Table of contents

    14 May 2022, Volume 31 Issue 5 Previous issue    Next issue
    A nonlocal Boussinesq equation: Multiple-soliton solutions and symmetry analysis
    Xi-zhong Liu(刘希忠) and Jun Yu(俞军)
    Chin. Phys. B, 2022, 31 (5):  050201.  DOI: 10.1088/1674-1056/ac43a7
    Abstract ( 336 )   HTML ( 3 )   PDF (2844KB) ( 116 )  
    A nonlocal Boussinesq equation is deduced from the local one by using consistent correlated bang method. To study various exact solutions of the nonlocal Boussinesq equation, it is converted into two local equations which contain the local Boussinesq equation. From the N-soliton solutions of the local Boussinesq equation, the N-soliton solutions of the nonlocal Boussinesq equation are obtained, among which the (N=2,3,4)-soliton solutions are analyzed with graphs. Some periodic and traveling solutions of the nonlocal Boussinesq equation are derived directly from the known solutions of the local Boussinesq equation. Symmetry reduction solutions of the nonlocal Boussinesq equation are also obtained by using the classical Lie symmetry method.
    Correlation and trust mechanism-based rumor propagation model in complex social networks
    Xian-Li Sun(孙先莉), You-Guo Wang(王友国), and Lin-Qing Cang(仓林青)
    Chin. Phys. B, 2022, 31 (5):  050202.  DOI: 10.1088/1674-1056/ac3d82
    Abstract ( 324 )   HTML ( 1 )   PDF (2367KB) ( 131 )  
    In real life, the rumor propagation is influenced by many factors. The complexity and uncertainty of human psychology make the diffusion model more challenging to depict. In order to establish a comprehensive propagation model, in this paper, we take some psychological factors into consideration to mirror rumor propagation. Firstly, we use the Ridenour model to combine the trust mechanism with the correlation mechanism and propose a modified rumor propagation model. Secondly, the mean-field equations which describe the dynamics of the modified SIR model on homogenous and heterogeneous networks are derived. Thirdly, a steady-state analysis is conducted for the spreading threshold and the final rumor size. Fourthly, we investigate rumor immunization strategies and obtain immunization thresholds. Next, simulations on different networks are carried out to verify the theoretical results and the effectiveness of the immunization strategies. The results indicate that the utilization of trust and correlation mechanisms leads to a larger final rumor size and a smaller terminal time. Moreover, different immunization strategies have disparate effectiveness in rumor propagation.
    Gauss quadrature based finite temperature Lanczos method Hot!
    Jian Li(李健) and Hai-Qing Lin(林海青)
    Chin. Phys. B, 2022, 31 (5):  050203.  DOI: 10.1088/1674-1056/ac5986
    Abstract ( 586 )   HTML ( 4 )   PDF (782KB) ( 451 )  
    The finite temperature Lanczos method (FTLM), which is an exact diagonalization method intensively used in quantum many-body calculations, is formulated in the framework of orthogonal polynomials and Gauss quadrature. The main idea is to reduce finite temperature static and dynamic quantities into weighted summations related to one- and two-dimensional Gauss quadratures. Then lower order Gauss quadrature, which is generated from Lanczos iteration, can be applied to approximate the initial weighted summation. This framework fills the conceptual gap between FTLM and kernel polynomial method, and makes it easy to apply orthogonal polynomial techniques in the FTLM calculation.
    Experimental realization of quantum controlled teleportation of arbitrary two-qubit state via a five-qubit entangled state
    Xiao-Fang Liu(刘晓芳), Dong-Fen Li(李冬芬), Yun-Dan Zheng(郑云丹), Xiao-Long Yang(杨小龙), Jie Zhou(周杰), Yu-Qiao Tan(谭玉乔), and Ming-Zhe Liu(刘明哲)
    Chin. Phys. B, 2022, 31 (5):  050301.  DOI: 10.1088/1674-1056/ac43b0
    Abstract ( 364 )   HTML ( 3 )   PDF (1531KB) ( 107 )  
    Quantum controlled teleportation is the transmission of the quantum state under the supervision of a third party. This paper presents the theoretical and experimental results of an arbitrary two-qubit quantum controlled teleportation scheme, in which the sender Alice only needs to perform two Bell state measurements and the receiver Bob can perform an appropriate unitary operation to reconstruct the arbitrary two-qubit states under the control of the supervisor Charlie. The operation process of the scheme is verified on the IBM quantum experience platform, and the accuracy of the transmitted quantum state is further checked by performing quantum state tomography. Meanwhile, a good fidelity is obtained by using the theoretical density matrix and the experimental density matrix. A sequence of photonic states is introduced to analyze the possible intercept-replace-resend, intercept-measure-resend, and entanglement-measure-resend attacks on this scheme. The results proved that our scheme is highly secure.
    Pseudospin symmetric solutions of the Dirac equation with the modified Rosen—Morse potential using Nikiforov—Uvarov method and supersymmetric quantum mechanics approach
    Wen-Li Chen(陈文利) and I B Okon
    Chin. Phys. B, 2022, 31 (5):  050302.  DOI: 10.1088/1674-1056/ac2f33
    Abstract ( 261 )   HTML ( 0 )   PDF (820KB) ( 78 )  
    Employing the Pekeris-type approximation to deal with the pseudo-centrifugal term, we analytically study the pseudospin symmetry of a Dirac nucleon subjected to equal scalar and vector modified Rosen-Morse potential including the spin-orbit coupling term by using the Nikiforov-Uvarov method and supersymmetric quantum mechanics approach. The complex eigenvalue equation and the total normalized wave functions expressed in terms of Jacobi polynomial with arbitrary spin-orbit coupling quantum number k are presented under the condition of pseudospin symmetry. The eigenvalue equations for both methods reproduce the same result to affirm the mathematical accuracy of analytical calculations. The numerical solutions obtained for different adjustable parameters produce degeneracies for some quantum number.
    Self-error-rejecting multipartite entanglement purification for electron systems assisted by quantum-dot spins in optical microcavities
    Yong-Ting Liu(刘永婷), Yi-Ming Wu(吴一鸣), and Fang-Fang Du(杜芳芳)
    Chin. Phys. B, 2022, 31 (5):  050303.  DOI: 10.1088/1674-1056/ac4489
    Abstract ( 293 )   HTML ( 1 )   PDF (1335KB) ( 117 )  
    We present a self-error-rejecting multipartite entanglement purification protocol (MEPP) for N-electron-spin entangled states, resorting to the single-side cavity-spin-coupling system. Our MEPP has a high efficiency containing two steps. One is to obtain high-fidelity N-electron-spin entangled systems with error-heralded parity-check devices (PCDs) in the same parity-mode outcome of three electron-spin pairs, as well as M-electron-spin entangled subsystems (2≤M <N) in the different parity-mode outcomes of those. The other is to regain the N-electron-spin entangled systems from M-electron-spin entangled states utilizing entanglement link. Moreover, the quantum circuits of PCDs make our MEPP works faithfully, due to the practical photon-scattering deviations from the finite side leakage of the microcavity, and the limited coupling between a quantum dot and a cavity mode, converted into a failed detection in a heralded way.
    Environmental parameter estimation with the two-level atom probes
    Mengmeng Luo(罗萌萌), Wenxiao Liu(刘文晓), Yuetao Chen(陈悦涛), Shangbin Han(韩尚斌), and Shaoyan Gao(高韶燕)
    Chin. Phys. B, 2022, 31 (5):  050304.  DOI: 10.1088/1674-1056/ac364f
    Abstract ( 262 )   HTML ( 2 )   PDF (893KB) ( 61 )  
    A novel scheme is proposed to estimate three environmental parameters, the detuning, the temperature and the squeezing strength with one-qubit or two-qubit probes. Quantum Fisher information and the fidelity of the atom probes are calculated. When the detuning between the frequency of cavity field and the atomic transition frequency is estimated, the dynamics of quantum Fisher information shows oscillatory and rising behaviors. To estimate the temperature of the thermal reservoir, the one-qubit probe with the superposition initial state is more favorable than the two-qubit probe with the entangled initial state. When the squeezing strength of the squeezed vacuum reservoir is estimated, we find that the estimation precision is significantly improved by utilizing the two-qubit probe with the maximal entangled initial state. Our work provides a potential application in the open quantum system and quantum information processing.
    Analysis and improvement of verifiable blind quantum computation
    Min Xiao(肖敏) and Yannan Zhang(张艳南)
    Chin. Phys. B, 2022, 31 (5):  050305.  DOI: 10.1088/1674-1056/ac2f34
    Abstract ( 314 )   HTML ( 2 )   PDF (798KB) ( 58 )  
    In blind quantum computation (BQC), a client with weak quantum computation capabilities is allowed to delegate its quantum computation tasks to a server with powerful quantum computation capabilities, and the inputs, algorithms and outputs of the quantum computation are confidential to the server. Verifiability refers to the ability of the client to verify with a certain probability whether the server has executed the protocol correctly and can be realized by introducing trap qubits into the computation graph state to detect server deception. The existing verifiable universal BQC protocols are analyzed and compared in detail. The XTH protocol (proposed by Xu Q S, Tan X Q, Huang R in 2020), a recent improvement protocol of verifiable universal BQC, uses a sandglass-like graph state to further decrease resource expenditure and enhance verification capability. However, the XTH protocol has two shortcomings: limitations in the coloring scheme and a high probability of accepting an incorrect computation result. In this paper, we present an improved version of the XTH protocol, which revises the limitations of the original coloring scheme and further improves the verification ability. The analysis demonstrates that the resource expenditure is the same as for the XTH protocol, while the probability of accepting the wrong computation result is reduced from the original minimum (0.866)d* to (0.819)d*, where d* is the number of repeated executions of the protocol.
    Effects of colored noise on the dynamics of quantum entanglement of a one-parameter qubit—qutrit system
    Odette Melachio Tiokang, Fridolin Nya Tchangnwa, Jaures Diffo Tchinda,Arthur Tsamouo Tsokeng, and Martin Tchoffo
    Chin. Phys. B, 2022, 31 (5):  050306.  DOI: 10.1088/1674-1056/ac2f36
    Abstract ( 292 )   HTML ( 2 )   PDF (926KB) ( 100 )  
    We analyzed the effect of colored noise on the negativity dynamics of a hybrid system consisting of a qubit-qutrit and not interacting, prepared from the start in an entangled one-parameter state and acting with noise in local and non-local environments. In this pink and brown noise we investigated two different situations: in the first situation, the noise is produced by a bistable oscillator with an unknown exchange rate; however, in the second situation, the noise is generated by a set of bistable oscillators. We found that entanglement decreases with time to zero, and undergoes the phenomenon of sudden death and rebirth. The pink noise is more prone to entanglement than the brown noise and the non-local environment is more prone to entanglement than the local one. When the number of fluctuators is increased, entanglement decays faster and finally, for certain parameters of the initial state, the subsystems are not affected by the noise.
    SPECIAL TOPIC—Non-Hermitian physics
    Filling up complex spectral regions through non-Hermitian disordered chains
    Hui Jiang and Ching Hua Lee
    Chin. Phys. B, 2022, 31 (5):  050307.  DOI: 10.1088/1674-1056/ac4a73
    Abstract ( 333 )   HTML ( 12 )   PDF (9183KB) ( 275 )  
    Eigenspectra that fill regions in the complex plane have been intriguing to many, inspiring research from random matrix theory to esoteric semi-infinite bounded non-Hermitian lattices. In this work, we propose a simple and robust ansatz for constructing models whose eigenspectra fill up generic prescribed regions. Our approach utilizes specially designed non-Hermitian random couplings that allow the co-existence of eigenstates with a continuum of localization lengths, mathematically emulating the effects of semi-infinite boundaries. While some of these couplings are necessarily long-ranged, they are still far more local than what is possible with known random matrix ensembles. Our ansatz can be feasibly implemented in physical platforms such as classical and quantum circuits, and harbors very high tolerance to imperfections due to its stochastic nature.
    Efficient quantum private comparison protocol based on one direction discrete quantum walks on the circle
    Jv-Jie Wang(王莒杰), Zhao Dou(窦钊), Xiu-Bo Chen(陈秀波), Yu-Ping Lai(赖裕平), and Jian Li(李剑)
    Chin. Phys. B, 2022, 31 (5):  050308.  DOI: 10.1088/1674-1056/ac5a3f
    Abstract ( 308 )   HTML ( 2 )   PDF (885KB) ( 133 )  
    We propose an efficient quantum private comparison protocol firstly based on one direction quantum walks. With the help of one direction quantum walk, we develop a novel method that allows the semi-honest third party to set a flag to judge the comparing result, which improves the qubit efficiency and the maximum quantity of the participants' secret messages. Besides, our protocol can judge the size of the secret messages, not only equality. Furthermore, the quantum walks particle is disentangled in the initial state. It only requires a quantum walks operator to move, making our proposed protocol easy to implement and reducing the quantum resources. Through security analysis, we prove that our protocol can withstand well-known attacks and brute-force attacks. Analyses also reveal that our protocol is correct and practical.
    A rational quantum state sharing protocol with semi-off-line dealer
    Hua-Li Zhang(张花丽), Bi-Chen Che(车碧琛), Zhao Dou(窦钊), Yu Yang(杨榆), and Xiu-Bo Chen(陈秀波)
    Chin. Phys. B, 2022, 31 (5):  050309.  DOI: 10.1088/1674-1056/ac4e02
    Abstract ( 338 )   HTML ( 1 )   PDF (777KB) ( 34 )  
    A rational quantum state sharing protocol with the semi-off-line dealer is proposed. Firstly, the dealer Alice shares an arbitrary two-particle entangled state with the players by Einstein-Podolsky-Rosen (EPR) pairs and Greenberger-Horne-Zeilinger (GHZ) states. The EPR pairs are prepared by Charlie instead of the dealer, reducing the workload of the dealer. Secondly, all players have the same probability of reconstructing the quantum state, guaranteeing the fairness of the protocol. In addition, the dealer is semi-off-line, which considerably reduces the information exchanging between the dealer and the players. Finally, our protocol achieves security, fairness, correctness, and strict Nash equilibrium.
    Phase-matching quantum key distribution with light source monitoring
    Wen-Ting Li(李文婷), Le Wang(王乐), Wei Li(李威), and Sheng-Mei Zhao(赵生妹)
    Chin. Phys. B, 2022, 31 (5):  050310.  DOI: 10.1088/1674-1056/ac4101
    Abstract ( 328 )   HTML ( 1 )   PDF (1194KB) ( 46 )  
    The transmission loss of photons during quantum key distribution (QKD) process leads to the linear key rate bound for practical QKD systems without quantum repeaters. Phase matching quantum key distribution (PM-QKD) protocol, an novel QKD protocol, can overcome the constraint with a measurement-device-independent structure, while it still requires the light source to be ideal. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a modified PM-QKD protocol with a light source monitoring, named PM-QKD-LSM protocol, which can guarantee the security of the system under the non-ideal source condition. The results show that our proposed protocol performs almost the same as the ideal PM-QKD protocol even considering the imperfect factors in practical systems. PM-QKD-LSM protocol has a better performance with source fluctuation, and it is robust in symmetric or asymmetric cases.
    Wave function collapses and 1/n energy spectrum induced by a Coulomb potential in a one-dimensional flat band system
    Yi-Cai Zhang(张义财)
    Chin. Phys. B, 2022, 31 (5):  050311.  DOI: 10.1088/1674-1056/ac3653
    Abstract ( 284 )   HTML ( 1 )   PDF (1533KB) ( 58 )  
    We investigate the bound state problem in a one-dimensional flat band system with a Coulomb potential. It is found that, in the presence of a Coulomb potential of type I (with three equal diagonal elements), similarly to that in the two-dimensional case, the flat band could not survive. At the same time, the flat band states are transformed into localized states with a logarithmic singularity near the center position. In addition, the wave function near the origin would collapse for an arbitrarily weak Coulomb potential. Due to the wave function collapses, the eigen-energies for a shifted Coulomb potential depend sensitively on the cut-off parameter. For a Coulomb potential of type II, there exist infinite bound states that are generated from the flat band. Furthermore, when the bound state energy is very near the flat band, the energy is inversely proportional to the natural number, e.g.,$E_n\propto$ 1/n, n=1,2,3,... It is expected that the 1/n energy spectrum could be observed experimentally in the near future.
    Geometric phase under the Unruh effect with intermediate statistics
    Jun Feng(冯俊), Jing-Jun Zhang(张精俊), and Qianyi Zhang(张倩怡)
    Chin. Phys. B, 2022, 31 (5):  050312.  DOI: 10.1088/1674-1056/ac5d31
    Abstract ( 345 )   HTML ( 1 )   PDF (1529KB) ( 124 )  
    Utilizing the geometric phase (GP) acquired in a quantum evolution, we manifest the thermality and quantum nature of the Unruh effect of an accelerating detector. We consider an UDW detector coupling to a conformal field in Minkowski spacetime, whose response spectrum exhibits an intermediate statistics of (1+1) anyon field. We find that comparing to an inertial moving detector, the GP in accelerating frame is modified after the nonunitary evolution of the detector due to the Unruh effect. We show that such modification can distinguish the different thermalizing ways of the detector, which depends on the scaling dimension of the conformal primary field. Finally, we estimate the difference between the GP under the Unruh radiation and that in a thermal bath for a static observer, which reveals the quantum origin of the Unruh effect rather than a conventional thermal noise.
    Fringe removal algorithms for atomic absorption images: A survey
    Gaoyi Lei(雷高益), Chencheng Tang(唐陈成), and Yueyang Zhai(翟跃阳)
    Chin. Phys. B, 2022, 31 (5):  050313.  DOI: 10.1088/1674-1056/ac3758
    Abstract ( 320 )   HTML ( 3 )   PDF (1700KB) ( 132 )  
    The fringe noises disrupt the precise measurement of the atom distribution in the process of the absorption images. The fringe removal algorithms have been proposed to reconstruct the ideal reference images of the absorption images to remove the fringe noises. However, the focus of these fringe removal algorithms is the association of the fringe removal performance with the physical systems, leaving the gap to analyze the workflows of different fringe removal algorithms. This survey reviews the fringe removal algorithms and classifies them into two categories: the image-decomposition based methods and the deep-learning based methods. Then this survey draws the workflow details of two classical fringe removal algorithms, and conducts experiments on the absDL ultracold image dataset. Experiments show that the singular value decomposition (SVD) method achieves outstanding performance, and the U-net method succeeds in implying the image inpainting idea. The main contribution of this survey is the interpretation of the fringe removal algorithms, which may help readers have a better understanding of the research status. Codes in this survey are available at https://github.com/leigaoyi/Atomic_Fringe_Denoise.
