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10 January 2023, Volume 32 Issue 2 Previous issue    Next issue

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DATA PAPER

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Atlas of dynamic spectra of fast radio burst FRB 20201124A Bo-Jun Wang(王铂钧), Heng Xu(胥恒), Jin-Chen Jiang(姜金辰), Jiang-Wei Xu(徐江伟), Jia-Rui Niu(牛佳瑞), Ping Chen(陈平), Ke-Jia Lee(李柯伽), Bing Zhang(张冰), Wei-Wei Zhu(朱炜玮), Su-Bo Dong(东苏勃), Chun-Feng Zhang(张春风), Hai Fu(傅海), De-Jiang Zhou(周德江), Yong-Kun Zhang(张永坤), Pei Wang(王培), Yi Feng(冯毅), Ye Li(李晔), Dong-Zi Li(李冬子), Wen-Bin Lu(鲁文宾), Yuan-Pei Yang(杨元培), R. N. Caballero, Ce Cai(蔡策), Mao-Zheng Chen(陈卯蒸), Zi-Gao Dai(戴子高), A. Esamdin(艾力·伊沙木丁), Heng-Qian Gan(甘恒谦), Jin-Lin Han(韩金林), Long-Fei Hao(郝龙飞), Yu-Xiang Huang(黄玉祥), Peng Jiang(姜鹏), Cheng-Kui Li(李承奎), Di Li(李菂), Hui Li(李辉), Xin-Qiao Li(李新乔), Zhi-Xuan Li(李志玄), Zhi-Yong Liu(刘志勇), Rui Luo(罗睿), Yun-Peng Men(门云鹏), Chen-Hui Niu(牛晨辉), Wen-Xi Peng(彭文溪), Lei Qian(钱磊), Li-Ming Song(宋黎明), Jing-Hai Sun(孙京海), Fa-Yin Wang(王发印), Min Wang(汪敏), Na Wang(王娜), Wei-Yang Wang(王维扬), Xue-Feng Wu(吴雪峰), Shuo Xiao(肖硕), Shao-Lin Xiong(熊少林), Yong-Hua Xu(徐永华), Ren-Xin Xu(徐仁新), Jun Yang(杨俊), Xuan Yang(杨轩), Rui Yao(姚蕊), Qi-Bin Yi(易祁彬), You-Ling Yue(岳友岭), Dong-Jun Yu(于东俊), Wen-Fei Yu(余文飞), Jian-Ping Yuan(袁建平), Bin-Bin Zhang(张彬彬), Song-Bo Zhang(张松波), Shuang-Nan Zhang(张双南), Yi Zhao(赵一), Wei-Kang Zheng(郑伟康), Yan Zhu(朱岩), and Jin-Hang Zou(邹金航) Chin. Phys. B, 2023, 32 (2):  029801.  DOI: 10.1088/1674-1056/aca7ed Abstract ( 403 )   HTML ( 10 )   PDF (1500KB) ( 276 )   Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio bursts,[1,2] of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076.

INSTRUMENTATION AND MEASUREMENT

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Measurement of T wave in magnetocardiography using tunnel magnetoresistance sensor Zhihong Lu(陆知宏), Shuai Ji(纪帅), and Jianzhong Yang(杨建中) Chin. Phys. B, 2023, 32 (2):  020703.  DOI: 10.1088/1674-1056/aca5fe Abstract ( 491 )   HTML ( 17 )   PDF (1865KB) ( 168 )   Several critical clinical applications of magnetocardiography (MCG) involve its T wave. The T wave's accuracy directly affects the diagnostic accuracy of MCG for ischemic heart disease and arrhythmogenic. Tunnel magnetoresistance (TMR) attracts attention as a new MCG measurement technique. However, the T waves measured by TMR are often drowned in noise. The accuracy of T waves needs to be discussed to determine the clinical value of MCG measured by TMR. This study uses an improved empirical mode decomposition (EMD) algorithm and averaging to eliminate the noise in the MCG measured by TMR. The MCG signals measured by TMR are compared with MCG measured by the optically pumped magnetometer (OPM) to judge its accuracy. Using the MCG measured by OPM as a reference, the relative errors in time and amplitude of the T wave measured by TMR are 3.4% and 1.8%, respectively. This is the first demonstration that TMR can accurately measure the time and amplitude of MCG T waves. The ability to provide reliable T wave data illustrates the significant clinical application value of TMR in MCG measurement.

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Direct measurement of an energy-dependent single-event-upset cross-section with time-of-flight method at CSNS Biao Pei(裴标), Zhixin Tan(谭志新), Yongning He(贺永宁), Xiaolong Zhao(赵小龙), and Ruirui Fan(樊瑞睿) Chin. Phys. B, 2023, 32 (2):  020705.  DOI: 10.1088/1674-1056/aca603 Abstract ( 422 )   HTML ( 2 )   PDF (2957KB) ( 153 )   To predict the soft error rate for applications, it is essential to study the energy dependence of the single-event-upset (SEU) cross-section. In this work, we present a direct measurement of the SEU cross-section with the Back-n white neutron source at the China Spallation Neutron Source. The measured cross section is consistent with the soft error data from the manufacturer and the result suggests that the threshold energy of the SEU is about 0.5 MeV, which confirms the statement in Iwashita's report that the threshold energy for neutron soft error is much below that of the (n, α) cross-section of silicon. In addition, an index of the effective neutron energy is suggested to characterize the similarity between a spallation neutron beam and the standard atmospheric neutron environment.

RAPID COMMUNICATION

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Estimation of far-field wavefront error of tilt-to-length distortion coupling in space-based gravitational wave detection Ya-Zheng Tao(陶雅正), Hong-Bo Jin(金洪波), and Yue-Liang Wu(吴岳良) Chin. Phys. B, 2023, 32 (2):  024212.  DOI: 10.1088/1674-1056/aca9c5 Abstract ( 376 )   HTML ( 4 )   PDF (1947KB) ( 153 )   In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials are used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between the distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show that the pointing jitter is strongly related to the wavefront error. Furthermore, when the jitter decreases 10 times from 100 nrad to 10 nrad, the wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to $Z$[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with the wavefront error of the received beam. When the aperture diameter increases at $Z$[5,3] Zernike, the wavefront error is not monotonic and has oscillation. Nevertheless, the wavefront error almost remains constant with the arm length increasing from 10$^{-1}$ Mkm to 10$^3$ Mkm. When the arm length decreases for three orders of magnitude from 10$^{-1}$ Mkm to 10$^{-4}$ Mkm, the wavefront error has only an order of magnitude increasing. In the range of 10$^{-4}$ Mkm to 10$^3$ Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm at $Z$[5,3] Zernike and 10 nrad jitter.

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Bismuth doping enhanced tunability of strain-controlled magnetic anisotropy in epitaxial Y3Fe5O12(111) films Hot! Yunpeng Jia(贾云鹏), Zhengguo Liang(梁正国), Haolin Pan(潘昊霖), Qing Wang(王庆), Qiming Lv(吕崎鸣), Yifei Yan(严轶非), Feng Jin(金锋), Dazhi Hou(侯达之), Lingfei Wang(王凌飞), and Wenbin Wu(吴文彬) Chin. Phys. B, 2023, 32 (2):  027501.  DOI: 10.1088/1674-1056/ac67cc Abstract ( 815 )   HTML ( 8 )   PDF (893KB) ( 540 )   Y3Fe5O12 (YIG) and BiY2Fe5O12 (Bi:YIG) films were epitaxially grown on a series of (111)-oriented garnet substrates using pulsed laser deposition. Structural and ferromagnetic resonance characterizations demonstrated the high epitaxial quality, extremely low magnetic loss and coherent strain state in these films. Using these epitaxial films as model systems, we systematically investigated the evolution of magnetic anisotropy (MA) with epitaxial strain and chemical doping. For both the YIG and Bi:YIG films, the compressive strain tends to align the magnetic moment in the film plane while the tensile strain can compete with the demagnetization effect and stabilize perpendicular MA. We found that the strain-induced lattice elongation/compression along the out-of-plane [111] axis is the key parameter that determines the MA. More importantly, the strain-induced tunability of MA can be enhanced significantly by Bi doping; meanwhile, the ultralow damping feature persists. We clarified that the cooperation between strain and chemical doping could realize an effective control of MA in garnet-type ferrites, which is essential for spintronic applications.

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Magnetic triangular bubble lattices in bismuth-doped yttrium iron garnet Hot! Tao Lin(蔺涛), Chengxiang Wang(王承祥), Zhiyong Qiu(邱志勇), Chao Chen(陈超), Tao Xing(邢弢), Lu Sun(孙璐), Jianhui Liang(梁建辉), Yizheng Wu(吴义政), Zhong Shi(时钟), and Na Lei(雷娜) Chin. Phys. B, 2023, 32 (2):  027505.  DOI: 10.1088/1674-1056/aca604 Abstract ( 582 )   HTML ( 13 )   PDF (2430KB) ( 419 )   Magnetic bubbles have again become a subject of significant attention following the experimental observation of topologically nontrivial magnetic skyrmions. In recent work, tailoring the shape of the bubbles is considered a key factor for their dynamics in spintronic devices. In addition to the reported circular, elliptical, and square bubbles, here we observe triangular bubble domains in bismuth-doped yttrium iron garnet (Bi-YIG) using Kerr microscopy. The bubble domains evolve from discrete circular to latticed triangular and hexagonal shapes. Further, the orientation of the triangular bubbles in the hexagonal lattices can be flipped by decreasing the magnetic field. The sixfold in-plane magnetic anisotropy of Bi-YIG(111) crystal, which is presumably the mechanism underlying the triangular shape of the bubbles, is measured as 1179 erg/cm3. The study of the morphologies of topologically trivial bubbles in YIG offers insight into nontrivial spin textures, which is appealing for future spintronic applications.

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Different roles of surfaces' interaction on lattice mismatched/matched surfaces in facilitating ice nucleation Hot! Xuanhao Fu(傅宣豪) and Xin Zhou(周昕) Chin. Phys. B, 2023, 32 (2):  028202.  DOI: 10.1088/1674-1056/aca202 Abstract ( 476 )   HTML ( 3 )   PDF (4059KB) ( 234 )   The freezing of water is one of the most common processes in nature and affects many aspects of human activity. Ice nucleation is a crucial part of the freezing process and usually occurs on material surfaces. There is still a lack of clear physical pictures about the central question how various features of material surfaces affect their capability in facilitating ice nucleation. Via molecular dynamics simulations, here we show that the detailed features of surfaces, such as atomic arrangements, lattice parameters, hydrophobicity, and function forms of surfaces' interaction to water molecules, generally affect the ice nucleation through the average adsorption energy per unit-area surfaces to individual water molecules, when the lattice of surfaces mismatches that of ice. However, for the surfaces whose lattice matches ice, even the detailed function form of the surfaces' interaction to water molecules can largely regulate the icing ability of these surfaces. This study provides new insights into understanding the diverse relationship between various microscopic features of different material surfaces and their nucleation efficacy.

GENERAL

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Matrix integrable fifth-order mKdV equations and their soliton solutions Wen-Xiu Ma(马文秀) Chin. Phys. B, 2023, 32 (2):  020201.  DOI: 10.1088/1674-1056/ac7dc1 Abstract ( 420 )   HTML ( 3 )   PDF (442KB) ( 211 )   We consider matrix integrable fifth-order mKdV equations via a kind of group reductions of the Ablowitz-Kaup-Newell-Segur matrix spectral problems. Based on properties of eigenvalue and adjoint eigenvalue problems, we solve the corresponding Riemann-Hilbert problems, where eigenvalues could equal adjoint eigenvalues, and construct their soliton solutions, when there are zero reflection coefficients. Illustrative examples of scalar and two-component integrable fifth-order mKdV equations are given.

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Comparison of differential evolution, particle swarm optimization, quantum-behaved particle swarm optimization, and quantum evolutionary algorithm for preparation of quantum states Xin Cheng(程鑫), Xiu-Juan Lu(鲁秀娟), Ya-Nan Liu(刘亚楠), and Sen Kuang(匡森) Chin. Phys. B, 2023, 32 (2):  020202.  DOI: 10.1088/1674-1056/ac65ee Abstract ( 313 )   HTML ( 3 )   PDF (830KB) ( 121 )   Four intelligent optimization algorithms are compared by searching for control pulses to achieve the preparation of target quantum states for closed and open quantum systems, which include differential evolution (DE), particle swarm optimization (PSO), quantum-behaved particle swarm optimization (QPSO), and quantum evolutionary algorithm (QEA). We compare their control performance and point out their differences. By sampling and learning for uncertain quantum systems, the robustness of control pulses found by these four algorithms is also demonstrated and compared. The resulting research shows that the QPSO nearly outperforms the other three algorithms for all the performance criteria considered. This conclusion provides an important reference for solving complex quantum control problems by optimization algorithms and makes the QPSO be a powerful optimization tool.

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Explicit K-symplectic methods for nonseparable non-canonical Hamiltonian systems Beibei Zhu(朱贝贝), Lun Ji(纪伦), Aiqing Zhu(祝爱卿), and Yifa Tang(唐贻发) Chin. Phys. B, 2023, 32 (2):  020204.  DOI: 10.1088/1674-1056/aca9c8 Abstract ( 315 )   HTML ( 2 )   PDF (1271KB) ( 139 )   We propose efficient numerical methods for nonseparable non-canonical Hamiltonian systems which are explicit, K-symplectic in the extended phase space with long time energy conservation properties. They are based on extending the original phase space to several copies of the phase space and imposing a mechanical restraint on the copies of the phase space. Explicit K-symplectic methods are constructed for two non-canonical Hamiltonian systems. Numerical tests show that the proposed methods exhibit good numerical performance in preserving the phase orbit and the energy of the system over long time, whereas higher order Runge-Kutta methods do not preserve these properties. Numerical tests also show that the K-symplectic methods exhibit better efficiency than that of the same order implicit symplectic, explicit and implicit symplectic methods for the original nonseparable non-canonical systems. On the other hand, the fourth order K-symplectic method is more efficient than the fourth order Yoshida's method, the optimized partitioned Runge-Kutta and Runge-Kutta-Nyström explicit K-symplectic methods for the extended phase space Hamiltonians, but less efficient than the the optimized partitioned Runge-Kutta and Runge-Kutta-Nyström extended phase space symplectic-like methods with the midpoint permutation.

