $5s5p~^3\!P_{2}~M=0$ states can be achieved. This result agrees well with the recent experimental measurement (78.49(3)$^\circ$)[Phys. Rev. Lett. 135, 143401 (2025)]. Meanwhile, triple magic trapping involving the $5s5p~^3\!P_{2}~M=2$ state can be achieved when $θ_p= 37.4(0.3)^\circ$. The conditions for achieving triple magic trapping with circularly and arbitrarily elliptically polarized light are also presented. △ Less

Submitted 29 December, 2025; originally announced December 2025.

Revisiting Mars' Induced Magnetic Field and Clock Angle Departures under Real-Time Upstream Solar Wind Conditions

Authors: Zhihao Cheng, Chi Zhang, Chuanfei Dong, Hongyang Zhou, Jiawei Gao, Abigail Tadlock, Xinmin Li, Liang Wang

Abstract: Mars lacks a global intrinsic dipole magnetic field, but its interaction with the solar wind generates a global induced magnetosphere. Until now, most studies have relied on single-spacecraft measurements, which could not simultaneously capture upstream solar wind conditions and the induced magnetic fields, thereby limiting our understanding of the system. Here, we statistically re-examine the pro… ▽ More Mars lacks a global intrinsic dipole magnetic field, but its interaction with the solar wind generates a global induced magnetosphere. Until now, most studies have relied on single-spacecraft measurements, which could not simultaneously capture upstream solar wind conditions and the induced magnetic fields, thereby limiting our understanding of the system. Here, we statistically re-examine the properties of Mars' induced magnetic field by incorporating, for the first time, real-time upstream solar wind conditions from the coordinated MAVEN and Tianwen-1 observations. Our results are show that both solar wind dynamic pressure and the interplanetary magnetic field (IMF) magnitude enhance the strength of the induced magnetic field, but they exert opposite effects on the compression ratio: higher dynamic pressure strengthens compression, while stronger IMF weakens it. The induced field is stronger under quasi-perpendicular IMF conditions compared with quasi-parallel IMF, reflecting a stronger mass-loading effect. We further investigate the clock angle departures of the induced fields. They remain relatively small in the magnetosheath near the bow shock, increase gradually toward the induced magnetosphere, and become significantly larger within the induced magnetosphere. In addition, clock angle departures are strongly enhanced under quasi-parallel IMF conditions. Their dependence on upstream drivers further shows that, within the magnetosheath, clock angle departures are minimized under low dynamic pressure, high IMF magnitude, and low Alfven Mach number conditions. These results may enhance our understanding of solar wind interaction with Mars, and highlight the critical role of multi-point observations. △ Less

Submitted 21 December, 2025; originally announced December 2025.

Comments: 27 pages, 8 figures, accepted for publication in Journal of Geophysical Research: Space Physics

Journal ref: Journal of Geophysical Research: Space Physics, 130, e2025JA034688 (2025)

Physics-Informed Neural Networks for Modeling the Martian Induced Magnetosphere

Authors: Jiawei Gao, Chuanfei Dong, Chi Zhang, Yilan Qin, Simin Shekarpaz, Xinmin Li, Liang Wang, Hongyang Zhou, Abigail Tadlock

Abstract: Understanding the magnetic field environment around Mars and its response to upstream solar wind conditions provide key insights into the processes driving atmospheric ion escape. To date, global models of Martian induced magnetosphere have been exclusively physics-based, relying on computationally intensive simulations. For the first time, we develop a data-driven model of the Martian induced mag… ▽ More Understanding the magnetic field environment around Mars and its response to upstream solar wind conditions provide key insights into the processes driving atmospheric ion escape. To date, global models of Martian induced magnetosphere have been exclusively physics-based, relying on computationally intensive simulations. For the first time, we develop a data-driven model of the Martian induced magnetospheric magnetic field using Physics-Informed Neural Network (PINN) combined with MAVEN observations and physical laws. Trained under varying solar wind conditions, including B_IMF, P_SW, and θ_cone, the data-driven model accurately reconstructs the three-dimensional magnetic field configuration and its variability in response to upstream solar wind drivers. Based on the PINN results, we identify key dependencies of magnetic field configuration on solar wind parameters, including the hemispheric asymmetries of the draped field line strength in the Mars-Solar-Electric coordinates. These findings demonstrate the capability of PINNs to reconstruct complex magnetic field structures in the Martian induced magnetosphere, thereby offering a promising tool for advancing studies of solar wind-Mars interactions. △ Less

Submitted 17 December, 2025; originally announced December 2025.

Journal ref: Geophysical Research Letters, 53, e2025GL121532

Initial performance results of the JUNO detector

Authors: Angel Abusleme, Thomas Adam, Kai Adamowicz, David Adey, Shakeel Ahmad, Rizwan Ahmed, Timo Ahola, Sebastiano Aiello, Fengpeng An, Guangpeng An, Costas Andreopoulos, Giuseppe Andronico, João Pedro Athayde Marcondes de André, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, Didier Auguste, Margherita Buizza Avanzini, Andrej Babic, Jingzhi Bai, Weidong Bai, Nikita Balashov, Roberto Barbera, Andrea Barresi , et al. (1114 additional authors not shown)

Abstract: The Jiangmen Underground Neutrino Observatory (JUNO) started physics data taking on 26 August 2025. JUNO consists of a 20-kton liquid scintillator central detector, surrounded by a 35 kton water pool serving as a Cherenkov veto, and almost 1000 m$^2$ of plastic scintillator veto on top. The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e. This paper present… ▽ More The Jiangmen Underground Neutrino Observatory (JUNO) started physics data taking on 26 August 2025. JUNO consists of a 20-kton liquid scintillator central detector, surrounded by a 35 kton water pool serving as a Cherenkov veto, and almost 1000 m$^2$ of plastic scintillator veto on top. The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e. This paper presents the performance results of the detector, extensively studied during the commissioning of the water phase, the subsequent liquid scintillator filling phase, and the first physics runs. The liquid scintillator achieved an attenuation length of 20.6 m at 430 nm, while the high coverage PMT system and scintillator together yielded about 1785 photoelectrons per MeV of energy deposit at the detector centre, measured using the 2.223 MeV $γ$ from neutron captures on hydrogen with an Am-C calibration source. The reconstructed energy resolution is 3.4% for two 0.511 MeV $γ$ at the detector centre and 2.9% for the 0.93 MeV quenched Po-214 alpha decays from natural radioactive sources. The energy nonlinearity is calibrated to better than 1%. Intrinsic contaminations of U-238 and Th-232 in the liquid scintillator are below 10$^{-16}$ g/g, assuming secular equilibrium. The water Cherenkov detector achieves a muon detection efficiency better than 99.9% for muons traversing the liquid scintillator volume. During the initial science runs, the data acquisition duty cycle exceeded 97.8%, demonstrating the excellent stability and readiness of JUNO for high-precision neutrino physics. △ Less

Submitted 18 November, 2025; originally announced November 2025.