    Thermodynamic effects of Bardeen black hole surrounded by perfect fluid dark matter under general uncertainty principle
    Zhenxiong Nie(聂振雄), Yun Liu(刘芸), Juhua Chen(陈菊华), and Yongjiu Wang(王永久)
    Chin. Phys. B, 2022, 31 (5):  050401.  DOI: 10.1088/1674-1056/ac3ca8
    Abstract ( 324 )   HTML ( 2 )   PDF (1202KB) ( 58 )  
    The thermodynamics of Bardeen black hole surrounded by perfect fluid dark matter is investigated. We calculate the analytical expresses of corresponding thermodynamic variables, e.g., the Hawking temperature, entropy of the black hole. In addition, we derive the heat capacity to analyze the thermal stability of the black hole. We also compute the rate of emission in terms of photons through tunneling. By numerical method, an obvious phase transition behavior is found. Furthermore, according to the general uncertainty principle, we study the quantum corrections to these thermodynamic quantities and obtain the quantum-corrected entropy containing the logarithmic term. Lastly, we investigate the effects of the magnetic charge g, the dark matter parameter k and the generalized uncertainty principle parameter α on the thermodynamics of Bardeen black hole surrounded by perfect fluid dark matter under general uncertainty principle.
    Relativistic motion on Gaussian quantum steering for two-mode localized Gaussian states
    Xiao-Long Gong(龚小龙), Shuo Cao(曹硕), Yue Fang(方越), and Tong-Hua Liu(刘统华)
    Chin. Phys. B, 2022, 31 (5):  050402.  DOI: 10.1088/1674-1056/ac401f
    Abstract ( 409 )   HTML ( 3 )   PDF (2682KB) ( 36 )  
    Realistic quantum systems always exhibit gravitational and relativistic features. In this paper, we investigate the properties of Gaussian steering and its asymmetry by the localized two-mode Gaussian quantum states, instead of the traditional single-mode approximation method in the relativistic setting. We find that the one-side Gaussian quantum steering will monotonically decrease with increasing observers of acceleration. Meanwhile, our results also reveal the interesting behavior of the Gaussian steering asymmetry, which increases for a specific range of accelerated parameter and then gradually approaches to a finite value. Such finding is well consistent and explained by the well-known Unruh effect, which could significantly destroy the one-side Gaussian quantum steering. Finally, our results could also be applied to the dynamical studies of Gaussian steering between the Earth and satellites, since the effects of acceleration are equal to the effects of gravity according to the equivalence principle.
    Nano-friction phenomenon of Frenkel—Kontorova model under Gaussian colored noise
    Yi-Wei Li(李毅伟), Peng-Fei Xu(许鹏飞), and Yong-Ge Yang(杨勇歌)
    Chin. Phys. B, 2022, 31 (5):  050501.  DOI: 10.1088/1674-1056/ac439d
    Abstract ( 338 )   HTML ( 1 )   PDF (1089KB) ( 54 )  
    The nano-friction phenomenon in a one-dimensional Frenkel-Kontorova (FK) model under Gaussian colored noise is investigated by using the molecular dynamic simulation method. The role of colored noise is analyzed through the inclusion of a stochastic force via a Langevin molecular dynamics method. Via the stochastic Runge-Kutta algorithm, the relationship between different parameter values of the Gaussian colored noise (the noise intensity and the correlation time) and the nano-friction phenomena such as hysteresis, the maximum static friction force is separately studied here. Similar results are obtained from the two geometrically opposed ideal cases: incommensurate and commensurate interfaces. It was found that the noise strongly influences the hysteresis and maximum static friction force and with an appropriate external driving force, the introduction of noise can accelerate the motion of the system, making the atoms escape from the substrate potential well more easily. Interestingly, suitable correlation time and noise intensity give rise to super-lubricity. It is noteworthy that the difference between the two circumstances lies in the fact that the effect of the noise is much stronger on triggering the motion of the FK model for the commensurate interface than that for the incommensurate interface.
    Characterization of a nano line width reference material based on metrological scanning electron microscope
    Fang Wang(王芳), Yushu Shi(施玉书), Wei Li(李伟), Xiao Deng(邓晓), Xinbin Cheng(程鑫彬), Shu Zhang(张树), and Xixi Yu(余茜茜)
    Chin. Phys. B, 2022, 31 (5):  050601.  DOI: 10.1088/1674-1056/ac3225
    Abstract ( 318 )   HTML ( 2 )   PDF (5236KB) ( 112 )  
    The line width (often synonymously used for critical dimension, CD) is a crucial parameter in integrated circuits. To accurately control CD values in manufacturing, a reasonable CD reference material is required to calibrate the corresponding instruments. We develop a new reference material with nominal CDs of 160 nm, 80 nm, and 40 nm. The line features are investigated based on the metrological scanning electron microscope which is developed by the National Institute of Metrology (NIM) in China. Also, we propose a new characterization method for the precise measurement of CD values. After filtering and leveling the intensity profiles, the line features are characterized by the combination model of the Gaussian and Lorentz functions. The left and right edges of CD are automatically extracted with the profile decomposition and k-means algorithm. Then the width of the two edges at the half intensity position is regarded as the standard CD value. Finally, the measurement results are evaluated in terms of the sample, instrument, algorithm, and repeatability. The experiments indicate efficiency of the proposed method which can be easily applied in practice to accurately characterize CDs.
    Penumbra lunar eclipse observations reveal anomalous thermal performance of Lunakhod 2 reflectors
    Tian-Quan Gao(高添泉), Cai-Shi Zhang(张才士), Hong-Chao Zhao(赵宏超), Li-Xiang Zhou(周立祥), Xian-Lin Wu(吴先霖), Hsienchi Yeh(叶贤基), and Ming Li(李明)
    Chin. Phys. B, 2022, 31 (5):  050602.  DOI: 10.1088/1674-1056/ac3068
    Abstract ( 331 )   HTML ( 2 )   PDF (1840KB) ( 75 )  
    As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon, we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lunar laser ranging echo. Laser ranging measurements during the penumbra lunar eclipse verify suspected thermal deformation in the Lunakhod 2 reflectors. Signal levels vary over two orders of magnitude as the penumbra eclipse progresses. This can be explained by the change in the dihedral angle of the corner-cube reflectors caused by the temperature. The results show that when the dihedral angle errors reach 1'', the energy is reduced by 100 times compared with the ideal corner-cube reflector. In the experiment, our findings suggest that when the corner-cube reflector arrays enter the penumbra of the earth, the effective echo signal level which reaches 0.18 photons/s far exceeds the historical level of the full moon. However, 11 minutes after the penumbra lunar eclipse, the effective echo rate of Lunakhod 2 will drop two orders of magnitude. The mechanism can explain the acute signal deficit observed at full moon.
    A self-powered and sensitive terahertz photodetection based on PdSe2
    Jie Zhou(周洁), Xueyan Wang(王雪妍), Zhiqingzi Chen(陈支庆子), Libo Zhang(张力波), Chenyu Yao(姚晨禹), Weijie Du(杜伟杰), Jiazhen Zhang(张家振), Huaizhong Xing(邢怀中), Nanxin Fu(付南新), Gang Chen(陈刚), and Lin Wang(王林)
    Chin. Phys. B, 2022, 31 (5):  050701.  DOI: 10.1088/1674-1056/ac4908
    Abstract ( 373 )   HTML ( 1 )   PDF (2839KB) ( 244 )  
    With the rapid development of terahertz technology, terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging, materials diagnostics, biology, medical sciences, and communication. Whereas self-powered, rapid response, and room temperature terahertz photodetectors are confronted with huge challenges. Here, we report a novel rapid response and self-powered terahertz photothermoelectronic (PTE) photodetector based on a low-dimensional material: palladium selenide (PdSe2). An order of magnitude performance enhancement was observed in photodetection based on PdSe2/graphene heterojunction that resulted from the integration of graphene and enhanced the Seebeck effect. Under 0.1-THz and 0.3-THz irradiations, the device displays a stable and repeatable photoresponse at room temperature without bias. Furthermore, rapid rise (5.0 μs) and decay (5.4 μs) times are recorded under 0.1-THz irradiation. Our results demonstrate the promising prospect of the detector based on PdSe2 in terms of air-stable, suitable sensitivity and speed, which may have great application in terahertz detection.
    A stopping layer concept to improve the spatial resolution of gas-electron-multiplier neutron detector
    Jianjin Zhou(周建晋), Jianrong Zhou(周健荣), Xiaojuan Zhou(周晓娟), Lin Zhu(朱林), Jianqing Yang(杨建清), Guian Yang(杨桂安), Yi Zhang(张毅), Baowei Ding(丁宝卫), Bitao Hu(胡碧涛), Zhijia Sun(孙志嘉), Limin Duan(段利敏), and Yuanbo Chen(陈元柏)
    Chin. Phys. B, 2022, 31 (5):  050702.  DOI: 10.1088/1674-1056/ac398e
    Abstract ( 309 )   HTML ( 1 )   PDF (870KB) ( 77 )  
    In recent years, gas electron multiplier (GEM) neutron detectors have been developing towards high spatial resolution and high dynamic counting range. We propose a novel concept of an Al stopping layer to enable the detector to achieve sub-millimeter (sub-mm) spatial resolution. The neutron conversion layer is coated with the Al stopping layer to limit the emission angle of ions into the drift region. The short track projection of ions is obtained on the signal readout board, and the detector would get good spatial resolution. The spatial resolutions of the GEM neutron detector with the Al stopping layer are simulated and optimized based on Geant4GarfieldInterface. The spatial resolution of the detector is 0.76 mm and the thermal neutron detection efficiency is about 0.01% when the Al stopping layer is 3.0 μ m thick, the drift region is 2 mm thick, the strip pitch is 600 μ m, and the digital readout is employed. Thus, the GEM neutron detector with a simple detector structure and a fast readout mode is developed to obtain a high spatial resolution and high dynamic counting range. It could be used for the direct measurement of a high-flux neutron beam, such as Bragg transmission imaging, very small-angle scattering neutron detection and neutron beam diagnostic.
    Theoretical study on the transition properties of AlF
    Yun-Guang Zhang(张云光), Ling-Ling Ji(吉玲玲), Ru Cai(蔡茹),Cong-Ying Zhang(张聪颖), and Jian-Gang Xu(徐建刚)
    Chin. Phys. B, 2022, 31 (5):  053101.  DOI: 10.1088/1674-1056/ac3648
    Abstract ( 472 )   HTML ( 2 )   PDF (793KB) ( 75 )  
    Potential energy curves of the X$^{1}\Sigma ^{+}$ and A$^{1}\Pi $ states of the AlF molecule are studied through the combination of the multi-reference configuration interaction (MRCI) approach and Davidson corrections (MRCI$+$Q). The AWCV5Z basis set is employed in the calculations. The transition dipole moments (TDMs) of the A$^{1}\Pi \leftrightarrow {\rm X}^{1}\Sigma^{+}$ transition are explored based on the AWCV5Z basis set and (4, 2, 2, 0) active space. The Schrödinger equation is solved via the LEVEL 8.2 program, and the vibrational levels and rotational constants of the X$^{1}\Sigma^{+}$ and A$^{1}\Pi $ states are calculated. It is shown that the AlF molecule has high diagonal Franck-Condon factors ($f_{00}=0.9949$ and $f_{11}=0.9854$) and large Einstein coefficients for the transition of A$^{1}\Pi {(\nu }'=0)\leftrightarrow {\rm X}^{1}\Sigma^{+}{\rm (\nu }''=0)$. In addition, the radiative lifetimes of the vibrational levels are close to 10$^{-9}$ s for the A$^{1}\Pi $ state. The line intensities of the A$^{1}\Pi {\rm (\nu }'=4-15)\leftrightarrow {\rm X}^{1}\Sigma^{+}{\rm (\nu }''=0)$ transitions are also calculated. The calculated TDMs and transition probabilities in this work are credible and provide some guidance for the study of similar transitions, particularly for exploring interstellar space.
    Energy levels and transition data of 3p63d8 and 3p53d9 configurations in Fe-like ions (Z = 57, 60, 62, 64, 65)
    Bao-Ling Shi(施宝玲), Yi Qin(秦毅), Xiang-Fu Li(李向富), Bang-Lin Deng(邓邦林), Gang Jiang(蒋刚), and Xi-Long Dou(豆喜龙)
    Chin. Phys. B, 2022, 31 (5):  053102.  DOI: 10.1088/1674-1056/ac4480
    Abstract ( 319 )   HTML ( 4 )   PDF (927KB) ( 74 )  
    Atomic data of highly charged ions (HCIs) offer an attractive means for plasma diagnostic and stars identification, and the investigations on atomic data are highly desirable. Herein, based on the fully relativistic multi-configuration Dirac-Hartree-Fock (MCDHF) method, we have performed calculations of the fine-structure energy levels, wavelengths, transition rates, oscillator strengths, and line strengths for the lowest 21 states of 3p63d8-3p53d9 electric dipole (E1) transitions configurations in Fe-like ions (Z = 57, 60, 62, 64, 65). The correlation effects of valence-valence (VV) and core-valence (CV) electrons were systematically considered. In addition, we have taken into account transverse-photon (Breit) interaction and quantum electrodynamics (QED) corrections to treat accurately the atomic state wave functions in the final relativistic configuration interaction (RCI) calculations. Our calculated energy levels and transition wavelengths are in excellent agreement with the available experimental and theoretical results. Most importantly, we predicted some new transition parameters that have not yet been reported. These data would further provide critical insights into better analyzing the physical processes of various astrophysical plasmas.
    Laser-induced fluorescence experimental spectroscopy and theoretical calculations of uranium monoxide
    Xi-Lin Bai(白西林), Xue-Dong Zhang(张雪东), Fu-Qiang Zhang(张富强), and Timothy C Steimle
    Chin. Phys. B, 2022, 31 (5):  053301.  DOI: 10.1088/1674-1056/ac43a4
    Abstract ( 329 )   HTML ( 2 )   PDF (2351KB) ( 115 )  
    As a model molecule of actinide chemistry, UO molecule plays an important role in understanding the electronic structure and chemical bonding of actinide-containing species. We report a study of the laser-induced fluorescence spectra of the U16O and U18O using two-dimensional spectroscopy. Several rotationally resolved excitation spectra were investigated. Accurate molecular rotational constants and equilibrium internuclear distances were reported. Low-lying electronic states information was extracted from high resolution dispersed fluorescence spectra and analyzed by the ligand field theory model. The configuration of the ground state was determined as U2+(5f37s)O2-. The branching ratios, and the vibrational harmonic and anharmonic parameters were also obtained. Radiative lifetimes were determined by recording the time-resolved fluorescence spectroscopy. Transition dipole moments were calculated using the branching ratios and the radiative lifetimes. These findings were elucidated by using quantum-chemical calculations, and the chemical bonding was also analyzed. The findings presented in this work will enrich our understanding of actinide-containing molecules.
    Computational design of ratiometric two-photon fluorescent Zn2+ probes based on quinoline and di-2-picolylamine moieties
    Zhe Shao(邵哲), Wen-Ying Zhang(张纹莹), and Ke Zhao(赵珂)
    Chin. Phys. B, 2022, 31 (5):  053302.  DOI: 10.1088/1674-1056/ac46c6
    Abstract ( 256 )   HTML ( 0 )   PDF (2863KB) ( 28 )  
    To improve two-photon absorption (TPA) response of a newly synthesized probe, a series of ratiometric two-photon fluorescent Zn2+ sensors based on quinoline and DPA moieties have been designed. The one-photon absorption, TPA, and emission properties of the experimental and designed probes before and after coordination with Zn2+ are investigated employing the density functional theory in combination with response functions. The design consists of two levels. In the first level of design, five probes are constructed through using several electron acceptors or donors to increase accepting or donating ability of the fluorophores. It shows that all the designed probes have stronger TPA intensities at longer wavelengths with respect to the experimental probe because of the increased intra-molecular charge transfer. Moreover, it is found that the probe 4 built by adding an acyl unit has the largest TPA cross section among the designed structures due to the form of longer conjugated length and more linear backbone. One dimethylamino terminal attached along the skeleton can improve TPA intensity more efficiently than two side amino groups. Therefore, in the second level of design, a new probe 7 is formed by both an acyl unit and a dimethylamino terminal. It exhibits that the TPA cross sections of probe 7 and its zinc complex increase dramatically. Furthermore, the fluorescence quantum yields of the designed probes 4 and 7 are calculated in a new way, which makes use of the relation between the computed difference of dipole moment and the measured fluorescence quantum yield. The result shows that our design also improves the fluorescence quantum yield considerably. All in all, the designed probes 4 and 7 not only possess enhanced TPA intensities but also have large differences of emission wavelength upon Zn2+ coordination and strong fluorescence intensity, which demonstrates that they are potential ratiometric two-photon fluorescent probes.
    Oscillator strength study of the excitations of valence-shell of C2H2 by high-resolution inelastic x-ray scattering
    Qiang Sun(孙强), Ya-Wei Liu(刘亚伟), Yuan-Chen Xu(徐远琛), Li-Han Wang(王礼涵), Tian-Jun Li(李天钧), Shu-Xing Wang(汪书兴), Ke Yang(杨科), and Lin-Fan Zhu(朱林繁)
    Chin. Phys. B, 2022, 31 (5):  053401.  DOI: 10.1088/1674-1056/ac422e
    Abstract ( 324 )   HTML ( 0 )   PDF (1018KB) ( 94 )  
    The oscillator strengths of the valence-shell excitations of C2H2 are extremely important for testing theoretical models and studying interstellar gases. In this study, the high-resolution inelastic x-ray scattering (IXS) method is adopted to determine the generalized oscillator strengths (GOSs) of the valence-shell excitations of C2H2 at a photon energy of 10 keV. The GOSs are extrapolated to their zero limit to obtain the corresponding optical oscillator strengths (OOSs). Through taking a completely different experimental method of the IXS, the present results offer the high energy limit for electron collision to satisfy the first Born approximation (FBA) and cross-check the previous experimental and theoretical results independently. The comparisons indicate that an electron collision energy of 1500 eV is not enough for C2H2 to satisfy the FBA for the large squared momentum transfer, and the line saturation effect limits the accuracy of the OOSs measured by the photoabsorption method.