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Molecular dynamics study of interactions between edge dislocation and irradiation-induced defects in Fe–10Ni–20Cr alloy Tao-Wen Xiong(熊涛文), Xiao-Ping Chen(陈小平), Ye-Ping Lin(林也平), Xin-Fu He(贺新福), Wen Yang(杨文), Wang-Yu Hu(胡望宇), Fei Gao(高飞), and Hui-Qiu Deng(邓辉球) Chin. Phys. B, 2023, 32 (2):  020206.  DOI: 10.1088/1674-1056/ac7dba Abstract ( 358 )   HTML ( 2 )   PDF (3661KB) ( 113 )   Irradiation-induced defects frequently impede the slip of dislocations, resulting in a sharp decline in the performance of nuclear reactor structural materials, particularly core structural materials. In the present work, molecular dynamics method is used to investigate the interactions between edge dislocations and three typical irradiation-induced defects (void, Frank loop, and stacking fault tetrahedron) with the sizes of 3 nm, 5 nm, and 7 nm at different temperatures in Fe-10Ni-20Cr alloy. The critical resolved shear stresses (CRSSs) are compared among different defect types after interacting with edge dislocations. The results show that the CRSS decreases with temperature increasing and defect size decreasing for each defect type during the interaction with edge dislocations, except for the case of 3-nm Frank loops at 900 K. According to a comparison, the CRSS in Frank loop is significantly higher than that of others of the same size, which is due to the occurrence of unfaulting and formation of superjog or stacking-fault complex during the interaction. The atomic evolution of irradiation-induced defects after interacting with dislocations can provide a novel insight into the design of new structural materials.

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Engineering topological state transfer in four-period Su-Schrieffer-Heeger chain Xi-Xi Bao(包茜茜), Gang-Feng Guo(郭刚峰), and Lei Tan(谭磊) Chin. Phys. B, 2023, 32 (2):  020301.  DOI: 10.1088/1674-1056/ac7bfe Abstract ( 406 )   HTML ( 6 )   PDF (2560KB) ( 209 )   An extended Su-Schrieffer-Heeger (SSH) model containing four periods of the hopping coefficients, called SSH4 model, is constructed to explore robust quantum state transfer. The gap state protected by the energy gap plays the role of the topological channel where the particle initially located at the last lattice site has the probability to arise at the first and all even lattice sites equally. Serving those sites as ports, a multi-port router can be realized naturally, and the fidelity reaches unity in a wide range of parameters under the long chain and random disorder. Further, when we reduce the third intracell hopping to a small value, the occupancy probability of the second lattice site in every unit cell will reduce to zero, by which a new topological router can be induced. In addition, our SSH4 model can work as a 1/3 beam splitter. Namely, the particle initially occupies the first lattice site and finally appears with equal probability at three lattice sites. We can also realize a 1/2 beam splitter. Our four-period SSH model provides a novel way for topological quantum information processing and can engineer two kinds of quantum optical devices.

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Spontaneous emission of a moving atom in a waveguide of rectangular cross section Jing Zeng(曾静), Jing Lu(卢竞), and Lan Zhou(周兰) Chin. Phys. B, 2023, 32 (2):  020302.  DOI: 10.1088/1674-1056/ac7a11 Abstract ( 337 )   HTML ( 2 )   PDF (521KB) ( 66 )   We study the spontaneous emission (SE) of an excited nonrelativistic two-level system (TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS's transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initially being at rest are obtained, it is found that in the first order of the mass $M$, the frequency of the emitted photon is smaller than the transition frequency of the TLS and the SE rate is smaller than the SE rate $\varGamma_{\rm f}$ of the TLS fixed in the same waveguide. The SE rate for the TLS initially being moving is obtained in the second order of the mass $M$. The SE rate is smaller than $\varGamma_{\rm f}$ but it is dependent not only on the atomic mass but also on the initial momentum. The carried frequency of the emitted photon is decreased when it travels along the direction of the initial momentum, whereas it is increased when it travels in the opposite direction of the initial momentum.

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Novel traveling quantum anonymous voting scheme via GHZ states Wenhao Zhao(赵文浩) and Min Jiang(姜敏) Chin. Phys. B, 2023, 32 (2):  020303.  DOI: 10.1088/1674-1056/ac9b2e Abstract ( 349 )   HTML ( 4 )   PDF (555KB) ( 201 )   Based on traveling ballot mode, we propose a secure quantum anonymous voting via Greenberger-Horne-Zeilinger (GHZ) states. In this scheme, each legal voter performs unitary operation on corresponding position of particle sequence to encode his/her voting content. The voters have multiple ballot items to choose rather than just binary options "yes" or "no". After counting votes phase, any participant who is interested in voting results can obtain the voting results. To improve the efficiency of the traveling quantum anonymous voting scheme, an optimization method based on grouping strategy is also presented. Compared with the most existing traveling quantum voting schemes, the proposed scheme is more practical because of its privacy, verifiability and non-repeatability. Furthermore, the security analysis shows that the proposed traveling quantum anonymous voting scheme can prevent various attacks and ensure high security.

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Performance of phase-matching quantum key distribution based on wavelength division multiplexing technology Haiqiang Ma(马海强), Yanxin Han(韩雁鑫), Tianqi Dou(窦天琦), and Pengyun Li(李鹏云) Chin. Phys. B, 2023, 32 (2):  020304.  DOI: 10.1088/1674-1056/ac6ee3 Abstract ( 405 )   HTML ( 2 )   PDF (691KB) ( 157 )   Quantum key distribution (QKD) generates information-theoretical secure keys between two parties based on the physical laws of quantum mechanics. The phase-matching (PM) QKD protocol allows the key rate to break the quantum channel secret key capacity limit without quantum repeaters, and the security of the protocol is demonstrated by using equivalent entanglement. In this paper, the wavelength division multiplexing (WDM) technique is applied to the PM-QKD protocol considering the effect of crosstalk noise on the secret key rate. The performance of PM-QKD protocol based on WDM with the influence of adjacent classical channels and Raman scattering is analyzed by numerical simulations to maximize the total secret key rate of the QKD, providing a reference for future implementations of QKD based on WDM techniques.

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Hall conductance of a non-Hermitian two-band system with k-dependent decay rates Junjie Wang(王俊杰), Fude Li(李福德), and Xuexi Yi(衣学喜) Chin. Phys. B, 2023, 32 (2):  020305.  DOI: 10.1088/1674-1056/ac9046 Abstract ( 314 )   HTML ( 2 )   PDF (1588KB) ( 73 )   Two-band model works well for Hall effect in topological insulators. It turns out to be non-Hermitian when the system is subjected to environments, and its topology characterized by Chern numbers has received extensive studies in the past decades. However, how a non-Hermitian system responses to an electric field and what is the connection of the response to the Chern number defined via the non-Hermitian Hamiltonian remains barely explored. In this paper, focusing on a k-dependent decay rate, we address this issue by studying the response of such a non-Hermitian Chern insulator to an external electric field. To this aim, we first derive an effective non-Hermitian Hamiltonian to describe the system and give a specific form of k-dependent decay rate. Then we calculate the response of the non-Hermitian system to a constant electric field. We observe that the environment leads the Hall conductance to be a weighted integration of curvature of the ground band and hence the conductance is no longer quantized in general. And the environment induces a delay in the response of the system to the electric field. A discussion on the validity of the non-Hermitian model compared with the master equation description is also presented.

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Realization of the iSWAP-like gate among the superconducting qutrits Peng Xu(许鹏), Ran Zhang(张然), and Sheng-Mei Zhao(赵生妹) Chin. Phys. B, 2023, 32 (2):  020306.  DOI: 10.1088/1674-1056/ac89e7 Abstract ( 354 )   HTML ( 2 )   PDF (1156KB) ( 201 )   High-dimensional quantum systems, such as qutrits (quantum three-level systems), have multiple accessible energy levels beyond the two-level qubits. Therefore, qutrits can offer a larger state space to improve the efficiency of quantum computation. Here, we demonstrate a high-fidelity iSWAP-like gate operation on a frequency-tunable superconducting qutrits system. The superconducting quantum system consists of two qutrits that are coupled via a resonator with fixed qutrit-resonator coupling strengths. Through designing the frequency pulse profile and optimizing the parameter values, the gate error can be suppressed below 1.5×10-3. To bear out the feasibility of the proposal, we have conducted our study with experimentally accessible parameters. As the resonator can mediate the interaction between the irrelevant qutrits, the presented approach can also be used to couple multiple qutrits together, providing a good platform for quantum information processing.

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Realizing reliable XOR logic operation via logical chaotic resonance in a triple-well potential system Huamei Yang(杨华美) and Yuangen Yao(姚元根) Chin. Phys. B, 2023, 32 (2):  020501.  DOI: 10.1088/1674-1056/ac6945 Abstract ( 335 )   HTML ( 1 )   PDF (1442KB) ( 67 )   There exists an optimal range of intensity of a chaotic force in which the behavior of a chaos-driven bistable system with two weak inputs can be consistently mapped to a specific logic output. This phenomenon is called logical chaotic resonance (LCR). However, realization of a reliable exclusive disjunction (XOR) through LCR has not been reported. Here, we explore the possibility of using chaos to enhance the reliability of XOR logic operation in a triple-well potential system via LCR. The success probability $P$ of obtaining XOR logic operation can take the maximum value of 1 in an optimal window of intensity $D$ of a chaotic force. Namely, success probability $P$ displays characteristic bell-shaped behavior by altering the intensity of the chaotic driving force, indicating the occurrence of LCR. Further, the effects of periodic force on LCR have been investigated. For a subthreshold chaotic force, a periodic force with appropriate amplitude and frequency can help enhance the reliability of XOR logic operation. Thus, LCR can be effectively regulated by changing the amplitude and frequency of the periodic force.

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Epilepsy dynamics of an astrocyte-neuron model with ammonia intoxication Zhixuan Yuan(袁治轩), Mengmeng Du(独盟盟), Yangyang Yu(于羊羊), and Ying Wu(吴莹) Chin. Phys. B, 2023, 32 (2):  020502.  DOI: 10.1088/1674-1056/ac6dbc Abstract ( 363 )   HTML ( 1 )   PDF (1439KB) ( 107 )   Experimental records in the cerebral cortex indicate that ammonia injection can lead to seizures. Considering that astrocytes play a vital role in mediating the uptake and absorption of ammonium ions in the extracellular space of the cortical circuit, we constructed a new astrocyte neuron coupling model, which is composed of a neuron and its astrocytes connected through the extracellular space, taking into account of the influence of extracellular ammonium ions. The numerical results verified the previous experimental observation that obtained epileptic firing modes of neurons and postsynaptic GABA reversal potential depolarization triggered by ammonia injection. In addition, we also determined the concentration-response relationship between the ammonium ion concentration and the time of entering epilepsy and predicted the threshold of the ammonium ion concentration for the onset of epilepsy.

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Lossless embedding: A visually meaningful image encryption algorithm based on hyperchaos and compressive sensing Xing-Yuan Wang(王兴元), Xiao-Li Wang(王哓丽), Lin Teng(滕琳), Dong-Hua Jiang(蒋东华), and Yongjin Xian(咸永锦) Chin. Phys. B, 2023, 32 (2):  020503.  DOI: 10.1088/1674-1056/aca149 Abstract ( 495 )   HTML ( 2 )   PDF (1694KB) ( 151 )   A novel visually meaningful image encryption algorithm is proposed based on a hyperchaotic system and compressive sensing (CS), which aims to improve the visual security of steganographic image and decrypted quality. First, a dynamic spiral block scrambling is designed to encrypt the sparse matrix generated by performing discrete wavelet transform (DWT) on the plain image. Then, the encrypted image is compressed and quantified to obtain the noise-like cipher image. Then the cipher image is embedded into the alpha channel of the carrier image in portable network graphics (PNG) format to generate the visually meaningful steganographic image. In our scheme, the hyperchaotic Lorenz system controlled by the hash value of plain image is utilized to construct the scrambling matrix, the measurement matrix and the embedding matrix to achieve higher security. In addition, compared with other existing encryption algorithms, the proposed PNG-based embedding method can blindly extract the cipher image, thus effectively reducing the transmission cost and storage space. Finally, the experimental results indicate that the proposed encryption algorithm has very high visual security.

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Localized nonlinear waves in a myelinated nerve fiber with self-excitable membrane Nkeh Oma Nfor, Patrick Guemkam Ghomsi, and Francois Marie Moukam Kakmeni Chin. Phys. B, 2023, 32 (2):  020504.  DOI: 10.1088/1674-1056/ac720d Abstract ( 312 )   HTML ( 2 )   PDF (2069KB) ( 183 )   We systematically study the evolution of modulated nerve impulses in a myelinated nerve fiber, where both the ionic current and membrane capacitance provide the necessary nonlinear feedbacks. This is achieved by using a perturbation technique, in which the Liénard form of the modified discrete Fitzhugh-Nagumo equation is reduced to the complex Ginzburg-Landau amplitude equation. Three distinct values of the capacitive feedback parameter are considered. At the critical value of the capacitive feedback parameter, it is shown that the dynamics of the system is governed by the dissipative nonlinear Schrödinger equation. Linear stability analysis of the system depicts the instability of plane waves, which is manifested as burst of modulated nerve impulses that fulfills the Benjamin-Feir criteria. Variations of the capacitive feedback parameter generally influences the plane wave stability and hence the type of wave profile identified in the neural network. Results of numerical simulations mainly confirm the propagation, collision, and annihilation of nerve impulses in the myelinated axon.

