Showing 1–50 of 140 results for author: Ren, Z

Wafer-scale monolithic integration of Ce:YIG films and magneto-optical isolators on silicon

Authors: Tianchi Zhang, Yucong Yang, Weihao Yang, JieJun Su, Tianyi Ma, Xuan Zhao, Junxian Wang, Di Wu, Zhenyuan Ren, Yi Shuai, Zixuan Wei, Lei Bi

Abstract: Silicon integrated cerium doped yttrium iron garnet (Ce:YIG) thin films are promising candidates for integrated nonreciprocal photonic devices, cryogenic photonic modulators and optical computing applications. However, previously reported Ce:YIG thin film on silicon is limited to milimeter sizes. Wafer-scale integration and non-destructive characterization of high quality Ce:YIG thin films on sili… ▽ More Silicon integrated cerium doped yttrium iron garnet (Ce:YIG) thin films are promising candidates for integrated nonreciprocal photonic devices, cryogenic photonic modulators and optical computing applications. However, previously reported Ce:YIG thin film on silicon is limited to milimeter sizes. Wafer-scale integration and non-destructive characterization of high quality Ce:YIG thin films on silicon has been elusive. Here, we report growth of 4-inch wafer-scale Ce:YIG thin films on silicon substrates by radio-frequency magnetron sputtering. Strong Faraday effect of 2318 deg/cm, low propagation loss of 80 dB/cm and excellent thickness uniformity of 3.5% is demonstrated across the 4-inch silicon wafer. Furthermore, a custom designed wafer-scale, non-destructive magneto-ellipsometry was established to characterize the film thickness, optical constants and magneto-optical constants across the wafer. Wafer-scale integration of ring resonator type magneto-optical isolators are also demonstrated. Our work demonstrates a step forward toward wafer-scale heterogeneous integration and characterization of magneto-optical thin films on silicon, providing material candidates for non-reciprocal photonic device arrays, magneto-optical in-memory computing networks and integrated magneto-optic magnetometers. △ Less

Submitted 9 August, 2026; originally announced August 2026.

Atomic oven with rapid thermal response for atom experiments

Authors: Weilong Huang, Congjun Zou, Feiyu Dong, Huirong Xiao, Zejian Ren, Shanchao Zhang

Abstract: Atomic oven generating controllable atomic beam flux plays a fundamental role in quantum gas experiments. Here, we report a new heater design that can heat up an high temperature atomic oven with fast thermal response. The new heater shows a heating rate improved by 7.65 times comparing to that of the conventional resistive heater while the crucible temperature can heated up to 1200K. With this ov… ▽ More Atomic oven generating controllable atomic beam flux plays a fundamental role in quantum gas experiments. Here, we report a new heater design that can heat up an high temperature atomic oven with fast thermal response. The new heater shows a heating rate improved by 7.65 times comparing to that of the conventional resistive heater while the crucible temperature can heated up to 1200K. With this oven, we generated a collimated ytterbium beam with flux exceeding $10^{14} \text{ atoms/s}$ at 823 K. We believe that our design offers a promising solution for shortening experimental dead time and improve the experiment efficiency in cold atom researches. △ Less

Submitted 7 July, 2026; v1 submitted 5 July, 2026; originally announced July 2026.

Comments: 5 pages, 4 figures

Unlocking Cryogenic Energy Storage by Constructing Dipole Glass with Unit-cell-level Polar Disorder

Authors: Yangyang Si, Denan Li, Yijie Li, Changsheng Chen, Jingxuan Li, Chao Zhou, Hao Xiong, Tianfu Zhang, Wenjin Liao, Zhongqi Ren, Huaicheng Yuan, Dong Li, Jing-Kai Qin, Cheng-Yan Xu, Ye Zhu, Yunlong Tang, Sujit Das, Jieun Kim, Junling Wang, Hao Pan, Fei Li, Zhen Chen, Shi Liu, Zuhuang Chen

Abstract: Cryogenic energy storage is vital for frontier technologies including deep-space exploration and quantum computing, yet conventional electrochemical energy systems fail below ~230 K due to frozen ion migration. While relaxor-based dielectric capacitors provide high efficiency at room temperature, the intrinsic freezing/growth of polar nanodomains at extended cryogenic regime limits their applicati… ▽ More Cryogenic energy storage is vital for frontier technologies including deep-space exploration and quantum computing, yet conventional electrochemical energy systems fail below ~230 K due to frozen ion migration. While relaxor-based dielectric capacitors provide high efficiency at room temperature, the intrinsic freezing/growth of polar nanodomains at extended cryogenic regime limits their applications with deteriorated hysteresis losses. Here, we realize superior cryogenic energy-storage performance by designing unit-cell-level disordered dipole-glass state in Pb0.6Sr0.4ZrO3 thin films with composition near antiferroelectric-paraelectric phase boundary. The antiferroelectric-derived dipole-glass introduces enhanced unit-cell-level complexity of dipole interaction that suppresses long-range ferroelectric order. This enables ultralow-hysteresis operation (efficiency > 88%) down to 4 K, delivering record-high energy density (211 J/cm^3) at 9 MV/cm, stability over 10^8 charge/discharge cycles and microsecond-scale charge/discharge capability. This work establishes a dipole-glass paradigm for cryogenic dielectric capacitors, opening a new avenue to highly-efficient energy-storage systems with broad applications in frontier nanoelectronics. △ Less

Submitted 26 June, 2026; originally announced June 2026.

Comments: 23 pages, 4 figures

Hyperon-Nucleon Spectrometer

Authors: Xiaozhi Bai, Xu Cao, Zhe Cao, Jinhui Chen, Kai Chen, Qibo Chen, Shi Chen, Xin Chen, Yuquan Chen, Zhenyu Chen, Jianping Dai, Heng-Tong Ding, Dongshuo Du, Shuxian Du, Limin Duan, Zhe Duan, Anhui Feng, Jie Feng, Yicheng Feng, Jinlin Fu, Xiaofeng Fu, Chaosong Gao, Liang Ge, Wenwen Ge, Lisheng Geng , et al. (215 additional authors not shown)

Abstract: Chirality lies at the heart of low-energy QCD, governing the symmetry structure that shapes hadron masses and strong interaction dynamics. Among the most compelling open questions tied to chiral dynamics and spontaneous chiral symmetry breaking is the longstanding $Λ$ polarization puzzle, in which $Λ$ hyperons produced in unpolarized hadronic collisions exhibit a surprisingly large transverse pola… ▽ More Chirality lies at the heart of low-energy QCD, governing the symmetry structure that shapes hadron masses and strong interaction dynamics. Among the most compelling open questions tied to chiral dynamics and spontaneous chiral symmetry breaking is the longstanding $Λ$ polarization puzzle, in which $Λ$ hyperons produced in unpolarized hadronic collisions exhibit a surprisingly large transverse polarization that remains theoretically unexplained. This whitepaper presents the proposal for the Hyperon-Nucleon Spectrometer (H-NS) at the High-Intensity heavy-ion Accelerator Facility (HIAF). Leveraging the high energy and high intensity of HIAF's proton and heavy-ion beams, the H-NS experiment will perform systematic studies of hyperon polarization phenomena and their underlying mechanisms in proton-proton ($pp$), proton-nucleus ($pA$), and nucleus-nucleus ($AA$) collisions in the fixed target mode. A wide-range beam energy scan, including proton beams from 3 GeV up to 9.3 GeV (HIAF) and up to 32 GeV (upgraded HIAF), will be conducted to examine the dependence of polarization on collision energy. The spectrometer is designed with specialized detectors capable of high-precision reconstruction of final-state baryon polarizations. Among its many interesting and important measurements, H-NS will simultaneously measure hyperon and proton spin observables to explore the polarization mechanism in hadronic interactions and the spin structure of baryons. Furthermore, the use of $pA$ and $AA$ collisions will enable detailed investigations of cold and hot nuclear matter effects on spin polarization. Its physics program and detector development will significantly benefit the future Electron-ion Collider in China. △ Less

Submitted 4 June, 2026; originally announced June 2026.

Comments: 69 pages, Hyperon-Nucleon Spectrometer (H-NS) white paper

Advances in laser-assisted nuclear decay and nuclear excitation

Authors: Q. Xiao, J. H. Cheng, Y. Y. Xu, Y. T. Zou, Z. Z. Ren, A. Ya. Dzyublik, T. P. Yu

Abstract: From the synthesis and evolution of the elements to the celestial nuclear processes of stellar explosions and neutron star mergers, nuclear physics is the foundation of our understanding of the universe. After more than a century of progress, the field of nuclear physics remains vibrant. The rapid advancement of laser technology has opened unprecedented avenues in nuclear physics, driven by the in… ▽ More From the synthesis and evolution of the elements to the celestial nuclear processes of stellar explosions and neutron star mergers, nuclear physics is the foundation of our understanding of the universe. After more than a century of progress, the field of nuclear physics remains vibrant. The rapid advancement of laser technology has opened unprecedented avenues in nuclear physics, driven by the interdisciplinary convergence of laser physics, nuclear structure, plasma science, and quantum dynamics. This emerging field enables studies on laser-induced nuclear excitation, laser assisted nuclear decay, and precision manipulation of nuclear isomers for optical clocks. This review comprehensively examines the research achievements over the past decade regarding the influence of lasers on radioactive charged particle emissions and nuclear excitation. Regarding theoretical developments, the review details various methods used to evaluate the interactions between lasers and nuclei, including the time-dependent Schrödinger equation for $α$ decay, proton radioactivity, and two-proton radioactivity and Fermi's golden rule for nuclear excitation as well as the application and advancement of various theoretical models and approximation methods. In experimental research, the review synthesizes significant breakthroughs in laser induced nuclear excitation experiments, particularly emphasizing the excitation of the $^{229}$Th, $^{83}$Kr, and $^{45}$Sc. These achievements provide essential groundwork for future breakthroughs in both fundamental nuclear science and its broader technological applications. △ Less

Submitted 15 May, 2026; originally announced May 2026.

