Showing 1–50 of 84 results for author: Fu, J

The Cryogenic System of DMRadio-50L

Authors: V. Ankel, C. Bartram, J. Begin, C. Bell, S. Chaudhuri, H. -M. Cho, J. Corbin, W. Craddock, S. Cuadra, A. Droster, J. Echevers, E. Engelhardt, J. T. Fry, J. Fu, K. D. Irwin, A. Keller, R. Kolevatov, A. Kunder, D. Li, M. Marangola, N. Otto, K. M. W. Pappas, E. Pariset, S. Puranam, P. Quassolo , et al. (14 additional authors not shown)

Abstract: The DMRadio-50L experiment is designed to search for axion dark matter in the 5 kHz - 5 MHz frequency range using a lumped-element LC resonator and a toroidal magnet and to serve as a testbed for quantum sensors. This paper describes the custom cryogenic system developed to meet the stringent requirements of the experiment within a standard laboratory environment. The system is designed to cool a… ▽ More The DMRadio-50L experiment is designed to search for axion dark matter in the 5 kHz - 5 MHz frequency range using a lumped-element LC resonator and a toroidal magnet and to serve as a testbed for quantum sensors. This paper describes the custom cryogenic system developed to meet the stringent requirements of the experiment within a standard laboratory environment. The system is designed to cool a 200 kg detector assembly to temperatures as low as 50 mK while providing sufficient cooling power at multiple temperature stages. We present the conceptual design, technical implementation, and measured performance of the hybrid cryogenic system, which combines a horizontal dilution refrigerator with a large vertical payload cryostat. △ Less

Submitted 6 July, 2026; originally announced July 2026.

Finite-Size Effect Induced Spatial-Spectral Mode Splitting in Membrane Metasurfaces

Authors: Chih-Zong Deng, Mu-Hsin Chen, Chun-Hao Chiang, Jui-Han Fu, Vincent Tung, Masanobu Iwanaga, Ya-Lun Ho

Abstract: This work reports the spatial-spectral engineering and finite-size quantization of optical modes within a triangular-lattice silicon nitride membrane metasurface. Truncating the lattice into a finite square cavity breaks translational symmetry and lifts modal degeneracy, splitting optical modes into discrete cavity-envelope sub-modes. High-resolution photoluminescence (PL) scanning reveals distinc… ▽ More This work reports the spatial-spectral engineering and finite-size quantization of optical modes within a triangular-lattice silicon nitride membrane metasurface. Truncating the lattice into a finite square cavity breaks translational symmetry and lifts modal degeneracy, splitting optical modes into discrete cavity-envelope sub-modes. High-resolution photoluminescence (PL) scanning reveals distinct spatial field distributions. The corner-localized sub-mode features the highest Q-factor due to multipolar far-field destructive interference, whereas the core-localized sub-mode exhibits strong radiative coupling. PL mapping reveals a symmetric, four-fold clover-like wavelength arrangement. These results demonstrate that boundary-induced deterministic symmetry can override underlying lattice characteristics, offering a robust strategy for precise spatial-spectral tailoring of light-matter interactions at the nanoscale. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Rare Earth Ion Coupling Implements Attention-Like Reservoir Computing

Authors: Junyan Chen, Xinzhe Li, Jinsong Fu, Axin Du, Jinfeng Yao, Shuang Gao, Wenzhao Sun, Limin Jin, Can Huang, Qinghai Song

Abstract: We present a physical computing paradigm that harnesses the intrinsic nonlinear dynamics of rare earth doped core shell nanoparticles as a computational substrate. By directly exploiting cross relaxation and energy transfer upconversion processes, the system realizes a state dependent transfer function whose effective decay rate evolves with the instantaneous Er3+ population, which mathematically… ▽ More We present a physical computing paradigm that harnesses the intrinsic nonlinear dynamics of rare earth doped core shell nanoparticles as a computational substrate. By directly exploiting cross relaxation and energy transfer upconversion processes, the system realizes a state dependent transfer function whose effective decay rate evolves with the instantaneous Er3+ population, which mathematically analogous to gating and attention mechanisms in recurrent neural networks. The three spectrally resolved emission channels inherently span disparate timescales, endowing the reservoir with native multitimescale feature extraction without auxiliary engineering. Under the reservoir computing framework, the coupled three channel system achieves a total memory capacity exceeding fourfold that of a single ion reservoir; capacity decomposition further reveals that the nonzero cross memory capacity is a direct signature of many body Tm3+@Er3+ coupling. On the Mackey Glass and Santa Fe chaotic benchmarks, the system attains normalized mean squared errors of 1.2x10-3 and 2.1x10-2, respectively, with only 125 virtual nodes. These results establish rare earth nanoparticles as a compelling platform for compact and hardware integrable neuromorphic computing, and introduce "inward evolution", the deliberate exploitation of intra material quantum dynamics, as a generalizable design principle for next generation physical computing systems. △ Less

Submitted 29 June, 2026; originally announced June 2026.

Rapid and robust laser-frequency auto-locking using Bayesian-optimization and discrete-wavelet-transformation algorithms

Authors: Min Jiang, Xiao-Li Chen, Si-Bin Lu, Jia-Hao Fu, Zhan-Wei Yao, Shao-Kang Li, Min Ke, San-Ming Song, Run-Bing Li, Jin Wang, Ming-Sheng Zhan

Abstract: Rapid and robust laser-frequency auto-locking is essential for the field deployment of quantum communications, quantum computing, and precision-measurement technologies; however, achieving this remains a considerable challenge. Here, we propose and demonstrate an auto-locking scheme employing Bayesian optimization and discrete biorthogonal wavelet transformation. First, the reference is rapidly so… ▽ More Rapid and robust laser-frequency auto-locking is essential for the field deployment of quantum communications, quantum computing, and precision-measurement technologies; however, achieving this remains a considerable challenge. Here, we propose and demonstrate an auto-locking scheme employing Bayesian optimization and discrete biorthogonal wavelet transformation. First, the reference is rapidly sought by making intelligent use of historical observations, eliminating the inherent blindness of the traditional parameter-scanning method. Second, the frequency reference is robustly identified by pinpointing transition signals with the discrete biorthogonal wavelet transformation and analyzing their immutable frequency differences and relative magnitudes, which are determined by the inherent atomic structure and remain resistant to environmental disturbances. This proposed approach achieves a fivefold acceleration in reference searching compared to conventional scanning methods in the case where the laser frequency drifts far away from the reference. Crucially, it achieves an identification accuracy of more than 99.5 %, even under severe 50 % laser-intensity fluctuations, $9.95^\circ$ photodiode misalignment, and $18^\circ$C Rb cell temperature elevation. Finally, locking the laser frequency to the identified reference with a lead zirconate titanate-current double-servo loop narrows the linewidth to 20 kHz. We believe that this rapid, robust, and high-performance auto-locking technique will be pivotal towards the deployment of the next generation of practical quantum technologies in demanding field environments. △ Less

Submitted 23 June, 2026; originally announced June 2026.

Comments: 9 pages, 8 figures. Submitted to Review of Scientific Instruments

Steering Selective Formation and 2D Crystallization of [4]Radialenes on Au(111) via [1+1+1+1] Cycloaddition of Isocyanides and Enantioselective Molecular Recognition

Authors: Jian-Wei Liu, Ying Wang, Cui-Ping Wu, Jia-Xin Li, Li-Xia Kang, Jian-Hui Fu, Wen-Wen Gong, Pei-Nian Liu, Deng-Yuan Li

Abstract: Conjugated carbon rings are fundamental skeletons of organic functional materials, and their selective formation is of paramount importance in molecular materials engineering. However, steering the formation and 2D crystallization of conjugated carbon rings on the surface with high chemo- and stereoselectivities remains a great challenge. Here, we report a highly chemoselective [1+1+1+1] cycloaddi… ▽ More Conjugated carbon rings are fundamental skeletons of organic functional materials, and their selective formation is of paramount importance in molecular materials engineering. However, steering the formation and 2D crystallization of conjugated carbon rings on the surface with high chemo- and stereoselectivities remains a great challenge. Here, we report a highly chemoselective [1+1+1+1] cycloaddition of isocyanides on the Au(111) surface, which affords the stereospecific tetraaza[4]radialene products and further enables their long-range-ordered 2D crystallization via enantioselective molecular recognition. Using the progressive annealing method, we found that at room temperature, isocyanides undergo a coordination reaction with Au adatoms to form two-fold symmetric isocyanide-Au-isocyanide complexes. In contrast, gradually increasing the annealing temperature induces the transformation of these complexes and subsequent covalent polymerization, leading to the selective generation of tetraaza[4]radialenes with homotactic configurations. The tetraaza[4]radialenes further assemble into 2D homochiral molecular crystals through enantioselective molecular recognition driven by multiple C-H -- Cl hydrogen-bonding interactions. By combining scanning tunneling microscopy/spectroscopy and non-contact atomic force microscopy, we determined the atomic structure and molecular orbitals of tetraaza[4]radialene, confirming that its four-membered ring adopts a planar geometry with a localized lowest unoccupied molecular orbital. Density functional theory calculations suggest that the [1+1+1+1] cycloaddition process involves stepwise formation of C-C bonds and its high selectivity arises from the spatial steric hindrance. Our findings provide new insights into the selective formation of conjugated rings on surfaces and have implications for engineering 2D homochiral molecular crystallization. △ Less

Submitted 6 June, 2026; originally announced June 2026.

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

PRBench: End-to-end Paper Reproduction in Physics Research

Authors: Shi Qiu, Junyi Deng, Yiwei Deng, Haoran Dong, Jieyu Fu, Mao Li, Zeyu Li, Zhaolong Zhang, Huiwen Zheng, Leidong Bao, Anqi Lv, Zihan Mo, Yadi Niu, Yiyang Peng, Yu Tian, Yili Wang, Ziyu Wang, Zi-Yu Wang, Jiashen Wei, Liuheng Wu, Aoran Xue, Leyi Yang, Guanglu Yuan, Xiarui Zhan, Jingjun Zhang , et al. (26 additional authors not shown)

Abstract: AI agents powered by large language models exhibit strong reasoning and problem-solving capabilities, enabling them to assist scientific research tasks such as formula derivation and code generation. However, whether these agents can reliably perform end-to-end reproduction from real scientific papers remains an open question. We introduce PRBench, a benchmark of 30 expert-curated tasks spanning 1… ▽ More AI agents powered by large language models exhibit strong reasoning and problem-solving capabilities, enabling them to assist scientific research tasks such as formula derivation and code generation. However, whether these agents can reliably perform end-to-end reproduction from real scientific papers remains an open question. We introduce PRBench, a benchmark of 30 expert-curated tasks spanning 11 subfields of physics. Each task requires an agent to comprehend the methodology of a published paper, implement the corresponding algorithms from scratch, and produce quantitative results matching the original publication. Agents are provided only with the task instruction and paper content, and operate in a sandboxed execution environment. All tasks are contributed by domain experts from over 20 research groups at the School of Physics, Peking University, each grounded in a real published paper and validated through end-to-end reproduction with verified ground-truth results and detailed scoring rubrics. Using an agentified assessment pipeline, we evaluate a set of coding agents on PRBench and analyze their capabilities across key dimensions of scientific reasoning and execution. The best-performing agent, OpenAI Codex powered by GPT-5.3-Codex, achieves a mean overall score of 34%. All agents exhibit a zero end-to-end callback success rate, with particularly poor performance in data accuracy and code correctness. We further identify systematic failure modes, including errors in formula implementation, inability to debug numerical simulations, and fabrication of output data. Overall, PRBench provides a rigorous benchmark for evaluating progress toward autonomous scientific research. △ Less

Submitted 29 March, 2026; originally announced March 2026.