    Measuring gravitational effect of superintense laser by spin-squeezed Bose—Einstein condensates interferometer
    Eng Boon Ng and C. H. Raymond Ooi
    Chin. Phys. B, 2022, 31 (5):  053701.  DOI: 10.1088/1674-1056/ac4231
    Abstract ( 263 )   HTML ( 1 )   PDF (1742KB) ( 62 )  
    We consider an extremely intense laser, enclosed by an atom interferometer. The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit. We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer. The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose-Einstein condensates. We push up the sensitivity limit of the interferometer with Bose-Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.
    Switchable directional scattering based on spoof core—shell plasmonic structures
    Yun-Qiao Yin(殷允桥), Hong-Wei Wu(吴宏伟), Shu-Ling Cheng(程淑玲), and Zong-Qiang Sheng(圣宗强)
    Chin. Phys. B, 2022, 31 (5):  054101.  DOI: 10.1088/1674-1056/ac3503
    Abstract ( 316 )   HTML ( 0 )   PDF (1748KB) ( 98 )  
    Manipulating directional electromagnetic scattering plays a crucial role in the realization of exotic optical phenomenon. Here, we show that the spoof plasmonic structure is able to achieve the switching of directional scattering direction on a subwavelength scale by inserting a perfect electric conductor (PEC) cylinder into the hollow of the spoof plasmonic structure. Based on the modal analysis, it is found that the electromagnetic response of the core-shell structure not only is well excited, but also exhibits the directional scattering by interference between the electric and magnetic dipolar resonances. We also discuss the influence of PEC cylinder radius on the performance of the directional scattering. Finally, the active tunable directional scattering is realized by switching between the two states. This work provides a feasible pathway to the subwavelength manipulation of electromagnetic wave. Moreover, it offers a simple method to switch the directional scattering direction. The proposed design approach can be easily applied to digital electromagnetic wave communication and associated applications.
    A multi-frequency circularly polarized metasurface antenna array based on quarter-mode substrate integrated waveguide for sub-6 applications
    Hao Bai(白昊), Guang-Ming Wang(王光明), Xiao-Jun Zou(邹晓鋆), Peng Xie(谢鹏), and Yi-Ping Shi(石一平)
    Chin. Phys. B, 2022, 31 (5):  054102.  DOI: 10.1088/1674-1056/ac373b
    Abstract ( 295 )   HTML ( 0 )   PDF (3862KB) ( 74 )  
    A miniaturized multi-frequency circularly polarized array is designed in this paper. The antenna array is composed of three independent sub-arrays employing modified quarter-mode substrate ntegrated aveguide (QMSIW) to achieve three circularly polarized frequency bands. By introducing strip-slot, the impedance bandwidth of the antenna array is broadened while the dimension is decreased by 75% to realize miniaturization. Meanwhile, metasurface causes the impedance bandwidth of the sub-array to be further enhanced. Moreover, the metal vias are employed in the antenna array design to further achieve miniaturization. The antenna array is manufactured and measured to verify the design. Both the measured and simulated results display that the array achieves the impedance bandwidths of 10%, 11.7%, and 14.8% and axial ratio bandwidths of 8.8%, 8.0%, and 8.5% at 2.5, 3.5, and 4.8 GHz, respectively. The gain is stable in the operating band within an uncertainty of 0.7 dBi. The whole dimension is 0.92λ×0.63λ×0.04λ, where λ0 is the wavelength at the lowest resonant frequency. Furthermore, the simple structure and miniaturization provides great convenience in sub-6 applications.
    Electron beam modeling and analyses of the electric field distribution and space charge effect
    Yueling Jiang(蒋越凌) and Quanlin Dong(董全林)
    Chin. Phys. B, 2022, 31 (5):  054103.  DOI: 10.1088/1674-1056/ac3d84
    Abstract ( 383 )   HTML ( 0 )   PDF (1396KB) ( 36 )  
    In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam's cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.
    A simple and comprehensive electromagnetic theory uncovering complete picture of light transport in birefringent crystals
    Jianbo Pan(潘剑波), Jianfeng Chen(陈剑锋), Lihong Hong(洪丽红), Li Long(龙利), and Zhi-Yuan Li(李志远)
    Chin. Phys. B, 2022, 31 (5):  054201.  DOI: 10.1088/1674-1056/ac4747
    Abstract ( 468 )   HTML ( 1 )   PDF (1248KB) ( 174 )  
    Birefringence production of light by natural birefringent crystal has long been studied and well understood. Here, we develop a simple and comprehensive rigorous electromagnetic theory that allows one to build up the complete picture about the optics of crystals in a friendly way. This theory not only yields the well-known refraction angle and index of ellipse for birefringence crystal, but also discloses many relevant physical and optical quantities that are rarely studied and less understood. We obtain the reflection and transmission coefficient for amplitude and intensity of light at the crystal surface under a given incident angle and show the electromagnetic field distribution within the crystal. We derive the wavefront and energy flux refraction angle of light and the corresponding phase and ray refractive index. We find big difference between them, where the phase refractive index satisfies the classical index of ellipse and Snell's law, while the ray refractive index does not. Moreover, we disclose the explicit expressions for the zero-reflection Brewster angle and the critical angle for total internal reflection. For better concept demonstration, we take a weak birefringent crystal of lithium niobate and a strong birefringent crystal tellurium as examples and perform simple theoretical calculations. In addition, we perform experimental measurement upon z-cut lithium niobate plate and find excellent agreement between theory and experiment in regard to the Brewster angle. Our theoretical and experimental results can help to construct a clear and complete picture about light transport characteristics in birefringent crystals, and may greatly facilitate people to find rigorous solution to many light-matter interaction processes happening within birefringent crystals, e.g., nonlinear optical interactions, with electromagnetic theory.
    On chip chiral and plasmonic hybrid dimer or tetramer: Generic way to reverse longitudinal and lateral optical binding forces
    Sudipta Biswas, Roksana Khanam Rumi, Tasnia Rahman Raima, Saikat Chandra Das, and M R C Mahdy
    Chin. Phys. B, 2022, 31 (5):  054202.  DOI: 10.1088/1674-1056/ac322d
    Abstract ( 263 )   HTML ( 1 )   PDF (8109KB) ( 50 )  
    For both the longitudinal binding force and the lateral binding force, a generic way of controlling the mutual attraction and repulsion (usually referred to as reversal of optical binding force) between chiral and plasmonic hybrid dimers or tetramers has not been reported so far. In this paper, by using a simple plane wave and an onchip configuration, we propose a possible generic way to control the binding force for such hybrid objects in both the near-field region and the far-field region. We also investigate different inter-particle distances while varying the wavelengths of light for each inter-particle distance throughout the investigations. First of all, for the case of longitudinal binding force, we find that chiral-plasmonic hybrid dimer pairs do not exhibit any reversal of optical binding force in the near-field region nor in the far-field region when the wavelength of light is varied in an air medium. However, when the same hybrid system of nanoparticles is placed over a plasmonic substrate, a possible chip, it is possible to achieve a reversal of the longitudinal optical binding force. Later, for the case of lateral optical binding force, we investigate a setup where we place the chiral and plasmonic tetramers on a plasmonic substrate by using two chiral nanoparticles and two plasmonic nanoparticles, with the setup illuminated by a circularly polarized plane wave. By applying the left-handed and the right-handed circular polarization state of light, we also observe the near-field and the far-field reversal of lateral optical binding force for both cases. As far as we know, so far, no work has been reported in the literature on the generic way of reversing the longitudinal optical binding force and the lateral optical binding force of such hybrid objects. Such a generic way of controlling optical binding forces can have important applications in different fields of science and technology in the near future.
    Manipulating vector solitons with super-sech pulse shapes
    Yan Zhou(周延), Keyun Zhang(张克赟), Chun Luo(罗纯), Xiaoyan Lin(林晓艳), Meisong Liao(廖梅松), Guoying Zhao(赵国营), and Yongzheng Fang(房永征)
    Chin. Phys. B, 2022, 31 (5):  054203.  DOI: 10.1088/1674-1056/ac439f
    Abstract ( 379 )   HTML ( 0 )   PDF (874KB) ( 52 )  
    Theoretical simulations about manipulating vector solitons with super-sech pulse shapes are conducted based on an optical fiber system. By changing the temporal pulses' parameters when the orthogonally polarized pulses have the same or different input central wavelengths, the output modes in orthogonal directions will demonstrate different properties. When the input orthogonal modes have the same central wavelength, the “2+2” pseudo-high-order vector soliton can be generated when the time delay is changed. While under the condition of different central wavelengths, orthogonal pulses with multiple peaks accompanied with two wavelengths can be achieved through varying the projection angle, time delay or phase difference. Our simulations are helpful to the study of optical soliton dynamics in optical fiber systems.
    Nonlocal nonreciprocal optomechanical circulator
    Ji-Hui Zheng(郑继会), Rui Peng(彭蕊), Jiong Cheng(程泂), Jing An(安静), and Wen-Zhao Zhang(张闻钊)
    Chin. Phys. B, 2022, 31 (5):  054204.  DOI: 10.1088/1674-1056/ac4100
    Abstract ( 251 )   HTML ( 0 )   PDF (1887KB) ( 48 )  
    A nonlocal circulator protocol is proposed in a hybrid optomechanical system. By analogy with quantum communication, using the input-output relationship, we establish the quantum channel between two optical modes with long-range. The three-body nonlocal interaction between the cavity and the two oscillators is obtained by eliminating the optomechanical cavity mode and verifying the Bell-CHSH inequality of continuous variables. By introducing the phase accumulation between cyclic interactions, the unidirectional transmission of quantum state between the optical mode and two mechanical modes is achieved. The results show that nonreciprocal transmissions are achieved as long as the accumulated phase reaches a certain value. In addition, the effective interaction parameters in our system are amplified, which reduces the difficulty of the implementation of our protocol. Our research can provide potential applications for nonlocal manipulation and transmission control of quantum platforms.
    Nonclassicality of photon-modulated spin coherent states in the Holstein—Primakoff realization
    Xiaoyan Zhang(张晓燕), Jisuo Wang(王继锁), Lei Wang(王磊),Xiangguo Meng(孟祥国), and Baolong Liang(梁宝龙)
    Chin. Phys. B, 2022, 31 (5):  054205.  DOI: 10.1088/1674-1056/ac40f5
    Abstract ( 398 )   HTML ( 0 )   PDF (1957KB) ( 39 )  
    Two new photon-modulated spin coherent states (SCSs) are introduced by operating the spin ladder operators J± on the ordinary SCS in the Holstein-Primakoff realization and the nonclassicality is exhibited via their photon number distribution, second-order correlation function, photocount distribution and negativity of Wigner distribution. Analytical results show that the photocount distribution is a Bernoulli distribution and the Wigner functions are only associated with two-variable Hermite polynomials. Compared with the ordinary SCS, the photon-modulated SCSs exhibit more stronger nonclassicality in certain regions of the photon modulated number k and spin number j, which means that the nonclassicality can be enhanced by selecting suitable parameters.
    Nonreciprocal two-photon transmission and statistics in a chiral waveguide QED system
    Lei Wang(王磊), Zhen Yi(伊珍), Li-Hui Sun(孙利辉), and Wen-Ju Gu(谷文举)
    Chin. Phys. B, 2022, 31 (5):  054206.  DOI: 10.1088/1674-1056/ac3ecc
    Abstract ( 252 )   HTML ( 0 )   PDF (960KB) ( 49 )  
    We study the nonreciprocal properties of transmitted photons in a chiral waveguide quantum electrodynamics (QED) system, including single- and two-photon transmissions and second-order correlations. For the single-photon transmission, the nonreciprocity is induced by the effects of chiral coupling and atomic dissipation in the weak coupling region. It vanishes in the strong coupling regime when the effect of atomic dissipation becomes ignorable. In the case of two-photon transmission, there exist two ways of going through the emitter: independently as plane waves and formation of bound state. Besides the nonreciprocal behavior of plane waves, the bound state that differs in two directions also alters transmission probabilities. In addition, the second-order correlation of transmitted photons depends on the interference between plane wave and bound state. The destructive interference leads to the strong antibunching in the weak coupling region, while the effective formation of bound state leads to the strong bunching in the intermediate coupling region. However, the negligible interactions for left-propagating photons hardly change the statistics of the input coherent state.
    Multi-function terahertz wave manipulation utilizing Fourier convolution operation metasurface
    Min Zhong(仲敏) and Jiu-Sheng Li(李九生)
    Chin. Phys. B, 2022, 31 (5):  054207.  DOI: 10.1088/1674-1056/ac46c0
    Abstract ( 361 )   HTML ( 3 )   PDF (1347KB) ( 209 )  
    We propose a novel metasurface based on a combined pattern of outer C-shaped ring and inner rectangular ring. By Fourier convolution operation to generating different predesigned sequences of metasurfaces, we realize various functionalities to flexible manipulate terahertz waves including vortex terahertz beam splitting, anomalous vortex terahertz wave deflection, vortex terahertz wave splitting and deflection simultaneously. The incident terahertz wave can be flexibly controlled in a single metasurface. The designed metasurface has an extensive application prospect in the field of future terahertz communication and sensing.
    Pump pulse characteristics of quasi-continuous-wave diode-side-pumped Nd:YAG laser
    Zexin Song(宋泽鑫), Qi Bian(卞奇), Yu Shen(申玉), Keling Gong(龚柯菱), Nan Zong(宗楠), Qingshuang Zong(宗庆霜), Yong Bo(薄勇), and Qinjun Peng(彭钦军)
    Chin. Phys. B, 2022, 31 (5):  054208.  DOI: 10.1088/1674-1056/ac447f
    Abstract ( 329 )   HTML ( 1 )   PDF (1528KB) ( 73 )  
    The influence of pumping laser pulse on the property of quasi-continuous-wave (QCW) diode-side-pumped Nd:YAG laser is investigated theoretically and experimentally. Under remaining a fixed duty cycle, the average output power increases, and the corresponding thermal focal length shorten with the increase of the pump pulse duration, which attributes to the decrease of the ratio of pulse buildup time to the pulse duration. At a pump power of 146 W, the laser output power changes from 65.1 W to 81.2 W when the pulse duration is adjusted from 150 μ s to 1000 μ s, confirming a significant enhancement of 24.7%. A laser rate equation model incorporating the amplified spontaneous emission is also utilized and numerically solved, and the simulated results agree well with the experimental data.
    High power semiconductor laser array with single-mode emission
    Peng Jia(贾鹏), Zhi-Jun Zhang(张志军), Yong-Yi Chen(陈泳屹), Zai-Jin Li(李再金), Li Qin(秦莉), Lei Liang(梁磊), Yu-Xin Lei(雷宇鑫), Cheng Qiu(邱橙), Yue Song(宋悦), Xiao-Nan Shan(单肖楠), Yong-Qiang Ning(宁永强), Yi Qu(曲轶), and Li-Jun Wang(王立军)
    Chin. Phys. B, 2022, 31 (5):  054209.  DOI: 10.1088/1674-1056/ac373d
    Abstract ( 437 )   HTML ( 0 )   PDF (1339KB) ( 50 )  
    The semiconductor laser array with single-mode emission is presented in this paper. The 6-μ m-wide ridge waveguides (RWGs) are fabricated to select the lateral mode. Thus the fundamental mode of laser array can be obtained by the RWGs. And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A, after that, a kink will appear. The slow axis (SA) far-field divergence angle of the unit is 13.65°. The beam quality factor M2 of the units determined by the second-order moment (SOM) method, is 1.2. This single-mode emission laser array can be used for laser processing.
    All polarization-maintaining Er:fiber-based optical frequency comb for frequency comparison of optical clocks
    Pan Zhang(张攀), Yan-Yan Zhang(张颜艳), Ming-Kun Li(李铭坤), Bing-Jie Rao(饶冰洁), Lu-Lu Yan(闫露露), Fa-Xi Chen(陈法喜), Xiao-Fei Zhang(张晓斐), Qun-Feng Chen(陈群峰), Hai-Feng Jiang(姜海峰), and Shou-Gang Zhang(张首刚)
    Chin. Phys. B, 2022, 31 (5):  054210.  DOI: 10.1088/1674-1056/ac40f6
    Abstract ( 278 )   HTML ( 1 )   PDF (1294KB) ( 78 )  
    We demonstrate an optical frequency comb (OFC) based on a turnkey mode-locked laser with a figure-9-shape structure and polarization-maintaining fibers, for the comparison of frequency among optical clocks with wavelengths of 698 nm, 729 nm, 1068 nm, and 1156 nm. We adopt a multi-branch approach in order to produce high power OFC signals at these specific wavelengths, enabling the signal-to-noise ratio of the beatnotes between the OFC and the clock lasers to exceed 30 dB at a resolution bandwidth of 300 kHz. This approach makes the supercontinuum spectra much easier to be generated than a single branch OFC. However, more out-of-loop fibers degrade the long-term frequency instability due to thermal drift. To minimize the thermal drift effect, we set the fiber lengths of different branches to be similar, and we stabilize the temperature as well. The out-of-loop frequency instability of the OFC due to the incoherence of the multi-branch is about 5.5×10-19 for 4000 s, while the in-loop frequency instability of fceo and that of fbeat are 7.5×10-18 for 1 s and 8.5×10-18 for 1 s, respectively. The turnkey OFC meets the requirement for the comparison of frequency between the best optical clocks.