Fast and Accurate Prediction of Lattice Thermal Conductivity via Machine Learning Surrogates

Authors: Zeyu Wang, Shuya Yamazaki, Martin Hoffmann Petersen, Masato Ohnishi, Tomiya Yamamoto, Wei Nong, Jianghai Wang, Ruiming Zhu, Masatoshi Hanai, Michimasa Morita, Toyotaro Suzumura, Zekun Ren, Junichiro Shiomi, Kedar Hippalgaonkar

Abstract: The appearance of generative models has opened vast chemical spaces in the design of functional materials. Although machine learning interatomic potentials (MLIPs) have substantially accelerated phonon calculations, high-fidelity prediction of lattice thermal conductivity \k{appa}lat still requires accurate treatment of anharmonic interactions, which remains a key challenge for existing potentials… ▽ More The appearance of generative models has opened vast chemical spaces in the design of functional materials. Although machine learning interatomic potentials (MLIPs) have substantially accelerated phonon calculations, high-fidelity prediction of lattice thermal conductivity \k{appa}lat still requires accurate treatment of anharmonic interactions, which remains a key challenge for existing potentials across novel chemical spaces. To address this challenge, we present a comprehensive benchmark of 15 surrogate models for predicting \k{appa}lat using the Phonix database, which contains 6,966 entries with anharmonic phonon properties derived from first-principles calculations. Firstly, We categorize these surrogate models into three distinct groups: Physical-informed feature descriptors combined with ML models, end-to-end deep neural networks, and pre-trained MLIP-embeddings combined with ML models. By evaluating model performance across random, space-group disjoint (testing generalization to unseen crystal symmetries), and Out-Of-Distribution splits (OOD dataset that testing extrapolation to property regimes beyond the training range) based on \k{appa}lat, we probe both interpolation and exploration capabilities. Our results reveal that MLIP-embedded models excel in interpolation within well-sampled regions, deep neural network models especially ALiEGNN demonstrate superior robustness in OOD regimes critical for discovering novel low-\k{appa}lat. Additionally, we find a systematic degradation in performance when the structural representation is reduced. Although surrogate models exhibit lower accuracy than direct simulations using first-principles calculation, they reduce computational costs by orders of magnitude, enabling efficient high-throughput screening of thermoelectric materials with minimal loss in generative design workflows. △ Less

Submitted 12 May, 2026; originally announced May 2026.

Exceptional Optical Phonon Coherence in Enriched Cubic Boron Arsenide via Suppression of Three-Phonon Scattering

Authors: Tong Lin, Fengjiao Pan, Gaihua Ye, Sanjna Sukumaran, Cynthia Nnokwe, Ange Benise Niyikiza, William A. Smith, Stephen B. Bayne, Rui He, Zhifeng Ren, Hanyu Zhu

Abstract: Cubic boron arsenide (BAs) is a promising semiconductor for next-generation electronics due to its outstanding ambipolar mobility and thermal conductivity, the latter of which is attributed to the suppression of three-phonon scattering. However, precisely accounting for different high-order anharmonic scattering processes is challenging from both theory and experiment, so that questions remain ope… ▽ More Cubic boron arsenide (BAs) is a promising semiconductor for next-generation electronics due to its outstanding ambipolar mobility and thermal conductivity, the latter of which is attributed to the suppression of three-phonon scattering. However, precisely accounting for different high-order anharmonic scattering processes is challenging from both theory and experiment, so that questions remain open regarding the ultimate limit of phonon lifetime and thermal conductivity in BAs. Here we show that this gap nearly eliminates three-phonon scattering for zone-center optical phonons in a wide temperature range, leading to a record-high, isotope purity-limited phonon coherence with a quality factor above $3.7\times 10^3$ for >98% enriched $^{11}$BAs below 100 K. We discriminate three decoherence mechanisms by their temperature-dependent contribution to the damping rate using high-resolution Raman and Fourier transform infrared spectroscopy. For the as-synthesized crystals, we find that defect scattering has negligible contributions to the linewidth of optical phonons in comparison to isotope scattering. These results provide critical insights into the intrinsic and extrinsic scattering mechanisms of optical phonons in BAs, motivating further studies to quantify anharmonic effects and realize superior phonon transport. △ Less

Submitted 11 March, 2026; originally announced March 2026.

Journal ref: Phys. Rev. Lett. 136, 116903 (2026)

Global versus regional internal--external potential field separation

Authors: X. Huang, C. Gerhards, Z. Ren

Abstract: Internal--external field separation is crucial for many aspects of geomagnetism, aiming at distinguishing contributions of the magnetic field generated within a given observation surface from those generated in the exterior. When data are available on a full spherical observation surface, this separation is a standard, stable, and widely used procedure dating back to Gauss. However, when data are… ▽ More Internal--external field separation is crucial for many aspects of geomagnetism, aiming at distinguishing contributions of the magnetic field generated within a given observation surface from those generated in the exterior. When data are available on a full spherical observation surface, this separation is a standard, stable, and widely used procedure dating back to Gauss. However, when data are only available in a subdomain of the observation surface (as is the case for aeromagnetic and ground-based surveys), the situation drastically changes. Here we show that, without prior assumptions, an internal--external field separation is not uniquely possible. Given the geophysically reasonable assumption that the exterior sources, e.g., magnetospheric and ionospheric current systems, are located above a source-free spherical shell, we show that a unique separation becomes possible but that it is highly unstable. The results are based on the spherical Hardy--Hodge decomposition and explain the intrinsic difficulties of regional data-based internal--external potential field separation. △ Less

Submitted 7 July, 2026; v1 submitted 5 March, 2026; originally announced March 2026.

Aeroacoustic signatures reveal fast transient dynamics of vapor-jet-driven cavity oscillations in metallic additive manufacturing

Authors: Haolin Liu, S. Kiana Naghibzadeh, Zhongshu Ren, Yanming Zhang, Jiayun Shao, Samuel J. Clark, Kamel Fezzaa, Xuzhe Zeng, Lin Gao, Wentao Yan, Noel Walkington, Kaushik Dayal, Tao Sun, Anthony D. Rollett, Levent Burak Kara

Abstract: Aeroacoustic emissions from intense evaporation are widely measured yet often treated as noisy byproducts and used mainly in empirical monitoring. Here, we show that airborne sound encodes physics-governed sub-millisecond fingerprints of vapor-jet dynamics in excessive vaporization, exemplified by vapor keyholes in laser metal processing. From first principles, we develop a vapor-jet-cavity oscill… ▽ More Aeroacoustic emissions from intense evaporation are widely measured yet often treated as noisy byproducts and used mainly in empirical monitoring. Here, we show that airborne sound encodes physics-governed sub-millisecond fingerprints of vapor-jet dynamics in excessive vaporization, exemplified by vapor keyholes in laser metal processing. From first principles, we develop a vapor-jet-cavity oscillation framework and incorporate it into an aeroacoustic formulation, thereby coupling measured sound to transient cavity depth and oscillation frequency. Reconciled with synchronized multimodal in-situ data, airborne acoustics enable accurate tracking of vapor-cavity properties within tens to hundreds of microseconds. Combined with newly discovered correlations, cavity-jet-acoustic theory recasts the transition from steady, pore-free to pore-shedding vaporizations as a critical-frequency event. Aeroacoustic emissions thus become scalable, physics-guided, and cost-efficient probes of rapidly evolving liquid-vapor systems. △ Less

Submitted 5 March, 2026; v1 submitted 28 February, 2026; originally announced March 2026.

Comments: 35 pages 5 figures

Device-independent quantum key distribution over 100 km with single atoms

Authors: Bo-Wei Lu, Chao-Wei Yang, Run-Qi Wang, Bo-Feng Gao, Yi-Zheng Zhen, Zhen-Gang Wang, Jia-Kai Shi, Zhong-Qi Ren, Thomas A. Hahn, Ernest Y. -Z. Tan, Xiu-Ping Xie, Ming-Yang Zheng, Xiao Jiang, Jun Zhang, Feihu Xu, Qiang Zhang, Xiao-Hui Bao, Jian-Wei Pan

Abstract: Device-independent quantum key distribution (DI-QKD) is a key application of the quantum internet. We report the realization of DI-QKD between two single-atom nodes linked by 100-km fibers. To improve the entangling rate, single-photon interference is leveraged for entanglement heralding, and quantum frequency conversion is used to reduce fiber loss. A tailored Rydberg-based emission scheme suppre… ▽ More Device-independent quantum key distribution (DI-QKD) is a key application of the quantum internet. We report the realization of DI-QKD between two single-atom nodes linked by 100-km fibers. To improve the entangling rate, single-photon interference is leveraged for entanglement heralding, and quantum frequency conversion is used to reduce fiber loss. A tailored Rydberg-based emission scheme suppresses the photon recoil effect on the atom without introducing noise. We achieved high-fidelity atom-atom entanglement and positive asymptotic key rates for fiber lengths up to 100 km. At 11 km, 1.2 million heralded Bell pairs were prepared over 624 hours, yielding an estimated extractable finite-size secure key rate of 0.112 bits per event against general attacks. Our results close the gap between proof-of-principle quantum network experiments and real-world applications. △ Less

Submitted 10 February, 2026; originally announced February 2026.

Comments: This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution

Journal ref: Science 391, 592-597 (2026)

Coherent Mode Decoupling: A Versatile Framework for High-Throughput Partially Coherent Light Transport

Authors: Han Xu, Ming Li, Shuo Wang, Zhe Ren, Peng Liu, Yi Zhang, Yuhui Dong, Liang Zhou

Abstract: Accurate and efficient wave-optics simulation of partially coherent light transport systems is critical for the design of advanced optical systems, ranging from computational lithography to diffraction-limited storage rings (DLSR). However, traditional approaches based on Coherent Mode Decomposition suffer from high computational costs due to the propagating massive sets of two-dimensional modes.… ▽ More Accurate and efficient wave-optics simulation of partially coherent light transport systems is critical for the design of advanced optical systems, ranging from computational lithography to diffraction-limited storage rings (DLSR). However, traditional approaches based on Coherent Mode Decomposition suffer from high computational costs due to the propagating massive sets of two-dimensional modes. In this paper, we propose the Coherent Mode Decoupling (CMDC) algorithm, a high-throughput computational framework designed to accelerate these simulations by orders of magnitude without compromising physical fidelity. The method factorizes 2D modes into efficient one-dimensional (1D) components, while crucially incorporating a subspace compression strategy to capture non-separable coupling effects. We demonstrated the generality and robustness of this framework in applications ranging from computational lithography to coherent beamlines of DLSR. △ Less

Submitted 22 January, 2026; originally announced January 2026.

Second- and Third-Harmonic Backscatter Through a Bandstop Filter Using Defected Ground Structure

Authors: Dan Che, Changjun Liu, Haoming He, Zhi Hua Ren, Pengde Wu

Abstract: In this brief, a novel harmonic-backscatter-rectifier (HBR) is introduced for simultaneous rectification and harmonic-based uplink. The proposed (HBR) employs a rectifier to generate both DC power and the harmonic carriers for backscattering communication, and a dual-band reconfigurable band-stop filter using defected ground structure(DGS) to modulate the second and third harmonics with low-power… ▽ More In this brief, a novel harmonic-backscatter-rectifier (HBR) is introduced for simultaneous rectification and harmonic-based uplink. The proposed (HBR) employs a rectifier to generate both DC power and the harmonic carriers for backscattering communication, and a dual-band reconfigurable band-stop filter using defected ground structure(DGS) to modulate the second and third harmonics with low-power consumption and same input impedance at f0 all the time. As a proof of concept, an HBR prototype operating at 1.85 GHz was designed and experimented. An uplink data rate of 8Mbps (4Mbps x 2 ) was achieved when the HBR was fed with -10 dBm RF power, and the data modulation consumed less than 27.7pJ/bit. In addition, a passive harmonic tag was implemented with the proposed HBR and a low-power binary sequence generator, which demonstrated a continuous uplink of 12 kbps at -6 dBm RF power. △ Less

Submitted 17 January, 2026; originally announced January 2026.