Comments: 17 pages, 3 figures

Report number: RISE-AGI-2026-002

Beam-Plasma Collective Oscillations in Intense Charged-Particle Beams: Dielectric Response Theory, Langmuir Wave Dispersion, and Unsupervised Detection via Prometheus

Authors: Brandon Yee, Wilson Collins, Michael Iofin, Jiayi Fu

Abstract: We develop a theoretical and computational framework for beam-plasma collective oscillations in intense charged-particle beams at intermediate energies (10-100 MeV). In Part I, we formulate a kinetic field theory governed by the Vlasov-Poisson system, deriving the Lindhard dielectric function and random phase approximation (RPA) polarization tensor for three beam distribution functions. We prove v… ▽ More We develop a theoretical and computational framework for beam-plasma collective oscillations in intense charged-particle beams at intermediate energies (10-100 MeV). In Part I, we formulate a kinetic field theory governed by the Vlasov-Poisson system, deriving the Lindhard dielectric function and random phase approximation (RPA) polarization tensor for three beam distribution functions. We prove via the dielectric function epsilon(omega,q)=0 the existence of undamped Langmuir wave modes above a critical beam density n_c, obtain explicit beam-plasma dispersion relations, and show that Landau damping vanishes above the particle-hole continuum. The plasma frequency Omega_p^2 = ne^2/(m*epsilon_0) is fixed by the f-sum rule independently of distribution shape; higher dispersion coefficients depend on velocity moments. Space charge effects drive anomalous beam broadening with sqrt(n-n_c) onset and Friedel oscillations at q=2k_F. The beam-plasma transition belongs to the 3D Ising universality class via renormalization group analysis. In Part II, we validate these predictions using Prometheus, a beta-VAE trained on static structure factor data S(q) from particle-in-cell (PIC) beam simulations. Prometheus detects collective plasma oscillation onset in Gaussian and uniform distributions, confirms their absence in the degenerate Fermi gas (n_c -> 0), and resolves the Kohn anomaly at q=2k_F. Dispersion analysis of S(q,omega) from PIC simulations verifies the distribution-independent Omega_p predicted by the f-sum rule. All six validation checks pass. Predicted signatures -- density-tunable plasma resonances at omega_p proportional to sqrt(n), anomalous beam broadening with sqrt(n-n_c) onset, and Friedel oscillations -- are accessible at existing intermediate-energy beam facilities. △ Less

Submitted 4 June, 2026; v1 submitted 11 March, 2026; originally announced March 2026.

Comments: Substantial Revision Required

Variance-Driven Mean Temperature Reduction in Nonuniformly Heated Radiative-Conductive Systems

Authors: Juntao Lu, Zihan Zhang, Yongjian Xiong, Jie Fu

Abstract: Radiative-conductive systems are intrinsically nonlinear due to the quartic temperature dependence of thermal radiation. Under fixed total heating power, convexity arguments imply that nonuniform temperature distributions radiate more efficiently and therefore exhibit a lower mean temperature than their isothermal counterparts. However, this conclusion remains qualitative, and an explicit quantita… ▽ More Radiative-conductive systems are intrinsically nonlinear due to the quartic temperature dependence of thermal radiation. Under fixed total heating power, convexity arguments imply that nonuniform temperature distributions radiate more efficiently and therefore exhibit a lower mean temperature than their isothermal counterparts. However, this conclusion remains qualitative, and an explicit quantitative relation between temperature heterogeneity and mean temperature reduction has been lacking. Here we derive a variance-based analytical expression linking the area-averaged temperature to the corresponding isothermal equilibrium temperature in a nonuniformly heated radiative--conductive system. By integrating the governing equation and performing a systematic second-order expansion about the ambient temperature, we show that the decrease of the mean temperature relative to the isothermal equilibrium value is linearly proportional to the temperature variance, with a proportionality coefficient set solely by the ambient temperature. This result transforms the convexity-based inequality into a quantitative statistical relation within the perturbative regime and provides a physically transparent framework for describing nonlinear radiative averaging in thermally heterogeneous systems. △ Less

Submitted 4 March, 2026; originally announced March 2026.

Photonic Neuromorphic Computing enabled by a BIC Metasurface

Authors: Jingsong Fu, Ruiheng Jin, Zhaohui Xie, Haijun Tang, Xiong Jiang, Yue Cui, Xiangtong Kong, Wentao Hao, Geyang Qu, Can Huang, Qingha Song

Abstract: Photonic neuromorphic computing promises revolutionary advances in parallel and high-speed processing, yet a key challenge persists: co-integrating nonlinearity, dense connectivity, and intrinsic memory monolithically to enable brain-inspired, spatiotemporal information processing. Here, we overcome this challenge by introducing a monolithic photonic recurrent network based on an active metasurfac… ▽ More Photonic neuromorphic computing promises revolutionary advances in parallel and high-speed processing, yet a key challenge persists: co-integrating nonlinearity, dense connectivity, and intrinsic memory monolithically to enable brain-inspired, spatiotemporal information processing. Here, we overcome this challenge by introducing a monolithic photonic recurrent network based on an active metasurface operating at bound state in the continuum (BIC). The BIC mode mediates strong,long-range coupling across the lattice, creating a reconfigurable recurrent network topology in hardware. Concurrently, the gain medium provides both optical nonlinearity for neuronal activation and a finite carrier lifetime that serves as a built in, analog temporal memory. This synergy enables computation to emerge directly from the collective spatiotemporal dynamics of the driven-dissipative photonic system, effectively realizing a physical reservoir computer on a chip. We experimentally validate a minimal yet physically complete system on benchmark tasks: brain MRI image classification and human action recognition, achieving 92.16% and 85.36% accuracies, respectively. This work establishes a scalable pathway toward ultrafast, energy-efficient neuromorphic intelligence where processing is an inherent property of tailored light matter interaction. △ Less

Submitted 25 February, 2026; originally announced February 2026.

Freestanding Resist Metasurface Supporting Higher-Order BICs for Efficient Field Enhancement in TMD Monolayers

Authors: Chih-Zong Deng, Sunhao Shi, Chun-Hao Chiang, Mu-Hsin Chen, Jui-Han Fu, Vincent Tung, Ya-Lun Ho

Abstract: Enhancing light-matter coupling in two-dimensional (2D) semiconductors such as transition metal dichalcogenide monolayers remains a central challenge in nanophotonics due to their atomic thickness, which limits their interaction volume with light. Here, we demonstrate that first-order quasi-bound states in the continuum (quasi-BICs) supported by a freestanding metasurface provide exceptionally str… ▽ More Enhancing light-matter coupling in two-dimensional (2D) semiconductors such as transition metal dichalcogenide monolayers remains a central challenge in nanophotonics due to their atomic thickness, which limits their interaction volume with light. Here, we demonstrate that first-order quasi-bound states in the continuum (quasi-BICs) supported by a freestanding metasurface provide exceptionally strong surface field enhancement, enabling efficient coupling with a tungsten disulfide (WS2) monolayer. Triangular-lattice polymer patterns on silicon nitride membranes are fabricated to realize these higher-order modes. Simulations reveal that first-order quasi-BICs exhibit much stronger field enhancement than zeroth-order modes at the top surface where the WS2 monolayer is placed. Photoluminescence (PL) measurements confirm a remarkable PL enhancement factor of 127 for first-order quasi-BICs, over six times larger than that of zeroth-order quasi-BICs. These results establish higher-order BICs in freestanding metasurfaces as a powerful route to engineer light-matter interactions in 2D semiconductors for advanced nanophotonic and quantum photonic applications. △ Less

Submitted 5 January, 2026; originally announced January 2026.

Beam-test evaluation of pre-production Low Gain Avalanche Detectors for the ATLAS High Granularity Timing Detector

Authors: A. Aboulhorma, M. Ait Tamlihat, H. M. Alfanda, O. Atanova, N. Atanov, I. Azzouzi, J. Barreiro Guimarães da Costa, T. Beau, D. Benchekroun, F. Bendebba, G. Bergamin, Y. Bimgdi, A. Blot, A. Boikov, J. Bonis, D. Boumediene, C. Brito, A. S. Brogna, A. M. Burger, L. Cadamuro, Y. Cai, N. Cartalade, R. Casanova Mohr, R. Cherkaoui El Moursli, Y. Che , et al. (207 additional authors not shown)

Abstract: The High Granularity Timing Detector (HGTD) will be installed in the ATLAS experiment as part of the Phase-II upgrade for the High Luminosity-Large Hadron Collider (HL-LHC). It will mitigate pile-up effects in the forward region, and measure per bunch luminosity. The design of HGTD is based on Low Gain Avalanche Detector (LGAD) sensors. This paper presents the results of beam-test campaigns conduc… ▽ More The High Granularity Timing Detector (HGTD) will be installed in the ATLAS experiment as part of the Phase-II upgrade for the High Luminosity-Large Hadron Collider (HL-LHC). It will mitigate pile-up effects in the forward region, and measure per bunch luminosity. The design of HGTD is based on Low Gain Avalanche Detector (LGAD) sensors. This paper presents the results of beam-test campaigns conducted at CERN and DESY in 2023 and 2024 on single LGADs from HGTD pre-production test structures, before and after neutron irradiation up to fluences of $2.5 \times 10^{15}~\mathrm{n_{eq}/cm^2}$. The tested LGADs can meet HGTD requirements in terms of charge collection, time resolution, and hit efficiency, even under HL-LHC end-of-life conditions, supporting their deployment in the final detector. △ Less

Submitted 30 January, 2026; v1 submitted 1 December, 2025; originally announced December 2025.

Nonlinear Unsteady Vortex-Lattice Vortex-Particle Method with Adaptive Wake Conversion for Rotorcraft Aerodynamics

Authors: Jinbin Fu, Eric Laurendeau

Abstract: Nonlinear unsteady vortex lattice-vortex particle methods (NL-UVLM-VPM) provide medium-fidelity predictions of rotorcraft aerodynamics with explicit three-dimensional wake representations at a moderate computational cost. This study presents an NL-UVLM-VPM approach with a scale-consistent adaptive wake panel-particle conversion strategy that mitigates the inherent temporal-spatial resolution coupl… ▽ More Nonlinear unsteady vortex lattice-vortex particle methods (NL-UVLM-VPM) provide medium-fidelity predictions of rotorcraft aerodynamics with explicit three-dimensional wake representations at a moderate computational cost. This study presents an NL-UVLM-VPM approach with a scale-consistent adaptive wake panel-particle conversion strategy that mitigates the inherent temporal-spatial resolution coupling of conventional wake treatments in rotorcraft aerodynamic simulations. Numerical assessment shows that this strategy preserves the near third-order temporal convergence of the underlying time-integration scheme while improving robustness under coarsened temporal resolution. For a representative hover case, computational time is reduced by 29% relative to the conventional conversion strategy at identical temporal resolution and by nearly 70% compared with a fine-resolution reference simulation over 20 rotor revolutions, while maintaining thrust and torque predictions within 1% of the reference solution. Based on these analyzes, practical recommendations for particle conversion parameters and wake resolution are provided. The methodology is further validated for increasingly complex scenarios, including hover, forward flight with blade-vortex interaction, and multirotor interaction. Predictions show good agreement with experimental data and dedicated unsteady Reynolds-averaged Navier-Stokes simulations (URANS), while computational speedups exceeding two orders of magnitude relative to URANS are achieved. △ Less

Submitted 14 March, 2026; v1 submitted 14 November, 2025; originally announced November 2025.

