Table of contents

    16 July 2021, Volume 30 Issue 8 Previous issue    Next issue
    Dynamics of a stochastic rumor propagation model incorporating media coverage and driven by Lévy noise
    Liang-An Huo(霍良安), Ya-Fang Dong(董雅芳), and Ting-Ting Lin(林婷婷)
    Chin. Phys. B, 2021, 30 (8):  080201.  DOI: 10.1088/1674-1056/ac0423
    Abstract ( 436 )   HTML ( 1 )   PDF (1265KB) ( 98 )  
    With the development of information technology, rumors propagate faster and more widely than in the past. In this paper, a stochastic rumor propagation model incorporating media coverage and driven by Lévy noise is proposed. The global positivity of the solution process is proved, and further the basic reproductive number R0 is obtained. When R0 < 1, the dynamical process of system with Lévy jump tends to the rumor-free equilibrium point of the deterministic system, and the rumor tends to extinction; when R0 > 1, the rumor will keep spreading and the system will oscillate randomly near the rumor equilibrium point of the deterministic system. The results show that the oscillation amplitude is related to the disturbance of the system. In addition, increasing media coverage can effectively reduce the final spread of rumors. Finally, the above results are verified by numerical simulation.
    Real-space parallel density matrix renormalization group with adaptive boundaries
    Fu-Zhou Chen(陈富州), Chen Cheng(程晨), and Hong-Gang Luo(罗洪刚)
    Chin. Phys. B, 2021, 30 (8):  080202.  DOI: 10.1088/1674-1056/abeb08
    Abstract ( 528 )   HTML ( 1 )   PDF (782KB) ( 190 )  
    We propose an improved real-space parallel strategy for the density matrix renormalization group (DMRG) method, where boundaries of separate regions are adaptively distributed during DMRG sweeps. Our scheme greatly improves the parallel efficiency with shorter waiting time between two adjacent tasks, compared with the original real-space parallel DMRG with fixed boundaries. We implement our new strategy based on the message passing interface (MPI), and dynamically control the number of kept states according to the truncation error in each DMRG step. We study the performance of the new parallel strategy by calculating the ground state of a spin-cluster chain and a quantum chemical Hamiltonian of the water molecule. The maximum parallel efficiencies for these two models are 91% and 76% in 4 nodes, which are much higher than the real-space parallel DMRG with fixed boundaries.
    Consistent Riccati expansion solvability, symmetries, and analytic solutions of a forced variable-coefficient extended Korteveg-de Vries equation in fluid dynamics of internal solitary waves
    Ping Liu(刘萍), Bing Huang(黄兵), Bo Ren(任博), and Jian-Rong Yang(杨建荣)
    Chin. Phys. B, 2021, 30 (8):  080203.  DOI: 10.1088/1674-1056/ac052a
    Abstract ( 477 )   HTML ( 1 )   PDF (1723KB) ( 117 )  
    We study a forced variable-coefficient extended Korteweg-de Vries (KdV) equation in fluid dynamics with respect to internal solitary wave. Bäcklund transformations of the forced variable-coefficient extended KdV equation are demonstrated with the help of truncated Painlevé expansion. When the variable coefficients are time-periodic, the wave function evolves periodically over time. Symmetry calculation shows that the forced variable-coefficient extended KdV equation is invariant under the Galilean transformations and the scaling transformations. One-parameter group transformations and one-parameter subgroup invariant solutions are presented. Cnoidal wave solutions and solitary wave solutions of the forced variable-coefficient extended KdV equation are obtained by means of function expansion method. The consistent Riccati expansion (CRE) solvability of the forced variable-coefficient extended KdV equation is proved by means of CRE. Interaction phenomenon between cnoidal waves and solitary waves can be observed. Besides, the interaction waveform changes with the parameters. When the variable parameters are functions of time, the interaction waveform will be not regular and smooth.
    Effect of the potential function and strain rate on mechanical behavior of the single crystal Ni-based alloys: A molecular dynamics study
    Qian Yin(尹倩), Ye-Da Lian(连业达), Rong-Hai Wu(巫荣海), Li-Qiang Gao(高利强), Shu-Qun Chen(陈树群), and Zhi-Xun Wen(温志勋)
    Chin. Phys. B, 2021, 30 (8):  080204.  DOI: 10.1088/1674-1056/abff22
    Abstract ( 412 )   HTML ( 3 )   PDF (1997KB) ( 131 )  
    Molecular dynamics has been widely used to study the fundamental mechanism of Ni-based superalloys. However, the effect of the potential function and strain rate on mechanical behavior has rarely been mentioned in the previous molecular dynamics studies. In the present work, we show that the potential function of molecular dynamics can dramatically influence the simulation results of single crystal Ni-based superalloys. The microstructure and mechanical behavior of single crystal Ni-based superalloys under four commonly used potential functions are systematically compared. A most suitable potential function for the mechanical deformation is critically selected, and based on it, the role of strain rate on the mechanical deformation is investigated.
    Atomistic simulations of the lubricative mechanism of a nano-alkane lubricating film between two layers of Cu-Zn alloy
    Jing Li(李京), Peng Zhu(朱鹏), Yuan-Yuan Sheng(盛圆圆), Lin Liu(刘麟), and Yong Luo(罗勇)
    Chin. Phys. B, 2021, 30 (8):  080205.  DOI: 10.1088/1674-1056/abfbd6
    Abstract ( 415 )   HTML ( 4 )   PDF (1968KB) ( 84 )  
    We describe simulations of lubrication by a hexadecane molecular lubricating film during the shearing process of a Cu-Zn alloy performed using the atomistic method. The results indicate that with increasing Zn contents, the interface slip between the alloy wall and the lubricating film first decreases and then increases, according to variations of the radius distribution function (RDF), while the interface slip reaches its lowest value of 0.12 during the shearing of CuZn30 alloy. We also discuss the relationship between interface roughness and the lubricating film. During film lubrication, the interface's roughness effectively inhibits interfacial slip. For the convex contact model, the presence of the hexadecane lubricating film reduces the interfacial contact pressure from 11.9 GPa to 8.7 GPa and the friction coefficient from 0.81 to 0.52.
    Introducing the general condition for an operator in curved space to be unitary
    Jafari Matehkolaee Mehdi
    Chin. Phys. B, 2021, 30 (8):  080301.  DOI: 10.1088/1674-1056/abe300
    Abstract ( 310 )   HTML ( 1 )   PDF (659KB) ( 32 )  
    We investigate the general condition for an operator to be unitary. This condition is introduced according to the definition of the position operator in curved space. In a particular case, we discuss the concept of translation operator in curved space followed by its relation with an anti-Hermitian generator. Also we introduce a universal formula for adjoint of an arbitrary linear operator. Our procedure in this paper is totally different from others, as we explore a general approach based only on the algebra of the operators. Our approach is only discussed for the translation operators in one-dimensional space and not for general operators.
    Realization of simultaneous balanced multi-outputs for multi-protocols QKD decoding based onsilica-based planar lightwave circuit
    Jin You(游金), Yue Wang(王玥), and Jun-Ming An(安俊明)
    Chin. Phys. B, 2021, 30 (8):  080302.  DOI: 10.1088/1674-1056/abe2ff
    Abstract ( 516 )   HTML ( 1 )   PDF (2008KB) ( 106 )  
    Silica-based planar lightwave circuit (PLC) devices can reduce transmission loss and cost in a quantum key distribution (QKD) system, and have potential applications in integration and production. A PLC-based quantum decoding integrated chip for multi-protocols is designed and fabricated, which is composed of variable optical splitters (VOSs), asymmetric Mach-Zehnder interferometers (AMZIs), and variable directional couplers (VDCs). Balanced pulse-pairs of four outputs are obtained simultaneously with measured delay times of 405 ps and 402 ps, respectively. The chip has advantages in achieving high interference visibility and low quantum bit error rate (QBER).
    Effects of initial states on the quantum correlations in the generalized Grover search algorithm
    Zhen-Yu Chen(陈祯羽), Tian-Hui Qiu(邱田会), Wen-Bin Zhang(张文彬), and Hong-Yang Ma(马鸿洋)
    Chin. Phys. B, 2021, 30 (8):  080303.  DOI: 10.1088/1674-1056/ac05a9
    Abstract ( 380 )   HTML ( 1 )   PDF (926KB) ( 174 )  
    We investigate the correlations between two qubits in the Grover search algorithm with arbitrary initial states by numerical simulation. Using a set of suitable bases, we construct the reduced density matrix and give the numerical expression of correlations relating to the iterations. For different initial states, we obtain the concurrence and quantum discord compared with the success probability in the algorithm. The results show that the initial states affect the correlations and the limit point of the correlations in the searching process. However, the initial states do not influence the whole cyclical trend.
    TOPICAL REVIEW—Quantum computation and quantum simulation
    Quantum computation and simulation with superconducting qubits
    Kaiyong He(何楷泳), Xiao Geng(耿霄), Rutian Huang(黄汝田), Jianshe Liu(刘建设), and Wei Chen(陈炜)
    Chin. Phys. B, 2021, 30 (8):  080304.  DOI: 10.1088/1674-1056/ac16cf
    Abstract ( 751 )   HTML ( 11 )   PDF (3866KB) ( 430 )  
    Superconducting circuits based on Josephson junctions are regarded as one of the most promising technologies for the implementation of scalable quantum computers. This review presents the basic principles of superconducting qubits and shows the progress of quantum computing and quantum simulation based on superconducting qubits in recent years. The experimental realization of gate operations, readout, error correction codes, as well as some quantum algorithms are summarized, followed by an introduction of quantum simulation. And then some important applications in fields including condensed matter physics, quantum annealing, and quantum chemistry are discussed.
    SPECIAL TOPIC—Quantum computation and quantum simulation
    Optimized pulse for stimulated Raman adiabatic passage on noisy experimental platform
    Zhi-Ling Wang(王志凌), Leiyinan Liu(刘雷轶男), and Jian Cui(崔健)
    Chin. Phys. B, 2021, 30 (8):  080305.  DOI: 10.1088/1674-1056/abfccb
    Abstract ( 529 )   HTML ( 8 )   PDF (1633KB) ( 247 )  
    Stimulated Raman adiabatic passage (STIRAP) is an important technique to manipulate quantum states in quantum simulation and quantum computation. The transformation fidelity is limited in reality due to experimental imperfections. After systematically calculating the influence of dissipation caused by thermal fluctuations and instantaneous decay of the intermediate state, we find optimized control pulses of Rydberg atom in optical tweezer to increase the STIRAP fidelity via optimal control method. All constraints of currently available control lasers have been taken into account. The transition error can be further depressed when control lasers with shorter rise time and accordingly proper total evolution time are applied. Finally, the robustness of the control pulses with respect to random deviations between the theoretical pulse shape and the implemented ones is also enhanced by additional rounds of optimizations based on ensemble averaged fidelity.
    Nonequilibrium free energy and information flow of a double quantum-dot system with Coulomb coupling
    Zhiyuan Lin(林智远), Tong Fu(付彤), Juying Xiao(肖菊英), Shanhe Su(苏山河), Jincan Chen(陈金灿), and Yanchao Zhang(张艳超)
    Chin. Phys. B, 2021, 30 (8):  080501.  DOI: 10.1088/1674-1056/abe119
    Abstract ( 432 )   HTML ( 2 )   PDF (999KB) ( 68 )  
    We build a double quantum-dot system with Coulomb coupling and aim at studying connections among the entropy production, free energy, and information flow. By utilizing concepts in stochastic thermodynamics and graph theory analysis, Clausius and nonequilibrium free energy inequalities are built to interpret local second law of thermodynamics for subsystems. A fundamental set of cycle fluxes and affinities is identified to decompose two inequalities by using Schnakenberg's network theory. Results show that the thermodynamic irreversibility has energy-related and information-related contributions. A global cycle associated with the feedback-induced information flow would pump electrons against the bias voltage, which implements a Maxwell demon.
    A sign-function receiving scheme for sine signals enhanced by stochastic resonance
    Zhao-Rui Li(李召瑞), Bo-Hang Chen(陈博航), Hui-Xian Sun(孙慧贤), Guang-Kai Liu(刘广凯), and Shi-Lei Zhu(朱世磊)
    Chin. Phys. B, 2021, 30 (8):  080502.  DOI: 10.1088/1674-1056/abfccc
    Abstract ( 477 )   HTML ( 1 )   PDF (1068KB) ( 59 )  
    To address the problem that it is difficult to detect an intermediate frequency (IF) signal at the receiving end of a communication system under extremely low signal-to-noise ratio (SNR) conditions, we propose a stochastic resonance (SR)-enhanced sine-signal detection method based on the sign function. By analyzing the SR mechanism of the sine signal and combining it with the characteristics of a dual-sequence frequency-hopping (DSFH) receiver, a periodic stationary solution of the Fokker-Planck equation (FPE) with a time parameter is obtained. The extreme point of the sine signal is selected as the decision time, and the force law of the electromagnetic particles is analyzed. A receiving structure based on the sign function is proposed to maximize the output difference of the system, and the value condition of the sign function is determined. In order to further improve the detection performance, in combination with the central-limit theorem, the sampling points are averaged N times, and the signal-detection problem is transformed into a hypothesis-testing problem under a Gaussian distribution. The theoretical analysis and simulation experiment results confirm that when N is 100 and the SNR is greater than 20 dB, the bit-error ratio (BER) is less than 1.5×10-2 under conditions in which the signal conforms to the optimal SR parameters.
    Acoustic wireless communication based on parameter modulation and complex Lorenz chaotic systems with complex parameters and parametric attractors
    Fang-Fang Zhang(张芳芳), Rui Gao(高瑞), and Jian Liu(刘坚)
    Chin. Phys. B, 2021, 30 (8):  080503.  DOI: 10.1088/1674-1056/ac0905
    Abstract ( 433 )   HTML ( 2 )   PDF (11544KB) ( 117 )  
    As the competition for marine resources is increasingly fierce, the security of underwater acoustic communication has attracted a great deal of attention. The information and location of the communicating platform can be leaked during the traditional underwater acoustic communication technology. According to the unique advantages of chaos communication, we put forward a novel communication scheme using complex parameter modulation and the complex Lorenz system. Firstly, we design a feedback controller and parameter update laws in a complex-variable form with rigorous mathematical proofs (while many previous references on the real-variable form were only special cases in which the imaginary part was zero), which can be realized in practical engineering; then we design a new communication scheme employing parameter modulation. The main parameter spaces of the complex Lorenz system are discussed, then they are adopted in our communication scheme. We also find that there exist parametric attractors in the complex Lorenz system. We make numerical simulations in two channels for digital signals and the simulations verify our conclusions.