Journal ref: IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 70, no. 11, pp. 4171-4175, Nov. 2023

Harmonic-Recycling Rectification Based on Novel Compact Dual-Band Resonator

Authors: Pengde Wu, Hao Wu, Yi-Dan Chen, Zhi Hua Ren, Yuhua Cheng, Changjun Liu

Abstract: Harmonic generation during radio frequency (RF)-dc conversion causes performance degradation of a microwave rectifying circuit. To suppress and recycle the harmonic power, this letter proposes a novel compact dual-band resonator (DBR) based on a microstrip coupled transmission line. It presents open-circuits at the second and third harmonic frequencies, which effectively block the higher order har… ▽ More Harmonic generation during radio frequency (RF)-dc conversion causes performance degradation of a microwave rectifying circuit. To suppress and recycle the harmonic power, this letter proposes a novel compact dual-band resonator (DBR) based on a microstrip coupled transmission line. It presents open-circuits at the second and third harmonic frequencies, which effectively block the higher order harmonic for power recycling. The conventional input cascading filters for harmonic rejection can be eliminated, simplifying the circuit topology and reducing loss. Theoretical analyses were carried out and corresponding equations were formulated for the proposed DBR. For validation, two rectifying circuits with/without the DBR operating at 2.2 GHz were fabricated and tested. Using the proposed DBR at 10 dBm RF power, the suppression of the second and third harmonic powers is enhanced by 18.4 and 7.6 dB, respectively. Besides, an improvement of RF-dc power conversion efficiency (PCE) was observed; specifically, PCE reached 73.2% at 10 dBm compared to 71.6% obtained from an equivalent rectifier. △ Less

Submitted 4 January, 2026; originally announced January 2026.

Journal ref: IEEE Microwave and Wireless Technology Letters, vol. 35, no. 5, pp. 553-556, May 2025

Benchmark for Non-reciprocal Attack Detection on Synchronization

Authors: Zishuo Ren, Yiting Lin, Yufei Zhang, Yang Li, Ziyang Chen, Hong Guo

Abstract: A precise and secure time synchronization is the backbone of both fundamental physics and advanced technologies. Despite ultra-high precision, security, particularly the unresolved vulnerabilities on physical links beyond traditional cryptography, remains the bottleneck. Here, we develop an analysis framework, the Benchmark Attack Noise Detection (BAND) model, to quantify the security of the high-… ▽ More A precise and secure time synchronization is the backbone of both fundamental physics and advanced technologies. Despite ultra-high precision, security, particularly the unresolved vulnerabilities on physical links beyond traditional cryptography, remains the bottleneck. Here, we develop an analysis framework, the Benchmark Attack Noise Detection (BAND) model, to quantify the security of the high-precision time synchronization when its core assumption, reciprocity, is broken. The model characterizes non-reciprocal attacks through a unified metric, termed attack intensity. Based on the analysis of attack intensity, we accurately predict both instantaneous and accumulating attacks in a 100-km dual-comb two-way time-transfer system. Beyond security considerations, we find that the BAND model can explain intrinsic fiber noise and delay-unsuppressed noise naturally, offering an effective tool to establish an environment-sensitive link model. This work paves the way for a secure large-scale integrated time, sensing and communication networks. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Comments: 13 pages, 6 figures

When Energy and Information Revolutions Meet 2D Janus

Authors: Long Zhang, Ziqi Ren, Li Sun, Yihua Gao, Deli Wang, Junjie He, Guoying Gao

Abstract: The depletion of energy sources, worsening environmental issues, and the quantum limitations of integrated circuits for information storage in the post-Moore era, are pressing global concerns. Fortunately, two-dimensional (2D) Janus materials, possessing broken spatial symmetry, with emerging pressure-dependent and non-linear optical response, piezoelectricity, valley polarization, Rashba spin spl… ▽ More The depletion of energy sources, worsening environmental issues, and the quantum limitations of integrated circuits for information storage in the post-Moore era, are pressing global concerns. Fortunately, two-dimensional (2D) Janus materials, possessing broken spatial symmetry, with emerging pressure-dependent and non-linear optical response, piezoelectricity, valley polarization, Rashba spin splitting and more, have established a substantial platform for exploring and applying modifiable physical, chemical and biological properties in material science and offered a promising solution for these energy and information issues. To furnish researchers with a comprehensive repository of 2D Janus family, this review systematically summarizes their theoretical predictions, experimental preparations, and modulation strategies. It also retrospectively outlines the recent advances in modifiable properties, applications, and inherent mechanisms in optics, catalysis, piezoelectricity, electrochemistry, thermoelectricity, magnetism, and electronics, with a focus on experimentally realized hexagonal and trigonal Janus structures. Additionally, their current research state is summarized, and potential opportunities and challenges that may arise are highlighted. Overall, this review aims to serve as a valuable resource for designing, fabricating, regulating, and applying 2D Janus systems, both theoretically and experimentally. This review will strongly promote the advanced academic investigations and industrial applications of 2D Janus materials in energy and information fields. △ Less

Submitted 23 December, 2025; v1 submitted 29 August, 2025; originally announced August 2025.

Comments: 126 pages, 21 figures, and 7 tables

Journal ref: Applied Physics Reviews, 2025, 12, 041329

Hydrodynamic Insight Drives Multimodal Light_Field Dynamics via Streamline Engineering

Authors: Wenxiang Yan, Zheng Yuan, Yuan Gao, Zhaozhong Chen, Zhi-Cheng Ren, Xi-Lin Wang, Jianping Ding, Hui-Tian Wang

Abstract: Since the 1970s, analogies between laser dynamics and fluid systems have provided insight into phenomena such as chaos, multistability, and turbulence. Building on this perspective, we model the optical field as an energy fluid and interpret Poynting-vector trajectories as energy streamlines, yielding a unified, three_dimensional map of light's free-space dynamics. By sculpting these streamlines,… ▽ More Since the 1970s, analogies between laser dynamics and fluid systems have provided insight into phenomena such as chaos, multistability, and turbulence. Building on this perspective, we model the optical field as an energy fluid and interpret Poynting-vector trajectories as energy streamlines, yielding a unified, three_dimensional map of light's free-space dynamics. By sculpting these streamlines, we develop an approach to talior vortex-beam propagation dynamics that suppresses both diffraction- and OAM-induced broadening. Extending this method to general structured modes, we enable a single field to exhibit customizable multimodal dynamics that integrate features from primary structured light families: the diffraction-free, self-healing behavior of Bessel beams; the tunable self-similarity of Laguerre-Gaussian beams and adjustable self-acceleration of Airy beams. Additionally, it allows for adjustable propagating energy-density profiles to counteract losses. Optical-tweezer experiments,analogous to particle-tracking velocimetry in fluid dynamics, show that trapped microspheres closely follow the designed streamlines, validating the streamline geometries and indicating a potential route toward precision 3D optomechanical control. In a proof-of-principle free-space communication experiment, vortex beams with customized multimodal dynamics demonstrate several improvements, including more independent channels, reduced turbulence-induced mode scattering, and robust non-line-of-sight transmission. Together, the streamline-engineering approach offers a unified and adaptable strategy for tailoring light's propagation dynamics, with potential applications in precision optomechanics, optofluidics, and advanced optical networking. △ Less

Submitted 27 July, 2025; v1 submitted 10 July, 2025; originally announced July 2025.

Room temperature spin injection into commercial VCSELs at non-resonant wavelengths

Authors: Timur Almabetov, Petros Androvitsaneas, Zhongze Ren, Andrew Young, Ruth Oulton, Edmund Harbord

Abstract: Spin lasers leverage electron spin-polarisation to control photon polarisation, offering the potential for lower thresholds, rapid modulation, and all-optical data processing. We report successful spin injection into a commercial Vertical Cavity Surface Emitting Laser (VCSEL) using optical pumping at wavelengths of 794 nm and 810 nm. Maximum circular polarisation achieved was about 20% at 794 nm,… ▽ More Spin lasers leverage electron spin-polarisation to control photon polarisation, offering the potential for lower thresholds, rapid modulation, and all-optical data processing. We report successful spin injection into a commercial Vertical Cavity Surface Emitting Laser (VCSEL) using optical pumping at wavelengths of 794 nm and 810 nm. Maximum circular polarisation achieved was about 20% at 794 nm, whereas this falls to 5% with exciting at 810 nm. We attribute this to reduced spin injection due to the longer excitation wavelength in line with previous measurements on quantum wells under optical orientation. We extend the Spin-Flip Model (SFM) to account for realistic excitation conditions and find our theoretical analysis accurately reproduces experimental trends. △ Less

Submitted 27 October, 2025; v1 submitted 23 June, 2025; originally announced June 2025.

Comments: 6 pages, 4 figures, 1 table, under submission

Journal ref: Semiconductor Science and Technology, 40 115016 (2025)

Controlling Enhancement of Transmitted Goos-Hänchen Shifts: From Symmetric to Unidirectional

Authors: Zhuolin Wu, Weiming Zhen, Zhi-Cheng Ren, Xi-Lin Wang, Hui-Tian Wang, Jianping Ding

Abstract: Since the discovery of the Goos-Hänchen (GH) shift in the 1940s, its deep connections to Fourier transforms and causality have led to widespread interest and applications in optics, acoustics, and quantum mechanics. Control of the shift involves both its magnitude and direction. Although resonance-enhanced GH shift under reflection has significantly expanded and facilitated its observation and app… ▽ More Since the discovery of the Goos-Hänchen (GH) shift in the 1940s, its deep connections to Fourier transforms and causality have led to widespread interest and applications in optics, acoustics, and quantum mechanics. Control of the shift involves both its magnitude and direction. Although resonance-enhanced GH shift under reflection has significantly expanded and facilitated its observation and application, implementations in transmission scenarios remain scarce. More importantly, discussions on the direction of the GH shift are rare, and the associated degree of freedom for controlling directional asymmetry has not been fully explored. To address these issues, we discuss a control framework for enhancing transmitted GH shifts from symmetric to asymmetric. A design with complete degrees of freedom from symmetric shift enhancement to unidirectional shift enhancement is demonstrated in transmission scenarios. The control dimension associated with directionality significantly enhances the flexibility of beam shift control, with broad application prospects in scenarios such as high-sensitivity sensing, precision measurement, optical isolators, and asymmetric optical switches. △ Less

Submitted 20 June, 2025; originally announced June 2025.

