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15 November 2024, Volume 33 Issue 11 Previous issue    Next issue

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TOPICAL REVIEW — Stephen J. Pennycook: A research life in atomic-resolution STEM and EELS

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Physics through the microscope Stephen J. Pennycook, Ryo Ishikawa, Haijun Wu(武海军), Xiaoxu Zhao(赵晓续), Changjian Li(黎长建), Duane Loh, Jiadong Dan, and Wu Zhou(周武) Chin. Phys. B, 2024, 33 (11):  116801.  DOI: 10.1088/1674-1056/ad7aff Abstract ( 24 )   PDF (9989KB) ( 11 )   The electron microscope provides numerous insights into physics, from demonstrations of fundamental quantum mechanical principles to the physics of imaging and materials. It reveals the atomic and electronic structure of key regions such as defects and interfaces. We can learn the underlying physics governing properties, and gain insight into how to synthesize new materials with improved properties. Some recent advances and possible future directions are discussed.

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Atomic-level quantitative analysis of electronic functional materials by aberration-corrected STEM Wanbo Qu(曲万博), Zhihao Zhao(赵志昊), Yuxuan Yang(杨宇轩), Yang Zhang(张杨), Shengwu Guo(郭生武), Fei Li(李飞), Xiangdong Ding(丁向东), Jun Sun(孙军), and Haijun Wu(武海军) Chin. Phys. B, 2024, 33 (11):  116802.  DOI: 10.1088/1674-1056/ad7afc Abstract ( 28 )   PDF (2506KB) ( 4 )   The stable sub-angstrom resolution of the aberration-corrected scanning transmission electron microscope (AC-STEM) makes it an advanced and practical characterization technique for all materials. Owing to the prosperous advancement in computational technology, specialized software and programs have emerged as potent facilitators across the entirety of electron microscopy characterization process. Utilizing advanced image processing algorithms promotes the rectification of image distortions, concurrently elevating the overall image quality to superior standards. Extracting high-resolution, pixel-level discrete information and converting it into atomic-scale, followed by performing statistical calculations on the physical matters of interest through quantitative analysis, represent an effective strategy to maximize the value of electron microscope images. The efficacious utilization of quantitative analysis of electron microscope images has become a progressively prominent consideration for materials scientists and electron microscopy researchers. This article offers a concise overview of the pivotal procedures in quantitative analysis and summarizes the computational methodologies involved from three perspectives: contrast, lattice and strain, as well as atomic displacements and polarization. It further elaborates on practical applications of these methods in electronic functional materials, notably in piezoelectrics/ferroelectrics and thermoelectrics. It emphasizes the indispensable role of quantitative analysis in fundamental theoretical research, elucidating the structure-property correlations in high-performance systems, and guiding synthesis strategies.

SPECIAL TOPIC — Stephen J. Pennycook: A research life in atomic-resolution STEM and EELS

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Making the link between ADF and 4D STEM: Resolution, transfer and coherence Peter D. Nellist and Timothy J. Pennycook Chin. Phys. B, 2024, 33 (11):  116803.  DOI: 10.1088/1674-1056/ad8554 Abstract ( 25 )   PDF (1608KB) ( 2 )   Steve Pennycook is a pioneer in the application of high-resolution scanning transmission electron microscopy (STEM) and in particular the use of annular dark-field (ADF) imaging. Here we show how a general framework for 4D STEM allows clear links to be made between ADF imaging and the emerging methods for reconstructing images from 4D STEM data sets. We show that both ADF imaging and ptychographical reconstruction can be thought of in terms of integrating over the overlap regions of diffracted discs in the detector plane. This approach allows the similarities in parts of their transfer functions to be understood, though we note that the transfer functions for ptychographic imaging cannot be used as a measure of information transfer. We also show that conditions of partial spatial and temporal coherence affect ADF imaging and ptychography similarly, showing that achromatic interference can always contribute to the image in both cases, leading to a robustness to partial temporal coherence that has enabled high-resolution imaging.

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Real-time four-dimensional scanning transmission electron microscopy through sparse sampling A W Robinson, J Wells, A Moshtaghpour, D Nicholls, C Huang, A Velazco-Torrejon, G Nicotra, A I Kirkland, and N D Browning Chin. Phys. B, 2024, 33 (11):  116804.  DOI: 10.1088/1674-1056/ad8a4a Abstract ( 38 )   PDF (3014KB) ( 99 )   Four-dimensional scanning transmission electron microscopy (4-D STEM) is a state-of-the-art image acquisition mode used to reveal high and low mass elements at atomic resolution. The acquisition of the electron momenta at each real space probe location allows for various analyses to be performed from a single dataset, including virtual imaging, electric field analysis, as well as analytical or iterative extraction of the object induced phase shift. However, the limiting factor in 4-D STEM is the speed of acquisition which is bottlenecked by the read-out speed of the camera, which must capture a convergent beam electron diffraction (CBED) pattern at each probe position in the scan. Recent developments in sparse sampling and image inpainting (a branch of compressive sensing) for STEM have allowed for real-time recovery of sparsely acquired data from fixed monolithic detectors, Further developments in compressive sensing for 4-D STEM have also demonstrated that acquisition speeds can be increased, i.e., live video rate 4-D imaging is now possible. In this work, we demonstrate the first practical implementations of compressive 4-D STEM for real-time inference on two different scanning transmission electron microscopes.

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Polarization pinning at antiphase boundaries in multiferroic YbFeO3 Guodong Ren, Pravan Omprakash, Xin Li, Yu Yun, Arashdeep S. Thind, Xiaoshan Xu, and Rohan Mishra Chin. Phys. B, 2024, 33 (11):  118502.  DOI: 10.1088/1674-1056/ad8cbc Abstract ( 23 )   PDF (3024KB) ( 5 )   The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain walls. We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO$_{3}$. We have directly resolved the atomic structure of a sharp antiphase boundary (APB) in YbFeO$_{3}$ thin films using a combination of aberration-corrected scanning transmission electron microscopy (STEM) and total energy calculations based on density-functional theory (DFT). We find the presence of a layer of FeO$_{6}$ octahedra at the APB that bridges the adjacent domains. STEM imaging shows a reversal in the direction of polarization on moving across the APB, which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO$_{6}$ octahedral layer at the APB. Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains.

SPECIAL TOPIC — Quantum communication and quantum network

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Generation of broadband polarization-orthogonal photon pairs via the dispersion-engineered thin-film lithium niobate waveguide Ji-Ning Zhang(张继宁), Tong-Yu Zhang(张同宇), Jia-Chen Duan(端家晨), Yan-Xiao Gong(龚彦晓), and Shi-Ning Zhu(祝世宁) Chin. Phys. B, 2024, 33 (11):  110301.  DOI: 10.1088/1674-1056/ad757c Abstract ( 54 )   PDF (660KB) ( 9 )   Broadband photon pairs are highly desirable for quantum metrology, quantum sensing, and quantum communication. Such sources are usually designed through type-0 phase-matching spontaneous parametric down-conversion (SPDC) that makes the photon pairs hard to separate in the frequency-degenerate case and thus limits their applications. In this paper, we design a broadband frequency-degenerate telecom-band photon pair source via the type-II SPDC in a dispersion-engineered thin-film lithium niobate waveguide, where the polarization modes of photon pairs are orthogonal and thus are easily separated deterministically. With a 5-mm-long waveguide, our design can achieve a bandwidth of 5.56 THz (44.8 nm), which is 8.6 times larger than that of the bulk lithium niobate, and the central wavelength can be flexibly adjusted. Our design is a promising approach towards high-quality integrated photon sources and may have wide applications in photonic quantum technologies.

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Improved model on asynchronous measurement-device-independent quantum key distribution with realistic devices Mingshuo Sun(孙铭烁), Chun-Hui Zhang(张春辉), Rui Zhang(章睿), Xing-Yu Zhou(周星宇), Jian Li(李剑), and Qin Wang(王琴) Chin. Phys. B, 2024, 33 (11):  110302.  DOI: 10.1088/1674-1056/ad757a Abstract ( 49 )   PDF (799KB) ( 3 )   In principle, the asynchronous measurement-device-independent quantum key distribution (AMDI-QKD) can surpass the key rate capacity without phase tracking and phase locking. However, practical imperfections in sources or detections would dramatically depress its performance. Here, we present an improved model on AMDI-QKD to reduce the influence of these imperfections, including intensity fluctuation, the afterpulse effect, and the dead time of detectors. Furthermore, we carry out corresponding numerical simulations. Simulation results show that, by implementing our present work, it can have more than 100 km longer secure transmission distance and one order of magnitude enhancement in the key generation rate after 320 km compared with the standard method. Moreover, our model can still break the Pirandola-Laurenza-Ottaviani-Banchi (PLOB) bound even under realistic experimental conditions.

SPECIAL TOPIC — Fabrication and manipulation of the second-generation quantum systems

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In situ non-destructive measurement of Josephson junction resistance using fritting contact technique Lei Du(杜磊), Hao-Ran Tao(陶浩然), Liang-Liang Guo(郭亮亮), Hai-Feng Zhang(张海峰), Yong Chen(陈勇), Xin Tian(田昕), Chi Zhang(张驰), Zhi-Long Jia(贾志龙), Peng Duan(段鹏), and Guo-Ping Guo(郭国平) Chin. Phys. B, 2024, 33 (11):  110309.  DOI: 10.1088/1674-1056/ad73b6 Abstract ( 47 )   PDF (728KB) ( 6 )   Conventional four-probe methods for measuring the resistance of Josephson junctions can damage superconducting thin films, making them unsuitable for frequency measurements of superconducting qubits. In this study, we present a custom probe station measurement system that employs the fritting contact technique to achieve in situ, non-destructive measurements of Josephson junction resistance. Our experimental results demonstrate that this method allows for accurate prediction of qubit frequency with an error margin of 17.2 MHz. Moreover, the fritting contact technique does not significantly affect qubit coherence time or the integrity of the superconducting film, confirming its non-destructive nature. This innovative approach provides a dependable foundation for frequency tuning and addressing frequency collision issues, thus supporting the advancement and practical deployment of superconducting quantum computing.

