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Observation of topological charge transformations in acoustic vortex using passive periodic systems

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 140-147页

作者： Di-Chao Chen Xie Liu Changqing Xu Da-Jian Wu Ying Cheng Xiao-Jun Liu School of physics and Technology Nanjing Normal University Key laboratory of Modern Acoustics School of Physics Nanjing University

Vortex transmutation utilizes a periodic system, which not only enables the alteration of the topological charge(TC) of unstable input vortices but also facilitates their transformation into stable structures. This approach is crucial for investigating the characteristics of vortices in various wave systems. Here, we achieve acoustic vortex TC transmutation by employing a welldesigned dual-structured plate external system(DPES). The interactions between the acoustic vortex and the finite-order discrete rotational symmetry lead to the transformation of its topological charge when complete rotational symmetry is broken to Nthorder discrete symmetry. Our results experimentally demonstrate the acoustic vortex TC transmutation based on passive artificial structures, enabling numerous applications in particle manipulation and information multiplexing as well as advancing our understanding and control over free-space acoustic vortices.

关键词： acoustic vortex topological charge transformation artificial structure

Unveiling the superior hydrogen evolution reaction activity of 1T-2H MoS_(2)heterointerface by on-chip microdevices

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Nano Research 2025年第1期18卷 149-156页

作者： Bowen Liu Junjie Xiong Shuaishuai Xu Xinying Luo Wenyan Yao Shigang Liu Yuting Du Qinghua Zhang Yang Gao Bin Wang CAS Key laboratory of Nanosystem and Hierarchical Fabrication National Center for Nanoscience and Technology(NCNST)Beijing 100190China University of Chinese Academy of Sciences Beijing 100049China School of Materials Science and Engineering China University of Petroleum(East China)Qingdao 266580China Beijing national laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

The identification and clarification of active sites of MoS_(2)have long been the focus of research efforts in hydrogen evolution reaction(HER).In this study,we constructed phase transition-induced 1T-2H MoS_(2)heterojunction via lithium intercalation and evaluated the HER activity using on-chip electrocatalytic microdevices(OCEMs).The heterojunction achieved an overpotential of only 226 mV at a cathodic current density of 10 mA/cm^(2),outperforming the basal planes of 1T and 2H MoS_(2).Furthermore,density functional theory(DFT)calculations demonstrated that the charge redistribution occurs at the 1T-2H MoS_(2)interface with electrons transferring from 1T to 2H MoS_(2),and the interfacial S atom at the top site of 1T MoS_(2)presents the smallest overpotential of 0.37 ***,the interference from highly active edge sites was avoided by precisely exposing specific active areas,quantitatively revealing the catalytic activity order of different types of in-plane MoS_(2)active *** work enables a systematic investigation of the HER activity of various active sites in MoS_(2),laying the foundation for quantitative analysis of activity in other lowdimensional materials.

关键词： on-chip microdevice phase transition heterojunction MoS_(2) hydrogen evolution reaction(HER)

Spin-glass behavior in the competing CoCrGaO_(4)cubic spinel system

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Nano Research 2025年第1期18卷 501-507页

作者： Jiyu Hu Jiangli Ni Zhenfa Zi Chaocheng Liu School of physics and Materials Engineering Hefei Normal UniversityHefei 230009China national Synchrotron Radiation laboratory University of Science and Technology of ChinaHefei 230026China

Spin glasses(SGs),generally defined as disordered systems with randomized competing interactions,are widely investigated complex *** the ground states of spin glasses is crucial for understanding the nature of disordered magnets and many other physical manifestations,while also helping to solve some hard combinatorial optimization problems across multiple ***,the intrinsic cause of SG has always been elusive,especially in spinel oxide ***,we report the SG behavior observed in the cubic spinel oxides CoCrGaO_(4),and provide a comprehensive understanding of its intrinsic *** results indicate a frustrated state under multi-magnetic competition,and the features of SG are confirmed by susceptibility *** fitting parameters ofτ0,T0,and zv of isothermal remanent magnetization further reveal the relaxation behavior and strong spin ***,the varying exchange coupling under different temperatures and magnetic fields is unveiled,which should be responsible for the disordered *** studies unravel the underlying mechanism responsible for doping-induced magnetic frustration and introduce CoCrGaO_(4)as a potential platform for investigating spin glass behavior,thereby advancing fundamental research on frustrated magnetism within the spinel system.