Comments: 31 pages, 10 figures. Note: This work was submitted to Laser & Photonics Reviews on June 5, 2025 (manuscript ID: lpor.202501398)

Temperature- and charge carrier density-dependent electronic response in methylammonium lead iodide

Authors: Jiacheng Wang Jungmin Park, Lei Gao, Lucia Di Virgilio, Sheng Qu, Heejae Kim, Hai I. Wang, Li-Lin Wu, Wen Zeng, Mischa Bonn, Zefeng Ren, Jaco J. Geuchies

Abstract: Understanding carrier dynamics in photoexcited metal-halide perovskites is key for optoelectronic devices such as solar cells (low carrier densities) and lasers (high carrier densities). Trapping processes at low carrier densities and many-body recombination at high densities can significantly alter the dynamics of photoexcited carriers. Combining optical-pump/THz probe and transient absorption sp… ▽ More Understanding carrier dynamics in photoexcited metal-halide perovskites is key for optoelectronic devices such as solar cells (low carrier densities) and lasers (high carrier densities). Trapping processes at low carrier densities and many-body recombination at high densities can significantly alter the dynamics of photoexcited carriers. Combining optical-pump/THz probe and transient absorption spectroscopy we examine carrier responses over a wide density range (10^14-10^19 cm-3) and temperatures (78-315K) in the prototypical methylammonium lead iodide perovskite. At densities below ~10^15 cm-3 (room temperature, sunlight conditions), fast carrier trapping at shallow trap states occurs within a few picoseconds. As excited carrier densities increase, trapping saturates, and the carrier response stabilizes, lasting up to hundreds of picoseconds at densities around ~10^17 cm-3. Above 10^18 cm-3 a Mott transition sets in: overlapping polaron wavefunctions lead to ultrafast annihilation through an Auger recombination process occurring over a few picoseconds. We map out trap-dominated, direct recombination-dominated, and Mott-dominated density regimes from 78-315 K, ultimately enabling the construction of an electronic phase diagram. These findings clarify carrier behavior across operational conditions, aiding material optimization for optoelectronics operating in the low (e.g. photovoltaics) and high (e.g. laser) carrier density regimes. △ Less

Submitted 24 May, 2025; originally announced May 2025.

Comments: 22 pages, 17 figures

Thermal Conductivity above 2000 W/m.K in Boron Arsenide by Nanosecond Transducer-less Time-Domain Thermoreflectance

Authors: Hong Zhong, Ying Peng, Feng Lin, Ange Benise Niyikiza, Fengjiao Pan, Chengzhen Qin, Jinghong Chen, Viktor G. Hadjiev, Liangzi Deng, Zhifeng Ren, Jiming Bao

Abstract: Cubic boron arsenide (c-BAs) has been theoretically predicted to exhibit thermal conductivity \k{appa} comparable to that of diamond, yet experimental measurements have plateaued at ~1300W/mK. We report room-temperature \k{appa} exceeding 2000W/mK in c-BAs, on par with single-crystal diamond. This finding is enabled by high-quality single crystals and a newly developed nanosecond, transducer-less… ▽ More Cubic boron arsenide (c-BAs) has been theoretically predicted to exhibit thermal conductivity \k{appa} comparable to that of diamond, yet experimental measurements have plateaued at ~1300W/mK. We report room-temperature \k{appa} exceeding 2000W/mK in c-BAs, on par with single-crystal diamond. This finding is enabled by high-quality single crystals and a newly developed nanosecond, transducer-less time-domain thermoreflectance technique that allows spatial mapping of \k{appa} without metal transducers. Thermal conductivity correlates with crystal quality, as evidenced by stronger photoluminescence and longer photoluminescence lifetimes. However, the observed nanosecond lifetimes remain shorter than expected for an indirect bandgap semiconductor, suggesting room for further crystal quality improvement and higher \k{appa}. These results challenge current theoretical models and highlight c-BAs as a promising material for next-generation electronics. △ Less

Submitted 23 May, 2025; originally announced May 2025.

Comments: 14 pages, 4 figures

Thermal conductivity of boron arsenide above 2100 watts per meter per Kelvin at room temperature

Authors: Ange Benise Niyikiza, Zeyu Xiang, Fanghao Zhang, Fengjiao Pan, Chunhua Li, David Broido, Ying Peng, Bolin Liao, Zhifeng Ren

Abstract: Boron arsenide (BAs) single crystals had been previously reported to have thermal conductivity of 1500 W/mK at room temperature. Now we achieved thermal conductivity above 2100 W/mK at room temperature in BAs crystals due to much lower concentration of impurities Si, C, and O grown from purified arsenic. We also observed a T-1.8 dependence of the thermal conductivity, suggesting a more significant… ▽ More Boron arsenide (BAs) single crystals had been previously reported to have thermal conductivity of 1500 W/mK at room temperature. Now we achieved thermal conductivity above 2100 W/mK at room temperature in BAs crystals due to much lower concentration of impurities Si, C, and O grown from purified arsenic. We also observed a T-1.8 dependence of the thermal conductivity, suggesting a more significant contribution from four-phonon scatterings than suggested by previous theory. We found that our experimental result can be fit with a modified theoretical calculation by tuning down the three-phonon scattering for phonons in the 4-8 THz range, although current phonon transport theory cannot provide a physical explanation. Such an advance will not only attract more effort on growing BAs single crystals and studying their practical applications but also stimulate theoretical work to predict more materials with possibly even higher thermal conductivities. △ Less

Submitted 20 May, 2025; originally announced May 2025.

Comments: The latest research on boron arsenide

Conformally-coated Nickel-Carbon Nitride on Structured Pyrolytic Carbon Electrodes for Enhanced Hydrogen Evolution

Authors: Nadira Meethale Palakkool, Mike P. C. Taverne, Owen G. Bell, Christopher P. Jones, Jonathan D. Mar, Duc Tam Ho, Vincent Barrioz, Yongtao Qu, Zhong Ren, Chung-Che Huang, Ying-Lung Daniel Ho

Abstract: This study presents a three-dimensional electrode for hydrogen evolution reaction (HER), tackling challenges in corrosion resistance, catalytic activity, and durability. The electrode features a rod-connected diamond structure made of pyrolytic carbon (PyC), with sequential Ni and CN conformal coatings, resulting in an increase of its electrochemical active surface area more than 80 times their ge… ▽ More This study presents a three-dimensional electrode for hydrogen evolution reaction (HER), tackling challenges in corrosion resistance, catalytic activity, and durability. The electrode features a rod-connected diamond structure made of pyrolytic carbon (PyC), with sequential Ni and CN conformal coatings, resulting in an increase of its electrochemical active surface area more than 80 times their geometric surface area, marking the first application of CN/Ni/RCD-PyC electrodes for HER. The CN layer enhances corrosion resistance under acidic and alkaline conditions, while synergizing with Ni boosts catalytic activity. We demonstrate that the CN/Ni/RCD-PyC electrode exhibited superior HER activity, achieving lower overpotentials of 0.6 V and 0.4 V for a current density of $\mathrm{10~mA\cdot cm^{-2}}$ in acidic and alkaline media, respectively. The electrode demonstrates excellent durability with performance over 2000 cycles of cyclic voltammetry at high scan rates with no significant decay. Therefore, this electrode offers a scalable, cost-effective solution for sustainable hydrogen production. △ Less

Submitted 19 June, 2025; v1 submitted 10 May, 2025; originally announced May 2025.

Comments: 38 pages (main: 24, Supplementary information: 14); 21 figures (main: 9, Supplementary information: 12); 3 tables (main: 0, Supplementary information: 3); Submitted to IOP Progress in Energy

Vortex-Free Intrinsic Orbital Angular Momentum

Authors: Wenxiang Yan, Zheng Yuan, Yuan Gao, Xian Long, Zhi-Cheng Ren, Xi-Lin Wang, Jianping Ding, Hui-Tian Wang

Abstract: Optical orbital angular momentum (OAM) has traditionally relied on vortex beams with helical phase fronts imparting quantized intrinsic OAM. Here, we introduce a fundamentally vortex_free framework where intrinsic OAM arises from the natural curvature of lights energy flow, specifically, the caustic geometry of self_accelerating beams whose curved trajectories act as orbital highways for photons.… ▽ More Optical orbital angular momentum (OAM) has traditionally relied on vortex beams with helical phase fronts imparting quantized intrinsic OAM. Here, we introduce a fundamentally vortex_free framework where intrinsic OAM arises from the natural curvature of lights energy flow, specifically, the caustic geometry of self_accelerating beams whose curved trajectories act as orbital highways for photons. This OAM generation mechanism is independent of phase vortices but mirrors celestial orbital motion. Through numerical simulations, experimental characterization, and optomechanical measurements using optical tweezers, we demonstrate intrinsic vortex_free OAM rooted solely in beam intensity architecture. Generalizing beyond geometric caustics to arbitrary optical fields, we demonstrate OAM via curved Poynting_vector energy streamlines, unifying conventional vortex and novel vortex_free OAM under a single quantitative framework. Streamline engineering enables customizable rotational dynamics, including hybrid orbital_cyclonic motions reminiscent of tropical storms, with promising applications in precision optomechanics, optofluidics, and optical analogues of fluid dynamics. This energy-flow perspective offers a versatile platform for designing and quantifying OAM across structured light. △ Less

Submitted 21 July, 2025; v1 submitted 27 March, 2025; originally announced March 2025.

The development of vibration modes propagation method to perform wave-optics simulation of beamline vibration

Authors: Han Xu, Xiao Li, Ming Li, Zhe Ren, Yi Zhang, Peng Liu, Yuhui Dong, Liang Zhou

Abstract: The evolution from 3rd to 4th generation synchrotron radiation (SR) sources provide promising potential improvements in X-ray techniques, particularly in spatial resolution for imaging, temporal resolution for dynamic studies, and beam size control for nanoprobes. Achieving these enhancements demands effective vibration suppression in beamline systems. This challenge drives the need for optical de… ▽ More The evolution from 3rd to 4th generation synchrotron radiation (SR) sources provide promising potential improvements in X-ray techniques, particularly in spatial resolution for imaging, temporal resolution for dynamic studies, and beam size control for nanoprobes. Achieving these enhancements demands effective vibration suppression in beamline systems. This challenge drives the need for optical designs that ensure efficient photon transport while maintaining vibration within acceptable thresholds. To address the advanced coherence requirements of fourth-generation SR sources, wave-optics simulations must be incorporated into optical design processes. We therefore propose a vibration mode propagation method using wave-optics techniques for beamline vibration simulation. Our approach achieves an almost 40-fold computational acceleration in actual beamline models compared to conventional methods, enabling direct analysis of propagating wavefront vibrations. This framework allows systematic evaluation of intensity distribution variations, coherence changes, and beam positioning errors caused by mechanical vibrations. △ Less

Submitted 18 March, 2025; originally announced March 2025.

OptMetaOpenFOAM: Large Language Model Driven Chain of Thought for Sensitivity Analysis and Parameter Optimization based on CFD

Authors: Yuxuan Chen, Long Zhang, Xu Zhu, Hua Zhou, Zhuyin Ren

Abstract: Merging natural language interfaces with computational fluid dynamics (CFD) workflows presents transformative opportunities for both industry and research. In this study, we introduce OptMetaOpenFOAM - a novel framework that bridges MetaOpenFOAM with external analysis and optimization tool libraries through a large language model (LLM)-driven chain-of-thought (COT) methodology. By automating compl… ▽ More Merging natural language interfaces with computational fluid dynamics (CFD) workflows presents transformative opportunities for both industry and research. In this study, we introduce OptMetaOpenFOAM - a novel framework that bridges MetaOpenFOAM with external analysis and optimization tool libraries through a large language model (LLM)-driven chain-of-thought (COT) methodology. By automating complex CFD tasks via natural language inputs, the framework empowers non-expert users to perform sensitivity analyses and parameter optimizations with markedly improved efficiency. The test dataset comprises 11 distinct CFD analysis or optimization tasks, including a baseline simulation task derived from an OpenFOAM tutorial covering fluid dynamics, combustion, and heat transfer. Results confirm that OptMetaOpenFOAM can accurately interpret user requirements expressed in natural language and effectively invoke external tool libraries alongside MetaOpenFOAM to complete the tasks. Furthermore, validation on a non-OpenFOAM tutorial case - namely, a hydrogen combustion chamber - demonstrates that a mere 200-character natural language input can trigger a sequence of simulation, postprocessing, analysis, and optimization tasks spanning over 2,000 lines of code. These findings underscore the transformative potential of LLM-driven COT methodologies in linking external tool for advanced analysis and optimization, positioning OptMetaOpenFOAM as an effective tool that streamlines CFD simulations and enhances their convenience and efficiency for both industrial and research applications. Code is available at https://github.com/Terry-cyx/MetaOpenFOAM. △ Less

Submitted 3 March, 2025; originally announced March 2025.