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Current bifurcation, reversals and multiple mobility transitions of dipole in alternating electric fields Wei Du(杜威), Kao Jia(贾考), Zhi-Long Shi(施志龙), and Lin-Ru Nie(聂林如) Chin. Phys. B, 2023, 32 (2):  020505.  DOI: 10.1088/1674-1056/ac7dbe Abstract ( 366 )   HTML ( 2 )   PDF (718KB) ( 34 )   Anomalous transports of dipole in alternating electric fields are investigated by means of numerical calculation of its average angular velocity (or current). Our results show that the alternating electric fields can make the dipole exhibit many interesting transport behaviors. There exist current bifurcation and multiple current reversal phenomena about frequency of the alternating electric fields in the system in the absence of constant bias force, while many platforms appear in the curve of its average angular velocity vs. the force, i.e., multiple mobility transitions phenomenon in the presence of the constant force, dependent on frequencies of the alternating electric fields. Further investigation indicates that the multiple mobility transitions are attributed to the traveling forces on the dipole. Intrinsic physical mechanism and conditions for the characteristic dynamical behaviors to occur are also discussed in detail. These findings will possess crucial significance for optimizing heating control in the alternating electric fields.

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Entanglement and thermalization in the extended Bose-Hubbard model after a quantum quench: A correlation analysis Xiao-Qiang Su(苏晓强), Zong-Ju Xu(许宗菊), and You-Quan Zhao(赵有权) Chin. Phys. B, 2023, 32 (2):  020506.  DOI: 10.1088/1674-1056/ac76b1 Abstract ( 395 )   HTML ( 5 )   PDF (4272KB) ( 159 )   Exploring the role of entanglement in quantum nonequilibrium dynamics is important to understand the mechanism of thermalization in an isolated system. We study the relaxation dynamics in a one-dimensional extended Bose-Hubbard model after a global interaction quench by considering several observables: the local Boson numbers, the nonlocal entanglement entropy, and the momentum distribution functions. We calculate the thermalization fidelity for different quench parameters and different sizes of subsystems, and the results show that the degree of thermalization is affected by the distance from the integrable point and the size of the subsystem. We employ the Pearson coefficient as the measurement of the correlation between the entanglement entropy and thermalization fidelity, and a strong correlation is demonstrated for the quenched system.

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Simulation based on a modified social force model for sensitivity to emergency signs in subway station Zheng-Yu Cai(蔡征宇), Ru Zhou(周汝), Yin-Kai Cui(崔银锴), Yan Wang(王妍), and Jun-Cheng Jiang(蒋军成) Chin. Phys. B, 2023, 32 (2):  020507.  DOI: 10.1088/1674-1056/ac7550 Abstract ( 382 )   HTML ( 3 )   PDF (787KB) ( 120 )   The subway is the primary travel tool for urban residents in China. Due to the complex structure of the subway and high personnel density in rush hours, subway evacuation capacity is critical. The subway evacuation model is explored in this work by combining the improved social force model with the view radius using the Vicsek model. The pedestrians are divided into two categories based on different force models. The first category is sensitive pedestrians who have normal responses to emergency signs. The second category is insensitive pedestrians. By simulating different proportions of the insensitive pedestrians, we find that the escape time is directly proportional to the number of insensitive pedestrians and inversely proportional to the view radius. However, when the view radius is large enough, the escape time does not change significantly, and the evacuation of people in a small view radius environment tends to be integrated. With the improvement of view radius conditions, the escape time changes more obviously with the proportion of insensitive pedestrians. A new emergency sign layout is proposed, and the simulations show that the proposed layout can effectively reduce the escape time in a small view radius environment. However, the evacuation effect of the new escape sign layout on the large view radius environment is not apparent. In this case, the exit setting emerges as an additional factor affecting the escape time.

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Precise measurement of 171Yb magnetic constants for 1S0–3P0 clock transition Ang Zhang(张昂), Congcong Tian(田聪聪), Qiang Zhu(朱强), Bing Wang(王兵), Dezhi Xiong(熊德智), Zhuanxian Xiong(熊转贤), Lingxiang He(贺凌翔), and Baolong Lyu(吕宝龙) Chin. Phys. B, 2023, 32 (2):  020601.  DOI: 10.1088/1674-1056/aca14e Abstract ( 356 )   HTML ( 1 )   PDF (1200KB) ( 234 )   We present a precise measurement of $^{171}$Yb magnetic constants for $^{1}S_{0}$-$^{3}P_{0}$ clock transition. The background magnetic field is firstly compensated to $< 1$ $\rm{mGs}$ (1 ${\rm Gs}=10^{-4}$ T) through measuring the splitting of two $ \pi $ transitins of $^{171}$Yb clock transition at different compensation coils currents. Then, the splitting ratios of the $ \pi $ and $ \sigma $ components of $^{171}$Yb clock transition at different bias magnetic fields are measured, and the first-order Zeeman coefficient is determined to be $\alpha = 199.49(5)$ $\rm{Hz/Gs}$. The second-order Zeeman shifts at various bias magnetic fields are also measured through interleaved self-comparison in which the bias magnetic fields are modulated between high and low values. The second-order Zeeman coefficient is fitted to be $ \beta = -6.09(3)$ $\rm{Hz/mT^{2}}$, which is consistent with the result of NIST group.

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In situ temperature measurement of vapor based on atomic speed selection Lu Yu(于露), Li Cao(曹俐), Ziqian Yue(岳子骞), Lin Li(李林), and Yueyang Zhai(翟跃阳) Chin. Phys. B, 2023, 32 (2):  020602.  DOI: 10.1088/1674-1056/ac8341 Abstract ( 390 )   HTML ( 2 )   PDF (1955KB) ( 116 )   We demonstrate an experimental method for the in situ temperature measurement of atomic vapor using the saturated absorption spectrum. By separately manipulating the frequency of the pump and probe beams, the position of the crossover peaks can move along the spectrum. Different velocity classes of atoms contribute to the crossover during the movement. We study the relationship between the intensity change of peaks and vapor temperature. Our experimental result around room temperature shows a deviation of less than 0.3 K. Compared with traditional thermometry using absorption spectroscopy, higher accuracy can theoretically be achieved with real-time thermometry.

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Achieving highly-efficient H2S gas sensor by flower-like SnO2-SnO/porous GaN heterojunction Zeng Liu(刘增), Ling Du(都灵), Shao-Hui Zhang(张少辉), Ang Bian(边昂), Jun-Peng Fang(方君鹏), Chen-Yang Xing(邢晨阳), Shan Li(李山), Jin-Cheng Tang(汤谨诚), Yu-Feng Guo(郭宇锋), and Wei-Hua Tang(唐为华) Chin. Phys. B, 2023, 32 (2):  020701.  DOI: 10.1088/1674-1056/ac6947 Abstract ( 334 )   HTML ( 2 )   PDF (1839KB) ( 135 )   A flower-like SnO2-SnO/porous GaN (FSS/PGaN) heterojunction was fabricated for the first time via a facile spraying process, and the whole process also involved hydrothermal preparation of FSS and electrochemical wet etching of GaN, and SnO2-SnO composites with p-n junctions were loaded onto PGaN surface directly applied to H2S sensor. Meanwhile, the excellent transport capability of heterojunction between FSS and PGaN facilitates electron transfer, that is, a response time as short as 65 s and a release time up to 27 s can be achieved merely at 150 ℃ under 50 ppm H2S concentration, which has laid a reasonable theoretical and experimental foundation for the subsequent PGaN-based heterojunction gas sensor. The lowering working temperature and high sensitivity (23.5 at 200 ppm H2S) are attributed to the structure of PGaN itself and the heterojunction between SnO2-SnO and PGaN. In addition, the as-obtained sensor showed ultra-high test stability. The simple design strategy of FSS/PGaN-based H2S sensor highlights its potential in various applications.

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Dual-channel fiber-optic surface plasmon resonance sensor with cascaded coaxial dual-waveguide D-type structure and microsphere structure Ling-Ling Li(李玲玲), Yong Wei(魏勇), Chun-Lan Liu(刘春兰), Zhuo Ren(任卓), Ai Zhou(周爱), Zhi-Hai Liu(刘志海), and Yu Zhang(张羽) Chin. Phys. B, 2023, 32 (2):  020702.  DOI: 10.1088/1674-1056/ac9de3 Abstract ( 385 )   HTML ( 2 )   PDF (4162KB) ( 180 )   To address the restriction of fiber-optic surface plasmon resonance (SPR) sensors in the field of multi-sample detection, a novel dual-channel fiber-optic SPR sensor based on the cascade of coaxial dual-waveguide D-type structure and microsphere structure is proposed in this paper. The fiber sidepolishing technique converts the coaxial dual-waveguide fiber into a D-type one, and the evanescent wave in the ring core leaks, generating a D-type sensing region; the fiber optic fused ball push technology converts the coaxial dual waveguides into microspheres, and the stimulated cladding mode evanescent wave leaks, producing the microsphere sensing region. By injecting light into the coaxial dual-waveguide middle core alone, the sensor can realize single-stage sensing in the microsphere sensing area; it can also realize dual-channel sensing in the D-type sensing area and microsphere sensing area by injecting light into the ring core. The refractive index measurement ranges for the two channels are 1.333-1.365 and 1.375-1.405, respectively, with detection sensitivities of 981.56 nm/RIU and 4138 nm/RIU. The sensor combines wavelength division multiplexing and space division multiplexing technologies, presenting a novel research concept for multi-channel fiber SPR sensors.

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Improvement of coercivity thermal stability of sintered 2:17 SmCo permanent magnet by Nd doping Chao-Zhong Wang(王朝中), Lei Liu(刘雷), Ying-Li Sun(孙颖莉), Jiang-Tao Zhao(赵江涛), Bo Zhou (周波), Si-Si Tu(涂思思), Chun-Guo Wang(王春国), Yong Ding(丁勇), and A-Ru Yan(闫阿儒) Chin. Phys. B, 2023, 32 (2):  020704.  DOI: 10.1088/1674-1056/ac70b7 Abstract ( 330 )   HTML ( 2 )   PDF (4168KB) ( 112 )   The effects of Nd doping on the microstructures and magnetic properties of Sm$_{1-x}$Nd$_{x}$ (Co$_{0.695}$Fe$_{0.2}$Cu$_{0.08}$Zr$_{0.025}$)$_{7.2}$ ($x=0$, 0.3, 0.5, 0.7, 1.0) permanent magnets are studied. The scanning electron microscope (SEM) analysis of the solid solution states of the magnets shows that with the increase of Nd content, the distribution of elements becomes inhomogeneous and miscellaneous phase will be generated. Positive temperature coefficient of coercivity ($\beta $) appears in each of the samples with $x=0.3$, 0.5, and 0.7. The corresponding positive $\beta $ temperatures are in ranges of about 70 K-170 K, 60 K-260 K, 182 K-490 K for the samples with $x=0.3$, 0.5, and 0.7, respectively. Thermomagnetic analysis shows that spin-reorientation-transition (SRT) of the cell boundary phase is responsible for this phenomenon. On the basis of this discovery, the Sm$_{0.7}$Nd$_{0.3}$ (Co$_{0.695}$Fe$_{0.2}$Cu$_{0.08}$Zr$_{0.025}$)$_{7.2}$ magnet possessing thermal stability with $\beta \approx -0.002 $ %/K at the temperature in a range of 150 K-200 K is obtained.

ATOMIC AND MOLECULAR PHYSICS

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Formation of nanobubbles generated by hydrate decomposition: A molecular dynamics study Zilin Wang(王梓霖), Liang Yang(杨亮), Changsheng Liu(刘长生), and Shiwei Lin(林仕伟) Chin. Phys. B, 2023, 32 (2):  023101.  DOI: 10.1088/1674-1056/ac786a Abstract ( 393 )   HTML ( 3 )   PDF (2015KB) ( 191 )   Natural gas hydrate is estimated to have huge reserves. Its exploitation can solve the global oil and gas shortage problem. Hydrates decompose into water and methane, and methane molecules are supersaturated to form nanobubbles. Methane nanobubbles can affect the decomposition efficiency of hydrates. They can provide abundant methane sources for the re-nucleation of hydrates. Molecular dynamics is employed in this study to investigate the decomposition process of type I methane hydrate and the formation of methane nanobubbles generated during decomposition under different methane mole fraction, pressures, and temperatures. The results indicate that external pressure inhibits the diffusion of methane molecules, thereby preventing the formation of nanobubbles. A higher mole fraction of methane molecules in the system requires a higher external pressure to generate stable nanobubbles after the decomposition of the hydrate structure. At 330 K, it is easy to form a nanobubble structure. Results of this study can help provide ideas for the study of efficient extraction and secondary nucleation of hydrates.

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Wavelength- and ellipticity-dependent photoelectron spectra from multiphoton ionization of atoms Keyu Guo(郭珂雨), Min Li(黎敏), Jintai Liang(梁锦台), Chuanpeng Cao(曹传鹏), Yueming Zhou(周月明), and Peixiang Lu((陆培祥) Chin. Phys. B, 2023, 32 (2):  023201.  DOI: 10.1088/1674-1056/ac9b36 Abstract ( 325 )   HTML ( 2 )   PDF (1846KB) ( 113 )   We theoretically study the photoelectron momentum distributions from multiphoton ionization of a model lithium atom over a range of laser wavelengths from 500 nm to 700 nm by numerically solving the time-dependent Schrödinger equation. The photoelectron momentum distributions display many ring-like patterns for the three-photon ionization, which vary dramatically with the change of the laser wavelength. We show that the wavelength-dependent photoelectron energy spectrum can be used to effectively identify the resonant and nonresonant ionization pathways. We also find an abnormal ellipticity dependence of the electron yield for the (2+1) resonance-enhanced ionization via the 4d intermediate state, which is relevant to the two-photon excitation probability from the ground state to the 4d state.

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Generation of a blue-detuned optical storage ring by a metasurface and its application in optical trapping of cold molecules Chen Ling(凌晨), Yaling Yin(尹亚玲), Yang Liu(刘泱), Lin Li(李林), and Yong Xia(夏勇) Chin. Phys. B, 2023, 32 (2):  023301.  DOI: 10.1088/1674-1056/ac6db0 Abstract ( 365 )   HTML ( 2 )   PDF (1397KB) ( 75 )   A scheme for storage of cold molecules in a hollow optical ring generated by a metasurface grating is proposed. The characteristics and intensity distribution related to the ring's structural parameters and fabrication error tolerance are theoretically studied. The optical potential and dipole force required for the ring to trap magnesium monofluoride (MgF) molecules are also calculated. The dynamic behavior of MgF molecules in the storage ring is simulated by a Monte Carlo method, which shows that a metasurface-based optical storage ring can be used to trap molecules and is an interesting platform for research into ultracold quantum gases and their quantum-state manipulation.

