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Table of contents

    13 October 2021, Volume 30 Issue 11 Previous issue    Next issue
    GENERAL
    Numerical investigation on threading dislocation bending with InAs/GaAs quantum dots
    Guo-Feng Wu(武国峰), Jun Wang(王俊), Wei-Rong Chen(陈维荣), Li-Na Zhu(祝丽娜), Yuan-Qing Yang(杨苑青), Jia-Chen Li(李家琛), Chun-Yang Xiao(肖春阳), Yong-Qing Huang(黄永清), Xiao-Min Ren(任晓敏), Hai-Ming Ji(季海铭), and Shuai Luo(罗帅)
    Chin. Phys. B, 2021, 30 (11):  110201.  DOI: 10.1088/1674-1056/abfd9f
    Abstract ( 471 )   HTML ( 2 )   PDF (570KB) ( 87 )  
    The threading dislocations (TDs) in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon. The insertion of InAs quantum dots (QDs) acting as dislocation filters is a pretty good alternative to solving this problem. In this paper, a finite element method (FEM) is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations (MDs). Making a comparison of elastic strain energy between the two isolated systems, a reasonable result is obtained. The effect of the cap layer thickness and the base width of QDs on TD bending are studied, and the results show that the bending area ratio of single QD (the bending area divided by the area of the QD base) is evidently affected by the two factors. Moreover, we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs. For the QD with 24-nm base width and 5-nm cap layer thickness, taking the QD density of 1011 cm-2 into account, the bending area ratio of single-layer QDs (the area of bending TD divided by the area of QD layer) is about 38.71%. With inserting five-layer InAs QDs, the TD density decreases by 91.35%. The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.
    Analysis of the rogue waves in the blood based on the high-order NLS equations with variable coefficients
    Ying Yang(杨颖), Yu-Xiao Gao(高玉晓), and Hong-Wei Yang(杨红卫)
    Chin. Phys. B, 2021, 30 (11):  110202.  DOI: 10.1088/1674-1056/abff31
    Abstract ( 534 )   HTML ( 0 )   PDF (1539KB) ( 135 )  
    The research of rogue waves is an advanced field which has important practical and theoretical significances in mathematics, physics, biological fluid mechanics, oceanography, etc. Using the reductive perturbation theory and long wave approximation, the equations governing the movement of blood vessel walls and the flow of blood are transformed into high-order nonlinear Schrödinger (NLS) equations with variable coefficients. The third-order nonlinear Schrödinger equation is degenerated into a completely integrable Sasa-Satsuma equation (SSE) whose solutions can be used to approximately simulate the real rogue waves in the vessels. For the first time, we discuss the conditions for generating rogue waves in the blood vessels and effects of some physiological parameters on the rogue waves. Based on the traveling wave solutions of the fourth-order nonlinear Schrödinger equation, we analyze the effects of the higher order terms and the initial deformations of the blood vessel on the wave propagation and the displacement of the tube wall. Our results reveal that the amplitude of the rogue waves are proportional to the initial stretching ratio of the tube. The high-order nonlinear and dispersion terms lead to the distortion of the wave, while the initial deformation of the tube wall will influence the wave amplitude and wave steepness.
    Connes distance of 2D harmonic oscillators in quantum phase space
    Bing-Sheng Lin(林冰生) and Tai-Hua Heng(衡太骅)
    Chin. Phys. B, 2021, 30 (11):  110203.  DOI: 10.1088/1674-1056/ac0529
    Abstract ( 330 )   HTML ( 0 )   PDF (581KB) ( 315 )  
    We study the Connes distance of quantum states of two-dimensional (2D) harmonic oscillators in phase space. Using the Hilbert-Schmidt operatorial formulation, we construct a boson Fock space and a quantum Hilbert space, and obtain the Dirac operator and a spectral triple corresponding to a four-dimensional (4D) quantum phase space. Based on the ball condition, we obtain some constraint relations about the optimal elements. We construct the corresponding optimal elements and then derive the Connes distance between two arbitrary Fock states of 2D quantum harmonic oscillators. We prove that these two-dimensional distances satisfy the Pythagoras theorem. These results are significant for the study of geometric structures of noncommutative spaces, and it can also help us to study the physical properties of quantum systems in some kinds of noncommutative spaces.
    Effect of external electric field on the terahertz transmission characteristics of electrolyte solutions
    Jia-Hui Wang(王佳慧), Guo-Yang Wang(王国阳), Xin Liu(刘欣), Si-Yu Shao(邵思雨), Hai-Yun Huang(黄海云), Chen-Xin Ding(丁晨鑫), Bo Su(苏波), and Cun-Lin Zhang(张存林)
    Chin. Phys. B, 2021, 30 (11):  110204.  DOI: 10.1088/1674-1056/abff24
    Abstract ( 392 )   HTML ( 1 )   PDF (1563KB) ( 131 )  
    We fabricated a microfluidic chip with simple structure and good sealing performance, and studied the influence of the electric field on THz absorption intensity of liquid samples treated at different times by using THz time domain spectroscopy system. The tested liquids were deionised water and CuSO4, CuCl2, NaHCO3, Na2CO3 and NaCl solutions. The transmission intensity of the THz wave increases as the standing time of the electrolyte solution in the electric field increases. The applied electric field alters the dipole moment of water molecules in the electrolyte solution, which affects the vibration and rotation of the whole water molecules, breaks the hydrogen bonds in the water, increases the number of single water molecules and leads to the enhancement of the THz transmission spectrum.
    Classical-field description of Bose-Einstein condensation of parallel light in a nonlinear optical cavity
    Hui-Fang Wang(王慧芳), Jin-Jun Zhang(张进军), and Jian-Jun Zhang(张建军)
    Chin. Phys. B, 2021, 30 (11):  110301.  DOI: 10.1088/1674-1056/abf4f9
    Abstract ( 399 )   HTML ( 0 )   PDF (972KB) ( 89 )  
    We study the Bose-Einstein condensation of parallel light in a two-dimensional nonlinear optical cavity, where the massive photons are converted into photon molecules (p-molecules). We extend the classical-field method to provide a description of the two-component system, and we also derive a coupled density equation which can be used to describe the conversion relation between photons and p-molecules. Furthermore, we obtain the chemical potential of the system, and we also find that the system can transform from the mixed photon and p-molecule condensate phase into a pure p-molecule condensate phase. Additionally, we investigate the collective excitation of the system. We also discuss the problem how the spontaneous decay of an atom is influenced by both the phase transition and collective excitation of the coupling system.
    Dense coding capacity in correlated noisy channels with weak measurement
    Jin-Kai Li(李进开), Kai Xu(徐凯), and Guo-Feng Zhang(张国锋)
    Chin. Phys. B, 2021, 30 (11):  110302.  DOI: 10.1088/1674-1056/abf34f
    Abstract ( 406 )   HTML ( 0 )   PDF (1373KB) ( 45 )  
    Capacity of dense coding via correlated noisy channel is greater than that via uncorrelated noisy channel. It is shown that the weak measurement and reversal measurement need to further improve their quantum dense coding capacity in correlated amplitude damping channel, but this improvement is very small in correlated phase damping channel and correlated depolarizing channel.
    Reference-frame-independent quantum key distribution of wavelength division multiplexing with multiple quantum channels
    Zhongqi Sun(孙钟齐), Yanxin Han(韩雁鑫), Tianqi Dou(窦天琦), Jipeng Wang(王吉鹏), Zhenhua Li(李振华), Fen Zhou(周芬), Yuqing Huang(黄雨晴), and Haiqiang Ma(马海强)
    Chin. Phys. B, 2021, 30 (11):  110303.  DOI: 10.1088/1674-1056/abf350
    Abstract ( 478 )   HTML ( 6 )   PDF (539KB) ( 144 )  
    Reference-frame-independent quantum key distribution (RFI-QKD) can allow a quantum key distribution system to obtain the ideal key rate and transmission distance without reference system calibration, which has attracted much attention. Here, we propose an RFI-QKD protocol based on wavelength division multiplexing (WDM) considering finite-key analysis and crosstalk. The finite-key bound for RFI-QKD with decoy states is derived under the crosstalk of WDM. The resulting secret key rate of RFI-QKD, which is more rigorous, is obtained. Simulation results reveal that the secret key rate of RFI-QKD based on WDM is affected by the multiplexing channel number, as well as crosstalk between adjacent channels.
    Probability density and oscillating period of magnetopolaron in parabolic quantum dot in the presence of Rashba effect and temperature
    Ying-Jie Chen(陈英杰) and Feng-Lan Shao(邵凤兰)
    Chin. Phys. B, 2021, 30 (11):  110304.  DOI: 10.1088/1674-1056/abfa0b
    Abstract ( 335 )   HTML ( 2 )   PDF (5154KB) ( 60 )  
    We study the property of magnetopolaron in a parabolic quantum dot under the Rashba spin-orbit interaction (RSOI) by adopting an unitary transformation of Lee-Low-Pines type and the variational method of Pekar type with and without considering the temperature. The temporal spatial distribution of the probability density and the relationships of the oscillating period with the RSOI constant, confinement constant, electron-phonon coupling strength, phonon wave vector and temperature are discussed. The results show that the probability density of the magnetopolaron in the superposition of the ground and first excited state takes periodic oscillation (T0/period) in the presence or absence of temperature. Because of the RSOI, the oscillating period is divided into different branches. Also, the results indicate that the oscillating period increases (decreases) when the RSOI constant, electron-phonon coupling strength and phonon wave vector (the confinement constant) increase in a proper temperature, and the temperature plays a significant role in determining the properties of the polaron.
    Hardware for multi-superconducting qubit control and readout
    Zhan Wang(王战), Hai Yu(于海), Rongli Liu(刘荣利), Xiao Ma(马骁), Xueyi Guo(郭学仪), Zhongcheng Xiang(相忠诚), Pengtao Song(宋鹏涛), Luhong Su(苏鹭红), Yirong Jin(金贻荣), and Dongning Zheng(郑东宁)
    Chin. Phys. B, 2021, 30 (11):  110305.  DOI: 10.1088/1674-1056/ac0425
    Abstract ( 535 )   HTML ( 4 )   PDF (6663KB) ( 346 )  
    We have developed an electronic hardware system for the control and readout of multi-superconducting qubit devices. The hardware system is based on the design ideas of good scalability, high synchronization and low latency. The system, housed inside a VPX-6U chassis, includes multiple arbitrary-waveform generator (AWG) channels, analog-digital-converter (ADC) channels as well as direct current source channels. The system can be used for the control and readout of up to twelve superconducting transmon qubits in one chassis, and control and readout of more and more qubit can be carried out by interconnecting the chassis. By using field programmable gate array (FPGA) processors, the system incorporates three features that are specifically useful for superconducting qubit research. Firstly, qubit signals can be processed using the on-board FPGA after being acquired by ADCs, significantly reducing data processing time and data amount for storage and transmission. Secondly, different output modes, such as direct output and sequential output modes, of AWG can be implemented with pre-encoded FPGA. Thirdly, with data acquisition ADCs and control AWGs jointly controlled by the same FPGA, the feedback latency can be reduced, and in our test a 178.4 ns latency time is realized. This is very useful for future quantum feedback experiments. Finally, we demonstrate the functionality of the system by applying the system to the control and readout of a 10 qubit superconducting quantum processor.
    One-dimensional atom laser in microgravity
    Yi Qin(秦毅), Xiaoyang Shen(沈晓阳), and Lin Xia(夏林)
    Chin. Phys. B, 2021, 30 (11):  110306.  DOI: 10.1088/1674-1056/abff25
    Abstract ( 333 )   HTML ( 0 )   PDF (531KB) ( 109 )  
    Using coupled Gross-Pitaevksii (GP) equations, we simulate the output of one-dimensional pulsed atom laser in space station. We get two atom laser pulses propagating in opposite directions with one pulsed RF coupling. Compared with atom laser under gravity, the laser pulse in microgravity shows much slower moving speed, which is suitable to be used for long-term investigations. We also simulate the output flux at different coupling strengths.
    Supersymmetric structures of Dirac oscillators in commutative and noncommutative spaces
    Jing-Ying Wei(魏静莹), Qing Wang(王青), and Jian Jing(荆坚)
    Chin. Phys. B, 2021, 30 (11):  110307.  DOI: 10.1088/1674-1056/ac05ab
    Abstract ( 332 )   HTML ( 0 )   PDF (443KB) ( 54 )  
    The supersymmetric properties of a charged planar Dirac oscillator coupling to a uniform perpendicular magnetic field are studied. We find that there is an N=2 supersymmetric structure in both commutative and noncommutative cases. We construct the generators of the supersymmetric algebras explicitly and show that the generators of the supersymmetric algebras can be mapped onto ones which only contain the left or right-handed chiral phonons by unitary transformations.
    RAPID COMMUNICATION
    Photoinduced Weyl semimetal phase and anomalous Hall effect in a three-dimensional topological insulator
    Meng-Nan Chen(陈梦南) and Wen-Chao Chen(陈文潮)
    Chin. Phys. B, 2021, 30 (11):  110308.  DOI: 10.1088/1674-1056/abff29
    Abstract ( 497 )   HTML ( 1 )   PDF (1186KB) ( 168 )  
    Motivated by the fact that Weyl fermions can emerge in a three-dimensional topological insulator on breaking either time-reversal or inversion symmetries, we propose that a topological quantum phase transition to a Weyl semimetal phase occurs under the off-resonant circularly polarized light, in a three-dimensional topological insulator, when the intensity of the incident light exceeds a critical value. The circularly polarized light effectively generates a Zeeman exchange field and a renormalized Dirac mass, which are highly controllable. The phase transition can be exactly characterized by the first Chern number. A tunable anomalous Hall conductivity emerges, which is fully determined by the location of the Weyl nodes in momentum space, even in the doping regime. Our predictions are experimentally realizable through pump-probe angle-resolved photoemission spectroscopy and raise a new way for realizing Weyl semimetals and quantum anomalous Hall effects.
    GENERAL
    Quantum exceptional points of non-Hermitian Hamiltonian and Liouvillian in dissipative quantum Rabi model
    Xianfeng Ou(欧先锋), Jiahao Huang(黄嘉豪), and Chaohong Lee(李朝红)
    Chin. Phys. B, 2021, 30 (11):  110309.  DOI: 10.1088/1674-1056/ac0349
    Abstract ( 416 )   HTML ( 1 )   PDF (3100KB) ( 219 )  
    The open quantum system can be described by either a Lindblad master equation or a non-Hermitian Hamiltonian (NHH). However, these two descriptions usually have different exceptional points (EPs), associated with the degeneracies in the open quantum system. Here, considering a dissipative quantum Rabi model, we study the spectral features of EPs in these two descriptions and explore their connections. We find that, although the EPs in these two descriptions are usually different, the EPs of NHH will be consistent with the EPs of master equation in the weak coupling regime. Further, we find that the quantum Fisher information (QFI), which measures the statistical distance between quantum states, can be used as a signature for the appearance of EPs. Our study may give a theoretical guidance for exploring the properties of EPs in open quantum systems.
    Effects of classical random external field on the dynamics of entanglement in a four-qubit system
    Edwige Carole Fosso, Fridolin Tchangnwa Nya, Lionel Tenemeza Kenfack, and Martin Tchoffo
    Chin. Phys. B, 2021, 30 (11):  110310.  DOI: 10.1088/1674-1056/ac0bab
    Abstract ( 294 )   HTML ( 0 )   PDF (2957KB) ( 39 )  
    We investigate the dynamics of entanglement through negativity and witness operators in a system of four non-interacting qubits driven by a classical phase noisy laser characterized by a classical random external field (CREF). The qubits are initially prepared in the GHZ-type and W-type states and interact with the CREF in two different qubit-field configurations, namely, common environment and independent environments in which the cases of equal and different field phase probabilities are distinguished. We find that entanglement exhibits different decaying behavior, depending on the input states of the qubits, the qubit-field coupling configuration, and field phase probabilities. On the one hand, we demonstrate that the coupling of the qubits in a common environment is an alternative and more efficient strategy to completely shield the system from the detrimental impacts of the decoherence process induced by a CREF, independent of the input state and the field phase probabilities considered. Also, we show that GHZ-type states have strong dynamics under CREF as compared to W-type states. On the other hand, we demonstrate that in the model investigated the system robustness's can be greatly improved by increasing the number of qubits constituting the system.