Comments: 26 pages,11 figures

Understanding observational characteristics of solar flare current sheets

Authors: Zining Ren, Yulei Wang, Xin Cheng, Mingde Ding

Abstract: The elongated bright structures above solar flare loops are suggested to be current sheets, where magnetic reconnection takes place. Observations have revealed various characteristics of the current sheet; however, their physical origin remains to be ascertained. In this study we aim to reveal the relations of observational characteristics of current sheets with the fundamental processes of magnet… ▽ More The elongated bright structures above solar flare loops are suggested to be current sheets, where magnetic reconnection takes place. Observations have revealed various characteristics of the current sheet; however, their physical origin remains to be ascertained. In this study we aim to reveal the relations of observational characteristics of current sheets with the fundamental processes of magnetic reconnection. Using high-resolution 3D magnetohydrodynamic simulations of turbulent magnetic reconnection within a solar flare current sheet, we synthesized the remote-sensing observations of the current sheet and determined their physical properties. Turbulent magnetic reconnection can significantly broaden the apparent width of the current sheet, which is much larger than the realistic physical width because of the superposition effect. The differential emission measures of the current sheet have two peaks; the high-temperature component is spatially related to confirmed small-scale reconnection sites, showing that the current sheet is directly heated by reconnection. Moreover, we demonstrate that strong turbulence can cause the nonthermal broadening of spectral lines at both the current sheet and flare loop-top regions. A strong correlation between them in time is also observed. Our 3D turbulent magnetic reconnection flare model can be used to interpret primary observational characteristics of the elongated bright current sheets of solar flares. △ Less

Submitted 20 February, 2025; originally announced February 2025.

Comments: 9 pages, 12 figures. Accepted for publication in Astronomy & Astrophysics

Frequency-comb-steered ultrawideband quasi-true-time-delay beamformer for integrated sensing and communication

Authors: Mian Wang, Wenxin Zhang, Zeyu Ren, Shangyuan Li, Xiaoping Zheng, Xiaoxiao Xue

Abstract: Phased array antennas (PAAs) possessing broadband beamforming capabilities are crucial for advanced radar and wireless communication systems. Nevertheless, traditional phase-shifter-based PAA beamformers frequently encounter the beam-squint issue, which substantially restricts their instantaneous bandwidth. Photonic true-time-delay (TTD) beamformers have the potential to overcome this challenge, o… ▽ More Phased array antennas (PAAs) possessing broadband beamforming capabilities are crucial for advanced radar and wireless communication systems. Nevertheless, traditional phase-shifter-based PAA beamformers frequently encounter the beam-squint issue, which substantially restricts their instantaneous bandwidth. Photonic true-time-delay (TTD) beamformers have the potential to overcome this challenge, offering ultrawide bandwidth and immunity to electromagnetic interference. However, their practical application is impeded by the high complexity, which typically involves a vast array of optical switches and delay lines. Here, we introduce a novel frequency-comb-steered photonic quasi-TTD beamformer that eliminates the need for delay lines by leveraging the concepts of frequency-diverse arrays and photonic microwave mixing arrays. This beamformer enables squint-free beamforming of ultrawideband linear frequency modulation waveforms, which is essential for high-resolution radar applications. It ensures seamless and continuous beam steering, effectively delivering infinite spatial resolution. We present a prototype with an 8-element PAA, demonstrating an instantaneous bandwidth of 6 GHz across the entire Ku-band. Additionally, we explore the system's capabilities in integrated inverse synthetic aperture radar imaging and high-speed communication, achieving a high imaging resolution of 2.6 cm * 3.0 cm and a transmission rate of 3 Gbps. Compared to conventional delay-line-based beamformers, our new concept markedly reduces hardware complexity and enhances scalability, positioning it as a potent enabler for future integrated sensing and communication applications. △ Less

Submitted 12 February, 2025; originally announced February 2025.

Comments: 17 pages, 4 figures

Postselection-Free Cavity-Enhanced Narrow-Band Orbital Angular Momentum Entangled Photon Source

Authors: Pei Wan, Wen-Zheng Zhu, Yan-Chao Lou, Zi-Mo Cheng, Zhi-Cheng Ren, Han Zhang, Xi-Lin Wang, Hui-Tian Wang

Abstract: Cavity-enhanced spontaneous parametric down-conversion (SPDC) provides a significant way to produce $\sim$10 MHz narrow-band photon pairs, which matches the bandwidth of photon for quantum memory. However, the output photon pairs from the cavity is not entangled and the postselection is required to create the entanglement outside the cavity, so the direct output of cavity-enhanced narrow-band enta… ▽ More Cavity-enhanced spontaneous parametric down-conversion (SPDC) provides a significant way to produce $\sim$10 MHz narrow-band photon pairs, which matches the bandwidth of photon for quantum memory. However, the output photon pairs from the cavity is not entangled and the postselection is required to create the entanglement outside the cavity, so the direct output of cavity-enhanced narrow-band entangled photon pairs is still an open challenge. Here we propose a solution that realizes the first postselection-free cavity-enhanced narrow-band entangled photon pairs. The entanglement is achieved in degree of freedom (DOF) of orbital angular momentum (OAM) by implementing an OAM-conservation SPDC process in an actively and precisely controlled cavity supporting degenerate high-order OAM modes. The measured linewidth for the two photons is 13.8 MHz and the measured fidelity is 0.969(3) for the directly generated OAM entangled two photons. We deterministically transfer the OAM entanglement to polarization one with almost no loss and obtain polarization entangled two photons with a fidelity of 0.948(2). Moreover, we produce narrow-band OAM-polarization hyperentangled photon pairs with a fidelity of 0.850(2) by establishing polarization entanglement with preservation of OAM entanglement, which is realized by interfering the two photons on a polarizing beam splitter (PBS) and post-selecting the events of one and only one photon in on each of the PBS port. Novel cavity may find applications in cavity-based light-matter interaction. Our results provide an efficient and promising approach to create narrow-band entangled photon sources for memory-based long-distance quantum communication and network. △ Less

Submitted 8 February, 2025; originally announced February 2025.

Comments: 7 pages, 5 figures,

Journal ref: Phys. Rev. Lett. 134, 053801 (2025)

A Mechanistic Study on Environment Gases in Metal Additive Manufacturing

Authors: Zhongshu Ren, Samuel J. Clark, Lin Gao, Kamel Fezzaa, Tao Sun

Abstract: A variety of protective or reactive environmental gases have recently gained growing attention in laser-based metal additive manufacturing (AM) technologies due to their unique thermophysical properties and the potential improvements they can bring to the build processes. However, much remains unclear regarding the effects of different gas environments on critical phenomena in laser AM, such as ra… ▽ More A variety of protective or reactive environmental gases have recently gained growing attention in laser-based metal additive manufacturing (AM) technologies due to their unique thermophysical properties and the potential improvements they can bring to the build processes. However, much remains unclear regarding the effects of different gas environments on critical phenomena in laser AM, such as rapid cooling, energy coupling, and defect generation. Through simultaneous high-speed synchrotron x-ray imaging and thermal imaging, we identify distinct effects of various environmental gases in laser AM and gained a deeper understanding of the underlying mechanisms. Compared to the commonly used protective gas, argon, it is found that helium has a negligible effect on cooling the part. However, helium can suppress unstable keyholes by decreasing effective energy absorption, thus mitigating keyhole porosity generation and reducing pore size under certain processing conditions. These observations provide guidelines for the strategic use of environmental gases in laser AM to produce parts with improved quality. △ Less

Submitted 4 February, 2025; originally announced February 2025.

MetaOpenFOAM 2.0: Large Language Model Driven Chain of Thought for Automating CFD Simulation and Post-Processing

Authors: Yuxuan Chen, Xu Zhu, Hua Zhou, Zhuyin Ren

Abstract: Computational Fluid Dynamics (CFD) is widely used in aerospace, energy, and biology to model fluid flow, heat transfer, and chemical reactions. While Large Language Models (LLMs) have transformed various domains, their application in CFD remains limited, particularly for complex tasks like post-processing. To bridge this gap, we introduce MetaOpenFOAM 2.0, which leverages Chain of Thought (COT) de… ▽ More Computational Fluid Dynamics (CFD) is widely used in aerospace, energy, and biology to model fluid flow, heat transfer, and chemical reactions. While Large Language Models (LLMs) have transformed various domains, their application in CFD remains limited, particularly for complex tasks like post-processing. To bridge this gap, we introduce MetaOpenFOAM 2.0, which leverages Chain of Thought (COT) decomposition and iterative verification to enhance accessibility for non-expert users through natural language inputs. Tested on a new benchmark covering simulation (fluid flow, heat transfer, combustion) and post-processing (extraction, visualization), MetaOpenFOAM 2.0 achieved an Executability score of 6.3/7 and a pass rate of 86.9%, significantly outperforming MetaOpenFOAM 1.0 (2.1/7, 0%). Additionally, it proved cost-efficient, averaging $0.15 per case. An ablation study confirmed that COT-driven decomposition and iterative refinement substantially improved task performance. Furthermore, scaling laws showed that increasing COT steps enhanced accuracy while raising token usage, aligning with LLM post-training scaling trends. These results highlight the transformative potential of LLMs in automating CFD workflows for industrial and research applications. Code is available at https://github.com/Terry-cyx/MetaOpenFOAM △ Less

Submitted 1 February, 2025; originally announced February 2025.

Comments: 16 pages,11 figures

Improving Tropical Cyclone Forecasting With Video Diffusion Models

Authors: Zhibo Ren, Pritthijit Nath, Pancham Shukla

Abstract: Tropical cyclone (TC) forecasting is crucial for disaster preparedness and mitigation. While recent deep learning approaches have shown promise, existing methods often treat TC evolution as a series of independent frame-to-frame predictions, limiting their ability to capture long-term dynamics. We present a novel application of video diffusion models for TC forecasting that explicitly models tempo… ▽ More Tropical cyclone (TC) forecasting is crucial for disaster preparedness and mitigation. While recent deep learning approaches have shown promise, existing methods often treat TC evolution as a series of independent frame-to-frame predictions, limiting their ability to capture long-term dynamics. We present a novel application of video diffusion models for TC forecasting that explicitly models temporal dependencies through additional temporal layers. Our approach enables the model to generate multiple frames simultaneously, better capturing cyclone evolution patterns. We introduce a two-stage training strategy that significantly improves individual-frame quality and performance in low-data regimes. Experimental results show our method outperforms the previous approach of Nath et al. by 19.3% in MAE, 16.2% in PSNR, and 36.1% in SSIM. Most notably, we extend the reliable forecasting horizon from 36 to 50 hours. Through comprehensive evaluation using both traditional metrics and Fréchet Video Distance (FVD), we demonstrate that our approach produces more temporally coherent forecasts while maintaining competitive single-frame quality. Code accessible at https://github.com/Ren-creater/forecast-video-diffmodels. △ Less

Submitted 12 May, 2025; v1 submitted 27 January, 2025; originally announced January 2025.