DATA PAPER

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Light emission from multiple self-trapped excitons in one-dimensional Ag-based ternary halides Jiahao Xie(颉家豪), Zewei Li(李泽唯), Shengqiao Wang(王晟侨), and Lijun Zhang(张立军) Chin. Phys. B, 2024, 33 (11):  117102.  DOI: 10.1088/1674-1056/ad7e9c Abstract ( 39 )   PDF (1270KB) ( 20 )   Ternary metal halides based on Cu(I) and Ag(I) have attracted intensive attention in optoelectronic applications due to their excellent luminescent properties, low toxicity, and robust stability. While the self-trapped excitons (STEs) emission mechanisms of Cu(I) halides are well understood, the STEs in Ag(I) halides remain less thoroughly explored. This study explores the STE emission efficiency within the $A_{2}$Ag$X_{3}$ ($A = {\rm Rb}$, Cs; $X = {\rm Cl}$, Br, I) system by identifying three distinct STE states in each material and calculating their configuration coordinate diagrams. We find that the STE emission efficiency in this system is mainly determined by STE stability and influenced by self-trapping and quenching barriers. Moreover, we investigate the impact of structural compactness on emission efficiency and find that the excessive electron-phonon coupling in this system can be reduced by increasing the structural compactness. The atomic packing factor is identified as a low-cost and effective descriptor for predicting STE emission efficiency in both Cs$_{2}$Ag$X_{3}$ and Rb$_{2}$Ag$X_{3}$ systems. These findings can deepen our understanding of STE behavior in metal halide materials and offer valuable insights for the design of efficient STE luminescent materials. The datasets presented in this paper are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.12094.

INSTRUMENTATION AND MEASUREMENT

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Optical design of the time-resolved ARPES beamline of the new material spectroscopy experimental station for the update of CAEP THz-FEL facility Liang-Liang Du(杜亮亮), Li-Min Meng(孟立民), Jiang Li(李江), and Li-Guo Zhu(朱礼国) Chin. Phys. B, 2024, 33 (11):  114203.  DOI: 10.1088/1674-1056/ad73b1 Abstract ( 46 )   PDF (605KB) ( 6 )   The Chinese Academy of Engineering Physics Terahertz Free Electron Laser Facility (CAEP THz FEL, CTFEL) is the only high-average power free electron laser terahertz source based on superconducting accelerators in China. The update of the CTFEL is now undergoing and will expand the frequency range from 0.1-4.2 THz to 0.1-125 THz. Two experimental stations for material spectroscopy and biomedicine will be built. A high harmonic generation (HHG) lightsource based beamline at the material spectroscopy experimental station for time-resolved angle-resolved photoemission spectroscopy (ARPES) research will be constructed and the optical design is presented. The HHG lightsource covers the extreme ultraviolet (XUV) photon energy range of 20-50 eV. A Czerny-Turner monochromator with two plane gratings worked in conical diffraction configuration is employed to maintain the transmission efficiency and preserve the pulse time duration. The calculated beamline transmission efficiency is better than 5% in the whole photon energy range. To our knowledge, this is the first time in China to combine THz-infrared FEL with HHG light source, and this experimental station will be a powerful and effective instrument that will give new research opportunities in the future for users doing research on the dynamic evolution of the excited electron band structure of a material's surface.

COMPUTATIONAL PROGRAMS FOR PHYSICS

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A hybrid method integrating Green's function Monte Carlo and projected entangled pair states He-Yu Lin(林赫羽), Rong-Qiang He(贺荣强), Yibin Guo (郭奕斌), and Zhong-Yi Lu(卢仲毅) Chin. Phys. B, 2024, 33 (11):  117504.  DOI: 10.1088/1674-1056/ad84c9 Abstract ( 34 )   PDF (2198KB) ( 9 )   This paper introduces a hybrid approach combining Green's function Monte Carlo (GFMC) method with projected entangled pair state (PEPS) ansatz. This hybrid method regards PEPS as a trial state and a guiding wave function in GFMC. By leveraging PEPS's proficiency in capturing quantum state entanglement and GFMC's efficient parallel architecture, the hybrid method is well-suited for the accurate and efficient treatment of frustrated quantum spin systems. As a benchmark, we applied this approach to study the frustrated $J_1$-$J_2$ Heisenberg model on a square lattice with periodic boundary conditions (PBCs). Compared with other numerical methods, our approach integrating PEPS and GFMC shows competitive accuracy in the performance of ground-state energy. This paper provides systematic and comprehensive discussion of the approach of our previous work [Phys. Rev. B 109 235133 (2024)].

RAPID COMMUNICATION

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Model on picometer-level light gravitational delay in the GRACE Follow-On-like missions Hot! Jin-Zhuang Dong(董金壮), Wei-Sheng Huang(黄玮圣), Cheng-Gang Qin(秦成刚), Yu-Jie Tan(谈玉杰), and Cheng-Gang Shao(邵成刚) Chin. Phys. B, 2024, 33 (11):  110401.  DOI: 10.1088/1674-1056/ad7af9 Abstract ( 50 )   PDF (694KB) ( 30 )   Laser interferometry plays a crucial role in laser ranging for high-precision space missions such as GRACE (Gravity Recovery and Climate Experiment) Follow-On-like missions and gravitational wave detectors. For such accuracy of modern space missions, a precise relativistic model of light propagation is required. With the post-Newtonian approximation, we utilize the Synge world function method to study the light propagation in the Earth's gravitational field, deriving the gravitational delays up to order $c^{-4}$. Then, we investigate the influences of gravitational delays in three inter-satellite laser ranging techniques, including one-way ranging, dual one-way ranging, and transponder-based ranging. By combining the parameters of Kepler orbit, the gravitational delays are expanded up to the order of $e^2$ ($e$ is the orbital eccentricity). Finally, considering the GRACE Follow-On-like missions, we estimate the gravitational delays to the level of picometer. The results demonstrate some high-order gravitational and coupling effects, such as $c^{-4}$-order gravitational delays and coupling of Shapiro and beat frequency, which may be non-negligible for higher precision laser ranging in the future.

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Gas encapsulation technology for large volume press Hot! Minghao Du(杜明浩) and Duanwei He(贺端威) Chin. Phys. B, 2024, 33 (11):  110701.  DOI: 10.1088/1674-1056/ad7af8 Abstract ( 17 )   PDF (9728KB) ( 3 )   For samples in the gaseous state at room temperature and ambient pressure, mature technology has been developed to encapsulate them in a diamond anvil cell (DAC). However, the large volume press (LVP) can only treat samples with starting materials in solid or liquid form. We have achieved stable encapsulation and reaction treatment of carbon dioxide in a centimeter sized sample chamber for a long time (over 10 min) under conditions of temperature higher than 1200 ℃ and pressure over 5 GPa through the use of integrated low-temperature freezing and rapid compression sealing method for LVP cell assemblies. This technology can also be applied to the packaging of other gaseous or liquid samples, such as ammonia, sulfur dioxide, water, etc. in LVP devices.

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Proton acceleration in plasma turbulence driven by high-energy lepton jets Hot! Gaowei Zhang(张高维), Zhengming Sheng(盛政明), Suming Weng(翁苏明), Min Chen(陈民), and Jie Zhang(张杰) Chin. Phys. B, 2024, 33 (11):  115203.  DOI: 10.1088/1674-1056/ad7b01 Abstract ( 34 )   PDF (4120KB) ( 4 )   The interaction of high energy lepton jets composed of electrons and positrons with background electron-proton plasma is investigated numerically based upon particle-in-cell simulation, focusing on the acceleration processes of background protons due to the development of electromagnetic turbulence. Such interaction may be found in the universe when energetic lepton jets propagate in the interstellar media. When such a jet is injected into the background plasma, the Weibel instability is excited quickly, which leads to the development of plasma turbulence into the nonlinear stage. The turbulent electric and magnetic fields accelerate plasma particles via the Fermi II type acceleration, where the maximum energy of both electrons and protons can be accelerated to much higher than that of the incident jet particles. Because of background plasma acceleration, a collisionless electrostatic shock wave is formed, where some pre-accelerated protons are further accelerated when passing through the shock wave front. Dependence of proton acceleration on the beam-plasma density ratio and beam energy is investigated. For a given background plasma density, the maximum proton energy generally increases both with the density and kinetic energy of the injected jet. Moreover, for a homogeneous background plasma, the proton acceleration via both turbulent fields and collisionless shocks is found to be significant. In the case of an inhomogeneous plasma, the proton acceleration in the plasma turbulence is dominant. Our studies illustrate a scenario where protons from background plasma can be accelerated successively by the turbulent fields and collisionless shocks.

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Liquid crystal droplets formation and stabilization during phase transition process Hot! Xia Meng(孟霞), Jiayao Ye(叶家耀), Ao Li(李澳), Xudong Zhu(朱徐栋), Zhaoyan Yang(杨朝雁), Lei Wang(王磊), Bingxiang Li(李炳祥), and Yanqing Lu(陆延青) Chin. Phys. B, 2024, 33 (11):  116101.  DOI: 10.1088/1674-1056/ad7afd Abstract ( 33 )   PDF (2686KB) ( 11 )   The study of phase transition processes in liquid crystals (LCs) remains challenging. Most thermotropic LCs exhibit a narrow temperature range and a rapid phase transition from the isotropic (ISO) to the nematic (N) phase, which make it difficult to capture and manipulate the phase transition process. In this study, we observed the evolution of small droplets during the ISO-N phase transition in ferroelectric nematic (N$_{\rm F}$) LC RM734. After doping with metal nanoparticles (NPs), the temperature range of the phase transition broadened, and the droplets formed during the phase transition remained stable, with their diameter increasing linearly with temperature. In addition, droplets doped with NPs can be well controlled by an external electric field. This discovery not only aids in understanding the fundamental mechanisms of LC phase transitions but also provides a simple alternative method for preparing droplets, which is potentially valuable for applications in optoelectronic devices and sensors.

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Visualizing the electronic structure of kagome magnet LuMn6Sn6 by angle-resolved photoemission spectroscopy Hot! Man Li(李满), Qi Wang(王琦), Liqin Zhou(周丽琴), Wenhua Song(宋文华), Huan Ma(马欢), Pengfei Ding(丁鹏飞), Alexander Fedorov, Yaobo Huang(黄耀波), Bernd Büchner, Hechang Lei(雷和畅), Shancai Wang(王善才), and Rui Lou(娄睿) Chin. Phys. B, 2024, 33 (11):  117101.  DOI: 10.1088/1674-1056/ad7afe Abstract ( 92 )   PDF (5542KB) ( 149 )   Searching for the dispersionless flat band (FB) in quantum materials, especially in topological systems, becomes an interesting topic. The kagome lattice is an ideal platform for such exploration because the FB can be naturally induced by the underlying destructive interference. Nevertheless, the magnetic kagome system that hosts the FB close to the Fermi level ($E_{\rm F}$) is exceptionally rare. Here, we study the electronic structure of a kagome magnet LuMn$_6$Sn$_6$ by combining angle-resolved photoemission spectroscopy and density functional theory calculations. The observed Fermi-surface topology and overall band dispersions are similar to previous studies of the $X$Mn$_6$Sn$_6$ ($X = {\rm Dy}$, Tb, Gd, Y) family of compounds. We clearly observe two kagome-derived FBs extending through the entire Brillouin zone, and one of them is located just below $E_{\rm F}$. The photon-energy-dependent measurements reveal that these FBs are nearly dispersionless along the $k_z$ direction as well, supporting the quasi-two-dimensional character of such FBs. Our results complement the $X$Mn$_6$Sn$_6$ family and demonstrate the robustness of the FB features across this family.