    Generation of mid-infrared supercontinuum by designing circular photonic crystal fiber
    Ying Huang(黄颖), Hua Yang(杨华), and Yucheng Mao(毛雨澄)
    Chin. Phys. B, 2022, 31 (5):  054211.  DOI: 10.1088/1674-1056/ac272c
    Abstract ( 309 )   HTML ( 0 )   PDF (11087KB) ( 85 )  
    A circular photonic crystal fiber (C-PCF) based on As2Se3 is designed, which has three zero dispersion wavelengths and flat dispersion. Using this fiber, a wide mid-infrared supercontinuum (MIR-SC) can be generated by launching a femtosecond pulse in the first anomalous dispersion region. The simulation results show that the MIR-SC is formed by soliton self-frequency shift and direct soliton spectrum tunneling on the long wavelength side and self-phase modulation, soliton fission on the short wavelength side. Further, optical shocking and four-wave mixing (FWM) are not conducive to the long-wavelength extension of MIR-SC, while the number and intensity of fundamental solitons have a greater effect on the short-wavelength extension of MIR-SC. The generation of optical shocking waves, FWM waves and fundamental solitons can be obviously affected by changing the fiber length and input pulse parameters, so that the spectrum range and flatness can be adjusted with great freedom. Finally, under the conditions of 4000 W pulse peak power, 30 fs pulse width, 47 mm fiber length, and 0 initial chirp, a wide MIR-SC with a coverage range of 2.535 μm-16.6 μm is obtained. These numerical results are encouraging because they demonstrate that the spread of MIR-SC towards the red and blue ends can be manipulated by choosing the appropriate incident pulse and designing optimized fiber parameters, which contributes to applications in such diverse areas as spectroscopy, metrology and tomography.
    Effect of the target positions on the rapid identification of aluminum alloys by using filament-induced breakdown spectroscopy combined with machine learning
    Xiaoguang Li(李晓光), Xuetong Lu(陆雪童), Yong Zhang(张勇),Shaozhong Song(宋少忠), Zuoqiang Hao(郝作强), and Xun Gao(高勋)
    Chin. Phys. B, 2022, 31 (5):  054212.  DOI: 10.1088/1674-1056/ac3810
    Abstract ( 289 )   HTML ( 2 )   PDF (1206KB) ( 40 )  
    Filament-induced breakdown spectroscopy (FIBS) combined with machine learning algorithms was used to identify five aluminum alloys. To study the effect of the distance between focusing lens and target surface on the identification accuracy of aluminum alloys, principal component analysis (PCA) combined with support vector machine (SVM) and K-nearest neighbor (KNN) was used. The intensity and intensity ratio of fifteen lines of six elements (Fe, Si, Mg, Cu, Zn, and Mn) in the FIBS spectrum were selected. The distances between the focusing lens and the target surface in the pre-filament, filament, and post-filament were 958 mm, 976 mm, and 1000 mm, respectively. The source data set was fifteen spectral line intensity ratios, and the cumulative interpretation rates of PC1, PC2, and PC3 were 97.22%, 98.17%, and 95.31%, respectively. The first three PCs obtained by PCA were the input variables of SVM and KNN. The identification accuracy of the different positions of focusing lens and target surface was obtained, and the identification accuracy of SVM and KNN in the filament was 100% and 90%, respectively. The source data set of the filament was obtained by PCA for the first three PCs, which were randomly selected as the training set and test set of SVM and KNN in 3:2. The identification accuracy of SVM and KNN was 97.5% and 92.5%, respectively. The research results can provide a reference for the identification of aluminum alloys by FIBS.
    Noncollinear phase-matching geometries in ultra-broadband quasi-parametric amplification
    Ji Wang(王佶), Yanqing Zheng(郑燕青), and Yunlin Chen(陈云琳)
    Chin. Phys. B, 2022, 31 (5):  054213.  DOI: 10.1088/1674-1056/ac3a5b
    Abstract ( 285 )   HTML ( 0 )   PDF (1538KB) ( 22 )  
    Optical parametric chirped pulse amplification (OPCPA) shows great potential in producing ultrashort high-intensity pulses because of its large gain bandwidth. Quasi-parametric chirped pulse amplification (QPCPA) may further extend the bandwidth. However, behavior of QPCPA at a limited pump intensity (e.g., ≤ 5 GW/cm2 in a nanosecond pumped QPCPA) has not yet been investigated fully. We discuss detailedly the ultra-broadband amplification and the noncollinear phase-matching geometry in QPCPA, model and develop a novel noncollinear geometry in QPCPA, namely triple-wavelength phase-matching geometry, which provides two additional phase-matching points around the phase-matching point at the central wavelength. Our analysis demonstrates that the triple-wavelength phase-matching geometry can support stable, ultra-broadband amplification in QPCPA. The numerical simulation results show that ultrashort pulse with a pulse duration of 7.92 fs can be achieved in QPCPA when the pump intensity is limited to 5 GW/cm2, calculated using the nonlinear coefficient of YCa4O(BO3)3.
    Surface defects, stress evolution, and laser damage enhancement mechanism of fused silica under oxygen-enriched condition
    Wei-Yuan Luo(罗韦媛), Wen-Feng Sun(孙文丰), Bo Li(黎波), Xia Xiang(向霞), Xiao-Long Jiang(蒋晓龙),Wei Liao(廖威), Hai-Jun Wang(王海军), Xiao-Dong Yuan(袁晓东),Xiao-Dong Jiang(蒋晓东), and Xiao-Tao Zu(祖小涛)
    Chin. Phys. B, 2022, 31 (5):  054214.  DOI: 10.1088/1674-1056/ac5a3e
    Abstract ( 366 )   HTML ( 0 )   PDF (1468KB) ( 89 )  
    Oxygen ions (O+) were implanted into fused silica at a fixed fluence of 1×1017 ions/cm2 with different ion energies ranging from 10 keV to 60 keV. The surface roughness, optical properties, mechanical properties and laser damage performance of fused silica were investigated to understand the effect of oxygen ion implantation on laser damage resistance of fused silica. The ion implantation accompanied with sputtering effect can passivate the sub-/surface defects to reduce the surface roughness and improve the surface quality slightly. The implanted oxygen ions can combine with the structural defects (ODCs and E' centers) to reduce the defect densities and compensate the loss of oxygen in fused silica surface under laser irradiation. Furthermore, oxygen ion implantation can reduce the Si-O-Si bond angle and densify the surface structure, thus introducing compressive stress in the surface to strengthen the surface of fused silica. Therefore, the laser induced damage threshold of fused silica increases and the damage growth coefficient decreases when ion energy up to 30 keV. However, at higher ion energy, the sputtering effect is weakened and implantation becomes dominant, which leads to the surface roughness increase slightly. In addition, excessive energy aggravates the breaking of Si-O bonds. At the same time, the density of structural defects increases and the compressive stress decreases. These will degrade the laser laser-damage resistance of fused silica. The results indicate that oxygen ion implantation with appropriate ion energy is helpful to improve the damage resistance capability of fused silica components.
    Design of a polarization splitter for an ultra-broadband dual-core photonic crystal fiber
    Yongtao Li(李永涛), Jiesong Deng(邓洁松), Zhen Yang(阳圳), Hui Zou(邹辉), and Yuzhou Ma(马玉周)
    Chin. Phys. B, 2022, 31 (5):  054215.  DOI: 10.1088/1674-1056/ac3a63
    Abstract ( 343 )   HTML ( 0 )   PDF (1185KB) ( 95 )  
    A novel ultra-broadband polarization splitter based on a dual-core photonic crystal fiber (DC-PCF) is designed. The full-vector finite element method and coupled-mode theory are employed to investigate the characteristics of the polarization splitter. According to the numerical results, a graphene-filled layer not only broadens the working bandwidth but also reduces the size of the polarization splitter. Furthermore, the fluorine-doped region and the germanium-doped region can broaden the bandwidth. Also, the 4.78 mm long polarization splitter can achieve an extinction ratio of -98.6 dB at a wavelength of 1550 nm. When extinction ratio is less than -20 dB, the range of the wavelength is 1027 nm-1723 nm with a bandwidth of 696 nm. Overall, the polarization splitter can be applied to all-optical network communication systems in the infrared and near-infrared wavelength range.
    Temperature-responded tunable metalenses based on phase transition materials
    Jing-Jun Wu(伍景军), Feng Tang(唐烽), Jun Ma(马骏), Bing Han(韩冰), Cong Wei(魏聪), Qing-Zhi Li(李青芝), Jun Chen(陈骏), Ning Zhang(张宁), Xin Ye(叶鑫), Wan-Guo Zheng(郑万国), and Ri-Hong Zhu(朱日宏)
    Chin. Phys. B, 2022, 31 (5):  054216.  DOI: 10.1088/1674-1056/ac3cad
    Abstract ( 335 )   HTML ( 0 )   PDF (2473KB) ( 65 )  
    Once the metalenses are fabricated, the functions of most metalenses are invariable. The tunability and reconfigurability are useful and cost-saving for metalenses in realistic applications. We demonstrate this tunability here via a novel hybrid metalens with the strategic placement of an ultra-thin VO2 layer. The hybrid metalens is capable of dynamically modulating the focusing intensity of transmitted light at a wavelength of 1550 nm, and demonstrate a 42.28% focusing efficiency of the incident light and 70.01% modulation efficiency. The hybrid metalens' optothermal simulations show an optothermal conversion process of dynamic focusing, and a maximum laser density of 1.76×103 W/cm2 can be handled at an ambient temperature lower than 330 K. The hybrid metalens proposed in this work, a light-dose sensitive tunable smart metalens that can protect other instruments/systems or materials from being damaged, has its specific applications such as in anti-satellite blinding, bio-imaging, etc.
    An apodized cubic phase mask used in a wavefront coding system to extend the depth of field
    Lina Zhu(朱丽娜), Fei Li(李飞), Zeyu Huang(黄泽宇), and Tingyu Zhao(赵廷玉)
    Chin. Phys. B, 2022, 31 (5):  054217.  DOI: 10.1088/1674-1056/ac5979
    Abstract ( 271 )   HTML ( 0 )   PDF (4489KB) ( 75 )  
    The point spread function (PSF) caused by a wavefront coding system with a cubic phase mask has big side-lobes which leads to bad image restoration. This paper proposes a novel apodized cubic phase mask to suppress the side-lobes of the PSF. Simulated annealing algorithm is used to optimize the cubic and the truncation parameter of the phase mask. The system with the novel phase mask has better performance in the modulation transfer function (MTF) especially in low-and-medium spatial frequency region. The simulation results show that the restored images with the novel phase mask are superior to the one with the classic cubic phase mask in contrast and ringing effect. The experimental results show that the side-lobes of the PSF are suppressed by using the apodized cubic phase mask.
    Scanning the optical characteristics of lead-free cesium titanium bromide double perovskite nanocrystals
    Chenxi Yu(于晨曦), Long Gao(高龙), Wentong Li(李文彤), Qian Wang(王倩), Meng Wang(王萌), and Jiaqi Zhang(张佳旗)
    Chin. Phys. B, 2022, 31 (5):  054218.  DOI: 10.1088/1674-1056/ac5984
    Abstract ( 311 )   HTML ( 0 )   PDF (2379KB) ( 124 )  
    Cs2TiBr6 nanocrystals (NCs) are a type of promising optoelectronic materials, owing to their high photoelectric properties and non-toxicity. Here, we synthesize the colloidal Cs2TiBr6 NCs using a hot-injection approach. The temperature-dependent absorption data shows that its energy band changes about 30 meV with temperature, reflecting that its energy band structure is much stable. The excitation intensity-dependent transient absorption data confirms its linear absorption cross-sections and carrier recombination rate constants, involving monomolecular and bimolecular recombination, which are all superior to those of conventional perovskite bromide counterparts. In addition, its nonlinear absorption cross-sections are also measured based on femtosecond Z-scan. Our results suggest that Cs2TiBr6 NCs can be extensively applied in the field of optoelectronics, owing to its excellent carrier dynamics and nonlinear optical properties.
    Acoustic multipath structure in direct zone of deep water and bearing estimation of tow ship noise of towed line array
    Zhi-Bin Han(韩志斌), Zhao-Hui Peng (彭朝晖), Jun Song(宋俊), Lei Meng(孟雷), Xiu-Ting Yang(杨秀庭), and Bing Su(苏冰)
    Chin. Phys. B, 2022, 31 (5):  054301.  DOI: 10.1088/1674-1056/ac364e
    Abstract ( 327 )   HTML ( 1 )   PDF (1762KB) ( 109 )  
    In the towed line array sonar system, the tow ship noise is the main factor that affects the sonar performance. Conventional noise cancelling methods assume that the noise is towards the endfire direction of the array. An acoustic experiment employing a towed line array is conducted in the western Pacific Ocean, and a strange bearing-splitting phenomenon of the tow ship noise is observed in the array. The tow ship noise is split into multiple noise signals whose bearings are distributed between 10° and 90° deviating from the endfire direction. The multiple interferences increase the difficulty in recognizing the target for the sonar operator and noise cancellation. Therefore, making the mechanism clear and putting forward the tow ship noise splitting bearing estimation method are imperative. In this paper, the acoustic multi-path structure of the tow ship in deep water is analyzed. Then it is pointed out that the bearing-splitting phenomenon is caused by the main lobe of direct rays and bottom-reflected rays, as well as several side lobes of direct rays. Meanwhile, the indistinguishability between the elevation angle and the bearing angle due to the axial symmetry of a strict horizontal line array causes the bearing to deviate from the endfire direction. Based on the theory above, a method of estimating bearing of the tow ship noise in deep water is proposed. The theoretical analysis results accord with the experimental results, which helps to identify the target and provide correct initial bearing guidance for noise cancelation methods.
    Analysis on vibration characteristics of large-size rectangular piezoelectric composite plate based on quasi-periodic phononic crystal structure
    Li-Qing Hu(胡理情), Sha Wang(王莎), and Shu-Yu Lin(林书玉)
    Chin. Phys. B, 2022, 31 (5):  054302.  DOI: 10.1088/1674-1056/ac3649
    Abstract ( 277 )   HTML ( 0 )   PDF (1128KB) ( 62 )  
    Based on the theory of composite materials and phononic crystals (PCs), a large-size rectangular piezoelectric composite plate with the quasi-periodic PC structure composed of PZT-4 and epoxy is proposed in this paper. This PC structure can suppress the transverse vibration of the piezoelectric composite plate so that the thickness mode is purer and the thickness vibration amplitude is more uniform. Firstly, the vibration of the model is analyzed theoretically, the electromechanical equivalent circuit diagram of three-dimensional coupled vibration is established, and the resonance frequency equation is derived. The effects of the length, width, and thickness of the piezoelectric composite plate at the resonant frequency are obtained by the analytical method and the finite element method, the effective electromechanical coupling coefficient is also analyzed. The results show that the resonant frequency can be changed regularly and the electromechanical conversion can be improved by adjusting the size of the rectangular piezoelectric plate. The effect of the volume fraction of the scatterer on the resonant frequency in the thickness direction is studied by the finite element method. The band gap in X and Y directions of large-size rectangular piezoelectric plate with quasi-periodic PC structures are calculated. The results show that the theoretical results are in good agreement with the simulation results. When the resonance frequency is in the band gap, the decoupling phenomenon occurs, and then the vibration mode in the thickness direction is purer.
    Crown evolution kinematics of a camellia oil droplet impacting on a liquid layer
    Zhongyu Shi(石中玉), Guanqing Wang(王关晴), Xiangxiang Chen(陈翔翔), Lu Wang(王路), Ning Ding(丁宁), and Jiangrong Xu(徐江荣)
    Chin. Phys. B, 2022, 31 (5):  054701.  DOI: 10.1088/1674-1056/ac46c1
    Abstract ( 378 )   HTML ( 0 )   PDF (1186KB) ( 62 )  
    The phenomenon of droplet impact on an immiscible liquid is encountered in a variety of scenarios in nature and industrial production. Despite exhaustive research, it is not fully clear how the immiscibility of the liquid on which a droplet impacts affects the crown evolution. The present work experimentally investigates the evolution kinematics of a crown formed by the normal impact of a camellia oil droplet on an immiscible water layer. Based on discussion of dynamic impact behaviors for three critical Weber numbers (We), the radius of the crown and its average spreading velocity are compared with those of previous theoretical models to discuss their applicability to the immiscible liquid. The evolution kinematics (morphology and velocity) are analyzed by considering the effects of the We and layer thickness. Furthermore, the ability of crown expansion in radial and vertical directions is characterized by a velocity ratio. The results show that our experimental crown radius still follows a square-root function of evolution time, which agrees with the theoretical predictions. The dimensionless average spreading velocity decreases with We and follows a multivariate power law, while the dimensionless average rising velocity remains constant. The velocity ratio is shown to linearly increase with We, demonstrating that the rising movement in crown evolution gradually enhances with We. These results are helpful for further investigation on the droplet impact on an immiscible liquid layer.
    Nanobubbles produced by hydraulic air compression technique
    Xiaodong Yang(杨晓东), Qingfeng Yang(杨庆峰), Limin Zhou(周利民),Lijuan Zhang(张立娟), and Jun Hu(胡钧)
    Chin. Phys. B, 2022, 31 (5):  054702.  DOI: 10.1088/1674-1056/ac464c
    Abstract ( 322 )   HTML ( 3 )   PDF (822KB) ( 196 )  
    The anoxia of coastal water has already been a serious problem all over the word. Nanobubbles are proved to have great applications in water remediation because they could effectively increase the oxygen content and degrade organic matters in water. But the existing methods to produce nanobubbles are complicated and high cost to operate, especially in deep sea. In this paper, we presented a low-cost method, hydraulic air compression (HAC), to produce a large number of nanobubbles and proved that nanoscale gas bubbles could be produced by HAC for the first time. Nanoparticle tracking analysis was used to measure the size and concentration of produced nanobubbles. It indicated that the concentration of nanobubbles would increase as the downpipe height increases. Degassed measurements proved that produced “nanoparticles” are gas nanobubbles indeed. More dissolved oxygen in water would provide the source for larger number of nanobubble formation. Those results are expected to be very helpful for water remediation in ocean in the future.
    Effects of Landau damping and collision on stimulated Raman scattering with various phase-space distributions
    Shanxiu Xie(谢善秀), Yong Chen(陈勇), Junchen Ye(叶俊辰), Yugu Chen(陈雨谷), Na Peng(彭娜), and Chengzhuo Xiao(肖成卓)
    Chin. Phys. B, 2022, 31 (5):  055201.  DOI: 10.1088/1674-1056/ac3ba7
    Abstract ( 283 )   HTML ( 0 )   PDF (1395KB) ( 33 )  
    Stimulated Raman scattering (SRS) is one of the main instabilities affecting success of fusion ignition. Here, we study the relationship between Raman growth and Landau damping with various distribution functions combining the analytic formulas and Vlasov simulations. The Landau damping obtained by Vlasov-Poisson simulation and Raman growth rate obtained by Vlasov-Maxwell simulation are anti-correlated, which is consistent with our theoretical analysis quantitatively. Maxwellian distribution, flattened distribution, and bi-Maxwellian distribution are studied in detail, which represent three typical stages of SRS. We also demonstrate the effects of plateau width, hot-electron fraction, hot-to-cold electron temperature ratio, and collisional damping on the Landau damping and growth rate. They gives us a deep understanding of SRS and possible ways to mitigate SRS through manipulating distribution functions to a high Landau damping regime.