    Real-time frequency transfer system over ground-to-satellite link based on carrier-phase compensation at 10-16 level
    Hui-Jian Liang(梁慧剑), Shi-Guang Wang(王时光), Yu Bai(白钰), Si-Chen Sun(孙思忱), and Li-Jun Wang(王力军)
    Chin. Phys. B, 2021, 30 (8):  080601.  DOI: 10.1088/1674-1056/ac05a6
    Abstract ( 370 )   HTML ( 0 )   PDF (1905KB) ( 83 )  
    We demonstrate a novel and stable frequency transfer scheme over ground-to-satellite link based on real-time carrier-phase detection and compensation. We performed a zero-baseline measurement with the designed system, an uninterrupted frequency standard signal is recovered in the reception station without additional post-correction of delay error caused in the route, which is because the phase error of the entire route is tracked and compensated continuously in real-time. To achieve this goal, we employed two carriers in the system and the differential signal is transferred in order to eliminate the instability results from the local oscillator at the satellite transponder as well as the common-mode noise induced in the transfer route and microwave components. The stability of 3×10-16 with an integration time of 1 day was achieved and the time fluctuation during one day was measured to be about ±20 ps. Error sources and possible solutions are discussed. Our zero-baseline method shows a promising result for real-time satellite-based time and frequency transfer and deserves further research to find whether it works between long-baseline stations.
    Optical state selection process with optical pumping in a cesium atomic fountain clock
    Lei Han(韩蕾), Fang Fang(房芳), Wei-Liang Chen(陈伟亮), Kun Liu(刘昆), Ya-Ni Zuo(左娅妮), Fa-Song Zheng(郑发松), Shao-Yang Dai(戴少阳), and Tian-Chu Li(李天初)
    Chin. Phys. B, 2021, 30 (8):  080602.  DOI: 10.1088/1674-1056/ac0698
    Abstract ( 399 )   HTML ( 0 )   PDF (2157KB) ( 73 )  
    We propose and realize a new optical state selection method on a cesium atomic fountain clock by applying a two-laser 3-3' optical pumping configuration to spin polarize atoms. The atoms are prepared in |F=3, mF=0> clock state with optical pumping directly after being launched up, followed by a pushing beam to push away the atoms remaining in the |F=4> state. With a state selection efficiency exceeding 92%, this optical method can substitute the traditional microwave state selection, and helps to develop a more compact physical package. A Ramsey fringe has been achieved with this optical state selection method, and a contrast of 90% is obtained with a full width half maximum of 0.92 Hz. The short-term frequency stability of 6.8×10-14 (τ/s)-1/2 is acquired. In addition, the number of detected atoms is increased by a factor of 1.7 with the optical state selection.
    Single-channel vector magnetic information detection method based on diamond NV color center
    Qin-Qin Wang(王琴琴), Rui-Rong Wang(王瑞荣), Jin-Ping Liu(刘金萍), Shao-Zhuo Lin(林绍卓), Liang-Wei Wu(武亮伟), Hao Guo(郭浩), Zhong-Hao Li(李中豪), Huan-Fei Wen(温焕飞), Jun Tang(唐军), Zong-Min Ma(马宗敏), and Jun Liu (刘俊)
    Chin. Phys. B, 2021, 30 (8):  080701.  DOI: 10.1088/1674-1056/abea84
    Abstract ( 384 )   HTML ( 2 )   PDF (1541KB) ( 81 )  
    A method of detecting the single channel triaxial magnetic field information based on diamond nitrogen-vacancy (NV) color center is introduced. Firstly, the incident angle of the bias magnetic field which can achieve the equal frequency difference optically-detected magnetic resonance (ODMR) spectrum of diamond NV color center is calculated theoretically, and the triaxial magnetic information solution model is also constructed. Secondly, the microwave time-controlled circuit module is designed to generate equal timing and equal frequency difference microwave pulse signals in one channel. Combining with the optical detection magnetic resonance technology, the purpose of sequentially locking and detecting the four formant signals on one side of the diamond NV color center (ms=-1 state signal) is achieved, and the vector magnetic field information detection is accomplished by combining the triaxial magnetic information solution model. The system can obtain magnetic field detection in a range of 0 mT-0.82 mT. The system's magnetic noise sensitivity is 14.2 nT/Hz1/2, and the deviation angle errors of magnetic field detection θx and θy are 1.3^o and 8.2^o respectively.
    Response of HD-V2 radiochromic film to argon ions
    Lei Cheng(程蕾), Zhe Zhang(张喆), Guiyun Liang(梁贵云), and Yutong Li(李玉同)
    Chin. Phys. B, 2021, 30 (8):  080702.  DOI: 10.1088/1674-1056/ac077f
    Abstract ( 301 )   HTML ( 0 )   PDF (976KB) ( 130 )  
    A two-dimensional dose detector for ion beam is required in many high energy density physics experiments. As a solid detector, the GAFChromic film offers a good spatial resolution and dosimetric accuracy. For an absolute dose measurement, the relative effectiveness, which represents the darkening efficiency of the film to a radiation source, needs to be taken into consideration. In this contribution, the dose-response of HD-V2 to argon ions is presented for the first time. The calibration was taken over the dose range of 65 Gy-660 Gy with 8-keV argon ions. The response of net optical density is from 0.01 to 0.05. Triple-color dose-response functions are derived. The relative effectiveness for the argon ion beams is about 5%, much lower than that of protons and carbon ions. To explain this effect, the inactivation probability based on track theory of ion bombardment is proposed. Furthermore, a theoretical prediction of the relative effectiveness for single ion is presented, showing the dependence of the darkening efficiency on the atomic number and the incident energy of ions.
    Third-order nonlinear optical properties of graphene composites: A review
    Meng Shang(尚萌), Pei-Ling Li(李培玲), Yu-Hua Wang(王玉华), and Jing-Wei Luo(罗经纬)
    Chin. Phys. B, 2021, 30 (8):  080703.  DOI: 10.1088/1674-1056/ac0424
    Abstract ( 424 )   HTML ( 0 )   PDF (9424KB) ( 75 )  
    Graphene has excellent thirdorder nonlinear optical (NLO) properties due to its unique electronic band structure and wideband gap tunability. This paper focuses on the research progress of graphene and its composite materials in nonlinear optics in recent years. In this review, recent results on graphene (or graphene oxide)-metal nanoparticles (G-MNPs), graphene-metal-oxide nanoparticles (G-MONPs), graphene-metal sulfide nanoparticles (G-MSNPs), and graphene-organic molecular composites (G-OM) have been discussed. In addition, the enhancement mechanism of nonlinear absorption (NLA) and optical limiting (OL) have also been covered.
    Single boron atom anchored on graphitic carbon nitride nanosheet (B/g-C2N) as a photocatalyst for nitrogen fixation: A first-principles study
    Hao-Ran Zhu(祝浩然), Jia-Liang Chen(陈嘉亮), and Shi-Hao Wei(韦世豪)
    Chin. Phys. B, 2021, 30 (8):  083101.  DOI: 10.1088/1674-1056/abe3f6
    Abstract ( 325 )   HTML ( 2 )   PDF (2936KB) ( 33 )  
    It is essential to explore high efficient catalysts for nitrogen reduction in ammonia production. Based on the first-principles calculation, we find that B/g-C2N can serve as high performance photocatalyst in N2 fixation, where single boron atom is anchored on the g-C2N to form B/g-C2N. With the introduction of B atom to g-C2N, the energy gap reduces from 2.45 eV to 1.21 eV and shows strong absorption in the visible light region. In addition, N2 can be efficiently reduced on B/g-C2N through the enzymatic mechanism with low onset potential of 0.07 V and rate-determining barrier of 0.50 eV. The "acceptance-donation" interaction between B/g-C2N and N2 plays a key role to active N2, and the BN2 moiety of B/g-C2N acts as active and transportation center. The activity originates from the strong interaction between 1π1π* orbitals of N2 and molecular orbitals of B/g-C2N, the ionization of 1π orbital and the filling of 1π* orbital can increase the N≡N bond length greatly, making the activation of N2. Overall, this work demonstrates that B/g-C2N is a promising photocatalyst for N2 fixation.
    Calculations of dynamic multipolar polarizabilities of the Cd clock transition levels
    Mi Zhou(周密) and Li-Yan Tang(唐丽艳)
    Chin. Phys. B, 2021, 30 (8):  083102.  DOI: 10.1088/1674-1056/abf0fc
    Abstract ( 327 )   HTML ( 0 )   PDF (731KB) ( 63 )  
    The pursuit of a systematic frequency uncertainty beyond 10-18 clock has triggered a multitude of investigations on the multipolar and higher-order lattice light shifts. The Cd atom has been proposed as a new candidate for the development of a lattice clock because of its smaller blackbody radiation shift at room temperature. Here, we apply an improved combined method of the Dirac-Fock plus core polarization and relativistic configuration interaction methods to calculate the dynamic multipolar polarizabilities of the Cd clock states. The effects of the high-order core-polarization potentials on the energies, reduced matrix elements, and multipolar polarizabilities have been evaluated systematically. The detailed comparison with available literature demonstrates that taking into account of the high-order core-polarization potentials is a simple and effective approach to improve the results of atomic properties for heavy atoms.
    Density functional theory investigation on lattice dynamics, elastic properties and origin of vanished magnetism in Heusler compounds CoMnVZ (Z= Al, Ga) Hot!
    Guijiang Li(李贵江), Enke Liu(刘恩克), Guodong Liu(刘国栋), Wenhong Wang(王文洪), and Guangheng Wu(吴光恒)
    Chin. Phys. B, 2021, 30 (8):  083103.  DOI: 10.1088/1674-1056/ac0a6a
    Abstract ( 815 )   HTML ( 13 )   PDF (1511KB) ( 662 )  
    The lattice dynamics, elastic properties and the origin of vanished magnetism in equiatomic quaternary Heusler compounds CoMnVZ (Z=Al, Ga) are investigated by first principle calculations in this work. Due to the similar constituent atoms in CoMnVAl and CoMnVGa compounds, they are both stable in LiMgPdSn-type structure with comparable lattice size, phonon dispersions and electronic structures. Comparatively, we find that CoMnVAl is more structurally stable than CoMnVGa. Meanwhile, the increased covalent bonding component in CoMnVAl enhances its mechanical strength and Vickers hardness, which leads to better comprehensive mechanical properties than those of CoMnVGa. Practically and importantly, structural and chemical compatibilities at the interface make non-magnetic semiconductor CoMnVAl and magnetic topological semimetals Co2MnAl/Ga more suitable to be grown in heterostructures. Owing to atomic preferential occupation in CoMnVAl/Ga, the localized atoms Mn occupy C (0.5, 0.5, 0.5) Wyckoff site rather than B (0.25, 0.25, 0.25) and D (0.75, 0.75, 0.75) Wyckoff sites in LiMgPdSn-type structure, which results in symmetric band filling and consequently drives them to be non-magnetic. Correspondingly, by tuning localized atoms Mn to occupy B (0.25, 0.25, 0.25) or/and D (0.75, 0.75, 0.75) Wyckoff sites in off-stoichiometric Co-Mn-V-Al/Ga compounds and keeping the total valence electrons as 24, newly compensated ferrimagnetic compounds are theoretically achieved. We hope that our work will provide more choices for spintronic applications.
    X-ray emission for Ar11+ ions impacting on various targets in the collisions near the Bohr velocity
    Xian-Ming Zhou(周贤明), Jing Wei(尉静), Rui Cheng(程锐), Yan-Hong Chen(陈燕红), Ce-Xiang Mei(梅策香), Li-Xia Zeng(曾利霞), Chang-Hui Liang(梁昌慧), Yao-Zong Li(李耀宗), Yong-Tao Zhao(赵永涛), and Xiao-An Zhang(张小安)
    Chin. Phys. B, 2021, 30 (8):  083201.  DOI: 10.1088/1674-1056/abe22f
    Abstract ( 382 )   HTML ( 0 )   PDF (1104KB) ( 52 )  
    X-ray emission from the collisions of 3 MeV Ar11+ ions with V, Fe, Co, Ni, Cu, and Zn is investigated. Both the x-rays of the target atom and projectile are observed simultaneously. The x-ray yield is extracted from the original count. The inner-shell ionization cross section is estimated by the binary encounter approximation model and compared with the experimental result. The remarkable result is that the Ar K-shell x-ray yield is diminished with the target atomic number increasing, which is completely opposite to the theoretical calculation. That is interpreted by the competitive consumption of the energy loss for the ionization of inner-shell electrons between the projectile and target atom.
    An effective pumping method for increasing atomic utilization in a compact cold atom clock
    Xin-Chuan Ouyang(欧阳鑫川), Bo-Wen Yang(杨博文), Jian-Liao Deng(邓见辽), Jin-Yin Wan(万金银), Ling Xiao(肖玲), Hang-Hang Qi(亓航航), Qing-Qing Hu(胡青青), and Hua-Dong Cheng(成华东)
    Chin. Phys. B, 2021, 30 (8):  083202.  DOI: 10.1088/1674-1056/abfccd
    Abstract ( 420 )   HTML ( 0 )   PDF (1223KB) ( 84 )  
    We propose a simple pumping method to increase the effective population of cold atoms in the clock state and investigate the factors which affect the pumping efficiency in cold atom systems. We report the theory and demonstrate the corresponding experiment in an 87Rb integrating sphere cold atom clock. The experimental results show that the population of cold atoms in the Zeeman sublevel |F=2, mF=0> is approximately 1.62 times that of the result using optical pumping alone. This method can also be applied to increase the effective population in any one of the target Zeeman sublevels in other cold atom systems.