GENERAL

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Prediction of ILI following the COVID-19 pandemic in China by using a partial differential equation Xu Zhang(张栩), Yu-Rong Song(宋玉蓉), and Ru-Qi Li(李汝琦) Chin. Phys. B, 2024, 33 (11):  110201.  DOI: 10.1088/1674-1056/ad6f90 Abstract ( 43 )   PDF (709KB) ( 10 )   The COVID-19 outbreak has significantly disrupted the lives of individuals worldwide. Following the lifting of COVID-19 interventions, there is a heightened risk of future outbreaks from other circulating respiratory infections, such as influenza-like illness (ILI). Accurate prediction models for ILI cases are crucial in enabling governments to implement necessary measures and persuade individuals to adopt personal precautions against the disease. This paper aims to provide a forecasting model for ILI cases with actual cases. We propose a specific model utilizing the partial differential equation (PDE) that will be developed and validated using real-world data obtained from the Chinese National Influenza Center. Our model combines the effects of transboundary spread among regions in China mainland and human activities' impact on ILI transmission dynamics. The simulated results demonstrate that our model achieves excellent predictive performance. Additionally, relevant factors influencing the dissemination are further examined in our analysis. Furthermore, we investigate the effectiveness of travel restrictions on ILI cases. Results can be used to utilize to mitigate the spread of disease.

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Spatial patterns of the Brusselator model with asymmetric Lévy diffusion Hongwei Yin(尹洪位), Shangtao Yang(杨尚涛), Xiaoqing Wen(文小庆), Haohua Wang(王浩华), and Shufen Yang(杨淑芬) Chin. Phys. B, 2024, 33 (11):  110202.  DOI: 10.1088/1674-1056/ad74e5 Abstract ( 60 )   PDF (2221KB) ( 15 )   The formation of spatial patterns is an important issue in reaction-diffusion systems. Previous studies have mainly focused on the spatial patterns in reaction-diffusion models equipped with symmetric diffusion (such as normal or fractional Laplace diffusion), namely, assuming that spatial environments of the systems are homogeneous. However, the complexity and heterogeneity of spatial environments of biochemical reactions in vivo can lead to asymmetric diffusion of reactants. Naturally, there arises an open question of how the asymmetric diffusion affects dynamical behaviors of biochemical reaction systems. To answer this, we build a general asymmetric Lévy diffusion model based on the theory of a continuous time random walk. In addition, we investigate the two-species Brusselator model with asymmetric Lévy diffusion, and obtain a general condition for the formation of Turing and wave patterns. More interestingly, we find that even though the Brusselator model with symmetric diffusion cannot produce steady spatial patterns for some parameters, the asymmetry of Lévy diffusion for this model can produce wave patterns. This is different from the previous result that wave instability requires at least a three-species model. In addition, the asymmetry of Lévy diffusion can significantly affect the amplitude and frequency of the spatial patterns. Our results enrich our knowledge of the mechanisms of pattern formation.

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Stochastic modeling and analysis of hepatitis and tuberculosis co-infection dynamics Sayed Murad Ali Shah, Yufeng Nie(聂玉峰), Anwarud Din, Abdulwasea Alkhazzan, and Bushra Younas Chin. Phys. B, 2024, 33 (11):  110203.  DOI: 10.1088/1674-1056/ad7afa Abstract ( 39 )   PDF (1041KB) ( 4 )   Several mathematical models have been developed to investigate the dynamics of tuberculosis (TB) and hepatitis B virus (HBV). Numerous current models for TB, HBV, and their co-dynamics fall short in capturing the important and practical aspect of unpredictability. It is crucial to take into account a stochastic co-infection HBV-TB epidemic model since different random elements have a substantial impact on the overall dynamics of these diseases. We provide a novel stochastic co-model for TB and HBV in this study, and we establish criteria on the uniqueness and existence of a non-negative global solution. We also looked at the persistence of the infections as long its dynamics are governable by the proposed model. To verify the theoretical conclusions, numerical simulations are presented keeping in view the associated analytical results. The infections are found to finally die out and go extinct with certainty when Lévy intensities surpass the specified thresholds and the related stochastic thresholds fall below unity. The findings also demonstrate the impact of noise on the decline in the co-circulation of HBV and TB in a given population. Our results provide insights into effective intervention strategies, ultimately aiming to improve the management and control of TB and HBV co-infections.

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Asymptotic analysis on bright solitons and breather solutions of a generalized higher-order nonlinear Schrödinger equation in an optical fiber or a planar waveguide Xin Zhao(赵鑫), Zhong Du(杜仲), Li-Jian Zhou(周立俭), Rong-Xiang Liu(刘荣香), and Xu-Hu Wang(王绪虎) Chin. Phys. B, 2024, 33 (11):  110204.  DOI: 10.1088/1674-1056/ad7e9e Abstract ( 46 )   PDF (1196KB) ( 4 )   We study a generalized higher-order nonlinear Schrödinger equation in an optical fiber or a planar waveguide. We obtain the Lax pair and $N$-fold Darboux transformation (DT) with $N$ being a positive integer. Based on Lax pair obtained by us, we derive the infinitely-many conservation laws. We give the bright one-, two-, and $N$-soliton solutions, and the first-, second-, and $N$th-order breather solutions based on the $N$-fold DT. We conclude that the velocities of the bright solitons are influenced by the distributed gain function, $g(z)$, and variable coefficients in equation, $h_1(z)$, $p_1(z)$, $r_1(z)$, and $s_1(z)$ via the asymptotic analysis, where $ z $ represents the propagation variable or spatial coordinate. We also graphically observe that: the velocities of the first- and second-order breathers will be affected by $h_1(z)$, $p_1(z)$, $r_1(z)$, and $s_1(z)$, and the background wave depends on $g(z)$.

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Sliding-mode-based preassigned-time control of a class of memristor chaotic systems Jinrong Fan(樊金荣), Qiang Lai(赖强), Qiming Wang(汪其铭), and Leimin Wang(王雷敏) Chin. Phys. B, 2024, 33 (11):  110205.  DOI: 10.1088/1674-1056/ad7e9d Abstract ( 41 )   PDF (877KB) ( 3 )   This paper addresses the preassigned-time chaos control problem of memristor chaotic systems with time delays. Since the introduction of memristor, the presented models are nonlinear systems with chaotic dynamics. First, the TS fuzzy method is adopted to describe the chaotic systems. Then, a sliding-model-based control approach is proposed to achieve the preassigned-time stabilization of the presented models, where the upper bound of stabilization time can be arbitrarily specified in advance. Finally, simulation results demonstrate the validity of presented control approach and theoretic results.

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Abundant invariant solutions of extended (3+1)-dimensional KP-Boussinesq equation Hengchun Hu(胡恒春) and Jiali Kang(康佳丽) Chin. Phys. B, 2024, 33 (11):  110206.  DOI: 10.1088/1674-1056/ad7fd1 Abstract ( 38 )   PDF (1483KB) ( 2 )   Lie group analysis method is applied to the extended $(3+1)$-dimensional Kadomtsev-Petviashvili-Boussinesq equation and the corresponding similarity reduction equations are obtained with various infinitesimal generators. By selecting suitable arbitrary functions in the similarity reduction solutions, we obtain abundant invariant solutions, including the trigonometric solution, the kink-lump interaction solution, the interaction solution between lump wave and triangular periodic wave, the two-kink solution, the lump solution, the interaction between a lump and two-kink and the periodic lump solution in different planes. These exact solutions are also given graphically to show the detailed structures of this high dimensional integrable system.

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Finite-time decentralized event-triggered state estimation for coupled neural networks under unreliable Markovian network against mixed cyberattacks Xiulin Wang(汪修林), Youzhi Cai(蔡有志), and Feng Li(李峰) Chin. Phys. B, 2024, 33 (11):  110207.  DOI: 10.1088/1674-1056/ad7e9a Abstract ( 35 )   PDF (1226KB) ( 2 )   This article investigates the issue of finite-time state estimation in coupled neural networks under random mixed cyberattacks, in which the Markov process is used to model the mixed cyberattacks. To optimize the utilization of channel resources, a decentralized event-triggered mechanism is adopted during the information transmission. By establishing the augmentation system and constructing the Lyapunov function, sufficient conditions are obtained for the system to be finite-time bounded and satisfy the $H_{\infty}$ performance index. Then, under these conditions, a suitable state estimator gain is obtained. Finally, the feasibility of the method is verified by a given illustrative example.

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Multi-party semi-quantum private comparison protocol of size relation based on two-dimensional Bell states Bing Wang(王冰), Li-Hua Gong(龚黎华), and San-Qiu Liu(刘三秋) Chin. Phys. B, 2024, 33 (11):  110303.  DOI: 10.1088/1674-1056/ad73ae Abstract ( 31 )   PDF (1423KB) ( 5 )   Currently, all quantum private comparison protocols based on two-dimensional quantum states can only compare equality, via using high-dimensional quantum states that it is possible to compare the size relation in existing work. In addition, it is difficult to manipulate high-dimensional quantum states under the existing conditions of quantum information processing, leading to low practicality and engineering feasibility of protocols for comparing size relation. Considering this situation, we propose an innovative protocol. The proposed protocol can make size comparison by exploiting more manageable two-dimensional Bell states, which significantly enhances its feasibility with current quantum technologies. Simultaneously, the proposed protocol enables multiple participants to compare their privacies with the semi-quantum model. The communication process of the protocol is simulated on the IBM Quantum Experience platform to verify its effectiveness. Security analysis shows that the proposed protocol can withstand common attacks while preserving the privacies of all participants. Thus, the devised protocol may provide an important reference for implementation of quantum private size comparison protocols.

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Floquet engineering of a dynamical Z2 lattice gauge field with ultracold atoms Xiangxiang Sun(孙祥祥), Hao-Yue Qi(齐浩月), Pengfei Zhang(张鹏飞), and Wei Zheng(郑炜) Chin. Phys. B, 2024, 33 (11):  110304.  DOI: 10.1088/1674-1056/ad7576 Abstract ( 45 )   PDF (1049KB) ( 3 )   Gauge field theory is a fundamental concept in modern physics, attracting many theoretical and experimental efforts towards its simulation. In this paper we propose that a simple model, in which fermions coupled to a dynamical lattice gauge field, can be engineered via the Floquet approach. The model possesses both an independent Maxwell term and local $Z_{2}$ gauge symmetry. Our proposal relies on a species-dependent optical lattice, and can be achieved in one, two or three dimensions. By a unitary transformation, this model can be mapped into a non-interacting composite fermion system with fluctuating background charge. With the help of this composite fermion picture, two characteristic observations are predicted. One is radio-frequency spectroscopy, which exhibits no dispersion in all parameter regimes. The second is dynamical localization, which depends on the structure of the initial states.