关键词： spin glass(SG) magnetic frustration magnetic competition spinel ferrites

Constraints on holographic QCD phase transitions from PTA observations

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 71-78页

作者： Song He Li Li Sai Wang Shao-Jiang Wang Center for Theoretical physics and College of physics Jilin University School of Physical Science and Technology Ningbo University Max Planck Institute for Gravitational physics (Albert Einstein Institute) CAS Key laboratory of Theoretical physics Institute of Theoretical Physics Chinese Academy of Sciences School of Fundamental physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of Sciences (UCAS) School of Physical Sciences University of Chinese Academy of Sciences (UCAS) Theoretical physics Division Institute of High Energy Physics Chinese Academy of Sciences

The underlying physics of QCD phase transition in the early Universe remains largely unknown due to its strong-coupling nature during the quark-gluon plasma/hadron gas transition, yet a holographic model has been proposed to quantitatively fit the lattice QCD data while with its duration of the first-order phase transition(FoPT) left undetermined. At specific baryon chemical potential, the first-order QCD phase transition agrees with the observational constraint of baryon asymmetry. It, therefore, provides a scenario for phase transition gravitational waves(GWs) within the standard model of particle physics. If these background GWs could contribute dominantly to the recently claimed common-spectrum red noise from pulsar timing array(PTA) observations, the duration of this FoPT can be well constrained, and the associated primordial black holes are still allowed by current observations.

关键词： pulsar timing array QCD phase transition gravitational waves primordial black holes

Vector meson's spin alignments in high energy reactions

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 5-20页

作者： Jin-Hui Chen Zuo-Tang Liang Yu-Gang Ma Xin-Li Sheng Qun Wang Key laboratory of Nuclear physics and Ion-beam Application (MoE) Institute of Modern PhysicsFudan University Institute of Frontier and Interdisciplinary Science Key Laboratory of Particle Physics and Particle Irradiation (MOE)Shandong University INFN-Firenze Department of Modern physics University of Science and Technology of China School of Mechanics and physics Anhui University of Science and Technology

The global spin alignment of vector mesons has been observed by the STAR collaboration at the Relativistic Heavy Ion Collider （RHIC） at Brookhaven national laboratory （BNL）.It provides a unique opportunity to probe the correlation between the polarized quark and antiquark in the strongly coupled quark-gluon plasma （sQGP） produced in relativistic heavy ion collisions,opening a new window to explore the properties of s *** addition,spin alignments of vector mesons have also been observed in other high-energy particle collisions such as e+e-annihilations at high energies where hadron production is dominated by quark fragmentation *** results obtained are quite different from those obtained in heavy ion collisions where quark coalescence/combination mechanism dominates suggesting strong dependence on hadronization *** comprehensive studies in different hadronization processes are *** this article,we present a brief review of theoretical and experimental advances in the study of vector meson’s spin alignments in a variety of high-energy particle collisions,with emphasis on hadronization mechanisms.

关键词： vector meson spin alignment global polarization relativistic heavy ion collisions fragmentation

Unraveling post-growth mechanisms of monolayer CsPbBr3 nanocubes:Laser-enhanced transformations and cathodoluminescence-electron microscopy correlations

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Journal of Energy Chemistry 2025年第1期100卷 146-156页

作者： Mingxing Li Xiaoge Wang Xiaofan Cao Zhiqun He Chunjun Liang Mingxing Chen Jing Ju Fangtian You Key laboratory of Luminescence and Optical Information Ministry of Education Institute of Optoelectronic Technology Beijing Jiaotong University Beijing national laboratory for Molecular Sciences (BNLMS) College of Chemistry and Molecular Engineering Peking University

Lead-halide perovskite nanoparticles（LHP NPs） are highly promising materials for next-generation displays and solid-state lighting due to their exceptional optical properties. However, their inherent instability presents a significant challenge. Recent advances have demonstrated that optoelectronic devices based on monolayer nanoparticle films exhibit both high luminescence efficiency and long-term *** research demonstrates that mobility limitations and anisotropic alignments in CsPbBr3nanocube monolayer films are key to their stabilization, hindering spontaneous growth through face-to-face fusion and resulting in the formation of connecting necks in a diagonal direction. Introducing laser irradiation confirmed this by significantly accelerating nanocubes growth, increasing mobility, and enhancing local structural ordering, leading to larger and more regularly shaped nanosheets. Fourier transform infrared spectroscopy and energy dispersive spectroscopy line-scan analyses indicated that laser irradiation did not disrupt the ligand structure. Transmission electron microscopy and correlative cathodoluminescence electron microscopy revealed the effects of post-growth and heterogeneous structures, including enhanced luminescence and inhomogeneous intensity in the nanosheets. These findings deepen the understanding of the post-growth mechanism of monolayer nanoparticles and the structure-emission correlation and highlight the unique role of laser irradiation in directing the formation of well-defined and regular nanostructures.