    Nearly invariant boundary entanglement in optomechanical systems
    Shi-Wei Cui(崔世威), Zhi-Jiao Deng(邓志姣), Chun-Wang Wu(吴春旺), and Qing-Xia Meng(孟庆霞)
    Chin. Phys. B, 2021, 30 (11):  110311.  DOI: 10.1088/1674-1056/ac16ca
    Abstract ( 433 )   HTML ( 0 )   PDF (599KB) ( 63 )  
    In order to understand our previous numerical finding that steady-state entanglement along the instability boundary remains unchanged in a three-mode optomechanical system [Phys. Rev. A 101 023838 (2020)], we investigate in detail the boundary entanglement in a simpler two-mode optomechanical system. Studies show that both the mechanism to generate entanglement and the parameter dependence of boundary entanglement are quite similar in these two models. Therefore, the two-mode system has captured the main features in the three-mode system. With the help of analytical calculations and discussing in a much bigger parameter interval, we find that the unchanging behavior previously discovered is actually an extremely slow changing behavior of the boundary entanglement function, and most importantly, this nearly invariant boundary entanglement is a general phenomenon via parametric down conversion process in the weak dissipation regime. This is by itself interesting as threshold quantum signatures in optomechanical phonon lasers, or may have potential value in related applications based on boundary quantum properties.
    Adjustable half-skyrmion chains induced by SU(3) spin-orbit coupling in rotating Bose-Einstein condensates
    Li Wang(王力), Ji Li(李吉), Xiao-Lin Zhou(周晓林), Xiang-Rong Chen(陈向荣), and Wu-Ming Liu(刘伍明)
    Chin. Phys. B, 2021, 30 (11):  110312.  DOI: 10.1088/1674-1056/abfcc8
    Abstract ( 334 )   HTML ( 2 )   PDF (5958KB) ( 142 )  
    The ground state properties of the rotating Bose-Einstein condensates (BECs) with SU(3) spin-orbit coupling (SOC) in a two-dimensional harmonic trap are studied. The results show that the ferromagnetic and antiferromagnetic systems present three half-skyrmion chains at an angle of 120° to each other along the coupling directions. With the enhancement of isotropic SU(3) SOC strength, the position of the three chains remains unchanged, in which the number of half-skyrmions increases gradually. With the increase of rotation frequency and atomic density-density interaction, the number of half-skyrmions on the three chains and in the regions between two chains increases gradually. The relationships of the total number of half-skyrmions on the three chains with the increase of SU(3) SOC strength, rotation frequency and atomic density-density interaction are also given. In addition, changing the anisotropic SU(3) SOC strength can regulate the number and morphology of the half-skyrmion chains.
    Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion
    Guang-Tai Xue(薛广太), Xiao-Hui Tian(田晓慧), Chi Zhang(张弛), Zhenda Xie(谢臻达), Ping Xu(徐平), Yan-Xiao Gong(龚彦晓), and Shi-Ning Zhu(祝世宁)
    Chin. Phys. B, 2021, 30 (11):  110313.  DOI: 10.1088/1674-1056/ac22a1
    Abstract ( 461 )   HTML ( 0 )   PDF (983KB) ( 122 )  
    We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric down-conversion in the periodically-poled lithium niobate on insulator (LNOI) waveguide. We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum, such as narrowing, broadening, and splitting. We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth. Our study may promote the development of on-chip photon sources in the LNOI platform, as well as opens up a way to engineer photon frequency state.
    A secure image protection algorithm by steganography and encryption using the 2D-TSCC
    Qi Li(李琦), Xingyuan Wang(王兴元), He Wang(王赫), Xiaolin Ye(叶晓林), Shuang Zhou(周双), Suo Gao(高锁), and Yunqing Shi(施云庆)
    Chin. Phys. B, 2021, 30 (11):  110501.  DOI: 10.1088/1674-1056/abfa01
    Abstract ( 432 )   HTML ( 0 )   PDF (30007KB) ( 101 )  
    Based on the two-dimensional (2D) tan-sin-cos-coupling (2D-TSCC), a new image protection method is designed, this method includes steganography and encryption. First, a 2D-TSCC system is designed. The 2D-TSCC has a large parameter space in a hyperchaotic state. The chaotic trajectory fills the entire window. The chaotic sequence generated by the 2D-TSCC has a good pseudorandomness, so it can be used in steganography and encryption. Then, the amount of information contained in each bit of the cover image is analyzed, and the three bits which carry the least amount of information are selected. The secret image is hidden in these three bits base on the 2D-TSCC. Finally, the carrier image is scrambled and diffused by the 2D-TSCC. The ciphertext is generated in this way. Send the ciphertext to the recipient through channel transmission, and the recipient obtains the secret image by decrypting twice.
    A memristive map with coexisting chaos and hyperchaos
    Sixiao Kong(孔思晓), Chunbiao Li(李春彪), Shaobo He(贺少波), Serdar Çiçek, and Qiang Lai(赖强)
    Chin. Phys. B, 2021, 30 (11):  110502.  DOI: 10.1088/1674-1056/abf4fb
    Abstract ( 439 )   HTML ( 1 )   PDF (8280KB) ( 149 )  
    By introducing a discrete memristor and periodic sinusoidal functions, a two-dimensional map with coexisting chaos and hyperchaos is constructed. Various coexisting chaotic and hyperchaotic attractors under different Lyapunov exponents are firstly found in this discrete map, along with which other regimes of coexistence such as coexisting chaos, quasi-periodic oscillation, and discrete periodic points are also captured. The hyperchaotic attractors can be flexibly controlled to be unipolar or bipolar by newly embedded constants meanwhile the amplitude can also be controlled in combination with those coexisting attractors. Based on the nonlinear auto-regressive model with exogenous inputs (NARX) for neural network, the dynamics of the memristive map is well predicted, which provides a potential passage in artificial intelligence-based applications.
    Physical generation of random numbers using an asymmetrical Boolean network
    Hai-Fang Liu(刘海芳), Yun-Cai Wang(王云才), Lu-Xiao Sang(桑鲁骁), and Jian-Guo Zhang(张建国)
    Chin. Phys. B, 2021, 30 (11):  110503.  DOI: 10.1088/1674-1056/abf4fc
    Abstract ( 393 )   HTML ( 0 )   PDF (8987KB) ( 52 )  
    Autonomous Boolean networks (ABNs) have been successfully applied to the generation of random number due to their complex nonlinear dynamics and convenient on-chip integration. Most of the ABNs used for random number generators show a symmetric topology, despite their oscillations dependent on the inconsistency of time delays along links. To address this issue, we suggest an asymmetrical autonomous Boolean network (aABN) and show numerically that it provides large amplitude oscillations by using equal time delays along links and the same logical gates. Experimental results show that the chaotic features of aABN are comparable to those of symmetric ABNs despite their being made of fewer nodes. Finally, we put forward a random number generator based on aABN and show that it generates the random numbers passing the NIST test suite at 100 Mbits/s. The unpredictability of the random numbers is analyzed by restarting the random number generator repeatedly. The aABN may replace symmetrical ABNs in many applications using fewer nodes and, in turn, reducing power consumption.
    ATOMIC AND MOLECULAR PHYSICS
    Hyperfine structures and the field effects of IBr molecule in its rovibronic ground state
    Defu Wang(王得富), Xuping Shao(邵旭萍), Yunxia Huang(黄云霞), Chuanliang Li(李传亮), and Xiaohua Yang(杨晓华)
    Chin. Phys. B, 2021, 30 (11):  113301.  DOI: 10.1088/1674-1056/abfc3d
    Abstract ( 448 )   HTML ( 1 )   PDF (577KB) ( 83 )  
    Hyperfine structures and the field effects of IBr molecule in its rovibronic ground state are theoretically studied by diagonalizing the effective Hamiltonian matrix. Perturbations of high-J levels up to 4 are taken into account when studying the hyperfine sub-levels of the J = 0 level, and thus, an 80×80 matrix is constructed and solved. Some of the experimentally absent molecular constants are computed using Dalton program. Our results will be helpful in the experimental investigation of manipulation and further cooling of cold IBr molecules.
    Geometric structure of N2Oq+ (q = 5, 6) studied by Ne8+ ion-induced Coulomb explosion imaging
    Xi Zhao(赵曦), Xu Shan(单旭), Xiaolong Zhu(朱小龙), Lei Chen(陈磊), Zhenjie Shen(沈镇捷), Wentian Feng(冯文天), Dalong Guo(郭大龙), Dongmei Zhao(赵冬梅), Ruitian Zhang(张瑞田), Yong Gao(高永), Zhongkui Huang(黄忠魁), Shaofeng Zhang(张少锋), Xinwen Ma(马新文), and Xiangjun Chen(陈向军)
    Chin. Phys. B, 2021, 30 (11):  113302.  DOI: 10.1088/1674-1056/abff45
    Abstract ( 455 )   HTML ( 0 )   PDF (3156KB) ( 115 )  
    We report the study on the complete three-body Coulomb explosion (CE) of N2Oq+ (q = 5, 6) induced by 56-keV/u Ne8+ ion collision with N2O gaseous molecule. Six CE channels for N2O5+ and seven for N2O6+ are identified by measuring three ionic fragments and the charge-changed projectile in quadruple coincidence. Correspondingly the kinetic energy release (KER) and momentum correlation angle (MCA) distributions of three ionic fragments for each of the CE channels are also deduced. Numerical computation is presented to reconstruct the geometric structure of N2Oq+ prior to dissociation based on the measured KER and MCA. The N-N and N-O bond lengths and the N-N-O bond angles of N2Oq+ for each of the channels are determined.
    TOPICAL REVIEW—Optical field manipulation
    Superchiral fields generated by nanostructures and their applications for chiral sensing
    Huizhen Zhang(张慧珍), Weixuan Zhang(张蔚暄), Saisai Hou(侯赛赛), Rongyao Wang(王荣瑶), and Xiangdong Zhang(张向东)
    Chin. Phys. B, 2021, 30 (11):  113303.  DOI: 10.1088/1674-1056/ac11df
    Abstract ( 423 )   HTML ( 1 )   PDF (7726KB) ( 165 )  
    Chirality is ubiquitous in natural world. Although with similar physical and chemical properties, chiral enantiomers could play different roles in biochemical processes. Discrimination of chiral enantiomers is extremely important in biochemical, analytical chemistry, and pharmaceutical industries. Conventional chiroptical spectroscopic methods are disadvantageous at a limited detection sensitivity because of the weak signals of natural chiral molecules. Recently, superchiral fields were proposed to effectively enhance the interaction between light and molecules, allowing for ultrasensitive chiral detection. Intensive theoretical and experimental works have been devoted to generation of superchiral fields based on artificial nanostructures and their application in ultrasensitive chiral sensing. In this review, we present a survey on these works. We begin with the introduction of chiral properties of electromagnetic fields. Then, the optical chirality enhancement and ultrasensitive chiral detection based on chiral and achiral nanostructures are discussed respectively. Finally, we give a short summary and a perspective for the future ultrasensitive chiral sensing.
    ATOMIC AND MOLECULAR PHYSICS
    Research on the ions' axial temperature of a sympathetically-cooled 113Cd+ ion crystal
    Nong-Chao Xin(辛弄潮), Sheng-Nan Miao(苗胜楠), Hao-Ran Qin(秦浩然), Li-Ming Guo(郭黎明), Ji-Ze Han(韩济泽), Hua-Xing Hu(胡华星), Wen-Xin Shi(施文心), Jian-Wei Zhang(张建伟), and Li-Jun Wang(王力军)
    Chin. Phys. B, 2021, 30 (11):  113701.  DOI: 10.1088/1674-1056/abe379
    Abstract ( 434 )   HTML ( 2 )   PDF (1269KB) ( 61 )  
    Molecular dynamics simulation of a sympathetically-cooled 113Cd+ ion crystal system is achieved. Moreover, the relationship between ions' axial temperature and different electric parameters, including radio frequency voltage and end-cap voltage is depicted. Under stable trapping condition, optimum radio frequency voltage, corresponding to minimum temperature and the highest cooling efficiency, is obtained. The temperature is positively correlated with end-cap voltage. The relationship is also confirmed by a sympathetically-cooled 113Cd+ microwave clock. The pseudo-potential model is used to illustrate the relationship and influence mechanism. A reasonable index, indicating ions' temperature, is proposed to quickly estimate the relative ions' temperature. The investigation is helpful for ion crystal investigation, such as spatial configuration manipulation, sympathetic cooling efficiency enhancement, and temporal evolution.
    ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
    Solar broadband metamaterial perfect absorber based on dielectric resonant structure of Ge cone array and InAs film
    Kuang-Ling Guo(郭匡灵), Hou-Hong Chen(陈厚宏), Xiao-Ming Huang(黄晓明), Tian-Hui Hu(胡天惠), and Hai-Ying Liu(刘海英)
    Chin. Phys. B, 2021, 30 (11):  114201.  DOI: 10.1088/1674-1056/abf91e
    Abstract ( 357 )   HTML ( 0 )   PDF (2425KB) ( 65 )  
    The broadband metamaterial perfect absorber has been extensively studied due to its excellent characteristics and promising application prospect. In this work a solar broadband metamaterial perfect absorber is proposed based on the structure of the germanium (Ge) cone array and the indium arsenide (InAs) dielectric film on the gold (Au) substrate. The results show that the absorption covers the whole ultraviolet-visible and near-infrared range. For the case of A > 99%, the absorption bandwidth reaches up to 1230 nm with a wavelength range varied from 200 nm to 1430 nm. The proposed absorber is able to absorb more than 98.7% of the solar energy in a solar spectrum from 200 nm to 3000 nm. The electromagnetic dipole resonance and the high-order modes of the Ge cone couple strongly to the incident optical field, which introduces a strong coupling with the solar radiation and produces an ultra-broadband absorption. The absorption spectrum can be feasibly manipulated via tuning the structural parameters, and the polarization insensitivity performance is particularly excellent. The proposed absorber can possess wide applications in active photoelectric effects, thermion modulators, and photoelectric detectors.
    A crossed focused vortex beam with application to cold molecules
    Meng Xia(夏梦), Yaling Yin(尹亚玲), Chunying Pei(裴春莹), Yuer Ye(叶玉儿), Ruoxi Gu(顾若溪), Kang Yan(严康), Di Wu(吴迪), Yong Xia(夏勇), and Jianping Yin(印建平)
    Chin. Phys. B, 2021, 30 (11):  114202.  DOI: 10.1088/1674-1056/abf915
    Abstract ( 406 )   HTML ( 2 )   PDF (2243KB) ( 160 )  
    We report the generation of a crossed, focused, optical vortex beam by using a pair of hybrid holograms, which combine the vortex phase and lens phase onto a spatial light modulator. We study the intensity distributions of the vortex beam in free propagation space, and the relationship of its dark spot size with the incident Gaussian beam's waist, the lens's focal length, and its orbital angular momentum. Our results show that the crossed, focused, vortex beam's dark spot size can be as small as 16.3μm and adjustable by the quantum number of the orbital angular momentum, and can be used to increase the density of trapped molecules. Furthermore, we calculate the optical potential of the blue-detuned, crossed vortex beam for MgF molecules. It is applicable to cool and trap neutral molecules by intensity-gradient-induced Sisyphus cooling, as the intensity gradient of such vortex beam is extremely high near the focal point.