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Nonreciprocal mechanical entanglement in a spinning optomechanical system Shan-Shan Chen(陈珊珊), Jing-Jing Zhang(张京京), Jia-Neng Li(李嘉能), Na-Na Zhang(张娜娜), Yong-Rui Guo(郭永瑞), and Huan Yang(杨桓) Chin. Phys. B, 2024, 33 (11):  110305.  DOI: 10.1088/1674-1056/ad72e1 Abstract ( 39 )   PDF (895KB) ( 9 )   Quantum entanglement between distant massive mechanical oscillators is an important resource in sensitive measurements and quantum information processing. We achieve the nonreciprocal mechanical entanglement in a compound optomechanical device consisting of two mechanical oscillators and a spinning whispering-gallery mode (WGM) optical microresonator. It is found that obvious nonreciprocal mechanical entanglement emerges in this system in the presence of the Sagnac effect which is induced by the rotation of the WGM resonator, and the nonreciprocal region can be controlled by tuning the angular velocity of the rotation. The nonreciprocity originates from the breaking of the time-reversal symmetry of this multimode system due to the presence of the Sagnac effect. The optomechanical coupling and the mechanical interaction provide cooling channels for the first and second mechanical oscillators, respectively. Two mechanical oscillators can be cooled simultaneously. The simultaneous cooling and the mechanical coupling of two mechanical oscillators ensure the generation of mechanical entanglement. Furthermore, an optimal mechanical entanglement can be achieved when the moderate optical frequency detuning and the driving power are chosen. The thermal noise of the mechanical environment has a negative effect on mechanical entanglement. Our scheme provides promising opportunities for research of quantum information processing based on phonons and sensitive measurements.

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Diagnosing quantum crosstalk in superconducting quantum chips by using out-of-time-order correlators Yujia Zhang(张宇佳), Yu Zhang(张钰), Shaoxiong Li(李邵雄), Wen Zheng(郑文), and Yang Yu(于扬) Chin. Phys. B, 2024, 33 (11):  110306.  DOI: 10.1088/1674-1056/ad73b3 Abstract ( 40 )   PDF (1093KB) ( 52 )   Performance of a scalable quantum processor critically relies on minimizing crosstalk and unwanted interactions within the system, as it is vital for parallel controlled operations on qubits. We present a protocol not only to provide information about residual coupling but also to effectively discriminate it from the influence of classical crosstalk. Our approach utilizes out-of-time-order correlators (OTOCs) as a signal of quantum crosstalk, making it applicable to various coupling forms and scalable architectures. To demonstrate the effectiveness of our protocol, we provide a theoretical analysis and simulate its implementation in coupled superconducting qubits.

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Generalized Einstein-Podolsky-Rosen steering paradox Zhi-Jie Liu(刘志洁), Xing-Yan Fan(樊星言), Jie Zhou(周洁), Mi Xie(谢汨), and Jing-Ling Chen(陈景灵) Chin. Phys. B, 2024, 33 (11):  110307.  DOI: 10.1088/1674-1056/ad73b7 Abstract ( 38 )   PDF (487KB) ( 2 )   Quantum paradoxes are essential means to reveal the incompatibility between quantum and classical theories, among which the Einstein-Podolsky-Rosen (EPR) steering paradox offers a sharper criterion for the contradiction between local-hidden-state model and quantum mechanics than the usual inequality-based method. In this work, we present a generalized EPR steering paradox, which predicts a contradictory equality "$2_{\rm Q}=\left( 1+\delta\right) _{\rm C}$" ($0\leq\delta<1$) given by the quantum (Q) and classical (C) theories. For any $N$-qubit state in which the conditional state of the steered party is pure, we test the paradox through a two-setting steering protocol, and find that the state is steerable if some specific measurement requirements are satisfied. Moreover, our construction also enlightens the building of EPR steering inequality, which may contribute to some schemes for typical quantum teleportation and quantum key distributions.

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Entanglement polygon inequalities for a class of mixed states Xian Shi(石现) Chin. Phys. B, 2024, 33 (11):  110308.  DOI: 10.1088/1674-1056/ad8eb0 Abstract ( 19 )   PDF (499KB) ( 3 )   The study on the entanglement polygon inequality of multipartite systems has attracted much attention. However, most of the results are on pure states. Here we consider the property for a class of mixed states, which are the reduced density matrices of generalized $W$-class states in multipartite higher dimensional systems. First we show the class of mixed states satisfies the entanglement polygon inequalities in terms of Tsallis-$q$ entanglement, then we propose a class of tighter inequalities for mixed states in terms of Tsallis-$q$ entanglement. At last, we get an inequality for the mixed states, which can be regarded as a relation for bipartite entanglement.

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Dynamical analysis, control, boundedness, and prediction for a fractional-order financial risk system Kehao Yang(杨轲皓), Song Zheng(郑松), Tianhu Yu(余天虎), Aceng Sambas, Muhamad Deni Johansyah, Hassan Saberi-Nik, and Mohamad Afendee Mohamed Chin. Phys. B, 2024, 33 (11):  110501.  DOI: 10.1088/1674-1056/ad7afb Abstract ( 49 )   PDF (3051KB) ( 2 )   This paper delves into the dynamical analysis, chaos control, Mittag-Leffler boundedness (MLB), and forecasting a fractional-order financial risk (FOFR) system through an absolute function term. To this end, the FOFR system is first proposed, and the adomian decomposition method (ADM) is employed to resolve this fractional-order system. The stability of equilibrium points and the corresponding control schemes are assessed, and several classical tools such as Lyapunov exponents (LE), bifurcation diagrams, complexity analysis (CA), and 0-1 test are further extended to analyze the dynamical behaviors of FOFR. Then the global Mittag-Leffler attractive set (MLAS) and Mittag-Leffler positive invariant set (MLPIS) for the proposed financial risk (FR) system are discussed. Finally, a proficient reservoir-computing (RC) method is applied to forecast the temporal evolution of the complex dynamics for the proposed system, and some simulations are carried out to show the effectiveness and feasibility of the present scheme.

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Impacts of bus holding strategy on the performance and pollutant emissions of a two-lane mixed traffic system Yanfeng Qiao(乔延峰), Ronghan Yao(姚荣涵), Baofeng Pan(潘宝峰), and Yu Xue(薛郁) Chin. Phys. B, 2024, 33 (11):  110502.  DOI: 10.1088/1674-1056/ad7e98 Abstract ( 46 )   PDF (4659KB) ( 2 )   This paper investigates the impacts of a bus holding strategy on the mutual interference between buses and passenger cars in a non-dedicated bus route, as well as the impacts on the characteristics of pollutant emissions of passenger cars. The dynamic behaviors of these two types of vehicles are described using cellular automata (CA) models under open boundary conditions. Numerical simulations are carried out to obtain the phase diagrams of the bus system and the trajectories of buses and passenger cars before and after the implementation of the bus holding strategy under different probabilities of passenger cars entering a two-lane mixed traffic system. Then, we analyze the flow rate, satisfaction rate, and pollutant emission rates of passenger cars together with the performance of a mixed traffic system. The results show that the bus holding strategy can effectively alleviate bus bunching, whereas it has no significant impact on the flow rate and pollutant emission rates of passenger cars; the flow rate, satisfaction rate, and pollutant emission rates of passenger cars for either the traffic system or for each lane are influenced by the bus departure interval and the number of passengers arriving at bus stops.

ATOMIC AND MOLECULAR PHYSICS

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Microwave field sensor based on cold cesium Rydberg three-photon electromagnetically induced spectroscopy Yuan-Yuan Wu(吴圆圆), Yun-Hui He(何云辉), Yue-Chun Jiao(焦月春), and Jian-Ming Zhao(赵建明) Chin. Phys. B, 2024, 33 (11):  113201.  DOI: 10.1088/1674-1056/ad7579 Abstract ( 52 )   PDF (1051KB) ( 16 )   We present the electromagnetically induced transparency (EIT) spectra of cold Rydberg four-level cascade atoms consisting of the $6{\rm S}_{1/2} \to 6{\rm P}_{3/2} \to 7{\rm S}_{1/2} \to 60{\rm P}_{3/2}$ scheme. A coupling laser drives the Rydberg transition, a dressing laser couples two intermediate levels and a weak probe laser probes the EIT signal. We numerically solve the Bloch equations and investigate the dependence of the probe transmission rate signal on the coupling and dressing lasers. We find that the probe transmission rate can display an EIT or electromagnetically induced absorption (EIA) profile, depending on the Rabi frequencies of the coupling and dressing lasers. When we increase the Rabi frequency of the coupling laser and keep the Rabi frequency of the probe and dressing laser fixed, flipping of the EIA to EIT spectrum occurs at the critical coupling Rabi frequency. When we apply a microwave field coupling the transition 60${\rm P}_{3/2} \to 61{\rm S}_{1/2}$, the EIT spectrum shows Autler-Townes splitting, which is employed to measure the microwave field. The theoretical measurement sensitivity can be 1.52$\times10^{-2}$ nV$\cdot$cm$^{-1}\cdot$Hz$^{-1/2}$ at the EIA-EIT flipping point.

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Theoretical study of differential cross sections for the ionization of helium by fast proton impact M Mondal, B Mandal, T Mistry, D Jana, and M Purkait Chin. Phys. B, 2024, 33 (11):  113401.  DOI: 10.1088/1674-1056/ad74e6 Abstract ( 52 )   PDF (2332KB) ( 6 )   We present the angular distribution of the ejected electron for single ionization of He by fast proton impact. A four-body formalism of the three-Coulomb wave is applied to calculate the triple differential cross sections at several impact energies in the scattering, perpendicular and azimuthal planes. Moreover, the three-body formalism of three-Coulomb, two-Coulomb and first Born approximation models has also been used to study the many-body effect on electron emission and the validity of the models. In the three-Coulomb wave model, the final state wave function incorporates distortion due to the three-body mutual Coulombic interaction. In this formalism, we use an uncorrelated and correlated Born initial state, which consists of a plane wave for the incoming projectile times a two-electron bound state wavefunction of the helium atom representing the 1s${^2}(^{1}$S) state. But, in the case of the three-body formalism, the initial state wavefunction consists of a long-range Coulomb distortion for the incoming projectile and one active electron of the He atom described by the Roothaan-Hartree-Fock wavefunction. The structure with a single or two peaks with unequal intensity is observed in the angular distributions of the triple differential cross sections for the different kinematic conditions. In addition, the influence of static electron correlations is investigated using different bound state wavefunctions for the ground state of the He target. In the four-body formalism, the present computations are very fast by reducing a nine-dimensional integral to a two-dimensional real integral. Despite the simplicity and speed of the proposed quadrature, the comparison shows that the obtained results are in reasonable agreement with the experiment and are compatible with those of other theories.