High Bandwidth and Ultra-low Dark Current Ge Photodetector Enabled by Frequency Domain Equalization

Authors: Wenxin Deng, Hengsong Yue, Xiaoyan Liu, Jianhong Liang, Jianbin Fu, Shilong Pan, Tao Chu

Abstract: High bandwidth and low dark current germanium (Ge) photodetectors are crucial in silicon photonic integrated circuits. The bandwidth of Ge photodetectors is restricted by carrier transit time and parasitic parameters. And thermal generation of carriers within the Ge P-N junction results in an inherent dark current, typically in nA-μA range. Here, we propose an equalization photodetector (EqPD) uti… ▽ More High bandwidth and low dark current germanium (Ge) photodetectors are crucial in silicon photonic integrated circuits. The bandwidth of Ge photodetectors is restricted by carrier transit time and parasitic parameters. And thermal generation of carriers within the Ge P-N junction results in an inherent dark current, typically in nA-μA range. Here, we propose an equalization photodetector (EqPD) utilizing the frequency response of a high-bandwidth photodetector PDA to subtract the frequency response of a low-bandwidth photodetector PDB. With the response of PDB attenuating more severely than PDA at high frequency, the differential response (the response of EqPD) can get higher values at high-frequency than at low-frequency. The dark current of EqPD can also be significantly reduced with PDB balancing the dark current of PDA. Experimental results show that the bandwidth of our proposed photodetector can be expanded to over 110 GHz with a dark current of 1 pA simultaneously, and its Non-Return-to-Zero (NRZ) transmission speed can reach 100 Gbaud without digital signal processing. To the best of our knowledge, this represents the highest bandwidth and lowest dark current in a vertical Ge photodetector. The high-performance EqPD provides a promising solution for high-speed and ultra-low noise photodetection in next-generation optical communication. △ Less

Submitted 15 October, 2025; originally announced October 2025.

Thermal Cycling Reliability of Hybrid Pixel Sensor Modules for The ATLAS High Granularity Timing Detector

Authors: Y. Li, A. Aboulhorma, M. Ait Tamlihat, H. M. Alfanda, N. Atanov, O. Atanova, I. Azzouzi, J. Barreiro Guimarães Da Costa, T. Beau, D. Benchekroun, F. Bendebba, Y. Bimgdi, A. Blot, A. Boikov, J. Bonis, D. Boumediene, C. Brito, A. S. Brogna, A. M. Burger, L. Cadamuro, Y. Cai, N. Cartalade, R. Casanova Mohr, Y. Che, X. Chen , et al. (203 additional authors not shown)

Abstract: The reliability of bump connection structures has become a critical aspect of future silicon detectors for particle physics. The High Granularity Timing Detector (HGTD) for the ATLAS experiment at the High-Luminosity Large Hadron Collider will require 8032 hybrid pixel sensor modules, composed of two Low Gain Avalanche Diode sensors bump-bonded to two readout ASICs and glued to a passive PCB. The… ▽ More The reliability of bump connection structures has become a critical aspect of future silicon detectors for particle physics. The High Granularity Timing Detector (HGTD) for the ATLAS experiment at the High-Luminosity Large Hadron Collider will require 8032 hybrid pixel sensor modules, composed of two Low Gain Avalanche Diode sensors bump-bonded to two readout ASICs and glued to a passive PCB. The detector will operate at low temperature (-30 degrees Celsius) to mitigate the impact of irradiation. The thermomechanical reliability of flip-chip bump connections in HGTD modules is a critical concern, particularly due to their characteristically lower bump density (pixel pitch dimensions of 1.3 mm by 1.3 mm). This paper elaborates on the challenges arising from this design characteristic. Finite element analysis and experimental testing were employed to investigate failure modes in the flip-chip bump structures under thermal cycling from -45 degrees Celsius to 40 degrees Celsius and to guide the module redesign. The optimized design demonstrates significantly enhanced robustness and is projected to fulfill the full lifetime requirements of the HGTD. △ Less

Submitted 17 September, 2025; originally announced September 2025.

Comments: 15 pages, 12 figures, 7 tables

Compact All optical Reservoir Computing via Luminescence Dynamics in Rare-earth Ions-doped Nanocrystals

Authors: Junyan Chen, Jingsong Fu, Jie Xu, Yixiang Qin, Axin Du, Kaiyang Wang, Limin Jin, Can Huang

Abstract: Optical neuromorphic computing offers a promising route to high speed, energy efficient information processing. However, photonic neurons, as the critical components for enhancing computational expressivity, still face significant bottlenecks in nonlinear mapping and memory capacity. Here, we demonstrate an all optical reservoir computing system based on rare earth ions doped nanocrystals for the… ▽ More Optical neuromorphic computing offers a promising route to high speed, energy efficient information processing. However, photonic neurons, as the critical components for enhancing computational expressivity, still face significant bottlenecks in nonlinear mapping and memory capacity. Here, we demonstrate an all optical reservoir computing system based on rare earth ions doped nanocrystals for the first time, leveraging their intrinsic nonlinear luminescence dynamics and multitimescale memory. Unlike traditional schemes that require bulky optical delays or intricate resonant structures, our platform exploits the material's inherent properties: nonlinear cross-relaxation processes enable nonlinear mapping while millisecond-scale metastable energy levels provide fading memory. As a proof of concept, we achieve 90.7% accuracy in MNIST digit classification and low-error chaotic time-series prediction (NRMSE < 0.1) using the rare-earth ions based system. Our work significantly reduce system footprint and complexity, offering a scalable, fully optical solution for edge computing and real-time neuromorphic applications. △ Less

Submitted 21 August, 2025; originally announced August 2025.

Large-Area Photonic Membranes Achieving Uniform and Strong Enhancement of Photoluminescence and Second-Harmonic Generation in Monolayer WSe2

Authors: Fong-Liang Hsieh, Chih-Zong Deng, Shao-Ku Huang, Tsung-Hsin Liu, Chun-Hao Chiang, Che-Lun Lee, Man-Hong Lai, Jui-Han Fu, Vincent Tung, Yu-Ming Chang, Chun-Wei Chen, Ya-Lun Ho

Abstract: Two dimensional transition metal dichalcogenides exhibit strong excitonic responses, direct bandgaps, and remarkable nonlinear optical properties, making them highly attractive for integrated photonic, optoelectronic, and quantum applications. Here, we present a large area freestanding membrane photonic platform that achieves exceptional enhancement of light matter interactions in monolayer WSe2 v… ▽ More Two dimensional transition metal dichalcogenides exhibit strong excitonic responses, direct bandgaps, and remarkable nonlinear optical properties, making them highly attractive for integrated photonic, optoelectronic, and quantum applications. Here, we present a large area freestanding membrane photonic platform that achieves exceptional enhancement of light matter interactions in monolayer WSe2 via quasi bound states in the continuum. The freestanding architecture effectively suppresses radiative losses and supports high Q optical resonances, leading to enhanced light matter interactions. This results in significant photoluminescence emission and second harmonic generation enhancement factors of 1158 and 378, respectively, with spatial uniformity sustained across a 450 times 450 um2 area. This uniform SHG enhancement further enables polarization resolved mapping of crystal orientation and grain boundaries, offering a practical method for large area structural characterization of 2D materials. Moreover, femtosecond pumped SHG spectra reveal multiple narrowband peaks originating from distinct quasi BIC modes providing direct spectral evidence of resonantly enhanced nonlinear coupling. The combined attributes of strong optical enhancement, spectral selectivity, and wafer scale compatibility establish this platform as a scalable interface for 2D semiconductor integration in next generation optoelectronic, nonlinear, and quantum photonic technologies. △ Less

Submitted 5 August, 2025; v1 submitted 1 August, 2025; originally announced August 2025.

Atomic-Scale Light Coupling Control in Ultrathin Photonic Nanomembranes

Authors: Chih-Zong Deng, Chun-Hao Chiang, Sunhao Shih, Jui-Han Fu, Yen-Ju Wu, Kuniaki Konishi, Vincent Tung, Chun-Wei Chen, Ya-Lun Ho

Abstract: Atomic-layer and two-dimensional (2D) materials have emerged as essential building blocks for next-generation quantum and semiconductor technologies, where atomic-scale control over light-matter interactions is critical. However, their inherently small interaction volume poses fundamental challenges for efficient integration into quantum and nanophotonic devices. Addressing this limitation require… ▽ More Atomic-layer and two-dimensional (2D) materials have emerged as essential building blocks for next-generation quantum and semiconductor technologies, where atomic-scale control over light-matter interactions is critical. However, their inherently small interaction volume poses fundamental challenges for efficient integration into quantum and nanophotonic devices. Addressing this limitation requires the development of photonic platforms that can effectively enhance atomic-scale optical coupling. To this end, freestanding nanomembranes with extreme thinness and minimal radiative loss offer an ideal framework for integrating these materials into photonic systems. Here, we demonstrate an ultrathin photonic nanomembrane enabling atomic-scale control of light coupling. This architecture supports strong field confinement at the surface and significantly enhances light-matter interaction. Through the integration of atomic-layer dielectrics, we achieve Å-level thickness modulation, where each deposition cycle leads to an ultrafine shift of the high-Q resonance. High-resolution spatial mapping further confirms uniform and deterministic resonance tuning across the nanomembrane surface. Furthermore, by integrating a WS2 monolayer with the photonic nanomembrane, strong field localization within the monolayer and a significant emission enhancement are achieved. This approach offers a scalable and versatile route for atomic-scale light coupling, helping to overcome the limitations of conventional photonics and opening opportunities in quantum photonics, optoelectronics, and advanced semiconductor technologies. △ Less

Submitted 16 October, 2025; v1 submitted 31 July, 2025; originally announced July 2025.

Quantifying Key Design Factors for Thermal Comfort in Underground Space Through Global Sensitivity Analysis and Machine Learning

Authors: Shisheng Chen, Nyuk Hien Wong, Chao Cen, Ruohan Xu, Lei Xu, Zhenjiang Shen, Zhigang Wu, Jiayan Fu, Zhongqi Yu

Abstract: This study identified the key design factors related to thermal comfort in naturally ventilated underground spaces under high temperature conditions (outdoor Tmax = 42.9 C) in Fuzhou, China. Fuzhou has a humid subtropical climate and is one of the three hottest cities in China in 2024. Daytime measurements indicated reduced air temperature (AT), mean radiant temperature (MRT), and wind speed (V),… ▽ More This study identified the key design factors related to thermal comfort in naturally ventilated underground spaces under high temperature conditions (outdoor Tmax = 42.9 C) in Fuzhou, China. Fuzhou has a humid subtropical climate and is one of the three hottest cities in China in 2024. Daytime measurements indicated reduced air temperature (AT), mean radiant temperature (MRT), and wind speed (V), together with elevated relative humidity (RH) in the underground space. Physiological Equivalent Temperature (PET) in the underground was consistently lower during peak hours (08:00-16:00), with the maximum difference in PET between pedestrian and underground levels being 11-11.9 C. Higher pedestrian-level PET at L1 was attributed to reduced greenery and shading, and decrement factors indicated greater thermal dampening at L2 (0.197) than at L1 (0.308). Sensitivity analysis showed that MRT was the most influential factor (S1/ST = 0.59-0.72) for aboveground spaces, followed by AT (0.13-0.26). In contrast, underground PET was mainly affected by metabolic rate (MET) (0.63-0.65), followed by RH (0.14-0.20) and V (0.08-0.18). Partial dependence analysis revealed that a 1 met increase in MET raised PET by 1.6 C, whereas a 1 m/s increase in V reduced PET by 1.5-2.2 C in the underground space. Due to cooler and more stable thermal conditions, underground spaces have higher tolerance for intensive physical activities. By buffering fluctuations in AT and MRT, underground environments can significantly alleviate heat stress and provide passive cooling shelter during daytime heat waves. Overall, this study provides empirical evidence to support underground space design in hot-humid climates and offers insights for sustainable urban heat mitigation. △ Less

Submitted 24 November, 2025; v1 submitted 21 July, 2025; originally announced July 2025.