    Optomechanical-organized multipulse dynamics in ultrafast fiber laser
    Lin Huang(黄琳), Yu-Sheng Zhang(张裕生), and Yu-Dong Cui(崔玉栋)
    Chin. Phys. B, 2021, 30 (11):  114203.  DOI: 10.1088/1674-1056/abf344
    Abstract ( 440 )   HTML ( 1 )   PDF (1993KB) ( 43 )  
    A novel organized multipulse pattern and its birth dynamics under strong optomechanical effect in microfiber-assisted ultrafast fiber laser are investigated in this work. The background pulses are observed to obviously exhibit selectively amplifying self-organized process of evolving into quasi-stable equidistant clusters. The radio frequency spectrum of the multipulse pattern displays a harmonic mode-locking-like behavior with a repetition rate of 2.0138 GHz, corresponding to the frequency of torsional-radial (TR2m) acoustic mode in microfiber. The results show the evidence of optomechanical effect in dominating the birth dynamics and pattern of multipulse.
    A low noise, high fidelity cross phase modulation in multi-level atomic medium
    Liangwei Wang(王亮伟), Jia Guan(关佳), Chengjie Zhu(朱成杰), Runbing Li(李润兵), and Jing Shi(石兢)
    Chin. Phys. B, 2021, 30 (11):  114204.  DOI: 10.1088/1674-1056/ac078d
    Abstract ( 478 )   HTML ( 0 )   PDF (708KB) ( 67 )  
    We develop a hybrid scheme of cross phase modulation based on electromagnetically induced transparency (EIT) and active Raman gain (ARG) in a multi-level atomic medium. The cross phase modulation, with low loss and without noise, is demonstrated in a room-temperature 85Rb vapor. We show that a π radian nonlinear Kerr phase shift of the signal light relative to a reference light is observed when the signal light is modulated by the phase control field with the low light intensity. We also show that the linear and the third-order absorption can be eliminated via the Raman gain, and the phase noise of the signal light can be ignored when the phase control light is applied in this hybrid scheme.
    Ultrafast carrier dynamics of Cu2O thin film induced by two-photon excitation
    Jian Liu(刘建), Jing Li(李敬), Kai-Jun Mu(牧凯军), Xin-Wei Shi(史新伟), Jun-Qiao Wang(王俊俏), Miao Mao(毛淼), Shu Chen(陈述), and Er-Jun Liang(梁二军)
    Chin. Phys. B, 2021, 30 (11):  114205.  DOI: 10.1088/1674-1056/ac003c
    Abstract ( 515 )   HTML ( 0 )   PDF (943KB) ( 240 )  
    Cuprous oxide (Cu2O) has attracted plenty of attention for potential nonlinear photonic applications due to its superior third-order nonlinear optical property such as two-photon absorption. In this paper, we investigated the two-photon excitation induced carrier dynamics of a Cu2O thin film prepared by radio-frequency magnetron sputtering, using the femtosecond transient absorption experiments. Biexponential dynamics including an ultrafast carrier scattering (< 1 ps) followed by a carrier recombination (> 50 ps) were observed. The time constant of carrier scattering under two-photon excitation is larger than that under one-photon excitation, due to the different transition selection rules and smaller absorption coefficient of the two-photon excitation.
    Effect of pulse duration on generation of attosecond pulse with coherent wake emission
    Siyu Chen(陈思宇), Zhinan Zeng(曾志男), and Ruxin Li(李儒新)
    Chin. Phys. B, 2021, 30 (11):  114206.  DOI: 10.1088/1674-1056/abf4be
    Abstract ( 540 )   HTML ( 0 )   PDF (1628KB) ( 99 )  
    High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase (CEP) of few-cycle laser pulse. We find that short pulse duration will cause the negative chirp for the high harmonics. When the laser pulse is shortened to a few cycles, the influence of the laser CEP on the chirp of the harmonics will also become more prominent.
    Optical absorption tunability and local electric field distribution of gold-dielectric-silver three-layered cylindrical nanotube
    Ye-Wan Ma(马业万), Zhao-Wang Wu(吴兆旺), Yan-Yan Jiang(江燕燕), Juan Li(李娟), Xun-Chang Yin(尹训昌), Li-Hua Zhang(章礼华), and Ming-Fang Yi(易明芳)
    Chin. Phys. B, 2021, 30 (11):  114207.  DOI: 10.1088/1674-1056/ac0785
    Abstract ( 320 )   HTML ( 0 )   PDF (6563KB) ( 42 )  
    The effects of inner nanowire radius, shell thickness, the dielectric functions of middle layer and surrounding medium on localized surface plasmon resonance (LSPR) of gold-dielectric-silver nanotube are studied based on the quasi-static approximation. Theoretical calculation results show that LSPR of gold-dielectric-silver nanotube and LSPR numbers can be well optimized by adjusting its geometrical parameters. The longer wavelength of $\left|\omega_{-}^{-}\right\rangle$ mode takes place a distinct red-shift with increasing the inner nanowire radius and the thickness of middle dielectric layer, while a blue-shift with increasing outer nanotube thickness. The physical mechanisms are explained based on the plasmon hybridization theory, induced charges and phase retardation. In addition, the effects of middle dielectric function and surrounding medium on LSPR, and the local electric field factor are also reported. Our study provides the potential applications of gold-dielectric-silver nanotube in biological tissues, sensor and related regions.
    Integrated silicon-based suspended racetrack micro-resonator for biological solution sensing with high-order mode
    Tao Ma(马涛), Yong-Sheng Tian(田永生), Shao-Hui Liu(刘少晖), Jia-He Ma(马家赫), Heng Liu(刘恒), and Fang Wang(王芳)
    Chin. Phys. B, 2021, 30 (11):  114208.  DOI: 10.1088/1674-1056/abf106
    Abstract ( 373 )   HTML ( 0 )   PDF (3643KB) ( 79 )  
    A biological sensing structure with a high-order mode ($\mathrm{E}_{21}^{y}$) is designed, which is composed of a suspended racetrack micro-resonator (SRTMR) and a microfluidic channel. The mode characteristics, coupling properties, and sensing performances are simulated by using the finite element method (FEM). To analyze the mode confinement property, the confinement factors in the core and cladding of the suspended waveguide for the $\mathrm{E}_{11}^{x}$, $\mathrm{E}_{11}^{y}$, and $\mathrm{E}_{21}^{y}$ are calculated. The simulation results show that the refractive index (RI) sensitivity of the proposed sensing structure can be improved by using the high-order mode ($\mathrm{E}_{21}^{y}$). The RI sensitivity for the $\mathrm{E}_{21}^{y}$ mode is ~ 201 nm/RIU, which is twice to thrice higher than those for the $\mathrm{E}_{11}^{x}$ mode and the $\mathrm{E}_{11}^{y}$ mode. Considering a commercial spectrometer, the proposed sensing structure based on the SRTMR achieves a limit of detection (LOD) of ~ 4.7×10-6 RIU. Combined with the microfluidic channel, the SRTMR can possess wide applications in the clinical diagnostic assays and biochemical detections.
    Propagations of Fresnel diffraction accelerating beam in Schrödinger equation with nonlocal nonlinearity
    Yagang Zhang(张亚港), Yuheng Pei(裴宇恒), Yibo Yuan(袁一博), Feng Wen(问峰), Yuzong Gu(顾玉宗), and Zhenkun Wu(吴振坤)
    Chin. Phys. B, 2021, 30 (11):  114209.  DOI: 10.1088/1674-1056/ac068e
    Abstract ( 351 )   HTML ( 0 )   PDF (1938KB) ( 92 )  
    Accelerating beams have been the subject of extensive research in the last few decades because of their self-acceleration and diffraction-free propagation over several Rayleigh lengths. Here, we investigate the propagation dynamics of a Fresnel diffraction beam using the nonlocal nonlinear Schrödinger equation (NNLSE). When a nonlocal nonlinearity is introduced into the linear Schrödinger equation without invoking an external potential, the evolution behaviors of incident Fresnel diffraction beams are modulated regularly, and certain novel phenomena are observed. We show through numerical calculations, under varying degrees of nonlocality, that nonlocality significantly affects the evolution of Fresnel diffraction beams. Further, we briefly discuss the two-dimensional case as the equivalent of the product of two one-dimensional cases. At a critical point, the Airy-like intensity profile oscillates between the first and third quadrants, and the process repeats during propagation to yield an unusual oscillation. Our results are expected to contribute to the understanding of NNLSE and nonlinear optics.
    Ultra-longer fiber cantilever taper for simultaneous measurement of temperature and relative humidity
    Min Li(李敏), Jiwen Yin(尹辑文), Weili Yan(闫伟丽), Aimin Cong(丛爱民), Hongjuan Li(李红娟), and Wenqiang Ma(马文强)
    Chin. Phys. B, 2021, 30 (11):  114210.  DOI: 10.1088/1674-1056/ac012e
    Abstract ( 340 )   HTML ( 0 )   PDF (903KB) ( 83 )  
    An ultra-longer fiber cantilever taper for simultaneous measurement of the temperature and relative humidity (RH) with high sensitivities was proposed. The structure was fabricated by using the simple and cost-effective method only including fiber cleaving, splicing, and tapering. The length of the cantilever taper is about 1.5 mm. The dip A and dip B were measured simultaneously, owing to the ultra-long length and super-fine size, the temperature sensitivities of the dip A and dip B reached as high as 127.3 pm/℃ and 0 pm/℃ between 25 ℃ and 50 ℃, and the RH sensitivities are -31.2 pm/% RH and -29.2 pm/% RH with a broad RH interval ranging from 20% RH to 70% RH. Besides, the proposed structure showed good linearity in the sensing process and small temperature crosstalk. It will be found in wide applications in environmental monitoring, food processing, and industries.
    Band offsets and electronic properties of the Ga2O3/FTO heterojunction via transfer of free-standing Ga2O3 onto FTO/glass
    Xia Wang(王霞), Wei-Fang Gu(古卫芳), Yong-Feng Qiao(乔永凤), Zhi-Yong Feng(冯志永), Yue-Hua An(安跃华), Shao-Hui Zhang(张少辉), and Zeng Liu(刘增)
    Chin. Phys. B, 2021, 30 (11):  114211.  DOI: 10.1088/1674-1056/ac11e7
    Abstract ( 367 )   HTML ( 0 )   PDF (1062KB) ( 75 )  
    The determination of band offsets is crucial in the optimization of Ga2O3-based devices, since the band alignment types could determine the operations of devices due to the restriction of carrier transport across the heterogeneous interfaces. In this work, the band offsets of the Ga2O3/FTO heterojunction are studied using x-ray photoelectron spectroscopy (XPS) based on Kraut's method, which suggests a staggered type-Ⅱ alignment with a conduction band offset (ΔEC) of 1.66 eV and a valence band offset (ΔEV) of -2.41 eV. Furthermore, the electronic properties of the Ga2O3/FTO heterostructure are also measured, both in the dark and under ultraviolet (UV) illuminated conditions (254 nm UV light). Overall, this work can provide meaningful guidance for the design and construction of oxide hetero-structured devices based on wide-bandgap semiconducting Ga2O3.
    RAPID COMMUNICATION
    Generation of domain-wall solitons in an anomalous dispersion fiber ring laser
    Wen-Yan Zhang(张文艳), Kun Yang(杨坤), Li-Jie Geng(耿利杰), Nan-Nan Liu(刘楠楠), Yun-Qi Hao(郝蕴琦), Tian-Hao Xian(贤天浩), and Li Zhan(詹黎)
    Chin. Phys. B, 2021, 30 (11):  114212.  DOI: 10.1088/1674-1056/ac0e22
    Abstract ( 455 )   HTML ( 0 )   PDF (730KB) ( 87 )  
    We report experimental observations performed using a net anomalous dispersion Er-doped fiber ring laser without polarization-selective elements, highlighting the domain-wall solitary pulses generated under the incoherent polarization coupling. By adjusting the pump power and the polarization state appropriately, bright and dark solitons can stably co-exist in the cavity, both centered at 1562.16 nm with a 3-dB spectral width of ~ 0.15 nm and a repetition rate of 3.83 MHz. Moreover, the 0.8 mm long thulium-doped fiber (TDF) facilitated the mode-locking and self-starting of the laser. This is the first demonstration of a laser being used to generate bright and dark solitons synchronously while using TDF as the saturable absorber (SA). Except possessing the all-fiber structure, the laser exhibits good stability, which may have a significant influence on improvement of the pulse-laser design, and may broaden practical applications in optical sensing, optical communication, and soliton multiplexed systems.
    SPECIAL TOPIC—Optical field manipulation
    Minimum structure of high-harmonic spectrafrom aligned O2 and N2 molecules
    Bo Yan(闫博), Yi-Chen Wang(王一琛), Qing-Hua Gao(高庆华), Fang-Jing Cheng(程方晶), Qiu-Shuang Jing(景秋霜), Hong-Jing Liang(梁红静), and Ri Ma(马日)
    Chin. Phys. B, 2021, 30 (11):  114213.  DOI: 10.1088/1674-1056/abfbd9
    Abstract ( 526 )   HTML ( 2 )   PDF (567KB) ( 150 )  
    We experimentally investigated the high-order harmonic generation (HHG) from aligned O2 and N2 molecules in a linearly polarized laser field, and presented the dependence of the harmonic spectrum on the driving laser intensity and molecular alignment angle. The minimum position of HHG of O2 varies with changing the laser intensity, which is caused by multi-orbital interference. However, the location of the observed minimum structure in N2 harmonic spectrum remained unchanged upon changing the laser intensity. The mechanism of the spectral minimum for N2 case is regarded as a Cooper-like minimum in HHG associated with the molecular electronic structure. This work indicates that harmonic spectroscopy can effectively uncover information about molecular structure and electron dynamics.
    Theory of multiphoton photoemission disclosing excited states in conduction band of individual TiO2 nanoparticles
    Bochao Li(李博超), Hao Li(李浩), Chang Yang(杨畅), Boyu Ji(季博宇), Jingquan Lin(林景全), and Toshihisa Tomie(富江敏尚)
    Chin. Phys. B, 2021, 30 (11):  114214.  DOI: 10.1088/1674-1056/ac1b8d
    Abstract ( 481 )   HTML ( 0 )   PDF (696KB) ( 146 )  
    A theory of multiphoton photoemission is derived to explain the experimentally observed monotonic decrease with the wavelength in the electron yield of TiO2 nanoparticles (NPs) by as large as four orders of magnitude. It is found that the fitting parameter corresponds to the energy position of Ti3d eg and t2g states, and the derived theory is a novel diagnostic of excited states in the conduction band, very importantly, applicable to individual NPs. The difference between four-photon slope NPs and three-photon slope NPs is attributed to the difference in defect density. The success of the theory in solving the puzzling result shows that thermal emission from high-lying levels may dominate over direct multiphoton ionization in solids when the photon number larger than four is required.
    Controlled plasmon-enhanced fluorescence by spherical microcavity
    Jingyi Zhao(赵静怡), Weidong Zhang(张威东), Te Wen(温特), Lulu Ye(叶璐璐), Hai Lin(林海), Jinglin Tang(唐靖霖), Qihuang Gong(龚旗煌), and Guowei Lyu(吕国伟)
    Chin. Phys. B, 2021, 30 (11):  114215.  DOI: 10.1088/1674-1056/ac0daa
    Abstract ( 296 )   HTML ( 0 )   PDF (1632KB) ( 105 )  
    A surrounding electromagnetic environment can engineer spontaneous emissions from quantum emitters through the Purcell effect. For instance, a plasmonic antenna can efficiently confine an electromagnetic field and enhance the fluorescent process. In this study, we demonstrate that a photonic microcavity can modulate plasmon-enhanced fluorescence by engineering the local electromagnetic environment. Consequently, we constructed a plasmon-enhanced emitter (PE-emitter), which comprised a nanorod and a nanodiamond, using the nanomanipulation technique. Furthermore, we controlled a polystyrene sphere approaching the PE-emitter and investigated in situ the associated fluorescent spectrum and lifetime. The emission of PE-emitter can be enhanced resonantly at the photonic modes as compared to that within the free spectral range. The spectral shape modulated by photonic modes is independent of the separation between the PS sphere and PE-emitter. The band integral of the fluorescence decay rate can be enhanced or suppressed after the PS sphere couples to the PE-emitters, depending on the coupling strength between the plasmonic antenna and the photonic cavity. These findings can be utilized in sensing and imaging applications.
    ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
    Multi-band asymmetric transmissions based on bi-layer windmill-shaped metamaterial
    Ying-Hua Wang(王英华), Jie Li(李杰), Zheng-Gao Dong(董正高), Yan Li(李妍), and Xu Zhang(张旭)
    Chin. Phys. B, 2021, 30 (11):  114216.  DOI: 10.1088/1674-1056/ac16d2
    Abstract ( 352 )   HTML ( 0 )   PDF (1683KB) ( 58 )  
    This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90° and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions (ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multi-band from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.
    Phonon dispersion relations of crystalline solids based on LAMMPS package
    Zhiyong Wei(魏志勇), Tianhang Qi(戚天航), Weiyu Chen(陈伟宇), and Yunfei Chen(陈云飞)
    Chin. Phys. B, 2021, 30 (11):  114301.  DOI: 10.1088/1674-1056/abf4c0
    Abstract ( 640 )   HTML ( 13 )   PDF (1199KB) ( 149 )  
    The phonon dispersion relations of crystalline solids play an important role in determining the mechanical and thermal properties of materials. The phonon dispersion relation, as well as the vibrational density of states, is also often used as an indicator of variation of lattice thermal conductivity with the external stress, defects, etc. In this study, a simple and fast tool is proposed to acquire the phonon dispersion relation of crystalline solids based on the LAMMPS package. The theoretical details for the calculation of the phonon dispersion relation are derived mathematically and the computational flow chart is present. The tool is first used to calculate the phonon dispersion relation of graphene with two atoms in the unit cell. Then, the phonon dispersions corresponding to several potentials or force fields, which are commonly used in the LAMMPS package to modeling the graphene, are obtained to compare with that from the DFT calculation. They are further extended to evaluate the accuracy of the used potentials before the molecular dynamics simulation. The tool is also used to calculate the phonon dispersion relation of superlattice structures that contains more than one hundred of atoms in the unit cell, which predicts the phonon band gaps along the cross-plane direction. Since the phonon dispersion relation plays an important role in the physical properties of condensed matter, the proposed tool for the calculation of the phonon dispersion relation is of great significance for predicting and explaining the mechanical and thermal properties of crystalline solids.
    Effect of Joule heating on the electroosmotic microvortex and dielectrophoretic particle separation controlled by local electric field
    Bing Yan(严兵), Bo Chen(陈波), Yongliang Xiong(熊永亮), and Zerui Peng(彭泽瑞)
    Chin. Phys. B, 2021, 30 (11):  114701.  DOI: 10.1088/1674-1056/abf108
    Abstract ( 292 )   HTML ( 0 )   PDF (1469KB) ( 38 )  
    Dielectrophoresis (DEP) technology has become important application of microfluidic technology to manipulate particles. By using a local modulating electric field to control the combination of electroosmotic microvortices and DEP, our group proposed a device using a direct current (DC) electric field to achieve continuous particle separation. In this paper, the influence of the Joule heating effect on the continuous separation of particles is analyzed. Results show that the Joule heating effect is caused by the local electric field, and the Joule heating effect caused by adjusting the modulating voltage is more significant than that by driving voltage. Moreover, a non-uniform temperature distribution exists in the channel due to the Joule heating effect, and the temperature is the highest at the midpoint of the modulating electrodes. The channel flux can be enhanced, and the enhancement of both the channel flux and temperature is more obvious for a stronger Joule heating effect. In addition, the ability of the vortices to trap particles is enhanced since a larger DEP force is exerted on the particles with the Joule heating effect; and the ability of the vortex to capture particles is stronger with a stronger Joule heating effect. The separation efficiency can also be increased because perfect separation is achieved at a higher channel flux. Parameter optimization of the separation device, such as the convective heat transfer coefficient of the channel wall, the length of modulating electrode, and the width of the channel, is performed.
    RAPID COMMUNICATION
    A composite micromotor driven by self-thermophoresis and Brownian rectification Hot!
    Xin Lou(娄辛), Nan Yu(余楠), Ke Chen(陈科), Xin Zhou(周昕), Rudolf Podgornik, and Mingcheng Yang(杨明成)
    Chin. Phys. B, 2021, 30 (11):  114702.  DOI: 10.1088/1674-1056/ac2727
    Abstract ( 729 )   HTML ( 1 )   PDF (517KB) ( 484 )  
    Brownian motors and self-phoretic microswimmers are two typical micromotors, for which thermal fluctuations play different roles. Brownian motors utilize thermal noise to acquire unidirectional motion, while thermal fluctuations randomize the self-propulsion of self-phoretic microswimmers. Here we perform mesoscale simulations to study a composite micromotor composed of a self-thermophoretic Janus particle under a time-modulated external ratchet potential. The composite motor exhibits a unidirectional transport, whose direction can be reversed by tuning the modulation frequency of the external potential. The maximum transport capability is close to the superposition of the drift speed of the pure Brownian motor and the self-propelling speed of the pure self-thermophoretic particle. Moreover, the hydrodynamic effect influences the orientation of the Janus particle in the ratched potential, hence also the performance of the composite motor. Our work thus provides an enlightening attempt to actively exploit inevitable thermal fluctuations in the implementation of the self-phoretic microswimmers.
    PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
    Simulations on the multi-shell target ignition driven by radiation pulse in Z-pinch dynamic hohlraum
    Shi-Jia Chen(陈诗佳), Yan-Yun Ma(马燕云), Fu-Yuan Wu(吴福源), Xiao-Hu Yang(杨晓虎), Yun Yuan(袁赟), Ye Cui(崔野), and Rafael Ramis
    Chin. Phys. B, 2021, 30 (11):  115201.  DOI: 10.1088/1674-1056/ac01c2
    Abstract ( 597 )   HTML ( 0 )   PDF (1822KB) ( 128 )  
    We present the first simulation results of a multi-shell target ignition driven by Z-pinch dynamic hohlraum radiation pulse. The radiation pulse is produced with a special Z-pinch dynamic hohlraum configuration, where the hohlraum is composed of a single metal liner, a low-Z plastic foam, and a high-Z metallic foam. The implosion dynamics of a hohlraum and a multi-shell target are investigated separately by the one-dimensional code MULTI-IFE. When the peak drive current is 50 MA, simulations suggest that an x-ray pulse with nearly constant radiation temperature (~ 310 eV) and a duration about 9 ns can be obtained. A small multi-shell target with a radius of 1.35 mm driven by this radiation pulse is able to achieve volumetric ignition with an energy gain (G) about 6.19, where G is the ratio of the yield to the absorbed radiation. Through this research, we better understand the effects of non-uniformities and hydrodynamics instabilities in Z-pinch dynamic hohlraum.
    Ultrabright γ-ray emission from the interaction of an intense laser pulse with a near-critical-density plasma
    Aynisa Tursun(阿依妮萨·图尔荪), Mamat Ali Bake(买买提艾力·巴克), Baisong Xie(谢柏松), Yasheng Niyazi(亚生·尼亚孜), and Abuduresuli Abudurexiti(阿不都热苏力·阿不都热西提)
    Chin. Phys. B, 2021, 30 (11):  115202.  DOI: 10.1088/1674-1056/abfb59
    Abstract ( 412 )   HTML ( 2 )   PDF (1407KB) ( 96 )  
    An efficient scheme for generating ultrabright γ-rays from the interaction of an intense laser pulse with a near-critical-density plasma is studied by using the two-dimensional particle-in-cell simulation including quantum electrodynamic effects. We investigate the effects of target shape on γ-ray generation efficiency using three configurations of the solid foils attached behind the near-critical-density plasma: a flat foil without a channel (target 1), a flat foil with a channel (target 2), and a convex foil with a channel (target 3). When an intense laser propagates in a near-critical-density plasma, a large number of electrons are trapped and accelerated to GeV energy, and emit γ-rays via nonlinear betatron oscillation in the first stage. In the second stage, the accelerated electrons collide with the laser pulse reflected from the foil and emit high-energy, high-density γ-rays via nonlinear Compton scattering. The simulation results show that compared with the other two targets, target 3 affords better focusing of the laser field and electrons, which decreases the divergence angle of γ-photons. Consequently, denser and brighter γ-rays are emitted when target 3 is used. Specifically, a dense γ-ray pulse with a peak brightness of 4.6×1026 photons/s/mm2/mrad2/0.1%BW (at 100 MeV) and 1.8×1023 photons/s/mm2/mrad2/0.1%BW (at 2 GeV) are obtained at a laser intensity of 8.5×1022 W/cm2 when the plasma density is equal to the critical plasma density nc. In addition, for target 3, the effects of plasma channel length, foil curvature radius, laser polarization, and laser intensity on the γ-ray emission are discussed, and optimal values based on a series of simulations are proposed.
    CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
    Analytical solution of crystal diffraction intensity
    Wan-Li Shang(尚万里), Ao Sun(孙奥), Hua-Bin Du(杜华冰), Guo-Hong Yang(杨国洪), Min-Xi Wei(韦敏习), Xu-Fei Xie(谢旭飞), Xing-Sen Che(车兴森), Li-Fei Hou(侯立飞), Wen-Hai Zhang(张文海), Miao Li(黎淼), Jun Shi(施军), Feng Wang(王峰), Hai-En He(何海恩), Jia-Min Yang(杨家敏), Shao-En Jiang(江少恩), and Bao-Han Zhang(张保汉)
    Chin. Phys. B, 2021, 30 (11):  116101.  DOI: 10.1088/1674-1056/ac0132
    Abstract ( 337 )   HTML ( 0 )   PDF (886KB) ( 44 )  
    Plasma density and temperature can be diagnosed by x-ray line emission measurement with crystal, and bent crystals such as von Hamos and Hall structures are proposed to improve the diffraction brightness. In this study, a straightforward solution for the focusing schemes of flat and bent crystals is provided. Simulations with XOP code are performed to validate the analytical model, and good agreements are achieved. The von Hamos or multi-cone crystal can lead to several hundred times intensity enhancements for a 200μm plasma source. This model benefits the applications of the focusing bent crystals.
    Theoretical study of reactive melt infiltration to fabricate Co-Si/C composites
    Saqib Shahzad, Khurram Iqbal, and Zaheer Uddin
    Chin. Phys. B, 2021, 30 (11):  116102.  DOI: 10.1088/1674-1056/abeee7
    Abstract ( 346 )   HTML ( 0 )   PDF (5458KB) ( 42 )  
    Cobalt-silicon based carbon composites (Co-Si/C) have established a noteworthy consideration in recent years as a replacement for conventional materials in the automotive and aerospace industries. To achieve the composite, a reactive melt infiltration process (RMI) is used, in which a melt impregnates a porous preform by capillary force. This method promises a high-volume fraction of reinforcement and can be steered in such a way to get the good “near-net” shaped components. A mathematical model is developed using reaction-formed Co-Si alloy/C composite as a prototype system for this process. The wetting behavior and contact angle are discussed; surface tension and viscosity are calculated by Wang's and Egry's equations, respectively. Pore radii of 5μm and 10μm are set as a reference on highly oriented pyrolytic graphite. The graphs are plotted using the model, to study some aspects of the infiltration dynamics. This highlights the possible connections among the various processes. In this attempt, the Co-Si (62.5 at.% silicon) alloy's maximum infiltration at 5 μm and 10 μm radii are found as 0.05668 m at 125 s and 0.22674 m at 250 s, respectively.
    Accurate prediction method for the microstructure of amorphous alloys without non-metallic elements
    Wei Zhao(赵伟), Jia-Lin Cheng(成家林), Gong Li(李工), and Xin Wang(王辛)
    Chin. Phys. B, 2021, 30 (11):  116103.  DOI: 10.1088/1674-1056/abfd9d
    Abstract ( 377 )   HTML ( 0 )   PDF (581KB) ( 25 )  
    A new structural parameter of amorphous alloys called atomic bond proportion was proposed, and a topological algorithm for the structural parameter was proven feasible in the previous work. In the present study, a correction factor, λ, is introduced to optimize the algorithm and dramatically improve the calculation accuracy of the atomic bond proportion. The correction factor represents the ability of heterogeneous atoms to combine with one another to form the metallic bonds and it is associated with the uniformity of the master alloy, mixing enthalpy, cooling rate during preparation, and annealing time. The correction factor provides a novel pathway for researching the structures of the amorphous alloys.
    Dislocation slip behaviors in high-quality bulk GaN investigated by nanoindentation
    Kai-Heng Shao(邵凯恒), Yu-Min Zhang(张育民), Jian-Feng Wang(王建峰), and Ke Xu(徐科)
    Chin. Phys. B, 2021, 30 (11):  116104.  DOI: 10.1088/1674-1056/abfd9e
    Abstract ( 409 )   HTML ( 1 )   PDF (9277KB) ( 79 )  
    The dislocation slip behaviors in GaN bulk crystal are investigated by nanoindentation, the dislocation distribution patterns formed around an impress are observed by cathodoluminescence (CL) and cross-sectional transmission electron microscope (TEM). Dislocation loops, vacancy luminescence, and cross-slips show hexagonal symmetry around the <11-20> and <1-100> direction on c-plane. It is found that the slip planes of dislocation in GaN crystal are dominated in {0001} basal plane and {10-11} pyramid plane. According to the dislocation intersection theory, we come up with the dislocation formation process and the related mechanisms are discussed.
    Optically-controlled resistive switching effectsof CdS nanowire memtransistor
    Jia-Ning Liu(刘嘉宁), Feng-Xiang Chen(陈凤翔), Wen Deng(邓文), Xue-Ling Yu(余雪玲), and Li-Sheng Wang(汪礼胜)
    Chin. Phys. B, 2021, 30 (11):  116105.  DOI: 10.1088/1674-1056/ac16ce
    Abstract ( 510 )   HTML ( 1 )   PDF (1569KB) ( 70 )  
    Since it was proposed, memtransistors have been a leading candidate with powerful capabilities in the field of neural morphological networks. A memtransistor is an emerging structure combining the concepts of a memristor and a field-effect transistor with low-dimensional materials, so that both optical excitation and electrical stimuli can be used to modulate the memristive characteristics, which make it a promising multi-terminal hybrid device for synaptic structures. In this paper, a single CdS nanowire memtransistor has been constructed by the micromechanical exfoliation and alignment lithography methods. It is found that the CdS memtransistor has good non-volatile bipolar memristive characteristics, and the corresponding switching ratio is as high as 106 in the dark. While under illumination, the behavior of the CdS memtransistor is similar to that of a transistor or a memristor depending on the incident wavelengths, and the memristive switching ratio varies in the range of 10 to 105 with the increase of the incident wavelength in the visible light range. In addition, the optical power is also found to affect the memristive characteristics of the device. All of these can be attributed to the modulation of the potential barrier by abundant surface states of nanowires and the illumination influences on the carrier concentrations in nanowires.
    Preparation of graphene on SiC by laser-accelerated pulsed ion beams
    Danqing Zhou(周丹晴), Dongyu Li(李东彧), Yuhan Chen(陈钰焓), Minjian Wu(吴旻剑), Tong Yang(杨童), Hao Cheng(程浩), Yuze Li(李昱泽), Yi Chen(陈艺), Yue Li(李越), Yixing Geng(耿易星), Yanying Zhao(赵研英), Chen Lin(林晨), Xueqing Yan(颜学庆), and Ziqiang Zhao(赵子强)
    Chin. Phys. B, 2021, 30 (11):  116106.  DOI: 10.1088/1674-1056/abfc3c
    Abstract ( 556 )   HTML ( 1 )   PDF (1930KB) ( 129 )  
    Laser-accelerated ion beams (LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100 ℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample.