    Light-shift induced by two unbalanced spontaneous decay rates in EIT (CPT) spectroscopies under Ramsey pulse excitation
    Xiaoyan Liu(刘晓艳), Xu Zhao(赵旭), Jianfang Sun(孙剑芳), Zhen Xu(徐震), and Zhengfeng Hu(胡正峰)
    Chin. Phys. B, 2021, 30 (8):  083203.  DOI: 10.1088/1674-1056/ac0528
    Abstract ( 397 )   HTML ( 0 )   PDF (940KB) ( 223 )  
    Light shift is important and inevitably affects the long-term stability of an atomic clock. In this work, considering two unbalanced branches of the spontaneous decay rate in a three-level system, we studied the frequency shifts of electromagnetically induced transparency (EIT) and coherent population trapping (CPT) clocks operating under the pulse sequence regime by numerically solving the Liouville density matrix equations. The results show that the frequency shifts are larger when the two branches of spontaneous emission rate are not equal compared to the equal case. In addition, in EIT-Ramsey, the effect of the unbalanced branches of the spontaneous decay rate and relaxations of low-energy states on the frequency shift is greater than that of Rabi frequency. In CPT-Ramsey, the relaxations of low-energy states play a dominant role in frequency shift.
    Comparative study of photoionization of atomic hydrogen by solving the one- and three-dimensional time-dependent Schrödinger equations
    Shun Wang(王顺), Shahab Ullah Khan, Xiao-Qing Tian(田晓庆), Hui-Bin Sun(孙慧斌), and Wei-Chao Jiang(姜维超)
    Chin. Phys. B, 2021, 30 (8):  083301.  DOI: 10.1088/1674-1056/abea85
    Abstract ( 355 )   HTML ( 0 )   PDF (1592KB) ( 75 )  
    We develop a numerical scheme for solving the one-dimensional (1D) time-dependent Schrödinger equation (TDSE), and use it to study the strong-field photoionization of the atomic hydrogen. The photoelectron energy spectra obtained for pulses ranging from XUV to near infrared are compared in detail to the spectra calculated with our well-developed code for accurately solving the three-dimensional (3D) TDSE. For XUV pulses, our discussions cover intensities at which the ionization is in the perturbative and nonperturbative regimes. For pulses of 400 nm or longer wavelengths, we distinguish the multiphoton and tunneling regimes. Similarities and discrepancies between the 1D and 3D calculations in each regime are discussed. The observed discrepancies mainly originate from the differences in the transition matrix elements and the energy level structures created in the 1D and 3D calculations.
    Shared aperture metasurface antenna for electromagnetic vortices generation with different topological charges
    He Wang(王贺), Yong-Feng Li(李勇峰), and Shao-Bo Qu(屈绍波)
    Chin. Phys. B, 2021, 30 (8):  084101.  DOI: 10.1088/1674-1056/abe37c
    Abstract ( 361 )   HTML ( 0 )   PDF (5974KB) ( 109 )  
    Vortex beams carrying orbital angular momentum (OAM) have aroused great interest of both scientific and engineering communities. Encouragingly, generating OAM with different topological charges in a shared aperture is regarded as a potential route to expanding the communication capacity, which yet is an academic challenging task. In this work, a paradigm of designing metasurface-based shared aperture antenna for generating polarization-dependent vortex beams with distinct topological charges is proposed. Anisotropic unit cells that can tailor different resonance phase profiles in two orthogonal orientations are used to assemble a metasurface reflector. As a proof-of-concept, a planar reflector antenna is designed with two Vivaldi sources, which can generate x- and y-polarized vortex beams with topological charges of l=-1 and l=-2, respectively. Both the simulation results and the measurement results are in good agreement, which demonstrates the feasibility of our design. Significantly, this work provides a new route to achieving vortex beams carrying different topological charges in the same frequency band, which may have potential applications in communication systems.
    Surface plasmon polaritons frequency-blue shift in low confinement factor excitation region
    Ling-Xi Hu(胡灵犀), Zhi-Qiang He(何志强), Min Hu(胡旻), and Sheng-Gang Liu(刘盛纲)
    Chin. Phys. B, 2021, 30 (8):  084102.  DOI: 10.1088/1674-1056/abe22e
    Abstract ( 363 )   HTML ( 0 )   PDF (1191KB) ( 50 )  
    Surface plasmon polaritons' (SPPs') frequency blue shift is observed in finite-difference time-domain (FDTD) simulation of parallel electron excitation Au bulk structure. Comparing with cold dispersion of SPPs, an obvious frequency blue shift is obtained in low confinement region excitation simulation results. Then, according to SPPs' transverse attenuation characteristics, the excited frequency mode instead of cold dispersion corresponding frequency mode matches it. Thence, this excited mode is confirmed to be SPPs' mode. As is well known the lower the frequency, the smaller the confinement factor is and the lower the excitation efficiency, the wider the bandwidth of excited SPPs is. And considering the attenuation in whole structure, the excited surface field contains attenuation signal. In a low confinement factor region, the higher the SPPs' frequency, the higher the excitation efficiency is, while broadband frequency information obtained in attenuation signal provides high frequency information in stimulation signal. Thence, in the beam-wave interaction, as the signal oscillation time increases, the frequency of the oscillation field gradually increases. Thus, compared with cold dispersion, the frequency of excited SPP is blueshifted This hypothesis is verified by monitoring the time domain signal of excited field in low and high confinement factor regions and comparing them. Then, this frequency-blue shift is confirmed to have commonality of SPPs, which is independent of SPPs' material and structure. Finally, this frequency-blue shift is confirmed in an attenuated total reflection (ATR) experiment. Owing to frequency dependence of most of SPPs' devices, such as coherent enhancement radiation and enhancement transmission devices, the frequency-blue shift presented here is of great influence in the SPPs applications.
    A novel receiver-transmitter metasurface for a high-aperture-efficiency Fabry-Perot resonator antenna
    Peng Xie(谢鹏), Guangming Wang(王光明), Binfeng Zong(宗彬锋), and Xiaojun Zou(邹晓鋆)
    Chin. Phys. B, 2021, 30 (8):  084103.  DOI: 10.1088/1674-1056/ac0788
    Abstract ( 404 )   HTML ( 1 )   PDF (1404KB) ( 112 )  
    This paper presents a novel coupled receiver-transmitter metasurface (MS) which is used to realize a high-aperture-efficiency Fabry-Perot resonator antenna. The unit cell of the MS adopts a slot-coupling procedure to realize energy transmission from the receiver patch to the radiator patch. This approach makes it easier to independently control the transmission magnitude and phase. Based on this characteristic, the transmission coefficients of different unit cells on the MS can be optimized by a genetic algorithm. Then, nearly uniform electric amplitude and phase distribution across the aperture field of the antenna are achieved. Therefore, the gain and aperture efficiency of the antenna are improved. A prototype of the optimized antenna is fabricated and measured to validate the design. The measured gain of the fabricated antenna reaches 17.3 dBi with an aperture efficiency of 94.5%. A higher aperture efficiency is obtained with the proposed antenna which has a low profile and simple structure.
    Continuous-wave Nd:KGd(WO4)2 single-longitudinal-mode laser
    Rui-Jun Lan(兰瑞君), Guang-Hua Liu(刘广华), Huan-Huan Min(闵欢欢), Tong-Yu Dai(戴通宇), Ying-Jie Shen(申英杰), Peng-Hua Mu(穆鹏华), Cheng Ren(任承), De-Zhong Cao(曹德忠), and Xavier Mateos
    Chin. Phys. B, 2021, 30 (8):  084201.  DOI: 10.1088/1674-1056/abea99
    Abstract ( 343 )   HTML ( 0 )   PDF (1711KB) ( 44 )  
    A continuous-wave Nd:KGd(WO4)2 single-longitudinal-mode laser is demonstrated with Fabry-Perot etalons in a simple linear cavity. The thermal lens effect is dramatically lowered by propagating the laser beam along the ‘athermal’ direction inside the laser crystal, which is very beneficial to removing the heat generated in the mode selection process. The maximum single-longitudinal-mode output power obtained is 64.8 mW at incident pump power of 4.7 W, corresponding to an optical conversion efficiency of 1.3% and a slope efficiency of 1.7%.
    Omnidirectional and compact Tamm phonon-polaritons enhanced mid-infrared absorber
    Xiaomin Hua(花小敏), Gaige Zheng(郑改革), Fenglin Xian(咸冯林), Dongdong Xu(徐董董), and Shengyao Wang(王升耀)
    Chin. Phys. B, 2021, 30 (8):  084202.  DOI: 10.1088/1674-1056/abe22b
    Abstract ( 476 )   HTML ( 1 )   PDF (1417KB) ( 154 )  
    Narrow band mid-infrared (MIR) absorption is highly desired in thermal emitter and sensing applications. We theoretically demonstrate that the perfect absorption at infrared frequencies can be achieved and controlled around the surface phonon resonance frequency of silicon carbide (SiC). The photonic heterostructure is composed of a distributed Bragg reflector (DBR)/germanium (Ge) cavity/SiC on top of a Ge substrate. Full-wave simulation results illustrate that the Tamm phonon-polaritons electric field can locally concentrate between the Ge cavity and the SiC film, contributed to the improved light-phonon interactions with an enhancement of light absorption. The structure has planar geometry and does not require nano-patterning to achieve perfect absorption of both polarizations of the incident light in a wide range of incident angles. Their absorption lines are tunable via engineering of the photon band-structure of the dielectric photonic nanostructures to achieve reversal of the geometrical phase across the interface with the plasmonic absorber.
    Low-threshold bistable reflection assisted by oscillating wave interaction with Kerr nonlinear medium
    Yingcong Zhang(张颖聪), Wenjuan Cai(蔡文娟), Xianping Wang(王贤平), Wen Yuan(袁文), Cheng Yin(殷澄), Jun Li(李俊), Haimei Luo(罗海梅), and Minghuang Sang(桑明煌)
    Chin. Phys. B, 2021, 30 (8):  084203.  DOI: 10.1088/1674-1056/abe118
    Abstract ( 481 )   HTML ( 1 )   PDF (924KB) ( 77 )  
    Owing to the enormously enhanced oscillating wave, a minute variation of the incident light intensity will give rise to a change in the dielectric constant of the Kerr nonlinear medium and lead to a bistable reflection with an ultra-low threshold intensity, which is closely related to the angle of incidence and the thickness of the Kerr nonlinear medium. The criterion for the existence of optical bistability is derived. Our bistability scheme is simple and not limited to the TM-polarization.
    Generation of diffraction-free vectorial elliptic hollow beams with space-varying inhomogeneous polarizations
    Hui-Rong Li(李会容), Peng-Yi Zhao(赵朋义), and Jian-Ping Yin(印建平)
    Chin. Phys. B, 2021, 30 (8):  084204.  DOI: 10.1088/1674-1056/abe3e9
    Abstract ( 336 )   HTML ( 1 )   PDF (4011KB) ( 41 )  
    Diffraction-free vectorial elliptic hollow beams (vEHBs) are generated by an optical system composed of a short elliptic hollow fiber (EHF) and an axicon. Each beam has a closed elliptic annular intensity profile and space-varying polarization states in its diffraction-free distance of more than 1 m. The generated beams have a counter-clockwise or clockwise periodically-rotated inhomogeneous polarization. And the spin angular momentum (SAM) of the vEHBs is 1ħ or -1ħ which is consistent with the type of dual-mode in the EHF and the periodic polarization rotations of the vEHBs. The vEHBs have potential applications in optically trapping and micromanipulating the micro- or nano-particles, quantum information transmission, and Bose-Einstein condensates, etc.
    Distributed analysis of forward stimulated Brillouin scattering for acoustic impedance sensing by extraction of a 2nd-order local spectrum
    Yu-Lian Yang(杨玉莲), Jia-Bing Lin(林佳兵), Li-Ming Liu(刘黎明), Xin-Hong Jia(贾新鸿), Wen-Yan Liang(梁文燕), Shi-Rong Xu(许世蓉), and Li Jiang(姜利)
    Chin. Phys. B, 2021, 30 (8):  084205.  DOI: 10.1088/1674-1056/abfcce
    Abstract ( 379 )   HTML ( 0 )   PDF (8074KB) ( 210 )  
    Distributed fiber sensors based on forward stimulated Brillouin scattering (F-SBS) have attracted special attention because of their capability to detect the acoustic impedance of liquid material outside fiber. However, the reported results were based on the extraction of a 1st-order local spectrum, causing the sensing distance to be restricted by pump depletion. Here, a novel post-processing technique was proposed for distributed acoustic impedance sensing by extracting the 2nd-order local spectrum, which is beneficial for improving the sensing signal-to-noise ratio (SNR) significantly, since its pulse energy penetrates into the fiber more deeply. As a proof-of-concept, distributed acoustic impedance sensing along ~1630 m fiber under moderate spatial resolution of ~20 m was demonstrated.
    Solar energy full-spectrum perfect absorption and efficient photo-thermal generation
    Zhefu Liao(廖喆夫), Zhengqi Liu(刘正奇), Qizhao Wu(吴起兆), Xiaoshan Liu(刘晓山), Xuefeng Zhan(詹学峰), Gaorong Zeng(曾高荣), and Guiqiang Liu(刘桂强)
    Chin. Phys. B, 2021, 30 (8):  084206.  DOI: 10.1088/1674-1056/ac0696
    Abstract ( 451 )   HTML ( 0 )   PDF (1608KB) ( 192 )  
    Designing and manufacturing cost-effective absorbers that can cover the full-spectrum of solar irradiation is still critically important for solar harvesting. Utilizing control of the lightwave reflection and transmission, metamaterials realize high absorption over a relatively wide bandwidth. Here, a truncated circular cone metasurface (TCCM) composed of alternating multiple layers of titanium (Ti) and silicon dioxide (SiO2) is presented. Enabled by the synergetic of surface plasmon resonances and Fabry-Pérot resonances, the TCCM simultaneously achieves high absorptivity (exceed 90%), and absorption broadband covers almost the entire solar irradiation spectrum. In addition, the novel absorber exhibits great photo-thermal property. By exploiting the ultrahigh melting point of Ti and SiO2, high-efficiency solar irradiation absorption and heat release have been achieved at 700℃ when the solar concentration ratio is 500 (i.e., incident light intensity at 5×105 W/m2). It is worth noting that the photo-thermal efficiency is almost unchanged when the incident angle increases from 0° to 45°. The outstanding capacity for solar harvesting and light-to-heat reported in this paper suggests that TCCM has great potential in photothermal therapies, solar desalination, and radiative cooling, etc.