Comments: 38 pages, 23 figures

Low-Energy Free-Electron Nonclassical Lasing

Authors: Mai Zhang, Yu Wang, Chang-Ling Zou, Lei Ying, Qiongyi He, Guang-Can Guo, Chun-Hua Dong

Abstract: Harnessing a beam of slow free electrons in artificial photonic structures offers a powerful, tunable platform for generating nonclassical light without the need for heavy physical equipment. Here we present a theory of nonclassical lasing, demonstrating how incoherent electrons in photonic crystal cavities can coherently emit photons through collective dynamics. When photon emission rate exceeds… ▽ More Harnessing a beam of slow free electrons in artificial photonic structures offers a powerful, tunable platform for generating nonclassical light without the need for heavy physical equipment. Here we present a theory of nonclassical lasing, demonstrating how incoherent electrons in photonic crystal cavities can coherently emit photons through collective dynamics. When photon emission rate exceeds cavity losses, nonclassical lasing with sub-Poissonian photon statistics emerges, driven by multi-photon Rabi oscillations. At specific coupling strengths, quantum state trapping effect emerges, producing high-fidelity Fock states at room temperature (e.g. nearly 90%-fidelity of four photon Fock state). Notably, the frequency of the emitted photons can be readily tuned via the velocity of the injected electrons to match cavity modes. This approach supports photonic integration and offers a scalable, energy-efficient platform for room-temperature quantum light sources and advanced studies in quantum electrodynamics. △ Less

Submitted 13 November, 2025; originally announced November 2025.

Prospects for geoneutrino detection with JUNO

Authors: Thomas Adam, Shakeel Ahmad, Rizwan Ahmed, Fengpeng An, João Pedro Athayde Marcondes de André, Costas Andreopoulos, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Didier Auguste, Marcel Büchner, Weidong Bai, Nikita Balashov, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Beretta, Antonio Bergnoli, Nikita Bessonov, Daniel Bick, Lukas Bieger, Svetlana Biktemerova, Thilo Birkenfeld, Simon Blyth , et al. (605 additional authors not shown)

Abstract: Geoneutrinos, which are antineutrinos emitted during the decay of long-lived radioactive elements inside Earth, serve as a unique tool for studying the composition and heat budget of our planet. The Jiangmen Underground Neutrino Observatory (JUNO) experiment in China, which has recently completed construction, is expected to collect a sample comparable in size to the entire existing world geoneutr… ▽ More Geoneutrinos, which are antineutrinos emitted during the decay of long-lived radioactive elements inside Earth, serve as a unique tool for studying the composition and heat budget of our planet. The Jiangmen Underground Neutrino Observatory (JUNO) experiment in China, which has recently completed construction, is expected to collect a sample comparable in size to the entire existing world geoneutrino dataset in less than a year. This paper presents an updated estimation of sensitivity to geoneutrinos of JUNO using the best knowledge available to date about the experimental site, the surrounding nuclear reactors, the detector response uncertainties, and the constraints expected from the TAO satellite detector. To facilitate comparison with present and future geological models, our results cover a wide range of predicted signal strengths. Despite the significant background from reactor antineutrinos, the experiment will measure the total geoneutrino flux with a precision comparable to that of existing experiments within its first few years, ultimately achieving a world-leading precision of about 8% over ten years. The large statistics of JUNO will also allow separation of the Uranium-238 and Thorium-232 contributions with unprecedented precision, providing crucial constraints on models of formation and composition of Earth. Observation of the mantle signal above the lithospheric flux will be possible but challenging. For models with the highest predicted mantle concentrations of heat-producing elements, a 3-sigma detection over six years requires knowledge of the lithospheric flux to within 15%. Together with complementary measurements from other locations, the geoneutrino results of JUNO will offer cutting-edge, high-precision insights into the interior of Earth, of fundamental importance to both the geoscience and neutrino physics communities. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 32 pages, with 13 figures and 5 tables

Compact and high-resolution spectrometer via Brillouin integrated circuits

Authors: Jia-Qi Wang, Yuan-Hao Yang, Zheng-Xu Zhu, Juan-Juan Lu, Ming Li, Xiaoxuan Pan, Chuanlong Ma, Lintao Xiao, Bo Zhang, Weiting Wang, Chun-Hua Dong, Xin-Biao Xu, Guang-Can Guo, Luyan Sun, Chang-Ling Zou

Abstract: Optical spectrometers are indispensable tools across various fields, from chemical and biological sensing to astronomical observations and quantum technologies. However, the integration of spectrometers onto photonic chips has been hindered by the low spectral resolution or large device footprint with complex multiple channel operations. Here, we introduce a novel chip-integrated spectrometer by l… ▽ More Optical spectrometers are indispensable tools across various fields, from chemical and biological sensing to astronomical observations and quantum technologies. However, the integration of spectrometers onto photonic chips has been hindered by the low spectral resolution or large device footprint with complex multiple channel operations. Here, we introduce a novel chip-integrated spectrometer by leveraging the acoustically-stimulated Brillouin scattering in a hybrid photonic-phononic chip. The Brillouin interaction provides a dynamic reflection grating with a high reflectivity up to 50% and a fast switching time on the microsecond scale, achieving an unprecedented spectral resolution of 0.56 nm over a 110 nm bandwidth using just a single 1 mm-long straight waveguide. This remarkable performance approaches the fundamental limit of resolution for a given device size, validating the potential of the hybrid photonic-phononic device for efficient and dynamically-reconfigurable spectral analysis, and thus opens up new avenues for advanced optical signal processing and sensing applications. △ Less

Submitted 6 November, 2025; originally announced November 2025.