    Temperature dependence of bismuth structures under high pressure
    Xiaobing Fan(范小兵), Shikai Xiang(向士凯), and Lingcang Cai(蔡灵仓)
    Chin. Phys. B, 2022, 31 (5):  056101.  DOI: 10.1088/1674-1056/ac398d
    Abstract ( 317 )   HTML ( 2 )   PDF (2039KB) ( 107 )  
    It is unclear whether there is a liquid-liquid phase transition or not in the bismuth melt at high temperature and high pressure. If so, it will be necessary to confirm the boundary of the liquid-liquid phase transition and clarify whether it is a first-order phase transition. Here, based on x-ray absorption spectra and simulations, the temperature dependence of bismuth structures is investigated under different pressures. According to the similarity of characteristic peaks of x-ray absorption near edge structure (XANES) spectra, we estimate the possible temperature ranges of liquid-liquid phase transition to be 779-799 K at 2.74 GPa and 859-879 K at 2.78 GPa, 809-819 K at 3.38 GPa and 829-839 K at 3.39 GPa and 729-739 K at 4.78 GPa. Using ab initio molecular dynamics (AIMD) simulations, we obtain the stable structures of the bismuth melt at different temperatures and pressures, and calculated their electronic structures. Meanwhile, two stable phases (phase III-like and phase IV-like) of bismuth melts are obtained from different initial phases of bismuth solids (phase III and phase IV) under the same condition (3.20 GPa and 800 K). Assuming that the bismuth melt undergoes a phase transition from IV-like to III-like between 809 K and 819 K at 3.38 GPa, the calculated electronic structures are consistent with the XANES spectra, which provides a possible explanation for the first-order liquid-liquid phase transition.
    Small-angle neutron scattering study on the stability of oxide nanoparticles in long-term thermally aged 9Cr-oxide dispersion strengthened steel
    Peng-Lin Gao(高朋林), Jian Gong(龚建), Qiang Tian(田强), Gung-Ai Sun(孙光爱), Hai-Yang Yan(闫海洋),Liang Chen(陈良), Liang-Fei Bai(白亮飞), Zhi-Meng Guo(郭志猛), and Xin Ju(巨新)
    Chin. Phys. B, 2022, 31 (5):  056102.  DOI: 10.1088/1674-1056/ac43aa
    Abstract ( 419 )   HTML ( 1 )   PDF (1661KB) ( 88 )  
    A 9Cr-oxide dispersion strengthened (ODS) steel was thermally aged at 873 K for up to 5000 h. The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field. Combined with transmission electron microscopy, Vickers micro-hardness tests and electron backscattered diffraction measurements, all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix, which suggested excellent thermal stability of the 9Cr-ODS steel.
    How to realize an ultrafast electron diffraction experiment with a terahertz pump: A theoretical study
    Dan Wang(王丹), Xuan Wang(王瑄), Guoqian Liao(廖国前), Zhe Zhang(张喆), and Yutong Li(李玉同)
    Chin. Phys. B, 2022, 31 (5):  056103.  DOI: 10.1088/1674-1056/ac422d
    Abstract ( 287 )   HTML ( 2 )   PDF (1630KB) ( 111 )  
    To integrate a terahertz pump into an ultrafast electron diffraction (UED) experiment has attracted much attention due to its potential to initiate and detect the structural dynamics both directly. However, the deflection of the electron probe by the electromagnetic field of the terahertz pump alters the incident angle of the electron probe on the sample, impeding it from recording structural information afterwards. In this article, we studied this issue by a theoretical simulation of the terahertz-induced deflection effect on the electron probe, and came up with several possible schemes to reduce such effect. As a result, a terahertz-pump-electron-probe UED experiment with a temporal resolution comparable to the terahertz period is realized. We also found that MeV UED was more suitable for such terahertz pump experiment.
    Structural and thermodynamic properties of inhomogeneous fluids in rectangular corrugated nano-pores
    Yanshuang Kang(康艳霜), Haijun Wang(王海军), and Zongli Sun(孙宗利)
    Chin. Phys. B, 2022, 31 (5):  056104.  DOI: 10.1088/1674-1056/ac4237
    Abstract ( 286 )   HTML ( 1 )   PDF (1196KB) ( 32 )  
    Based on the free-energy average method, an area-weighted effective potential is derived for rectangular corrugated nano-pore. With the obtained potential, classical density functional theory is employed to investigate the structural and thermodynamic properties of confined Lennard-Jones fluid in rectangular corrugated slit pores. Firstly, influence of pore geometry on the adsorptive potential is calculated and analyzed. Further, thermodynamic properties including excess adsorption, solvation force, surface free energy and thermodynamic response functions are systematically investigated. It is found that pore geometry can largely modulate the structure of the confined fluids, which in turn influences other thermodynamic properties. In addition, the results show that different geometric elements have different influences on the confined fluids. The work provides an effective route to investigate the effect of roughness on confined fluids. It is expected to shed light on further understanding about interfacial phenomena near rough walls, and then provide useful clues for the design and characterization of novel materials.
    Alloying and magnetic disordering effects on phase stability of Co2 YGa (Y=Cr, V, and Ni) alloys: A first-principles study
    Chun-Mei Li(李春梅), Shun-Jie Yang(杨顺杰), and Jin-Ping Zhou(周金萍)
    Chin. Phys. B, 2022, 31 (5):  056105.  DOI: 10.1088/1674-1056/ac3986
    Abstract ( 306 )   HTML ( 1 )   PDF (1335KB) ( 29 )  
    The alloying and magnetic disordering effects on site occupation, elastic property, and phase stability of Co$_{2}Y$Ga ($Y={\rm Cr}$, V, and Ni) shape memory alloys are systematically investigated using the first-principles exact muffin-tin orbitals method. It is shown that with the increasing magnetic disordering degree $y$, their tetragonal shear elastic constant $C'$ (i.e., $(C_{11}-C_{12})/2$) of the $L2_{1}$ phase decreases whereas the elastic anisotropy $A$ increases, and upon tetragonal distortions the cubic phase gets more and more unstable. Co$_{2}$CrGa and Co$_{2}$VGa alloys with $y\geq0.2$ thus can show the martensitic transformation (MT) from $L2_{1}$ to $D0_{22}$ as well as Co$_{2}$NiGa. In off-stoichiometric alloys, the site preference is controlled by both the alloying and magnetic effects. At the ferromagnetism state, the excessive Ga atoms always tend to take the $Y$ sublattices, whereas the excessive Co atom favor the $Y$ sites when $Y={\rm Cr}$, and the excessive $Y$ atoms prefer the Co sites when $Y={\rm Ni}$. The Ga-deficient $Y={\rm V}$ alloys can also occur the MT at the ferromagnetism state by means of Co or V doping, and the MT temperature $T_{\rm M}$ should increase with their addition. In the corresponding ferromagnetism $Y={\rm Cr}$ alloys, nevertheless, with Co or Cr substituting for Ga, the reentrant MT (RMT) from $D0_{22}$ to $L2_{1}$ is promoted and then $T_{\rm M}$ for the RMT should decrease. The alloying effect on the MT of these alloys is finally well explained by means of the Jahn-Teller effect at the paramagnetic state. At the ferromagnetism state, it may originate from the competition between the austenite and martensite about their strength of the covalent banding between Co and Ga as well as $Y$ and Ga.
    Strategy to mitigate single event upset in 14-nm CMOS bulk FinFET technology
    Dong-Qing Li(李东青), Tian-Qi Liu(刘天奇), Pei-Xiong Zhao(赵培雄), Zhen-Yu Wu(吴振宇), Tie-Shan Wang(王铁山), and Jie Liu(刘杰)
    Chin. Phys. B, 2022, 31 (5):  056106.  DOI: 10.1088/1674-1056/ac3d7e
    Abstract ( 400 )   HTML ( 3 )   PDF (2993KB) ( 125 )  
    Three-dimensional (3D) TCAD simulations demonstrate that reducing the distance between the well boundary and N-channel metal-oxide semiconductor (NMOS) transistor or P-channel metal-oxide semiconductor (PMOS) transistor can mitigate the cross section of single event upset (SEU) in 14-nm complementary metal-oxide semiconductor (CMOS) bulk FinFET technology. The competition of charge collection between well boundary and sensitive nodes, the enhanced restoring currents and the change of bipolar effect are responsible for the decrease of SEU cross section. Unlike dual-interlock cell (DICE) design, this approach is more effective under heavy ion irradiation of higher LET, in the presence of enough taps to ensure the rapid recovery of well potential. Besides, the feasibility of this method and its effectiveness with feature size scaling down are discussed.
    Combined effects of cycling endurance and total ionizing dose on floating gate memory cells
    Si-De Song(宋思德), Guo-Zhu Liu(刘国柱), Qi He(贺琪), Xiang Gu(顾祥), Gen-Shen Hong(洪根深), and Jian-Wei Wu(吴建伟)
    Chin. Phys. B, 2022, 31 (5):  056107.  DOI: 10.1088/1674-1056/ac3d80
    Abstract ( 312 )   HTML ( 0 )   PDF (1359KB) ( 46 )  
    The combined effects of cycling endurance and radiation on floating gate memory cell are investigated in detail, and the obtained results are listed below. (i) The programmed flash cells with a prior appropriate number of program and easing cycling stress exhibit much smaller threshold voltage shift than without those in response to radiation, which is ascribed mainly to the recombination of trapped electrons (introduced by cycling stress) and trapped holes (introduced by irradiation) in the oxide surrounding the floating gate. (ii) The radiation induced transconductance degradation in prior cycled flash cell is more severe than those without cycling stress in the programmed state or erased state. (iii) Radiation is more likely to set up the interface generation in programmed state than in erased state. This paper will be useful in understanding the issues involved in cycling endurance and radiation effects as well as in designing radiation hardened floating gate memory cells.
    Assessing the effect of hydrogen on the electronic properties of 4H-SiC
    Yuanchao Huang(黄渊超), Rong Wang(王蓉), Yiqiang Zhang(张懿强), Deren Yang(杨德仁), and Xiaodong Pi(皮孝东)
    Chin. Phys. B, 2022, 31 (5):  056108.  DOI: 10.1088/1674-1056/ac4234
    Abstract ( 358 )   HTML ( 0 )   PDF (1043KB) ( 159 )  
    As a common impurity in 4H silicon carbide (4H-SiC), hydrogen (H) may play a role in tuning the electronic properties of 4H-SiC. In this work, we systemically explore the effect of H on the electronic properties of both n-type and p-type 4H-SiC. The passivation of H on intrinsic defects such as carbon vacancies (VC) and silicon vacancies (VSi) in 4H-SiC is also evaluated. We find that interstitial H at the bonding center of the Si-C bond (Hibc) and interstitial H at the tetrahedral center of Si (HiSi-te) dominate the defect configurations of H in p-type and n-type 4H-SiC, respectively. In n-type 4H-SiC, the compensation of HiSi-te is found to pin the Fermi energy and hinder the increase of the electron concentration for highly N-doped 4H-SiC. The compensation of Hibc is negligible compared to that of VC on the p-type doping of Al-doped 4H-SiC. We further examine whether H can passivate VC and improve the carrier lifetime in 4H-SiC. It turns out that nonequilibrium passivation of VC by H is effective to eliminate the defect states of VC, which enhances the carrier lifetime of moderately doped 4H-SiC. Regarding the quantum-qubit applications of 4H-SiC, we find that H can readily passivate VSi during the creation of VSi centers. Thermal annealing is needed to decompose the resulting VSi-nH (n=1-4) complexes and promote the uniformity of the photoluminescence of VSi arrays in 4H-SiC. The current work may inspire the impurity engineering of H in 4H-SiC.
    Raman spectroscopy investigation on the pressure-induced structural and magnetic phase transition in two-dimensional antiferromagnet FePS3
    Hong Zeng(曾鸿), Tingting Ye(叶婷婷), Peng Cheng(程鹏), Deyuan Yao(姚德元), and Junfeng Ding(丁俊峰)
    Chin. Phys. B, 2022, 31 (5):  056109.  DOI: 10.1088/1674-1056/ac5a41
    Abstract ( 348 )   HTML ( 3 )   PDF (2948KB) ( 182 )  
    The layered van der Waals antiferromagnetic FePS3 has received considerable attention because long range magnetic ordering can remain with single atoms layer, which offers potential applications in future ultrathin devices. Here, we perform Raman spectroscopy to systematically explore the variations of lattice vibration and crystal structure under pressure up to 18.9 GPa. We observe two structural phase transitions at approximately 4 GPa and 13 GPa, respectively. Moreover, by monitoring spin-related Raman modes, we demonstrate a pressure-induced magnetic structure transition above 2 GPa. These modes disappear accompanying the second structural phase transition and insulator-to-metal transition (IMT), indicating the suppression of long-range magnetic ordering, in agreement with earlier neutron powder diffraction experiments.
    Pressure-induced phase transitions in the ZrXY (X= Si, Ge, Sn;Y= S, Se, Te) family compounds Hot!
    Qun Chen(陈群), Juefei Wu(吴珏霏), Tong Chen(陈统), Xiaomeng Wang(王晓梦), Chi Ding(丁弛), Tianheng Huang(黄天衡), Qing Lu(鲁清), and Jian Sun(孙建)
    Chin. Phys. B, 2022, 31 (5):  056201.  DOI: 10.1088/1674-1056/ac5989
    Abstract ( 515 )   HTML ( 5 )   PDF (6039KB) ( 376 )  
    Pressure is an effective and clean way to modify the electronic structures of materials, cause structural phase transitions and even induce the emergence of superconductivity. Here, we predicted several new phases of the ZrXY family at high pressures using the crystal structures search method together with first-principle calculations. In particular, the ZrGeS compound undergoes an isosymmetric phase transition from P4/nmm-I to P4/nmm-II at approximately 82 GPa. Electronic band structures show that all the high-pressure phases are metallic. Among these new structures, P4/nmm-II ZrGeS and P4/mmm ZrGeSe can be quenched to ambient pressure with superconducting critical temperatures of approximately 8.1 K and 8.0 K, respectively. Our study provides a way to tune the structure, electronic properties, and superconducting behavior of topological materials through pressure.
    Impact of thermostat on interfacial thermal conductance prediction from non-equilibrium molecular dynamics simulations
    Song Hu(胡松), C Y Zhao(赵长颖), and Xiaokun Gu(顾骁坤)
    Chin. Phys. B, 2022, 31 (5):  056301.  DOI: 10.1088/1674-1056/ac4238
    Abstract ( 331 )   HTML ( 2 )   PDF (1412KB) ( 35 )  
    The knowledge of interfacial thermal conductance (ITC) is key to understand thermal transport in nanostructures. The non-equilibrium molecular dynamics (NEMD) simulation is a useful tool to calculate the ITC. In this study, we investigate the impact of thermostat on the prediction of the ITC. The Langevin thermostat is found to result in larger ITC than the Nose-Hoover thermostat. In addition, the results from NEMD simulations with the Nose-Hoover thermostat exhibit strong size effect of thermal reservoirs. Detailed spectral heat flux decomposition and modal temperature calculation reveal that the acoustic phonons in hot and cold thermal reservoirs are of smaller temperature difference than optical phonons when using the Nose-Hoover thermostat, while phonons in the Langevin thermostat are of identical temperatures. Such a non-equilibrium state of phonons in the case of the Nose-Hoover thermostat reduces the heat flux of low-to-middle-frequency phonons. We also discuss how enlarging the reservoirs or adding an epitaxial rough wall to the reservoirs affects the predicted ITC, and find that these attempts could help to thermalize the phonons, but still underestimate the heat flux from low-frequency phonons.
    Evaluation of performance of machine learning methods in mining structure—property data of halide perovskite materials
    Ruoting Zhao(赵若廷), Bangyu Xing(邢邦昱), Huimin Mu(穆慧敏), Yuhao Fu(付钰豪), and Lijun Zhang(张立军)
    Chin. Phys. B, 2022, 31 (5):  056302.  DOI: 10.1088/1674-1056/ac5d2d
    Abstract ( 482 )   HTML ( 4 )   PDF (1248KB) ( 441 )  
    With the rapid development of artificial intelligence and machine learning (ML) methods, materials science is rapidly entering the era of data-driven materials informatics. ML models serve as the most crucial component, closely bridging material structure and material properties. There is a considerable difference in the prediction performance of different ML methods for material systems. Herein, we evaluated three categories (linear, kernel, and nonlinear methods) of models, with twelve ML algorithms commonly used in the materials field. In addition, halide perovskite was chosen as an example to evaluate the fitting performance of different models. We constructed a total dataset of 540 halide perovskites and 72 features, with formation energy and bandgap as target properties. We found that different categories of ML models show similar trends for different target properties. Among them, the difference between the models is enormous for the formation energy, with the coefficient of determination (R2) range 0.69-0.953. The fitting performance between the models is closer for bandgap, with the R2 range 0.941-0.997. The nonlinear-ensemble model shows the best fitting performance for both the formation energy and the bandgap. It shows that the nonlinear-ensemble model, constructed by combining multiple weak learners, effectively describes the nonlinear relationship between material features and target property. In addition, the extreme gradient boosting decision tree model shows the most superior results among all the models and searches for two new descriptors that are crucial for formation energy and bandgap. Our work provides useful guidance for the selection of effective machine learning methods in the data-mining studies of specific material systems. The dataset that supported the findings of this study is available in Science Data Bank, with the link https://www.doi.org/10.11922/sciencedb.01611.
    Water contact angles on charged surfaces in aerosols Hot!