Comments: Recommended for spotlight presentation at the ICLR 2025 workshop on Tackling Climate Change with Machine Learning. 7 pages, 7 figures

Healing of the edge magnetic island in the island divertor configuration on J-TEXT

Authors: Zhangrong Hou, Song Zhou, Nengchao Wang, Yonghua Ding, Zhonghe Jiang, Yunfeng Liang, Zhengkang Ren, Feiyue Mao, Qinghu Yang, Jiaming Wang, Xin Xu, Yutong Yang, Jiankun Hua, Zijian Xuan, Chuanxu Zhao, Yangbo Li, Lei Yu, Donghui Xia, Zhipeng Chen, Zhoujun Yang, the J-TEXT team

Abstract: The phenomena of island healing and configuration transition induced by high-power electron cyclotron resonance heating (ECRH) have been investigated in the island divertor configuration on the J-TEXT tokamak. Experimental results reveal that the size of the edge open magnetic island with mode number m/n = 3/1 decreases substantially under specific ECRH conditions. This process, referred to as isl… ▽ More The phenomena of island healing and configuration transition induced by high-power electron cyclotron resonance heating (ECRH) have been investigated in the island divertor configuration on the J-TEXT tokamak. Experimental results reveal that the size of the edge open magnetic island with mode number m/n = 3/1 decreases substantially under specific ECRH conditions. This process, referred to as island healing, occurs when ECRH with a power of 500~600 kW is deposited in the plasma core or when 250 kW of ECRH is deposited at r = 0.5 a, where a is the minor radius. The reduction of the island width makes the island divertor ineffective and transition into the limiter configuration. A model incorporating the influence of ECRH on the scrape-off layer (SOL) thermoelectric current is proposed to explain the observed changes in the edge magnetic topology of the island divertor configuration. These findings suggest that ECRH should be deposited at the plasma core with carefully controlled power to ensure the stable and compatible operation of ECRH and the island divertor configuration in tokamaks. The results can provide insights into achieving robust operation of an island divertor in tokamaks. △ Less

Submitted 14 January, 2025; originally announced January 2025.

Successive optimization of optics and post-processing with differentiable coherent PSF operator and field information

Authors: Zheng Ren, Jingwen Zhou, Wenguan Zhang, Jiapu Yan, Bingkun Chen, Huajun Feng, Shiqi Chen

Abstract: Recently, the joint design of optical systems and downstream algorithms is showing significant potential. However, existing rays-described methods are limited to optimizing geometric degradation, making it difficult to fully represent the optical characteristics of complex, miniaturized lenses constrained by wavefront aberration or diffraction effects. In this work, we introduce a precise optical… ▽ More Recently, the joint design of optical systems and downstream algorithms is showing significant potential. However, existing rays-described methods are limited to optimizing geometric degradation, making it difficult to fully represent the optical characteristics of complex, miniaturized lenses constrained by wavefront aberration or diffraction effects. In this work, we introduce a precise optical simulation model, and every operation in pipeline is differentiable. This model employs a novel initial value strategy to enhance the reliability of intersection calculation on high aspherics. Moreover, it utilizes a differential operator to reduce memory consumption during coherent point spread function calculations. To efficiently address various degradation, we design a joint optimization procedure that leverages field information. Guided by a general restoration network, the proposed method not only enhances the image quality, but also successively improves the optical performance across multiple lenses that are already in professional level. This joint optimization pipeline offers innovative insights into the practical design of sophisticated optical systems and post-processing algorithms. The source code will be made publicly available at https://github.com/Zrr-ZJU/Successive-optimization △ Less

Submitted 23 December, 2024; v1 submitted 19 December, 2024; originally announced December 2024.

Constrained Transformer-Based Porous Media Generation to Spatial Distribution of Rock Properties

Authors: Zihan Ren, Sanjay Srinivasan, Dustin Crandall

Abstract: Pore-scale modeling of rock images based on information in 3D micro-computed tomography data is crucial for studying complex subsurface processes such as CO2 and brine multiphase flow during Geologic Carbon Storage (GCS). While deep learning models can generate 3D rock microstructures that match static rock properties, they have two key limitations: they don't account for the spatial distribution… ▽ More Pore-scale modeling of rock images based on information in 3D micro-computed tomography data is crucial for studying complex subsurface processes such as CO2 and brine multiphase flow during Geologic Carbon Storage (GCS). While deep learning models can generate 3D rock microstructures that match static rock properties, they have two key limitations: they don't account for the spatial distribution of rock properties that can have an important influence on the flow and transport characteristics (such as permeability and relative permeability) of the rock and they generate structures below the representative elementary volume (REV) scale for those transport properties. Addressing these issues is crucial for building a consistent workflow between pore-scale analysis and field-scale modeling. To address these challenges, we propose a two-stage modeling framework that combines a Vector Quantized Variational Autoencoder (VQVAE) and a transformer model for spatial upscaling and arbitrary-size 3D porous media reconstruction in an autoregressive manner. The VQVAE first compresses and quantizes sub-volume training images into low-dimensional tokens, while we train a transformer to spatially assemble these tokens into larger images following specific spatial order. By employing a multi-token generation strategy, our approach preserves both sub-volume integrity and spatial relationships among these sub-image patches. We demonstrate the effectiveness of our multi-token transformer generation approach and validate it using real data from a test well, showcasing its potential to generate models for the porous media at the well scale using only a spatial porosity model. The interpolated representative porous media that reflect field-scale geological properties accurately model transport properties, including permeability and multiphase flow relative permeability of CO2 and brine. △ Less

Submitted 28 October, 2024; originally announced October 2024.

Comments: 24 pages

Ultrafast control of braiding topology in non-Hermitian metasurfaces

Authors: Yuze Hu, Mingyu Tong, Ziheng Ren, Fujia Chen, Qiaolu Chen, Hongsheng Chen, Tian Jiang, Yihao Yang

Abstract: The mathematical theory of braids, influential across scientific disciplines, has emerged as a compelling strategy for light manipulation. Existing approaches to creating braids in photonics, whether in momentum-space bandstructures or real-space fields, often face limitations associated with static nature of devices and lack of tunability. Here, we experimentally demonstrate ultrafast control of… ▽ More The mathematical theory of braids, influential across scientific disciplines, has emerged as a compelling strategy for light manipulation. Existing approaches to creating braids in photonics, whether in momentum-space bandstructures or real-space fields, often face limitations associated with static nature of devices and lack of tunability. Here, we experimentally demonstrate ultrafast control of eigen-spectrum braids of Jones matrices within mere picoseconds, in reconfigurable non-Hermitian metasurfaces. The Jones matrices of the metasurface exhibit a complex eigen-spectrum that braids in the three-dimensional eigenvalue-frequency space, thereby creating arbitrary elements within the two-string braid group, B2. By exciting the photoconductive semiconductor terahertz metasurface with a femtosecond infrared pulse, we achieve ultrafast switching of the braids, transitioning from the Solomon link to either the Trefoil knot or Hopf link. Our approach serves as a pivotal tool for elucidating non-trivial topology of braids and studying ultrafast topological optoelectronics. △ Less

Submitted 22 October, 2024; originally announced October 2024.

Increased resistance to photooxidation in Dion-Jacobson lead halide perovskites -- implication for perovskite device stability

Authors: Zhilin Ren, Juraj Ovčar, Tik Lun Leung, Yanling He, Yin Li, Dongyang Li, Xinshun Qin, Hongbo Mo, Zhengtian Yuan, Jueming Bing, Martin P. Bucknall, Luca Grisanti, Muhammad Umair Ali, Peng Bai, Tao Zhu, Ali Ashger Syed, Jingyang Lin, Jingbo Wang, Abdul-Khaleed, Wenting Sun, Gangyue Li, Gang Li, Alan Man Ching Ng, Anita W. Y. Ho-Baillie, Ivor Lončarić , et al. (2 additional authors not shown)

Abstract: 2D metal halide perovskites have enabled significant stability improvements in perovskite devices, particularly in resistance to moisture. However, some 2D perovskites are even more susceptible to photooxidation compared to 3D perovskites. This is particularly true for more commonly investigated Ruddlesden-Popper (RP) perovskites that exhibit increased susceptibility to photoinduced degradation co… ▽ More 2D metal halide perovskites have enabled significant stability improvements in perovskite devices, particularly in resistance to moisture. However, some 2D perovskites are even more susceptible to photooxidation compared to 3D perovskites. This is particularly true for more commonly investigated Ruddlesden-Popper (RP) perovskites that exhibit increased susceptibility to photoinduced degradation compared to Dion-Jacobson (DJ) perovskites. Comparisons between different RP and DJ perovskites reveal that this phenomenon cannot be explained by commonly proposed differences in superoxide ion generation, interlayer distance and lattice structural rigidity differences. Instead, the resistance to photooxidation of DJ perovskites can be attributed to decreased likelihood of double deprotonation events (compared to single deprotonation events in RP perovskites) required for the loss of organic cations and the perovskite decomposition. Consequently, DJ perovskites are less susceptible to oxidative degradation (both photo- and electrochemically induced), which leads to improved operational stability of solar cells based on these materials. △ Less

Submitted 19 September, 2024; originally announced September 2024.

Comments: Main text: 19 pages, 6 figures, supplementary information: 62 pages, 47 figures

Apparatus for producing single strontium atoms in an optical tweezer array

Authors: Kai Wen, Huijin Chen, Xu Yan, Zejian Ren, Chengdong He, Elnur Hajiyev, Preston Tsz Fung Wong, Gyu-Boong Jo

Abstract: We outline an experimental setup for efficiently preparing a tweezer array of $^{88}$Sr atoms. Our setup uses permanent magnets to maintain a steady-state two-dimensional magneto-optical trap (MOT) which results in a loading rate of up to $10^{8}$ s$^{-1}$ at 5 mK for the three-dimensional blue MOT. This enables us to trap $2\times10^{6}$ $^{88}$Sr atoms at 2 $μ$K in a narrow-line red MOT with the… ▽ More We outline an experimental setup for efficiently preparing a tweezer array of $^{88}$Sr atoms. Our setup uses permanent magnets to maintain a steady-state two-dimensional magneto-optical trap (MOT) which results in a loading rate of up to $10^{8}$ s$^{-1}$ at 5 mK for the three-dimensional blue MOT. This enables us to trap $2\times10^{6}$ $^{88}$Sr atoms at 2 $μ$K in a narrow-line red MOT with the $^{1}$S$_{0}$ $\rightarrow$ $^{3}$P$_{1}$ intercombination transition at 689 nm. With the Sisyphus cooling and pairwise loss processes, single atoms are trapped and imaged in 813 nm optical tweezers, exhibiting a lifetime of 2.5 minutes. We further investigate the survival fraction of a single atom in the tweezers and characterize the optical tweezer array using a release and recapture technique. Our platform paves the way for potential applications in atomic clocks, precision measurements, and quantum simulations. △ Less

Submitted 9 September, 2024; originally announced September 2024.