Reconfigurable on-chip vortex beam generation via acoustically stimulated Brillouin nonlinear optical radiation

Authors: Ming Li, Xiang Chen, Wen-Qi Duan, Yuan-Hao Yang, Jia-Qi Wang, Mai Zhang, Xin-Biao Xu, Chun-Hua Dong, Luyan Sun, Guang-Can Guo, Chang-Ling Zou

Abstract: The integrated devices that generate structured optical fields with non-trivial orbital angular momentum (OAM) hold great potential for advanced optical applications, but are restricted to complex nanostructures and static functionalities. Here, we demonstrate a reconfigurable OAM beam generator from a simple microring resonator without requiring grating-like nanostructures. Our approach harnesses… ▽ More The integrated devices that generate structured optical fields with non-trivial orbital angular momentum (OAM) hold great potential for advanced optical applications, but are restricted to complex nanostructures and static functionalities. Here, we demonstrate a reconfigurable OAM beam generator from a simple microring resonator without requiring grating-like nanostructures. Our approach harnesses Brillouin interaction between confined phonon and optical modes, where the acoustic field is excited through microwave input. The phonon stimulate the conversion from a guided optical mode into a free-space vortex beam. Under the selection rule of the radiation, the OAM order of the emitted light is determined by the acousto-optic phase matching and is rapidly reconfigurable by simply tuning the microwave frequency. Furthermore, this all-microwave control scheme allows for the synthesis of arbitrary high-dimensional OAM superpositions by programming the amplitudes and phases of the driving fields. Analytical and numerical models predict a radiation efficiency over 25\% for experimentally feasible on-chip microcavities. This work introduces a novel paradigm for chip-to-free-space interfaces, replacing fixed nanophotonic structures with programmable acousto-optic interactions for versatile structured light generation. △ Less

Submitted 19 November, 2025; v1 submitted 16 October, 2025; originally announced October 2025.

Comments: 6 pages, 4 figures

Multi-Channel Microwave-to-Optics Conversion Utilizing a Hybrid Photonic-Phononic Waveguide

Authors: Yuan-Hao Yang, Jia-Qi Wang, Zheng-Xu Zhu, Yu Zeng, Ming Li, Yan-Lei Zhang, Juanjuan Lu, Qiang Zhang, Weiting Wang, Chun-Hua Dong, Xin-Biao Xu, Guang-Can Guo, Luyan Sun, Chang-Ling Zou

Abstract: Efficient and coherent conversion between microwave and optical signals is crucial for a wide range of applications, from quantum information processing to microwave photonics and radar systems. However, existing conversion techniques rely on cavity-enhanced interactions, which limit the bandwidth and calability. Here, we demonstrate the first multi-channel microwave-to-optics conversion by introd… ▽ More Efficient and coherent conversion between microwave and optical signals is crucial for a wide range of applications, from quantum information processing to microwave photonics and radar systems. However, existing conversion techniques rely on cavity-enhanced interactions, which limit the bandwidth and calability. Here, we demonstrate the first multi-channel microwave-to-optics conversion by introducing a traveling-wave architecture that leverages a hybrid photonic-phononic waveguide on thin-film lithium niobate (TFLN). Our approach exploits continuous phase-matching rather than discrete resonances, enabling unprecedented operational bandwidths exceeding 40 nm in the optical domain and 250 MHz in the microwave domain. By harnessing the strong piezoelectric and photoelastic effects of TFLN, we achieve coherent conversion between 9 GHz microwave photons and 1550 nm telecom photons via traveling phonons, with an internal efficiency of 2.2% (system efficiency 2.4 *10^-4 ) at room temperature. Remarkably, we demonstrate simultaneous operation of nine conversion channels in a single device. Our converter opens up new opportunities for seamless integration of microwave and photonic technologies, enabling the quantum interface for distributed quantum computing with superconducting quantum processors, high efficient microwave signal processing, and advanced radar applications. △ Less

Submitted 12 September, 2025; originally announced September 2025.

Study of a Compact Device for Water Attenuation Length Measurements

Authors: Junyou Chen, Jilei Xu, Yongbo Huang, Sibo Wang, Chuanshi Dong, Haoqi Lu, Changgen Yang, Yongpeng Zhang, Yi Wang

Abstract: This study presents the development and validation of a compact device for measuring the water attenuation length (WAL), utilizing photomultiplier tubes (PMTs), optical fibers, and light-emitting diodes (LEDs). An 8 m water tank and the device was constructed and validated in the laboratory. The device is capable of measuring WAL values up to 50 m. The stray light was blocked mainly by a custom-de… ▽ More This study presents the development and validation of a compact device for measuring the water attenuation length (WAL), utilizing photomultiplier tubes (PMTs), optical fibers, and light-emitting diodes (LEDs). An 8 m water tank and the device was constructed and validated in the laboratory. The device is capable of measuring WAL values up to 50 m. The stray light was blocked mainly by a custom-designed shutter. Toy Monte Carlo simulations were employed to evaluate the measurement uncertainty, which was found to be within reasonable limits. These simulations further indicate that the uncertainty can be reduced and more accurately predicted for a larger-scale device with a length of 30 m. Real-time monitoring was achieved by integrating the device into a water purification circulation system, providing a practical, scalable solution for WAL measurement in future large-scale water Cherenkov detectors. △ Less

Submitted 30 October, 2025; v1 submitted 11 September, 2025; originally announced September 2025.