    Molecular dynamics simulations of dopant effectson lattice trapping of cracks in Ni matrix
    Shulan Liu(刘淑兰) and Huijing Yang(杨会静)
    Chin. Phys. B, 2021, 30 (11):  116107.  DOI: 10.1088/1674-1056/ac0780
    Abstract ( 360 )   HTML ( 0 )   PDF (1433KB) ( 63 )  
    Molecular dynamic analysis was performed on pure and doped (by Re, Ru, Co or W) Ni at 300 K using the embedded-atom-method (EAM) potentials to understand the crack formation of the doped Ni matrix in the (010)[001] orientation. When Ni was doped with Re, Ru, and W, the matrix demonstrated increased lattice trapping limits and, as a result, improved the mechanical properties. Consequently, this prevented the bond breakage at the crack tips and promoted crack healing. The average atomic and surface energy values increased when Re, Ru, and W were added. Analysis of these energy increase helped us to understand the influence these elements had on the lattice trapping limits. The fracture strength of the Ni matrix at 300 K increased because of the formation of the stronger Ni-Re, Ni-Ru, and Ni-W bonds. At the same time, doping the Ni matrix with Co did not demonstrate any strengthening effects because of the formation of Co-Ni bonds, which are weaker than the Ni-Ni bonds. Out of all dopants tested in this work, Ni doping with W showed the best results.
    Ab-initio calculations of bandgap tuning of In1-xGaxY (Y = N, P) alloys for optoelectronic applications
    Muhammad Rashid, Jamil M, Mahmood Q, Shahid M Ramay, Asif Mahmood A, and Ghaithan H M
    Chin. Phys. B, 2021, 30 (11):  116301.  DOI: 10.1088/1674-1056/abf128
    Abstract ( 440 )   HTML ( 0 )   PDF (7073KB) ( 41 )  
    The Ⅲ-V alloys and doping to tune the bandgap for solar cells and other optoelectronic devices has remained a hot topic of research for the last few decades. In the present article, the bandgap tuning and its influence on optical properties of In1-xGaxN/P, where (x = 0.0, 0.25, 0.50, 0.75, and 1.0) alloys are comprehensively analyzed by density functional theory based on full-potential linearized augmented plane wave method (FP-LAPW) and modified Becke and Johnson potentials (TB-mBJ). The direct bandgaps turn from 0.7 eV to 3.44 eV, and 1.41 eV to 2.32 eV for In1-xGaxN/P alloys, which increases their potentials for optoelectronic devices. The optical properties are discussed such as dielectric constants, refraction, absorption, optical conductivity, and reflection. The light is polarized in the low energy region with minimum reflection. The absorption and optical conduction are maxima in the visible region, and they are shifted into the ultraviolet region by Ga doping. Moreover, static dielectric constant ε1(0) is in line with the bandgap from Penn's model.
    Synthesis and thermoelectric properties of Bi-doped SnSe thin films
    Jun Pang(庞军), Xi Zhang(张析), Limeng Shen(申笠蒙), Jiayin Xu(徐家胤), Ya Nie(聂娅), and Gang Xiang(向钢)
    Chin. Phys. B, 2021, 30 (11):  116302.  DOI: 10.1088/1674-1056/ac11da
    Abstract ( 423 )   HTML ( 0 )   PDF (2145KB) ( 104 )  
    Bi doped n-type SnSe thin films were prepared by chemical vapor deposition (CVD) and their structure and thermoelectric properties were studied. The x-ray diffraction patterns, x-ray photoelectron spectroscopy, and microscopic images show that the prepared SnSe thin films were composed of pure SnSe crystals. The Seebeck coefficients of the Bi-doped SnSe were greatly improved compared to that of undoped SnSe thin films. Specifically, Sn0.99Bi0.01Se thin film exhibited a Seebeck coefficient of -905.8μV·K-1 at 600 K, much higher than 285.5 μV·K-1 of undoped SnSe thin film. Further first-principles calculations reveal that the enhancement of the thermoelectric properties can be explained mainly by the Fermi level lifting and the carrier pockets increasing near the Fermi level due to Bi doping in the SnSe samples. Our results suggest the potentials of the Bi-doped SnSe thin films in thermoelectric applications.
    Metal substrates-induced phase transformation of monolayer transition metal dichalcogenides for hydrogen evolution catalysis
    Zhe Wang(王喆) and Wenguang Zhu(朱文光)
    Chin. Phys. B, 2021, 30 (11):  116401.  DOI: 10.1088/1674-1056/abfbd1
    Abstract ( 408 )   HTML ( 0 )   PDF (2455KB) ( 72 )  
    Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical, optical, and catalytic properties. Effective control of the relative stability and transformation of different phases in these materials is thus of critical importance for applications. Using density functional theory calculations, we investigate the effects of low-work-function metal substrates including Ti, Zr, and Hf on the structural, electronic, and catalytic properties of monolayer MoS2 and WS2. The results indicate that such substrates not only convert the energetically stable structure from the 1H phase to the 1T'/1T phase, but also significantly reduce the kinetic barriers of the phase transformation. Furthermore, our calculations also indicate that the 1T' phase of MoS2 with Zr or Hf substrate is a potential catalyst for the hydrogen evolution reaction.
    Effect of the liquid temperature on the interaction behavior for single water droplet impacting on the immiscible liquid
    Tiantian Wang(汪甜甜), Changjian Wang(王昌建), Shengchao Rui(芮圣超), and Kai Pan(泮凯)
    Chin. Phys. B, 2021, 30 (11):  116801.  DOI: 10.1088/1674-1056/abf34b
    Abstract ( 416 )   HTML ( 0 )   PDF (1213KB) ( 63 )  
    The interaction of single water droplet impacting on immiscible liquid surface was focused with the temperature varying from 50 ℃ to 210 ℃. The impact behavior is recorded with a high-speed camera running at 2000 frames per second. It is found that droplet diameter, oil temperature, and Weber number have important influences on impact behaviors. Three typical phenomena, including penetration, crater-jet, and crater-jet-secondary jet, were observed. Penetration only occurs when the Weber number is below 105. With Weber number increasing to 302, the jet begins to appear. Moreover, to gain deeper physical insight into the crater formation and jet formation, the energy of droplet impingement onto the liquid pool surface was estimated. The oil temperature has a significant effect on the energy conversion efficiency. High temperature is beneficial to improve energy conversion efficiency.
    RAPID COMMUNICATION
    Realization of semiconducting Cu2Se by direct selenization of Cu(111) Hot!
    Yumu Yang(杨雨沐), Qilong Wu(吴奇龙), Jiaqi Deng(邓嘉琦), Jing Wang(王静), Yu Xia(夏雨), Xiaoshuai Fu(富晓帅), Qiwei Tian(田麒玮), Li Zhang(张力), Long-Jing Yin(殷隆晶), Yuan Tian(田园), Sheng-Yi Xie(谢声意), Lijie Zhang(张利杰), and Zhihui Qin(秦志辉)
    Chin. Phys. B, 2021, 30 (11):  116802.  DOI: 10.1088/1674-1056/ac0037
    Abstract ( 571 )   HTML ( 1 )   PDF (1904KB) ( 302 )  
    Bulk group IB transition-metal chalcogenides have been widely explored due to their applications in thermoelectrics. However, a layered two-dimensional form of these materials has been rarely reported. Here, we realize semiconducting Cu2Se by direct selenization of Cu(111). Scanning tunneling microcopy measurements combined with first-principles calculations allow us to determine the structural and electronic properties of the obtained structure. X-ray photoelectron spectroscopy data reveal chemical composition of the sample, which is Cu2Se. The observed moiré pattern indicates a lattice mismatch between Cu2Se and the underlying Cu(111)-$\sqrt{3}$×$\sqrt{3}$ surface. Differential conductivity obtained by scanning tunneling spectroscopy demonstrates that the synthesized Cu2Se exhibits a band gap of 0.78 eV. Furthermore, the calculated density of states and band structure demonstrate that the isolated Cu2Se is a semiconductor with an indirect band gap of ~ 0.8 eV, which agrees quite well with the experimental results. Our study provides a simple pathway varying toward the synthesis of novel layered 2D transition chalcogenides materials.
    REVIEW
    Accurate GW0 band gaps and their phonon-induced renormalization in solids
    Tong Shen(申彤), Xiao-Wei Zhang(张小伟), Min-Ye Zhang(张旻烨), Hong Jiang(蒋鸿), and Xin-Zheng Li(李新征)
    Chin. Phys. B, 2021, 30 (11):  117101.  DOI: 10.1088/1674-1056/ac0041
    Abstract ( 407 )   HTML ( 0 )   PDF (1014KB) ( 124 )  
    Recent years, huge progress of first-principles methods has been witnessed in calculating the quasiparticle band gaps, with many-body perturbation theory in the GW approximation being the standard choice, where G refers to Green's function and W denotes the dynamically screened Coulomb interaction. Numerically, the completeness of the basis set has been extensively discussed, but in practice far from carefully addressed. Beyond the static description of the nuclei, the electron-phonon interactions (EPIs) are ubiquitous, which cause zero-point renormalization (ZPR) of the band gaps. Therefore, to obtain high quality band gaps, one needs both accurate quasiparticle energies and accurate treatments of EPIs. In this article, we review methods on this. The completeness of the basis set is analyzed in the framework of linearized augmented plane waves, by adding high-energy local orbitals (HLOs). The electron-phonon matrix elements and self-energy are discussed, followed by the temperature dependence of the band gaps in both perturbative and non-perturbative methods. Applications of such an analysis on bulk wurtzite BeO and monolayer honeycomb BeO are given. Adding HLOs widens their GW0 band gaps by ~ 0.4 eV while ZPR narrows them by similar amount. These influences cancel each other, which explains the fortuitous agreement between experiment and theory when the basis set is incomplete and the EPIs are absent. The phonon-induced renormalization, a term often neglected in calculations of the band gaps, is also emphasized by its large magnitude.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Simulations of monolayer SiC transistors with metallic 1T-phase MoS2 contact for high performance application
    Hai-Qing Xie(谢海情), Dan Wu(伍丹), Xiao-Qing Deng(邓小清), Zhi-Qiang Fan(范志强), Wu-Xing Zhou(周五星), Chang-Qing Xiang(向长青), and Yue-Yang Liu(刘岳阳)
    Chin. Phys. B, 2021, 30 (11):  117102.  DOI: 10.1088/1674-1056/abeee0
    Abstract ( 429 )   HTML ( 1 )   PDF (3845KB) ( 139 )  
    We preform a first-principles study of performance of 5 nm double-gated (DG) Schottky-barrier field effect transistors (SBFETs) based on two-dimensional SiC with monolayer or bilayer metallic 1T-phase MoS2 contacts. Because of the wide bandgap of SiC, the corresponding DG SBFETs can weaken the short channel effect. The calculated transfer characteristics also meet the standard of the high performance transistor summarized by international technology road-map for semiconductors. Moreover, the bilayer metallic 1T-phase MoS2 contacts in three stacking structures all can further raise the ON-state currents of DG SiC SBFETs in varying degrees. The above results are helpful and instructive for design of short channel transistors in the future.
    Electronic and optical properties of 3N-doped graphdiyne/MoS2 heterostructures tuned by biaxial strain and external electric field
    Dong Wei(魏东), Yi Li(李依), Zhen Feng(冯振), Gaofu Guo(郭高甫), Yaqiang Ma(马亚强), Heng Yu(余恒), Qingqing Luo(骆晴晴), Yanan Tang(唐亚楠), and Xianqi Dai(戴宪起)
    Chin. Phys. B, 2021, 30 (11):  117103.  DOI: 10.1088/1674-1056/ac1927
    Abstract ( 400 )   HTML ( 1 )   PDF (3933KB) ( 63 )  
    The construction of van der Waals (vdW) heterostructures by stacking different two-dimensional layered materials have been recognised as an effective strategy to obtain the desired properties. The 3N-doped graphdiyne (N-GY) has been successfully synthesized in the laboratory. It could be assembled into a supercapacitor and can be used for tensile energy storage. However, the flat band and wide forbidden bands could hinder its application of N-GY layer in optoelectronic and nanoelectronic devices. In order to extend the application of N-GY layer in electronic devices, MoS2 was selected to construct an N-GY/MoS2 heterostructure due to its good electronic and optical properties. The N-GY/MoS2 heterostructure has an optical absorption range from the visible to ultraviolet with a absorption coefficient of 105 cm-1. The N-GY/MoS2 heterostructure exhibits a type-Ⅱ band alignment allows the electron-hole to be located on N-GY and MoS2 respectively, which can further reduce the electron-hole complexation to increase exciton lifetime. The power conversion efficiency of N-GY/MoS2 heterostructure is up to 17.77%, indicating it is a promising candidate material for solar cells. In addition, the external electric field and biaxial strain could effectively tune the electronic structure. Our results provide a theoretical support for the design and application of N-GY/MoS2 vdW heterostructures in semiconductor sensors and photovoltaic devices.
    TOPICAL REVIEW—Two-dimensional magnetic materials and devices
    Review of Raman spectroscopy of two-dimensional magnetic van der Waals materials
    Yu-Jia Sun(孙宇伽), Si-Min Pang(庞思敏), and Jun Zhang(张俊)
    Chin. Phys. B, 2021, 30 (11):  117104.  DOI: 10.1088/1674-1056/ac1e0f
    Abstract ( 539 )   HTML ( 12 )   PDF (3052KB) ( 1136 )  
    Ultrathin van der Waals (vdW) magnets provide a possibility to access magnetic ordering in the two-dimensional (2D) limit, which are expected to be applied in the spintronic devices. Raman spectroscopy is a powerful characterization method to investigate the spin-related properties in 2D vdW magnets, including magnon and spin-lattice interaction, which are hardly accessible by other optical methods. In this paper, the recent progress of various magnetic properties in 2D vdW magnets studied by Raman spectroscopy is reviewed, including the magnetic transition, spin-wave, spin-lattice interaction, symmetry tuning induced by spin ordering, and nonreciprocal magneto-phonon Raman scattering.
    SPECIAL TOPIC—Two-dimensional magnetic materials and devices
    Carrier and magnetism engineering for monolayer SnS2 by high throughput first-principles calculations
    Qing Zhan(詹庆), Xiaoguang Luo(罗小光), Hao Zhang(张皓), Zhenxiao Zhang(张振霄), Dongdong Liu(刘冬冬), and Yingchun Cheng(程迎春)
    Chin. Phys. B, 2021, 30 (11):  117105.  DOI: 10.1088/1674-1056/ac2805
    Abstract ( 444 )   HTML ( 2 )   PDF (1152KB) ( 222 )  
    Two-dimensional (2D) semiconducting tin disulfide (SnS2) has been widely used for optoelectronic applications. To functionalize SnS2 for extending its application, we investigate the stability, electronic and magnetic properties of substitutional doping by high throughput first-principles calculations. There are a lot of elements that can be doped in monolayer SnS2. Nonmetal in group A can introduce p-type and n-type carriers, while most metals in group A can only lead to p-type doping. Not only 3d, but also 4d and 5d transition metals in groups VB to VⅢB9 can introduce magnetism in SnS2, which is potentially applicable for spintronics. This study provides a comprehensive view of functionalization of SnS2 by substitutional doping, which will guide further experimental realization.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Tuning charge and orbital ordering in DyNiO3 by biaxial strain
    Litong Jiang(姜丽桐), Kuijuan Jin(金奎娟), Wenning Ren(任文宁), and Guozhen Yang(杨国桢)
    Chin. Phys. B, 2021, 30 (11):  117106.  DOI: 10.1088/1674-1056/abfbcf
    Abstract ( 524 )   HTML ( 0 )   PDF (1750KB) ( 112 )  
    The first-principles calculations were used to explore the tunable electronic structure in DyNiO3 (DNO) under the effects of the biaxial compressive and tensile strains. We explored how the biaxial strain tunes the orbital hybridization and influences the charge and orbital ordering states. We found that breathing mode and Jahn-Teller distortion play a primary role in charge ordering state and orbital ordering state, respectively. Additionally, the calculated results revealed that the biaxial strain has the ability to manipulate the phase competition between the two states. A phase transition point has been found under tensile train. If the biaxial train is larger than the point, the system favors orbital ordering state. If the strain is smaller than the point, the system is in charge ordering state favorably.