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Secondary electron yield of air-exposed ALD-Al2O3 coating on Ag-plated aluminum alloy Xue-Man Wan(万雪曼), Tian-Cun Hu(胡天存), Jing Yang(杨晶), Na Zhang(张娜), Yun He(何鋆), and Wan-Zhao Cui(崔万照) Chin. Phys. B, 2024, 33 (11):  113701.  DOI: 10.1088/1674-1056/ad71b3 Abstract ( 50 )   PDF (1320KB) ( 15 )   Secondary electron yield (SEY) of air-exposed metals tends to be increased because of air-formed oxide, hydrocarbon, and other contaminants. This enhances the possibility of secondary electron multipacting in high-power microwave systems, resulting in undesirable occurrence of discharge damage. Al$_{2}$O$_{3}$ coatings have been utilized as passive and protective layers on device packages to provide good environmental stability. We employed atomic layer deposition (ALD) to produce a series of uniform Al$_{2}$O$_{3}$ coatings with appropriate thickness on Ag-plated aluminum alloy. The secondary electron emission characteristics and their variations during air exposure were observed. The escape depth of secondary electron needs to exceed the coating thickness to some extent in order to demonstrate SEY of metallic substrates. Based on experimental and calculated results, the maximum SEY of Ag-plated aluminum alloy had been maintained at 2.45 over 90 days of exposure without obvious degradation by applying 1 nm Al$_{2}$O$_{3}$ coatings. In comparison, the peak SEY of untreated Ag-plated aluminum alloy grew from an initial 2.33 to 2.53, exceeding that of the 1 nm Al$_{2}$O$_{3}$ sample. The ultra-thin ALD-Al$_{2}$O$_{3}$ coating substantially enhanced the SEY stability of metal materials, with good implications for the environmental dependability of spacecraft microwave components.

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Zeeman decoherence effect of trapped 199Hg+ ion Ramsey spectra Ge Liu(刘格), Hao Liu(柳浩), Yihe Chen(陈义和), Jian Wang(王健), Shuhong Huang(黄书泓), Chengbin Li(李承斌), and Lei She(佘磊) Chin. Phys. B, 2024, 33 (11):  113702.  DOI: 10.1088/1674-1056/ad7af6 Abstract ( 36 )   PDF (657KB) ( 3 )   In the $^{199}$Hg$^{+}$ ion microwave clock, the Zeeman decoherence effect caused by the overlapping of Zeeman sidebands and the radial secular motion sidebands will decrease the contrast of the Ramsey fringe, thus reducing the signal-to-noise ratio of the spectra. In this paper, the Zeeman decoherence effect is analyzed theoretically and investigated experimentally. A simplified model is built to describe the Ramsey spectral probability, in which the transverse relaxation time $T_{{2}}$ is introduced to characterize the influence of the Zeeman decoherence effect phenomenologically. The experiments were carried out on a linear quadrupole trap $^{199}$Hg$^{+}$ ion clock. The results show that the probability model matches well with the experimental data, and the magnetic field value should be more than 150 mGs (1 Gs = 10$^{-4}$ T) to avoid the Zeeman decoherence effect.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Computational temporal ghost imaging based on complementary modulation Jia-Wei Li(李佳炜), Wei Zhang(张伟), Xue-Feng Liu(刘雪峰), and Xu-Ri Yao(姚旭日) Chin. Phys. B, 2024, 33 (11):  114201.  DOI: 10.1088/1674-1056/ad74e8 Abstract ( 32 )   PDF (2704KB) ( 3 )   We report an experimental demonstration of temporal ghost imaging in which a digital micromirror device (DMD) and +1/-1 binary modulation have been combined to give an accurate reconstruction of a nonperiodic time object. Compared to the $0/1$ modulation, the reconstruction signal can be improved greatly by +1/-1 binary modulation even with half of the measurements. Experimental results show that 0/1 binary temporal objects up to 4 kHz and sinusoidal time objects up to 1 kHz can be reconstructed by this method. The influences of modulation speed and array detector gray levels are also discussed.

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Manganese dioxide as wide adaptive ultrafast photonic device for pulsed laser generation Xin-He Dou(窦鑫河), Zhen Chen(陈震), Chen-Yan Zhang(张辰妍), Xiang Li(李响), Fei-Hong Qiao(乔飞鸿), Bo-Le Song(宋博乐), Shan Wang(王珊), Hao Teng(滕浩), and Zhi-Guo Lv(吕志国) Chin. Phys. B, 2024, 33 (11):  114202.  DOI: 10.1088/1674-1056/ad71b5 Abstract ( 49 )   PDF (1281KB) ( 11 )   Research on novel ultrafast photonic devices with wide adaptability has become important scientific technical means to realize both scheme innovation and performance breakthrough in fiber laser generation. As types of transition metal oxide, manganese dioxide (MnO$_{2}$) materials exhibit remarkable properties including high photothermal stability, strong oxidation resistance, and excellent optical properties, making them promising candidate for utilization as modulation devices in nonlinear optics and ultrafast optics fields. We investigate the impact of MnO$_{2}$-based saturable absorber (SA) on the pulse characteristics. The experiment reveals that MnO$_{2}$-based SA supports effectively pulsed laser generation in wide pump power range and large dispersion parameter space with signal-to-noise ratio more than 85 dB. As far as we know, the pump power response range is outstanding among the most of the reported pulsed lasers, which is attributed to the large modulation depth of MnO$_{2}$ SA. We also investigate the impact of dispersion on the characteristics of laser output, which is not involved in other similar works. This research indicates that MnO$_{2}$ as a photonic device has vast potential in advanced ultrafast optics.

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Rapid hologram generation through backward ray tracing and adaptive-resolution wavefront recording plane Jianying Zhu(朱建英), Yong Bi(毕勇), Minyuan Sun(孙敏远), and Weinan Gao(高伟男) Chin. Phys. B, 2024, 33 (11):  114204.  DOI: 10.1088/1674-1056/ad7c2e Abstract ( 34 )   PDF (989KB) ( 3 )   An advanced method for rapidly computing holograms of large three-dimensional (3D) objects combines backward ray tracing with adaptive resolution wavefront recording plane (WRP) and adaptive angular spectrum propagation. In the initial phase, a WRP with adjustable resolution and sampling interval based on the object's size is defined to capture detailed information from large 3D objects. The second phase employs an adaptive angular spectrum method (ASM) to efficiently compute the propagation from the large-sized WRP to the small-sized computer-generated hologram (CGH). The computation process is accelerated using CUDA and OptiX. Optical experiments confirm that the algorithm can generate high-quality holograms with shadow and occlusion effects at a resolution of 1024×1024 in 29 ms.

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An analogical study of wave equations, physical quantities, conservation and reciprocity equations between electromagnetic and elastic waves Yuchen Zang(臧雨宸) Chin. Phys. B, 2024, 33 (11):  114301.  DOI: 10.1088/1674-1056/ad7724 Abstract ( 47 )   PDF (594KB) ( 14 )   This paper presents an analogical study between electromagnetic and elastic wave fields, with a one-to-one correspondence principle established regarding the basic wave equations, the physical quantities and the differential operations. Using the electromagnetic-to-elastic substitution, the analogous relations of the conservation laws of energy and momentum are investigated between these two physical fields. Moreover, the energy-based and momentum-based reciprocity theorems for an elastic wave are also derived in the time-harmonic state, which describe the interaction between two elastic wave systems from the perspectives of energy and momentum, respectively. The theoretical results obtained in this analysis can not only improve our understanding of the similarities of these two linear systems, but also find potential applications in relevant fields such as medical imaging, non-destructive evaluation, acoustic microscopy, seismology and exploratory geophysics.

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Relationship between self-propelled velocity and Brownian motion for spherical and ellipsoid particles Jingwen Wang(汪静文), Ming Xu(徐明), and Deming Nie(聂德明) Chin. Phys. B, 2024, 33 (11):  114601.  DOI: 10.1088/1674-1056/ad7727 Abstract ( 56 )   PDF (1378KB) ( 12 )   The Brownian motion of spherical and ellipsoidal self-propelled particles was simulated without considering the effect of inertia and using the Langevin equation and the diffusion coefficient of ellipsoidal particles derived by Perrin. The Péclet number (Pe) was introduced to measure the relative strengths of self-propelled and Brownian motions. We found that the motion state of spherical and ellipsoid self-propelled particles changed significantly under the influence of Brownian motion. For spherical particles, there were three primary states of motion: 1) when $Pe< 30$, the particles were still significantly affected by Brownian motion; 2) when $Pe> 30$, the self-propelled velocities of the particles were increasing; and 3) when $Pe> 100$, the particles were completely controlled by the self-propelled velocities and the Brownian motion was suppressed. In the simulation of the ellipsoidal self-propelled particles, we found that the larger the aspect ratio of the particles, the more susceptible they were to the influence of Brownian motion. In addition, the value interval of $Pe$ depended on the aspect ratio. Finally, we found that the directional motion ability of the ellipsoidal self-propelled particles was much weaker than that of the spherical self-propelled particles.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Comparative study of boron and neon injections on divertor heat fluxes using SOLPS-ITER simulations Lei Peng(彭磊), Zhen Sun(孙震), Ji-Zhong Sun(孙继忠), Rajesh Maingi, Fang Gao(高放), Xavier Bonnin, Hua-Yi Chang(常华溢), Wei-Kang Wang(汪炜康), and Jin-Yuan Liu(刘金远) Chin. Phys. B, 2024, 33 (11):  115201.  DOI: 10.1088/1674-1056/ad711e Abstract ( 54 )   PDF (1930KB) ( 6 )   Based on the EAST equilibrium, the effects of boron (B) and neon (Ne) injected at different locations on the target heat load, and the distributions of B and Ne particles were investigated by transport code SOLPS-ITER. It was found that the B injection was more sensitive to the injection location for heat flux control than impurity Ne. The high electron and ion densities near the inner target in the discharge with impurity B injected from over $X$-point ($R_{1}$) led to plasma detachment only at the inner target, and the localized B ions in the cases with injection from outer target location ($R_{2}$) and upstream location ($R_{3}$) led to far-SOL detachment at the outer target, but not at the inner target. In contrast, for Ne, the spatial distributions of Ne ions and electrons were found to be similar in all the cases at the three injection locations, and the detached plasma was achieved at the inner target and the electron temperature was reduced at the outer target. For locations $R_{2}$ and $R_{3}$, impurity B showed a more pronounced effect on the heat flux at the far-SOL of the outer target. Further analysis indicated that Ne atoms came mainly from the recycling sources, whereas B atoms came mainly from injection, and that their distinct atomic distributions resulted from the difference in the ionization threshold and ionization mean free path. In addition, the radiation proportion of B in the divertor region was larger than that of Ne when the total radiation power was similar, which suggests that B has less influence on the core region.