    Yu-Tian Shen(申钰田), Ting Lin(林挺), Zhen-Ze Yang(杨镇泽), Yong-Feng Huang(黄永峰), Ji-Yu Xu(徐纪玉), and Sheng Meng(孟胜)
    Chin. Phys. B, 2022, 31 (5):  056801.  DOI: 10.1088/1674-1056/ac5c2f
    Abstract ( 397 )   HTML ( 1 )   PDF (903KB) ( 226 )  
    Interactions between water and solid substrates are of fundamental importance to various processes in nature and industry. Electric control is widely used to modify interfacial water, where the influence of surface charges is inevitable. Here we obtain positively and negatively charged surfaces using LiTaO3 crystals and observe that a large net surface charge up to 0.1 C/m2 can nominally change the contact angles of pure water droplets comparing to the same uncharged surface. However, even a small amount of surface charge can efficiently increase the water contact angle in the presence of aerosols. Our results indicate that such surface charges can hardly affect the structure of interfacial water molecular layers and the morphology of the macroscopic droplet, while adsorption of a small amount of organic contaminants from aerosols with the help of Coulomb attraction can notably decrease the wettability of solid surface. Our results not only provide a fundamental understanding of the interactions between charged surfaces and water, but also help to develop new techniques on electric control of wettability and microfluidics in real aerosol environments.
    First-principles calculations of the hole-induced depassivation of SiO2/Si interface defects
    Zhuo-Cheng Hong(洪卓呈), Pei Yao(姚佩), Yang Liu(刘杨), and Xu Zuo(左旭)
    Chin. Phys. B, 2022, 31 (5):  057101.  DOI: 10.1088/1674-1056/ac3506
    Abstract ( 282 )   HTML ( 2 )   PDF (2302KB) ( 41 )  
    The holes induced by ionizing radiation or carrier injection can depassivate saturated interface defects. The depassivation of these defects suggests that the deep levels associated with the defects are reactivated, affecting the performance of devices. This work simulates the depassivation reactions between holes and passivated amorphous-SiO2/Si interface defects (HPb+h→ Pb+H+). The climbing image nudged elastic band method is used to calculate the reaction curves and the barriers. In addition, the atomic charges of the initial and final structures are analyzed by the Bader charge method. It is shown that more than one hole is trapped by the defects, which is implied by the reduction in the total number of valence electrons on the active atoms. The results indicate that the depassivation of the defects by the holes actually occurs in three steps. In the first step, a hole is captured by the passivated defect, resulting in the stretching of the Si-H bond. In the second step, the defect captures one more hole, which may contribute to the breaking of the Si-H bond. The H atom is released as a proton and the Si atom is three-coordinated and positively charged. In the third step, an electron is captured by the Si atom, and the Si atom becomes neutral. In this step, a Pb-type defect is reactivated.
    Evolution of optical properties and molecular structure of PCBM films under proton irradiation
    Guo-Dong Xiong(熊国栋), Hui-Ping Zhu(朱慧平), Lei Wang(王磊), Bo Li(李博), Fa-Zhan Zhao(赵发展), and Zheng-Sheng Han(韩郑生)
    Chin. Phys. B, 2022, 31 (5):  057102.  DOI: 10.1088/1674-1056/ac322b
    Abstract ( 294 )   HTML ( 0 )   PDF (2543KB) ( 45 )  
    Low-energy proton irradiation effects on the optical properties and the molecular structure of phenyl-C61-butyric acid methyl ester (PCBM) are studied in this work. The PCBM films are irradiated by 100-keV proton beams with fluences of 5×1012 p/cm2, 5×1013 p/cm2, and 5×1014 p/cm2, respectively. The photoluminescence (PL) peaks of the post-irradiated PCBM films show a progressive decrease in the peak intensity as the proton fluences increase, which can be attributed to the deep defect levels induced by proton irradiation. Additionally, a slight blue-shift in the PL spectrum is also observed at a proton fluence of 5×1014 p/cm2. The underlying mechanism can be traced back to the lift of the lowest unoccupied molecular orbital (LUMO) level, which is caused by the attachment of methoxy radicals on ortho position of the phenyl ring in the post-irradiated PCBM structure. This work is of significance in understanding the radiation hardness and the damage mechanism of the PCBM film in radiation environments, which is essential before it is put into practical application in space.
    Maximum entropy mobility spectrum analysis for the type-I Weyl semimetal TaAs
    Wen-Chong Li(李文充), Ling-Xiao Zhao(赵凌霄), Hai-Jun Zhao(赵海军),Gen-Fu Chen(陈根富), and Zhi-Xiang Shi(施智祥)
    Chin. Phys. B, 2022, 31 (5):  057103.  DOI: 10.1088/1674-1056/ac2b24
    Abstract ( 296 )   HTML ( 1 )   PDF (989KB) ( 56 )  
    Due to non-saturating magnetoresistance (MR) and the special compensation mechanism, the Weyl semimetal TaAs single crystal has attracted considerable attention in condensed matter physics. Herein, we use maximum entropy mobility spectrum analysis (MEMSA) to extract charge carrier information by fitting the experimentally measured longitudinal and transverse electric transport curves of TaAs. The carrier types and the number of bands are obtained without any hypothesis. Study of the temperature dependence shows details of carrier property evolution. Our quantitative results explain the non-saturated magnetoresistance and Hall sign change phenomena of TaAs.
    Chiral splitting of Kondo peak in triangular triple quantum dot
    Yi-Ming Liu(刘一铭), Yuan-Dong Wang(王援东), and Jian-Hua Wei(魏建华)
    Chin. Phys. B, 2022, 31 (5):  057201.  DOI: 10.1088/1674-1056/ac29a5
    Abstract ( 310 )   HTML ( 2 )   PDF (1081KB) ( 69 )  
    New characteristics of the Kondo effect, arising from spin chirality induced by the Berry phase in the equilibrium state, are investigated. The analysis is based on the hierarchical equations of motion (HEOM) approach in a triangular triple quantum-dot (TTQD) structure. In the absence of magnetic field, TTQD has four-fold degenerate chiral ground states with degenerate spin chirality. When a perpendicular magnetic field is applied, the chiral interaction is induced by the magnetic flux threading through TTQD and the four-fold degenerate states split into two chiral state pairs. The chiral excited states manifest as chiral splitting of the Kondo peak in the spectral function. The theoretical analysis is confirmed by the numerical computations. Furthermore, under a Zeeman magnetic field B, the chiral Kondo peak splits into four peaks, owing to the splitting of spin freedom. The influence of spin chirality on the Kondo effect signifies an important role of the phase factor. This work provides insight into the quantum transport of strongly correlated electronic systems.
    Ferroelectric Ba0.75Sr0.25TiO3 tunable charge transfer in perovskite devices
    Zi-Xuan Chen(陈子轩), Jia-Lin Sun(孙家林), Qiang Zhang(张强), Chong-Xin Qian(钱崇鑫), Ming-Zi Wang(王明梓), and Hong-Jian Feng(冯宏剑)
    Chin. Phys. B, 2022, 31 (5):  057202.  DOI: 10.1088/1674-1056/ac46c3
    Abstract ( 426 )   HTML ( 4 )   PDF (2034KB) ( 108 )  
    Interfacial charge recombination is a main issue causing the efficiency loss of the perovskite solar cells (PSCs). Here, ferroelectric Ba0.75Sr0.25TiO3 (BST) is introduced as a polarization tunable layer to promote the interfacial charge transfer of the PSCs. The coexistence of ferroelectric polarization and charge carriers in BST is confirmed by density functional theory (DFT) calculations. Experimental characterization demonstrates the polarization reversal and the existence of domain in BST film. The BST film conductivity is tested as 2.98×10-4 S/cm, which is comparable to the TiO2 being used as the electron transporting layer (ETL) in PSCs. The calculations results prove that BST can be introduced into the PSCs and the interfacial charge transfer can be tuned by ferroelectric polarization. Thus, we fabricated the BST-based PSCs with a champion power conversion efficiency (PCE) of 19.05% after poling.
    Improved device performance of recessed-gate AlGaN/GaN HEMTs by using in-situ N2O radical treatment
    Xinchuang Zhang(张新创), Mei Wu(武玫), Bin Hou(侯斌), Xuerui Niu(牛雪锐), Hao Lu(芦浩), Fuchun Jia(贾富春), Meng Zhang(张濛), Jiale Du(杜佳乐), Ling Yang(杨凌), Xiaohua Ma(马晓华), and Yue Hao(郝跃)
    Chin. Phys. B, 2022, 31 (5):  057301.  DOI: 10.1088/1674-1056/ac48fb
    Abstract ( 366 )   HTML ( 0 )   PDF (2309KB) ( 139 )  
    The N2O radicals in-situ treatment on gate region has been employed to improve device performance of recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). The samples after gate recess etching were treated by N2O radicals without physical bombardment. After in-situ treatment (IST) processing, the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST. The fabricated HEMTs with the IST process show a low reverse gate current of 10-9 A/mm, high on/off current ratio of 108, and high fT×Lg of 13.44 GHz· μm. A transmission electron microscope (TEM) imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface. X-ray photoelectron spectroscopy (XPS) measurement shows that the content of the Al-O and Ga-O bonds elevated after IST, indicating that the Al-N and Ga-N bonds on the AlGaN surface were broken and meanwhile the Al-O and Ga-O bonds formed. The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.
    Topological Lifshitz transition and novel edge states induced by non-Abelian SU(2) gauge field on bilayer honeycomb lattice
    Wen-Xiang Guo(郭文祥) and Wu-Ming Liu(刘伍明)
    Chin. Phys. B, 2022, 31 (5):  057302.  DOI: 10.1088/1674-1056/ac3ecb
    Abstract ( 332 )   HTML ( 0 )   PDF (5640KB) ( 121 )  
    We investigate the SU(2) gauge effects on bilayer honeycomb lattice thoroughly. We discover a topological Lifshitz transition induced by the non-Abelian gauge potential. Topological Lifshitz transitions are determined by topologies of Fermi surfaces in the momentum space. Fermi surface consists of N = 8 Dirac points at π-flux point instead of N = 4 in the trivial Abelian regimes. A local winding number is defined to classify the universality class of the gapless excitations. We also obtain the phase diagram of gauge fluxes by solving the secular equation. Furthermore, the novel edge states of biased bilayer nanoribbon with gauge fluxes are also investigated.
    Bias-induced reconstruction of hybrid interface states in magnetic molecular junctions
    Ling-Mei Zhang(张令梅), Yuan-Yuan Miao(苗圆圆), Zhi-Peng Cao(曹智鹏), Shuai Qiu(邱帅), Guang-Ping Zhang(张广平), Jun-Feng Ren(任俊峰), Chuan-Kui Wang(王传奎), and Gui-Chao Hu(胡贵超)
    Chin. Phys. B, 2022, 31 (5):  057303.  DOI: 10.1088/1674-1056/ac3caf
    Abstract ( 272 )   HTML ( 1 )   PDF (1700KB) ( 78 )  
    Based on first-principles calculations, the bias-induced evolutions of hybrid interface states in π-conjugated tricene and in insulating octane magnetic molecular junctions are investigated. Obvious bias-induced splitting and energy shift of the spin-resolved hybrid interface states are observed in the two junctions. The recombination of the shifted hybrid interface states from different interfaces makes the spin polarization around the Fermi energy strongly bias-dependent. The transport calculations demonstrate that in the π -conjugated tricene junction, the bias-dependent hybrid interface states work efficiently for large current, current spin polarization, and distinct tunneling magnetoresistance. But in the insulating octane junction, the spin-dependent transport via the hybrid interface states is inhibited, which is only slightly disturbed by the bias. This work reveals the phenomenon of bias-induced reconstruction of hybrid interface states in molecular spinterface devices, and the underlying role of conjugated molecular orbitals in the transport ability of hybrid interface states.
    Generalization of the theory of three-dimensional quantum Hall effect of Fermi arcs in Weyl semimetal Hot!
    Mingqi Chang(苌名起), Yunfeng Ge(葛云凤), and Li Sheng(盛利)
    Chin. Phys. B, 2022, 31 (5):  057304.  DOI: 10.1088/1674-1056/ac5c32
    Abstract ( 382 )   HTML ( 4 )   PDF (2213KB) ( 184 )  
    The quantum Hall effect (QHE), which is usually observed in two-dimensional systems, was predicted theoretically and observed experimentally in three-dimensional (3D) topological semimetal. However, there are some inconsistencies between the theory and the experiments showing the theory is imperfect. Here, we generalize the theory of the 3D QHE of Fermi arcs in Weyl semimetal. Through calculating the sheet Hall conductivity of a Weyl semimetal slab, we show that the 3D QHE of Fermi arcs can occur in a large energy range and the thickness dependences of the QHE in different Fermi energies are distinct. When the Fermi energy is near the Weyl nodes, the Fermi arcs give rise to the QHE which is independent of the thickness of the slab. When the Fermi energy is not near the Weyl nodes, the two Fermi arcs form a complete Fermi loop with the assistance of bulk states giving rise to the QHE which is dependent on the sample thickness. We also demonstrate how the band anisotropic terms influence the QHE of Fermi arcs. Our theory complements the imperfections of the present theory of 3D QHE of Fermi arcs.
    Preparation of PSFO and LPSFO nanofibers by electrospinning and their electronic transport and magnetic properties
    Ying Su(苏影), Dong-Yang Zhu(朱东阳), Ting-Ting Zhang(张亭亭), Yu-Rui Zhang(张玉瑞), Wen-Peng Han(韩文鹏), Jun Zhang(张俊), Seeram Ramakrishna, and Yun-Ze Long(龙云泽)
    Chin. Phys. B, 2022, 31 (5):  057305.  DOI: 10.1088/1674-1056/ac3baa
    Abstract ( 305 )   HTML ( 1 )   PDF (2668KB) ( 41 )  
    Pr0.5Sr0.5FeO3 (PSFO) and La0.25Pr0.25Sr0.5FeO3 (LPSFO) nanofibers are prepared by electrospinning followed by calcination, and their morphologies, microstructures, electronic transports, and magnetic properties are studied systematically. The temperature-dependent resistance curves of PSFO and LPSFO nanofibers are measured in a temperature range from 300 K to 10 K. With the temperature lowering, the resistance increases gradually and then decreases sharply due to the occurrence of ferromagnetic metal phase. The metal-insulator transition temperatures are about 110 K and 180 K for PSFO and LPSFO nanofibers, respectively. The electronic conduction behavior above the transition temperature can be described by one-dimensional Mott's variable-range hopping (VRH) model. The hysteresis loops and the field-cooled (FC) and zero-field-cooled (ZFC) curves show that both PSFO nanofiber and LPSFO nanofiber exhibit ferromagnetism. Although the doping of La reduces the overall magnetization intensity of the material, it increases the ferromagnetic ratio of the system, which may improve the performance of LPSFO in solid oxide fuel cell.
    Photon number resolvability of multi-pixel superconducting nanowire single photon detectors using a single flux quantum circuit
    Hou-Rong Zhou(周后荣), Kun-Jie Cheng(程昆杰), Jie Ren(任洁), Li-Xing You(尤立星),Li-Liang Ying(应利良), Xiao-Yan Yang(杨晓燕), Hao Li(李浩), and Zhen Wang(王镇)
    Chin. Phys. B, 2022, 31 (5):  057401.  DOI: 10.1088/1674-1056/ac398a
    Abstract ( 322 )   HTML ( 3 )   PDF (2016KB) ( 68 )  
    Superconducting nanowire single-photon detectors (SNSPDs) are typical switching devices capable of detecting single photons with almost 100% detection efficiency. However, they cannot determine the exact number of incident photons during a detection event. Multi-pixel SNSPDs employing multiple read-out channels can provide photon number resolvability (PNR), but they require increased cooling power and costly multi-channel electronic systems. In this work, a single-flux quantum (SFQ) circuit is employed, and PNR based on multi-pixel SNSPDs is successfully demonstrated. A multi-input magnetically coupled DC/SFQ converter (MMD2Q) circuit with a mutual inductance M is used to combine and record signals from a multi-pixel SNSPD device. The designed circuit is capable of discriminating the amplitude of the combined signals in accuracy of Φ0/M with Φ0 being a single magnetic flux quantum. By employing the MMD2Q circuit, the discrimination of up to 40 photons can be simulated. A 4-parallel-input MMD2Q circuit is fabricated, and a PNR of 3 is successfully demonstrated for an SNSPD array with one channel reserved for the functional verification. The results confirm that an MMD2Q circuit is an effective tool for implementing PNR with multi-pixel SNSPDs.
    Asymmetric Fraunhofer pattern in Josephson junctions from heterodimensional superlattice V5S8 Hot!
    Juewen Fan(范珏雯), Bingyan Jiang(江丙炎), Jiaji Zhao(赵嘉佶), Ran Bi(毕然), Jiadong Zhou(周家东), Zheng Liu(刘政), Guang Yang(杨光), Jie Shen(沈洁), Fanming Qu(屈凡明), Li Lu(吕力), Ning Kang(康宁), and Xiaosong Wu(吴孝松)
    Chin. Phys. B, 2022, 31 (5):  057402.  DOI: 10.1088/1674-1056/ac5d30
    Abstract ( 595 )   HTML ( 5 )   PDF (1074KB) ( 305 )  
    Introduction of spin-orbit coupling (SOC) in a Josephson junction (JJ) gives rise to unusual Josephson effects. We investigate JJs based on a newly discovered heterodimensional superlattice V5S8 with a special form of SOC. The unique homointerface of our JJs enables elimination of extrinsic effects due to interfaces and disorder. We observe asymmetric Fraunhofer patterns with respect to both the perpendicular magnetic field and the current. The asymmetry is influenced by an in-plane magnetic field. Analysis of the pattern points to a nontrivial spatial distribution of the Josephson current that is intrinsic to the SOC in V5S8.
    SPECIAL TOPIC—Superconductivity in vanadium-based kagome materials
    Surface-induced orbital-selective band reconstruction in kagome superconductor CsV3Sb5
    Linwei Huai(淮琳崴), Yang Luo(罗洋), Samuel M. L. Teicher, Brenden R. Ortiz, Kaize Wang(王铠泽),Shuting Peng(彭舒婷), Zhiyuan Wei(魏志远), Jianchang Shen(沈建昌), Bingqian Wang(王冰倩), Yu Miao(缪宇),Xiupeng Sun(孙秀鹏), Zhipeng Ou(欧志鹏), Stephen D. Wilson, and Junfeng He(何俊峰)
    Chin. Phys. B, 2022, 31 (5):  057403.  DOI: 10.1088/1674-1056/ac4f50
    Abstract ( 453 )   HTML ( 6 )   PDF (1156KB) ( 197 )  
    The two-dimensional (2D) kagome superconductor CsV3Sb5 has attracted much recent attention due to the coexistence of superconductivity, charge orders, topology and kagome physics, which manifest themselves as distinct electronic structures in both bulk and surface states of the material. An interesting next step is to manipulate the electronic states in this system. Here, we report angle-resolved photoemission spectroscopy (ARPES) evidence for a surface-induced orbital-selective band reconstruction in CsV3Sb5. A significant energy shift of the electron-like band around Γ and a moderate energy shift of the hole-like band around M are observed as a function of time. This evolution is reproduced in a much shorter time scale by in-situ annealing of the CsV3Sb5 sample. Orbital-resolved density functional theory (DFT) calculations reveal that the momentum-dependent band reconstruction is associated with different orbitals for the bands around Γ and M, and the time-dependent evolution points to the change of sample surface that is likely caused by the formation of Cs vacancies on the surface. Our results indicate the possibility of orbital-selective control of the band structure via surface modification, which may open a new avenue for manipulating exotic phenomena in this material system, including superconductivity.