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Fine and hyperfine structures of pionic helium atoms Zhi-Da Bai(白志达), Zhen-Xiang Zhong(钟振祥), Zong-Chao Yan(严宗朝), and Ting-Yun Shi(史庭云) Chin. Phys. B, 2023, 32 (2):  023601.  DOI: 10.1088/1674-1056/ac6db9 Abstract ( 320 )   HTML ( 2 )   PDF (948KB) ( 123 )   The fine and hyperfine structures of pionic helium metastable states is calculated within the formalism of the Breit-Pauli Hamiltonian by using the variationally generated wave functions in Hylleraas coordinates. Our results not only verify the existing values of Hori ${\it et al.}$ [${Phys. Rev. A} {\bf 89}$, 042515 (2014)] for the fine structure of $\pi^4$He$^+$, but also determine the hyperfine structure of $\pi^3$He$^+$.

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Quantum degenerate Bose-Fermi atomic gas mixture of 23Na and 40K Ziliang Li(李子亮), Zhengyu Gu(顾正宇), Zhenlian Shi(师振莲), Pengjun Wang(王鹏军), and Jing Zhang(张靖) Chin. Phys. B, 2023, 32 (2):  023701.  DOI: 10.1088/1674-1056/aca14f Abstract ( 386 )   HTML ( 1 )   PDF (1755KB) ( 161 )   We report a compact experimental setup for producing a quantum degenerate mixture of Bose $^{23}$Na and Fermi $^{40}$K gases. The atoms are collected in dual dark magneto-optical traps (MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the $D_{2}$ line for $^{23}$Na and $D_{1}$ line for $^{40}$K. The microwave evaporation cooling is used to cool $^{23}$Na in $| F=2,m_{F}=2\rangle$ in an optically plugged magnetic trap, meanwhile, $^{40}$K in $| F=9/2,m_{F}=9/2\rangle$ is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where $^{23}$Na atoms are immediately transferred to $|1,1\rangle$ for further effective cooling to avoid the strong three-body loss between $^{23}$Na atoms in $|2,2\rangle$ and $^{40}$K atoms in $|9/2,9/2\rangle$. At the end of the evaporation in optical trap, a degenerate Fermi gas of $^{40}$K with $1.9 \times10^{5}$ atoms at $T/T_{F}=0.5$ in the $|9/2,9/2\rangle$ hyperfine state coexists with a Bose-Einstein condensate (BEC) of $^{23}$Na with $8\times10^{4}$ atoms in the $|1,1\rangle$ hyperfine state at 300 nK. We also can produce the two species mixture with the tunable population imbalance by adjusting the $^{23}$Na magneto-optical trap loading time.

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

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High efficiency of broadband transmissive metasurface terahertz polarization converter Qiangguo Zhou(周强国), Yang Li(李洋), Yongzhen Li(李永振), Niangjuan Yao(姚娘娟), and Zhiming Huang(黄志明) Chin. Phys. B, 2023, 32 (2):  024201.  DOI: 10.1088/1674-1056/ac6db7 Abstract ( 407 )   HTML ( 9 )   PDF (3484KB) ( 296 )   Terahertz wave is between microwave and infrared bands in the electromagnetic spectrum with the frequency range from 0.1 THz to 10 THz. Controlling and processing of the polarization state in terahertz wave are the focus due to its great influence on the characteristics. In this paper, a transmissive metasurface terahertz polarization converter is designed in 3D structure with an upper surface of ruler-like rectangular, an intermediate dielectric layer and a lower surface of metal grid wires. Numerical simulations of the converter show that the polarization conversion ratio (PCR) is above 99.9% at 0.288 THz-1.6 THz, the polarization rotation angle (PRA) is close to 90° at 0.06 THz-1.4 THz, and the ellipticity angle (EA) is close to 0° at 0.531 THz-1.49 THz. The origin of the efficient polarization conversion is explained by analyzing the electric field intensity, magnetic field intensity, surface current, electric field energy density, and magnetic field energy density distributions of the converter at 1.19 THz and 0.87 THz, which are consistent with the energy transmittance and transmittance coefficient. In addition, the effects of different thickness and material of intermediate layer, thickness of upper surface material, polarized wave incidence angle, and metasurface materials on the performance of the polarization converter are discussed, and how they affect the conversion performance of the polarization converter are also explained. Our results provide a strong theoretical basis and technical support to develop high performance transmission-type terahertz polarization converters, and play an important role to promote the development of terahertz science and technology.

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Research on the model of high robustness computational optical imaging system Yun Su(苏云), Teli Xi(席特立), and Xiaopeng Shao(邵晓鹏) Chin. Phys. B, 2023, 32 (2):  024202.  DOI: 10.1088/1674-1056/ac9b34 Abstract ( 366 )   HTML ( 1 )   PDF (3491KB) ( 191 )   Computational optical imaging is an interdisciplinary subject integrating optics, mathematics, and information technology. It introduces information processing into optical imaging and combines it with intelligent computing, subverting the imaging mechanism of traditional optical imaging which only relies on orderly information transmission. To meet the high-precision requirements of traditional optical imaging for optical processing and adjustment, as well as to solve its problems of being sensitive to gravity and temperature in use, we establish an optical imaging system model from the perspective of computational optical imaging and studies how to design and solve the imaging consistency problem of optical system under the influence of gravity, thermal effect, stress, and other external environment to build a high robustness optical system. The results show that the high robustness interval of the optical system exists and can effectively reduce the sensitivity of the optical system to the disturbance of each link, thus realizing the high robustness of optical imaging.

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Laser shaping and optical power limiting of pulsed Laguerre-Gaussian laser beams of high-order radial modes in fullerene C60 Jie Li(李杰), Wen-Hui Guan(管文慧), Shuo Yuan(袁烁), Ya-Nan Zhao(赵亚男), Yu-Ping Sun(孙玉萍), and Ji-Cai Liu(刘纪彩) Chin. Phys. B, 2023, 32 (2):  024203.  DOI: 10.1088/1674-1056/ac70b6 Abstract ( 328 )   HTML ( 2 )   PDF (1139KB) ( 106 )   We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre-Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60 molecular medium. It is found that the spatiotemporal profile of the incident pulsed Laguerre-Gaussian laser beam is strongly reshaped during its propagation in the C60 molecular medium. The centrosymmetric temporal profile of the incident pulse gradually evolves into a non-centrosymmetric meniscus shape, and the on-axis pulse duration is clearly depressed. Furthermore, the field intensity is distinctly attenuated due to the field-intensity-dependent reverse saturable absorption, and clear optical power limiting behavior is observed for different orders of the input pulsed Laguerre-Gaussian laser beams before the takeover of the saturation effect; the lower the order of the Laguerre-Gaussian beam, the lower the energy transmittance.

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A band-pass frequency selective surface with polarization rotation Bao-Qin Lin(林宝勤), Wen-Zhun Huang(黄文准), Jian-Xin Guo(郭建新), Zhe Liu(刘哲), Yan-Wen Wang(王衍文), and Hong-Jun Ye(叶红军) Chin. Phys. B, 2023, 32 (2):  024204.  DOI: 10.1088/1674-1056/ac6496 Abstract ( 366 )   HTML ( 2 )   PDF (1153KB) ( 243 )   A band-pass frequency selective surface (FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS (PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-antenna (AFA) module, and the polarization directions of the upper and lower antennas in each AFA module are orthogonal to each other, so the PR-FSS can achieve frequency selection and 90 degrees polarization rotation at the same time. The numerical simulation demonstrate that the anticipated frequency selection and polarization rotation are realized by the PR-FSS in the frequency band from 8.84 GHz to 10.30 GHz with a relative bandwidth of 15.26%, and the maximum insertion loss in the pass band is only 0.17 dB. Finally, one effective experiment validation is carried out, a reasonable agreement is observed between the experimental and simulated results except for a slight deviation caused by fabrication error and measurement tolerance.

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Multi-band polarization switch based on magnetic fluid filled dual-core photonic crystal fiber Lianzhen Zhang(张连震), Xuedian Zhang(张学典), Xiantong Yu(俞宪同), Xuejing Liu(刘学静), Jun Zhou(周军), Min Chang(常敏), Na Yang(杨娜), and Jia Du(杜嘉) Chin. Phys. B, 2023, 32 (2):  024205.  DOI: 10.1088/1674-1056/ac9a37 Abstract ( 298 )   HTML ( 1 )   PDF (1621KB) ( 126 )   The research of high-performance polarization controllers is of great significance for expanding the application field of polarization optics. Here, a polarization switch is demonstrated by using a dual-core photonic crystal fiber (DCPCF) with four symmetrical air holes, placed above and below each core, filled with magnetic fluid (MF). The switch, which utilizes a magnetic field to change the coupling length ratio of the x and y polarization modes, enables dynamic tuning of the polarization state and extinction ratio. Numerical results show that when the working length is 36.638 mm, the magneto-optical polarization switch can operate in four communication bands, i.e., 1509 nm to 1520 nm, 1544 nm to 1556 nm, 1578 nm to 1591 nm, and 1611 nm to 1624 nm. Moreover, the extinction ratio (ER) is greater than 20 dB in the fiber length range of 38.5 mm to 38.7 mm, indicating that the device has a good fault tolerance for the interception of the fiber length.

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Optomagnonically tunable whispering gallery cavity laser wavelength conversion Yining Zhu(朱奕宁), Zixu Zhu(朱子虚), Anbang Pei(裴安邦), and Yong-Pan Gao(高永潘) Chin. Phys. B, 2023, 32 (2):  024206.  DOI: 10.1088/1674-1056/ac7862 Abstract ( 342 )   HTML ( 1 )   PDF (1116KB) ( 66 )   We achieve laser wavelength conversion in an optomagnonical whispering gallery cavity by adjusting the strength of the applied static magnetic field. Numerical simulations are carried out on a yttrium iron garnet (YIG) sphere under different cavity quality factors or coupling strength. It is found that a high cavity quality factor will not always mean a high cavity excitation field for Gaussian lasers with finite linewidth. On state of the art, the high cavity quality factor will always mean the higher lightwave conversion rate. In addition, we also find that increasing the mode coupling strength is beneficial to the conversion of the laser. Our study provides new insights into generation of highly precise tunable coherent light.

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A cladding-pumping based power-scaled noise-like and dissipative soliton pulse fiber laser Zhiguo Lv(吕志国), Hao Teng(滕浩), and Zhiyi Wei(魏志义) Chin. Phys. B, 2023, 32 (2):  024207.  DOI: 10.1088/1674-1056/ac8f3e Abstract ( 397 )   HTML ( 2 )   PDF (1623KB) ( 205 )   We report a high-average-power noise-like pulse (NLP) and dissipative soliton (DS) pulse fiber laser. Average power as high as 4.8 W could be obtained at the fundamental mode-locked repetition rate. The NLP can also be transformed into a more powerful DS mode-locking state by optimizing the polarization and losses of intra-cavity pulses in the nonlinear polarization evolution regime. The operation mode between the NLP and DS can be switched, and the laser output performance in both modes has been studied. The main advantage of this work is switchable high-power operation between the NLP and DS. In comparison with conventional single-mode NLP fiber lasers, the multi-function high-power optical source will greatly push its application in supercontinuum generation, coherence tomography, and industrial processing.

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Tightly focused properties of a partially coherent radially polarized power-exponent-phase vortex beam Kang Chen(陈康), Zhi-Yuan Ma(马志远), and You-You Hu(胡友友) Chin. Phys. B, 2023, 32 (2):  024208.  DOI: 10.1088/1674-1056/ac70b0 Abstract ( 335 )   HTML ( 2 )   PDF (3535KB) ( 253 )   A partially coherent beam called a radially polarized multi-Gaussian Schell-model power-exponent-phase vortex beam is introduced. Both the analytical formula of the beam propagating through the high-numerical-aperture objective lens based on the vectorial diffraction theory, and the cross-spectral density matrix of the beam in the focal region are derived. Then, the tight focusing characteristics of the partially coherent radially polarized power-exponent-phase vortex beam are studied numerically, and the intensity distribution, degree of polarization and coherence of the beams in the focusing region with different topological charge, power order, beam index and coherence width are analyzed in detail. The results show that the contour of the spot becomes clearer and smoother with the increase in the beam index, and the focal fields of different structures that include the flattened beam can be obtained by changing the coherence width. In addition, by changing the topological charge and power order, the intensity can gather to a point along the ring. These unique properties will have potential applications in particle capture and manipulation, especially in the manipulation of irregular particles.

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Wavelength switchable mode-locked fiber laser with a few-mode fiber filter Shaokang Bai(白少康), Yujin Xiang(向昱锦), and Zuxing Zhang(张祖兴) Chin. Phys. B, 2023, 32 (2):  024209.  DOI: 10.1088/1674-1056/ac744f Abstract ( 277 )   HTML ( 1 )   PDF (1265KB) ( 167 )   We have proposed and constructed a few-mode fiber (FMF)-based comb filter realized by dislocation splicing a few-mode long-period fiber grating (FM-LPFG) with a single-mode fiber (SMF). From an all-fiber laser with a FMF-based comb filter, the generation of switchable single-, dual-, triple-, and quadruple-wavelength continuous light has been achieved. Moreover, wavelength switchable mode-locked pulses have been obtained with the increased pump power. In the experiment, the output wavelength of the mode-locked fiber laser was changed from 1567.72 nm to 1571.04 nm, while the signal-to-noise (SNR) ratio was maintained above 61 dB. The switchable multiwavelength continuous wave (CW) and mode-locked all-fiber lasers have potentially important applications for fiber sensing, wavelength-division multiplexing (WDM) and signal processing.