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A model for fast electron-driven high-density plasma in the double-cone ignition scheme Zhong-Yi Chen(陈忠义), Kai-Ge Zhao(赵凯歌), and Ying-Jun Li(李英骏) Chin. Phys. B, 2024, 33 (11):  115202.  DOI: 10.1088/1674-1056/ad71b8 Abstract ( 46 )   PDF (1044KB) ( 9 )   A model for fast electron-driven high-density plasma is proposed to describe the effect of injected fast electrons on the temperature and inner pressure of the plasma in the fast heating process of the double-cone ignition (DCI) scheme. Due to the collision of the two low-density plasmas, the density and volume of the high-density plasma vary. Therefore, the ignition temperature and energy requirement of the high-density plasma vary at different moments, and the required energy for hot electrons to heat the plasma also changes. In practical experiments, the energy input of hot electrons needs to be considered. To reduce the energy input of hot electrons, the optimal moment and the shortest time for injecting hot electrons with minimum energy are analyzed. In this paper, it is proposed to inject hot electrons for a short time to heat the high-density plasma to a relatively high temperature. Then, the alpha particles with the high heating rate and PdV work heat the plasma to the ignition temperature, further reducing the energy required to inject hot electrons. The study of the injection time of fast electrons can reduce the energy requirement of fast electrons for the high-density plasma and increase the probability of successful ignition of the high-density plasma.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Valence electron structures dependences of structural stability and properties of REX3(RE=rare earth; X=In, Tl) and RE(In, Co)3 alloys Boyang Li(李博洋), Yongquan Guo(郭永权), Yi-Chen Feng(冯奕晨), Xinze Wang(王鑫泽), and Wei Liu(刘葳) Chin. Phys. B, 2024, 33 (11):  116102.  DOI: 10.1088/1674-1056/ad7575 Abstract ( 36 )   PDF (820KB) ( 3 )   Intermetallic compounds $RE$In$_{3}$ ($RE={\rm rare}$ earth) have attracted much attention due to their unique characteristics: crystal field effect, Kondo effect, superconductivity, heavy fermion, and antiferromagnetism, and their cobalt diluted alloys exhibit the ferromagnetic half-metallic characteristics at room temperature. In this study, an empirical electron theory (EET) is employed to investigate systemically the valence electronic structure, the thermal and magnetic properties of $REX_{3}$ and their cobalt diluted alloys for revealing the mechanism of physical properties. The calculated bond length, melting point, and magnetic moment match the experimental ones very well. The study reveals that structural stability and physical properties of $REX_{3}$ and their cobalt dilute alloys are strongly related to their valence electron structures. It is suggested that the structural stability and cohesive energy depend upon the covalent electron, the melting point is modulated by covalent electron pair, and the magnetic moment is originated from 3d magnetic electron. The ferromagnetic characteristics of Co-diluted $RE$In$_{3}$ alloys is originated from the introduction of strong ferromagnetic Co atom, but, a competition is caused between the electron transition from valence electron to magnetic electron on d orbit and its reversal electron transformation with increasing the content of cobalt, which results in the formations of diluted magnetic Gd(In,Co)$_{3}$ alloy with minor amount of cobalt and strong magnetic Nd(In,Co)$_{3}$ alloy with doping more Co atoms.

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Effect of Mn element on shock response in CoCrFeNiMnx high entropy alloys Peng Wen(闻鹏), Changxing Du(杜长星), Gang Tao(陶钢), and Guipeng Ding(丁贵鹏) Chin. Phys. B, 2024, 33 (11):  116103.  DOI: 10.1088/1674-1056/ad7fd0 Abstract ( 28 )   PDF (3584KB) ( 4 )   The effect of Mn element on shock response of CoCrFeNiMn$_{x}$ high entropy alloys (HEAs) are investigated using molecular dynamics simulations. Structural analysis shows that Mn-rich CoCrFeNiMn$_{x}$ HEA has a larger average atomic volume. The elastic properties of CoCrFeNiMn$_{x}$ HEAs under various hydrostatic pressures are studied, revealing that the elastic modulus decreases with increasing of Mn content. The shock thermodynamic parameters are quantitatively analyzed. The Mn-dependent shock Hugoniot relationship of CoCrFeNiMn$_{x}$ HEAs is obtained: $ U_{\rm s} = 1.25 + (5.21$-0.011$x)U_{\rm p}$. At relatively high shock pressure, the increase in Mn content promotes the formation of clustered BCC structures and hinders the development of dislocations. In addition, more FCC structures in Mn-rich CoCrFeNiMn$_{x}$ HEAs transform into disordered structures during spallation. Spall strength decreases with increasing Mn content. This study can provide a reference for the design and application of CoCrFeNiMn HEAs under shock loading.

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A molecular dynamics study on mechanical performance and deformation mechanisms in nanotwinned NiCo-based alloys with nano-precipitates under high temperatures Zihao Yu(于子皓), Hongyu Wang(王鸿宇), Ligang Sun(孙李刚), Zhihui Li(李志辉), and Linli Zhu(朱林利) Chin. Phys. B, 2024, 33 (11):  116201.  DOI: 10.1088/1674-1056/ad6cca Abstract ( 56 )   PDF (1133KB) ( 9 )   Molecular dynamics simulations are performed to investigate the mechanical behavior of nanotwinned NiCo-based alloys containing coherent L1$_{2}$ nano-precipitates at different temperatures, as well as the interactions between the dislocations and nano-precipitates within the nanotwins. The simulation results demonstrate that both the yield stress and flow stress in the nanotwinned NiCo-based alloys with nano-precipitates decrease as the temperature rises, because the higher temperatures lead to the generation of more defects during yielding and lower dislocation density during plastic deformation. Moreover, the coherent L1$_{2}$ phase exhibits excellent thermal stability, which enables the hinderance of dislocation motion at elevated temperatures via the wrapping and cutting mechanisms of dislocations. The synergistic effect of nanotwins and nano-precipitates results in more significant strengthening behavior in the nanotwinned NiCo-based alloys under high temperatures. In addition, the high-temperature mechanical behavior of nanotwinned NiCo-based alloys with nano-precipitates is sensitive to the size and volume fraction of the microstructures. These findings could be helpful for the design of nanotwins and nano-precipitates to improve the high-temperature mechanical properties of NiCo-based alloys.

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A novel MgHe compound under high pressure Jurong Zhang(张车荣), Lebin Chang(常乐斌), Suchen Ji(纪苏宸), Lanci Guo(郭兰慈), and Yuhao Fu(付钰豪) Chin. Phys. B, 2024, 33 (11):  116202.  DOI: 10.1088/1674-1056/ad77b5 Abstract ( 49 )   PDF (896KB) ( 5 )   Helium, with a full-shell electronic structure, is the most inert element in the periodic table at atmospheric pressure. The study of the reaction between helium and other non-noble-gas elements as well as relevant compounds has attracted great attention in the fields of chemistry, physics, materials and planetary science. In this study, we found a stable compound of MgHe with $P$6$_{3}/{mmc}$ symmetry at pressures above 795 GPa within zero-point energy. Thermodynamic stability calculations of $P$6$_{3}/mmc$ phase at high temperatures and pressures indicate that this structure may exist in the interior of the super-Earth and Neptune. Our further simulations on the electron localization function and Bader analysis show that the predicted compound is an electride with $-1.093e$ in the quantized interstitial quasiatom (ISQ) orbitals, which are localized at interstitial sites in the crystal lattice. Our study provides a theoretical basis for studying the physical and chemical properties of MgHe and the existence of MgHe in gaseous planets.

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The hcp-bcc transition of Be via anisotropy of modulus and sound velocity Zhen Yang(杨真), Jia-Wei Xian(咸家伟), Xing-Yu Gao(高兴誉), Fu-Yang Tian(田付阳), and Hai-Feng Song(宋海峰) Chin. Phys. B, 2024, 33 (11):  116401.  DOI: 10.1088/1674-1056/ad73b0 Abstract ( 68 )   PDF (3632KB) ( 21 )   Based on ab initio calculations, we utilize the mean-field potential approach with the quantum modification in conjunction with stress-strain relation to investigate the elastic anisotropies and sound velocities of hcp and bcc Be under high-temperature (0-6000 K) and high-pressure (0-500 GPa) conditions. We propose a general definition of anisotropy for elastic moduli and sound velocities. Results suggest that the elastic anisotropy of Be is more significantly influenced by pressure than by temperature. The pressure-induced increase of $c/a$ ratio makes the anisotropy of hcp Be significantly strengthen. Nevertheless, the hcp Be still exhibits smaller anisotropy than bcc Be in terms of elastic moduli and sound velocities. We suggest that measuring the anisotropy in shear sound velocity may be an approach to distinguishing the hcp-bcc phase transition under extreme conditions.

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“Glass-quake” in elastically loaded bulk metallic glasses Qi Huang(黄琦), Kaiguo Chen(陈开果), Chen Liu(刘辰), Guisen Liu(刘桂森), Yang Shao(邵洋), Chenlong Zhao(赵晨龙), Ran Chen(陈然), Hengtong Bu(卜亨通), Lingti Kong(孔令体), and Yao Shen(沈耀) Chin. Phys. B, 2024, 33 (11):  116402.  DOI: 10.1088/1674-1056/ad7725 Abstract ( 55 )   PDF (621KB) ( 5 )   Amorphous solids exhibit scale-free avalanches, even under small external loading, and thus can work as suitable systems to study critical behavior and universality classes. The abundance of scale-free avalanches in the entire elastic tension regime of bulk metallic glass (BMG) samples has been experimentally observed using acoustic emission (AE) measurements. In this work, we compare the statistics of avalanches with those of earthquakes, and find that they both follow the Gutenberg-Richter law in the statistics of energies and Omori's law of aftershock rates, and share the same characteristics in the distribution of recurrence times. These resemblances encourage us to propose the term "glass-quake" to describe avalanches in elastically loaded BMGs. Furthermore, our work echoes the potential universality of critical behavior in disordered physical systems from atomic to planetary scales, and motivates the use of elastic loaded BMGs as valuable laboratory simulators of seismic dynamics.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Valley switch effect in an α-T3 lattice-based superconducting interferometer Ya-Jun Wei(魏亚军) and Jun Wang(汪军) Chin. Phys. B, 2024, 33 (11):  117201.  DOI: 10.1088/1674-1056/ad6f91 Abstract ( 44 )   PDF (2355KB) ( 5 )   Dirac electrons possess a valley degree of freedom, which is currently under investigation as a potential information carrier. We propose an approach to generate and manipulate the valley-switching current (VSC) through Andreev reflection using an interferometer-based superconductor hybrid junction. The interferometer comprises a ring-shaped structure formed by topological kink states in the $\alpha$-T$_3$ lattice via carefully designed electrostatic potentials. Our results demonstrate the feasibility of achieving a fully polarized VSC in this device without contamination from cotunneling electrons sharing the same valley as the incident electron. Furthermore, we show that control over the fully polarized VSC can be achieved by applying a nonlocal gate voltage or modifying the global parameter $\alpha$. The former alters the dynamic phase of electrons while the latter provides an $\alpha$-dependent Berry phase, both directly influencing quantum interference and thereby affecting performance in terms of generating and manipulating VSC, crucial for advancements in valleytronics.