Journal ref: Chen, Shisheng, et al. "Quantifying key design factors for thermal comfort in underground space through global sensitivity analysis and machine learning." Tunnelling and Underground Space Technology 169 (2026): 107282

Theoretical analysis for non-linear effects of magnetic fields on unsteady boundary layer flows

Authors: Jing-Yu Fu, Ming-Jiu Ni, Nian-Mei Zhang

Abstract: This study investigates unsteady boundary layer phenomena in electrically conducting fluids subjected to static magnetic fields. Using a semi-explicit similarity transformation method, the momentum equation associated with the Stokes stream function is solved. The nonlinear closed analytical solutions for both stagnation flow and converging flow are derived. The results demonstrate that the bounda… ▽ More This study investigates unsteady boundary layer phenomena in electrically conducting fluids subjected to static magnetic fields. Using a semi-explicit similarity transformation method, the momentum equation associated with the Stokes stream function is solved. The nonlinear closed analytical solutions for both stagnation flow and converging flow are derived. The results demonstrate that the boundary layer structure incorporates similar shock and solitary wave components which are promoted by Lorentz force. Under extreme magnetic fields, the flow exhibits sine and cosine wave patterns, which are motivated by the strong Lorentz force. An in-depth asymptotic analysis establishes the square root scaling laws that quantify the growth of friction and flux with increasing magnetic field strength. The boundary layer thickness scales inversely with the Hartmann number, a consequence of dominant Lorentz force, which differs from the conclusion of duct flow (Hunt 1965). These findings elucidate the physical mechanisms governing the nonlinear coupling between magnetic fields and the dynamics of the boundary layer. △ Less

Submitted 9 April, 2025; originally announced April 2025.

Beam test result and digitization of TaichuPix-3: A Monolithic Active Pixel Sensors for CEPC vertex detector

Authors: Hancen Lu, Tianyuan Zhang, Chang Xu, Shuqi Li, Xinhui Huang, Jia Zhou, Ziyue Yan, Wei Wang, Hao Zeng, Xuewei Jia, Yiming Hu, Xiaoxu Zhang, Zhijun Liang, Wei Wei, Ying Zhang, Xiaomin Wei, Tianya Wu, Lei Zhang, Ming Qi, Jun Hu, Jinyu Fu, Hongyu Zhang, Gang Li, Linghui Wu, Mingyi Dong , et al. (9 additional authors not shown)

Abstract: The Circular Electron-Positron Collider (CEPC), as the next-generation electron-positron collider, is tasked with advancing not only Higgs physics but also the discovery of new physics. Achieving these goals requires high-precision measurements of particles. Taichu seires, Monolithic Active Pixel Sensor (MAPS), a key component of the vertex detector for CEPC was designed to meet the CEPC's require… ▽ More The Circular Electron-Positron Collider (CEPC), as the next-generation electron-positron collider, is tasked with advancing not only Higgs physics but also the discovery of new physics. Achieving these goals requires high-precision measurements of particles. Taichu seires, Monolithic Active Pixel Sensor (MAPS), a key component of the vertex detector for CEPC was designed to meet the CEPC's requirements. For the geometry of vertex detector is long barrel with no endcap, and current silicon lacks a complete digitization model, precise estimation of cluster size particularly causing by particle with large incident angle is needed. Testbeam results were conducted at the Beijing Synchrotron Radiation Facility (BSRF) to evaluate cluster size dependence on different incident angles and threshold settings. Experimental results confirmed that cluster size increases with incident angle. Simulations using the Allpix$^2$ framework replicated experimental trends at small angles but exhibited discrepancies at large angles, suggesting limitations in linear electric field assumptions and sensor thickness approximations. The results from both testbeam and simulations have provided insights into the performance of the TaichuPix chip at large incident angles, offering a crucial foundation for the establishment of a digital model and addressing the estimation of cluster size in the forward region of the long barrel. Furthermore, it offers valuable references for future iterations of TaichuPix, the development of digital models, and the simulation and estimation of the vertex detector's performance. △ Less

Submitted 10 March, 2025; v1 submitted 7 March, 2025; originally announced March 2025.

Machine learning for modelling unstructured grid data in computational physics: a review

Authors: Sibo Cheng, Marc Bocquet, Weiping Ding, Tobias Sebastian Finn, Rui Fu, Jinlong Fu, Yike Guo, Eleda Johnson, Siyi Li, Che Liu, Eric Newton Moro, Jie Pan, Matthew Piggott, Cesar Quilodran, Prakhar Sharma, Kun Wang, Dunhui Xiao, Xiao Xue, Yong Zeng, Mingrui Zhang, Hao Zhou, Kewei Zhu, Rossella Arcucci

Abstract: Unstructured grid data are essential for modelling complex geometries and dynamics in computational physics. Yet, their inherent irregularity presents significant challenges for conventional machine learning (ML) techniques. This paper provides a comprehensive review of advanced ML methodologies designed to handle unstructured grid data in high-dimensional dynamical systems. Key approaches discuss… ▽ More Unstructured grid data are essential for modelling complex geometries and dynamics in computational physics. Yet, their inherent irregularity presents significant challenges for conventional machine learning (ML) techniques. This paper provides a comprehensive review of advanced ML methodologies designed to handle unstructured grid data in high-dimensional dynamical systems. Key approaches discussed include graph neural networks, transformer models with spatial attention mechanisms, interpolation-integrated ML methods, and meshless techniques such as physics-informed neural networks. These methodologies have proven effective across diverse fields, including fluid dynamics and environmental simulations. This review is intended as a guidebook for computational scientists seeking to apply ML approaches to unstructured grid data in their domains, as well as for ML researchers looking to address challenges in computational physics. It places special focus on how ML methods can overcome the inherent limitations of traditional numerical techniques and, conversely, how insights from computational physics can inform ML development. To support benchmarking, this review also provides a summary of open-access datasets of unstructured grid data in computational physics. Finally, emerging directions such as generative models with unstructured data, reinforcement learning for mesh generation, and hybrid physics-data-driven paradigms are discussed to inspire future advancements in this evolving field. △ Less

Submitted 13 February, 2025; originally announced February 2025.

All-optical and ultrafast control of high-order exciton-polariton orbital modes

Authors: Yuyang Zhang, Xin Zeng, Wenna Du, Zhiyong Zhang, Yuexing Xia, Jiepeng Song, Jianhui Fu, Shuai Zhang, Yangguang Zhong, Yubo Tian, Yiyang Gong, Shuai Yue, Yuanyuan Zheng, Xiaotian Bao, Yutong Zhang, Qing Zhang, Xinfeng Liu

Abstract: Exciton-polaritons flows within closed quantum circuits can spontaneously form phase-locked modes that carry orbital angular momentum (OAM). With its infinite set of angular momentum quantum numbers, high-order OAM represents a transformative solution to the bandwidth bottleneck in multiplexed optical communication. However, its practical application is hindered by the limited choice of materials… ▽ More Exciton-polaritons flows within closed quantum circuits can spontaneously form phase-locked modes that carry orbital angular momentum (OAM). With its infinite set of angular momentum quantum numbers, high-order OAM represents a transformative solution to the bandwidth bottleneck in multiplexed optical communication. However, its practical application is hindered by the limited choice of materials which in general requires cryogenic temperatures and the reliance on mechanical switching. In this work, we achieve stable and high-order (up to order of 33) OAM modes by constructing a closed quantum circuit using the halide perovskite microcavities at room temperature. By controlling the spatial and temporal symmetry of the closed quantum circuits using another laser pulse, we achieve significant tuning OAM of EP flows from 8 to 12. Our work demonstrate all-optical and ultrafast control of high-order OAM using exciton-polariton condensates in perovskite microcavities that would have important applications in high-throughput optical communications. △ Less

Submitted 12 February, 2025; originally announced February 2025.

Comments: 23 pages,5 figures

Stochastic reconstruction of multiphase composite microstructures using statistics-encoded neural network for poro/micro-mechanical modelling

Authors: Jinlong Fu, Wei Tan

Abstract: Understanding microstructure-property relationships (MPRs) is essential for optimising the performance of multiphase composites. Image-based poro/micro-mechanical modelling provides a non-invasive approach to exploring MPRs, but the randomness of multiphase composites often necessitates extensive 3D microstructure datasets for statistical reliability. This study introduces a cost-effective machine… ▽ More Understanding microstructure-property relationships (MPRs) is essential for optimising the performance of multiphase composites. Image-based poro/micro-mechanical modelling provides a non-invasive approach to exploring MPRs, but the randomness of multiphase composites often necessitates extensive 3D microstructure datasets for statistical reliability. This study introduces a cost-effective machine learning framework to reconstruct numerous virtual 3D microstructures from limited 2D exemplars, circumventing the high costs of volumetric microscopy. Using feedforward neural networks, termed the statistics-encoded neural network (SENN), the framework encodes 2D morphological statistics and infers 3D morphological statistics via a 2D-to-3D integration scheme. Statistically equivalent 3D microstructures are synthesised using Gibbs sampling. Hierarchical characterisation enables seamless capture of features across multiple scales. Validation on three composites demonstrates strong statistical equivalence between reconstructed and reference microstructures, confirmed by morphological descriptors and simulated macroscopic properties (e.g., stiffness, permeability). The SENN-based framework is a high-fidelity tool for efficiently and accurately reconstructing multiphase microstructures. △ Less

Submitted 19 January, 2025; v1 submitted 13 January, 2025; originally announced January 2025.

Highly stable modular-assembled laser system for a dual-atom-interferometer gyroscope

Authors: Chuan Sun, Si-Bin Lu, Min Jiang, Zhan-Wei Yao, Shao-Kang Li, Xiao-Li Chen, Min Ke, Jia-Hao Fu, Run-Bing Li, Jin Wang, Ming-Sheng Zhan

Abstract: Operating atom-interferometer gyroscopes outside a laboratory environment is challenging primarily owing to the instability of laser systems. To enhance the thermal stability of free-space laser systems, a compact laser system using fiber lasers and all-quartz-jointed optical modules was developed for a dual-atom-interferometer gyroscope. Millimeter-scale optical elements jointed on quartz plates… ▽ More Operating atom-interferometer gyroscopes outside a laboratory environment is challenging primarily owing to the instability of laser systems. To enhance the thermal stability of free-space laser systems, a compact laser system using fiber lasers and all-quartz-jointed optical modules was developed for a dual-atom-interferometer gyroscope. Millimeter-scale optical elements jointed on quartz plates with identical quartz supports, ensure laser power stability and facilitate component upgrades. The primary diode laser was locked to the modulation transfer spectrum of Rb atoms, and Raman lasers were phase-locked to the primary laser. Frequencies for repumping, blow-away, and detection lasers were adjusted with acousto-optic modulators. At room temperature, laser power fluctuation was under 1:1000, polarization extinction ratio exceeded 30 dB, frequency fluctuation was below 91 kHz, and phase noise reached to -100 dBc/Hz @ 1 kHz. The optical modules were tested at 5--50 $^{\circ}$C and applied to a dual-atom-interferometer gyroscope. The fringe contrast was tested over the temperature range. The proposed system paves the way for promoting field applications of atom-interferometer sensors. △ Less

Submitted 18 November, 2024; originally announced November 2024.