关键词： Post-growth mechanism Heterogeneous structure Single-particle spectroscopy Laser irradiation

The detection, extraction and parameter estimation of extreme-mass-ratio inspirals with deep learning

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 86-96页

作者： Qianyun Yun Wen-Biao Han Yi-Yang Guo He Wang Minghui Du Hangzhou Institute for Advanced Study University of Chinese Academy of Sciences Shanghai Astronomical Observatory Chinese Academy of Sciences School of physics and Astronomy Shanghai Jiao Tong University School of Astronomy and Space Science University of Chinese Academy of Sciences Taiji laboratory for Gravitational Wave Universe (Beijing/Hangzhou) University of Chinese Academy of Sciences Lanzhou Center for Theoretical physics Key Laboratory of Theoretical Physics of Gansu Province Key Laboratory of Quantum Theory and Applications of MoE Lanzhou University Institute of Theoretical physics & Research Center of Gravitation Lanzhou University International Centre for Theoretical physics Asia-Pacific (ICTP-AP) University of Chinese Academy of Sciences (UCAS) Center for Gravitational Wave Experiment National Microgravity Laboratory Institute of Mechanics Chinese Academy of Sciences

One of the primary goals of space-borne gravitational wave detectors is to detect and analyze extreme-mass-ratio inspirals(EMRIs). This task is particularly challenging because EMRI signals are complex, lengthy, and faint. In this work, we introduce a2-layer convolutional neural network(CNN) approach to detect EMRI signals for space-borne detectors, achieving a true positive rate(TPR) of 96.9% at a 1% false positive rate(FPR) for signal-to-noise ratio(SNR) from 50 to 100. Especially, the key intrinsic parameters of EMRIs such as the mass, spin of the supermassive black hole(SMBH) and the initial eccentricity of the orbit can also be inferred directly by employing a neural network. The mass and spin of the SMBH can be determined at 99% and 92% respectively. This will greatly reduce the parameter spaces and computing cost for the following Bayesian parameter *** model also has a low dependency on the accuracy of the waveform model. This study underscores the potential of deep learning methods in EMRI data analysis, enabling the rapid detection of EMRI signals and efficient parameter estimation.

关键词： gravitational wave EMRIs deep-learing

Laser beam induced current microscopy and photocurrent mapping for junction characterization of infrared photodetectors

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Science China(physics,Mechanics & Astronomy) 2015年第2期58卷 1-13页

作者： QIU WeiCheng HU WeiDa national laboratory for infrared physics Shanghai Institute of Technical Physics Chinese Academy of Sciences

For non-destructive optical characterization, laser beam induced current(LBIC) microscopy has been developed into as a quantitative tool to examine individual photodiodes within a large pixel array. Two-dimensional LBIC microscopy, also generally called photocurrent mapping(PC mapping), can provide spatially resolved information about local electrical properties and p-n junction formation in photovoltaic infrared(including visible light) photodetectors from which it is possible to extract material and device parameters such as junction area, junction depth, diffusion length, leakage current position and minority carrier diffusion length etc. This paper presents a comprehensive review of research background, operating principle, fundamental issues, and applications of LBIC or PC mapping.

关键词： laser beam induced current photocurrent mapping focal plane array photocurrent infrared photodetector

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Local-contrastive-learning machine with both generalization and adversarial robustness: A statistical physics analysis

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Science China(physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 109-123页

作者： Mingshan Xie Yuchen Wang Haiping Huang PMI Lab School of Physics Sun Yat-sen University Guangdong Provincial Key laboratory of Magnetoelectric physics and Devices Sun Yat-sen University

Distinct from human cognitive processing, deep neural networks trained by backpropagation can be easily fooled by adversarial examples. To design a semantically meaningful representation learning, we discard backpropagation, and instead, propose a local contrastive learning, where the representations for the inputs bearing the same label shrink(akin to boson) in hidden layers,while those of different labels repel(akin to fermion). This layer-wise learning is local in nature, being biologically plausible.A statistical mechanics analysis shows that the target fermion-pair-distance is a key parameter. Moreover, the application of this local contrastive learning to MNIST benchmark dataset demonstrates that the adversarial vulnerability of standard perceptron can be greatly mitigated by tuning the target distance, i.e., controlling the geometric separation of prototype manifolds.

关键词： machine learning statistical mechanics adversarial robustness neural networks