    Quantum storage of single photons with unknown arrival time and pulse shapes
    Yu You(由玉), Gong-Wei Lin(林功伟), Ling-Juan Feng(封玲娟), Yue-Ping Niu(钮月萍), and Shang-Qing Gong(龚尚庆)
    Chin. Phys. B, 2021, 30 (8):  084207.  DOI: 10.1088/1674-1056/abfbd3
    Abstract ( 346 )   HTML ( 0 )   PDF (789KB) ( 28 )  
    We present a scheme for the quantum storage of single photons using electromagnetically induced transparency (EIT) in a low-finesse optical cavity, assisted by state-selected spontaneous atomic emission. Mediated by the dark mode of cavity EIT, the destructive quantum interference between the cavity input-output channel and state-selected atomic spontaneous emission leads to strong absorption of single photons with unknown arrival time and pulse shapes. We discuss the application of this phenomenon to photon counting using stored light.
    A 37 mJ, 100 Hz, high energy single frequency oscillator
    Yu Shen(申玉), Yong Bo(薄勇), Nan Zong(宗楠), Shenjin Zhang(张申金), Qinjun Peng(彭钦军), and Zuyan Xu(许祖彦)
    Chin. Phys. B, 2021, 30 (8):  084208.  DOI: 10.1088/1674-1056/ac0694
    Abstract ( 362 )   HTML ( 0 )   PDF (1731KB) ( 105 )  
    Ways on energy enhancement for single frequency oscillator are reported in this paper. By quantitative analysis on gain and loss coefficients for each cavity mode with inserted etalons, a 37 mJ, 100 Hz high energy single-frequency Nd:YAG oscillator is obtained. The pulse energy is promoted by enhancement of nearly 7 times for a single frequency oscillator reported. The result proves that this method does help for energy enhancement. It has attractive potential for high energy single frequency oscillator design, especially on condition of intensive side pumped or long cavity laser, where strong competitors exist and are hard to be suppressed.
    Broad-band phase retrieval method for transient radial shearing interference using chirp Z transform technique
    Fang Xue(薛芳), Ya-Xuan Duan(段亚轩), Xiao-Yi Chen(陈晓义), Ming Li(李铭), Suo-Chao Yuan(袁索超), and Zheng-Shang Da(达争尚)
    Chin. Phys. B, 2021, 30 (8):  084209.  DOI: 10.1088/1674-1056/abff2f
    Abstract ( 482 )   HTML ( 0 )   PDF (3328KB) ( 116 )  
    The transient radial shearing interferometry technique based on fast Fourier transform (FFT) provides a means for the measurement of the wavefront phase of transient light field. However, which factors affect the spatial bandwidth of the wavefront phase measurement of this technology and how to achieve high-precision measurement of the broad-band transient wavefront phase are problems that need to be studied further. To this end, a theoretical model of phase-retrieved bandwidth of radial shearing interferometry is established in this paper. The influence of the spatial carrier frequency and the calculation window on phase-retrieved bandwidth is analyzed, and the optimal carrier frequency and calculation window are obtained. On this basis, a broad-band transient radial shearing interference phase-retrieval method based on chirp Z transform (CZT) is proposed, and the corresponding algorithm is given. Through theoretical simulation, a known phase is used to generate the interferogram and it is retrieved by the traditional method and the proposed method respectively. The residual wavefront RMS of the traditional method is 0.146λ, and it is 0.037λ for the proposed method, which manifests an improvement of accuracy by an order of magnitude. At the same time, different levels of signal-to-noise ratios (SNRs) from 50 dB to 10 dB of the interferogram are simulated, and the RMS of the residual wavefront is from 0.040λ to 0.066λ. In terms of experiments, an experimental verification device based on a phase-only spatial light modulator is built, and the known phase on the modulator is retrieved from the actual interferogram. The RMS of the residual wavefront retrieved through FFT is 0.112λ, and it decreases to 0.035λ through CZT. The experimental results verify the effectiveness of the method proposed in this paper. Furthermore, the method can be used in other types of spatial carrier frequency interference, such as lateral shearing interference, rotational shearing interference, flipping shearing interference, and four-wave shearing interference.
    A low-threshold multiwavelength Brillouin fiber laser with double-frequency spacing based on a small-core fiber
    Lu-Lu Xu(徐路路), Ying-Ying Wang(王莹莹), Li Jiang(江丽), Pei-Long Yang(杨佩龙), Lei Zhang(张磊), and Shi-Xun Dai(戴世勋)
    Chin. Phys. B, 2021, 30 (8):  084210.  DOI: 10.1088/1674-1056/abff47
    Abstract ( 411 )   HTML ( 0 )   PDF (1435KB) ( 63 )  
    We demonstrate multiwavelength Brillouin fiber lasers (MWBFLs) with double-frequency spacing based on a small-core fiber (SCF) and a standard single-mode fiber (SMF), which have core diameters of 5 and 8.8 μm, respectively. Experimental results show that the SCF-based MWBFL exhibits a higher laser output power and a lower pump threshold. The output powers of the SCF-based MWBFL are > 1.4 times those of the SMF-based MWBFL. Moreover, the threshold power required to generate each channel of the SCF-based MWBFL is 59% that of the SMF-based MWBFL. When the same pump power of 180 mW is injected, the number of laser channels generated for the SCF-based MWBFL is 13, which is twice that generated for the SMF-based MWBFL. In addition, the SCF-based MWBFL exhibits good wavelength tunability from 1535 to 1565 nm and temporal stability over an hour.
    SPECIAL TOPIC—Optical field manipulation
    Bound states in the continuum on perfect conducting reflection gratings
    Jianfeng Huang(黄剑峰), Qianju Song(宋前举), Peng Hu(胡鹏), Hong Xiang(向红), and Dezhuan Han(韩德专)
    Chin. Phys. B, 2021, 30 (8):  084211.  DOI: 10.1088/1674-1056/abeee4
    Abstract ( 572 )   HTML ( 1 )   PDF (863KB) ( 199 )  
    Bound states can be supported on the surface of a periodically corrugated perfect conductor known as spoof surface plasmon polaritons with their dispersion curves reside below the light line. Here we show that bound states in the continuum (BICs) can also be achieved in such systems. Two types of grating structures are proposed to suppress the radiation leakage and hence generate bound states. The first one is a simple grating with broad grooves in which multiple cavity modes are accommodated. Due to the symmetry incompatibility and the destructive interaction mainly from the TM0 and TM1 modes, BICs at the Γ point and at off-Γ points are both realized. The second one is a dimerized grating with two grooves in each unit cell. The destructive interaction between the modes in the two grooves can suppresses the radiation and BICs at the Γ point are observed. The Q factors of the whole bands can be further tuned by the dimerization strength effectively. This work may offer new opportunity for the applications of metallic grating in the low frequency bands.
    Impact of the spatial coherence on self-interference digital holography
    Xingbing Chao(潮兴兵), Yuan Gao(高源), Jianping Ding(丁剑平), and Hui-Tian Wang(王慧田)
    Chin. Phys. B, 2021, 30 (8):  084212.  DOI: 10.1088/1674-1056/abd766
    Abstract ( 372 )   HTML ( 0 )   PDF (4908KB) ( 151 )  
    Owing to the unique feature that the signal and reference waves of self-interference digital holography (SIDH) contain the same spatial information from the same point of object, compared with conventional digital holography, the SIDH has the special spatial coherence properties. We present a statistical optics approach to analyzing the formation of cross-correlation image in SIDH. Our study reveals that the spatial coherence of illumination light can greatly influence the imaging characteristics of SIDH, and the impact extent of the spatial coherence depends substantially on the recording distance of hologram. The theoretical conclusions are supported well by numerical simulation and optical experiments.
    Characterization of inner layer thickness change of a composite circular tube using nonlinear circumferential guided wave:A feasibility study
    Ming-Liang Li(李明亮), Guang-Jian Gao(高广健), and Ming-Xi Deng(邓明晰)
    Chin. Phys. B, 2021, 30 (8):  084301.  DOI: 10.1088/1674-1056/abe234
    Abstract ( 393 )   HTML ( 1 )   PDF (1293KB) ( 52 )  
    The feasibility of using the nonlinear effect of primary circumferential guided wave (CGW) propagation for characterizing the change of inner layer thickness of a composite circular tube (CCT) has been investigated. An appropriate mode pair of the fundamental and double-frequency CGWs (DFCGWs) has been selected to enable the second harmonics of primary wave mode in the given CCT to accumulate along the circumferential direction. When changes in the inner layer thickness (described as the equivalent inner layer thickness) take place, the corresponding nonlinear CGW measurements are conducted. It is found that there is a direct correlation between change of equivalent inner layer thickness of the CCT and the relative acoustic nonlinearity parameter (Δβ) measured with CGWs propagating through one full circumference, and that the effect of second-harmonic generation (SHG) is very sensitive to change in the inner layer thickness. The experimental result obtained demonstrates the feasibility for quantitatively assessing the change of equivalent inner layer thickness in CCTs using the effect of SHG by primary CGW propagation.
    Broadband topological valley-projected edge-states transport in composite structure phononic crystal
    Hong-Yong Mao(毛鸿勇), Fu-Jia Chen(陈福家), Kai Guo(郭凯), and Zhong-Yi Guo(郭忠义)
    Chin. Phys. B, 2021, 30 (8):  084302.  DOI: 10.1088/1674-1056/abea89
    Abstract ( 346 )   HTML ( 1 )   PDF (2919KB) ( 65 )  
    The topological valley transport, realized in phononic crystals, has aroused tremendous interest in these years. Many previous researches have further promoted the development of this transport phenomenon. Crucially, the bandwidth of the valley-projected edge mode has been an essential research topic. As is well known, the broadband will improve the adaptability of the acoustic edge-states, which will be more conducive to the transmission of information. Therefore, in this paper, we present a composite structure, composed of the atoms with different shapes forming a hexagonal lattice, which can achieve larger bandwidth than a single structure. Meanwhile, the results demonstrate that the topological protected edge states are also observed in our structure. Furthermore, the backscattering suppressions from associated valley-protected edge states under certain perturbations have also been investigated and demonstrated. Our work can provide a new idea for designing acoustic devices based on valley degree of freedom.
    Evolution of melt convection in a liquid metal driven by a pulsed electric current
    Yanyi Xu(徐燕祎), Yunhu Zhang(张云虎), Tianqing Zheng(郑天晴), Yongyong Gong(龚永勇), Changjiang Song(宋长江), Hongxing Zheng(郑红星), and Qijie Zhai(翟启杰)
    Chin. Phys. B, 2021, 30 (8):  084701.  DOI: 10.1088/1674-1056/ac0a6c
    Abstract ( 350 )   HTML ( 1 )   PDF (17498KB) ( 54 )  
    Gain refinement in metal alloy can be achieved by applying an electric current pulse (ECP) in solidification process. Forced flow inside the melt has been proved to be a key role in grain refinement. In this paper, the fluid flow inside Ga 20 wt%-In 12 wt%-Sn alloy induced by a damping sinusoidal ECP flowing through two parallel electrodes into the cylindrical melt was investigated by both experimental measurements and numerical simulations. Experimental results showed that a strong descending jet was induced beneath the bottom of electrodes under the application of ECP. Besides, it was found that flow intensity increases with the increase of amplitude, frequency, and pulse width, respectively. In order to unlock the formation mechanism of flow pattern and the relevance of flow intensity varied with electrical parameters, a three-dimensional numerical model under the application of ECP was established. Meanwhile, a comparative study was conducted by numerical simulations to reveal the distributions of electromagnetic fields and forced flow. Numerical results showed that the downward Lorentz force induced by ECP was concentrated beneath the bottom of electrodes. This downward Lorentz force induces a descending jet and provokes a global forced flow. According to numerical simulations, the evolution of flow intensity with electrical parameters under the application of ECP can be understood by the time averaged impulse of Lorentz force.
    Controllable preparation and disorder-dependent photoluminescence of morphologically different C60 microcrystals
    Wen Cui(崔雯), De-Jun Li(李德军), Jin-Liang Guo(郭金良), Lang-Huan Zhao(赵琅嬛), Bing-Bing Liu(刘冰冰), and Shi-Shuai Sun(孙士帅)
    Chin. Phys. B, 2021, 30 (8):  086101.  DOI: 10.1088/1674-1056/ac0691
    Abstract ( 367 )   HTML ( 0 )   PDF (3424KB) ( 140 )  
    Different C60 crystals were synthesized by precipitation from a mixture of the good solvent m-xylene and the poor solvent isopropyl alcohol. The samples were characterized by scanning electron microscopy (SEM), Raman spectroscopy, thermogravimetric analysis, and high resolution transmission electron microscope (HRTEM). We found that the morphologies and sizes of the samples could be controlled by adjusting the volume ratio between the good and poor solvents. Especially, an unexpected short flower column-like crystal was synthesized at low ratios (from 1:6 to 1:12). Room temperature photoluminescence (PL) and HRTEM studies of the C60 crystal samples reveal that the PL efficiency of the crystals decreases with increasing crystalline order and that the disordered C60 crystals synthesized at the ratio of 1:2 show 10 times higher PL efficiency than that of pristine C60. The mechanism of the growth process of these C60 crystals was also studied by replacing the good solvents m-xylene with toluene and mesitylene.
    SPECIAL TOPIC—Ion beam modification of materials and applications
    Evolution of helium bubbles in nickel-based alloy by post-implantation annealing
    Rui Zhu(朱睿), Qin Zhou(周钦), Li Shi(史力), Li-Bin Sun(孙立斌), Xin-Xin Wu(吴莘馨), Sha-Sha Lv(吕沙沙), and Zheng-Cao Li(李正操)
    Chin. Phys. B, 2021, 30 (8):  086102.  DOI: 10.1088/1674-1056/ac0783
    Abstract ( 431 )   HTML ( 0 )   PDF (3497KB) ( 144 )  
    Nickel-based alloys have been considered as candidate structural materials used in generation IV nuclear reactors serving at high temperatures. In the present study, alloy 617 was irradiated with 180-keV helium ions to a fluence of 3.6×1017 ions/cm2 at room temperature. Throughout the cross-section transmission electron microscopy (TEM) image, numerous over-pressurized helium bubbles in spherical shape are observed with the actual concentration profile a little deeper than the SRIM predicted result. Post-implantation annealing was conducted at 700 ℃ for 2 h to investigate the bubble evolution. The long-range migration of helium bubbles occurred during the annealing process, which makes the bubbles of the peak region transform into a faceted shape as well. Then the coarsening mechanism of helium bubbles at different depths is discussed and related to the migration and coalescence (MC) mechanism. With the diffusion of nickel atoms slowed down by the alloy elements, the migration and coalescence of bubbles are suppressed in alloy 617, leading to a better helium irradiation resistance.