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Nonvolatile ferroelectric control of electronic properties of Bi2Te3 Xusheng Ding(丁旭升), Yunfei Li(李云飞), Chaoyang Kang(康朝阳), Ye-Heng Song(宋业恒), and Weifeng Zhang(张伟风) Chin. Phys. B, 2024, 33 (11):  117301.  DOI: 10.1088/1674-1056/ad7670 Abstract ( 52 )   PDF (784KB) ( 6 )   Nonvolatile electric-field control of the unique physical characteristics of topological insulators (TIs) is essential for the fundamental research and development of practical electronic devices. Electrically tunable transport properties through gating materials have been extensively investigated. However, the relatively weak and volatile tunability limits its practical applications in spintronics. Here, we demonstrate the nonvolatile electric-field control of Bi$_{2}$Te$_{3}$ transport properties via constructing ferroelectric Rashba architectures, i.e., 2D Bi$_{2}$Te$_{3}/\alpha $-In$_{2}$Se$_{3}$ ferroelectric field-effect transistors. By switching the polarization states of $\alpha $-In$_{2}$Se$_{3}$, the Fermi level, resistance, Fermi wave vector, carrier mobility, carrier density and magnetoresistance (MR) of the Bi$_{2}$Te$_{3}$ film can be effectively modulated. Importantly, a shift of the Fermi level towards a band gap with a surface state occurs as switching to a negative polarization state, the contribution of the surface state to the conductivity then increases, thereby increasing the carrier mobility and electron coherence length significantly, resulting in the enhanced weak anti-localization (WAL) effect. These results provide a nonvolatile electric-field control method to tune the electronic properties of TI and can further extend to quantum transport properties.

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Pseudospin-filter tunneling of massless Dirac fermions Zhengdong Li(李政栋) and Wen Zeng(曾文) Chin. Phys. B, 2024, 33 (11):  117401.  DOI: 10.1088/1674-1056/ad78d9 Abstract ( 44 )   PDF (579KB) ( 1 )   The tunneling of the massless Dirac fermions through a vector potential barrier are theoretically investigated, where the vector potential can be introduced by very high and very thin ($\delta$-function) magnetic potential barriers. We show that, distinct from the previously studied electric barrier tunneling, the vector potential barriers are more transparent for pseudospin-1/2 Dirac fermions but more obstructive for pseudospin-1 Dirac fermions. By tuning the height of the vector potential barrier, the pseudospin-1/2 Dirac fermions remain transmitted, whereas the transmission of the pseudospin-$1$ Dirac fermions is forbidden, leading to a pseudospin filtering effect for massless Dirac fermions.

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Dynamic properties of the magnetic skyrmion driven by electromagnetic waves with spin angular momentum and orbital angular momentum Longfei Guo(郭龙飞), Bing Zha(查兵), Xiaoqiao Sun(孙晓乔), Songmei Ni(倪松梅), Ruiyu Huang(黄瑞玉), Lin Chen(陈琳), and Zhikuo Tao(陶志阔) Chin. Phys. B, 2024, 33 (11):  117501.  DOI: 10.1088/1674-1056/ad7577 Abstract ( 50 )   PDF (5107KB) ( 36 )   We theoretically studied the dynamic properties of the skyrmion driven by electromagnetic (EM) waves with spin angular momentum (SAM) and orbital angular momentum (OAM) using micromagnetic simulations. First, the guiding centers of the skyrmion driven by EM waves with SAM, i.e., left-handed and right-handed circularly polarized EM waves, present circular trajectories, while present elliptical trajectories under linear EM waves driving due to the superposition of oppositely polarized wave components. Second, the trajectories of the skyrmion driven by EM waves with OAM demonstrate similar behavior to that driven by linearly polarized EM waves. Because the wave vector intensity varies with the phase for both linearly polarized EM waves and EM waves with OAM, the angular momentum is transferred to the skyrmion non-uniformly, while the angular momentum is transferred to the skyrmion uniformly for left-handed and right-handed circularly polarized EM driving. Third, the dynamic properties of the skyrmion driven by EM waves with both SAM and OAM are investigated. It is found that the dynamic trajectories exhibit more complex behavior due to the contributions or competition of SAM and OAM. We investigate the characteristics of intrinsic gyration modes and frequency-dependent trajectories. Our research may provide insight into the dynamic properties of skyrmion manipulated by EM waves with SAM or OAM and provide a method for controlling skyrmion in spintronic devices.

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Magnetocaloric properties of Nd-doped Gd5Si4 microparticles and nanopowders Kaiyang Zhang(张凯扬), Huanhuan Wang(王欢欢), Ying Wang(王颖), and Tao Wang(王涛) Chin. Phys. B, 2024, 33 (11):  117502.  DOI: 10.1088/1674-1056/ad6de7 Abstract ( 47 )   PDF (3585KB) ( 5 )   The preparation of materials with enhanced magnetocaloric properties is crucial for magnetic refrigeration. In this study, Nd-doped Gd$_{5}$Si$_{4}$ microparticles and nanomaterials were synthesized using the reduction-diffusion method. The impact of Nd doping with varying compositions on the structure and entropy change properties of the materials was investigated. The Curie temperatures of both the micron- and nano-sized materials ranged from 190 K to 210 K, which were lower than previously reported values. Micron-sized samples doped with 1% Nd exhibited superior magnetocaloric properties, demonstrating a maximum entropy change of 4.98 J$\cdot $kg$^{-1}\cdot $K$^{-1}$ at 5 T, with an entropy change exceeding 4 J$\cdot $kg$^{-1}\cdot $K$^{-1}$ over a wide temperature range of approximately 70 K. Conversely, the nanomaterials had broader entropy change peaks but lower values. All samples exhibited a second-order phase transition, as confirmed by the Arrott plots.

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Phase structure evolution and coercivity mechanism of high-Co containing permanent magnets Min Huang(黄敏), Yong Ding(丁勇), Zhihe Zhao(赵之赫), Chunguo Wang(王春国), Bo Zhou(周波), Lei Liu(刘雷), Yingli Sun(孙颖莉), and Aru Yan(闫阿儒) Chin. Phys. B, 2024, 33 (11):  117503.  DOI: 10.1088/1674-1056/ad6b82 Abstract ( 27 )   PDF (6217KB) ( 1 )   The phase structure and magnetic properties of high-Co containing permanent magnets with high thermal stability have been systematically studied in this work. It is abnormal that the coercivity of annealed samples was slightly lower than that of sintered samples, while the coercivity was usually enhanced after annealing in conventional Nd-Fe-B samples. Further analysis showed that in addition to RE$_{2}$(Fe,Co)$_{14}$B main phase and RE-rich grain boundary phase, there were also new Co-rich magnetic phases located in the grain boundary. During annealing, the phase structures of high-Co containing magnets were readjusted, especially the increasing Co-rich magnetic phase and emerging RE-rich particles precipitated from the main phase. Eventually, the isolated RE-rich particles would act as the pinning center of the domain wall movement in demagnetization process. It was confirmed that the coercivity of annealed high-Co containing magnets was controlled by both nucleation and pinning. Pinning mechanism can partially compensate for the weakening of magnetic isolation due to increased Co-rich magnetic phase, which explained the moderate decrease in coercivity of annealed high-Co containing magnets. The discovery of new coercivity mechanism contributed to in-depth understanding of high-Co containing magnets.

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Crystal growth, structure and crystal field splitting and fitting of Yb:GdScO3 Jia-Hong Li(李加红), Qing-Li Zhang(张庆礼), Gui-Hua Sun(孙贵花), Jin-Yun Gao(高进云), Ren-Qin Dou(窦仁勤), Xiao-Fei Wang(王小飞), and Shou-Jun Ding(丁守军) Chin. Phys. B, 2024, 33 (11):  117601.  DOI: 10.1088/1674-1056/ad72d3 Abstract ( 25 )   PDF (1366KB) ( 10 )   A good quality (5 at.% Yb:GdScO$_{3}$) single crystal of $\varPhi30 {\rm mm}\times 37$ mm was grown successfully by the Czochralski method. Its structure is studied by the x-ray diffraction (XRD), and its atomic coordinates are obtained by Rietveld refinement. The crystal field energy level splitting of Yb$^{3+}$ in GdScO$_{3}$ is determined by employing the absorption and photoluminescence spectra at 8 K. Only $^{2}$F$_{7/2}$(4) is far from the ground state $^{2}$F$_{7/2}$(1) by 710 cm$^{-1}$ among the crystal field energy levels split from $^{2}$F$_{7/2}$, so it is more easier to realize the laser operation of $^{2}$F$_{5/2}$(1)$\to^{2}$F$_{7/2}$(4) with wavelength 1060 nm. The spin-orbit coupling parameters and intrinsic crystal field parameters (CFPs). The intrinsic crystal field parameters $\bar{B}_{k}$ ($k=2$, 4, 6) of the crystal were fitted by the superposition model. The CFPs evaluated with $\bar{B}_{k}$ and coordination factor are taken as the initial parameters to fit the crystal field energy levels of the crystal, and the crystal field parameters ${B}^{k}_{q}$ are obtained finally with the root-mean-square deviation 9 cm$^{-1}$. It is suggested that the ligand point charge, covalency and overlap interaction are slightly weaker than charge interpenetration and coulomb exchange interaction for Yb$^{3+}$ in GdScO$_{3}$. The obtained Hamiltonian parameters can be used to calculate crystal field energy levels and wave functions of Yb:GdScO$_{3}$ to analyze the mechanism of the luminescence or laser.

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Relation of V/III ratio of AlN interlayer with the polarity of nitride Zhaole Su(苏兆乐), Yangfeng Li(李阳锋), Xiaotao Hu(胡小涛), Yimeng Song(宋祎萌), Zhen Deng(邓震), Ziguang Ma(马紫光), Chunhua Du(杜春花), Wenxin Wang(王文新), Haiqiang Jia(贾海强), Yang Jiang(江洋), and Hong Chen(陈弘) Chin. Phys. B, 2024, 33 (11):  117801.  DOI: 10.1088/1674-1056/ad71b2 Abstract ( 50 )   PDF (2204KB) ( 4 )   N-polar GaN film was obtained by using a high-temperature AlN buffer layer. It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temperature AlN layer. Continuing to increase the V/III ratio of the low-temperature AlN interlayer, the Ga-polarity of GaN film was inverted to N-polarity again but the crystal quality and surface roughness of GaN film greatly deteriorated. Finally, we analyzed the chemical environment of the AlN layer by x-ray photoelectron spectroscopy (XPS), which provides a new direction for the control of GaN polarity.