Magnetic Field and Plasma Asymmetries Between the Martian Quasi-Perpendicular and Quasi-Parallel Magnetosheaths

Authors: Abigail Tadlock, Chuanfei Dong, Chi Zhang, Markus Franz, Hongyang Zhou, Jiawei Gao

Abstract: The Martian magnetosheath acts as a conduit for mass and energy transfer between the upstream solar wind and its induced magnetosphere. However, our understanding of its global properties remains limited. Using nine years of data from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we performed a quantitative statistical analysis to explore the spatial distribution of the magnetic f… ▽ More The Martian magnetosheath acts as a conduit for mass and energy transfer between the upstream solar wind and its induced magnetosphere. However, our understanding of its global properties remains limited. Using nine years of data from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we performed a quantitative statistical analysis to explore the spatial distribution of the magnetic fields, solar wind and planetary ions in the magnetosheath. We discovered significant asymmetries in the magnetic field, solar wind protons, and planetary ions between the quasi-perpendicular and quasi-parallel magnetosheaths. The asymmetries in the Martian magnetosheath exhibit both similarities and differences compared to those in the Earth's and Venus' magnetosheaths. These results indicate that the Martian magnetosheath is distinctly shaped by both shock geometry and planetary ions. △ Less

Submitted 8 September, 2025; originally announced September 2025.

Comments: 16 pages, 4 figures, accepted for publication in Geophysical Research Letters

Journal ref: Geophysical Research Letters, 52, e2025GL118172 (2025)

Surrogate Modeling of Landau Damping with Deep Operator Networks

Authors: Simin Shekarpaz, Chuanfei Dong, Ziyu Huang

Abstract: Kinetic simulations excel at capturing microscale plasma physics phenomena with high accuracy, but their computational demands make them impractical for modeling large-scale space and astrophysical systems. In this context, we build a surrogate model, using Deep Operator Networks (DeepONets), based upon the Vlasov-Poisson simulation data to model the dynamical evolution of plasmas, focusing on the… ▽ More Kinetic simulations excel at capturing microscale plasma physics phenomena with high accuracy, but their computational demands make them impractical for modeling large-scale space and astrophysical systems. In this context, we build a surrogate model, using Deep Operator Networks (DeepONets), based upon the Vlasov-Poisson simulation data to model the dynamical evolution of plasmas, focusing on the Landau damping process - a fundamental kinetic phenomenon in space and astrophysical plasmas. The trained DeepONets are able to capture the evolution of electric field energy in both linear and nonlinear regimes under various conditions. Extensive validation highlights DeepONets' robust performance in reproducing complex plasma behaviors with high accuracy, paving the way for large-scale modeling of space and astrophysical plasmas. △ Less

Submitted 4 September, 2025; v1 submitted 22 July, 2025; originally announced July 2025.

Comments: 10 pages, 8 figures, 4 tables, accepted for publication in ApJ

Journal ref: The Astrophysical Journal, 990:161 (8pp), 2025

Observation of a Knotted Electron Diffusion Region in Earth's Magnetotail Reconnection

Authors: Xinmin Li, Chuanfei Dong, Hantao Ji, Chi Zhang, Liang Wang, Barbara Giles, Hongyang Zhou, Rui Chen, Yi Qi

Abstract: Magnetic reconnection is a fundamental plasma process that alters the magnetic field topology and releases magnetic energy. Most numerical simulations and spacecraft observations assume a two-dimensional diffusion region, with the electron diffusion region (EDR) embedded in the same plane as the ion diffusion region (IDR) and a uniform guide field throughout. Using observations from Magnetospheric… ▽ More Magnetic reconnection is a fundamental plasma process that alters the magnetic field topology and releases magnetic energy. Most numerical simulations and spacecraft observations assume a two-dimensional diffusion region, with the electron diffusion region (EDR) embedded in the same plane as the ion diffusion region (IDR) and a uniform guide field throughout. Using observations from Magnetospheric Multiscale (MMS) mission, we report a non-coplanar, knotted EDR in Earth's magnetotail current sheet. The reconnection plane of the knotted EDR deviates by approximately 38° from that of the IDR, with the guide field exhibiting both a 38° directional shift and a twofold increase in amplitude. Moreover, the Hall magnetic field is bipolar in the EDR but quadrupolar in the IDR, indicating different Hall current structures at electron and ion scales. These observations highlight the importance of three-dimensional effects and illustrate the complexity of multiscale coupling between the EDR and IDR during reconnection studies.1 △ Less

Submitted 14 July, 2025; originally announced July 2025.

Comments: 27 pages and 4 figures

Journal ref: Geophysical Research Letters,2025

Planar Collisionless Shock Simulations with Semi-Implicit Particle-in-Cell Model FLEKS

Authors: Hongyang Zhou, Yuxi Chen, Chuanfei Dong, Liang Wang, Ying Zou, Brian Walsh, Gábor Tóth

Abstract: This study investigates the applicability of the semi-implicit particle-in-cell code FLEKS to heliospheric shock simulations. We examine one- and two-dimensional local planar shock simulations, initialized using MHD states with upstream conditions representative of plasmas in the hypersonic, $β\sim 1$ regime, for both quasi-perpendicular and quasi-parallel configurations. The refined algorithm in… ▽ More This study investigates the applicability of the semi-implicit particle-in-cell code FLEKS to heliospheric shock simulations. We examine one- and two-dimensional local planar shock simulations, initialized using MHD states with upstream conditions representative of plasmas in the hypersonic, $β\sim 1$ regime, for both quasi-perpendicular and quasi-parallel configurations. The refined algorithm in FLEKS proves robust, enabling accurate shock simulations with a grid resolution on the order of the electron inertial length $d_e$. Our simulations successfully capture key shock features, including shock structures (foot, ramp, overshoot, and undershoot), upstream and downstream waves (fast magnetosonic, whistler, Alfvén ion-cyclotron, and mirror modes), and non-Maxwellian particle distributions. Crucially, we find that at least two spatial dimensions are critical for accurately reproducing downstream wave physics in quasi-perpendicular shocks and capturing the complex dynamics of quasi-parallel shocks, including surface rippling, shocklets, SLAMS, magnetic reconnection and jets. Furthermore, our parameter studies demonstrate the impact of mass ratio and grid resolution on shock physics. This work provides valuable guidance for selecting appropriate physical and numerical parameters for shock simulations using a semi-implicit PIC method, paving the way for incorporating kinetic shock processes into large-scale collisionless plasma simulations with the MHD-AEPIC model. △ Less

Submitted 29 October, 2025; v1 submitted 9 June, 2025; originally announced June 2025.