    Microstructure evolution of T91 steel after heavy ion irradiation at 550 ℃
    Ligang Song(宋力刚), Bo Huang(黄波), Jianghua Li(李江华), Xianfeng Ma(马显锋), Yang Li(李阳), Zehua Fang(方泽华), Min Liu(刘敏), Jishen Jiang(蒋季伸), and Yanying Hu(胡琰莹)
    Chin. Phys. B, 2021, 30 (8):  086103.  DOI: 10.1088/1674-1056/ac0a64
    Abstract ( 612 )   HTML ( 1 )   PDF (7682KB) ( 185 )  
    Fe-Cr ferritic/martensitic (F/M) steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies. In this study, a widely-used ferritic/martensitic steel, T91 steel, was irradiated by 196-MeV Kr+ ions at 550 ℃. To reveal the irradiation mechanism, the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope (TEM). With increasing dose, the defects gradually changed from black dots to dislocation loops, and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations. When many dislocation loops of primary a0/2<111> type with high migration interacted with other defects or carbon atoms, it led to the production of dislocation segments and other dislocation loops of a0<100> type. Lots of defects accumulated near grain boundaries in the irradiated area, especially in the high-dose area. The grain boundaries of martensite laths acted as important sinks of irradiation defects in T91. Elevated temperature facilitated the migration of defects, leading to the accumulation of defects near the grain boundaries of martensite laths.
    Mechanism of defect evolution in H+ and He+ implanted InP
    Ren-Jie Liu(刘仁杰), Jia-Jie Lin(林家杰), N Daghbouj, Jia-Liang Sun(孙嘉良), Tian-Gui You(游天桂), Peng Gao(高鹏), Nie-Feng Sun(孙聂枫), and Min Liao(廖敏)
    Chin. Phys. B, 2021, 30 (8):  086104.  DOI: 10.1088/1674-1056/abf640
    Abstract ( 424 )   HTML ( 0 )   PDF (1486KB) ( 196 )  
    The defect evolution in InP with the 75 keV H+ and 115 keV He+ implantation at room temperature after subsequent annealing has been investigated in detail. With the same ion implantation fluence, the He+ implantation caused much broader damage distribution accompanied by much higher out-of-plane strain with respect to the H+ implanted InP. After annealing, the H+ implanted InP did not show any blistering or exfoliation on the surface even at the high fluence and the H2 molecules were stored in the heterogeneously oriented platelet defects. However, the He molecules were stored into the large bubbles which relaxed toward the free surface, creating blisters at the high fluence.
    Ion track-based nanowire arrays with gradient and programmable diameters towards rational light management
    Ran Huang(黄冉), Jiaming Zhang(张家明), Fangfang Xu(徐芳芳), Jie Liu(刘杰), Huijun Yao(姚会军), Yonghui Chen(陈永辉), and Jinglai Duan(段敬来)
    Chin. Phys. B, 2021, 30 (8):  086105.  DOI: 10.1088/1674-1056/ac078a
    Abstract ( 528 )   HTML ( 2 )   PDF (1192KB) ( 148 )  
    Integrating nanowires with nonuniform diameter and random spatial distribution into an array can afford unconventional and additional means for modulating optical response. However, experimental realization of such a nanowire array is quite challenging. In this work, we propose a new fabrication strategy which takes advantage of ion track technology, via sequential swift heavy ion irradiation and ion track etching. Based on this strategy, we unprecedentedly realize nanowire arrays, using gold as an example, with gradient and programmable diameters in a controlled manner. We further demonstrate that such nanowire arrays can support broadband, tunable, and enhanced plasmonic responses. We believe that our new type of nanowire arrays will find great potential in applications such as light management and optoelectronic devices.
    Helium-hydrogen synergistic effects on swelling in in-situ multiple-ion beams irradiated steels
    Haocheng Liu(刘昊成), Jia Huang(黄嘉), Liuxuan Cao(曹留煊), Yue Su(苏悦), Zhiying Gao(高智颖), Pengfei Ma(马鹏飞), Songqin Xia(夏松钦), Wei Ge(葛伟), Qingyuan Liu(刘清元), Shuang Zhao(赵双), Yugang Wang(王宇钢), Jinchi Huang(黄金池), Zhehui Zhou(周哲辉), Pengfei Zheng(郑鹏飞), and Chenxu Wang(王晨旭)
    Chin. Phys. B, 2021, 30 (8):  086106.  DOI: 10.1088/1674-1056/abfcca
    Abstract ( 595 )   HTML ( 1 )   PDF (7236KB) ( 210 )  
    The development of reliable fusion energy is one of the most important challenges in this century. The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe problems. Due to the lack of suitable fusion neutron testing facilities, we have to rely on ion irradiation experiments to test candidate materials in fusion reactors. Moreover, fusion neutron irradiation effects are accompanied by the simultaneous transmutation production of helium and hydrogen. One important method to study the He-H synergistic effects in materials is multiple simultaneous ion beams (MSIB) irradiation that has been studied for decades. To date, there is no convincing conclusion on these He-H synergistic effects among these experiments. Recently, a multiple ion beam in-situ transmission electron microscopy (TEM) analysis facility was developed in Xiamen University (XIAMEN facility), which is the first triple beam system and the only in-running in-situ irradiation facility with TEM in China. In this work, we conducted the first high-temperature triple simultaneous ion beams irradiation experiment with TEM observation using the XIAMEN facility. The responses to in-situ triple-ion beams irradiation in austenitic steel 304L SS and ferritic/martensitic steel CLF-1 were studied and compared with the results in dual- and single-ion beam(s) irradiated steels. Synergistic effects were observed in MSIB irradiated steels. Helium was found to be critical for cavity formation, while hydrogen has strong synergistic effect on increasing swelling.
    Formation of nano-twinned 3C-SiC grains in Fe-implanted 6H-SiC after 1500-℃ annealing
    Zheng Han(韩铮), Xu Wang(王旭), Jiao Wang(王娇), Qing Liao(廖庆), and Bingsheng Li(李炳生)
    Chin. Phys. B, 2021, 30 (8):  086107.  DOI: 10.1088/1674-1056/abff43
    Abstract ( 479 )   HTML ( 0 )   PDF (5811KB) ( 155 )  
    A nano-twinned microstructure was found in amorphous SiC after high-temperature annealing. Grazing incidence x-ray diffraction, high-resolution transmission electron microscopy, and electron diffraction were performed to characterize the microstructure and phase transition in the recrystallization layer. After 1500 ℃ or 2-h annealing, 3C-SiC grains and numerous stacking faults on the {111} planes were visible. Some 3C-SiC grains have nano-twinned structure with {011} planes. Between the nano-twinned 3C-SiC grains, there is a stacking fault, indicating that the formation mechanisms of the nano-twinned structure are related to the disorder of Si atoms. The increase in the twin thickness with increasing annealing temperature demonstrates that the nano-twinned structure can sink for lattice defects, in order to improve the radiation tolerance of SiC.
    Influence of helium on the evolution of irradiation-induced defects in tungsten: An object kinetic Monte Carlo simulation
    Peng-Wei Hou(侯鹏伟), Yu-Hao Li(李宇浩), Zhong-Zhu Li(李中柱), Li-Fang Wang(王丽芳), Xingyu Gao(高兴誉), Hong-Bo Zhou(周洪波), Haifeng Song(宋海峰), and Guang-Hong Lu(吕广宏)
    Chin. Phys. B, 2021, 30 (8):  086108.  DOI: 10.1088/1674-1056/abf7ac
    Abstract ( 569 )   HTML ( 0 )   PDF (930KB) ( 166 )  
    Understanding the evolution of irradiation-induced defects is of critical importance for the performance estimation of nuclear materials under irradiation. Hereby, we systematically investigate the influence of He on the evolution of Frenkel pairs and collision cascades in tungsten (W) via using the object kinetic Monte Carlo (OKMC) method. Our findings suggest that the presence of He has significant effect on the evolution of irradiation-induced defects. On the one hand, the presence of He can facilitate the recombination of vacancies and self-interstitial atoms (SIAs) in W. This can be attributed to the formation of immobile He-SIA complexes, which increases the annihilation probability of vacancies and SIAs. On the other hand, due to the high stability and low mobility of He-vacancy complexes, the growth of large vacancy clusters in W is kinetically suppressed by He addition. Specially, in comparison with the injection of collision cascades and He in sequential way at 1223 K, the average sizes of surviving vacancy clusters in W via simultaneous way are smaller, which is in good agreement with previous experimental observations. These results advocate that the impurity with low concentration has significant effect on the evolution of irradiation-induced defects in materials, and contributes to our understanding of W performance under irradiation.
    In-situ TEM observation of the evolution of helium bubbles in Mo during He+ irradiation and post-irradiation annealing
    Yi-Peng Li(李奕鹏), Guang Ran(冉广), Xin-Yi Liu(刘歆翌), Xi Qiu(邱玺), Qing Han(韩晴), Wen-Jie Li(李文杰), and Yi-Jia Guo(郭熠佳)
    Chin. Phys. B, 2021, 30 (8):  086109.  DOI: 10.1088/1674-1056/abff48
    Abstract ( 671 )   HTML ( 0 )   PDF (5196KB) ( 173 )  
    The evolution of helium bubbles in purity Mo was investigated by in-situ transmission electron microscopy (TEM) during 30 keV He+ irradiation (at 673 K and 1173 K) and post-irradiation annealing (after 30 keV He+ irradiation with the fluence of 5.74×1016 He+/cm2 at 673 K). Both He+ irradiation and subsequently annealing induced the initiation, aggregation, and growth of helium bubbles. Temperature had a significant effect on the initiation and evolution of helium bubbles. The higher the irradiation temperature was, the larger the bubble size at the same irradiation fluence would be. At 1173 K irradiation, helium bubbles nucleated and grew preferentially at grain boundaries and showed super large size, which would induce the formation of microcracks. At the same time, the geometry of helium bubbles changed from sphericity to polyhedron. The polyhedral bubbles preferred to grow in the shape bounded by {100} planes. After statistical analysis of the characteristic parameters of helium bubbles, the functions between the average size, number density of helium bubbles, swelling rate and irradiation damage were obtained. Meanwhile, an empirical formula for calculating the size of helium bubbles during the annealing was also provided.
    Modification of short-range repulsive interactions in ReaxFF reactive force field for Fe-Ni-Al alloy
    Huaqiang Chen(陈华强), Lin Lang(稂林), Shuaiyu Yi(易帅玉), Jinlong Du(杜进隆), Guangdong Liu(刘广东), Lixia Liu(刘丽霞), Yufei Wang(王宇飞), Yuehui Wang(王悦辉), Huiqiu Deng(邓辉球), and Engang Fu(付恩刚)
    Chin. Phys. B, 2021, 30 (8):  086110.  DOI: 10.1088/1674-1056/ac0901
    Abstract ( 528 )   HTML ( 1 )   PDF (7473KB) ( 242 )  
    The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics (MD) simulations. In this work, the short-range repulsive interaction of a reactive force field (ReaxFF), describing Fe-Ni-Al alloy system, is well modified by adding a tabulated function form based on Ziegler-Biersack-Littmark (ZBL) potential. The modified interaction covers three ranges, including short range, smooth range, and primordial range. The short range is totally predominated by ZBL potential. The primordial range means the interactions in this range is the as-is ReaxFF with no changes. The smooth range links the short-range ZBL and primordial-range ReaxFF potentials with a taper function. Both energies and forces are guaranteed to be continuous, and qualified to the consistent requirement in LAMMPS. This modified force field is applicable for simulations of energetic particle bombardments and reproducing point defects' booming and recombination effectively.
    Effect of Mo doping on phase change performance of Sb2Te3
    Wan-Liang Liu(刘万良), Ying Chen(陈莹), Tao Li(李涛), Zhi-Tang Song(宋志棠), and Liang-Cai Wu(吴良才)
    Chin. Phys. B, 2021, 30 (8):  086801.  DOI: 10.1088/1674-1056/abe22d
    Abstract ( 400 )   HTML ( 1 )   PDF (1523KB) ( 129 )  
    Mo, as a dopant, is doped into SbTe to improve its thermal stability. It is shown in this paper that the Mo-doped Sb2Te3 (Mo0.26Sb2Te3, MST) material possesses phase change memory (PCM) applications. MST has better thermal stability than Sb2Te3(ST) and will crystallize only when the annealing temperature is higher than 250 ℃. With the good thermal stability, MST-based PCM cells have a fast crystallization time of 6 ns. Furthermore, endurance up to 4×105 cycles with a resistance ratio of more than one order of magnitude makes MST a promising candidate for PCM applications.
    CeAu2In4: A candidate of quasi-one-dimensional antiferromagnetic Kondo lattice Hot!
    Meng Lyu(吕孟), Hengcan Zhao(赵恒灿), Jiahao Zhang(张佳浩), Zhen Wang(王振), Shuai Zhang(张帅), and Peijie Sun(孙培杰)
    Chin. Phys. B, 2021, 30 (8):  087101.  DOI: 10.1088/1674-1056/ac0a60
    Abstract ( 484 )   HTML ( 0 )   PDF (1950KB) ( 331 )  
    Needle-like single crystals of CeAu2In4 have been grown from In flux and characterized as a new candidate of quasi-one-dimensional Kondo lattice compound by crystallographic, magnetic, transport, and specific-heat measurements down to very low temperatures. We observe an antiferromagnetic transition at TN ≈ 0.9 K, a highly non-mean-field profile of the corresponding peak in specific heat, and a large Sommerfeld coefficient γ =369 mJ·mol-1·K-2. The Kondo temperature TK is estimated to be 1.1 K, being low and comparable to TN. While Fermi liquid behavior is observed deep into the magnetically ordered phase, the Kadowaki-Woods ratio is much reduced relative to the expected value for Ce compounds with Kramers doublet ground state. Markedly, this feature shares striking similarities to that of the prototypical quasi-one-dimensional compounds YbNi4P2 and CeRh6Ge4 with tunable ferromagnetic quantum critical point. Given the shortest Ce-Ce distance along the needle direction, CeAu2In4 appears to be an interesting model system for exploring antiferromagnetic quantum critical behaviors in a quasi-one-dimensional Kondo lattice with enhanced quantum fluctuations.