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Identifying the effect of photo-generated carriers on the phonons in rutile TiO2 through Raman spectroscopy Zheng Wang(王征), Min Liao(廖敏), Guihua Wang(王桂花), and Meng Zhang(张梦) Chin. Phys. B, 2024, 33 (11):  117802.  DOI: 10.1088/1674-1056/ad73b4 Abstract ( 44 )   PDF (4999KB) ( 6 )   Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials. Carriers can interact with lattices and influence lattice vibrations; thus, it is feasible to study the effect of photo-generated carriers on phonons by analyzing changes in the Raman spectra of semiconductors. Rutile is one of the predominant crystalline phases of TiO$_{2}$, which is a widely utilized metal oxide semiconductor. In this work, rutile TiO$_{2}$ is coated on a thinned optical fiber to concentrate ultraviolet light energy within the material, thereby enhancing the generation of carriers and amplifying the changes in the Raman spectra. A Raman detection laser with a wavelength of 532 nm is utilized to collect the Raman spectra of rutile TiO$_{2}$ during irradiation. Using this setup, the impact of photo-generated carriers on the phonons corresponding to Raman vibrational modes is researched. The localization and non-radiative recombination of photo-generated carriers contribute to a reduction in both the frequencies and lifetimes of phonons. This work provides a novel approach to researching the effect of carriers on phonons.

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Dancing bubble sonoluminescence in phosphoric acid solution Dexin Wang(王德鑫), Qinghim(清河美), Wurihan Bao(包乌日汗), Haiying Han(韩海英), and Naranmandula(那仁满都拉) Chin. Phys. B, 2024, 33 (11):  117803.  DOI: 10.1088/1674-1056/ad78dc Abstract ( 44 )   PDF (1882KB) ( 5 )   Sonoluminescence is more distinctly observed in phosphoric and sulfuric acid, which exhibit high viscosity and lower vapor pressures relative to water. Within an 85-wt% phosphoric acid solution saturated with argon (Ar), variations in the light-emitting regimes of bubbles were noted to correspond with increments in the driving acoustic intensity. Specifically, the bubbles were observed to perform a dance-like motion 2 cm below the multi-bubble sonoluminescence (MBSL) cluster, traversing a 25-mm$^2$ grid during the camera exposure period. Spectral analysis conducted at the beginning of the experiment showed a gradual attenuation of CN (B$^2\Sigma$-X$^2\Sigma$) emission concurrent with a strengthening of Ar (4p-4s) atom emission lines. The application of a theoretical temperature model to the spectral data revealed that the internal temperature of the bubbles escalates swiftly upon their implosion. This study is instrumental in advancing the comprehension of the underlying mechanisms of sonoluminescence and in the formulation of a dynamic model for the behavior of the bubbles.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Structural behavior and metallization of AsSbS3 at high pressure Tian Qin(覃天), Min Wu(武敏), Kai Wang(王凯), Ye Wu(吴也), and Haijun Huang(黄海军) Chin. Phys. B, 2024, 33 (11):  118101.  DOI: 10.1088/1674-1056/ad78d8 Abstract ( 39 )   PDF (1207KB) ( 2 )   The group V-VI semiconductor material getchellite (crystalline AsSbS$_{3})$ has garnered extensive attention due to its wonderful electronic and optical properties. The pressure engineering is one of the most effective methods to modulate crystal structure and physical properties of semiconductor materials. In this study, the structural behavior, optical and electrical properties of AsSbS$_{3}$ under high pressure have been investigated systematically by in situ high-pressure experiments for the first time. The monoclinic structure of AsSbS$_{3}$ remains stable up to 47.0 GPa without phase transition. The gradual lattice contraction with increasing pressure results in a continuous narrowing of the bandgap then leads to pressure-induced metallization of AsSbS$_{3}$ at 31.5 GPa. Our research presents a high-pressure strategy for tuning the crystal structure and physical properties of AsSbS$_{3}$ to expand its potential applications in electronic and optoelectronic fields.

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Unravelling biotoxicity of graphdiyne: Molecular dynamics simulation of the interaction between villin headpiece protein and graphdiyne Bei-Wei Zhang(张贝薇), Bing-Quan Zhang(张兵权), Zhi-Gang Shao(邵志刚), and Xianqiu Wu(吴先球) Chin. Phys. B, 2024, 33 (11):  118102.  DOI: 10.1088/1674-1056/ad7af5 Abstract ( 35 )   PDF (4072KB) ( 2 )   Recently, there has been a growing prevalence in the utilization of graphdiyne (GDY) in the field of biomedicine, attributed to its distinctive physical structure and chemical properties. Additionally, its biocompatibility has garnered increasing attention. However, there is a lack of research on the biological effects and physical mechanisms of GDY-protein interactions at the molecular scale. In this study, the villin headpiece subdomain (HP35) served as a representative protein model. Molecular dynamics simulations were employed to investigate the interaction process between the HP35 protein and GDY, as well as the structural evolution of the protein. The data presented in our study demonstrate that GDY can rapidly adsorb HP35 protein and induce denaturation to one of the $\alpha$-helix structures of HP35 protein. This implies a potential cytotoxicity concern of GDY for biological systems. Compared to graphene, GDY induced less disruption to HP35 protein. This can be attributed to the presence of natural triangular vacancies in GDY, which prevents $\pi$-$\pi$ stacking action and the limited interaction of GDY with HP35 protein is not conducive to the expansion of protein structures. These findings unveil the biological effects of GDY at the molecular level and provide valuable insights for the application of GDY in biomedicine.

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Relationship between polyhedral structures formed by tangent planes of ellipsoidal particles and system sound velocity Cheng-Bo Li(李成波), Lin Bao(鲍琳), and Chuang Zhao(赵闯) Chin. Phys. B, 2024, 33 (11):  118301.  DOI: 10.1088/1674-1056/ad7726 Abstract ( 34 )   PDF (3738KB) ( 7 )   Internal polyhedral structures of a granular system can be investigated using the Voronoi tessellations. This technique has gained increasing recognition in research of kinetic properties of granular flows. For systems with mono-sized spherical particles, Voronoi tessellations can be utilized, while radial Voronoi tessellations are necessary for analyzing systems with multi-sized spherical particles. However, research about polyhedral structures of non-spherical particle systems is limited. We utilize the discrete element method to simulate a system of ellipsoidal particles, defined by the equation $(\frac{x}{\alpha})^{2}+(\frac{y}{1})^{2}+(\frac{z}{1/\alpha})^{2}=1$, where $\alpha$ ranges from 1.1 to 2.0. The system is then dissected by using tangent planes at the contact points, and the geometric quantities of the resulting polyhedra in different shaped systems, such as surface area, volume, number of vertices, number of edges, and number of faces, are calculated. Meanwhile, the longitudinal and transverse wave velocities within the system are calculated with the time-of-flight method. The results demonstrate a strong correlation between the sound velocity of the system and the geometry of the dissected polyhedra. The sound velocity of the system increases with the increase in $\alpha$, peaking at $\alpha=1.3$, and then decreases as $\alpha$ continues to increase. The average volume, surface area, number of vertices, number of edges, and number of faces of the polyhedra decrease with the increase in sound velocity. That is, these quantities initially decrease with the increase in $\alpha$, reaching minima at $\alpha=1.3$, and then increase with further increase of $\alpha$. The relationship between sound velocity and the geometric quantities of the dissected polyhedra can serve as a reference for acoustic material design.

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Spatial electron-spin splitting in single-layered semiconductor microstructure modulated by Dresselhaus spin-orbit coupling Jia-Li Chen(陈嘉丽), Sai-Yan Chen(陈赛艳), Li Wen(温丽), Xue-Li Cao(曹雪丽), and Mao-Wang Lu(卢卯旺) Chin. Phys. B, 2024, 33 (11):  118501.  DOI: 10.1088/1674-1056/ad6b83 Abstract ( 35 )   PDF (969KB) ( 11 )   Combining theory and computation, we explore the Goos-Hänchen (GH) effect for electrons in a single-layered semiconductor microstructure (SLSM) modulated by Dresselhaus spin-orbit coupling (SOC). GH displacement depends on electron spins thanks to Dresselhaus SOC, therefore electron spins can be separated from the space domain and spin-polarized electrons in semiconductors can be realized. Both the magnitude and sign of the spin polarization ratio change with the electron energy, in-plane wave vector, strain engineering and semiconductor layer thickness. The spin polarization ratio approaches a maximum at resonance; however, no electron-spin polarization occurs in the SLSM for a zero in-plane wave vector. More importantly, the spin polarization ratio can be manipulated by strain engineering or semiconductor layer thickness, giving rise to a controllable spatial electron-spin splitter in the field of semiconductor spintronics.

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Topological slow light and rainbow trapping of surface wave in valley photonic crystal bounded by air Shuheng Chen(陈书恒), Yi Qi(齐奕), Yucen Li(李昱岑), Qihao Wang(王琪皓), and Yuanjiang Xiang(项元江) Chin. Phys. B, 2024, 33 (11):  118701.  DOI: 10.1088/1674-1056/ad7fd2 Abstract ( 27 )   PDF (4003KB) ( 2 )   Topological slow light and rainbow trapping tend to rely on large-scale interface structure in previous research work, which have restricted further miniaturization. In this work, we propose a method to realize slow light and rainbow trapping at the zigzag edge of a single valley photonic crystals (VPCs) bounded by air, which is very different from previous studies where rainbow trapping is supported at the interface separating two VPCs with inversion symmetry. By constructing the VPC-air boundaries and VPC-VPC interfaces experimentally, we have observed the topologically protected rainbow trapping simultaneously at the external and internal boundary. This work provides a feasible platform for the miniaturized optical communication devices such as optical buffers, optical storage and optical routing.

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Identify information sources with different start times in complex networks based on sparse observers Yuan-Zhang Deng(邓元璋), Zhao-Long Hu(胡兆龙), Feilong Lin(林飞龙), Chang-Bing Tang(唐长兵), Hui Wang(王晖), and Yi-Zhen Huang(黄宜真) Chin. Phys. B, 2024, 33 (11):  118901.  DOI: 10.1088/1674-1056/ad7af4 Abstract ( 29 )   PDF (2434KB) ( 3 )   The dissemination of information across various locations is an ubiquitous occurrence, however, prevalent methodologies for multi-source identification frequently overlook the fact that sources may initiate dissemination at distinct initial moments. Although there are many research results of multi-source identification, the challenge of locating sources with varying initiation times using a limited subset of observational nodes remains unresolved. In this study, we provide the backward spread tree theorem and source centrality theorem, and develop a backward spread centrality algorithm to identify all the information sources that trigger the spread at different start times. The proposed algorithm does not require prior knowledge of the number of sources, however, it can estimate both the initial spread moment and the spread duration. The core concept of this algorithm involves inferring suspected sources through source centrality theorem and locating the source from the suspected sources with linear programming. Extensive experiments from synthetic and real network simulation corroborate the superiority of our method in terms of both efficacy and efficiency. Furthermore, we find that our method maintains robustness irrespective of the number of sources and the average degree of network. Compared with classical and state-of-the art source identification methods, our method generally improves the AUROC value by 0.1 to 0.2.