Dynamic Control of Momentum-Polarization Photoluminescence States with Liquid-Crystal-tuned Nanocavities

Authors: Chengkun Dong, Matthew R. Chua, Rasna Maruthiyodan Veetil, T. Thu Ha Do, Lu Ding, Deepak K. Sharma, Jun Xia, Ramón Paniagua-Domínguez

Abstract: Dynamic control of light, and in particular beam steering, is pivotal in various optical applications, including telecommunications, LiDAR, and biomedical imaging. Traditional approaches achieve this by interfacing a tunable modulating device with an external light source, facing challenges in achieving compact devices. Here, we introduce a dynamic photoluminescence (PL) modulating device, with wh… ▽ More Dynamic control of light, and in particular beam steering, is pivotal in various optical applications, including telecommunications, LiDAR, and biomedical imaging. Traditional approaches achieve this by interfacing a tunable modulating device with an external light source, facing challenges in achieving compact devices. Here, we introduce a dynamic photoluminescence (PL) modulating device, with which the properties of light directly emitted by a quasi-two-dimensional perovskite (in particular its directionality and polarization) can be modified continuously and over a large range. The device is based on a liquid-crystal-tunable Fabry-Perot (FP) nanocavity and uses the FP energy-momentum dispersion and spin-orbit coupling between the excitons and the cavity modes to enable this dynamic control over the emitted radiation. With this device, we achieve electrically-controlled, continuous and variable emission angles up to a maximum of 28°, as well as manipulation of the PL polarization state, enabling both the creation of polarization gradients and the achievement of polarization conversion at specific emission angles. Moreover, due to its resonant character, a 3-fold increase in the emission intensity is observed, as confirmed through time-resolved photoluminescence (TRPL) measurements. Our approach leverages the unique properties of actively tunable birefringent nanocavities to improve emission directivity, angle tunability and polarization control, presenting a promising solution for next-generation, deeply integrated beam steering devices. △ Less

Submitted 30 May, 2025; originally announced June 2025.

Photonic chip-based high-efficiency soliton microcombs via electroopitc-Kerr synergy

Authors: Rui Niu, Shuai Wan, Pi-Yu Wang, Rui Ma, Jin Li, Fang Bo, Zhen Shen, Guang-Can Guo, Fang-Wen Sun, Junqiu Liu, Chun-Hua Dong

Abstract: Temporal soliton mode-locking in coherently pumped microcavities provides a promising platform for miniaturized frequency comb systems. While significant progress has been made, achieving high conversion efficiency in such microcombs remains a critical challenge. Soliton generation through pulse pumping has emerged as an effective strategy to improve conversion efficiency. However, the on-chip int… ▽ More Temporal soliton mode-locking in coherently pumped microcavities provides a promising platform for miniaturized frequency comb systems. While significant progress has been made, achieving high conversion efficiency in such microcombs remains a critical challenge. Soliton generation through pulse pumping has emerged as an effective strategy to improve conversion efficiency. However, the on-chip integration of pulse generation with dissipative Kerr soliton (DKS) formation within the photonic chip has not yet been realized. In this work, we demonstrate a photonic chip-based soliton microcomb with high conversion efficiency, achieved by integrating on-chip pulse generation and DKS generation. The pulsed laser, fabricated on a lithium niobate-on-insulator (LNOI) platform, delivers a 35.5GHz repetition rate with broadly tunable center frequencies. By coupling these on-chip pulses to a silicon nitride microresonator, we achieve stable DKS generation with a pump-to-soliton conversion efficiency of 43.9% under steady-state conditions. This integrated architecture establishes a viable pathway toward chip-scale soliton microcombs with unprecedented efficiency, opening up new possibilities for optical communications, precision spectroscopy, and photonic sensing. △ Less

Submitted 20 May, 2025; originally announced May 2025.

Liquid combs: broadband light with equidistance and without stability

Authors: Mithun Roy, Tianyi Zeng, Zhenyang Xiao, Chao Dong, Sadhvikas Addamane, Qing Hu, David Burghoff

Abstract: Broadband light sources with well-defined spectral structures are vital for science and technology. However, the evenly spaced lines of frequency combs represent only a small subset of all possible structured white-light sources. We demonstrate liquid combs: optical states that preserve spectral equidistance but lack temporal stability. By engineering the gain and dispersion of semiconductor laser… ▽ More Broadband light sources with well-defined spectral structures are vital for science and technology. However, the evenly spaced lines of frequency combs represent only a small subset of all possible structured white-light sources. We demonstrate liquid combs: optical states that preserve spectral equidistance but lack temporal stability. By engineering the gain and dispersion of semiconductor laser cavities, we produce light that possesses rapid phase fluctuations but maintains relative phase differences between modes that vary identically. We show experimentally that this phenomenon occurs in multiple laser platforms -- across multiple octaves -- through the creation of a metrological technique that determines the phase differences. We also show theoretically that this is a general phenomenon that can be described using a mean-field theory. These liquid combs are attractive for many applications due to having wider bandwidths than frequency combs, and more generally, they represent the long-sought realization of structured white-light sources that are not combs. △ Less

Submitted 19 May, 2025; originally announced May 2025.