Comments: 11 pages, 9 figures

Silicon modulator exceeding 110 GHz using tunable time-frequency equalization

Authors: Hengsong Yue, Jianbin Fu, Hengwei Zhang, Bo Xiong, Shilong Pan, Tao Chu

Abstract: Silicon modulators have garnered considerable attention owing to their potential applications in high-density integration and high-speed modulation. However, they are increasingly challenged by the limited 3 dB bandwidth as the demand for modulation speed in optical communications continues to rise, impeding their ability to compete with modulators made of thin-film lithium niobate. This bandwidth… ▽ More Silicon modulators have garnered considerable attention owing to their potential applications in high-density integration and high-speed modulation. However, they are increasingly challenged by the limited 3 dB bandwidth as the demand for modulation speed in optical communications continues to rise, impeding their ability to compete with modulators made of thin-film lithium niobate. This bandwidth limitation arises because of the parasitic resistance and capacitance in the PN junction of the silicon modulators. This study demonstrates the first silicon modulator exceeding 110 GHz without any resonant structure using a tunable time-frequency equalization technique. This substantial breakthrough enables on-off keying modulation at a rate of 140 Gbaud without digital signal processing. These accomplishments represent the highest bandwidth and maximum baud rate achieved without digital signal processing in an all-silicon modulator, reaching the testing limitations of the experimental system. This opens the possibility of attaining modulation rates of up to 200 or even 300 Gbaud by adopting design strategies such as slow light and technologies such as digital signal processing. This advancement extends the speed capabilities of silicon modulators to the level of thin-film lithium niobate modulators, thereby promoting their application in the broader array of fields, such as linear-drive pluggable transceivers. △ Less

Submitted 13 October, 2024; originally announced October 2024.

Cosmic ray susceptibility of the Terahertz Intensity Mapper detector arrays

Authors: Lun-Jun Liu, Reinier M. J. Janssen, Bruce Bumble, Elijah Kane, Logan M. Foote, Charles M. Bradford, Steven Hailey-Dunsheath, Shubh Agrawal, James E. Aguirre, Hrushi Athreya, Justin S. Bracks, Brockton S. Brendal, Anthony J. Corso, Jeffrey P. Filippini, Jianyang Fu, Christopher E. Groppi, Dylan Joralmon, Ryan P. Keenan, Mikolaj Kowalik, Ian N. Lowe, Alex Manduca, Daniel P. Marrone, Philip D. Mauskopf, Evan C. Mayer, Rong Nie , et al. (4 additional authors not shown)

Abstract: We report on the effects of cosmic ray interactions with the Kinetic Inductance Detector (KID) based focal plane array for the Terahertz Intensity Mapper (TIM). TIM is a NASA-funded balloon-borne experiment designed to probe the peak of the star formation in the Universe. It employs two spectroscopic bands, each equipped with a focal plane of four $\sim\,$900-pixel, KID-based array chips. Measurem… ▽ More We report on the effects of cosmic ray interactions with the Kinetic Inductance Detector (KID) based focal plane array for the Terahertz Intensity Mapper (TIM). TIM is a NASA-funded balloon-borne experiment designed to probe the peak of the star formation in the Universe. It employs two spectroscopic bands, each equipped with a focal plane of four $\sim\,$900-pixel, KID-based array chips. Measurements of an 864-pixel TIM array shows 791 resonators in a 0.5$\,$GHz bandwidth. We discuss challenges with resonator calibration caused by this high multiplexing density. We robustly identify the physical positions of 788 (99.6$\,$%) detectors using a custom LED-based identification scheme. Using this information we show that cosmic ray events occur at a rate of 2.1$\,\mathrm{events/min/cm^2}$ in our array. 66$\,$% of the events affect a single pixel, and another 33$\,$% affect $<\,$5 KIDs per event spread over a 0.66$\,\mathrm{cm^2}$ region (2 pixel pitches in radius). We observe a total cosmic ray dead fraction of 0.0011$\,$%, and predict that the maximum possible in-flight dead fraction is $\sim\,$0.165$\,$%, which demonstrates our design will be robust against these high-energy events. △ Less

Submitted 24 July, 2024; originally announced July 2024.

Comments: 14 pages, 5 figures. Accepted for the publication in Journal of Low Temperature Physics (2024)

Study of the decay and production properties of $D_{s1}(2536)$ and $D_{s2}^*(2573)$

Authors: M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann , et al. (645 additional authors not shown)

Abstract: The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ processes are studied using data samples collected with the BESIII detector at center-of-mass energies from 4.530 to 4.946~GeV. The absolute branching fractions of $D_{s1}(2536)^- \rightarrow \bar{D}^{*0}K^-$ and $D_{s2}^*(2573)^- \rightarrow \bar{D}^0K^-$ are measured for the first time to be… ▽ More The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ processes are studied using data samples collected with the BESIII detector at center-of-mass energies from 4.530 to 4.946~GeV. The absolute branching fractions of $D_{s1}(2536)^- \rightarrow \bar{D}^{*0}K^-$ and $D_{s2}^*(2573)^- \rightarrow \bar{D}^0K^-$ are measured for the first time to be $(35.9\pm 4.8\pm 3.5)\%$ and $(37.4\pm 3.1\pm 4.6)\%$, respectively. The measurements are in tension with predictions based on the assumption that the $D_{s1}(2536)$ and $D_{s2}^*(2573)$ are dominated by a bare $c\bar{s}$ component. The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ cross sections are measured, and a resonant structure at around 4.6~GeV with a width of 50~MeV is observed for the first time with a statistical significance of $15σ$ in the $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ process. It could be the $Y(4626)$ found by the Belle collaboration in the $D_s^+D_{s1}(2536)^{-}$ final state, since they have similar masses and widths. There is also evidence for a structure at around 4.75~GeV in both processes. △ Less

Submitted 10 July, 2024; originally announced July 2024.

Beam test of a baseline vertex detector prototype for CEPC

Authors: Shuqi Li, Tianya Wu, Xinhui Huang, Jia Zhou, Ziyue Yan, Wei Wang, Hao Zeng, Yiming Hu, Xiaoxu Zhang, Zhijun Liang, Wei Wei, Ying Zhang, Xiaomin Wei, Lei Zhang, Ming Qi, Jun Hu, Jinyu Fu, Hongyu Zhang, Gang Li, Linghui Wu, Mingyi Dong, Xiaoting Li, Raimon Casanova, Liang Zhang, Jianing Dong , et al. (5 additional authors not shown)

Abstract: The Circular Electron Positron Collider (CEPC) has been proposed to enable more thorough and precise measurements of the properties of Higgs, W, and Z bosons, as well as to search for new physics. In response to the stringent performance requirements of the vertex detector for the CEPC, a baseline vertex detector prototype was tested and characterized for the first time using a 6 GeV electron beam… ▽ More The Circular Electron Positron Collider (CEPC) has been proposed to enable more thorough and precise measurements of the properties of Higgs, W, and Z bosons, as well as to search for new physics. In response to the stringent performance requirements of the vertex detector for the CEPC, a baseline vertex detector prototype was tested and characterized for the first time using a 6 GeV electron beam at DESY II Test Beam Line 21. The baseline vertex detector prototype is designed with a cylindrical barrel structure that contains six double-sided detector modules (ladders). Each side of the ladder includes TaichuPix-3 sensors based on Monolithic Active Pixel Sensor (MAPS) technology, a flexible printed circuit, and a carbon fiber support structure. Additionally, the readout electronics and the Data Acquisition system were also examined during this beam test. The performance of the prototype was evaluated using an electron beam that passed through six ladders in a perpendicular direction. The offline data analysis indicates a spatial resolution of about 5 um, with detection efficiency exceeding 99 % and an impact parameter resolution of about 5.1 um. These promising results from this baseline vertex detector prototype mark a significant step toward realizing the optimal vertex detector for the CEPC. △ Less

Submitted 1 April, 2024; originally announced April 2024.

Stacking faults enabled second harmonic generation in centrosymmetric van der Waals RhI3

Authors: Yue Liu, Wen He, Bingze Wu, Fengyuan Xuan, Yuqiang Fang, Zhengbo Zhong, Jierui Fu, Jiapeng Wang, Zhipeng Li, Jinzhong Wang, Mingguang Yao, Fuqiang Huang, Liang Zhen, Yang Li, Chengyan Xu

Abstract: Second harmonic generation (SHG) in van der Waals (vdWs) materials has garnered significant attention due to its potential for integrated nonlinear optical and optoelectronic applications. Stacking faults in vdWs materials, a typical kind of planar defect, can introduce a new degree of freedom to modulate the crystal symmetry and resultant SHG response, however, the physical origin and tunability… ▽ More Second harmonic generation (SHG) in van der Waals (vdWs) materials has garnered significant attention due to its potential for integrated nonlinear optical and optoelectronic applications. Stacking faults in vdWs materials, a typical kind of planar defect, can introduce a new degree of freedom to modulate the crystal symmetry and resultant SHG response, however, the physical origin and tunability of stacking-fault-governed SHG in vdWs materials remain unclear. Here, taking the intrinsically centrosymmetric vdWs RhI3 as an example, we theoretically reveal the origin of stacking-fault-governed SHG response, where the SHG response comes from the energetically favorable AC- Cstacking fault of which the electrical transitions along the high symmetry paths Gamma-M and Gamma-K in the Brillion zone play the dominant role at 810 nm. Such stacking-fault-governed SHG response is further confirmed via structural characterizations and SHG measurements. Furthermore, by applying hydrostatic pressure on RhI3, the correlation between structural evolution and SHG response is revealed with SHG enhancement up to 6.9 times, where the decreased electronic transition energies and huger momentum matrix elements due to the stronger interlayer interactions upon compression magnify the SHG susceptibility. This study develops a promising foundation based on strategically designed stacking faults for pioneering new avenues in nonlinear nano-optics. △ Less

Submitted 29 February, 2024; originally announced February 2024.

Unveiling a crystal's entropy of disorder via electron diffraction. A statistical mechanics approach

Authors: Dongxin Liu, Oren Elishav, Jiarui Fu, Masaya Sakakibara, Kaoru Yamanouchi, Barak Hirshberg, Takayuki Nakamuro, Eiichi Nakamura

Abstract: Upon melting, the molecules in the crystal explore numerous configurations, reflecting an increase in disorder. The molar entropy of disorder can be defined by Bolzmann's formula dSd = Rln(Wd) where Wd is the increase in the number of microscopic states, so far inaccessible experimentally. We found that the Arrhenius frequency factor A of the electron diffraction signal decay provides Wd via an ex… ▽ More Upon melting, the molecules in the crystal explore numerous configurations, reflecting an increase in disorder. The molar entropy of disorder can be defined by Bolzmann's formula dSd = Rln(Wd) where Wd is the increase in the number of microscopic states, so far inaccessible experimentally. We found that the Arrhenius frequency factor A of the electron diffraction signal decay provides Wd via an experimental equation A = AINTWd where AINT is an inelastic scattering cross-section. The method connects Clausius and Boltzmann experimentally and supplements the Clausius approach, being applicable to a femtogram quantity of thermally unstable and biomolecular crystals. The data also showed that crystal disordering and crystallization of melt are reciprocal, both governed by the entropy change, but manifesting in opposite directions. △ Less

Submitted 8 February, 2024; v1 submitted 7 February, 2024; originally announced February 2024.