    First-principles study of electronic structure and magnetic properties of Sr3Fe2O5 oxide
    Mavlanjan Rahman(买吾兰江·热合曼) and Jiuyang He(何久洋)
    Chin. Phys. B, 2021, 30 (11):  117107.  DOI: 10.1088/1674-1056/abfa06
    Abstract ( 439 )   HTML ( 1 )   PDF (1229KB) ( 60 )  
    We investigate the electronic structure and magnetic properties of layered compound Sr3Fe2O5 based on first-principles calculations in the framework of density functional theory with GGA+U method. Under high pressure, the ladder-type layered structure of Sr3Fe2O5 is transformed into the infinite layered structure accompanied by a transition from G-type anti-ferromagnetic (AFM) insulator to ferromagnetic (FM) metal and a spin transition from S=2 to S=1. We reproduce these transformations in our calculations and give a clear physical interpretation.
    Self-assembly 2D plasmonic nanorice film for surface-enhanced Raman spectroscopy
    Tingting Liu(柳婷婷), Chuanyu Liu(刘船宇), Jialing Shi(石嘉玲), Lingjun Zhang(张玲君), Xiaonan Sun(孙晓楠), and Yingzhou Huang(黄映洲)
    Chin. Phys. B, 2021, 30 (11):  117301.  DOI: 10.1088/1674-1056/abefc4
    Abstract ( 425 )   HTML ( 2 )   PDF (1501KB) ( 37 )  
    As an ultrasensitive sensing technology, the application of surface enhanced Raman spectroscopy (SERS) is one interesting topic of nano-optics, which has huge application prospectives in plenty of research fields. In recent years, the bottleneck in SERS application could be the fabrication of SERS substrate with excellent enhancement. In this work, a two-dimensional (2D) Ag nanorice film is fabricated by self-assembly method as a SERS substrate. The collected SERS spectra of various molecules on this 2D plasmonic film demonstrate quantitative detection could be performed on this SERS substrate. The experiment data also demonstrate this 2D plasmonic film consisted of anisotropic nanostructures has no obvious SERS polarization dependence. The simulated electric field distribution points out the SERS enhancement comes from the surface plasmon coupling between nanorices. And the SERS signals is dominated by molecules adsorbed at different regions of nanorice surface at various wavelengths, which could be a good near IR SERS substrate for bioanalysis. Our work not only enlarges the surface plasmon properties of metal nanostructure, but also exhibits the good application prospect in SERS related fields.
    Abnormal phenomenon of source-drain current of AlGaN/GaN heterostructure device under UV/visible light irradiation
    Yue-Bo Liu(柳月波), Jun-Yu Shen(沈俊宇), Jie-Ying Xing(邢洁莹), Wan-Qing Yao(姚婉青), Hong-Hui Liu(刘红辉), Ya-Qiong Dai(戴雅琼), Long-Kun Yang(杨隆坤), Feng-Ge Wang(王风格), Yuan Ren(任远), Min-Jie Zhang(张敏杰), Zhi-Sheng Wu(吴志盛), Yang Liu(刘扬), and Bai-Jun Zhang(张佰君)
    Chin. Phys. B, 2021, 30 (11):  117302.  DOI: 10.1088/1674-1056/abfa07
    Abstract ( 604 )   HTML ( 0 )   PDF (1845KB) ( 27 )  
    We report an abnormal phenomenon that the source-drain current (ID) of AlGaN/GaN heterostructure devices decreases under visible light irradiation. When the incident light wavelength is 390 nm, the photon energy is less than the band gaps of GaN and AlGaN whereas it can causes an increase of ID. Based on the UV light irradiation, a decrease of ID can still be observed when turning on the visible light. We speculate that this abnormal phenomenon is related to the surface barrier height, the unionized donor-like surface states below the surface Fermi level and the ionized donor-like surface states above the surface Fermi level. For visible light, its photon energy is less than the surface barrier height of the AlGaN layer. The electrons bound in the donor-like surface states below the Fermi level are excited and trapped by the ionized donor-like surface states between the Fermi level and the conduction band of AlGaN. The electrons trapped in ionized donor-like surface states show a long relaxation time, and the newly ionized donor-like surface states below the surface Fermi level are filled with electrons from the two-dimensional electron gas (2DEG) channel at AlGaN/GaN interface, which causes the decrease of ID. For the UV light, when its photon energy is larger than the surface barrier height of the AlGaN layer, electrons in the donor-like surface states below the Fermi level are excited to the conduction band and then drift into the 2DEG channel quickly, which cause the increase of ID.
    Alpha particle detector with planar double Schottky contacts directly fabricated on semi-insulating GaN:Fe template
    Qun-Si Yang(羊群思), Qing Liu(刘清), Dong Zhou(周东), Wei-Zong Xu(徐尉宗), Yi-Wang Wang(王宜望), Fang-Fang Ren(任芳芳), and Hai Lu(陆海)
    Chin. Phys. B, 2021, 30 (11):  117303.  DOI: 10.1088/1674-1056/abff44
    Abstract ( 456 )   HTML ( 0 )   PDF (997KB) ( 71 )  
    Alpha particle radiation detectors with planar double Schottky contacts (DSC) are directly fabricated on 5-μm-thick epitaxial semi-insulating (SI) GaN:Fe film with resistivity higher than 1×108Ω·cm. Under 10 V bias, the detector exhibits a low dark current of less than 5.0×10-11 A at room-temperature, which increases at higher temperatures. Linear behavior in the semi-log reverse current-voltage plot suggests that Poole-Frenkel emission is the dominant carrier leakage mechanism at high bias. Distinct double-peak characteristics are observed in the energy spectrum of alpha particles regardless of bias voltage. The energy resolution of the SI-GaN based detector is determined to be ~ 8.6% at the deposited energy of 1.209 MeV with a charge collection efficiency of ~ 81.7%. At a higher temperature of 90 ℃, the measured full width at half maximum (FWHM) rises to 235 keV with no shift of energy peak position, which proves that the GaN detector has potential to work stably in high temperature environment. This study provides a possible route to fabricate the low cost GaN-based alpha particle detector with reasonable performance.
    Electronic structures and topological properties of TeSe2 monolayers Hot!
    Zhengyang Wan(万正阳), Hao Huan(郇昊), Hairui Bao(鲍海瑞), Xiaojuan Liu(刘晓娟), and Zhongqin Yang(杨中芹)
    Chin. Phys. B, 2021, 30 (11):  117304.  DOI: 10.1088/1674-1056/ac2489
    Abstract ( 754 )   HTML ( 4 )   PDF (2793KB) ( 471 )  
    The successfully experimental fabrication of two-dimensional Te monolayer films [Phys. Rev. Lett. 119 106101 (2017)] has promoted the researches on the group-VI monolayer materials. In this work, the electronic structures and topological properties of a group-VI binary compound of TeSe2 monolayers are studied based on the density functional theory and Wannier function method. Three types of structures, namely, α-TeSe2, β-TeSe2, and γ-TeSe2, are proposed for the TeSe2 monolayer among which the α-TeSe2 is found being the most stable. All the three structures are semiconductors with indirect band gaps. Very interestingly, the γ-TeSe2 monolayer becomes a quantum spin Hall (QSH) insulator with a global nontrivial energy gap of 0.14 eV when a 3.5% compressive strain is applied. The opening of the global band gap is understood by the competition between the decrease of the local band dispersion and the weakening of the interactions between the Se px, py orbitals and Te px, py orbitals during the process. Our work realizes topological states in the group-VI monolayers and promotes the potential applications of the materials in spintronics and quantum computations.
    Pure spin-current diode based on interacting quantum dot tunneling junction
    Zhengzhong Zhang(张正中), Min Yu(余敏), Rui Bo(薄锐), Chao Wang(王超), and Hao Liu(刘昊)
    Chin. Phys. B, 2021, 30 (11):  117305.  DOI: 10.1088/1674-1056/abfbd8
    Abstract ( 321 )   HTML ( 0 )   PDF (636KB) ( 94 )  
    A magnetic field-controlled spin-current diode is theoretically proposed, which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes. By applying a spin bias VS across the junction, a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy exists. More interestingly, if we applied an external magnetic field on the quantum dot, we observed a clear asymmetry in the spectrum of spin current IS as a function of spin bias, while the charge current always decays to zero in the Coulomb blockade regime. Such asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias, while the net charge through the device is almost zero. Different from the traditional charge current diode, this design can change the polarity direction and rectifying ability by adjusting the external magnetic field, which is very convenient. This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.
    Design, fabrication, and characterization of Ti/Au transition-edge sensor with different dimensions of suspended beams
    Hong-Jun Zhang(张宏俊), Ji Wen(文继), Zhao-Hong Mo(莫钊洪), Hong-Rui Liu(刘鸿瑞), Xiao-Dong Wang(汪小东), Zhong-Hua Xiong(熊忠华), Jin-Wen Zhang(张锦文), and Mao-Bing Shuai(帅茂兵)
    Chin. Phys. B, 2021, 30 (11):  117401.  DOI: 10.1088/1674-1056/abff20
    Abstract ( 295 )   HTML ( 0 )   PDF (2368KB) ( 58 )  
    For photon detection, superconducting transition-edge sensor (TES) micro-calorimeters are excellent energy-resolving devices. In this study, we report our recent work in developing Ti-/Au-based TES. The Ti/Au TES devices were designed and implemented with a thickness ratio of 1:1 and different suspended structures using micromachining technology. The characteristics were evaluated and analyzed, including surface morphology, 3D deformation of suspended Ti/Au TES device structure, I-V characteristics, and low-temperature superconductivity. The results showed that the surface of Ti/Au has good homogeneity and the surface roughness of Ti/Au is significantly increased compared with the substrate. The structure of Ti/Au bilayer film significantly affects the deformation of suspended devices, but the deformation does not affect the I-V characteristics of the devices. For devices with the Ti/Au bilayer (150μm×150μm) and beams (100μm×25μm), the transition temperature (Tc) is 253 mK with a width of 6 mK, and the value of the temperature sensitivity α is 95.1.
    Exact solution of an integrable quantum spin chain with competing interactions
    Jian Wang(王健), Yi Qiao(乔艺), Junpeng Cao(曹俊鹏), and Wen-Li Yang(杨文力)
    Chin. Phys. B, 2021, 30 (11):  117501.  DOI: 10.1088/1674-1056/abfa0a
    Abstract ( 368 )   HTML ( 0 )   PDF (494KB) ( 38 )  
    We construct an integrable quantum spin chain that includes the nearest-neighbor, next-nearest-neighbor, chiral three-spin couplings, Dzyloshinsky-Moriya interactions and unparallel boundary magnetic fields. Although the interactions in bulk materials are isotropic, the spins nearby the boundary fields are polarized, which induce the anisotropic exchanging interactions of the first and last bonds. The U(1) symmetry of the system is broken because of the off-diagonal boundary reflections. Using the off-diagonal Bethe ansatz, we obtain an exact solution to the system. The inhomogeneous T-Q relation and Bethe ansatz equations are given explicitly. We also calculate the ground state energy. The method given in this paper provides a general way to construct new integrable models with certain interesting interactions.
    Antiferromagnetic spin dynamics in exchanged-coupled Fe/GdFeO3 heterostructure
    Na Li(李娜), Jin Tang(汤进), Lei Su(苏磊), Ya-Jiao Ke(柯亚娇), Wei Zhang(张伟), Zong-Kai Xie(谢宗凯), Rui Sun(孙瑞), Xiang-Qun Zhang(张向群), Wei He(何为), and Zhao-Hua Cheng(成昭华)
    Chin. Phys. B, 2021, 30 (11):  117502.  DOI: 10.1088/1674-1056/abf3b7
    Abstract ( 408 )   HTML ( 1 )   PDF (994KB) ( 166 )  
    We investigate the ultrafast spin dynamics of an antiferromagnet in a ferromagnet/antiferromagnet heterostructure Fe/GdFeO3 via an all-optical method. After laser irradiation, the terahertz spin precession is hard to be excited in a bare GdFeO3 without spin reorientation phase but efficiently in Fe/GdFeO3. Both quasi-ferromagnetic and impurity modes, as well as a phonon mode, are observed. We attribute it to the optical modification of interfacial exchange coupling between Fe and GdFeO3. Moreover, the excitation efficiency of dynamics can be modified significantly via the pump laser influence. Our results elucidate that the interfacial exchange coupling is a feasible stimulation to efficiently excite terahertz spin dynamics in antiferromagnets. It will expand the exploration of terahertz spin dynamics for antiferromagnet-based opto-spintronic devices.
    Intrinsic two-dimensional multiferroicity in CrNCl2 monolayer
    Wei Shen(沈威), Yuanhui Pan(潘远辉), Shengnan Shen(申胜男), Hui Li(李辉), Siyuan Nie(聂思媛), and Jie Mei(梅杰)
    Chin. Phys. B, 2021, 30 (11):  117503.  DOI: 10.1088/1674-1056/ac0787
    Abstract ( 341 )   HTML ( 0 )   PDF (1200KB) ( 86 )  
    Two-dimensional multiferroics, which simultaneously possess ferroelectricity and magnetism in a single phase, are well-known to possess great potential applications in nanoscale memories and spintronics. On the basis of first-principles calculations, a CrNCl2 monolayer is reported as an intrinsic multiferroic. The CrNCl2 has an antiferromagnetic ground state, with a Néel temperature of about 88 K, and it exhibits an in-plane spontaneous polarization of 200 pC/m. The magnetic moments of CrNCl2 mainly come from the dxy orbital of the Cr cation, but the plane of the dxy orbital is perpendicular to the direction of the ferroelectric polarization, which hardly suppresses the occurrence of ferroelectricity. Therefore, the multiferroic exits in the CrNCl2. In addition, like CrNCl2, the CrNBr2 is an intrinsic multiferroic with antiferromagnetic-ferroelectric ground state while CrNI2 is an intrinsic multiferroic with ferromagnetic-ferroelectric ground state. These findings enrich the multiferroics in the two-dimensional system and enable a wide range of applications in nanoscale devices.
    RAPID COMMUNICATION
    Realizing Majorana fermion modes in the Kitaev model
    Lu Yang(杨露), Jia-Xing Zhang(张佳星), Shuang Liang(梁爽), Wei Chen(陈薇), and Qiang-Hua Wang(王强华)
    Chin. Phys. B, 2021, 30 (11):  117504.  DOI: 10.1088/1674-1056/ac229a
    Abstract ( 528 )   HTML ( 0 )   PDF (1583KB) ( 193 )  
    We study the possibility to realize a Majorana zero mode that is robust and may be easily manipulated for braiding in quantum computing in the ground state of the Kitaev model in this work. To achieve this we first apply a uniform [111] magnetic field to the gapless Kitaev model and turn the Kitaev model to an effective p+ip topological superconductor of spinons. We then study possible vortex binding in such system to a topologically trivial spot in the ground state. We consider two cases in the system: one is a vacancy and the other is a fully polarized spin. We show that in both cases, the system binds a vortex with the defect and a robust Majorana zero mode in the ground state at a weak uniform [111] magnetic field. The distribution and asymptotic behavior of these Majorana zero modes are studied. The Majorana zero modes in both cases decay exponentially in space, and are robust against local perturbations and other Majorana zero modes far away, which makes them promising candidates for braiding in topological quantum computing.