TBA-enabled spin-coating of a percolatively connected GO nanosieve for thru-hole epitaxy: tuning GO flake stacking and coverage to control GaN nucleation

Authors: Gunhoon Beak, Changwook Dong, Minah Choi, Jieun Yang, Joonwon Lim, Chinkyo Kim

Abstract: We report a spin-coating-based approach for forming a percolatively connected graphene oxide (GO) nanosieve on SiO$_2$-patterned sapphire substrates, where the addition of tetrabutylammonium (TBA) to the GO solution significantly improves the uniformity of flake coverage and modulates GaN nucleation behavior. Upon thermal annealing of GO, the resulting reduced graphene oxide (rGO) films exhibit sp… ▽ More We report a spin-coating-based approach for forming a percolatively connected graphene oxide (GO) nanosieve on SiO$_2$-patterned sapphire substrates, where the addition of tetrabutylammonium (TBA) to the GO solution significantly improves the uniformity of flake coverage and modulates GaN nucleation behavior. Upon thermal annealing of GO, the resulting reduced graphene oxide (rGO) films exhibit spatially varying coverage, leading to three distinct GaN nucleation outcomes: (i) ELOG-like nucleation on exposed substrate regions, (ii) thru-hole epitaxy (THE)-like nucleation through appropriately thin areas, and (iii) complete nucleation suppression on thickly stacked zones. On spin-coated GO films without TBA, all three behaviors coexist, and undesired ELOG- and no-nucleation modes persist due to uneven coverage. Importantly, these issues cannot be resolved by simply adjusting GO flake concentration, as concentration tuning alone fails to eliminate the formation of locally bare and overly thick regions. In contrast, the addition of TBA results in a more uniform, moderately stacked rGO morphology that suppresses both ELOG- and no-nucleation modes while expanding THE-like nucleation regions. This reshaped nucleation landscape confines GaN growth to areas with engineered percolative transport. The approach offers a scalable, lithography-free route for controlling GaN epitaxy using solution-processable 2D material masks. △ Less

Submitted 7 May, 2025; originally announced May 2025.

The Land$\acute{e}$ $g$ factors for the $6S_{1/2}$ , $5D_{3/2,5/2}$ states of Ba$^{+}$ ions

Authors: Bing-Bing Li, Jun Jiang, Lei Wu, Deng-Hong Zhang, Chen-Zhong Dong

Abstract: The Land$\acute{e}$ $g$ factors of Ba$^+$ are very important in high-precision measurement physics. The wave functions, energy levels, and Land$\acute{e}$ $g$ factors for the $6s$ $^{2}S_{1/2}$ and $5d$ $^{2}D_{3/2,5/2}$ states of Ba$^{+}$ ions were calculated using the multi-configuration Dirac-Hartree-Fock (MCDHF) method and the Model-QED method. The contributions of the electron correlation eff… ▽ More The Land$\acute{e}$ $g$ factors of Ba$^+$ are very important in high-precision measurement physics. The wave functions, energy levels, and Land$\acute{e}$ $g$ factors for the $6s$ $^{2}S_{1/2}$ and $5d$ $^{2}D_{3/2,5/2}$ states of Ba$^{+}$ ions were calculated using the multi-configuration Dirac-Hartree-Fock (MCDHF) method and the Model-QED method. The contributions of the electron correlation effects and quantum electrodynamics (QED) effects were discussed in detail. The transition energies are in excellent agreement with the experimental results, with differences of approximately 5 cm$^{-1}$. The presently calculated $g$ factor of 2.0024905(16) for the $6S_{1/2}$ agrees very well with the available experimental and theoretical results, with a difference at a level of 10$^{-6}$. For the $5D_{3/2, 5/2}$ states, the present results of 0.7993961(126) and 1.2003942(190) agree with the experimental results of 0.7993278(3) [\textcolor{blue}{Phys. Rev. A 54, 1199(1996)}] and 1.20036739(14) [\textcolor{blue}{Phys. Rev. Lett. 124, 193001 (2020)}] very well, with differences at the level of 10$^{-5}$. △ Less

Submitted 26 March, 2025; originally announced March 2025.

Machine-learning heat flux closure for multi-moment fluid modeling of nonlinear Landau damping

Authors: Ziyu Huang, Chuanfei Dong, Liang Wang

Abstract: Nonlinear plasma physics problems are usually simulated through comprehensive modeling of phase space. The extreme computational cost of such simulations has motivated the development of multi-moment fluid models. However, a major challenge has been finding a suitable fluid closure for these fluid models. Recent developments in physics-informed machine learning have led to a renewed interest in co… ▽ More Nonlinear plasma physics problems are usually simulated through comprehensive modeling of phase space. The extreme computational cost of such simulations has motivated the development of multi-moment fluid models. However, a major challenge has been finding a suitable fluid closure for these fluid models. Recent developments in physics-informed machine learning have led to a renewed interest in constructing accurate fluid closure terms. In this study, we take an approach that integrates kinetic physics from the first-principles Vlasov simulations into a fluid model (through the heat flux closure term) using the Fourier neural operator - a neural network architecture. Without resolving the phase space dynamics, this new fluid model is capable of capturing the nonlinear evolution of the Landau damping process that exactly matches the Vlasov simulation results. This machine learning-assisted new approach provides a computationally affordable framework that surpasses previous fluid models in accurately modeling the kinetic evolution of complex plasma systems. △ Less

Submitted 14 March, 2025; originally announced March 2025.

Comments: 6 figures

Journal ref: Proceedings of the National Academy of Sciences, Vol. 122, e2419073122 (2025)

Modulation of supernarrow EIT pair via atomic coherence

Authors: Lin Cheng, Zhiyuan Xiong, Shuaishuai Hou, Yijia Sun, Chenyu Dong, Fan Wu, Kun Huang

Abstract: We report the phenomena of electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) using two identical beams in rubidium atomic vapor. The Λ-type EIT configuration is employed to examine the EIT spectrum for the D1 line in 87Rb F=2 characteristics16 by varying parameters such as frequency detuning, Iprobe/Ipump, the total power of probe and pump beam. Notabl… ▽ More We report the phenomena of electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) using two identical beams in rubidium atomic vapor. The Λ-type EIT configuration is employed to examine the EIT spectrum for the D1 line in 87Rb F=2 characteristics16 by varying parameters such as frequency detuning, Iprobe/Ipump, the total power of probe and pump beam. Notably, the pump beam is also investigated in this process, which has not been previously studied. We study the effect of of the phase between the two applied fields and find that EIA and EIT can transform into each other by adjusting the relative phase. These finding may have applications in light drag or storage, optical switching, and sensing. △ Less

Submitted 28 February, 2025; originally announced February 2025.