    Measurement of electronic structure in van der Waals ferromagnet Fe5-xGeTe2
    Kui Huang(黄逵), Zhenxian Li(李政贤), Deping Guo(郭的坪), Haifeng Yang(杨海峰), Yiwei Li(李一苇),Aiji Liang(梁爱基), Fan Wu(吴凡), Lixuan Xu(徐丽璇), Lexian Yang(杨乐仙), Wei Ji(季威),Yanfeng Guo(郭艳峰), Yulin Chen(陈宇林), and Zhongkai Liu(柳仲楷)
    Chin. Phys. B, 2022, 31 (5):  057404.  DOI: 10.1088/1674-1056/ac5c3c
    Abstract ( 408 )   HTML ( 4 )   PDF (4622KB) ( 227 )  
    As a van der Waals ferromagnet with high Curie temperature, Fe5-xGeTe2 has attracted tremendous interests recently. Here, using high-resolution angle-resolved photoemission spectroscopy (ARPES), we systematically investigated the electronic structure of Fe5-xGeTe2 crystals and its temperature evolution. Our ARPES measurement reveals two types of band structures from two different terminations with slight kz evolution. Interestingly, across the ferromagnetic transition, we observed the merging of two split bands above the Curie temperature, suggesting the band splitting due to the exchange interaction within the itinerant Stoner model. Our results provide important insights into the electronic and magnetic properties of Fe5-xGeTe2 and the understanding of magnetism in a two-dimensional ferromagnetic system.
    Dynamical signatures of the one-dimensional deconfined quantum critical point Hot!
    Ning Xi(西宁) and Rong Yu(俞榕)
    Chin. Phys. B, 2022, 31 (5):  057501.  DOI: 10.1088/1674-1056/ac5987
    Abstract ( 407 )   HTML ( 8 )   PDF (3436KB) ( 219 )  
    We study the critical scaling and dynamical signatures of fractionalized excitations at two different deconfined quantum critical points (DQCPs) in an S = 1/2 spin chain using the time evolution of infinite matrix product states. The scaling of the correlation functions and the dispersion of the conserved current correlations explicitly show the emergence of enhanced continuous symmetries at these DQCPs. The dynamical structure factors in several different channels reveal the development of deconfined fractionalized excitations at the DQCPs. Furthermore, we find an effective spin-charge separation at the DQCP between the ferromagnetic (FM) and valence bond solid (VBS) phases, and identify two continua associated with different types of fractionalized excitations at the DQCP between the X-direction and Z-direction FM phases. Our findings not only provide direct evidence for the DQCP in one dimension but also shed light on exploring the DQCP in higher dimensions.
    Effects of phosphorus doping on the physical properties of axion insulator candidate EuIn2As2 Hot!
    Feihao Pan(潘斐豪), Congkuan Tian(田丛宽), Jiale Huang(黄嘉乐), Daye Xu(徐大业), Jinchen Wang (汪晋辰), Peng Cheng(程鹏), Juanjuan Liu(刘娟娟), and Hongxia Zhang(张红霞)
    Chin. Phys. B, 2022, 31 (5):  057502.  DOI: 10.1088/1674-1056/ac5d2c
    Abstract ( 343 )   HTML ( 0 )   PDF (1336KB) ( 199 )  
    We report an investigation on the single crystal growth, magnetic and transport properties of EuIn2(As1-xPx)2 (0≤x≤ 1). The physical properties of axion insulator candidate EuIn2As2 can be effectively tuned by P-doping. With increasing x, the c-axis lattice parameter decreases linearly, the magnetic transition temperature gradually increases and ferromagnetic interactions are enhanced. This is similar to the previously reported high pressure effect on EuIn2As2. For x=0.40, a spin glass state at Tg=10 K emerges together with the observations of a butter-fly shaped magnetic hysteresis and slow magnetic behavior. Besides, magnetic transition has great influence on the charge carriers in this system and negative colossal magnetoresistance is observed for all P-doped samples. Our findings suggest that EuIn2(As1-xPx)2 is a promising material playground for exploring novel topological states.
    Designing high k dielectric films with LiPON—Al2O3 hybrid structure by atomic layer deposition
    Ze Feng(冯泽), Yitong Wang(王一同), Jilong Hao(郝继龙), Meiyi Jing(井美艺), Feng Lu(卢峰), Weihua Wang(王维华), Yahui Cheng(程雅慧), Shengkai Wang(王盛凯), Hui Liu(刘晖), and Hong Dong(董红)
    Chin. Phys. B, 2022, 31 (5):  057701.  DOI: 10.1088/1674-1056/ac3736
    Abstract ( 297 )   HTML ( 0 )   PDF (1359KB) ( 55 )  
    A large amount of ultra-low-power consumption electronic devices are urgently needed in the new era of the internet of things, which demand relatively low frequency response. Here, atomic layer deposition has been utilized to fabricate the ion polarization dielectric of the LiPON-Al2O3 hybrid structure. The LiPON thin film is periodically stacked in the Al2O3 matrix. This hybrid structure presents a frequency-dependent dielectric constant, of which k is significantly higher than the aluminum oxide matrix from 1 kHz to 200 kHz in frequency. The increased dielectric constant is attributed to the lithium ions shifting locally upon the applied electrical field, which shows an additional polarization to the Al2O3 matrix. This work provides a new strategy with promising potential to engineers for the dielectric constant of the gate oxide and sheds light on the application of electrolyte/dielectric hybrid structure in a variety of devices from capacitors to transistors.
    Hybrid-anode structure designed for a high-performance quasi-vertical GaN Schottky barrier diode
    Qiliang Wang(王启亮), Tingting Wang(王婷婷), Taofei Pu(蒲涛飞), Shaoheng Cheng(成绍恒),Xiaobo Li(李小波), Liuan Li(李柳暗), and Jinping Ao(敖金平)
    Chin. Phys. B, 2022, 31 (5):  057702.  DOI: 10.1088/1674-1056/ac272a
    Abstract ( 313 )   HTML ( 0 )   PDF (1087KB) ( 46 )  
    A quasi-vertical GaN Schottky barrier diode with a hybrid anode structure is proposed to trade off the on-resistance and the breakdown voltage. By inserting a SiN dielectric between the anode metal with a relatively small length, it suppresses the electric field crowding effect without presenting an obvious effect on the forward characteristics. The enhanced breakdown voltage is ascribed to the charge-coupling effect between the insulation dielectric layer and GaN. On the other hand, the current density is decreased beneath the dielectric layer with the increasing length of the SiN, resulting in a high on-resistance. Furthermore, the introduction of the field plate on the side wall forms an metal-oxide-semiconductor (MOS) channel and decreases the series resistance, but also shows an obvious electric field crowding effect at the bottom of the mesa due to the quasi-vertical structure.
    Effect of different catalysts and growth temperature on the photoluminescence properties of zinc silicate nanostructures grown via vapor-liquid-solid method
    Ghfoor Muhammad, Imran Murtaza, Rehan Abid, and Naeem Ahmad
    Chin. Phys. B, 2022, 31 (5):  057801.  DOI: 10.1088/1674-1056/ac439e
    Abstract ( 261 )   HTML ( 0 )   PDF (2208KB) ( 43 )  
    We explore the photoluminescence properties of zinc silicate (Zn2SiO4) nanostructures synthesized by vapor-liquid-solid (VLS) mode of growth using three different catalysts (Sn, Ag, and Mn). Different catalysts significantly influence the growth rate which in turn has an impact on the structure and hence the photoluminescence of the prepared zinc silicate nanostructures. Zn2SiO4 has a wide bandgap of about 5.5 eV and in its pure form, it does not emit in visible region due to its inner shell electronic transitions between the 3d5 energy levels. However, the incorporation of different catalysts (Sn, Ag and Mn) at different growth temperatures into the Zn2SiO4 crystal growth kinetics provides wide visible spectral range of photoluminescence (PL) emissions. PL analysis shows broad multi-band spectrum in the visible region and distinct colors (red, yellow, green, blue, cyan and violet) are obtained depending on the crystalline structure of the prepared nanostructures. The allowed transitions due to the effect of different catalysts on zinc silicate lattice offer a huge cross-section of absorption that generates strong photoluminescence. The correlation between the structural and optical properties of the synthesized nanostructures is discussed in detail. The synthesized photoluminescent nanostructures have potential applications in solid-state lighting and display devices.
    Strong near-field couplings of anapole modes and formation of higher-order electromagnetic modes in stacked all-dielectric nanodisks
    Bin Liu(刘彬), Ma-Long Hu(胡马龙), Yi-Wen Zhang(章艺文), Yue You(游悦), Zhao-Guo Liang(梁钊国), Xiao-Niu Peng(彭小牛), and Zhong-Jian Yang(杨中见)
    Chin. Phys. B, 2022, 31 (5):  057802.  DOI: 10.1088/1674-1056/ac3bac
    Abstract ( 289 )   HTML ( 0 )   PDF (1578KB) ( 87 )  
    We theoretically study the near-field couplings of two stacked all-dielectric nanodisks, where each disk has an electric anapole mode consisting of an electric dipole mode and an electric toroidal dipole (ETD) mode. Strong bonding and anti-bonding hybridizations of the ETD modes of the two disks occur. The bonding hybridized ETD can interfere with the dimer's electric dipole mode and induce a new electric anapole mode. The anti-bonding hybridization of the ETD modes can induce a magnetic toroidal dipole (MTD) response in the disk dimer. The MTD and magnetic dipole resonances of the dimer form a magnetic anapole mode. Thus, two dips associated with the hybridized modes appear on the scattering spectrum of the dimer. Furthermore, the MTD mode is also accompanied by an electric toroidal quadrupole mode. The hybridizations of the ETD and the induced higher-order modes can be adjusted by varying the geometries of the disks. The strong anapole mode couplings and the corresponding rich higher-order mode responses in simple all-dielectric nanostructures can provide new opportunities for nanoscale optical manipulations.
    Exciton luminescence and many-body effect of monolayer WS2 at room temperature
    Jian-Min Wu(吴建民), Li-Hui Li(黎立辉), Wei-Hao Zheng(郑玮豪), Bi-Yuan Zheng(郑弼元), Zhe-Yuan Xu(徐哲元), Xue-Hong Zhang(张学红), Chen-Guang Zhu(朱晨光), Kun Wu(吴琨), Chi Zhang(张弛), Ying Jiang(蒋英),Xiao-Li Zhu(朱小莉), and Xiu-Juan Zhuang(庄秀娟)
    Chin. Phys. B, 2022, 31 (5):  057803.  DOI: 10.1088/1674-1056/ac380c
    Abstract ( 324 )   HTML ( 2 )   PDF (2197KB) ( 48 )  
    Monolayer transition metal dichalcogenides favor the formation of a variety of excitonic quasiparticles, and can serve as an ideal material for exploring room-temperature many-body effects in two-dimensional systems. Here, using mechanically exfoliated monolayer WS2 and photoluminescence (PL) spectroscopy, exciton emission peaks are confirmed through temperature-dependent and electric-field-tuned PL spectroscopy. The dependence of exciton concentration on the excitation power density at room temperature is quantitatively analyzed. Exciton concentrations covering four orders of magnitude are divided into three stages. Within the low carrier concentration stage, the system is dominated by excitons, with a small fraction of trions and localized excitons. At the high carrier concentration stage, the localized exciton emission from defects coincides with the emission peak position of trions, resulting in broad spectral characteristics at room temperature.
    First principles investigation on Li or Sn codoped hexagonal tungsten bronzes as the near-infrared shielding material
    Bo-Shen Zhou(周博深), Hao-Ran Gao(高浩然), Yu-Chen Liu(刘雨辰), Zi-Mu Li(李子木),Yang-Yang Huang(黄阳阳), Fu-Chun Liu(刘福春), and Xiao-Chun Wang(王晓春)
    Chin. Phys. B, 2022, 31 (5):  057804.  DOI: 10.1088/1674-1056/ac598a
    Abstract ( 355 )   HTML ( 3 )   PDF (1551KB) ( 126 )  
    The 52% energy of the solar radiation is contributed by near-infrared radiation (NIR, 780-2500 nm). Therefore, the material design for the energy-saving smart window, which can effectively shield NIR and has acceptable visible transmittance, is vital to save the energy consumed on the temperature control system. It is important to find a non-toxic stable material with excellent NIR-shielding ability and acceptable visible transmittance. The systematic first-principles study on LixSnyWO3 (x=0, 0.33, 0.66, and y=0, 0.33) exhibits that the chemical stability is a positive correlation with the doping concentration. After doping, the Fermi-energy upshifts into the conduction band, and the material shows metal-like characteristics. Therefore, these structures LixSnyWO3 (except the structure with x=0.33 and y=0) show pronounced improvement of NIR shielding ability. Our results indicate that when x=0 and y=0.33, the material exhibits the strongest NIR-shielding ability, satisfying chemical stability, wide NIR-shielding range (780-2500 nm), and acceptable visible transmittance. This work provides a good choice for experimental study on NIR shielding material for the energy-saving window.
    Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials
    Fengling Chen(陈峰岭), Jiannan Lin(林建楠), Yifan Chen(陈一帆), Binbin Dong(董彬彬), Chujun Yin(尹楚君), Siying Tian(田飔莹), Dapeng Sun(孙大鹏), Jing Xie (解婧),Zhenyu Zhang(张振宇), Hong Li(李泓), and Chaobo Li(李超波)
    Chin. Phys. B, 2022, 31 (5):  058101.  DOI: 10.1088/1674-1056/ac4481
    Abstract ( 393 )   HTML ( 1 )   PDF (4168KB) ( 231 )  
    Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density. However, low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application. Herein, a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi0.88Mn0.03Co0.09O2, and the electrochemical performance is improved. The modified LiNi0.88Mn0.03Co0.09O2 displays an initial discharge capacity of ~ 233 mAh/g at 0.1 C and 174 mAh/g at 1 C after 150 cycles in the voltage range of 3.0 V-4.4 V at 45℃, and it also exhibits an enhanced rate capability with 118 mAh/g at 5 C. The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi0.88Mn0.03Co0.09O2, and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.
    SPECIAL TOPIC—Superconductivity in vanadium-based kagome materials
    Robustness of the unidirectional stripe order in the kagome superconductor CsV3Sb5
    Bin Hu(胡彬), Yuhan Ye(耶郁晗), Zihao Huang(黄子豪), Xianghe Han(韩相和), Zhen Zhao(赵振),Haitao Yang(杨海涛), Hui Chen(陈辉), and Hong-Jun Gao(高鸿钧)
    Chin. Phys. B, 2022, 31 (5):  058102.  DOI: 10.1088/1674-1056/ac5888
    Abstract ( 447 )   HTML ( 3 )   PDF (2401KB) ( 241 )  
    V-based kagome materials AV3Sb5 (A=K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a0×2a0 CDW (charge density wave with in-plane 2×2 superlattice modulation) in AV3Sb5, an additional 1×4 (4a0) unidirectional stripe order has been observed at the Sb surface of RbV3Sb5 and CsV3Sb5. However, the stability and electronic nature of the 4a0 stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a0 stripe order on the Sb-terminated surface of CsV3Sb5. We find that the 4a0 stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a0 stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV3Sb5.
    Photoelectrochemical activity of ZnO:Ag/rGO photo-anodes synthesized by two-steps sol-gel method
    D Ben Jemia, M Karyaoui, M A Wederni, A Bardaoui, M V Martinez-Huerta, M Amlouk, and R Chtourou
    Chin. Phys. B, 2022, 31 (5):  058201.  DOI: 10.1088/1674-1056/ac474a
    Abstract ( 309 )   HTML ( 1 )   PDF (5206KB) ( 86 )  
    This work investigated the influence of silver plasmon and reduced graphene oxide (rGO) on the photoelectrochemical performance (PEC) of ZnO thin films synthesized by the sol-gel method. The physicochemical properties of the obtained photo-anodes were systematically studied by using several characterization techniques. The x-ray diffraction analysis showed that all samples presented hexagonal wurtzite structure with a polycrystalline nature. Raman and energy dispersive x-ray (EDX) studies confirmed the existence of both Ag and rGO in ZnO:Ag/rGO thin films. The estimated grain size obtained from scanning electron microscopy (SEM) analysis decreased with Ag doping, then increased to a maximum value after rGO addition. The UV-vis transmission spectra of the as-prepared ZnO:Ag and ZnO:Ag/rGO thin films have shown a reduction in the visible range with a redshift at the absorption edges. The bandgaps were estimated to be around 3.17 eV, 2.7 eV, and 2.52 eV for ZnO, ZnO:Ag, and ZnO:Ag/rGO, respectively. Moreover, the electrical measurements revealed that the charge exchange processes were enhanced at the ZnO:Ag/rGO/electrolyte interface, accompanied by an increase in the (PEC) performance compared to ZnO and ZnO:Ag photo-anodes. Consequently, the photocurrent density of ZnO:Ag/rGO (0.2 mA·cm-2) was around 4 and 2.22 times higher than photo-anodes based on undoped ZnO (0.05 mA·cm-2) and ZnO:Ag (0.09 mA·cm-2), respectively. Finally, from the flat band potential and donor density, deduced from the Mott-Schottky, it was clear that all the samples were n-type semiconductors with the highest carrier density for the ZnO:Ag/rGO photo-anode.