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Real-time observation of soliton pulsation in net normal-dispersion dissipative soliton fiber laser Xu-De Wang(汪徐德), Xu Geng(耿旭), Jie-Yu Pan(潘婕妤), Meng-Qiu Sun(孙梦秋), Meng-Xiang Lu(陆梦想), Kai-Xin Li(李凯芯), and Su-Wen Li(李素文) Chin. Phys. B, 2023, 32 (2):  024210.  DOI: 10.1088/1674-1056/ac76b0 Abstract ( 319 )   HTML ( 1 )   PDF (3910KB) ( 114 )   We present experimental observations of soliton pulsations in the net normal-dispersion fiber laser by using the dispersive Fourier transform (DFT) technique. According to the pulsating characteristics, the soliton pulsations are classified as visible and invisible soliton pulsations. The visible soliton pulsation is converted from single- into dual-soliton pulsation with the common characteristics of energy oscillation and bandwidth breathing. The invisible soliton pulsation undergoes periodic variation in the spectral profile and peak power but remains invariable in pulse energy. The reason for invisible soliton pulsation behavior is periodic oscillation of the pulse inside the soliton molecule. These results could be helpful in deepening our understanding of the soliton pulsation phenomena.

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Asymmetrical spiral spectra and orbital angular momentum density of non-uniformly polarized vortex beams in uniaxial crystals Ling-Yun Shu(舒凌云), Ke Cheng(程科), Sai Liao(廖赛), Meng-Ting Liang(梁梦婷), and Ceng-Hao Yang(杨嶒浩) Chin. Phys. B, 2023, 32 (2):  024211.  DOI: 10.1088/1674-1056/ac7860 Abstract ( 316 )   HTML ( 3 )   PDF (7784KB) ( 204 )   To explore the effect of non-uniform polarization on orbital angular momentum (OAM) in anisotropic medium, in this work investigated are the evolution of the spiral spectra and OAM densities of non-uniformly polarized vortex (NUPV) beams in uniaxial crystals propagating orthogonal to the optical axis, and also the case of uniformly polarized vortex (UPV) beams with left-handed elliptical polarization. In the input plane, the NUPV beams present their spiral spectra of $m$-mode concentrated at $m=l\pm 1$ modes rather than $m=l$ mode, and reveal the relation among topological charge $l$, mode of spiral spectra $m$ and the power weight value $R_{m}$ expressed by $l=\sum_{m=-\infty }^\infty {mR_{m} } $. The relation $l=\sum_{m=-\infty }^\infty {mR_{m} } $ is still satisfied for UPV beams in uniaxially anisotropic crystals, whereas for NUPV beams their relations are no longer valid owing to non-uniform polarization. Furthermore, the analysis indicates that the asymmetrical distribution of power weight of spiral spectra and the non-zero value in the sum of longitudinal OAM densities originate from the initial non-uniform polarization and anisotropy in uniaxial crystals rather than topological charges. In addition, the relation between spiral spectrum and longitudinal OAM density is numerically discussed. This work may provide an avenue for OAM-based communications, optical metrology, and imaging by varying the initial non-uniform polarization.

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Coupled-generalized nonlinear Schrödinger equations solved by adaptive step-size methods in interaction picture Lei Chen(陈磊), Pan Li(李磐), He-Shan Liu(刘河山), Jin Yu(余锦), Chang-Jun Ke(柯常军), and Zi-Ren Luo(罗子人) Chin. Phys. B, 2023, 32 (2):  024213.  DOI: 10.1088/1674-1056/ac76a8 Abstract ( 300 )   HTML ( 4 )   PDF (1497KB) ( 162 )   We extend two adaptive step-size methods for solving two-dimensional or multi-dimensional generalized nonlinear Schrödinger equation (GNLSE): one is the conservation quantity error adaptive step-control method (RK4IP-CQE), and the other is the local error adaptive step-control method (RK4IP-LEM). The methods are developed in the vector form of fourth-order Runge-Kutta iterative scheme in the interaction picture by converting a vector equation in frequency domain. By simulating the supercontinuum generated from the high birefringence photonic crystal fiber, the calculation accuracies and the efficiencies of the two adaptive step-size methods are discussed. The simulation results show that the two methods have the same global average error, while RK4IP-LEM spends more time than RK4IP-CQE. The decrease of huge calculation time is due to the differences in the convergences of the relative photon number error and the approximated local error between these two adaptive step-size algorithms.

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A simulation study of polarization characteristics of ultrathin CsPbBr3 nanowires with different cross-section shapes and sizes Kang Yang(杨康), Huiqing Hu(胡回清), Jiaojiao Wang(王娇娇), Lingling Deng(邓玲玲), Yunqing Lu(陆云清), and Jin Wang(王瑾) Chin. Phys. B, 2023, 32 (2):  024214.  DOI: 10.1088/1674-1056/ac744d Abstract ( 333 )   HTML ( 1 )   PDF (1891KB) ( 115 )   The polarization characteristics of ultrathin CsPbBr3 nanowires are investigated. Especially, for the height of cross-section of nanowires between 2 nm and 25 nm, the normalized intensity and polarization ratio ρ of CsPbBr3 nanowires with triangular, square and hexagonal cross-section shapes are compared. The results show that, along with the increase of the height of cross-section, the polarization ratios of these three nanowires decrease until T=15 nm, and increase afterwards. Also, along with the increase of the cross-section area up to 100 nm2, the polarization ratios of these three nanowires increase too. In general, for the same height or area, the polarization ratio ρ of these nanowires follows ρhexagon>ρsquare>ρtriangle. Therefore, the nanowire with the hexagonal cross-section should be chosen, where for a cross-section height of 2 nm and a length-height ratio of 20:1, the maximal polarization ratio is 0.951 at the longitudinal center of the NW. Further, for the hexagonal NW with a cross-section height of 10 nm, the hexagonal NW with a length-height ratio of 45:1 exhibits the maximal polarization ratio at the longitudinal center of the NW. These simulation results predict the feasible size and shape of CsPbBr3 nanowire devices with high polarization ratios.

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Generation of elliptical airy vortex beams based on all-dielectric metasurface Xiao-Ju Xue(薛晓菊), Bi-Jun Xu(徐弼军), Bai-Rui Wu(吴白瑞), Xiao-Gang Wang(汪小刚), Xin-Ning Yu(俞昕宁), Lu Lin(林露), and Hong-Qiang Li(李宏强) Chin. Phys. B, 2023, 32 (2):  024215.  DOI: 10.1088/1674-1056/ac7cd0 Abstract ( 327 )   HTML ( 2 )   PDF (3778KB) ( 282 )   Elliptical airy vortex beams (EAVBs) can spontaneously form easily identifiable topological charge focal spots. They are used for topological charge detection of vortex beams because they have the abruptly autofocusing properties of circular airy vortex beams and exhibit unique propagation characteristics. We study the use of the dynamic phase and Pancharatnam-Berry phase principles for generation and modulation of EAVBs by designing complex-amplitude metasurface and phase-only metasurface, at an operating wavelength of 1500 nm. It is found that the focusing pattern of EAVBs in the autofocusing plane splits into |m| +1 tilted bright spots from the original ring, and the tilted direction is related to the sign of the topological charge number m. Due to the advantages of ultra-thin, ultra-light, and small size of the metasurface, our designed metasurface device has potential applications in improving the channel capacity based on orbital angular momentum communication, information coding, and particle capture compared to spatial light modulation systems that generate EAVBs.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Ignition dynamics of radio frequency discharge in atmospheric pressure cascade glow discharge Ya-Rong Zhang(张亚容), Qian-Han Han(韩乾翰), Jun-Lin Fang(方骏林), Ying Guo(郭颖), and Jian-Jun Shi(石建军) Chin. Phys. B, 2023, 32 (2):  025201.  DOI: 10.1088/1674-1056/ac673d Abstract ( 355 )   HTML ( 3 )   PDF (1419KB) ( 101 )   A cascade glow discharge in atmospheric helium was excited by a microsecond voltage pulse and a pulse-modulated radio frequency (RF) voltage, in which the discharge ignition dynamics of the RF discharge burst was investigated experimentally. The spatio-temporal evolution of the discharge, the ignition time and optical emission intensities of plasma species of the RF discharge burst were investigated under different time intervals between the pulsed voltage and RF voltage in the experiment. The results show that by increasing the time interval between the pulsed discharge and RF discharge burst from 5 μs to 20 μs, the ignition time of the RF discharge burst is increased from 1.6 μs to 2.0 μs, and the discharge spatial profile of RF discharge in the ignition phase changes from a double-hump shape to a bell-shape. The light emission intensity at 706 nm and 777 nm at different time intervals indicates that the RF discharge burst ignition of the depends on the number of residual plasma species generated in the pulsed discharges.

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Gyrokinetic simulation of low-n Alfvénic modes in tokamak HL-2A plasmas Wen-Hao Lin(林文浩), Ji-Quan Li(李继全), J Garcia, and S Mazzi Chin. Phys. B, 2023, 32 (2):  025202.  DOI: 10.1088/1674-1056/ac6b23 Abstract ( 331 )   HTML ( 1 )   PDF (1237KB) ( 71 )   The turbulence characteristics of plasmas with internal transport barriers in the HL-2A tokamak are analyzed by means of linear gyrokinetic simulations. It is found that turbulence is dominated by the ion temperature gradient (ITG) mode together with large-scale modes characterized by high-frequency electromagnetic fluctuation, which are destabilized by the steep ion temperature gradient in the weak magnetic shear regime. Comparison with solutions of analytical dispersion relations shows that their linear features match well with the beta-induced Alfvén eigenmode branch of the shear Alfvénic spectrum. It is further clarified that the large population of fast ions in these plasmas plays a stabilization role through the dilution mechanism in high-n ITG mode regimes.

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Effect of kinetic ions on the toroidal double-tearing modes Ruibo Zhang(张睿博), Lei Ye(叶磊), Yang Chen, Nong Xiang(项农), and Xiaoqing Yang(杨小庆) Chin. Phys. B, 2023, 32 (2):  025203.  DOI: 10.1088/1674-1056/ac7f89 Abstract ( 314 )   HTML ( 1 )   PDF (1247KB) ( 69 )   We investigate the effects of kinetic ions on double-tearing modes (DTMs) using the gyrokinetic particle-in-cell simulation code GEM with a gyrokinetic ion/fluid electron hybrid model. It is found that the ion kinetic effects can decrease the growth rate of the DTMs. This effect is more significant for stronger coupling of DTMs with smaller distance between the rational surfaces. Kinetic ions can also enhance the coupling effect between the two rational surfaces. Energy transfer analyses between particles and wave fields show that the stabilizing effect of kinetic ions comes mainly from the perpendicular magnetic drift of ions in the coupling region and around the outer rational surface.

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Correction of intense laser-plasma interactions by QED vacuum polarization in collision of laser beams Wen-Bo Chen(陈文博) and Zhi-Gang Bu(步志刚) Chin. Phys. B, 2023, 32 (2):  025204.  DOI: 10.1088/1674-1056/ac70b3 Abstract ( 357 )   HTML ( 0 )   PDF (1343KB) ( 71 )   The influence of vacuum polarization effects on the interactions of multiple ultra-intense lasers with plasmas is discussed. The nonlinear paraxial monochromatic model of the interactions has been improved by considering the Heisenberg-Euler Lagrangian density of two laser processes. Comparing the corrections of vacuum polarization effects in the collision of laser beams with one generated by a single intense laser, we find that the former has a higher order of magnitude correction. The laser collision also produces variations in the propagation direction and polarization direction of the lasers propagating in the plasma. In addition, the strong-field quantum electrodynamic (QED) effects can be enhanced by increasing the laser intensity or frequency difference, or by adjusting the incident angles of the two laser beams.

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Influence of magnetic field on power deposition in high magnetic field helicon experiment Yan Zhou(周岩), Peiyu Ji(季佩宇), Maoyang Li(李茂洋), Lanjian Zhuge(诸葛兰剑), and Xuemei Wu(吴雪梅) Chin. Phys. B, 2023, 32 (2):  025205.  DOI: 10.1088/1674-1056/ac7207 Abstract ( 384 )   HTML ( 0 )   PDF (1306KB) ( 102 )   Based on high magnetic field helicon experiment (HMHX), HELIC code was used to study the effect of different magnetic fields on the power deposition under parabolic distribution. This paper is divided into three parts: preliminary calculation, actual discharge experiment and calculation. The results of preliminary calculation show that a magnetic field that is too small or too large cannot produce a good power deposition effect. When the magnetic field strength is 1200 Gs, a better power deposition can be obtained. The actual discharge experiment illustrates that the change of the magnetic field will have a certain influence on the discharge phenomenon. Finally, the results of verification calculation successfully verify the accuracy of the results of preliminary simulation. The results show that in the actual discharge experiment, it can achieve the best deposition effect when the magnetic field is 1185 Gs.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Surface structure modification of ReSe2 nanosheets via carbon ion irradiation Mei Qiao(乔梅), Tie-Jun Wang(王铁军), Yong Liu(刘泳), Tao Liu(刘涛), Shan Liu(刘珊), and Shi-Cai Xu(许士才) Chin. Phys. B, 2023, 32 (2):  026101.  DOI: 10.1088/1674-1056/ac7297 Abstract ( 324 )   HTML ( 0 )   PDF (1962KB) ( 71 )   The effects of C ion irradiation on multilayer ReSe2 flakes are studied by utilizing different kinds of technologies. The domain sizes, thickness, morphologies of the multilayer ReSe2 flakes on the Al2O3 substrates before and after 1.0-MeV C ion irradiation with different fluence rates are studied by atomic force microscope and scanning electron microscopy. The atomic vibrational spectra of multilayer ReSe2 flakes are detected by micro-Raman spectra. The redshifts of the Raman modes after 1.0-MeV C ion irradiation are observed from the micro-Raman spectra. The elemental compositions and bonding configurations of the multilayer ReSe2 samples before and after irradiation processes are characterized by x-ray photoelectron spectroscopy. The structural properties are also investigated by x-ray diffraction, and it is concluded that after 1.0-MeV C ion irradiation process, multilayer ReSe2 samples continue to grow on Al2O3 substrates, the increase of crystallite size also reveals that the crystallinity is improved with the increase of the layer number after 1.0-MeV C ion irradiation.