    High-frequency enhancement-mode millimeterwave AlGaN/GaN HEMT with an fT/fmax over 100 GHz/200 GHz
    Sheng Wu(武盛), Minhan Mi(宓珉瀚), Xiaohua Ma(马晓华), Ling Yang(杨凌), Bin Hou(侯斌), and Yue Hao(郝跃)
    Chin. Phys. B, 2021, 30 (8):  087102.  DOI: 10.1088/1674-1056/ac04a5
    Abstract ( 567 )   HTML ( 2 )   PDF (1074KB) ( 185 )  
    Ultra-thin barrier (UTB) 4-nm-AlGaN/GaN normally-off high electron mobility transistors (HEMTs) having a high current gain cut-off frequency (fT) are demonstrated by the stress-engineered compressive SiN trench technology. The compressive in-situ SiN guarantees the UTB-AlGaN/GaN heterostructure can operate a high electron density of 1.27×1013cm-2, a high uniform sheet resistance of 312.8 Ω /□, but a negative threshold for the short-gate devices fabricated on it. With the lateral stress-engineering by full removing in-situ SiN in the 600-nm SiN trench, the short-gated (70 nm) devices obtain a threshold of 0.2 V, achieving the devices operating at enhancement-mode (E-mode). Meanwhile, the novel device also can operate a large current of 610 mA/mm and a high transconductance of 394 mS/mm for the E-mode devices. Most of all, a high fT/fmax of 128 GHz/255 GHz is obtained, which is the highest value among the reported E-mode AlGaN/GaN HEMTs. Besides, being together with the 211 GHz/346 GHz of fT/fmax for the D-mode HEMTs fabricated on the same materials, this design of E/D-mode with the realization of fmax over 200 GHz in this work is the first one that can be used in Q-band mixed-signal application with further optimization. And the minimized processing difference between the E- and D-mode designs the addition of the SiN trench, will promise an enormous competitive advantage in the fabricating costs.
    Group velocity matters for accurate prediction of phonon-limited carrier mobility Hot!
    Qiao-Lin Yang(杨巧林), Hui-Xiong Deng(邓惠雄), Su-Huai Wei(魏苏淮), and Jun-Wei Luo(骆军委)
    Chin. Phys. B, 2021, 30 (8):  087201.  DOI: 10.1088/1674-1056/ac0133
    Abstract ( 463 )   HTML ( 0 )   PDF (828KB) ( 265 )  
    First-principles approaches have recently been developed to replace the phenomenological modeling approaches with adjustable parameters for calculating carrier mobilities in semiconductors. However, in addition to the high computational cost, it is still a challenge to obtain accurate mobility for carriers with a complex band structure, e.g., hole mobility in common semiconductors. Here, we present a computationally efficient approach using isotropic and parabolic bands to approximate the anisotropy valence bands for evaluating group velocities in the first-principles calculations. This treatment greatly reduces the computational cost in two ways: relieves the requirement of an extremely dense κ mesh to obtain a smooth change in group velocity, and reduces the 5-dimensional integral to 3-dimensional integral. Taking Si and SiC as two examples, we find that this simplified approach reproduces the full first-principles calculation for mobility. If we use experimental effective masses to evaluate the group velocity, we can obtain hole mobility in excellent agreement with experimental data over a wide temperature range. These findings shed light on how to improve the first-principles calculations towards predictive carrier mobility in high accuracy.
    Observation of large in-plane anisotropic transport in van der Waals semiconductor Nb2SiTe4
    Kaiyao Zhou(周楷尧), Jun Deng(邓俊), Long Chen(陈龙), Wei Xia(夏威), Yanfeng Guo(郭艳峰), Yang Yang(杨洋), Jian-Gang Guo(郭建刚), and Liwei Guo(郭丽伟)
    Chin. Phys. B, 2021, 30 (8):  087202.  DOI: 10.1088/1674-1056/ac068f
    Abstract ( 383 )   HTML ( 1 )   PDF (1880KB) ( 186 )  
    Two-dimensional (2D) van der Waals material is a focus of research for its widespread application in optoelectronics, memories, and spintronics. The ternary compound Nb2SiTe4 is a van der Waals semiconductor with excellent air stability and small cleavage energy, which is suitable for preparing a few layers counterpart to explore novel properties. Here, properties of bulk Nb2SiTe4 with large in-plane electrical anisotropy are demonstrated. It is found that hole carriers dominate at a temperature above 45 K with a carrier active energy of 31.3 meV. The carrier mobility measured at 100 K is about 213 cm2·V-1·s-1 in bulk Nb2SiTe4, higher than the reported results. In a thin flake Nb2SiTe4, the resistivity ratio between the crystalline axes of a and b is reaching about 47.3 at 2.5 K, indicating that there exists a large anisotropic transport behavior in their basal plane. These novel transport properties provide accurate information for modulating or utilizing Nb2SiTe4 for electronic device applications.
    Accurate capacitance-voltage characterization of organic thin films with current injection
    Ming Chu(褚明), Shao-Bo Liu(刘少博), An-Ran Yu(蔚安然), Hao-Miao Yu(于浩淼), Jia-Jun Qin(秦佳俊), Rui-Chen Yi(衣睿宸), Yuan Pei(裴远), Chun-Qin Zhu(朱春琴), Guang-Rui Zhu(朱光瑞), Qi Zeng(曾琪), and Xiao-Yuan Hou(侯晓远)
    Chin. Phys. B, 2021, 30 (8):  087301.  DOI: 10.1088/1674-1056/abe3e4
    Abstract ( 472 )   HTML ( 1 )   PDF (974KB) ( 74 )  
    To deal with the invalidation of commonly employed series model and parallel model in capacitance-voltage (C-V) characterization of organic thin films when current injection is significant, a three-element equivalent circuit model is proposed. On this basis, the expression of real capacitance in consideration of current injection is theoretically derived by small-signal analysis method. The validity of the proposed equivalent circuit and theoretical expression are verified by a simulating circuit consisting of a capacitor, a diode, and a resistor. Moreover, the accurate C-V characteristic of an organic thin film device is obtained via theoretical correction of the experimental measuring result, and the real capacitance is 35.7% higher than the directly measured capacitance at 5-V bias in the parallel mode. This work strongly demonstrates the necessity to consider current injection in C-V measurement and provides a strategy for accurate C-V characterization experimentally.
    A simple method to synthesize worm-like AlN nanowires and its field emission studies
    Qi Liang(梁琦), Meng-Qi Yang(杨孟骐), Chang-Hao Wang(王长昊), and Ru-Zhi Wang(王如志)
    Chin. Phys. B, 2021, 30 (8):  087302.  DOI: 10.1088/1674-1056/abe3e7
    Abstract ( 358 )   HTML ( 0 )   PDF (1930KB) ( 40 )  
    The worm-like AlN nanowires are fabricated by the plasma-enhanced chemical vapor deposition (PECVD) on Si substrates through using Al powder and N2 as precursors, CaF2 as fluxing medium, Au as catalyst, respectively. The as-grown worm-like AlN nanowires each have a polycrystalline and hexagonal wurtzite structure. Their diameters are about 300 nm, and the lengths are over 10 μm. The growth mechanism of worm-like AlN nanowires is discussed. Hydrogen plasma plays a very important role in forming the polycrystalline structure and rough surfaces of worm-like AlN nanowires. The worm-like AlN nanowires exhibit an excellent field-emission (FE) property with a low turn-on field of 4.5 V/μm at a current density of 0.01 mA/cm2 and low threshold field of 9.9 V/μm at 1 mA/cm2. The emission current densities of worm-like AlN nanowires each have a good stability. The enhanced FE properties of worm-like AlN nanowires may be due to their polycrystalline and rough structure with nanosize and high aspect ratio. The excellent FE properties of worm-like AlN nanowires can be explained by a grain boundary conduction mechanism. The results demonstrate that the worm-like AlN nanowires prepared by the proposed simple and the PECVD method possesses the potential applications in photoelectric and field-emission devices.
    Effect of surface oxygen vacancy defects on the performance of ZnO quantum dots ultraviolet photodetector
    Hongyu Ma(马宏宇), Kewei Liu(刘可为), Zhen Cheng(程祯), Zhiyao Zheng(郑智遥), Yinzhe Liu(刘寅哲), Peixuan Zhang(张培宣), Xing Chen(陈星), Deming Liu(刘德明), Lei Liu(刘雷), and Dezhen Shen(申德振)
    Chin. Phys. B, 2021, 30 (8):  087303.  DOI: 10.1088/1674-1056/ac0131
    Abstract ( 476 )   HTML ( 2 )   PDF (2949KB) ( 192 )  
    The slower response speed is the main problem in the application of ZnO quantum dots (QDs) photodetector, which has been commonly attributed to the presence of excess oxygen vacancy defects and oxygen adsorption/desorption processes. However, the detailed mechanism is still not very clear. Herein, the properties of ZnO QDs and their photodetectors with different amounts of oxygen vacancy (VO) defects controlled by hydrogen peroxide (H2O2) solution treatment have been investigated. After H2O2 solution treatment, VO concentration of ZnO QDs decreased. The H2O2 solution-treated device has a higher photocurrent and a lower dark current. Meanwhile, with the increase in VO concentration of ZnO QDs, the response speed of the device has been improved due to the increase of oxygen adsorption/desorption rate. More interestingly, the response speed of the device became less sensitive to temperature and oxygen concentration with the increase of VO defects. The findings in this work clarify that the surface VO defects of ZnO QDs could enhance the photoresponse speed, which is helpful for sensor designing.
    Magneto-transport properties of thin flakes of Weyl semiconductor tellurium
    Nan Zhang(张南), Bin Cheng(程斌), Hui Li(李惠), Lin Li(李林), and Chang-Gan Zeng(曾长淦)
    Chin. Phys. B, 2021, 30 (8):  087304.  DOI: 10.1088/1674-1056/ac0a5e
    Abstract ( 795 )   HTML ( 23 )   PDF (7248KB) ( 535 )  
    As an elemental semiconductor, tellurium has recently attracted intense interest due to its non-trivial band topology, and the resulted intriguing topological transport phenomena. In this study we report systematic electronic transport studies on tellurium flakes grown via a simple vapor deposition process. The sample is self-hole-doped, and exhibits typical weak localization behavior at low temperatures. Substantial negative longitudinal magnetoresistance under parallel magnetic field is observed over a wide temperature region, which is considered to share the same origin with that in tellurium bulk crystals, i.e., the Weyl points near the top of valence band. However, with lowering temperature the longitudinal magnetoconductivity experiences a transition from parabolic to linear field dependency, differing distinctly from the bulk counterparts. Further analysis reveals that such a modulation of Weyl behaviors in this low-dimensional tellurium structure can be attributed to the enhanced inter-valley scattering at low temperatures. Our results further extend Weyl physics into a low-dimensional semiconductor system, which may find its potential application in designing topological semiconductor devices.
    Investigation on threshold voltage of p-channel GaN MOSFETs based on p-GaN/AlGaN/GaN heterostructure
    Ruo-Han Li(李若晗), Wu-Xiong Fei(费武雄), Rui Tang(唐锐), Zhao-Xi Wu(吴照玺), Chao Duan(段超), Tao Zhang(张涛), Dan Zhu(朱丹), Wei-Hang Zhang(张苇杭), Sheng-Lei Zhao(赵胜雷), Jin-Cheng Zhang(张进成), and Yue Hao(郝跃)
    Chin. Phys. B, 2021, 30 (8):  087305.  DOI: 10.1088/1674-1056/ac0793
    Abstract ( 495 )   HTML ( 5 )   PDF (830KB) ( 162 )  
    The threshold voltage (Vth) of the p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) is investigated via Silvaco-Atlas simulations. The main factors which influence the threshold voltage of p-channel GaN MOSFETs are barrier height Φ1,p, polarization charge density σb, and equivalent unite capacitance Coc. It is found that the thinner thickness of p-GaN layer and oxide layer will acquire the more negative threshold voltage Vth, and threshold voltage |Vth| increases with the reduction in p-GaN doping concentration and the work-function of gate metal. Meanwhile, the increase in gate dielectric relative permittivity may cause the increase in threshold voltage |Vth|. Additionally, the parameter influencing output current most is the p-GaN doping concentration, and the maximum current density is 9.5 mA/mm with p-type doping concentration of 9.5×1016 cm-3 at VGS = -12 V and VDS = -10 V.
    Signatures of strong interlayer coupling in γ-InSe revealed by local differential conductivity Hot!
    Xiaoshuai Fu(富晓帅), Li Liu(刘丽), Li Zhang(张力), Qilong Wu(吴奇龙), Yu Xia(夏雨), Lijie Zhang(张利杰), Yuan Tian(田园), Long-Jing Yin(殷隆晶), and Zhihui Qin(秦志辉)
    Chin. Phys. B, 2021, 30 (8):  087306.  DOI: 10.1088/1674-1056/abff32
    Abstract ( 464 )   HTML ( 0 )   PDF (5948KB) ( 314 )  
    Interlayer coupling in layered semiconductors can significantly affect their optoelectronic properties. However, understanding the mechanisms behind the interlayer coupling at the atomic level is not straightforward. Here, we study modulations of the electronic structure induced by the interlayer coupling in the γ-phase of indium selenide (γ-InSe) using scanning probe techniques. We observe a strong dependence of the energy gap on the sample thickness and a small effective mass along the stacking direction, which are attributed to strong interlayer coupling. In addition, the moiré patterns observed in γ-InSe display a small band-gap variation and nearly constant local differential conductivity along the patterns. This suggests that modulation of the electronic structure induced by the moiré potential is smeared out, indicating the presence of a significant interlayer coupling. Our theoretical calculations confirm that the interlayer coupling in γ-InSe is not only of the van der Waals origin, but also exhibits some degree of hybridization between the layers. Strong interlayer coupling might play an important role in the performance of γ-InSe-based devices.