Comments: 7 pages, 5 figures

One-dimensional Photonic Crystal Structure Enhanced External-Magnetic-Field-Free Spintronic Terahertz High-Field Emitter

Authors: Zehao Yang, Jiahui Li, Shaojie Liu, Zejun Ren, Mingxuan Zhang, Chunyan Geng, Xiufeng Han, Caihua Wan, Xiaojun Wu

Abstract: Intense terahertz (THz) radiation in free space offers multifaceted capabilities for accelerating electron, understanding the mesoscale architecture in (bio)materials, elementary excitation and so on. Recently popularized spintronic THz emitters (STEs) with their versatility such as ultra-broadband, cost-effectiveness, large-size and ease for-integration have become one of the most promising alter… ▽ More Intense terahertz (THz) radiation in free space offers multifaceted capabilities for accelerating electron, understanding the mesoscale architecture in (bio)materials, elementary excitation and so on. Recently popularized spintronic THz emitters (STEs) with their versatility such as ultra-broadband, cost-effectiveness, large-size and ease for-integration have become one of the most promising alternative for the next generation of intense THz sources. Nevertheless, the typical W| Co20Fe60B20 | Pt necessitates an external-magnetic-field to saturate magnetization for stable operation, limiting its scalability for achieving higher THz field with uniform distribution over larger sample areas. Here we demonstrate the methodologies of enhancing the high-field THz radiation of external-magnetic-field-free IrMn3 | Co20Fe60B20 |W heterostructure via optimizing the substrate with superior thermal conductivity and integrating a one-dimensional photonic crystal (PC) structure to maximize the radiation efficiency. Under the excitation of a Ti: sapphire femtosecond laser amplifier with central wavelength of 800 nm, pulse duration of 35 fs, and repetition rate of 1 kHz and maximum single pulse energy of 5.5 mJ, we successfully generate intense THz radiation with focal peak electric field up to 1.1 MV/cm with frequency range covering 0.1-10 THz without external-magnetic-fields. These high-field STEs will also enable other applications such as ultra-broadband high-field THz spectroscopy and polarization-based large-size strong-field THz imaging. △ Less

Submitted 26 August, 2024; originally announced August 2024.

MetaOpenFOAM: an LLM-based multi-agent framework for CFD

Authors: Yuxuan Chen, Xu Zhu, Hua Zhou, Zhuyin Ren

Abstract: Remarkable progress has been made in automated problem solving through societies of agents based on large language models (LLMs). Computational fluid dynamics (CFD), as a complex problem, presents unique challenges in automated simulations that require sophisticated solutions. MetaOpenFOAM, as a novel multi-agent collaborations framework, aims to complete CFD simulation tasks with only natural lan… ▽ More Remarkable progress has been made in automated problem solving through societies of agents based on large language models (LLMs). Computational fluid dynamics (CFD), as a complex problem, presents unique challenges in automated simulations that require sophisticated solutions. MetaOpenFOAM, as a novel multi-agent collaborations framework, aims to complete CFD simulation tasks with only natural language as input. These simulation tasks include mesh pre-processing, simulation and so on. MetaOpenFOAM harnesses the power of MetaGPT's assembly line paradigm, which assigns diverse roles to various agents, efficiently breaking down complex CFD tasks into manageable subtasks. Langchain further complements MetaOpenFOAM by integrating Retrieval-Augmented Generation (RAG) technology, which enhances the framework's ability by integrating a searchable database of OpenFOAM tutorials for LLMs. Tests on a benchmark for natural language-based CFD solver, consisting of eight CFD simulation tasks, have shown that MetaOpenFOAM achieved a high pass rate per test (85%), with each test case costing only $0.22 on average. The eight CFD simulation tasks encompass a range of multidimensional flow problems, covering compressible and incompressible flows with different physical processes. This demonstrates the capability to automate CFD simulations using only natural language input, iteratively correcting errors to achieve the desired simulations. An ablation study was conducted to verify the necessity of each component in the multi-agent system and the RAG technology. A sensitivity study on the randomness of LLM showed that LLM with low randomness can obtain more stable and accurate results. Additionally, MetaOpenFOAM owns the ability to identify and modify key parameters in user requirements, and excels in correcting bugs when failure match occur,which demonstrates the generalization of MetaOpenFOAM. △ Less

Submitted 7 August, 2024; v1 submitted 31 July, 2024; originally announced July 2024.

Comments: 31 pages,11 figures, 11 tables

COLOSS: Complex-scaled Optical and couLOmb Scattering Solver

Authors: Junzhe Liu, Jin Lei, Zhongzhou Ren

Abstract: We introduce COLOSS, a program designed to address the scattering problem using a bound-state technique known as complex scaling. In this method, the oscillatory boundary conditions of the wave function are transformed into exponentially decaying ones, accommodating the long-range Coulomb interaction. The program implements the Woods-Saxon form of a realistic optical potential, with all potential… ▽ More We introduce COLOSS, a program designed to address the scattering problem using a bound-state technique known as complex scaling. In this method, the oscillatory boundary conditions of the wave function are transformed into exponentially decaying ones, accommodating the long-range Coulomb interaction. The program implements the Woods-Saxon form of a realistic optical potential, with all potential parameters included in a well-designed input format for ease of use. This design offers users straightforward access to compute \(S\)-matrices and cross-sections of the scattering process. We provide thorough discussions on the precision of Lagrange functions and their benefits in evaluating matrix elements. Additionally, COLOSS incorporates two distinct rotation methods, making it adaptable to potentials without analytical expressions. Comparative results demonstrate that COLOSS achieves high accuracy when compared with the direct integration method, Numerov, underscoring its utility and effectiveness in scattering calculations. △ Less

Submitted 23 July, 2024; originally announced July 2024.

Multi-reservoir enhanced loading of tweezer atom arrays

Authors: Xu Yan, Chengdong He, Kai Wen, Zejian Ren, Preston Tsz Fung Wong, Elnur Hajiyev, Gyu-Boong Jo

Abstract: We introduce a species-independent method for improved loading into a single-atom optical tweezer array, utilizing iterative loading with multiple reservoir tweezers. Demonstrated with dual wavelength tweezer arrays of $^{88}$Sr atoms, our approach achieves a 96$\%$ loading rate after four reload cycles. This method can significantly enhance existing tweezer rearrangement protocols, potentially re… ▽ More We introduce a species-independent method for improved loading into a single-atom optical tweezer array, utilizing iterative loading with multiple reservoir tweezers. Demonstrated with dual wavelength tweezer arrays of $^{88}$Sr atoms, our approach achieves a 96$\%$ loading rate after four reload cycles. This method can significantly enhance existing tweezer rearrangement protocols, potentially reducing iteration time and optical power consumption, thereby enabling a larger number of atoms in a quantum logic device. △ Less

Submitted 16 July, 2024; originally announced July 2024.

Comments: 6 pages, 4 figures ; supplementary materials

Wideband Coherent Microwave Conversion via Magnon Nonlinearity in Hybrid Quantum System

Authors: Jiahao Wu, Jiacheng Liu, Zheyu Ren, Man Yin Leung, Wai Kuen Leung, Kin On Ho, Xiangrong Wang, Qiming Shao, Sen Yang

Abstract: Frequency conversion is a widely realized physical process in nonlinear systems of optics and electronics. As an emerging nonlinear platform, spintronic devices have the potential to achieve stronger frequency conversion. Here, we demonstrated a microwave frequency conversion method in a hybrid quantum system, integrating nitrogen-vacancy centers in diamond with magnetic thin film CoFeB. We achiev… ▽ More Frequency conversion is a widely realized physical process in nonlinear systems of optics and electronics. As an emerging nonlinear platform, spintronic devices have the potential to achieve stronger frequency conversion. Here, we demonstrated a microwave frequency conversion method in a hybrid quantum system, integrating nitrogen-vacancy centers in diamond with magnetic thin film CoFeB. We achieve a conversion bandwidth ranging from 0.1 to 12GHz, presenting an up to $\mathrm{25^{th}}$ order frequency conversion and further display the application of this method for frequency detection and qubits coherent control. Distinct from traditional frequency conversion techniques based on nonlinear electric response, our approach employs nonlinear magnetic response in spintronic devices. The nonlinearity, originating from the symmetry breaking such as domain walls in magnetic films, presents that our method can be adapted to hybrid systems of other spintronic devices and spin qubits, expanding the application scope of spintronic devices and providing a promising on-chip platform for coupling quantum systems. △ Less

Submitted 3 July, 2024; originally announced July 2024.

Comments: 11 pages, 5 figures

Journal ref: npj Spintronics volume 2, Article number: 30 (2024)

Towards Hypernuclei from Nuclear Lattice Effective Field Theory

Authors: Fabian Hildenbrand, Serdar Elhatisari, Zhengxue Ren, Ulf-G. Meißner

Abstract: Understanding the strong interactions within baryonic systems beyond the up and down quark sector is pivotal for a comprehensive description of nuclear forces. This study explores the interactions involving hyperons, particularly the $Λ$ particle, within the framework of nuclear lattice effective field theory (NLEFT). By incorporating $Λ$ hyperons into the NLEFT framework, we extend our investigat… ▽ More Understanding the strong interactions within baryonic systems beyond the up and down quark sector is pivotal for a comprehensive description of nuclear forces. This study explores the interactions involving hyperons, particularly the $Λ$ particle, within the framework of nuclear lattice effective field theory (NLEFT). By incorporating $Λ$ hyperons into the NLEFT framework, we extend our investigation into the $S = -1$ sector, allowing us to probe the third dimension of the nuclear chart. We calculate the $Λ$ separation energies ($B_Λ$) of hypernuclei up to the medium-mass region, providing valuable insights into hyperon-nucleon ($YN$) and hyperon-nucleon-nucleon ($YNN$) interactions. Our calculations employ high-fidelity chiral interactions at N${}^3$LO for nucleons and extend it to $Λ$ hyperons with leading-order S-wave $YN$ interactions as well as $YNN$ forces constrained only by the $A=4,5$ systems. Our results contribute to a deeper understanding of the SU(3) symmetry breaking and establish a foundation for future improvements in hypernuclear calculations. △ Less

Submitted 7 October, 2024; v1 submitted 25 June, 2024; originally announced June 2024.