Stable Soliton Microcomb Generation in X-cut Lithium Tantalate via Thermal-Assisted Photorefractive Suppression

Authors: Jiachen Cai, Shuai Wan, Bowen Chen, Jin Li, Xuqiang Wang, Dongchen Sui, Piyu Wang, Zhenyu Qu, Xinjian Ke, Yifan Zhu, Yang Chen, WenHui Xu, Ailun Yi, Jiaxiang Zhang, Chengli Wang, Chun-Hua Dong, Xin Ou

Abstract: Chip-based soliton frequency microcombs combine compact size, broad bandwidth, and high coherence, presenting a promising solution for integrated optical telecommunications, precision sensing, and spectroscopy. Recent progress in ferroelectric thin films, particularly thin-film Lithium niobate (LN) and thin-film Lithium tantalate (LT), has significantly advanced electro-optic (EO) modulation and s… ▽ More Chip-based soliton frequency microcombs combine compact size, broad bandwidth, and high coherence, presenting a promising solution for integrated optical telecommunications, precision sensing, and spectroscopy. Recent progress in ferroelectric thin films, particularly thin-film Lithium niobate (LN) and thin-film Lithium tantalate (LT), has significantly advanced electro-optic (EO) modulation and soliton microcombs generation, leveraging their strong third-order nonlinearity and high Pockels coefficients. However, achieving soliton frequency combs in X-cut ferroelectric materials remains challenging due to the competing effects of thermo-optic and photorefractive phenomena. These issues hinder the simultaneous realization of soliton generation and high-speed EO modulation. Here, following the thermal-regulated carrier behaviour and auxiliary-laser-assisted approach, we propose a convenient mechanism to suppress both photorefractive and thermal dragging effect at once, and implement a facile method for soliton formation and its long-term stabilization in integrated X-cut LT microresonators for the first time. The resulting mode-locked states exhibit robust stability against perturbations, enabling new pathways for fully integrated photonic circuits that combine Kerr nonlinearity with high-speed EO functionality. △ Less

Submitted 12 February, 2025; originally announced February 2025.

Comments: 8 pages, 5 figures, article

Ultrafast Coulomb blockade in an atomic-scale quantum dot

Authors: Jonas Allerbeck, Laric Bobzien, Nils Krane, S. Eve Ammerman, Daniel E. Cintron Figueroa, Chengye Dong, Joshua A. Robinson, Bruno Schuler

Abstract: Controlling electron dynamics at optical clock rates is a fundamental challenge in lightwave-driven nanoelectronics. Here, we demonstrate ultrafast charge-state manipulation of individual selenium vacancies in monolayer and bilayer tungsten diselenide (WSe$_2$) using picosecond terahertz (THz) source pulses, focused onto the picocavity of a scanning tunneling microscope (STM). Using THz pump--THz… ▽ More Controlling electron dynamics at optical clock rates is a fundamental challenge in lightwave-driven nanoelectronics. Here, we demonstrate ultrafast charge-state manipulation of individual selenium vacancies in monolayer and bilayer tungsten diselenide (WSe$_2$) using picosecond terahertz (THz) source pulses, focused onto the picocavity of a scanning tunneling microscope (STM). Using THz pump--THz probe time-domain sampling of the defect charge population, we capture atomic-scale snapshots of the transient Coulomb blockade, a signature of charge transport via quantized defect states. We identify back tunneling of localized charges to the tip electrode as a key challenge for lightwave-driven STM when probing electronic states with charge-state lifetimes exceeding the pulse duration. However, we show that back tunneling can be mitigated by the Franck-Condon blockade, which limits accessible vibronic transitions and promotes unidirectional charge transport. Our rate equation model accurately reproduces the time-dependent tunneling process across the different coupling regimes. This work builds on recent progress in imaging coherent lattice and quasiparticle dynamics with lightwave-driven STM and opens new avenues for exploring ultrafast charge dynamics in low-dimensional materials, advancing the development of lightwave-driven nanoscale electronics. △ Less

Submitted 18 December, 2024; originally announced December 2024.

Spatio-temporal Dynamical Indices for Complex Systems

Authors: Chenyu Dong, Gabriele Messori, Davide Faranda, Adriano Gualandi, Valerio Lucarini, Gianmarco Mengaldo

Abstract: Complex systems span multiple spatial and temporal scales, making their dynamics challenging to understand and predict. This challenge is especially daunting when one wants to study localized and/or rare events. Advances in dynamical systems theory, including the development of state-dependent dynamical indices, namely local dimension and persistence, have provided powerful tools for studying thes… ▽ More Complex systems span multiple spatial and temporal scales, making their dynamics challenging to understand and predict. This challenge is especially daunting when one wants to study localized and/or rare events. Advances in dynamical systems theory, including the development of state-dependent dynamical indices, namely local dimension and persistence, have provided powerful tools for studying these phenomena. However, existing applications of such indices rely on a predefined and fixed spatial domain, that provides a single scalar quantity for the entire region of interest. This aspect prevents understanding the spatially localized dynamical behavior of the system. In this work, we introduce Spatio-temporal Dynamical Indices (SDIs), that leverage the existing framework of state-dependent local dimension and persistence. SDIs are obtained via a sliding window approach, enabling the exploration of space-dependent properties in spatio-temporal data. As an example, we show that, through this framework, we are able to reconcile previously different perspectives on European summertime heatwaves. This result showcases the importance of accounting for spatial scales when performing scale-dependent dynamical analyses. △ Less

Submitted 19 September, 2025; v1 submitted 13 December, 2024; originally announced December 2024.