    Giant Rashba-like spin-orbit splitting with distinct spin texture in two-dimensional heterostructures
    Jianbao Zhu(朱健保), Wei Qin(秦维), and Wenguang Zhu(朱文光)
    Chin. Phys. B, 2021, 30 (8):  087307.  DOI: 10.1088/1674-1056/ac0784
    Abstract ( 598 )   HTML ( 1 )   PDF (2029KB) ( 249 )  
    Based on first-principles density functional theory calculation, we discover a novel form of spin-orbit (SO) splitting in two-dimensional (2D) heterostructures composed of a single Bi(111) bilayer stacking with a 2D semiconducting In2Se2 or a 2D ferroelectric α-In2Se3 layer. Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum, where the chirality of the spin texture reverses within the upper spin-split branch, in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point. The ferroelectric nature of α-In2Se3 further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field. Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction. This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications.
    Epitaxial growth and transport properties of compressively-strained Ba2IrO4 films
    Yun-Qi Zhao(赵蕴琦), Heng Zhang(张衡), Xiang-Bin Cai(蔡祥滨), Wei Guo(郭维), Dian-Xiang Ji(季殿祥), Ting-Ting Zhang(张婷婷), Zheng-Bin Gu(顾正彬), Jian Zhou(周健), Ye Zhu(朱叶), and Yue-Feng Nie(聂越峰)
    Chin. Phys. B, 2021, 30 (8):  087401.  DOI: 10.1088/1674-1056/abea97
    Abstract ( 431 )   HTML ( 1 )   PDF (2252KB) ( 77 )  
    Ba2IrO4 is a sister compound of the widely investigated Sr2IrO4 and has no IrO6 octahedral rotation nor net canted antiferromagnetic moment, thus it acts as a system more similar to the high-Tc cuprate. In this work, we synthesize the Ba2IrO4 epitaxial films by reactive molecular beam epitaxy and study their crystalline structure and transport properties under biaxial compressive strain. High resolution scanning transmission electron microscopy and x-ray diffraction confirm the high quality of films with partial strain relaxation. Under compressive epitaxial strain, the Ba2IrO4 exhibits the strain-driven enhancement of the conductivity, consistent with the band gap narrowing and the stronger hybridization of Ir-t2g and O-2p orbitals predicted in the first-principles calculations.
    Excess-iron driven spin glass phase in Fe1+yTe1-xSex Hot!
    Long Tian(田龙), Panpan Liu(刘盼盼), Tao Hong(洪涛), Tilo Seydel, Xingye Lu(鲁兴业), Huiqian Luo(罗会仟), Shiliang Li(李世亮), and Pengcheng Dai(戴鹏程)
    Chin. Phys. B, 2021, 30 (8):  087402.  DOI: 10.1088/1674-1056/ac0695
    Abstract ( 616 )   HTML ( 0 )   PDF (1310KB) ( 215 )  
    The iron-chalcogenide superconductor FeTe1-xSex displays a variety of exotic features distinct from iron pnictides. Although much effort has been devoted to understanding the interplay between magnetism and superconductivity near x=0.5, the existence of a spin glass phase with short-range magnetic order in the doping range (x~0.1-0.3) has rarely been studied. Here, we use DC/AC magnetization and (quasi) elastic neutron scattering to confirm the spin-glass nature of the short-range magnetic order in a Fe1.07Te0.8Se0.2 sample. The AC-frequency dependent spin-freezing temperature Tf generates a frequency sensitivity ΔTf(ω) /[Tf(ω) Δlog10ω]≈0.028 and the description of the critical slowing down with τ=τ0(Tf / TSG)-zv gives TSG≈22 K and zv≈10, comparable to that of a classical spin-glass system. We have also extended the frequency-dependent Tf to the smaller time scale using energy-resolution-dependent neutron diffraction measurements, in which the TN of the short-range magnetic order increases systematically with increasing energy resolution. By removing the excess iron through annealing in oxygen, the spin-freezing behavior disappears, and bulk superconductivity is realized. Thus, the excess Fe is the driving force for the formation of the spin-glass phase detrimental to bulk superconductivity.
    Ground-state phase diagram of the dimerizedspin-1/2 two-leg ladder
    Cong Fu(傅聪), Hui Zhao(赵晖), Yu-Guang Chen(陈宇光), and Yong-Hong Yan(鄢永红)
    Chin. Phys. B, 2021, 30 (8):  087501.  DOI: 10.1088/1674-1056/abec31
    Abstract ( 353 )   HTML ( 0 )   PDF (1104KB) ( 75 )  
    Dimerized spin-1/2 ladders exhibit a variety of phase structures, which depend on the intra-chain and inter-chain spin exchange energies as well as on the dimerization pattern of the ladder. Using the density matrix renormalization group (DMRG) algorithm, we study critical properties of the bond-alternating two-leg Heisenberg spin ladder with diagonal interaction J×. Two types of spin systems, staggered dimerized antiferromagnetic ladder and columnar dimerized ferro-antiferromagnetic couplings ladder, are investigated. To clarify the phase transition behaviors, we simultaneously analyze the string order parameter (SOP), the twisted order parameter (TOP), as well as a measurement of the quantum information analysis. Based on measuring this different observables, we establish the phase diagram accurately and give the fitting functions of the phase boundaries. In addition, the phase transition of cross-coupled spin ladder (in the absence of intrinsic dimerization) is also discussed.
    Microstructure and magnetocaloric properties in melt-spun and high-pressure hydrogenated La0.5Pr0.5Fe11.4Si1.6 ribbons
    Qian Liu(刘倩), Min Tong(佟敏), Xin-Guo Zhao(赵新国), Nai-Kun Sun(孙乃坤), Xiao-Fei Xiao(肖小飞), Jie Guo(郭杰), Wei Liu(刘伟), and Zhi-Dong Zhang(张志东)
    Chin. Phys. B, 2021, 30 (8):  087502.  DOI: 10.1088/1674-1056/abea91
    Abstract ( 359 )   HTML ( 0 )   PDF (2128KB) ( 76 )  
    The effects of wheel speeds and high-pressure hydrogen treatment on phase evolution, microstructure, and magnetocaloric properties in La0.5Pr0.5Fe11.4Si1.6 melt-spun ribbons are studied in this work. The results reveal that the increase of wheel speed is beneficial to the formation of cubic NaZn13-type phase and the grain refinement. The optimized wheel speed for microstructural and magnetocaloric properties is 30 m/s. The largest entropy change of 18.1 J/kg·K at 190 K under a magnetic field change of 0 T-5 T is obtained in La0.5Pr0.5Fe11.4Si1.6 ribbons melt-spun at 30 m/s. After a high-pressure hydrogen treatment of 50 MPa, the Curie temperature of the ribbons prepared at 30 m/s is adjusted to about 314 K and the large -ΔSM of 17.9 J/kg·K under a magnetic field change of 0 T-5 T is achieved at room temperature with almost none hysteresis loss. The small thermal and magnetic hysteresis and the large -ΔSM make the La0.5Pr0.5Fe11.4Si1.6 hydride ribbons appropriate for magnetic refrigerant applications around room temperature.
    Effective model for rare-earth Kitaev materials and its classical Monte Carlo simulation Hot!
    Mengjie Sun(孙梦杰), Huihang Lin(林慧航), Zheng Zhang(张政), Yanzhen Cai(蔡焱桢), Wei Ren(任玮), Jing Kang(康靖), Jianting Ji(籍建葶), Feng Jin(金峰), Xiaoqun Wang(王孝群), Rong Yu(俞榕), Qingming Zhang(张清明), and Zhengxin Liu(刘正鑫)
    Chin. Phys. B, 2021, 30 (8):  087503.  DOI: 10.1088/1674-1056/ac0a5d
    Abstract ( 628 )   HTML ( 0 )   PDF (2226KB) ( 364 )  
    Recently, the family of rare-earth chalcohalides were proposed as candidate compounds to realize the Kitaev spin liquid (KSL) [Chin. Phys. Lett. 38 047502 (2021)]. In the present work, we firstly propose an effective spin Hamiltonian consistent with the symmetry group of the crystal structure. Then we apply classical Monte Carlo simulations to preliminarily study the model and establish a phase diagram. When approaching to the low temperature limit, several magnetic long range orders are observed, including the stripe, the zigzag, the antiferromagnetic (AFM), the ferromagnetic (FM), the incommensurate spiral (IS), the multi-Q, and the 120° ones. We further calculate the thermodynamic properties of the system, such as the temperature dependence of the magnetic susceptibility and the heat capacity. The ordering transition temperatures reflected in the two quantities agree with each other. For most interaction regions, the system is magnetically more susceptible in the ab-plane than in the c-direction. The stripe phase is special, where the susceptibility is fairly isotropic in the whole temperature region. These features provide useful information to understand the magnetic properties of related materials.
    Achieving high-performance multilayer MoSe2 photodetectors by defect engineering
    Jintao Hong(洪锦涛), Fengyuan Zhang(张丰源), Zheng Liu(刘峥), Jie Jiang(蒋杰), Zhangting Wu(吴章婷), Peng Zheng(郑鹏), Hui Zheng(郑辉), Liang Zheng(郑梁), Dexuan Huo(霍德璇), Zhenhua Ni(倪振华), and Yang Zhang(张阳)
    Chin. Phys. B, 2021, 30 (8):  087801.  DOI: 10.1088/1674-1056/abea8b
    Abstract ( 351 )   HTML ( 0 )   PDF (1009KB) ( 66 )  
    Optoelectronic properties of MoSe2 are modulated by controlled annealing in air. Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects. Considerable increase in electron and hole mobilities reveals the highly improved electron and hole transport. Furthermore, the photocurrent is enhanced by nearly four orders of magnitudes under 7 nW laser exposure after annealing. The remarkable enhancement in the photoresponse is attributed to an increase in hole trapping centers and a reduction in resistance. Furthermore, the annealed photodetector shows a fast time response on the order of 10 ms and responsivity of 3×104 A/W.
    SPECIAL TOPIC—Optical field manipulation
    Polarized photoluminescence spectroscopy in WS2, WSe2 atomic layers and heterostructures by cylindrical vector beams
    Lijun Wu(吴莉君), Cuihuan Ge(葛翠环), Kai Braun, Mai He(贺迈), Siman Liu(刘思嫚), Qingjun Tong(童庆军), Xiao Wang(王笑), and Anlian Pan(潘安练)
    Chin. Phys. B, 2021, 30 (8):  087802.  DOI: 10.1088/1674-1056/abf3b6
    Abstract ( 563 )   HTML ( 16 )   PDF (1566KB) ( 199 )  
    Due to the large exciton binding energy, two-dimensional (2D) transition metal dichalcogenides (TMDCs) provide an ideal platform for studying excitonic states and related photonics and optoelectronics. Polarization states lead to distinct light-matter interactions which are of great importance for device applications. In this work, we study polarized photoluminescence spectra from intralayer exciton and indirect exciton in WS2 and WSe2 atomic layers, and interlayer exciton in WS2/WSe2 heterostructures by radially and azimuthally polarized cylindrical vector laser beams. We demonstrated the same in-plane and out-of-plane polarization behavior from the intralayer and indirect exciton. Moreover, with these two laser modes, we obtained interlayer exciton in WS2/WSe2 heterostructures with stronger out-of-plane polarization, due to the formation of vertical electric dipole moment.
    Phase-field study of spinodal decomposition under effect of grain boundary
    Ying-Yuan Deng(邓英远), Can Guo(郭灿), Jin-Cheng Wang(王锦程), Qian Liu(刘倩), Yu-Ping Zhao(赵玉平), and Qing Yang(杨卿)
    Chin. Phys. B, 2021, 30 (8):  088101.  DOI: 10.1088/1674-1056/abea9b
    Abstract ( 325 )   HTML ( 0 )   PDF (1523KB) ( 90 )  
    Grain boundary directed spinodal decomposition has a substantial effect on the microstructure evolution and properties of polycrystalline alloys. The morphological selection mechanism of spinodal decomposition at grain boundaries is a major challenge to reveal, and remains elusive so far. In this work, the effect of grain boundaries on spinodal decomposition is investigated by using the phase-field model. The simulation results indicate that the spinodal morphology at the grain boundary is anisotropic bicontinuous microstructures different from the isotropic continuous microstructures of spinodal decomposition in the bulk phase. Moreover, at grain boundaries with higher energy, the decomposed phases are alternating α/β layers that are parallel to the grain boundary. On the contrary, alternating α/β layers are perpendicular to the grain boundary.
    In situ formed FeS2@CoS cathode for long cycling life lithium-ion battery
    Xin Wang(王鑫), Bojun Wang(汪博筠), Jiachao Yang(杨家超), Qiwen Ran(冉淇文), Jian Zou(邹剑), Pengyu Chen(陈鹏宇), Li Li(李莉), Liping Wang(王丽平), and Xiaobin Niu(牛晓滨)
    Chin. Phys. B, 2021, 30 (8):  088201.  DOI: 10.1088/1674-1056/abe9ab
    Abstract ( 433 )   HTML ( 0 )   PDF (2976KB) ( 148 )  
    Pyrite FeS2 exhibits an ultrahigh energy density (1671 W·h·kg-1, for the reaction of FeS2+4Li=Fe+2Li2S) in secondary lithium-ion batteries, but its poor cycling stability, huge volume expansion, the shuttle effect of polysulfides, and slow kinetic properties limit its practical application. In this work, we synthesize a composite structure material CoS on FeS2 surface (FeSx@CoS, 1 < x ≤ 2) by using a cobalt-containing MOF to improve its cycle stability. It is found that CoS inhibits the side reactions and adsorbs polysulfides. As a result, the modified FeS2 shows a higher discharge capacity of 577 mA·h·g-1 (919 W·h·kg-1) after 60 cycles than 484 mA·h·g-1 (778 W·h·kg-1) of bare pyrite FeS2. This efficient strategy provides a valuable step toward the realization of high cycling stability FeS2 cathode materials for secondary lithium-ion batteries and enriches the basic understanding of the influence of FeS2 interfacial stability on its electrochemical performances.