Comments: 18 pages, 5 figures, 1 table

Deep-learning density functional perturbation theory

Authors: He Li, Zechen Tang, Jingheng Fu, Wen-Han Dong, Nianlong Zou, Xiaoxun Gong, Wenhui Duan, Yong Xu

Abstract: Calculating perturbation response properties of materials from first principles provides a vital link between theory and experiment, but is bottlenecked by the high computational cost. Here a general framework is proposed to perform density functional perturbation theory (DFPT) calculations by neural networks, greatly improving the computational efficiency. Automatic differentiation is applied on… ▽ More Calculating perturbation response properties of materials from first principles provides a vital link between theory and experiment, but is bottlenecked by the high computational cost. Here a general framework is proposed to perform density functional perturbation theory (DFPT) calculations by neural networks, greatly improving the computational efficiency. Automatic differentiation is applied on neural networks, facilitating accurate computation of derivatives. High efficiency and good accuracy of the approach are demonstrated by studying electron-phonon coupling and related physical quantities. This work brings deep-learning density functional theory and DFPT into a unified framework, creating opportunities for developing ab initio artificial intelligence. △ Less

Submitted 31 January, 2024; originally announced January 2024.

Journal ref: Phys. Rev. Lett. 132, 096401 (2024)

Beam test of a 180 nm CMOS Pixel Sensor for the CEPC vertex detector

Authors: Tianya Wu, Shuqi Li, Wei Wang, Jia Zhou, Ziyue Yan, Yiming Hu, Xiaoxu Zhang, Zhijun Liang, Wei Wei, Ying Zhang, Xiaomin Wei, Xinhui Huang, Lei Zhang, Ming Qi, Hao Zeng, Xuewei Jia, Jun Hu, Jinyu Fu, Hongyu Zhang, Gang Li, Linghui Wu, Mingyi Dong, Xiaoting Li, Raimon Casanova, Liang Zhang , et al. (6 additional authors not shown)

Abstract: The proposed Circular Electron Positron Collider (CEPC) imposes new challenges for the vertex detector in terms of pixel size and material budget. A Monolithic Active Pixel Sensor (MAPS) prototype called TaichuPix, based on a column drain readout architecture, has been developed to address the need for high spatial resolution. In order to evaluate the performance of the TaichuPix-3 chips, a beam t… ▽ More The proposed Circular Electron Positron Collider (CEPC) imposes new challenges for the vertex detector in terms of pixel size and material budget. A Monolithic Active Pixel Sensor (MAPS) prototype called TaichuPix, based on a column drain readout architecture, has been developed to address the need for high spatial resolution. In order to evaluate the performance of the TaichuPix-3 chips, a beam test was carried out at DESY II TB21 in December 2022. Meanwhile, the Data Acquisition (DAQ) for a muti-plane configuration was tested during the beam test. This work presents the characterization of the TaichuPix-3 chips with two different processes, including cluster size, spatial resolution, and detection efficiency. The analysis results indicate the spatial resolution better than 5 $μm$ and the detection efficiency exceeds 99.5 % for both TaichuPix-3 chips with the two different processes. △ Less

Submitted 10 November, 2023; originally announced November 2023.

Nanoscale Analysis of Frozen Water by Atom Probe Tomography Using Graphene Encapsulation and Cryo-Workflows: A Parametric Study

Authors: Florant Exertier, Levi Tegg, Adam Taylor, Julie M. Cairney, Jing Fu, Ross K. W. Marceau

Abstract: There has been an increasing interest in atom probe tomography (APT) to characterise hydrated and biological materials. A major benefit of APT compared to microscopy techniques more commonly used in biology is its combination of outstanding 3D spatial resolution (~0.2 nm) and mass sensitivity. APT has already been successfully used to characterise biological materials, revealing key structural inf… ▽ More There has been an increasing interest in atom probe tomography (APT) to characterise hydrated and biological materials. A major benefit of APT compared to microscopy techniques more commonly used in biology is its combination of outstanding 3D spatial resolution (~0.2 nm) and mass sensitivity. APT has already been successfully used to characterise biological materials, revealing key structural information at the atomic scale, however there are many challenges inherent to the analysis of hydrated materials. New preparation protocols, often involving sample preparation and transfer at cryogenic temperature, enable APT analysis of hydrated materials and have the potential to enable 3D atomic scale characterisation of biological materials in the near-native hydrated state. In this study, APT specimens of pure water at the tips of tungsten needles were prepared at room temperature by graphene encapsulation. A parametric study was conducted where samples were transferred at either room temperature or cryo-temperature and analysed by APT by varying parameters such as the flight path and pulsing mode. The differences between the acquisition scenarios are presented along with recommendations for future studies. △ Less

Submitted 10 November, 2023; originally announced November 2023.

Complexity of Government response to Covid-19 pandemic: A perspective of coupled dynamics on information heterogeneity and epidemic outbreak

Authors: Xiaoqi Zhang, Jie Fu, Sheng Hua, Han Liang, Zi-Ke Zhang

Abstract: This study aims at modeling the universal failure in preventing the outbreak of COVID-19 via real-world data from the perspective of complexity and network science. Through formalizing information heterogeneity and government intervention in the coupled dynamics of epidemic and infodemic spreading; first, we find that information heterogeneity and its induced variation in human responses significa… ▽ More This study aims at modeling the universal failure in preventing the outbreak of COVID-19 via real-world data from the perspective of complexity and network science. Through formalizing information heterogeneity and government intervention in the coupled dynamics of epidemic and infodemic spreading; first, we find that information heterogeneity and its induced variation in human responses significantly increase the complexity of the government intervention decision. The complexity results in a dilemma between the socially optimal intervention that is risky for the government and the privately optimal intervention that is safer for the government but harmful to the social welfare. Second, via counterfactual analysis against the COVID-19 crisis in Wuhan, 2020, we find that the intervention dilemma becomes even worse if the initial decision time and the decision horizon vary. In the short horizon, both socially and privately optimal interventions agree with each other and require blocking the spread of all COVID-19-related information, leading to a negligible infection ratio 30 days after the initial reporting time. However, if the time horizon is prolonged to 180 days, only the privately optimal intervention requires information blocking, which would induce a catastrophically higher infection ratio than that in the counter-factual world where the socially optimal intervention encourages early-stage information spread. These findings contribute to the literature by revealing the complexity incurred by the coupled infodemic-epidemic dynamics and information heterogeneity to the governmental intervention decision, which also sheds insight into the design of an effective early warning system against the epidemic crisis in the future. △ Less

Submitted 24 October, 2023; originally announced October 2023.

Comments: This version contains the full-resolution figures for the paper DOI: 10.1007/s11071-023-08427-5

Crystal Facet Effect in Plasmonic Catalysis

Authors: Yicui Kang, Simão M. João, Rui Lin, Li Zhu, Junwei Fu, Weng-Chon, Cheong, Seunghoon Lee, Kilian Frank, Bert Nickel, Min Liu, Johannes Lischner, Emiliano Cortés

Abstract: In the realm of plasmonic catalytic systems, much attention has been devoted to the plasmon-derived mechanisms, yet the influence of nanoparticles' crystal facets in this type of processes has been sparsely investigated. In this work, we study the plasmon-assisted electrocatalytic CO2 reduction reaction using three different shapes of plasmonic Au nanoparticles - nanocube (NC), rhombic dodecahedro… ▽ More In the realm of plasmonic catalytic systems, much attention has been devoted to the plasmon-derived mechanisms, yet the influence of nanoparticles' crystal facets in this type of processes has been sparsely investigated. In this work, we study the plasmon-assisted electrocatalytic CO2 reduction reaction using three different shapes of plasmonic Au nanoparticles - nanocube (NC), rhombic dodecahedron (RD) and octahedron (OC) - with three different exposed facets: {100}, {110} and {111}, respectively. These particles were synthesized with similar sizes and LSPR wavelengths to reveal the role of the facet more than other contributions to the plasmon-assisted reaction. Upon plasmon excitation, Au OCs exhibited nearly a doubling in the Faradaic efficiency of CO (FE(CO)) and a remarkable threefold enhancement in the partial current density of CO (j(CO)) compared to the non-illuminated response, NCs also demonstrated an improved performance under illumination. In contrast, Au RDs showed nearly the same performance in dark or light conditions. Temperature-dependent experiments ruled out heat as the main factor in the enhanced response of Au OCs and NCs. Large-scale atomistic simulations of the nanoparticles' electronic structure and electromagnetic modeling revealed higher hot carrier abundance and electric field enhancement on Au OCs and NCs compared to RDs. Abundant hot carriers on edges facilitate molecular activation, leading to enhanced selectivity and activity. Thus, OCs with the highest edge/facet ratio exhibited the strongest enhancement in FE(CO) and j(CO) upon illumination. This observation is further supported by plasmon-assisted H2 evolution reaction experiments. Our findings highlight the dominance of low coordinated sites over facets in plasmonic catalytic processes, providing valuable insights for designing more efficient catalysts for solar fuels production. △ Less

Submitted 23 October, 2023; originally announced October 2023.

Experts' cognition-driven ensemble deep learning for external validation of predicting pathological complete response to neoadjuvant chemotherapy from histological images in breast cancer

Authors: Yongquan Yang, Fengling Li, Yani Wei, Yuanyuan Zhao, Jing Fu, Xiuli Xiao, Hong Bu

Abstract: In breast cancer, neoadjuvant chemotherapy (NAC) provides a standard treatment option for patients who have locally advanced cancer and some large operable tumors. A patient will have better prognosis when he has achieved a pathological complete response (pCR) with the treatment of NAC. There has been a trend to directly predict pCR to NAC from histological images based on deep learning (DL). Howe… ▽ More In breast cancer, neoadjuvant chemotherapy (NAC) provides a standard treatment option for patients who have locally advanced cancer and some large operable tumors. A patient will have better prognosis when he has achieved a pathological complete response (pCR) with the treatment of NAC. There has been a trend to directly predict pCR to NAC from histological images based on deep learning (DL). However, the DL-based predictive models numerically have better performances in internal validation than in external validation. In this paper, we aim to alleviate this situation with an intrinsic approach. We propose an experts' cognition-driven ensemble deep learning (ECDEDL) approach. Taking the cognition of both pathology and artificial intelligence experts into consideration to improve the generalization of the predictive model to the external validation, ECDEDL can intrinsically approximate the working paradigm of a human being which will refer to his various working experiences to make decisions. ECDEDL was validated with 695 WSIs collected from the same center as the primary dataset to develop the predictive model and perform the internal validation, and was also validated with 340 WSIs collected from other three centers as the external dataset to perform the external validation. In external validation, ECDEDL improves the AUCs of pCR prediction from 61.52(59.80-63.26) to 67.75(66.74-68.80) and the Accuracies of pCR prediction from 56.09(49.39-62.79) to 71.01(69.44-72.58). ECDEDL was quite effective for external validation of predicting pCR to NAC from histological images in breast cancer, numerically approximating the internal validation. △ Less

Submitted 11 November, 2024; v1 submitted 19 June, 2023; originally announced June 2023.

Comments: This is the final published version

The LHCb upgrade I

Authors: LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, C. Achard, T. Ackernley, B. Adeva, M. Adinolfi, P. Adlarson, H. Afsharnia, C. Agapopoulou, C. A. Aidala, Z. Ajaltouni, S. Akar, K. Akiba, P. Albicocco, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, Z. Aliouche, P. Alvarez Cartelle, R. Amalric, S. Amato , et al. (1298 additional authors not shown)

Abstract: The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their select… ▽ More The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software. △ Less

Submitted 10 September, 2024; v1 submitted 17 May, 2023; originally announced May 2023.