On-chip 7 GHz acousto-optic modulators for visible wavelengths

Authors: Ji-Zhe Zhang, Yu Zeng, Qing Qin, Yuan-Hao Yang, Zheng-Hui Tian, Jia-Qi Wang, Chun-Hua Dong, Xin-Biao Xu, Ming-Yong Ye, Guang-Can Guo, Chang-Ling Zou

Abstract: A chip-integrated acousto-optic phase modulator tailored for visible optical wavelengths has been developed. Utilizing the lithium niobate on sapphire platform, the modulator employs a 7 GHz surface acoustic wave, excited by an interdigital transducer and aligned perpendicular to the waveguide. This design achieves efficient phase modulation of visible light within a compact device length of merel… ▽ More A chip-integrated acousto-optic phase modulator tailored for visible optical wavelengths has been developed. Utilizing the lithium niobate on sapphire platform, the modulator employs a 7 GHz surface acoustic wave, excited by an interdigital transducer and aligned perpendicular to the waveguide. This design achieves efficient phase modulation of visible light within a compact device length of merely 200 microns, while holds the advantages of easy fabrication and high stability due to simple unsuspended structure. Remarkably, in this high-frequency acoustic regime, the acoustic wavelength becomes comparable to the optical wavelength, resulting in a notable single-sideband modulation behavior. This observation underscores the phase delay effects in the acousto-optics interactions, and opens up new aspects for realizing functional visible photonic devices and its integration with atom- and ion-based quantum platforms. △ Less

Submitted 23 November, 2024; originally announced November 2024.

Comments: 10 pages, 6 figures

Journal ref: Opt. Express 33, 5562-5576 (2025)

Time-Lagged Recurrence: a data-driven method to estimate the predictability of dynamical systems

Authors: Chenyu Dong, Davide Faranda, Adriano Gualandi, Valerio Lucarini, Gianmarco Mengaldo

Abstract: Nonlinear dynamical systems are ubiquitous in nature and they are hard to forecast. Not only they may be sensitive to small perturbations in their initial conditions, but they are often composed of processes acting at multiple scales. Classical approaches based on the Lyapunov spectrum rely on the knowledge of the dynamic forward operator, or of a data-derived approximation of it. This operator is… ▽ More Nonlinear dynamical systems are ubiquitous in nature and they are hard to forecast. Not only they may be sensitive to small perturbations in their initial conditions, but they are often composed of processes acting at multiple scales. Classical approaches based on the Lyapunov spectrum rely on the knowledge of the dynamic forward operator, or of a data-derived approximation of it. This operator is typically unknown, or the data are too noisy to derive its faithful representation. Here we propose a new data-driven approach to analyze the local predictability of dynamical systems. This method, based on the concept of recurrence, is closely linked to the well-established framework of local dynamical indices. When applied to both idealized systems and real-world datasets arising from large-scale atmospheric fields, our new approach proves its effectiveness in estimating local predictability. Additionally, we discuss its relationship with other local dynamical indices, and how it reveals the scale-dependent nature of predictability. Furthermore, we explore its link to information theory, its extension that includes a weighting strategy, and its real-time application. We believe these aspects collectively demonstrate its potential as a powerful diagnostic tool for complex systems. △ Less

Submitted 3 October, 2025; v1 submitted 23 September, 2024; originally announced September 2024.

Integrated photonic nonreciprocal devices based on susceptibility-programmable medium

Authors: Yan-Lei Zhang, Ming Li, Xin-Biao Xu, Zhu-Bo Wang, Chun-Hua Dong, Guang-Can Guo, Chang-Ling Zou, Xu-Bo Zou

Abstract: The switching and control of optical fields based on nonlinear optical effects are often limited to relatively weak nonlinear susceptibility and strong optical pump fields. Here, an optical medium with programmable susceptibility tensor based on polarizable atoms is proposed. Under a structured optical pump, the ground state population of atoms could be efficiently controlled by tuning the chirali… ▽ More The switching and control of optical fields based on nonlinear optical effects are often limited to relatively weak nonlinear susceptibility and strong optical pump fields. Here, an optical medium with programmable susceptibility tensor based on polarizable atoms is proposed. Under a structured optical pump, the ground state population of atoms could be efficiently controlled by tuning the chirality and intensity of optical fields, and thus the optical response of the medium is programmable in both space and time. We demonstrate the potential of this approach by engineering the spatial distribution of the complex susceptibility tensor of the medium in photonic structures to realize nonreciprocal optical effects. Specifically, we investigate the advantages of chiral interaction between atoms and photons in an atom-cladded waveguide, theoretically showing that reconfigurable, strong, and fastly switchable isolation of optical signals in a selected optical mode is possible. The susceptibility-programmable medium provides a promising way to efficiently control the optical field, opening up a wide range of applications for integrated photonic devices and structured optics. △ Less

Submitted 2 September, 2024; originally announced September 2024.

Comments: 7 pages, 4 figures

Photonic time-delayed reservoir computing based on lithium niobate microring resonators

Authors: Yuan Wang, Ming Li, Mingyi Gao, Chang-Ling Zou, Chun-Hua Dong, Xiaoniu Yang, Qi Xuan, HongLiang Ren

Abstract: On-chip micro-ring resonators (MRRs) have been proposed for constructing delay reservoir computing (RC) systems, offering a highly scalable, high-density computational architecture that is easy to manufacture. However, most proposed RC schemes have utilized passive integrated optical components based on silicon-on-insulator (SOI), and RC systems based on lithium niobate on insulator (LNOI) have no… ▽ More On-chip micro-ring resonators (MRRs) have been proposed for constructing delay reservoir computing (RC) systems, offering a highly scalable, high-density computational architecture that is easy to manufacture. However, most proposed RC schemes have utilized passive integrated optical components based on silicon-on-insulator (SOI), and RC systems based on lithium niobate on insulator (LNOI) have not yet been reported. The nonlinear optical effects exhibited by lithium niobate microphotonic devices introduce new possibilities for RC design. In this work, we design an RC scheme based on a series-coupled MRR array, leveraging the unique interplay between thermo-optic nonlinearity and photorefractive effects in lithium niobate. We first demonstrate the existence of three regions defined by wavelength detuning between the primary LNOI micro-ring resonator and the coupled micro-ring array, where one region achieves an optimal balance between nonlinearity and high memory capacity at extremely low input energy, leading to superior computational performance. We then discuss in detail the impact of each ring's nonlinearity and the system's symbol duration on performance. Finally, we design a wavelength-division multiplexing (WDM) based multi-task parallel computing scheme, showing that the computational performance for multiple tasks matches that of single-task computations. △ Less

Submitted 24 August, 2024; originally announced August 2024.

Comments: 17 pages, 6 figures