    Structure and frustrated magnetism of the two-dimensional triangular lattice antiferromagnet Na2BaNi(PO4)2
    Fei Ding(丁飞), Yongxiang Ma(马雍翔), Xiangnan Gong(公祥南), Die Hu(胡蝶), Jun Zhao(赵俊), Lingli Li(李玲丽), Hui Zheng(郑慧), Yao Zhang(张耀), Yongjiang Yu(于永江), Lichun Zhang(张立春), Fengzhou Zhao(赵风周), and Bingying Pan(泮丙营)
    Chin. Phys. B, 2021, 30 (11):  117505.  DOI: 10.1088/1674-1056/abff1d
    Abstract ( 568 )   HTML ( 2 )   PDF (860KB) ( 196 )  
    A new frustrated triangular lattice antiferromagnet Na2BaNi(PO4)2 was synthesized by high temperature flux method. The two-dimensional triangular lattice is formed by the Ni2+ ions with S =1. Its magnetism is highly anisotropic with the Weiss constants θCW =-6.615 K (Hc) and -43.979 K (H||c). However, no magnetic ordering is present down to 0.3 K, reflecting strong geometric spin frustration. Our heat capacity measurements show substantial residual magnetic entropy existing below 0.3 K at zero field, implying the presence of low energy spin excitations. These results indicate that Na2BaNi(PO4)2 is a potential spin liquid candidate with spin-1.
    Observation of magnetoresistance in CrI3/graphene van der Waals heterostructures
    Yu-Ting Niu(牛宇婷), Xiao Lu(鲁晓), Zhong-Tai Shi(石钟太), and Bo Peng(彭波)
    Chin. Phys. B, 2021, 30 (11):  117506.  DOI: 10.1088/1674-1056/ac1e1d
    Abstract ( 505 )   HTML ( 8 )   PDF (1106KB) ( 274 )  
    Two-dimensional ferromagnetic van der Waals (2D vdW) heterostructures have opened new avenues for creating artificial materials with unprecedented electrical and optical functions beyond the reach of isolated 2D atomic layered materials, and for manipulating spin degree of freedom at the limit of few atomic layers, which empower next-generation spintronic and memory devices. However, to date, the electronic properties of 2D ferromagnetic heterostructures still remain elusive. Here, we report an unambiguous magnetoresistance behavior in CrI3/graphene heterostructures, with a maximum magnetoresistance ratio of 2.8%. The magnetoresistance increases with increasing magnetic field, which leads to decreasing carrier densities through Lorentz force, and decreases with the increase of the bias voltage. This work highlights the feasibilities of applying two-dimensional ferromagnetic vdW heterostructures in spintronic and memory devices.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Oxygen vacancy control of electrical, optical, and magnetic properties of Fe0.05Ti0.95O2 epitaxial films
    Qing-Tao Xia(夏清涛), Zhao-Hui Li(李召辉), Le-Qing Zhang(张乐清), Feng-Ling Zhang(张凤玲), Xiang-Kun Li(李祥琨), Heng-Jun Liu(刘恒均), Fang-Chao Gu(顾方超), Tao Zhang(张涛), Qiang Li(李强), and Qing-Hao Li(李庆浩)
    Chin. Phys. B, 2021, 30 (11):  117701.  DOI: 10.1088/1674-1056/ac078e
    Abstract ( 315 )   HTML ( 0 )   PDF (1160KB) ( 55 )  
    High-quality Fe-doped TiO2 films are epitaxially grown on MgF2 substrates by pulsed laser deposition. The x-ray diffraction and Raman spectra prove that they are of pure rutile phase. High-resolution transmission electron microscopy (TEM) further demonstrates that the epitaxial relationship between rutile-phased TiO2 and MgF2 substrates is 110 TiO22. The room temperature ferromagnetism is detected by alternative gradient magnetometer. By increasing the ambient oxygen pressure, magnetization shows that it decreases monotonically while absorption edge shows a red shift. The transport property measurement demonstrates a strong correlation between magnetization and carrier concentration. The influence of ambient oxygen pressure on magnetization can be well explained by a modified bound magnetization polarization model.
    TOPICAL REVIEW—Optical field manipulation
    Photonic-plasmonic hybrid microcavities: Physics and applications
    Hongyu Zhang(张红钰), Wen Zhao(赵闻), Yaotian Liu(刘耀天), Jiali Chen(陈佳丽), Xinyue Wang(王欣月), and Cuicui Lu(路翠翠)
    Chin. Phys. B, 2021, 30 (11):  117801.  DOI: 10.1088/1674-1056/ac0db3
    Abstract ( 476 )   HTML ( 3 )   PDF (4257KB) ( 275 )  
    Photonic-plasmonic hybrid microcavities, which possess a higher figure of merit Q/V (the ratio of quality factor to mode volume) than that of pure photonic microcavities or pure plasmonic nano-antennas, play key roles in enhancing light-matter interaction. In this review, we summarize the typical photonic-plasmonic hybrid microcavities, such as photonic crystal microcavities combined with plasmonic nano-antenna, whispering gallery mode microcavities combined with plasmonic nano-antenna, and Fabry-Perot microcavities with plasmonic nano-antenna. The physics and applications of each hybrid photonic-plasmonic system are illustrated. The recent developments of topological photonic crystal microcavities and topological hybrid nano-cavities are also introduced, which demonstrates that topological microcavities can provide a robust platform for the realization of nanophotonic devices. This review can bring comprehensive physical insights of the hybrid system, and reveal that the hybrid system is a good platform for realizing strong light-matter interaction.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    On the structural and optical properties investigation of annealed Zn nanorods in the oxygen flux
    Fatemeh Abdi
    Chin. Phys. B, 2021, 30 (11):  117802.  DOI: 10.1088/1674-1056/abf4ba
    Abstract ( 268 )   HTML ( 0 )   PDF (3526KB) ( 45 )  
    Zn nano rods were produced on glass substrates using oblique angle deposition method at different deposition angles. For oxidation, the samples were placed in a furnace under oxygen flux. AFM and FESEM images were used to morphology analysis of the structures. The results showed that with increasing the angle of deposition, the grain size decreases and the porosity of the structures increases. XRD pattern and XPS depth profile analysis were used to crystallography and oxide thickness investigations, respectively. The XRD results confirmed oxide phase formation, and the XPS results analyzed the oxide layer thickness. The result showed that as the deposition angle of the nanorods increases, the thickness of the oxide layer increases. The reason for the increase in the thickness of the oxide layer with increasing deposition angle was investigated and attributed to the increase in the porosity of the thin films. The optical spectra of the structures for p polarized light at 10° incident light angle were obtained using single beam spectrophotometer in the 300 nm to 1000 nm wavelengths. The results showed that the formed structures although annealed in oxygen flux, tend to behave like metal. To calculate the optical constant of the structures, the reverse homogenization theory was used and the void fraction and complex refractive index of the structures were obtained. Finally, by calculating permittivity and optical conductivity of the structures, their changes with the deposition angle were investigated.
    Retrieval of the effective constitutive parameters from metamaterial absorbers
    Shaomei Shi(石邵美), Xiaojing Qiao(乔小晶), Shuo Liu(刘朔), and Weinan Liu(刘卫南)
    Chin. Phys. B, 2021, 30 (11):  117803.  DOI: 10.1088/1674-1056/abff27
    Abstract ( 322 )   HTML ( 2 )   PDF (2141KB) ( 67 )  
    The equivalent medium theory of metamaterials provides a way to obtain their effective constitutive parameters. However, because of its non-reciprocity, the complexity of the electromagnetic coupling, and a metallic bottom layer, it has been challenging to retrieve them from a metamaterial absorber. In this paper, we propose a method without any approximation to obtain them, in which the non-reciprocity and the strong electromagnetic coupling are included. Compared with the three methods such as symmetric metamaterial method, asymmetric metamaterial method and metasurface method, our method can reveal the metamaterial absorber's electrical and magnetic resonance and show its electromagnetic coupling coefficients. To deal with a metamaterial absorber with a metallic bottom layer, four corners of the metallic bottom layer in the unit cell are removed, making it possible to retrieve the electromagnetic parameters. Surprisingly, these results show that the metamaterial absorber with a metallic bottom layer in our example operates in a negative refraction state at the half absorption frequencies, which helps further understand the absorbing mechanism of these metamaterial absorbers.
    Photoemission oscillation in epitaxially grown van der Waals β-In2Se3/WS2 heterobilayer bubbles
    Jiyu Dong(董继宇), Kang Lin(林康), Congpu Mu(牟从普), Zhiyan Jia(贾智研), Jin Xu(徐瑾), Anmin Nie(聂安民), Bochong Wang(王博翀), Jianyong Xiang(向建勇), Fusheng Wen(温福昇), Kun Zhai(翟昆), Tianyu Xue(薛天宇), and Zhongyuan Liu(柳忠元)
    Chin. Phys. B, 2021, 30 (11):  117901.  DOI: 10.1088/1674-1056/ac272f
    Abstract ( 359 )   HTML ( 0 )   PDF (2070KB) ( 134 )  
    Thin films of millimeter-scale continuous monolayer WS2 have been grown on SiO2/Si substrate, followed by the deposition of β-In2Se3 crystals on monolayer WS2 to prepare In2Se3/WS2 van de Waals heterostructures by a two-step chemical vapor deposition (CVD) method. After the growth of In2Se3 at elevated temperatures, high densities of In2Se3/WS2 heterostructure bubbles with monolayer to multilayer β-In2Se3 crystals atop are observed. Fluorescence of the resultant β-In2Se3/WS2 heterostructure is greatly enhanced in intensity upon the formation of bubbles, which are evidenced by the Newton's rings in optical image owing to constructive and destructive interference. In photoluminescence (PL) mapping images of monolayer β-In2Se3/monolayer WS2 heterobilayer bubble, significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference. However, oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam. The oscillatory mechanism of PL is further verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber. In addition, redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure of bubbles.
    INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    Effect of nitrogen gas flow and growth temperature on extension of GaN layer on Si
    Jian-Kai Xu(徐健凯), Li-Juan Jiang(姜丽娟), Qian Wang(王茜), Quan Wang(王权), Hong-Ling Xiao(肖红领), Chun Feng(冯春), Wei Li(李巍), and Xiao-Liang Wang(王晓亮)
    Chin. Phys. B, 2021, 30 (11):  118101.  DOI: 10.1088/1674-1056/abff30
    Abstract ( 478 )   HTML ( 0 )   PDF (1911KB) ( 122 )  
    The effect of nitrogen flow and growth temperature on extension of GaN on Si substrate has been studied. By increasing the nitrogen flow whose outlet is located in the center of the MOCVD (metal-organic chemical vapor deposition) gas/particle screening flange and by increasing the growth temperature of HT-AlN and AlGaN buffer layers near the primary flat of the wafer, the GaN layer has extended more adequately on Si substrate. In the meantime, the surface morphology has been greatly improved. Both the AlN and GaN crystal quality uniformity has been improved. X-ray diffraction results showed that the GaN (0002) XRD FWHMs (full width at half maximum) decreased from 579 arcsec~ 1655 arcsec to around 420 arcsec.
    Degradation and its fast recovery in a-IGZO thin-film transistors under negative gate bias stress
    Jianing Guo(郭佳宁), Dongli Zhang(张冬利), Mingxiang Wang(王明湘), and Huaisheng Wang(王槐生)
    Chin. Phys. B, 2021, 30 (11):  118102.  DOI: 10.1088/1674-1056/ac05aa
    Abstract ( 425 )   HTML ( 0 )   PDF (1026KB) ( 59 )  
    A new type of degradation phenomena featured with increased subthreshold swing and threshold voltage after negative gate bias stress (NBS) is observed for amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs), which can recover in a short time. After comparing with the degradation phenomena under negative bias illumination stress (NBIS), positive bias stress (PBS), and positive bias illumination stress (PBIS), degradation mechanisms under NBS is proposed to be the generation of singly charged oxygen vacancies ($V_{\mathrm{o}}^{+}$) in addition to the commonly reported doubly charged oxygen vacancies ($V_{\mathrm{o}}^{2+}$). Furthermore, the NBS degradation phenomena can only be observed when the transfer curves after NBS are measured from the negative gate bias to the positive gate bias direction due to the fast recovery of $V_{\mathrm{o}}^{+}$ under positive gate bias. The proposed degradation mechanisms are verified by TCAD simulation.
    RAPID COMMUNICATION
    Tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber
    Xu Cheng(程旭), Xu Zhou(周旭), Chen Huang(黄琛), Can Liu(刘灿), Chaojie Ma(马超杰), Hao Hong(洪浩), Wentao Yu(于文韬), Kaihui Liu(刘开辉), and Zhongfan Liu(刘忠范)
    Chin. Phys. B, 2021, 30 (11):  118103.  DOI: 10.1088/1674-1056/ac11d0
    Abstract ( 558 )   HTML ( 0 )   PDF (756KB) ( 158 )  
    Optical fiber temperature sensors have been widely employed in enormous areas ranging from electric power industry, medical treatment, ocean dynamics to aerospace. Recently, graphene optical fiber temperature sensors attract tremendous attention for their merits of simple structure and direct power detecting ability. However, these sensors based on transfer techniques still have limitations in the relatively low sensitivity or distortion of the transmission characteristics, due to the unsuitable Fermi level of graphene and the destruction of fiber structure, respectively. Here, we propose a tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber (Gr-PCF) with the non-destructive integration of graphene into the holes of PCF. This hybrid structure promises the intact fiber structure and transmission mode, which efficiently enhances the temperature detection ability of graphene. From our simulation, we find that the temperature sensitivity can be electrically tuned over four orders of magnitude and achieve up to ~ 3.34×10-3 dB/(cm·℃) when the graphene Fermi level is ~ 35 meV higher than half the incident photon energy. Additionally, this sensitivity can be further improved by ~ 10 times through optimizing the PCF structure (such as the fiber hole diameter) to enhance the light-matter interaction. Our results provide a new way for the design of the highly sensitive temperature sensors and broaden applications in all-fiber optoelectronic devices.
    INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    Suppression of ion migration in perovskite materials by pulse-voltage method Hot!
    Xue-Yan Wang(王雪岩), Hu Wang(王虎), Luo-Ran Chen(陈烙然), Yu-Chuan Shao(邵宇川), and Jian-Da Shao(邵建达)
    Chin. Phys. B, 2021, 30 (11):  118104.  DOI: 10.1088/1674-1056/ac248d
    Abstract ( 476 )   HTML ( 2 )   PDF (1398KB) ( 204 )  
    Hybrid halide perovskites have great potential for applications in optoelectronic devices. However, the typical ion migration in perovskite could lead to the non-repeatability of electrical measurement, instability of material, and degradation of device performance. The basic current-voltage behavior of perovskite materials is intricate due to the mixed electronic-ionic characteristic, which is still poorly understood in these semiconductors. Developing novel measurement schematic is a promising solution to obtain the intrinsic electrical performance without the interference of ion migration. Herein, we explore the pulse-voltage (PV) method on methylammonium lead tribromide single crystals to protect the device from the ion migration. A guideline is summarized through the analysis of measurement history and condition parameters. The influence of the ion migration on current-voltage measurement, such as repeatability and hysteresis loop, is under controlled. An application of the PV method is demonstrated on the activation energy of conductivity. The abruption of activation energy still exists near the phase transition temperature despite the ion migration is excluded by the PV method, introducing new physical insight on the current-voltage behavior of perovskite materials. The guideline on PV method will be beneficial for measuring halide perovskite materials and developing optoelectronic applications with new technique schematic.