Comments: 15 pages, 6 figures, 9 tables, typos corrected, extended discussion, final version accepted for publication

Complete Interband Transitions for Non-Hermitian Spin-Orbit-Coupled Cold-Atom Systems

Authors: Dong Liu, Zejian Ren, Wai Chun Wong, Entong Zhao, Chengdong He, Ka Kwan Pak, Gyu-Boong Jo, Jensen Li

Abstract: Recently, synthetic spin-orbit coupling has been introduced into cold-atom systems for more flexible control of the Hamiltonian, which was further made time-varying through two-photon detuning to achieve dynamic control of the cold-atom state. While an intraband transition can be adiabatically obtained, a complete interband transition, rather than a superposition of different bands, obtained throu… ▽ More Recently, synthetic spin-orbit coupling has been introduced into cold-atom systems for more flexible control of the Hamiltonian, which was further made time-varying through two-photon detuning to achieve dynamic control of the cold-atom state. While an intraband transition can be adiabatically obtained, a complete interband transition, rather than a superposition of different bands, obtained through fast sweeping is usually guaranteed by having the positions of the initial and final states be far away from any band gap in the quasimomentum space. Here, by introducing an additional non-Hermitian parameter through an atom-loss contrast together with two-photon detuning as two controllable external parameters, both intraband and complete interband transitions can be achieved independent of the positions of the initial and final states. In addition, a point-source diagram approach in the 2D external parameter space is developed to visualize and predict the locations of any nonadiabatic transitions. This control protocol can have potential applications in quantum state control and quantum simulations using cold-atom systems. △ Less

Submitted 4 March, 2024; originally announced March 2024.

Comments: 21 pages, 4 figures

Creation of a tweezer array for cold atoms utilizing a generative neural network

Authors: Zejian Ren, Xu Yan, Kai Wen, Huijin Chen, Elnur Hajiyev, Chengdong He, Gyu-Boong Jo

Abstract: Optical tweezers have become essential tools for dynamically manipulating objects, ranging from microspheres or biological molecules to neutral atoms. In this study, we demonstrate the creation of tweezer arrays using a generative neural network, which allows for the trapping of neutral atoms with tunable atom arrays. We have successfully loaded cold strontium atoms into various optical tweezer pa… ▽ More Optical tweezers have become essential tools for dynamically manipulating objects, ranging from microspheres or biological molecules to neutral atoms. In this study, we demonstrate the creation of tweezer arrays using a generative neural network, which allows for the trapping of neutral atoms with tunable atom arrays. We have successfully loaded cold strontium atoms into various optical tweezer patterns generated by a spatial light modulator (SLM) integrated with generative models. Our approach shortens the process time to control the SLM wtih minimal time delay, eliminating the need for repeated re-optimization of the hologram for the SLM. △ Less

Submitted 18 July, 2024; v1 submitted 11 January, 2024; originally announced January 2024.

Comments: 5 pages, 4 figures

Versatile manipulation of light- and dark- seeking particles on demand

Authors: Zheng Yuan, Chenchen Zhang, Yuan Gao, Wenxiang Yan, Zhi-Cheng Ren, Xi-Lin Wang, Jianping Ding, Hui-Tian Wang

Abstract: We propose a novel approach to enable the agile manipulation of light- and dark-seeking particles. Our approach involves introducing a two-curvilinear perfect optical vortex beam (TC-POVB) generated by superimposing a pair of curved beams. The TC-POVB exhibits the property of a perfect optical vortex, which means that its size remains constant regardless of its topological charge. Additionally, ea… ▽ More We propose a novel approach to enable the agile manipulation of light- and dark-seeking particles. Our approach involves introducing a two-curvilinear perfect optical vortex beam (TC-POVB) generated by superimposing a pair of curved beams. The TC-POVB exhibits the property of a perfect optical vortex, which means that its size remains constant regardless of its topological charge. Additionally, each curve of the TC-POVB can support a distinct orbital flow density (OFD). This enables the application of torques to produce a dark channel that satisfies the requirements for particle size and drives the revolution or rotation motion of the confined dark-seeking particles. To demonstrate the effectiveness of our approach, we manipulate light- and dark-seeking particles experimentally, making them perform various curvilinear trajectories simultaneously, including moving, revolving, and rotating. △ Less

Submitted 4 December, 2023; originally announced December 2023.

Revealing the preference for correcting separated aberrations in joint optic-image design

Authors: Jingwen Zhou, Shiqi Chen, Zheng Ren, Wenguan Zhang, Jiapu Yan, Huajun Feng, Qi Li, Yueting Chen

Abstract: The joint design of the optical system and the downstream algorithm is a challenging and promising task. Due to the demand for balancing the global optimal of imaging systems and the computational cost of physical simulation, existing methods cannot achieve efficient joint design of complex systems such as smartphones and drones. In this work, starting from the perspective of the optical design, w… ▽ More The joint design of the optical system and the downstream algorithm is a challenging and promising task. Due to the demand for balancing the global optimal of imaging systems and the computational cost of physical simulation, existing methods cannot achieve efficient joint design of complex systems such as smartphones and drones. In this work, starting from the perspective of the optical design, we characterize the optics with separated aberrations. Additionally, to bridge the hardware and software without gradients, an image simulation system is presented to reproduce the genuine imaging procedure of lenses with large field-of-views. As for aberration correction, we propose a network to perceive and correct the spatially varying aberrations and validate its superiority over state-of-the-art methods. Comprehensive experiments reveal that the preference for correcting separated aberrations in joint design is as follows: longitudinal chromatic aberration, lateral chromatic aberration, spherical aberration, field curvature, and coma, with astigmatism coming last. Drawing from the preference, a 10% reduction in the total track length of the consumer-level mobile phone lens module is accomplished. Moreover, this procedure spares more space for manufacturing deviations, realizing extreme-quality enhancement of computational photography. The optimization paradigm provides innovative insight into the practical joint design of sophisticated optical systems and post-processing algorithms. △ Less

Submitted 20 November, 2023; v1 submitted 8 September, 2023; originally announced September 2023.

Comments: 19 pages

Strong magnon-magnon coupling in an ultralow damping all-magnetic-insulator heterostructure

Authors: Jiacheng Liu, Yuzan Xiong, Jingming Liang, Xuezhao Wu, Chen Liu, Shun Kong Cheung, Zheyu Ren, Ruizi Liu, Andrew Christy, Zehan Chen, Ferris Prima Nugraha, Xi-Xiang Zhang, Chi Wah Leung, Wei Zhang, Qiming Shao

Abstract: Magnetic insulators such as yttrium iron garnets (YIGs) are of paramount importance for spin-wave or magnonic devices as their ultralow damping enables ultralow power dissipation that is free of Joule heating, exotic magnon quantum state, and coherent coupling to other wave excitations. Magnetic insulator heterostructures bestow superior structural and magnetic properties and house immense design… ▽ More Magnetic insulators such as yttrium iron garnets (YIGs) are of paramount importance for spin-wave or magnonic devices as their ultralow damping enables ultralow power dissipation that is free of Joule heating, exotic magnon quantum state, and coherent coupling to other wave excitations. Magnetic insulator heterostructures bestow superior structural and magnetic properties and house immense design space thanks to the strong and engineerable exchange interaction between individual layers. To fully unleash their potential, realizing low damping and strong exchange coupling simultaneously is critical, which often requires high quality interface. Here, we show that such a demand is realized in an all-insulator thulium iron garnet (TmIG)/YIG bilayer system. The ultralow dissipation rates in both YIG and TmIG, along with their significant spin-spin interaction at the interface, enable strong and coherent magnon-magnon coupling with a benchmarking cooperativity value larger than the conventional ferromagnetic metal-based heterostructures. The coupling strength can be tuned by varying the magnetic insulator layer thickness and magnon modes, which is consistent with analytical calculations and micromagnetic simulations. Our results demonstrate TmIG/YIG as a novel platform for investigating hybrid magnonic phenomena and open opportunities in magnon devices comprising all-insulator heterostructures. △ Less

Submitted 6 September, 2023; originally announced September 2023.

Comments: 45 pages, 18 figures, and 2 tables

Self-biased magnetoelectric Ni/LiNbO3/Ni for body embedded electronic energy harvesters

Authors: Tianwen Huang, Loïc Becerra, Aurélie Gensbittel, Yunlin Zheng, Hakeim Talleb, Ulises Acevedo Salas, Zhuoxiang Ren, Massimiliano Marangolo

Abstract: In this study, we present the fabrication and characterization of Ni/LiNbO3/Ni trilayers using RF sputtering. These trilayers exhibit thick Ni layers (10 microns) and excellent adherence to the substrate, enabling high magnetoelectric coefficients. By engineering the magnetic anisotropy of Nickel through anisotropic thermal residual stress induced during fabrication, and by selecting a carefully c… ▽ More In this study, we present the fabrication and characterization of Ni/LiNbO3/Ni trilayers using RF sputtering. These trilayers exhibit thick Ni layers (10 microns) and excellent adherence to the substrate, enabling high magnetoelectric coefficients. By engineering the magnetic anisotropy of Nickel through anisotropic thermal residual stress induced during fabrication, and by selecting a carefully chosen cut angle for the LiNbO3 substrate, we achieved a self-biased behavior. We demonstrate that these trilayers can power medical implant devices remotely using a small AC magnetic field excitation, thereby eliminating the need for a DC magnetic field and bulky magnetic field sources. The results highlight the potential of these trilayers for the wireless and non-invasive powering of medical implants. This work contributes to the advancement of magnetoelectric materials and their applications in healthcare technology. △ Less

Submitted 29 August, 2023; originally announced August 2023.

Comments: 20 pages, 9 figures,

Complex unit lattice cell for low-emittance storage ring light source

Authors: Zhiliang Ren, Zhenghe Bai, Penghui Yang, Lin Wang, Hongliang Xu

Abstract: To achieve the true diffraction-limited emittance of a storage ring light source, such as ~10 pm.rad for medium-energy electron beams, within a limited circumference, it is generally necessary to increase the number of bending magnets in a multi-bend achromat (MBA) lattice, as in the future upgrade plan of MAX IV with a 19BA replacing the current 7BA. However, this comes with extremely strong quad… ▽ More To achieve the true diffraction-limited emittance of a storage ring light source, such as ~10 pm.rad for medium-energy electron beams, within a limited circumference, it is generally necessary to increase the number of bending magnets in a multi-bend achromat (MBA) lattice, as in the future upgrade plan of MAX IV with a 19BA replacing the current 7BA. However, this comes with extremely strong quadrupole and sextupole magnets and very limited space. The former can result in very small vacuum chambers, increasing the coupling impedance and thus enhancing the beam instabilities, and the latter can pose significant challenges in accommodating the necessary diagnostics and vacuum components. Inspired by the hybrid MBA lattice concept, in this paper we propose a new unit lattice concept called the complex unit lattice cell, which can reduce the magnet strengths and also save space. The complex unit cell is numerically studied using a simplified model. Then as an example, a 17BA lattice based on the complex unit cell concept is designed for a 3 GeV storage ring light source with a circumference of 537.6 m, which has a natural emittance of 19.3 pm.rad. This 17BA lattice is also compared with the 17BA lattice designed with conventional unit cells to showcase the benefits of the complex unit cell concept. This 17BA lattice also suggests a new type of MBA lattice, which we call the MBA lattice with semi-distributed chromatic correction. △ Less

Submitted 19 August, 2023; originally announced August 2023.