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Liquid-liquid phase transition in confined liquid titanium Di Zhang(张迪), Yunrui Duan(段云瑞), Peiru Zheng(郑培儒), Yingjie Ma(马英杰), Junping Qian(钱俊平), Zhichao Li(李志超), Jian Huang(黄建), Yanyan Jiang(蒋妍彦), and Hui Li(李辉) Chin. Phys. B, 2023, 32 (2):  026801.  DOI: 10.1088/1674-1056/ac6dc0 Abstract ( 356 )   HTML ( 2 )   PDF (4253KB) ( 127 )   We report the layering and liquid-liquid phase transition of liquid titanium confined between two parallel panel walls. Abnormal changes in the volume and the potential energy confirm the existence of the liquid-liquid phase transition of the liquid titanium. The typical feature of the liquid-liquid phase transition is layering, which is induced by the slit size, pressure and temperature. We highlight the fact that the slit size and pressure will determine the number of layers. In addition, with the change in the slit size, the density of the confined liquid expresses a fluctuating law. The phase diagram of the layering transition is drawn to clearly understand the layering. This study provides insights into the liquid-liquid phase transition of liquid metal in a confined space.

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Evolution of microstructure, stress and dislocation of AlN thick film on nanopatterned sapphire substrates by hydride vapor phase epitaxy Chuang Wang(王闯), Xiao-Dong Gao(高晓冬), Di-Di Li(李迪迪), Jing-Jing Chen(陈晶晶), Jia-Fan Chen(陈家凡), Xiao-Ming Dong(董晓鸣), Xiaodan Wang(王晓丹), Jun Huang(黄俊), Xiong-Hui Zeng(曾雄辉), and Ke Xu(徐科) Chin. Phys. B, 2023, 32 (2):  026802.  DOI: 10.1088/1674-1056/ac6865 Abstract ( 320 )   HTML ( 0 )   PDF (2859KB) ( 106 )   A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates (NPSSs) by hydride vapor phase epitaxy (HVPE). The coalescence, stress evolution, and dislocation annihilation mechanisms in the AlN layer have been investigated. The large voids located on the pattern region were caused by the undesirable parasitic crystallites grown on the sidewalls of the nano-pattern in the early growth stage. The coalescence of the c-plane AlN was hindered by these three-fold crystallites and the special triangle void appeared. The cross-sectional Raman line scan was used to characterize the change of stress with film thickness, which corresponds to the characteristics of different growth stages of AlN. Threading dislocations (TDs) mainly originate from the boundary between misaligned crystallites and the c-plane AlN and the coalescence of two adjacent c-plane AlN crystals, rather than the interface between sapphire and AlN.

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High repetition granular Co/Pt multilayers with improved perpendicular remanent magnetization for high-density magnetic recording Zhi Li(李智), Kun Zhang(张昆), Ao Du(杜奥), Hongchao Zhang(张洪超), Weibin Chen(陈伟斌), Ning Xu(徐宁), Runrun Hao(郝润润), Shishen Yan(颜世申), Weisheng Zhao(赵巍胜), and Qunwen Leng(冷群文) Chin. Phys. B, 2023, 32 (2):  026803.  DOI: 10.1088/1674-1056/ac9fc1 Abstract ( 313 )   HTML ( 0 )   PDF (2723KB) ( 186 )   Thanks to the strong perpendicular magnetic anisotropy (PMA), excellent processing compatibility as well as novel spintronic phenomenon, Co/Pt multilayers have been attracting massive attention and widely used in magnetic storage. However, reversed magnetic domains come into being with the increasing layer repetition ‘$N$’ to reduce magneto-static energy, resulting in the remarkable diminishment of the remanent magnetization ($M_{\rm r}$). As a result, the product of $M_{\rm r}$ and thickness ($i.e.$, the remanent moment-thickness product, $M_{\rm r}t$), a key parameter in magnetic recording for reliable data storing and reading, also decreases dramatically. To overcome this issue, we deposit an ultra-thick granular [Co/Pt]$_{80}$ multilayer with a total thickness of 68 nm on granular SiN$_{x}$ buffer layer. The $M_{\rm r}t$ value, $M_{\rm r}$ to saturation magnetization ($M_{\rm s}$) ratio as well as out of plane (OOP) coercivity ($H_{\rm coop}$) are high up to 2.97 memu/cm$^{2}$, 67%, and 1940 Oe (1 Oe = 79.5775 A$\cdot$m$^{-1}$), respectively, which is remarkably improved compared with that of continuous [Co/Pt]$_{80}$ multilayers. That is because large amounts of grain boundaries in the granular multilayers can efficiently impede the propagation and expansion of reversed magnetic domains, which is verified by experimental investigations and micromagnetic simulation results. The simulation results also indicate that the value of $M_{\rm r}t$, $M_{\rm r}/M_{\rm s}$ ratio, and $H_{\rm coop}$ can be further improved through optimizing the granule size, which can be experimentally realized by manipulating the process parameter of SiN$_{x}$ buffer layer. This work provides an alternative solution for achieving high $M_{\rm r}t$ value in ultra-thick Co/Pt multilayers, which is of unneglectable potential in applications of high-density magnetic recording.

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

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First-principles prediction of quantum anomalous Hall effect in two-dimensional Co2Te lattice Yuan-Shuo Liu(刘元硕), Hao Sun(孙浩), Chun-Sheng Hu(胡春生), Yun-Jing Wu(仵允京), and Chang-Wen Zhang(张昌文) Chin. Phys. B, 2023, 32 (2):  027101.  DOI: 10.1088/1674-1056/aca082 Abstract ( 367 )   HTML ( 3 )   PDF (2104KB) ( 358 )   The quantum anomalous Hall effect (QAHE) has special quantum properties that are ideal for possible future spintronic devices. However, the experimental realization is rather challenging due to its low Curie temperature and small non-trivial bandgap in two-dimensional (2D) materials. In this paper, we demonstrate through first-principles calculations that monolayer Co$_{2}$Te material is a promising 2D candidate to realize QAHE in practice. Excitingly, through Monte Carlo simulations, it is found that the Curie temperature of single-layer Co$_{2}$Te can reach 573 K. The band crossing at the Fermi level in monolayer Co$_{2}$Te is opened when spin-orbit coupling is considered, which leads to QAHE with a sizable bandgap of $E_{\rm g} = 96$ meV, characterized by the non-zero Chern number $\left( C = 1 \right)$ and a chiral edge state. Therefore, our findings not only enrich the study of quantum anomalous Hall effect, but also broaden the horizons of the spintronics and topological nanoelectronics applications.

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Mobility edges generated by the non-Hermitian flatband lattice Tong Liu(刘通) and Shujie Cheng(成书杰) Chin. Phys. B, 2023, 32 (2):  027102.  DOI: 10.1088/1674-1056/ac6581 Abstract ( 354 )   HTML ( 0 )   PDF (2323KB) ( 129 )   We study the cross-stitch flatband lattice subject to the quasiperiodic complex potential exp(ix). We firstly identify the exact expression of quadratic mobility edges through analytical calculation, then verify the theoretical predictions by numerically calculating the inverse participation ratio. Further more, we study the relationship between the real-complex spectrum transition and the localization-delocalization transition, and demonstrate that mobility edges in this non-Hermitian model not only separate localized from extended states but also indicate the coexistence of complex and real spectrum.

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Magnetic ground state of plutonium dioxide: DFT+U calculations Yue-Fei Hou(侯跃飞), Wei Jiang(江伟), Shu-Jing Li(李淑静), Zhen-Guo Fu(付振国), and Ping Zhang(张平) Chin. Phys. B, 2023, 32 (2):  027103.  DOI: 10.1088/1674-1056/ac9e96 Abstract ( 343 )   HTML ( 2 )   PDF (3996KB) ( 255 )   The magnetic states of the strongly correlated system plutonium dioxide (PuO$_{2}$) are studied based on the density functional theory (DFT) plus Hubbard $U$ (DFT$ + U$) method with spin-orbit coupling (SOC) included. A series of typical magnetic structures including the multiple-$k$ types are simulated and compared in the aspect of atomic structure and total energy. We test LDA, PBE, and SCAN exchange-correlation functionals on PuO$_{2}$ and a longitudinal $3k$ antiferromagnetic (AFM) ground state is theoretically determined. This magnetic structure has been identified to be the most stable one by the former computational work using the hybrid functional. Our DFT$ + U$$ + $SOC calculations for the longitudinal $3k$ AFM ground state suggest a direct gap which is in good agreement with the experimental value. In addition, a genetic algorithm is employed and proved to be effective in predicting magnetic ground state of PuO$_{2}$. Finally, a comparison between the results of two extensively used DFT$ + U$ approaches to this system is made.

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Blue phosphorene/MoSi2N4 van der Waals type-II heterostructure: Highly efficient bifunctional materials for photocatalytics and photovoltaics Xiaohua Li(李晓华), Baoji Wang(王宝基), and Sanhuang Ke(柯三黄) Chin. Phys. B, 2023, 32 (2):  027104.  DOI: 10.1088/1674-1056/ac9469 Abstract ( 286 )   HTML ( 0 )   PDF (2134KB) ( 56 )   Converting solar energy into electric power or hydrogen fuel is a promising means to obtain renewable green energy. Here, we design a two-dimensional blue phosphorene (BlueP)/MoSi$_2$N$_4$ van der Waals heterostructure (vdWH) and investigate its potential application in photocatalysis and photovoltaics using first-principles calculations. We find that the BlueP/MoSi$_2$N$_4$ vdWH possesses type-II band structure with a large build-in electric field, thus endowing it with a potential ability to separate photogenerated electron-hole pairs. The calculated band-edge positions show that the heterostructure is a very promising water-splitting photocatalyst. Its solar-to-hydrogen efficiency ($\eta_{ \text{STH}}$) can reach up to 15.8%, which is quite promising for commercial applications. Furthermore, the BlueP/MoSi$_2$N$_4$ vdWH shows remarkably light absorption capacity and distinguished maximum power conversion efficiency ($\eta_{\text{PCE}}$) up to 10.61%. Remarkably, its $\eta_{\text{PCE}}$ can be further enhanced by the external strain: the $\eta_{\text{PCE}}$ of 21.20% can be obtained under a 4% tensile strain. Finally, we determine that adjusting the number of the BlueP sublayer is another effective method to modulate the band gaps and band alignments of the heterostructures. These theoretical findings indicate that BlueP/MoSi$_2$N$_4$ vdWH is a promising candidate for photocatalyst and photovoltaic device.

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A novel monoclinic phase and electrically tunable magnetism of van der Waals layered magnet CrTe2 Hot! Qidi Ren(任启迪), Kang Lai(赖康), Jiahao Chen(陈家浩), Xiaoxiang Yu(余晓翔), and Jiayu Dai(戴佳钰) Chin. Phys. B, 2023, 32 (2):  027201.  DOI: 10.1088/1674-1056/ac9b37 Abstract ( 553 )   HTML ( 5 )   PDF (1943KB) ( 408 )   Exploring the novel structural phase of van der Waals (vdW) magnets would promote the development of spintronics. Here, through first-principles calculations, we report a novel monoclinic structure of vdW layered 1T-CrTe2, which is one of the popular vdW magnets normally exhibiting a trigonal structure. The new monoclinic phase emerges from a switchable magnetic state between ferromagnetism and antiferromagnetism through changing hole doping concentration, which suggests a practical approach to obtain such a structure. The results of phonon dispersion and energy analysis convince us that the monoclinic structure is a metastable phase even without hole doping. When the hole doping concentration increases, the stability analysis indicates the preference for a novel monoclinic phase rather than a conventional trigonal phase, and meanwhile, the magnetic properties are accordingly tuned. This work provides new insights into the phase engineering of the chalcogenide family and the electrical control of magnetism of vdW layered magnets.

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Chiral symmetry protected topological nodal superconducting phase and Majorana Fermi arc Mei-Ling Lu(卢美玲), Yao Wang(王瑶), He-Zhi Zhang(张鹤之), Hao-Lin Chen(陈昊林), Tian-Yuan Cui(崔天元), and Xi Luo(罗熙) Chin. Phys. B, 2023, 32 (2):  027301.  DOI: 10.1088/1674-1056/ac7208 Abstract ( 367 )   HTML ( 0 )   PDF (1552KB) ( 202 )   With an external in-plane magnetic field, we show the emergence of a topological nodal superconducting phase of the two-dimensional topological surface states. This nodal superconducting phase is protected by the chiral symmetry with a non-zero magnetic field, and there are corresponding Majorana Fermi arcs (also known as flat band Andreev bound states) connecting the two Majorana nodes along the edges, similar to the case of Weyl semimetal. The topological nodal superconductor is an intermediate phase between two different chiral superconductors, and is stable against the effects of substrates. The two-dimensional effective theory of the nodal superconducting phase also captures the low energy behavior of a three-dimensional lattice model which describes the iron-based superconductor with a thin film geometry. The localizations of the Majorana nodes can be manipulated through external in-plane magnetic fields, which may introduce a non-trivial topological Berry phase between them.

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Demonstration and modeling of unipolar-carrier-conduction GaN Schottky-pn junction diode with low turn-on voltage Lijian Guo(郭力健), Weizong Xu(徐尉宗), Qi Wei(位祺), Xinghua Liu(刘兴华), Tianyi Li(李天义), Dong Zhou(周东), Fangfang Ren(任芳芳), Dunjun Chen(陈敦军), Rong Zhang(张荣), Youdou Zheng(郑有炓), and Hai Lu(陆海) Chin. Phys. B, 2023, 32 (2):  027302.  DOI: 10.1088/1674-1056/ac81ad Abstract ( 339 )   HTML ( 2 )   PDF (726KB) ( 215 )   By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode (SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conduction characteristic is demonstrated by the verification of temperature-dependent current-voltage (I-V) tests and electroluminescence spectra. Meanwhile, apparently advantageous forward conduction properties as compared to the pn diode fabricated on the same wafer have been achieved, featuring a lower turn-on voltage of 0.82 V. Together with the analysis model established in the GaN SPND for a wide-range designable turn-on voltage, this work provides an alternative method to the GaN rectifier strategies besides the traditional solution.