    High adsorption and separation performance ofCO2 over N2 in azo-based (N=N) pillar[6]arene supramolecular organic frameworks
    Yong-Chao Jiang(姜永超), Gui-Xia Li(李桂霞), Gui-Feng Yu(于桂凤), Juan Wang(王娟), Shu-Lai Huang(黄树来), and Guo-Liang Xu(徐国亮)
    Chin. Phys. B, 2021, 30 (11):  118105.  DOI: 10.1088/1674-1056/ac05b5
    Abstract ( 353 )   HTML ( 0 )   PDF (877KB) ( 61 )  
    Azo-based pillar[6]arene supramolecular organic frameworks are reported for CO2 and N2 adsorption and separation by density functional theory and grand canonical Monte-Carlo simulation. Azo-based pillar[6]arene provides suitable environment for CO2 adsorption and selectivity. The adsorption and selectivity results show that introducing azo groups can effectively improve CO2 adsorption and selectivity over N2, and both CO2 adsorption and CO2 selectivity over N2 follow the sequence pillar[6]arene_N4 > pillar[6]arene_N2 > pillar[6]arene. Pillar[6]arene_N4 exhibits CO2 adsorption capacity of ~ 1.36 mmol/g, and superior selectivity of CO2 over N2 of ~ 116.75 with equal molar fraction at 1 bar (1 bar=105 Pa) and 298 K. Interaction analysis confirms that both the Coulomb and van der Waals interactions between CO2 with pillar[6]arene frameworks are greater than that of N2. The stronger affinity of CO2 with pillar[6]arene_N4 than other structures and the larger isosteric heat differences between CO2 and N2 rendered pillar[6]arene_N4 to present the high CO2 adsorption capacity and high CO2 selectivity over N2. Our results highlight the potential of azo-functionalization as an excellent means to improve pillar[6]arene for CO2 capture and separation.
    Steady and transient behavior of perylene under high pressure
    Ting-Ting Wang(王亭亭), Yu Zhang(张宇), Hong-Yu Tu(屠宏宇), Lu Han(韩露), Ji-Chao Cheng(程基超), Xin Wang(王鑫), Fang-Fei Li(李芳菲), Ling-Yun Pan(潘凌云), and Tian Cui(崔田)
    Chin. Phys. B, 2021, 30 (11):  118201.  DOI: 10.1088/1674-1056/abf923
    Abstract ( 396 )   HTML ( 0 )   PDF (1312KB) ( 50 )  
    Pressure can reduce the distances among atoms, thereby modifying the overall optical characteristics of molecules. In this article, the excited state behavior of perylene is carefully observed under isotropic pressure and non-complexing condition. In a steady state, absorption peak shows red shift and spectral width are broadened with pressure increasing, which is ascribed to the π-electron delocalization between molecules. In a transient state, the transition dynamics presents a wavelike tendency with pressure increasing because the shift of self-tapping exciton state is contrary to that of Y-state with pressure increasing. The results conduce to understanding the influence of inter-molecule interaction on excited state behavior with inter-molecule distance decreasing, which contributes to studying the materials under extreme condition.
    Theoretical investigation of fluorescence changes caused bymethanol bridge based on ESIPT reaction
    Xinglei Zhang(张星蕾), Lixia Zhu(朱丽霞), Zhengran Wang(王正然), Bifa Cao(曹必发), Qiao Zhou(周悄), You Li(李尤), Bo Li(栗博), Hang Yin(尹航), and Ying Shi(石英)
    Chin. Phys. B, 2021, 30 (11):  118202.  DOI: 10.1088/1674-1056/abf131
    Abstract ( 374 )   HTML ( 0 )   PDF (2031KB) ( 84 )  
    The different fluorescence behavior caused by the excited state proton transfer in 3-hydroxy-4-pyridylisoquinoline (2a) compound has been theoretically investigated. Our calculation results illustrate that the 2a monomer in tetrahydrofuran solvent would not occur proton transfer spontaneously, while the 2a complex in methanol (MeOH) solvent can undergo an asynchronous excited state intramolecular proton transfer (ESIPT) process. The result was confirmed by analyzing the related structural parameters, infrared vibration spectrum and reduced density gradient isosurfaces. Moreover, the potential curves revealed that with the bridging of single MeOH molecular the energy barrier of ESIPT was modulated effectively. It was distinctly reduced to 4.80 kcal/mol in 2a-MeOH complex from 25.01 kcal/mol in 2a monomer. Accordingly, the ESIPT process induced a fluorochromic phenomenon with the assistant of proton-bridge. The elucidation of the mechanism of solvent discoloration will contribute to the design and synthesis of fluorogenic dyes as environment-sensitive probes.
    A novel multifunctional electronic calibration kit integrated by MEMS SPDT switches
    Shan-Shan Wang(王姗姗), Qian-Nan Wu(吴倩楠), Yue-Sheng Gao(高跃升), Jian-Gang Yu(余建刚), Qian-Long Cao(曹钎龙), Lu-Lu Han(韩路路), and Meng-Wei Li(李孟委)
    Chin. Phys. B, 2021, 30 (11):  118501.  DOI: 10.1088/1674-1056/abf12b
    Abstract ( 491 )   HTML ( 0 )   PDF (1473KB) ( 90 )  
    Design and simulation results of a novel multifunctional electronic calibration kit based on microelectromechanical system (MEMS) single-pole double-throw (SPDT) switches are presented in this paper. The short-open-load-through (SOLT) calibration states can be completed simultaneously by using the MEMS electronic calibration, and the electronic calibrator can be reused 106 times. The simulation results show that this novel electronic calibration can be used in a frequency range of 0.1 GHz-20 GHz, the return loss is less than 0.18 dB and 0.035 dB in short-circuit and open-circuit states, respectively, and the insertion loss in through (thru) state is less than 0.27 dB. On the other hand, the size of this novel calibration kit is only 6 mm×2.8 mm×0.8 mm. Our results demonstrate that the calibrator with integrated radio-frequency microelectromechanical system (RF MEMS) switches can not only provide reduced size, loss, and calibration cost compared with traditional calibration kit but also improves the calibration accuracy and efficiency. It has great potential applications in millimeter-wave measurement and testing technologies, such as device testing, vector network analyzers, and RF probe stations.
    Light-controlled pulsed x-ray tube with photocathode
    Hao Xuan(宣浩), Yong-An Liu(刘永安), Peng-Fei Qiang(强鹏飞), Tong Su(苏桐), Xiang-Hui Yang(杨向辉), Li-Zhi Sheng(盛立志), and Bao-Sheng Zhao(赵宝升)
    Chin. Phys. B, 2021, 30 (11):  118502.  DOI: 10.1088/1674-1056/abff1e
    Abstract ( 378 )   HTML ( 1 )   PDF (2389KB) ( 130 )  
    Unstable mechanical structure, low energy efficiency, and cooling requirements limit the application of conventional x-ray tubes based on filament as cathode in several academic areas. In this paper, we demonstrate a light-controlled pulsed x-ray tube using multialkali cathode as electron generator. The photocathode active area of the light controlled x-ray tube is 13.2 cm2 (41 mm in diameter), which provides high photoelectron-emitting efficiency up to 0.288 mA/lm in 460-nm LED and 2.37-mA maximum tube current. Furthermore, the modulation ability from 1 kHz to 100 kHz of the x-ray tube is tested. The results suggest that the light-controlled pulsed x-ray tube has easy modulation and short x-ray pulse properties and is promising to be the next generation x-ray tube with wide applications in medical radiation therapy as well as the calibration for detectors and scintillators.
    RAPID COMMUNICATION
    Improved blue quantum dot light-emitting diodes via chlorine passivated ZnO nanoparticle layer
    Xiangwei Qu(瞿祥炜), Jingrui Ma(马精瑞), Siqi Jia(贾思琪), Zhenghui Wu(吴政辉), Pai Liu(刘湃), Kai Wang(王恺), and Xiao-Wei Sun(孙小卫)
    Chin. Phys. B, 2021, 30 (11):  118503.  DOI: 10.1088/1674-1056/ac22a3
    Abstract ( 614 )   HTML ( 3 )   PDF (1458KB) ( 125 )  
    In blue quantum dot light emitting diodes (QLEDs), electron injection is insufficient, which would degrade device efficiency and stability. Herein, we employ chlorine passivated ZnO nanoparticles as electron transport layer to facilitate electron injection into QDs effectively. Moreover, it suppresses exciton quenching at the QD/ZnO interface by blocking charge transfer channel. As a result, the maximum external quantum efficiency of blue QLED was increased from 2.55% to 4.60%, and the operation lifetime of blue QLED was nearly 4 times longer than that of the control device. Our work indicates that election injection plays an important role in blue QLED efficiency and stability.
    TOPICAL REVIEW—Two-dimensional magnetic materials and devices
    Magnetic two-dimensional van der Waals materials forspintronic devices
    Yu Zhang(张雨), Hongjun Xu(许洪军), Jiafeng Feng(丰家峰), Hao Wu(吴昊), Guoqiang Yu(于国强), and Xiufeng Han(韩秀峰)
    Chin. Phys. B, 2021, 30 (11):  118504.  DOI: 10.1088/1674-1056/ac2808
    Abstract ( 619 )   HTML ( 3 )   PDF (3012KB) ( 622 )  
    Magnetic two-dimensional (2D) van der Waals (vdWs) materials and their heterostructures attract increasing attention in the spintronics community due to their various degrees of freedom such as spin, charge, and energy valley, which may stimulate potential applications in the field of low-power and high-speed spintronic devices in the future. This review begins with introducing the long-range magnetic order in 2D vdWs materials and the recent progress of tunning their properties by electrostatic doping and stress. Next, the proximity-effect, current-induced magnetization switching, and the related spintronic devices (such as magnetic tunnel junctions and spin valves) based on magnetic 2D vdWs materials are presented. Finally, the development trend of magnetic 2D vdWs materials is discussed. This review provides comprehensive understandings for the development of novel spintronic applications based on magnetic 2D vdWs materials.
    INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    Any-polar resistive switching behavior in Ti-intercalated Pt/Ti/HfO2/Ti/Pt device
    Jin-Long Jiao(焦金龙), Qiu-Hong Gan(甘秋宏), Shi Cheng(程实), Ye Liao(廖晔), Shao-Ying Ke(柯少颖), Wei Huang(黄巍), Jian-Yuan Wang(汪建元), Cheng Li(李成), and Song-Yan Chen(陈松岩)
    Chin. Phys. B, 2021, 30 (11):  118701.  DOI: 10.1088/1674-1056/abf34e
    Abstract ( 442 )   HTML ( 0 )   PDF (2526KB) ( 50 )  
    The special any-polar resistive switching mode includes the coexistence and stable conversion between the unipolar and the bipolar resistive switching mode under the same compliance current. In the present work, the any-polar resistive switching mode is demonstrated when thin Ti intercalations are introduced into both sides of Pt/HfO2/Pt RRAM device. The role of the Ti intercalations contributes to the fulfillment of the any-polar resistive switching working mechanism, which lies in the filament constructed by the oxygen vacancies and the effective storage of the oxygen ion at both sides of the electrode interface.
    Optical strong coupling in hybrid metal-graphene metamaterial for terahertz sensing
    Ling Xu(徐玲), Yun Shen(沈云), Liangliang Gu(顾亮亮), Yin Li(李寅), Xiaohua Deng(邓晓华), Zhifu Wei(魏之傅), Jianwei Xu(徐建伟), and Juncheng Cao(曹俊诚)
    Chin. Phys. B, 2021, 30 (11):  118702.  DOI: 10.1088/1674-1056/abfb58
    Abstract ( 441 )   HTML ( 1 )   PDF (1793KB) ( 117 )  
    We propose a terahertz hybrid metamaterial composed of subwavelength metallic slits and graphene plasmonic ribbons for sensing application. This special design can cause the interaction between the plasmon resonances of the metallic slits and graphene ribbons, giving rise to a strong coupling effect and Rabi splitting. Intricate balancing in the strong coupling region can be perturbed by the carrier concentration of graphene, which is subject to the analyte on its surface. Thereby, the detection of analyte can be reflected as a frequency shift of resonance in terahertz transmission spectra. The result shows that this sensor can achieve a theoretical detection limit of 325 electrons or holes per square micrometer. Meanwhile, it also works well as a refractive index sensor with the frequency sensitivity of 485 GHz/RIU. Our results may contribute to design of ultra-micro terahertz sensors.
    Nonlinear signal transduction network with multistate
    Han-Yu Jiang(姜寒玉) and Jun He(何军)
    Chin. Phys. B, 2021, 30 (11):  118703.  DOI: 10.1088/1674-1056/ac21bf
    Abstract ( 344 )   HTML ( 0 )   PDF (5988KB) ( 123 )  
    Signal transduction is an important and basic mechanism to cell life activities. The stochastic state transition of receptor induces the release of signaling molecular, which triggers the state transition of other receptors. It constructs a nonlinear sigaling network, and leads to robust switchlike properties which are critical to biological function. Network architectures and state transitions of receptor affect the performance of this biological network. In this work, we perform a study of nonlinear signaling on biological polymorphic network by analyzing network dynamics of the Ca2+-induced Ca2+ release (CICR) mechanism, where fast and slow processes are involved and the receptor has four conformational states. Three types of networks, Erdös-Rényi (ER) network, Watts-Strogatz (WS) network, and BaraBási-Albert (BA) network, are considered with different parameters. The dynamics of the biological networks exhibit different patterns at different time scales. At short time scale, the second open state is essential to reproduce the quasi-bistable regime, which emerges at a critical strength of connection for all three states involved in the fast processes and disappears at another critical point. The pattern at short time scale is not sensitive to the network architecture. At long time scale, only monostable regime is observed, and difference of network architectures affects the results more seriously. Our finding identifies features of nonlinear signaling networks with multistate that may underlie their biological function.
    Viewing the noise propagation mechanism in a unidirectional transition cascade from the perspective of stability
    Qi-Ming Pei(裴启明), Bin-Qian Zhou(周彬倩), Yi-Fan Zhou(周祎凡), Charles Omotomide Apata, and Long Jiang(蒋龙)
    Chin. Phys. B, 2021, 30 (11):  118704.  DOI: 10.1088/1674-1056/ac0ee7
    Abstract ( 415 )   HTML ( 0 )   PDF (642KB) ( 53 )  
    Noise and noise propagation are inevitable and play a constructive role in various biological processes. The stability of cell homeostasis is also a critical issue. In the unidirectional transition cascade of colon cells, stem cells (SCs) are the source. They differentiate into transit-amplifying cells (TACs), and TACs differentiate into fully differentiated cells (FDCs). Two differentiation processes are irreversible. The stability factor is introduced so that the noise propagation mechanism from the perspective of stability is studied according to the noise propagation formulas. It is found that the value of the stability factor corresponding to the minimum noise in FDCs may be the best choice to enable colon cells to maintain high stability and low noise of the cascade. Moreover, for the source cell, the total noise only includes intrinsic noise; for the downstream cell with self-proliferation capability, the total noise mainly depends on its intrinsic noise and transmitted noise from upstream cells, and its intrinsic noise is dominant. For the downstream cell without self-proliferation capability, the total noise is mainly determined by transmitted noises from upstream cells, and there is a minimum value. This work provides a new approach for studying the mechanism of noise propagation while considering the stability of cell homeostasis in biological systems.
    ERRATUM
    Erratum to “Floquet bands and photon-induced topological edge states of graphene nanoribbons”
    Weijie Wang(王威杰), Xiaolong Lü(吕小龙), and Hang Xie(谢航)
    Chin. Phys. B, 2021, 30 (11):  119901.  DOI: 10.1088/1674-1056/ac2b1e
    Abstract ( 409 )   HTML ( 0 )   PDF (474KB) ( 26 )  
    Figures 2(a) and 2(b) in the original paper [Chin. Phys. B 30 066701 (2021)] are replaced by the new ones.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 30, No. 11

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