Comments: All figures and tables, along with any supplementary material and additional information, are available at http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-DP-2022-002.html (LHCb public pages)

Report number: LHCb-DP-2022-002

Journal ref: JINST 19 (2024) P05065

STCF Conceptual Design Report: Volume 1 -- Physics & Detector

Authors: M. Achasov, X. C. Ai, R. Aliberti, L. P. An, Q. An, X. Z. Bai, Y. Bai, O. Bakina, A. Barnyakov, V. Blinov, V. Bobrovnikov, D. Bodrov, A. Bogomyagkov, A. Bondar, I. Boyko, Z. H. Bu, F. M. Cai, H. Cai, J. J. Cao, Q. H. Cao, Z. Cao, Q. Chang, K. T. Chao, D. Y. Chen, H. Chen , et al. (413 additional authors not shown)

Abstract: The Super $τ$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $τ$-Charm factory -- the BEPCII,… ▽ More The Super $τ$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $τ$-Charm factory -- the BEPCII, providing a unique platform for exploring the asymmetry of matter-antimatter (charge-parity violation), in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions, as well as searching for exotic hadrons and physics beyond the Standard Model. The STCF project in China is under development with an extensive R\&D program. This document presents the physics opportunities at the STCF, describes conceptual designs of the STCF detector system, and discusses future plans for detector R\&D and physics case studies. △ Less

Submitted 5 October, 2023; v1 submitted 28 March, 2023; originally announced March 2023.

Journal ref: Front. Phys. 19(1), 14701 (2024)

Design of The Kinetic Inductance Detector Based Focal Plane Assembly for The Terahertz Intensity Mapper

Authors: L. -J. Liu, R. M. J. Janssen, C. M. Bradford, S. Hailey-Dunsheath, J. Fu, J. P. Filippini, J. E. Aguirre, J. S. Bracks, A. J. Corso, C. Groppi, J. Hoh, R. P. Keenan, I. N. Lowe, D. P. Marrone, P. Mauskopf, R. Nie, J. Redford, I. Trumper, J. D. Vieira

Abstract: We report on the kinetic inductance detector (KID) array focal plane assembly design for the Terahertz Intensity Mapper (TIM). Each of the 2 arrays consists of 4 wafer-sized dies (quadrants), and the overall assembly must satisfy thermal and mechanical requirements, while maintaining high optical efficiency and a suitable electromagnetic environment for the KIDs. In particular, our design manages… ▽ More We report on the kinetic inductance detector (KID) array focal plane assembly design for the Terahertz Intensity Mapper (TIM). Each of the 2 arrays consists of 4 wafer-sized dies (quadrants), and the overall assembly must satisfy thermal and mechanical requirements, while maintaining high optical efficiency and a suitable electromagnetic environment for the KIDs. In particular, our design manages to strictly maintain a 50 $\mathrm{μm}$ air gap between the array and the horn block. We have prototyped and are now testing a sub-scale assembly which houses a single quadrant for characterization before integration into the full array. The initial test result shows a $>$95% yield, indicating a good performance of our TIM detector packaging design. △ Less

Submitted 24 July, 2024; v1 submitted 17 November, 2022; originally announced November 2022.

Comments: 8 pages, 6 figures, accepted for publication in Journal of Low Temperature Physics (2022)

Design and testing of Kinetic Inductance Detector package for the Terahertz Intensity Mapper

Authors: L. -J. Liu, R. M. J Janssen, C. M. Bradford, S. Hailey-Dunsheath, J. P. Filippini, J. E. Aguirre, J. S. Bracks, A. J. Corso, J. Fu, C. Groppi, J. Hoh, R. P. Keenan, I. N. Lowe, D. P. Marrone, P. Mauskopf, R. Nie, J. Redford, I. Trumper, J. D. Vieira

Abstract: The Terahertz Intensity Mapper (TIM) is designed to probe the star formation history in dust-obscured star-forming galaxies around the peak of cosmic star formation. This will be done via measurements of the redshifted 157.7 um line of singly ionized carbon ([CII]). TIM employs two R $\sim 250$ long-slit grating spectrometers covering 240-420 um. Each is equipped with a focal plane unit containing… ▽ More The Terahertz Intensity Mapper (TIM) is designed to probe the star formation history in dust-obscured star-forming galaxies around the peak of cosmic star formation. This will be done via measurements of the redshifted 157.7 um line of singly ionized carbon ([CII]). TIM employs two R $\sim 250$ long-slit grating spectrometers covering 240-420 um. Each is equipped with a focal plane unit containing 4 wafer-sized subarrays of horn-coupled aluminum kinetic inductance detectors (KIDs). We present the design and performance of a prototype focal plane assembly for one of TIM's KID-based subarrays. Our design strictly maintain high optical efficiency and a suitable electromagnetic environment for the KIDs. The prototype detector housing in combination with the first flight-like quadrant are tested at 250 mK. Initial frequency scan shows that many resonances are affected by collisions and/or very shallow transmission dips as a result of a degraded internal quality factor (Q factor). This is attributed to the presence of an external magnetic field during cooldown. We report on a study of magnetic field dependence of the Q factor of our quadrant array. We implement a Helmholtz coil to vary the magnetic field at the detectors by (partially) nulling earth's. Our investigation shows that the earth magnetic field can significantly affect our KIDs' performance by degrading the Q factor by a factor of 2-5, well below those expected from the operational temperature or optical loading. We find that we can sufficiently recover our detectors' quality factor by tuning the current in the coils to generate a field that matches earth's magnetic field in magnitude to within a few uT. Therefore, it is necessary to employ a properly designed magnetic shield enclosing the TIM focal plane unit. Based on the results presented in this paper, we set a shielding requirement of |B| < 3 uT. △ Less

Submitted 24 July, 2024; v1 submitted 16 November, 2022; originally announced November 2022.

Comments: This conference proceeding reports on a study of magnetic field dependence of the quality factor of Terahertz Intensity Mapper's 864-pixel Kinetic Inductance Detector array and an effort on carrying out the magnetic shielding requirement for TIM's balloon flight and science operation. 8 pages, 5 figures, accepted for publication in conference proceedings of SPIE

Journal ref: Proceedings of the SPIE, Volume 12190 (2022)

Patient-specific mean teacher UNet for enhancing PET image and low-dose PET reconstruction on RefleXion X1 biology-guided radiotherapy system

Authors: Jie Fu, Zhicheng Zhang, Linxi Shi, Zhiqiang Hu, Thomas Laurence, Eric Nguyen, Peng Dong, Guillem Pratx, Lucas Vitzthum, Daniel T. Chang, Lei Xing, Wu Liu

Abstract: The RefleXion X1 is the first biology-guided radiotherapy (BgRT) system. Its dual 90-degree PET detector collects fewer pair production events compared to a full-ring diagnostic PET system. In the proposed BgRT workflow, a short scan is acquired before treatment delivery to ensure image quality and consistency. The shorter scan time, a quarter of the simulation scan time, also leads to fewer coinc… ▽ More The RefleXion X1 is the first biology-guided radiotherapy (BgRT) system. Its dual 90-degree PET detector collects fewer pair production events compared to a full-ring diagnostic PET system. In the proposed BgRT workflow, a short scan is acquired before treatment delivery to ensure image quality and consistency. The shorter scan time, a quarter of the simulation scan time, also leads to fewer coincidence events and hence reduced image quality. In this study, we proposed a patient-specific mean teacher UNet (MT-UNet) to enhance PET image quality and low-dose PET reconstruction on RefleXion X1. PET/CT scans of nine cancer patients were acquired using RefleXion X1. Every patient had one simulation scan. Five patients had additional scans acquired during the first and the final treatment fractions. Treatment scans were acquired using the same imaging protocol as the simulation scan. For each scan, we reconstructed a full-dose image and evenly split coincidence events into four sessions to reconstruct four quarter-dose PET images. For each patient, our proposed MT-UNet was trained using quarter-dose and full-dose images of the simulation scan. For the image quality enhancement task, we applied nine trained MT-UNets to full-dose simulation PET images of the nine patients to generate enhanced images, respectively. The enhanced images were compared with the original full-dose images using CNR and SNR. For the low-dose image reconstruction task, we applied five trained MT-UNets to ten quarter-dose treatment images of five patients to predict full-dose images, respectively. The predicted and ground truth full-dose images were compared using SSIM and PSNR. We also trained and evaluated patient-specific UNets for model comparison. Our proposed patient-specific MT-UNet achieved better performance in improving the quality of RefleXion low-dose and full-dose images compared to the patient-specific UNet. △ Less

Submitted 12 September, 2022; originally announced September 2022.

A LN2-based cryogenic system prototype for future PandaX experiment

Authors: Xinbei Jiang, Li Zhao, Shaobo Wang, Jia Fu, Tianjie Wu, Jianglai Liu

Abstract: This paper describes results on R&D of an economical and efficient cryogenic system prototype for future liquid xenon detector. The test module of the prototype has a "cold head" attached to a copper rod, which is specially designed to transport heat loads to a free-boiling liquid nitrogen bath. The performance of the test module and commercial refrigerators is compared. The module with an optimiz… ▽ More This paper describes results on R&D of an economical and efficient cryogenic system prototype for future liquid xenon detector. The test module of the prototype has a "cold head" attached to a copper rod, which is specially designed to transport heat loads to a free-boiling liquid nitrogen bath. The performance of the test module and commercial refrigerators is compared. The module with an optimized copper rod has demonstrated more than 1500W cooling power at 178K.The temperature of the "cold head" can be kept stable with an error of 0.02K, its fluctuation is within 0.1K. △ Less

Submitted 8 June, 2022; v1 submitted 1 June, 2022; originally announced June 2022.

Comments: 11 pages, 6 figures

Substrate-mediated Borophane Polymorphs through Hydrogenation of Two-dimensional Boron Sheets

Authors: Yuchong Kang, Xiaoyun Ma, Jing Fu, Kun Yang, Zongguo Wang, Haibo Li, Wei Ma, Jin Zhang

Abstract: Two-dimensional boron monolayer (borophene) stands out from the two-dimensional atomic layered materials due to its structural flexibility, tunable electronic and mechanical properties from a large number of allotropic materials. The stability of pristine borophene polymorphs could possibly be improved via hydrogenation with atomic hydrogen (referred to as borophane). However, the precise adsorpti… ▽ More Two-dimensional boron monolayer (borophene) stands out from the two-dimensional atomic layered materials due to its structural flexibility, tunable electronic and mechanical properties from a large number of allotropic materials. The stability of pristine borophene polymorphs could possibly be improved via hydrogenation with atomic hydrogen (referred to as borophane). However, the precise adsorption structures and the underlying mechanism are still elusive. Employing first-principles calculations, we demonstrate the optimal configurations of freestanding borophanes and the ones grown on metallic substrates. For freestanding β12 and χ3 borophenes, the energetically favored hydrogen adsorption sites are on the top of the boron atoms with CN=4 (CN: coordination number), while the best absorption sites for α' borophene are on the top of the boron atoms with CN=6. With various metal substrates, the hydrogenation configurations of borophene are modulated significantly, attributed to the chemical hybridization strength between B pz and H s orbitals. These findings provide a deep insight into the hydrogenating borophenes and facilitate the stabilization of two-dimensional boron polymorphs by engineering hydrogen adsorption sites and concentrations. △ Less

Submitted 30 May, 2022; originally announced May 2022.