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Effect of thickness on magnetic properties of single domain GdBCO bulk superconductors Ping Gao(高平), Wan-Min Yang(杨万民), Ting-Ting Wu(武婷婷), Miao Wang(王妙), and Kun Liu(刘坤) Chin. Phys. B, 2023, 32 (2):  027401.  DOI: 10.1088/1674-1056/ac7a13 Abstract ( 289 )   HTML ( 0 )   PDF (2421KB) ( 78 )   To study the influence of thickness on the magnetic properties of ReBCO (Re=Y, Gd, Sm, Nd, etc.) bulk superconductors, a single domain gadolinium barium copper oxide (GdBCO) bulk superconductor fabricated by the Re+ 011 top seeded infiltration growth (Re+ 011 TSIG) method was continuously sliced along the bottom to obtain samples of different thickness. The levitation force and attractive force of these samples were tested at 77 K in the zero-field-cooled (ZFC) state. It is found that as the sample thickness decreases, the levitation force decreases gradually whereas the attractive force increases. This is related to the varied ability to resist the penetration of magnetic field occasioned by varying sample thickness, which are deeply revealed by combining with the characteristics of the non-ideal type-I!I superconductor. Further, the levitation force exhibits a trend of slow initial change followed by rapid change, which may be attributed to the growth of the sample. Measurement of the trapped field shows that a similar distribution of trapped field at the top and bottom surfaces can be achieved by removing some materials from the bottom of the bulk. These results provide a reference for meeting the actual requirements of ReBCO bulks of different thicknesses and greatly contribute to practical designs and applications.

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Magnetocaloric properties of phenolic resin bonded La(Fe,Si)13-based plates and its use in a hybrid magnetic refrigerator Shao-Shan Xu(徐少山), Qi Fu(付琪), Yi-Fan Zhou(周益帆), Ling Peng(彭铃), Xin-Qiang Gao(高新强), Zhen-Xing Li(李振兴), Mao-Qiong Gong(公茂琼), Xue-Qiang Dong(董学强), and Jun Shen(沈俊) Chin. Phys. B, 2023, 32 (2):  027502.  DOI: 10.1088/1674-1056/ac9fbf Abstract ( 347 )   HTML ( 0 )   PDF (2192KB) ( 147 )   We present a simple hot press-based method for processing La(Fe,Si)$_{13}$-based compounds consisting of La-Fe-Co-Si-C particles and phenolic resin. The magnetic entropy change $\Delta S$ per unit mass for the LaFe$_{10.87}$Co$_{0.63}$Si$_{1.5}$C$_{0.2}$/phenolic resin compounds have nearly the same magnitude with the base materials. With the content of phenolic resin of 5.0 wt%, the compound conductivity is 3.13 W$\cdot$m$^{-1}\cdot$K$^{-1}$. In order to measure the cooling performance of La(Fe,Si)$_{13}$-based compounds, the La(Fe$_{11.6-x}$Co$_{x}$)Si$_{1.4}$C$_{0.15}$ ($x=$0.60, 0.65, 0.75, 0.80, 0.85)/phenolic resin compounds were pressed into thin plates and tested in a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect. The test results showed that a maximum cooling power of 41 W was achieved over a temperature span of 30 K.

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Giant low-field cryogenic magnetocaloric effect in polycrystalline LiErF4 compound Zhaojun Mo(莫兆军), Jianjian Gong(巩建建), Huicai Xie(谢慧财), Lei Zhang(张磊), Qi Fu(付琪), Xinqiang Gao(高新强), Zhenxing Li(李振兴), and Jun Shen(沈俊) Chin. Phys. B, 2023, 32 (2):  027503.  DOI: 10.1088/1674-1056/ac65ef Abstract ( 434 )   HTML ( 1 )   PDF (920KB) ( 244 )   Antiferromagnetic LiErF4 has attracted extensive attention due to its dipolar interaction domination and quantum fluctuations action. In the present work, the crystal structure, cryogenic magnetic properties, and magnetocaloric effect (MCE) of polycrystalline LiErF4 compound are investigated. Crystallographic study shows that the compound crystallizes in the tetragonal scheelite structure with I41/a space group. It exhibits an antiferromagnetic (AFM) phase transition around 0.4 K, accompanied by a giant cryogenic MCE. At 1.3 K, the maximum values of magnetic entropy changes are 24.3 J/kg·K, 33.1 J/kg·K, and 49.0 J/kg·K under the low magnetic field change of 0-0.6 T, 0-1 T, and 0-2 T, respectively. The giant MCE observed above Néel temperature TN is probably due to the strong quantum fluctuations, which cause a large ratio of the unreleased magnetic entropy existing above the phase transition temperature. The outstanding low-field MCE below 2 K makes the LiErF4 compound an attractive candidate for the magnetic refrigeration at the ultra-low temperature.

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Charge-mediated voltage modulation of magnetism in Hf0.5Zr0.5O2/Co multiferroic heterojunction Jia Chen(陈佳), Peiyue Yu(于沛玥), Lei Zhao(赵磊), Yanru Li(李彦如), Meiyin Yang(杨美音), Jing Xu(许静), Jianfeng Gao(高建峰), Weibing Liu(刘卫兵), Junfeng Li(李俊峰), Wenwu Wang(王文武), Jin Kang(康劲), Weihai Bu(卜伟海), Kai Zheng(郑凯), Bingjun Yang(杨秉君), Lei Yue(岳磊), Chao Zuo(左超), Yan Cui(崔岩), and Jun Luo(罗军) Chin. Phys. B, 2023, 32 (2):  027504.  DOI: 10.1088/1674-1056/ac9a3b Abstract ( 391 )   HTML ( 4 )   PDF (2742KB) ( 177 )   We construct the Hall-bar device with the size of several hundred nanometers based on the HZO/Co multiferroic heterojunction. A remarkable voltage-controlled magnetism is observed in the device that possesses both ferroelectric property and perpendicular magnetic anisotropy (PMA). The nucleation field and coercivity can be modulated by voltage pulse while saturation field keeps stable. The non-volatile and reversible voltage-controlled magnetism is ascribable to interfacial charges caused by ferroelectric polarization. Meanwhile, the effective anisotropy energy density (Ku) can also be controlled by voltage pulse, a decrease of 83% and increase of 28% in Ku are realized under -3-V and 3-V pulses, respectively. Because the energy barrier is directly proportional to Ku under a given volume, a decreased or enhanced energy barrier can be controlled by voltage pulse. Thus, it is an effective method to realize low-power and high-stability magneto-resistive random-access memory (MRAM).

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Graphene metasurface-based switchable terahertz half-/quarter-wave plate with a broad bandwidth Xiaoqing Luo(罗小青), Juan Luo(罗娟), Fangrong Hu(胡放荣), and Guangyuan Li(李光元) Chin. Phys. B, 2023, 32 (2):  027801.  DOI: 10.1088/1674-1056/ac80a8 Abstract ( 474 )   HTML ( 3 )   PDF (988KB) ( 308 )   Metasurfaces incorporating graphene hold great promise for the active manipulation of terahertz waves. However, it remains challenging to design a broadband graphene-based terahertz metasurface with switchable functionality of half-wave plate (HWP) and quarter-wave plate (QWP). Here, we propose a graphene-metal hybrid metasurface for achieving broadband switchable HWP/QWP in the terahertz regime. Simulation results show that, by varying the Fermi energy of graphene from 0 eV to 1 eV, the function of the reflective metasurface can be switched from an HWP with polarization conversion ratio exceeding 97% over a wide band ranging from 0.7 THz to 1.3 THz, to a QWP with ellipticity above 0.92 over 0.78 THz-1.33 THz. The sharing bandwidth reaches up to 0.52 THz and the relative bandwidth is as high as 50%. We expect this broadband and dynamically switchable terahertz HWP/QWP will find applications in terahertz sensing, imaging, and telecommunications.

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Effect of thickness of antimony selenide film on its photoelectric properties and microstructure Xin-Li Liu(刘欣丽), Yue-Fei Weng(翁月飞), Ning Mao(毛宁), Pei-Qing Zhang(张培晴), Chang-Gui Lin(林常规), Xiang Shen(沈祥), Shi-Xun Dai(戴世勋), and Bao-An Song(宋宝安) Chin. Phys. B, 2023, 32 (2):  027802.  DOI: 10.1088/1674-1056/ac8724 Abstract ( 321 )   HTML ( 2 )   PDF (3724KB) ( 212 )   Antimony selenide (Sb2Se3) films are widely used in phase change memory and solar cells due to their stable switching effect and excellent photovoltaic properties. These properties of the films are affected by the film thickness. A method combining the advantages of Levenberg-Marquardt method and spectral fitting method (LM-SFM) is presented to study the dependence of refractive index (RI), absorption coefficient, optical band gap, Wemple-DiDomenico parameters, dielectric constant and optical electronegativity of the Sb2Se3 films on their thickness. The results show that the RI and absorption coefficient of the Sb2Se3 films increase with the increase of film thickness, while the optical band gap decreases with the increase of film thickness. Finally, the reasons why the optical and electrical properties of the film change with its thickness are explained by x-ray diffractometer (XRD), energy dispersive x-ray spectrometer (EDS), Mott-Davis state density model and Raman microstructure analysis.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Influence of the lattice parameter of the AlN buffer layer on the stress state of GaN film grown on (111) Si Zhen-Zhuo Zhang(张臻琢), Jing Yang(杨静), De-Gang Zhao(赵德刚), Feng Liang(梁锋), Ping Chen(陈平), and Zong-Shun Liu(刘宗顺) Chin. Phys. B, 2023, 32 (2):  028101.  DOI: 10.1088/1674-1056/ac6b2b Abstract ( 381 )   HTML ( 0 )   PDF (1419KB) ( 281 )   GaN films grown on (111) Si substrate with different lattice parameters of the AlN buffer layer by metal-organic chemical vapor deposition are studied. The stress states obtained by different test methods are compared and it is found that the lattice parameter of the AlN buffer layer may have a significant effect on the stress state in the initial stage of subsequent GaN film growth. A larger compressive stress is beneficial to improved surface morphology and crystal quality of GaN film. The results of further orthogonal experiments show that an important factor affecting the lattice parameter is the growth rate of the AlN buffer layer. This work may be helpful for realizing simple GaN-on-Si structures and thus reducing the costs of growth processes.

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Effects of π-conjugation-substitution on ESIPT process for oxazoline-substituted hydroxyfluorenes Di Wang(汪迪), Qiao Zhou(周悄), Qiang Wei(魏强), and Peng Song(宋朋) Chin. Phys. B, 2023, 32 (2):  028201.  DOI: 10.1088/1674-1056/ac65f4 Abstract ( 315 )   HTML ( 1 )   PDF (2413KB) ( 99 )   Excited-state intramolecular proton transfer (ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydroxyfluorenes and hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory (DFT) and time-dependent DFT (TDDFT) are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals (FMOs) isosurfaces, and O-H stretching vibration frequency analysis demonstrate that PT processes are more active in S1 state. Constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of naphthoxazole (NO-OH) is distinctly bathochromic-shift relative to the oxazoline-substituted hydroxyfluorenes (Oxa-OH) configuration when adding π-conjugation-substitution, and it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules.

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Memristor's characteristics: From non-ideal to ideal Fan Sun(孙帆), Jing Su(粟静), Jie Li(李杰), Shukai Duan(段书凯), and Xiaofang Hu(胡小方) Chin. Phys. B, 2023, 32 (2):  028401.  DOI: 10.1088/1674-1056/ac7548 Abstract ( 315 )   HTML ( 0 )   PDF (1313KB) ( 211 )   Memristor has been widely studied in the field of neuromorphic computing and is considered to be a strong candidate to break the von Neumann bottleneck. However, the non-ideal characteristics of memristor seriously limit its practical application. There are two sides to everything, and memristors are no exception. The non-ideal characteristics of memristors may become ideal in some applications. Genetic algorithm (GA) is a method to search for the optimal solution by simulating the process of biological evolution. It is widely used in the fields of machine learning, combinatorial optimization, and signal processing. In this paper, we simulate the biological evolutionary behavior in GA by using the non-ideal characteristics of memristors, based on which we design peripheral circuits and path planning algorithms based on memristor networks. The experimental results show that the non-ideal characteristics of memristor can well simulate the biological evolution behavior in GA.

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Transition-edge sensors using Mo/Au/Au tri-layer films Hubing Wang(王沪兵), Yue Lv(吕越), Dongxue Li(李冬雪), Yue Zhao(赵越), Bo Gao(高波), and Zhen Wang(王镇) Chin. Phys. B, 2023, 32 (2):  028501.  DOI: 10.1088/1674-1056/ac7f94 Abstract ( 334 )   HTML ( 1 )   PDF (1807KB) ( 119 )   The proximity effect to reduce the transition temperature of a superconducting film is frequently used in transition-edge sensors. Here, we develop these transition-edge sensors using Mo/Au/Au tri-layer films to detect soft x-rays. They are equipped with an overhanging photon absorber. We reduce the fabrication complexity by integrating the sensor patterning with the tri-layer film formation. We determine the electro-thermal parameters of the sensors through a series of resistance vs. temperature and current vs. voltage measurements. We also demonstrate their energy-resolving capability by using a 55Fe radioactive x-ray source. The best energy resolution was approximately 6.66 eV at 5.9 keV, with a theoretical count rate of 500 Hz.

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Enhancement of holding voltage by a modified low-voltage trigger silicon-controlled rectifier structure for electrostatic discharge protection Yuankang Chen(陈远康), Yuanliang Zhou(周远良), Jie Jiang(蒋杰), Tingke Rao(饶庭柯), Wugang Liao(廖武刚), and Junjie Liu(刘俊杰) Chin. Phys. B, 2023, 32 (2):  028502.  DOI: 10.1088/1674-1056/ac7b1d Abstract ( 377 )   HTML ( 1 )   PDF (902KB) ( 424 )   A novel structure of low-voltage trigger silicon-controlled rectifiers (LVTSCRs) with low trigger voltage and high holding voltage is proposed for electrostatic discharge (ESD) protection. The proposed ESD protection device possesses an ESD implant and a floating structure. This improvement enhances the current discharge capability of the gate-grounded NMOS and weakens the current gain of the silicon-controlled rectifier current path. According to the simulation results, the proposed device retains a low trigger voltage characteristic of LVTSCRs and simultaneously increases the holding voltage to 5.53 V, providing an effective way to meet the ESD protection requirement of the 5 V CMOS process.