    Simulated and experimental studies of a multi-band symmetric metamaterial absorber with polarization independence for radar applications
    Hema O. Ali, Asaad M. Al-Hindawi, Yadgar I. Abdulkarim, Ekasit Nugoolcharoenlap, Tossapol Tippo,Fatih Özkan Alkurt, Olcay Altıntaş, and Muharrem Karaaslan
    Chin. Phys. B, 2022, 31 (5):  058401.  DOI: 10.1088/1674-1056/ac2b1c
    Abstract ( 328 )   HTML ( 3 )   PDF (4507KB) ( 187 )  
    We develop a simple new design for a multi-band metamaterial absorber (MTMA) for radar applications. Computer Simulation Technology (CST) Studio Suite 2018 was used for the numerical analysis and absorption study. The simulated results show four high peaks at 5.6 GHz, 7.6 GHz, 10.98 GHz, and 11.29 GHz corresponding to absorption characteristics of 100%, 100%, 99%, and 99%, respectively. Furthermore, two different structures were designed and compared with the proposed MTMA. The proposed structure remained insensitive for any incident angle and polarization angle from 0° to 60°. Moreover, negative constitutive parameters were retrieved numerically. To support the simulated results, the proposed design was fabricated by using a computer numerical control-based printed circuit board prototyping machine and tested experimentally in a microwave laboratory. The absorption mechanism of the proposed MTMA is presented through the surface current and electric field distributions. The novelties of the proposed structure are a simple and new design, ease of fabrication, low cost, durability, suitability for real-time applications and long-term stability given the fabrication technique and non-destructive measurement method and very high absorption. The proposed structure has potential applications in C and X band frequency ranges.
    DC and analog/RF performance of C-shaped pocket TFET (CSP-TFET) with fully overlapping gate
    Zi-Xin Chen(陈子馨), Wei-Jing Liu(刘伟景), Jiang-Nan Liu(刘江南), Qiu-Hui Wang(王秋蕙), Xu-Guo Zhang(章徐国), Jie Xu(许洁), Qing-Hua Li(李清华), Wei Bai(白伟), and Xiao-Dong Tang(唐晓东)
    Chin. Phys. B, 2022, 31 (5):  058501.  DOI: 10.1088/1674-1056/ac43a6
    Abstract ( 372 )   HTML ( 0 )   PDF (1559KB) ( 125 )  
    A C-shaped pocket tunnel field effect transistor (CSP-TFET) has been designed and optimized based on the traditional double-gate TFETs by introducing a C-shaped pocket region between the source and channel to improve the device performance. A gate-to-pocket overlapping structure is also examined in the proposed CSP-TFET to enhance the gate controllability. The effects of the pocket length, pocket doping concentration and gate-to-pocket overlapping structure on the DC and analog/RF characteristics of the CSP-TFET are estimated after calibrating the tunneling model in double-gate TFETs. The DC and analog/RF performance such as on-state current (Ion), on/off current ratio (Ion/Ioff), subthreshold swing (SS) transconductance (gm), cut-off frequency (fT) and gain-bandwidth product (GBP) are investigated. The optimized CSPTFET device exhibits excellent performance with high Ion (9.98×10 - 4 A/μm), high Ion/Ioff (~ 1011), as well as low SS (~ 12 mV/dec). The results reveal that the CSP-TFET device could be a potential alternative for the next generation of semiconductor devices.
    Impact of gate offset in gate recess on DC and RF performance of InAlAs/InGaAs InP-based HEMTs
    Shurui Cao(曹书睿), Ruize Feng(封瑞泽), Bo Wang(王博), Tong Liu(刘桐), Peng Ding(丁芃), and Zhi Jin(金智)
    Chin. Phys. B, 2022, 31 (5):  058502.  DOI: 10.1088/1674-1056/ac464f
    Abstract ( 344 )   HTML ( 2 )   PDF (1749KB) ( 122 )  
    A set of 100-nm gate-length InP-based high electron mobility transistors (HEMTs) were designed and fabricated with different gate offsets in gate recess. A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography. DC and RF measurement was conducted. With the gate offset varying from drain side to source side, the maximum drain current (Ids,max) and transconductance (gm,max) increased. In the meantime, fT decreased while fmax increased, and the highest fmax of 1096 GHz was obtained. It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance. Output conductance was also suppressed by gate offset toward source side. This provides simple and flexible device parameter selection for HEMTs of different usages.
    MOS-based model of four-transistor CMOS image sensor pixels for photoelectric simulation
    Bing Zhang(张冰), Congzhen Hu(胡从振), Youze Xin(辛有泽), Yaoxin Li(李垚鑫), Zhuoqi Guo(郭卓奇), Zhongming Xue(薛仲明), Li Dong(董力), Shanzhe Yu(于善哲), Xiaofei Wang(王晓飞), Shuyu Lei(雷述宇), and Li Geng(耿莉)
    Chin. Phys. B, 2022, 31 (5):  058503.  DOI: 10.1088/1674-1056/ac3819
    Abstract ( 337 )   HTML ( 0 )   PDF (1356KB) ( 164 )  
    By using the MOS-based model established in this paper, the physical process of photoelectron generation, transfer, and storage in the four-transistor active pixel sensor (4T-APS) pixels can be simulated in SPICE environment. The variable capacitance characteristics of double junctions in pinned photodiodes (PPDs) and the threshold voltage difference formed by channel nonuniform doping in transfer gates (TGs) are considered with this model. The charge transfer process of photogenerated electrons from PPDs to the floating diffusion (FD) is analyzed, and the function of nonuniform doping of TGs in suppressing charge injection back to PPDs is represented with the model. The optical and electrical characteristics of all devices in the pixel are effectively combined with the model. Moreover, the charge transfer efficiency and the voltage variation in PPD can be described with the model. Compared with the hybrid simulation in TCAD and the Verilog-A simulation in SPICE, this model has higher simulation efficiency and accuracy, respectively. The effectiveness of the MOS-based model is experimentally verified in a 3 μ m test pixel designed in 0.11 μm CIS process.
    Thermionic electron emission in the 1D edge-to-edge limit
    Tongyao Zhang(张桐耀), Hanwen Wang(王汉文), Xiuxin Xia(夏秀鑫), Chengbing Qin(秦成兵), and Xiaoxi Li(李小茜)
    Chin. Phys. B, 2022, 31 (5):  058504.  DOI: 10.1088/1674-1056/ac464d
    Abstract ( 338 )   HTML ( 0 )   PDF (3547KB) ( 85 )  
    Thermionic emission is a tunneling phenomenon, which depicts that electrons on the surface of a conductor can be pulled out into the vacuum when they are subjected to high electrical tensions while being heated hot enough to overtake their work functions. This principle has led to the great success of the so-called vacuum tubes in the early 20th century. To date, major challenges still remain in the miniaturization of a vacuum channel transistor for on-chip integration in modern solid-state integrated circuits. Here, by introducing nano-sized vacuum gaps (~ 200 nm) in a van der Waals heterostructure, we successfully fabricated a one-dimensional (1D) edge-to-edge thermionic emission vacuum tube using graphene as the filament. With the increasing collector voltage, the emitted current exhibits a typical rectifying behavior, with the maximum emission current reaching 200 pA and an ON-OFF ratio of 103. In addition, it is found that the maximum emission current is proportional to the number of the layers of graphene. Our results expand the research of nano-sized vacuum tubes to an unexplored physical limit of 1D edge-to-edge emission, and hold great promise for future nano-electronic systems based on it.
    Current oscillation in GaN-HEMTs with p-GaN islands buried layer for terahertz applications
    Wen-Lu Yang(杨文璐), Lin-An Yang(杨林安), Fei-Xiang Shen(申飞翔), Hao Zou(邹浩), Yang Li(李杨), Xiao-Hua Ma(马晓华), and Yue Hao(郝跃)
    Chin. Phys. B, 2022, 31 (5):  058505.  DOI: 10.1088/1674-1056/ac2b1f
    Abstract ( 369 )   HTML ( 3 )   PDF (1059KB) ( 129 )  
    A GaN-based high electron mobility transistor (HEMT) with p-GaN islands buried layer (PIBL) for terahertz applications is proposed. The introduction of a p-GaN island redistributes the electric field in the gate-drain channel region, thereby promoting the formation of electronic domains in the two-dimensional electron gas (2DEG) channel. The formation and regulation mechanism of the electronic domains in the device are investigated using Silvaco-TCAD software. Simulation results show that the 0.2 μ m gate HEMT with a PIBL structure having a p-GaN island doping concentration (Np) of 2.5×1018 cm-3-3×1018 cm-3 can generate stable oscillations up to 344 GHz-400 GHz under the gate-source voltage (Vgs) of 0.6 V. As the distance (Dp) between the p-GaN island and the heterojunction interface increases from 5 nm to 15 nm, the fundamental frequency decreases from 377 GHz to 344 GHz, as well as the ratio of oscillation current amplitude of the fundamental component to the average component If1/Iavg ranging from 2.4% to 3.84%.
    Enhancement of fMAX of InP-based HEMTs by double-recessed offset gate process
    Bo Wang(王博), Peng Ding(丁芃), Rui-Ze Feng(封瑞泽), Shu-Rui Cao(曹书睿), Hao-Miao Wei(魏浩淼), Tong Liu(刘桐), Xiao-Yu Liu(刘晓宇), Hai-Ou Li(李海鸥), and Zhi Jin(金智)
    Chin. Phys. B, 2022, 31 (5):  058506.  DOI: 10.1088/1674-1056/ac6013
    Abstract ( 341 )   HTML ( 1 )   PDF (1783KB) ( 61 )  
    A double-recessed offset gate process technology for InP-based high electron mobility transistors (HEMTs) has been developed in this paper. Single-recessed and double-recessed HEMTs with different gate offsets have been fabricated and characterized. Compared with single-recessed devices, the maximum drain-source current (ID,max) and maximum extrinsic transconductance (gm,max) of double-recessed devices decreased due to the increase in series resistances. However, in terms of RF performance, double-recessed HEMTs achieved higher maximum oscillation frequency (fMAX) by reducing drain output conductance (gds) and drain to gate capacitance (Cgd). In addition, further improvement of fMAX was observed by adjusting the gate offset of double-recessed devices. This can be explained by suppressing the ratio of Cgd to source to gate capacitance (Cgs) by extending drain-side recess length (Lrd). Compared with the single-recessed HEMTs, the fMAX of double-recessed offset gate HEMTs was increased by about 20%.
    Analysis of period and visibility of dual phase grating interferometer
    Jun Yang(杨君), Jian-Heng Huang(黄建衡), Yao-Hu Lei(雷耀虎), Jing-Biao Zheng(郑景标), Yu-Zheng Shan(单雨征), Da-Yu Guo(郭大育), and Jin-Chuan Guo(郭金川)
    Chin. Phys. B, 2022, 31 (5):  058701.  DOI: 10.1088/1674-1056/ac3a60
    Abstract ( 284 )   HTML ( 0 )   PDF (1707KB) ( 38 )  
    Dual phase grating interferometer may simultaneously achieve large field of view and high x-ray dose efficiency. Here, we develop a simple theoretical method to better understand the imaging process of the dual phase grating interferometer. The derivation process of fringe period and the optimal visibility conditions of the dual phase grating interferometer are given in detail. Then, we theoretically prove that the fringe period and optimal visibility conditions of the dual phase grating interferometer include that of the Talbot interferometer. By comparing our experimental results with those of other researchers, we find that when the positions of phase gratings are far away from the positions where the fringe visibility is optimal, the fringe period of the dual π -phase grating interferometer is twice the theoretical results under the illumination of polychromatic x-ray. This conclusion may explain the contradictory research results of dual phase grating interferometer among different researchers.
    Investigation of the structural and dynamic basis of kinesin dissociation from microtubule by atomistic molecular dynamics simulations
    Jian-Gang Wang(王建港), Xiao-Xuan Shi(史晓璇), Yu-Ru Liu(刘玉如), Peng-Ye Wang(王鹏业),Hong Chen(陈洪), and Ping Xie(谢平)
    Chin. Phys. B, 2022, 31 (5):  058702.  DOI: 10.1088/1674-1056/ac598b
    Abstract ( 309 )   HTML ( 0 )   PDF (3920KB) ( 88 )  
    Kinesin is a molecular motor that can step processively on microtubules via the hydrolysis of ATP molecules. An important factor characterizing the processivity of the kinesin motor is its dissociation from the microtubule. Here, using all-atom molecular dynamics simulations, we studied the dissociation process of the kinesin head in weak-microtubule-binding or ADP state from tubulin on the basis of the available high-resolution structural data for the head and tubulin. By analyzing the simulated snapshots of the structure of the head-tubulin complex we provided detailed structural and dynamic information for the dissociation process. We found that the dissociation of the head along different directions relative to the tubulin exhibits very different dynamic behaviors. Moreover, the potential forms or energy landscapes of the interaction between the head and tubulin along different directions were determined. The studies have important implications for the detailed molecular mechanism of the dissociation of the kinesin motor and thus are critical to the mechanism of its processivity.
    GeSn (0.524 eV) single-junction thermophotovoltaic cells based on the device transport model
    Xin-Miao Zhu(朱鑫淼), Min Cui(崔敏), Yu Wang(汪宇), Tian-Jing Yu(于添景),Jin-Xiang Deng(邓金祥), and Hong-Li Gao(高红丽)
    Chin. Phys. B, 2022, 31 (5):  058801.  DOI: 10.1088/1674-1056/ac4749
    Abstract ( 361 )   HTML ( 0 )   PDF (2100KB) ( 74 )  
    Based on the transport equation of the semiconductor device model for 0.524 eV GeSn alloy and the experimental parameters of the material, the thermal-electricity conversion performance governed by a GeSn diode has been systematically studied in its normal and inverted structures. For the normal p+/n (n+/p) structure, it is demonstrated here that an optimal base doping Nd(a) = 3 (7)×1018 cm-3 is observed, and the superior p+/n structure can achieve a higher performance. To reduce material consumption, an economical active layer can comprise a 100 nm-300 nm emitter and a 3 μm-6 μm base to attain comparable performance to that for the optimal configuration. Our results offer many useful guidelines for the fabrication of economical GeSn thermophotovoltaic devices.
    A novel car-following model by sharing cooperative information transmission delayed effect under V2X environment and its additional energy consumption
    Guang-Han Peng(彭光含), Te-Ti Jia(贾特提), Hua Kuang(邝华), Hui-Li Tan(谭惠丽), and Tao Chen(陈陶)
    Chin. Phys. B, 2022, 31 (5):  058901.  DOI: 10.1088/1674-1056/ac422a
    Abstract ( 343 )   HTML ( 3 )   PDF (1776KB) ( 105 )  
    A novel car-following model is offered based on the cooperative information transmission delayed effect involving headway and velocity under V2X environment. The stability conditions and mKdV equation of the new model are obtained via the linear and nonlinear analysis. Through numerical simulation, the variation trend of headway and hysteresis phenomenon are studied. In addition, we investigate the additional energy consumption of the vehicle during acceleration. In brief, theoretical analysis and simulation results confirm that the new car-following model based on the cooperative information transmission delayed effect can improve traffic stability and reduce additional energy consumption.
    Voter model on adaptive networks
    Jinming Du(杜金铭)
    Chin. Phys. B, 2022, 31 (5):  058902.  DOI: 10.1088/1674-1056/ac43b4
    Abstract ( 389 )   HTML ( 3 )   PDF (1675KB) ( 148 )  
    Voter model is an important basic model in statistical physics. In recent years, it has been more and more used to describe the process of opinion formation in sociophysics. In real complex systems, the interactive network of individuals is dynamically adjusted, and the evolving network topology and individual behaviors affect each other. Therefore, we propose a linking dynamics to describe the coevolution of network topology and individual behaviors in this paper, and study the voter model on the adaptive network. We theoretically analyze the properties of the voter model, including consensus probability and time. The evolution of opinions on dynamic networks is further analyzed from the perspective of evolutionary game. Finally, a case study of real data is shown to verify the effectiveness of the theory.
    A novel method for identifying influential nodes in complex networks based on gravity model
    Yuan Jiang(蒋沅), Song-Qing Yang(杨松青), Yu-Wei Yan(严玉为),Tian-Chi Tong(童天驰), and Ji-Yang Dai(代冀阳)
    Chin. Phys. B, 2022, 31 (5):  058903.  DOI: 10.1088/1674-1056/ac4226
    Abstract ( 370 )   HTML ( 8 )   PDF (1392KB) ( 131 )  
    How to identify influential nodes in complex networks is an essential issue in the study of network characteristics. A number of methods have been proposed to address this problem, but most of them focus on only one aspect. Based on the gravity model, a novel method is proposed for identifying influential nodes in terms of the local topology and the global location. This method comprehensively examines the structural hole characteristics and K-shell centrality of nodes, replaces the shortest distance with a probabilistically motivated effective distance, and fully considers the influence of nodes and their neighbors from the aspect of gravity. On eight real-world networks from different fields, the monotonicity index, susceptible-infected-recovered (SIR) model, and Kendall's tau coefficient are used as evaluation criteria to evaluate the performance of the proposed method compared with several existing methods. The experimental results show that the proposed method is more efficient and accurate in identifying the influence of nodes and can significantly discriminate the influence of different nodes.
    Erratum to “ Accurate GW0 band gaps and their phonon-induced renormalization in solids”
    Tong Shen(申彤), Xiao-Wei Zhang(张小伟), Min-Ye Zhang(张旻烨), Hong Jiang(蒋鸿), and Xin-Zheng Li(李新征)
    Chin. Phys. B, 2022, 31 (5):  059901.  DOI: 10.1088/1674-1056/ac6578
    Abstract ( 442 )   HTML ( 0 )   PDF (800KB) ( 25 )  
    The derivation of Eq. (28) in the original paper [Chin. Phys. B 30 117101 (2021)] is corrected.
    Erratum to “Boundary layer flow and heat transfer of a Casson fluid past a symmetric porous wedge with surface heat flux”
    Swati Mukhopadhyay and Iswar Chandra Mandal
    Chin. Phys. B, 2022, 31 (5):  059902.  DOI: 10.1088/1674-1056/ac67c8
    Abstract ( 257 )   HTML ( 0 )   PDF (721KB) ( 29 )  
    We would like to acknowledge the misprinted terms in our published paper “Boundary layer flow and heat transfer of a Casson fluid past a symmetric porous wedge with surface heat flux” [Chin. Phys. B 23 044702 (2014)]. Since only two misprints exist and the main results of the published paper are correct, we present the correct equations in this erratum.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 31, No. 5

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