First Identification of New X-Ray Spectra of Mo39+, Mo40+, W43+, W44+ and W45+ on EAST

Authors: Fudi Wang, Dian Lu, Mingfeng Gu, Yifei Jin, Jia Fu, Yuejiang Shi, Yang Yang, J. E. Rice, Manfred Bitter, Qing Zang, Hailin Zhao, Liang He, Miaohui Li, Handong Xu, Haijing Liu, Zichao Lin, Yifei Chen, Yongcai Shen, Kenneth Hill, Cheonho Bae, Shengyu Fu, Hongming Zhang, Sanggon Lee, Xiaoqing Yang, Guozhang Jia , et al. (5 additional authors not shown)

Abstract: New high-resolution x-ray spectra of Mo39+, Mo40+, W43+, W44+ and W45+ have been carefully confirmed for the first time by use of the x-ray imaging crystal spectrometer (XCS) in Experimental Advanced Superconducting Tokamak (EAST) under various combined auxiliary heating plasmas conditions. Wavelength of these new x-ray spectra is ranged from 3.895 Å to 3.986 Å. When core electron temperature (Te0… ▽ More New high-resolution x-ray spectra of Mo39+, Mo40+, W43+, W44+ and W45+ have been carefully confirmed for the first time by use of the x-ray imaging crystal spectrometer (XCS) in Experimental Advanced Superconducting Tokamak (EAST) under various combined auxiliary heating plasmas conditions. Wavelength of these new x-ray spectra is ranged from 3.895 Å to 3.986 Å. When core electron temperature (Te0) reaches 6.0 keV, Mo39+ and Mo40+ lines of 3.9727, 3.9294 and 3.9480 Å can be effectively detected on XCS for EAST; meanwhile, line-integrated brightness of these spectral lines of Mo39+ and Mo40+ is very considerable when electron temperature reaches 12.9 keV. Multi-components spectral lines for W43+, W44+ and W45+ have also been identified when Te0 reaches 6 keV. Parts of spectral lines, such as Zn-1, Cu-2, Cu-4a, Cu-4d and Cu-5 lines of tungsten, are first observed experimentally. When electron temperature reaches 12.9 keV, line-integrated intensity for part of these spectral lines of W43+, W44+ and W45+ are considerable. These experimental results and theoretical predictions from FAC and FLYCHK codes are in good general agreement. These new spectral lines, obtained on XCS for EAST, are vital for deeply uncovering the mechanisms of ion and electron thermal, high-Z impurity and momentum (anomalous) transport to achieve the advanced steady-state operation scenarios for ITER and CFETR. △ Less

Submitted 5 April, 2022; originally announced April 2022.

Quantitative exploration of the absorber behavior of metal-insulator-metal metamaterials within terahertz via an asymmetric peak model

Authors: Zhigang Li Wenjing Jiang, Jianyu Fu, Qing Zhao

Abstract: Terahertz (THz) metamaterials have been developed for THz sensing, detection, imaging, and many other functions due to their unusual absorbers. However, the unusual absorption spectra change with different incident angles. Thus, we designed and fabricated a focal plane array with metal-insulator-metal (MIM) structure metamaterial absorbers for further research. The absorption spectrum with inciden… ▽ More Terahertz (THz) metamaterials have been developed for THz sensing, detection, imaging, and many other functions due to their unusual absorbers. However, the unusual absorption spectra change with different incident angles. Thus, we designed and fabricated a focal plane array with metal-insulator-metal (MIM) structure metamaterial absorbers for further research. The absorption spectrum with incident angles from 20 to 60 was measured using THz time-domain spectroscopy (THz-TDS), and the experimental results reveal that the absorption spectrum changes with incident angle variations. A basic analytical asymmetric peak model for extracting absorption-frequency characteristics was developed in this study to quantitatively explore this variation in the absorber behavior with incident angles. The best result was that the frequency corresponding to the highest absorption can be easily found using this peak model. The experimental data was coherent with the validation of the asymmetric peak model. Moreover, a second model to quantitatively relate parameters to the incident angle was discovered, allowing for the prediction of absorption spectrum shifts and changes. The absorption spectrum was predicted to have a valley-like absorption curve at particular incident angles based on the secondary models deduction. The proposed extraction method's essential feature is that it can be applied to any physics-based MIM metamaterial system. Such a model will guide the design and optimization of THz metamaterial absorbers, sensors, imagers, and many others. △ Less

Submitted 25 February, 2022; originally announced February 2022.

Paired Ru-O-Mo ensemble for efficient and stable alkaline hydrogen evolution reaction

Authors: HuangJingWei Li, Kang Liu, Junwei Fu, Kejun Chen, Kexin Yang, Yiyang Lin, Baopeng Yang, Qiyou Wang, Hao Pan, Zhoujun Cai, Hongmei Li, Maoqi Cao, Junhua Hu, Ying-Rui Lu, Ting-Shan Chan, Emiliano Cortés, Andrea Fratalocchi, Min Liu

Abstract: Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is a promising electrochemical energy conversion strategy. Ruthenium (Ru) is an efficient catalyst with a desirable cost for HER, however, the sluggish H2O dissociation process, due to the low H2O adsorption on its surface, currently hampers the performances of this catalyst in alkaline HER. Herein, we demonstrate that the H2O ad… ▽ More Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is a promising electrochemical energy conversion strategy. Ruthenium (Ru) is an efficient catalyst with a desirable cost for HER, however, the sluggish H2O dissociation process, due to the low H2O adsorption on its surface, currently hampers the performances of this catalyst in alkaline HER. Herein, we demonstrate that the H2O adsorption improves significantly by the construction of Ru-O-Mo sites. We prepared Ru/MoO2 catalysts with Ru-O-Mo sites through a facile thermal treatment process and assessed the creation of Ru-O-Mo interfaces by transmission electron microscope (TEM) and extended X-ray absorption fine structure (EXAFS). By using Fourier-transform infrared spectroscopy (FTIR) and H2O adsorption tests, we proved Ru-O-Mo sites have tenfold stronger H2O adsorption ability than that of Ru catalyst. The catalysts with Ru-O-Mo sites exhibited a state-of-the-art overpotential of 16 mV at 10 mA cm-2 in 1 M KOH electrolyte, demonstrating a threefold reduction than the previous bests of Ru (59 mV) and commercial Pt (31 mV) catalysts. We proved the stability of these performances over 40 hours without decline. These results could open a new path for designing efficient and stable catalysts. △ Less

Submitted 25 August, 2021; originally announced August 2021.

Journal ref: Nano Energy 82 (2021) 105767

Tuning the intermediate reaction barriers by CuPd catalyst to improve the selectivity of electroreduction CO2 to C2 products

Authors: Li Zhu, Yiyang Lin, Kang Liu, Emiliano Cortés, Hongmei Li, Junhua Hu, Akira Yamaguchi, Ying-Rui Lu, Ting-Shan Chan, Xiaoliang Liu, Masahiro Miyauchi, Junwei Fu, Min Liu

Abstract: Electrochemical CO2 reduction is a promising strategy for utilization of CO2 and intermittent excess electricity. Cu is the only single-metal catalyst that can electrochemically convert CO2 to multi-carbon products. However, Cu has an undesirable selectivity and activity for C2 products, due to its insufficient amount of CO* for C-C coupling. Considering the strong CO2 adsorption and ultra-fast re… ▽ More Electrochemical CO2 reduction is a promising strategy for utilization of CO2 and intermittent excess electricity. Cu is the only single-metal catalyst that can electrochemically convert CO2 to multi-carbon products. However, Cu has an undesirable selectivity and activity for C2 products, due to its insufficient amount of CO* for C-C coupling. Considering the strong CO2 adsorption and ultra-fast reaction kinetics of CO* formation on Pd, an intimate CuPd(100) interface was designed to lower the intermediate reaction barriers and then improve the efficiency of C2 products. Density functional theory (DFT) calculations showed that the CuPd(100) interface has enhanced CO2 adsorption and decreased CO2* hydrogenation energy barrier, which are beneficial for C-C coupling. The potential-determining step (PDS) barrier of CO2 to C2 products on CuPd(100) interface is 0.61 eV, which is lower than that on Cu(100) (0.72 eV). Motivated by the DFT calculation, the CuPd(100) interface catalyst was prepared by a facile chemical solution method and demonstrated by transmission electron microscope (TEM). The CO2 temperature programmed desorption (CO2-TPD) and gas sensor experiments proved the enhancements of CO2 adsorption and CO2* hydrogenation abilities on CuPd(100) interface catalyst. As a result, the obtained CuPd(100) interface catalyst exhibits a C2 Faradaic efficiency of 50.3 (+/-) 1.2% at -1.4 VRHE in 0.1 M KHCO3, which is 2.1 times higher than 23.6(+/-) 1.5% of Cu catalyst. This work provides a rational design of Cu-based electrocatalyst for multi-carbon products by fine-tuning the intermediate reaction barriers. △ Less

Submitted 25 August, 2021; originally announced August 2021.

Journal ref: Chinese Journal of Catalysis 42 (2021) 1500-1508

Electrically switchable metasurface for beam steering using PEDOT

Authors: Juliane Ratzsch, Julian Karst, Jinglin Fu, Monika Ubl, Tobias Pohl, Florian Sterl, Claudia Malacrida, Matthias Wieland, Bernhard Reineke, Thomas Zentgraf, Sabine Ludwigs, Mario Hentschel, Harald Giessen

Abstract: Switchable and active metasurfaces allow for the realization of beam steering, zoomable metalenses, or dynamic holography. To achieve this goal, one has to combine high-performance metasurfaces with switchable materials that exhibit high refractive index contrast and high switching speeds. In this work, we present an electrochemically switchable metasurface for beam steering where we use the condu… ▽ More Switchable and active metasurfaces allow for the realization of beam steering, zoomable metalenses, or dynamic holography. To achieve this goal, one has to combine high-performance metasurfaces with switchable materials that exhibit high refractive index contrast and high switching speeds. In this work, we present an electrochemically switchable metasurface for beam steering where we use the conducting polymer poly(3,4-ethylene-dioxythiophene) (PEDOT) as an active material. We show beam diffraction with angles up to 10° and change of the intensities of the diffracted and primary beams employing an externally applied cyclic voltage between -1 V and +0.5 V. With this unique combination, we realize switching speeds in the range of 1 Hz while the extension to typical display frequencies in the tens of Hz region is possible. Our findings have immediate implications on the design and fabrication of future electronically switchable and display nanotechnologies, such as dynamic holograms. △ Less

Submitted 3 March, 2021; originally announced March 2021.

Journal ref: J. Opt. 22, 124001 (2020)

Photoionization-induced broadband dispersive wave generated in an Ar-filled hollow-core photonic crystal fiber

Authors: Jianhua Fu, Yifei Chen, Zhiyuan Huang, Fei Yu, Dakun Wu, Jinyu Pan, Cheng Zhang, Ding Wang, Meng Pang, Yuxin Leng

Abstract: The resonance band in hollow-core photonic crystal fiber (HC-PCF), while leading to high-loss region in the fiber transmission spectrum, has been successfully used for generating phase-matched dispersive wave (DW). Here, we report that the spectral width of the resonance-induced DW can be largely broadened due to plasma-driven blueshifting soliton. In the experiment, we observed that in a short le… ▽ More The resonance band in hollow-core photonic crystal fiber (HC-PCF), while leading to high-loss region in the fiber transmission spectrum, has been successfully used for generating phase-matched dispersive wave (DW). Here, we report that the spectral width of the resonance-induced DW can be largely broadened due to plasma-driven blueshifting soliton. In the experiment, we observed that in a short length of Ar-filled single-ring HC-PCF the soliton self-compression and photoionization effects caused a strong spectral blueshift of the pump pulse, changing the phase-matching condition of the DW emission process. Therefore, broadening of DW spectrum to the longer-wavelength side was obtained with several spectral peaks, which correspond to the generation of DW at different positions along the fiber. In the simulation, we used super-Gauss windows with different central wavelengths to filter out these DW spectral peaks, and studied the time-domain characteristics of these peaks respectively using Fourier transform method. The simulation results verified that these multiple-peaks on the DW spectrum have different delays in the time domain, agreeing well with our theoretical prediction. Remarkably, we found that the whole time-domain DW trace can be compressed to ~29 fs using proper chirp compensation. The experimental and numerical results reported here provide some insight into the resonance-induced DW generation process in gas-filled HC-PCFs, they could also pave the way to ultrafast pulse generation using DW-emission mechanism. △ Less

Submitted 5 January, 2021; originally announced January 2021.