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High performance SiC trench-type MOSFET with an integrated MOS-channel diode Jie Wei(魏杰), Qinfeng Jiang(姜钦峰), Xiaorong Luo(罗小蓉), Junyue Huang(黄俊岳), Kemeng Yang(杨可萌), Zhen Ma(马臻), Jian Fang(方健), and Fei Yang(杨霏) Chin. Phys. B, 2023, 32 (2):  028503.  DOI: 10.1088/1674-1056/ac7cd5 Abstract ( 488 )   HTML ( 6 )   PDF (1793KB) ( 481 )   A novel SiC double-trench metal-oxide-semiconductor field effect transistor (MOSFET) with integrated MOS-channel diode is proposed and investigated by Sentaurus TCAD simulation. The new SiC MOSFET has a trench gate and a stepped-trench source, and features an integrated MOS-channel diode on the top sidewall of the source trench (MT MOS). In the reverse conduction state, the MOS-channel diode turns on firstly to prevent the internal parasitic body diode being activated, and thus reduces the turn-on voltage $V_{\rm F}$ and suppresses the bipolar degradation phenomena. The $V_{\rm F}$ of 1.70 V (@$I_{\rm ds} = -100$ A/cm$^{2}$) for the SiC MT MOS is 38.2% lower than that of SiC double-trench MOSFET (DT MOS). Meanwhile, the reverse recovery charge $Q_{\rm rr}$ of the MT MOS is 58.7% lower than that of the DT MOS at $I_{\rm load} = 700$ A/cm$^{2}$, and thus the reverse recovery loss is reduced. Furthermore, owing to the modulation effect induced by the double trenches, the MT MOS preserves the same superior forward conduction and blocking performance as those of DT MOS, with 22.9% and 18.2% improvement on breakdown voltage and $R_{\rm ON,sp}$ compared to the trench gate MOSFET with planar integrated SBD (ST MOS).

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Experiment and simulation on degradation and burnout mechanisms of SiC MOSFET under heavy ion irradiation Hong Zhang(张鸿), Hongxia Guo(郭红霞), Zhifeng Lei(雷志锋), Chao Peng(彭超), Zhangang Zhang(张战刚), Ziwen Chen(陈资文), Changhao Sun(孙常皓), Yujuan He(何玉娟), Fengqi Zhang(张凤祁), Xiaoyu Pan(潘霄宇), Xiangli Zhong(钟向丽), and Xiaoping Ouyang(欧阳晓平) Chin. Phys. B, 2023, 32 (2):  028504.  DOI: 10.1088/1674-1056/ac8cda Abstract ( 416 )   HTML ( 2 )   PDF (1582KB) ( 244 )   Experiments and simulation studies on 283 MeV I ion induced single event effects of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) were carried out. When the cumulative irradiation fluence of the SiC MOSFET reached 5×106 ion·cm-2, the drain-gate channel current increased under 200 V drain voltage, the drain-gate channel current and the drain-source channel current increased under 350 V drain voltage. The device occurred single event burnout under 800 V drain voltage, resulting in a complete loss of breakdown voltage. Combined with emission microscope, scanning electron microscope and focused ion beam analysis, the device with increased drain-gate channel current and drain-source channel current was found to have drain-gate channel current leakage point and local source metal melt, and the device with single event burnout was found to have local melting of its gate, source, epitaxial layer and substrate. Combining with Monte Carlo simulation and TCAD electrothermal simulation, it was found that the initial area of single event burnout might occur at the source-gate corner or the substrate-epitaxial interface, electric field and current density both affected the lattice temperature peak. The excessive lattice temperature during the irradiation process appeared at the local source contact, which led to the drain-source channel damage. And the excessive electric field appeared in the gate oxide layer, resulting in drain-gate channel damage.

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Analysis of refraction and scattering image artefacts in x-ray analyzer-based imaging Li-Ming Zhao(赵立明), Tian-Xiang Wang(王天祥), Run-Kang Ma(马润康), Yao Gu(顾瑶), Meng-Si Luo(罗梦丝), Heng Chen(陈恒), Zhi-Li Wang(王志立), and Xin Ge(葛昕) Chin. Phys. B, 2023, 32 (2):  028701.  DOI: 10.1088/1674-1056/ac685d Abstract ( 317 )   HTML ( 2 )   PDF (1729KB) ( 113 )   X-ray analyzer-based imaging (ABI) is a powerful phase-sensitive technique that can provide a wide dynamic range of density and extract useful physical properties of the sample. It derives contrast from x-ray absorption, refraction, and scattering properties of the investigated sample. However, x-ray ABI setups can be susceptible to external vibrations, and mechanical imprecisions of system components, e.g., the precision of motor, which are unavoidable in practical experiments. Those factors will provoke deviations of analyzer angular positions and hence errors in the acquired image data. Consequently, those errors will introduce artefacts in the retrieved refraction and scattering images. These artefacts are disadvantageous for further image interpretation and tomographic reconstruction. For this purpose, this work aims to analyze image artefacts resulting from deviations of analyzer angular positions. Analytical expressions of the refraction and scattering image artefacts are derived theoretically and validated by synchrotron radiation experiments. The results show that for the refraction image, the artefact is independent of the sample's absorption and scattering signals. By contrast, artefact of the scattering image is dependent on both the sample's refraction and scattering signals, but not on absorption signal. Furthermore, the effect of deviations of analyzer angular positions on the accuracy of the retrieved images is investigated, which can be of use for optimization of data acquisition. This work offers the possibility to develop advanced multi-contrast image retrieval algorithms that suppress artefacts in the retrieved refraction and scattering images in x-ray analyzer-based imaging.

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Heterogeneous hydration patterns of G-quadruplex DNA Cong-Min Ji(祭聪敏), Yusong Tu(涂育松), and Yuan-Yan Wu(吴园燕) Chin. Phys. B, 2023, 32 (2):  028702.  DOI: 10.1088/1674-1056/ac7452 Abstract ( 249 )   HTML ( 0 )   PDF (797KB) ( 93 )   G-quadruplexes (GQs) are guanine-rich, non-canonical nucleic acid structures that play fundamental roles in biological processes. Their structure and function are strongly influenced by their hydration shells. Although extensively studied through various experimental and computational methods, hydration patterns near DNA remain under debate due to the chemically and topologically heterogeneous nature of the exposed surface. In this work, we employed all-atom molecular dynamics (MD) simulation to study the hydration patterns of GQ DNA. The Drude oscillator model was used in MD simulation as a computationally efficient method for modeling electronic polarization in DNA ion solutions. Hydration structure was analyzed in terms of radial distribution functions and high-density three-dimensional hydration sites. Analysis of hydration dynamics focused on self-diffusion rates and orientation time correlation at different structural regions of GQ DNA. The results show highly heterogeneous hydration patterns in both structure and dynamics; for example, there are several insular high-density sites in the inner channel, and ‘spine of water’ in the groove. For water inside the loop, anomalous diffusion is present over a long time scale, but for water around the phosphate group and groove, diffusion becomes normal after ～ 30 ps. These essentially correspond to deeply buried structural water and strong interaction with DNA, respectively.

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Thermally enhanced photoluminescence and temperature sensing properties of Sc2W3O12:Eu3+ phosphors Yu-De Niu(牛毓德), Yu-Zhen Wang(汪玉珍), Kai-Ming Zhu(朱凯明), Wang-Gui Ye(叶王贵), Zhe Feng(冯喆), Hui Liu(柳挥), Xin Yi(易鑫), Yi-Huan Wang(王怡欢), and Xuan-Yi Yuan(袁轩一) Chin. Phys. B, 2023, 32 (2):  028703.  DOI: 10.1088/1674-1056/ac70b8 Abstract ( 323 )   HTML ( 2 )   PDF (3455KB) ( 189 )   Recently, lanthanide-ion-doped luminescent materials have been extensively used as optical thermometry probes due to their fast responses, non-contact, and high sensitivity properties. Based on different responses of two emissions to temperature, the fluorescence intensity ratio (FIR) technique can be used to estimate the sensitivities for assessing the optical thermometry performances. In this study, we introduce different doping concentrations of Eu$^{3+}$ ions into negative thermal expansion material Sc$_{2}$W$_{3}$O$_{12}$ to increase the thermal-enhanced luminescence from 373 K to 548 K, and investigate the temperature sensing properties in detail. All samples can exhibit their good luminescence behaviors thermally enhanced. The emission intensity of Sc$_{2}$W$_{3}$O$_{12}$:6-mol% Eu$^{3+}$ phosphor reaches 147.8% of initial intensity at 473 K. As the Eu$^{3+}$ doping concentration increases, the resistance of the sample to thermal quenching decreases. The FIR technique based on each of the transitions $^{5}$D$\to {}^{7}$F$_{1}$ (592 nm) and $^{5}$D$\to ^{7}$F$_{2 }$ (613 nm) of Eu$^{3+}$ ions demonstrates a maximum relative temperature sensitivity of 3.063% K$^{-1}$ at 298 K for Sc$_{2}$W$_{3}$O$_{12}$:6-mol% Eu$^{3+}$ phosphor. The sensitivity of sample decreases with the increase of Eu$^{3+}$ concentration. Benefiting from the thermal-enhanced luminescence performance and good temperature sensing properties, the Sc$_{2}$W$_{3}$O$_{12}$:Eu$^{3+}$ phosphors can be used as optical thermometers.

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Micro-mechanism study of the effect of Cd-free buffer layers ZnXO (X=Mg/Sn) on the performance of flexible Cu2ZnSn(S, Se)4 solar cell Caixia Zhang(张彩霞), Yaling Li(李雅玲), Beibei Lin(林蓓蓓), Jianlong Tang(唐建龙), Quanzhen Sun(孙全震), Weihao Xie(谢暐昊), Hui Deng(邓辉), Qiao Zheng(郑巧), and Shuying Cheng(程树英) Chin. Phys. B, 2023, 32 (2):  028801.  DOI: 10.1088/1674-1056/ac9b3a Abstract ( 365 )   HTML ( 1 )   PDF (1049KB) ( 220 )   The traditional CdS buffer layers in flexible CZTSSe solar cells lead to light absorption losses and environmental pollution problems. Therefore, the study of Cd-free buffer layer is very important for the realization of environmentally friendly and efficient CZTSSe solar cells. The Zn$_{1-x}$Mg$_{x}$O (ZnMgO) and Zn$_{1-x}$Sn$_{x}$O (ZnSnO) alternate buffer layers are studied in this study using the simulation package solar cell capacitance simulator (SCAPS-1D) numerical simulation model, and the theoretical analysis is further verified by the results of the experiments. We simulate the performance of CZTSSe/Zn$X$O ($X={\rm Mg/Sn}$) heterojunction devices with different Mg/(Zn$+$Mg) and Sn/(Zn$+$Sn) ratios and analyze the intrinsic mechanism of the effect of conduction band offsets (CBO) on the device performance. The simulation results show that the CZTSSe/Zn$X$O ($X={\rm Mg/Sn}$) devices achieve optimal performance with a small "spike" band or "flat" band at Mg and Sn doping concentrations of 0.1 and 0.2, respectively. To investigate the potential of Zn$_{0.9}$Mg$_{0.1}$O and Zn$_{0.8}$Sn$_{0.2}$O as alternative buffer layers, carrier concentrations and thicknesses are analyzed. The simulation demonstrates that the Zn$_{0.9}$Mg$_{0.1}$O device with low carrier concentration has a high resistivity, serious carrier recombination, and a greater impact on performance from thickness variation. Numerical simulations and experimental results show the potential of the ZnSnO buffer layer as an alternative to toxic CdS, and the ZnMgO layer has the limitation as a substitute buffer layer. This paper provides the theoretical basis and experimental proof for further searching for a suitable flexible CZTSSe Cd-free buffer layer.

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Investigating the characteristic delay time in the leader-follower behavior in children single-file movement Shu-Qi Xue(薛书琦), Nirajan Shiwakoti, Xiao-Meng Shi(施晓蒙), and Yao Xiao(肖尧) Chin. Phys. B, 2023, 32 (2):  028901.  DOI: 10.1088/1674-1056/ac80b1 Abstract ( 333 )   HTML ( 1 )   PDF (1343KB) ( 184 )   The single-file movement experiment offered a convenient way to investigate the one-dimensional leader-follower behavior of pedestrians. This study investigated the time delays of children pedestrians in the leader-follower behavior by introducing a time-dependent delayed speed correlation. A total of 118 German students from the fifth grade (aged 11-12 years old) and the 11th grade (aged 17-18 years old) participated the single-file experiment. The characteristic delay time for each pedestrian was identified by optimising the time-dependent delayed speed correlation. The influences of the curvature of the experimental scenario, density, age, and gender on the delay time were statistically examined. The results suggested that to a large extent, the revealed characteristic delay time was a density-dependent variable, and none of the curvatures, the age and gender of the individual, and the age and gender of the leader had a significant influence on it. The findings from this study are variable resources to understand the leader-follower behavior among children pedestrians and to build related simulation models.

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Analysis of cut vertex in the control of complex networks Jie Zhou(周洁), Cheng Yuan(袁诚), Zu-Yu Qian(钱祖燏), Bing-Hong Wang(汪秉宏), and Sen Nie(聂森) Chin. Phys. B, 2023, 32 (2):  028902.  DOI: 10.1088/1674-1056/aca208 Abstract ( 339 )   HTML ( 0 )   PDF (635KB) ( 91 )   The control of complex networks is affected by their structural characteristic. As a type of key nodes in a network structure, cut vertexes are essential for network connectivity because their removal will disconnect the network. Despite their fundamental importance, the influence of the cut vertexes on network control is still uncertain. Here, we reveal the relationship between the cut vertexes and the driver nodes, and find that the driver nodes tend to avoid the cut vertexes. However, driving cut vertexes reduce the energy required for controlling complex networks, since cut vertexes are located near the middle of the control chains. By employing three different node failure strategies, we investigate the impact of cut vertexes failure on the energy required. The results show that cut vertex failures markedly increase the control energy because the cut vertexes are larger-degree nodes. Our results deepen the understanding of the structural characteristic in network control.