    Shortcut-based quantum gates on superconducting qubits in circuit QED
    Zheng-Yin Zhao(赵正印), Run-Ying Yan(闫润瑛), and Zhi-Bo Feng(冯志波)
    Chin. Phys. B, 2021, 30 (8):  088501.  DOI: 10.1088/1674-1056/abea96
    Abstract ( 410 )   HTML ( 0 )   PDF (985KB) ( 36 )  
    Construction of optimal gate operations is significant for quantum computation. Here an efficient scheme is proposed for performing shortcut-based quantum gates on superconducting qubits in circuit quantum electrodynamics (QED). Two four-level artificial atoms of Cooper-pair box circuits, having sufficient level anharmonicity, are placed in a common quantized field of circuit QED and are driven by individual classical microwaves. Without the effect of cross resonance, one-qubit NOT gate and phase gate in a decoupled atom can be implemented using the invariant-based shortcuts to adiabaticity. With the assistance of cavity bus, a one-step SWAP gate can be obtained within a composite qubit-photon-qubit system by inversely engineering the classical drivings. We further consider the gate realizations by adjusting the microwave fields. With the accessible decoherence rates, the shortcut-based gates have high fidelities. The present strategy could offer a promising route towards fast and robust quantum computation with superconducting circuits experimentally.
    Large-area fabrication: The next target of perovskite light-emitting diodes
    Hang Su(苏杭), Kun Zhu(朱坤), Jing Qin(钦敬), Mengyao Li(李梦瑶), Yulin Zuo(左郁琳), Yunzheng Wang(王允正), Yinggang Wu(吴迎港), Jiawei Cao(曹佳维), and Guolong Li(李国龙)
    Chin. Phys. B, 2021, 30 (8):  088502.  DOI: 10.1088/1674-1056/ac05a4
    Abstract ( 419 )   HTML ( 3 )   PDF (8494KB) ( 240 )  
    Perovskite materials show exciting potential for light-emitting diodes (LEDs) owing to their intrinsically high photoluminescence efficiency and color purity. The research focusing on perovskite light-emitting diodes (PeLEDs) has experienced an exponential growth in the past six years. The maximum external quantum efficiency of red, green, and blue PeLEDs has surpassed 20%, 20%, and 10%, respectively. Nevertheless, the current PeLEDs are still in the laboratory stage, and the key for further development of PeLEDs is large-area fabrication. In this paper, we briefly discuss the similarities and differences between manufacturing high-quality and large-area PeLEDs and perovskite solar cells. Especially, the general technologies for fabricating large-area perovskite films are also introduced. The effect of charge transport layers and electrodes on large-area devices are discussed as well. Most importantly, we summarize the advances of large-area (active area ≥ 30 mm2) PeLEDs reported since 2017, and describe the methods for optimizing large-area PeLEDs reported in the literature. Finally, the development perspective of PeLEDs is presented for the goal of highly efficient and large-area PeLED fabrication. It is of great significance for the application of PeLEDs in future display and lighting.
    SPECIAL TOPIC—Optical field manipulation
    Anisotropic photoresponse of layered rhenium disulfide synaptic transistors
    Chunhua An(安春华), Zhihao Xu(徐志昊), Jing Zhang(张璟), Enxiu Wu(武恩秀), Xinli Ma(马新莉), Yidi Pang(庞奕荻), Xiao Fu(付晓), Xiaodong Hu(胡晓东), Dong Sun(孙栋), Jinshui Miao(苗金水), and Jing Liu(刘晶)
    Chin. Phys. B, 2021, 30 (8):  088503.  DOI: 10.1088/1674-1056/abff26
    Abstract ( 396 )   HTML ( 0 )   PDF (1329KB) ( 147 )  
    Layered ReS2 with direct bandgap and strong in-plane anisotropy shows great potential to develop high-performance angle-resolved photodetectors and optoelectronic devices. However, systematic characterizations of the angle-dependent photoresponse of ReS2 are still very limited. Here, we studied the anisotropic photoresponse of layered ReS2 phototransistors in depth. Angel-resolved Raman spectrum and field-effect mobility are tested to confirm the inconsistency between its electrical and optical anisotropies, which are along 120° and 90°, respectively. We further measured the angle-resolved photoresponse of a ReS2 transistor with 6 diagonally paired electrodes. The maximum photoresponsivity exceeds 0.515 A·W-1 along b-axis, which is around 3.8 times larger than that along the direction perpendicular to b axis, which is consistent with the optical anisotropic directions. The incident wavelength- and power-dependent photoresponse measurement along two anisotropic axes further demonstrates that b axis has stronger light-ReS2 interaction, which explains the anisotropic photoresponse. We also observed angle-dependent photoresistive switching behavior of the ReS2 transistor, which leads to the formation of angle-resolved phototransistor memory. It has simplified structure to create dynamic optoelectronic resistive random access memory controlled spatially through polarized light. This capability has great potential for real-time pattern recognition and photoconfiguration of artificial neural networks (ANN) in a wide spectral range of sensitivity provided by polarized light.
    Tunable inhibition of β-amyloid peptides by fast green molecules
    Tiantian Yang(杨甜甜), Tianxiang Yu(俞天翔), Wenhui Zhao(赵文辉), and Dongdong Lin(林冬冬)
    Chin. Phys. B, 2021, 30 (8):  088701.  DOI: 10.1088/1674-1056/ac0690
    Abstract ( 400 )   HTML ( 3 )   PDF (2818KB) ( 158 )  
    The aggregation of β-amyloid (Aβ) protein into toxic intermediates and mature fibrils is considered to be one of the main causes of Alzheimer's disease (AD). Small molecules as one of blockers are expected to be the potential drug treatment for the disease. However, the nucleation process in molecular assembly is less informative in the literatures. In this work, the formation of Aβ (16-22) peptides was investigated with the presence of small molecule of fast green (FG) at the initial aggregation stage. The results exhibited the tunable inhibitory ability of FG molecules on Aβ (16-22) peptides. Atomic force microscopy (AFM) demonstrated that the inhibitory effect would be dependent on the dose of FG molecules, which could delay the lag time (nucleation) and form single layer conjugates. Spectral measurements further showed that the β-sheet secondary structure of Aβ (16-22) reduced dramatically after the presence of FG molecules. Instead, non-β-sheet nanosheets were formed when the FG/Aβ (16-22) ratio reached 1:1. In addition, the cytotoxicity of aggregates reduced greatly with the presence of FG molecules compared with the Aβ (16-22) fibrils. Overall, this study provided a method for suppressing the toxic amyloid aggregates by FG molecules efficiently, and also showed a strategy for fabrication of two-dimensional materials by small molecules.
    Role of graphene in improving catalytic behaviors of AuNPs/MoS2/Gr/Ni-F structure in hydrogen evolution reaction
    Xian-Wu Xiu(修显武), Wen-Cheng Zhang(张文程), Shu-Ting Hou(侯淑婷), Zhen Li(李振), Feng-Cai Lei(雷风采), Shi-Cai Xu(许士才), Chong-Hui Li(李崇辉), Bao-Yuan Man(满宝元), Jing Yu(郁菁), and Chao Zhang(张超)
    Chin. Phys. B, 2021, 30 (8):  088801.  DOI: 10.1088/1674-1056/abea88
    Abstract ( 480 )   HTML ( 0 )   PDF (3384KB) ( 72 )  
    The efficient production of hydrogen through electrocatalytic decomposition of water has broad prospects in modern energy equipment. However, the catalytic efficiency and durability of hydrogen evolution catalyst are still very deficient, which need to be further explored. Here in this work, we prove that introducing a graphene layer (Gr) between the molybdenum disulfide and nickel foam (Ni-F) substrate can greatly improve the catalytic performance of the hybrid. Owing to the excitation of local surface plasmon resonance (LSPR) of gold nanoparticles (NPs), the electrocatalytic hydrogen releasing activity of the MoS2/Gr/Ni-F heterostructure is greatly improved. This results in a significant increase in the current density of AuNPs/MoS2/Gr/Ni-F composite material under light irradiation and in the dark at 0.2 V (versus reversible hydrogen electrode (RHE)), which is much better than in MoS2/Gr/Ni-F composite materials. The enhancement of hydrogen release can be attributed to the injection of hot electrons into MoS2/Gr/Ni-F by AuNPs, which will improve the electron density of MoS2/Gr/Ni-F, promote the reduction of H2O, and further reduce the activation energy of the electrocatalyst hydrogen evolution reaction (HER). We also prove that the introduction of graphene can improve its stability in acidic catalytic environments. This work provides a new way of designing efficient water splitting system.
    Serverless distributed learning for smart grid analytics
    Gang Huang(黄刚), Chao Wu(吴超), Yifan Hu(胡一帆), and Chuangxin Guo(郭创新)
    Chin. Phys. B, 2021, 30 (8):  088802.  DOI: 10.1088/1674-1056/abe232
    Abstract ( 448 )   HTML ( 3 )   PDF (10439KB) ( 76 )  
    The digitization, informatization, and intelligentization of physical systems require strong support from big data analysis. However, due to restrictions on data security and privacy and concerns about the cost of big data collection, transmission, and storage, it is difficult to do data aggregation in real-world power systems, which directly retards the effective implementation of smart grid analytics. Federated learning, an advanced distributed learning method proposed by Google, seems a promising solution to the above issues. Nevertheless, it relies on a server node to complete model aggregation and the framework is limited to scenarios where data are independent and identically distributed. Thus, we here propose a serverless distributed learning platform based on blockchain to solve the above two issues. In the proposed platform, the task of machine learning is performed according to smart contracts, and encrypted models are aggregated via a mechanism of knowledge distillation. Through this proposed method, a server node is no longer required and the learning ability is no longer limited to independent and identically distributed scenarios. Experiments on a public electrical grid dataset will verify the effectiveness of the proposed approach.
    Stabilization of formamidinium lead iodide perovskite precursor solution for blade-coating efficient carbon electrode perovskite solar cells Hot!
    Yu Zhan(占宇), Weijie Chen(陈炜杰), Fu Yang(杨甫), and Yaowen Li(李耀文)
    Chin. Phys. B, 2021, 30 (8):  088803.  DOI: 10.1088/1674-1056/abfbcb
    Abstract ( 644 )   HTML ( 3 )   PDF (4217KB) ( 387 )  
    Formamidinium lead triiodide (FAPbI3) is a research hotspot in perovskite photovoltaics due to its broad light absorption and proper thermal stability. However, quite a few researches focused on the stability of the FAPbI3 perovskite precursor solutions. Besides, the most efficient FAPbI3 layers are prepared by the spin-coating method, which is limited to the size of the device. Herein, the stability of FAPbI3 perovskite solution with methylammonium chloride (MACl) or cesium chloride (CsCl) additive is studied for preparing perovskite film through an upscalable blade-coating method. Each additive works well for achieving a high-quality FAPbI3 film, resulting in efficient carbon electrode perovskite solar cells (pero-SCs) in the ambient condition. However, the perovskite solution with MACl additive shows poor aging stability that no α-FAPbI3 phase is observed when the solution is aged over one week. While the perovskite solution with CsCl additive shows promising aging stability that it still forms high-quality pure α-FAPbI3 perovskite film even the solution is aged over one month. During the solution aging process, the MACl could be decomposed into methylamine which will form some unfavored intermediated phase inducing δ-phase FAPbI3. Whereas, replacing MACl with CsCl could effectively solve this issue. Our founding shows that there is a great need to develop a non-MACl FAPbI3 perovskite precursor solution for cost-effective preparation of pero-SCs.
    LCH: A local clustering H-index centrality measure for identifying and ranking influential nodes in complex networks
    Gui-Qiong Xu(徐桂琼), Lei Meng(孟蕾), Deng-Qin Tu(涂登琴), and Ping-Le Yang(杨平乐)
    Chin. Phys. B, 2021, 30 (8):  088901.  DOI: 10.1088/1674-1056/abea86
    Abstract ( 503 )   HTML ( 12 )   PDF (1655KB) ( 108 )  
    Identifying influential nodes in complex networks is one of the most significant and challenging issues, which may contribute to optimizing the network structure, controlling the process of epidemic spreading and accelerating information diffusion. The node importance ranking measures based on global information are not suitable for large-scale networks due to their high computational complexity. Moreover, they do not take into account the impact of network topology evolution over time, resulting in limitations in some applications. Based on local information of networks, a local clustering H-index (LCH) centrality measure is proposed, which considers neighborhood topology, the quantity and quality of neighbor nodes simultaneously. The proposed measure only needs the information of first-order and second-order neighbor nodes of networks, thus it has nearly linear time complexity and can be applicable to large-scale networks. In order to test the proposed measure, we adopt the susceptible-infected-recovered (SIR) and susceptible-infected (SI) models to simulate the spreading process. A series of experimental results on eight real-world networks illustrate that the proposed LCH can identify and rank influential nodes more accurately than several classical and state-of-the-art measures.
    Detection of influential nodes with multi-scale information
    Jing-En Wang(王静恩), San-Yang Liu(刘三阳), Ahmed Aljmiai, and Yi-Guang Bai(白艺光)
    Chin. Phys. B, 2021, 30 (8):  088902.  DOI: 10.1088/1674-1056/abff2d
    Abstract ( 524 )   HTML ( 25 )   PDF (17476KB) ( 434 )  
    The identification of influential nodes in complex networks is one of the most exciting topics in network science. The latest work successfully compares each node using local connectivity and weak tie theory from a new perspective. We study the structural properties of networks in depth and extend this successful node evaluation from single-scale to multi-scale. In particular, one novel position parameter based on node transmission efficiency is proposed, which mainly depends on the shortest distances from target nodes to high-degree nodes. In this regard, the novel multi-scale information importance (MSII) method is proposed to better identify the crucial nodes by combining the network's local connectivity and global position information. In simulation comparisons, five state-of-the-art algorithms, i.e. the neighbor nodes degree algorithm (NND), betweenness centrality, closeness centrality, Katz centrality and the k-shell decomposition method, are selected to compare with our MSII. The results demonstrate that our method obtains superior performance in terms of robustness and spreading propagation for both real-world and artificial networks.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 30, No. 8

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