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Topological phase in one-dimensional Rashba wire Sa-Ke Wang(汪萨克), Jun Wang(汪军), Jun-Feng Liu(刘军丰) Chin. Phys. B, 2016, 25 (7): 077305.   DOI: 10.1088/1674-1056/25/7/077305 Abstract （203770）   HTML    PDF （397KB）（199283）       Knowledge map    We study the possible topological phase in a one-dimensional (1D) quantum wire with an oscillating Rashba spin-orbital coupling in real space. It is shown that there are a pair of particle-hole symmetric gaps forming in the bulk energy band and fractional boundary states residing in the gap when the system has an inversion symmetry. These states are topologically nontrivial and can be characterized by a quantized Berry phase ±π or nonzero Chern number through dimensional extension. When the Rashba spin-orbital coupling varies slowly with time, the system can pump out 2 charges in a pumping cycle because of the spin flip effect. This quantized pumping is protected by topology and is robust against moderate disorders as long as the disorder strength does not exceed the opened energy gap.

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Generation of valley pump currents in silicene John Tombe Jada Marcellino, Mei-Juan Wang(王美娟), Sa-Ke Wang(汪萨克) Chin. Phys. B, 2019, 28 (1): 017204.   DOI: 10.1088/1674-1056/28/1/017204 Abstract （348871）   HTML    PDF （433KB）（345574）       Knowledge map    We propose a workable scheme for generating a bulk valley pump current in a silicene-based device which consists of two pumping regions characterized by time-dependent strain and staggered potentials, respectively. In a one-dimension model, we show that a pure valley current can be generated, in which the two valley currents have the same magnitude but flow in opposite directions. Besides, the pumped valley current is quantized and maximized when the Fermi energy of the system locates in the bandgap opened by the two pumping potentials. Furthermore, the valley current can be finely controlled by tuning the device parameters. Our results are useful for the development of valleytronic devices based on two-dimensional materials.

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Spin and valley filter in strain engineered silicene Wang Sa-Ke (汪萨克), Wang Jun (汪军) Chin. Phys. B, 2015, 24 (3): 037202.   DOI: 10.1088/1674-1056/24/3/037202 Abstract （321762）   HTML    PDF （643KB）（319436）       Knowledge map    The realization of a perfect spin or valley filtering effect in two-dimensional graphene-like materials is one of the fundamental objectives in spintronics and valleytronics. For this purpose, we study spin- and valley-dependent transport in a silicene system with spatially alternative strains. It is found that due to the valley-opposite gauge field induced by the strain, the strained silicene with a superlattice structure exhibits an angle-resolved valley and spin filtering effect when the spin-orbit interaction is considered. When the interaction that breaks the time reversal symmetry is introduced, such as the spin or valley dependent staggered magnetization, the system is shown to be a perfect spin and valley half metal in which only one spin and valley species is allowed to transport. Our findings are helpful to design both spintronic and valleytronic devices based on silicene.

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Spin and valley half metal induced by staggered potential and magnetization in silicene Wang Sa-Ke (汪萨克), Tian Hong-Yu (田宏玉), Yang Yong-Hong (杨永宏), Wang Jun (汪军) Chin. Phys. B, 2014, 23 (1): 017203.   DOI: 10.1088/1674-1056/23/1/017203 Abstract （301100）      PDF （639KB）（303424）       Knowledge map    We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin–orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices.

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Spin gapless armchair graphene nanoribbons under magnetic field and uniaxial strain Hou Hai-Ping (侯海平), Xie Yue-E (谢月娥), Chen Yuan-Ping (陈元平), Ouyang Tao (欧阳滔), Ge Qing-Xia (葛青霞), Zhong Jian-Xin (钟建新) Chin. Phys. B, 2013, 22 (8): 087303.   DOI: 10.1088/1674-1056/22/8/087303 Abstract （829）      PDF （654KB）（5578）       Knowledge map    Using Green's function method, we investigate the spin transport properties of armchair graphene nanoribbons (AGNRs) under magnetic field and uniaxial strain. Our results show that it is very difficult to transform narrow AGNRs directly from semiconductor to spin gapless semiconductors (SGS) by applying magnetic fields. However, as a uniaxial strain is exerted on the nanoribbons, the AGNRs can transform to SGS by a small magnetic field. The combination mode between magnetic field and uniaxial strain displays a nonmonotonic arch-pattern relationship. In addition, we find that the combination mode is associated with the widths of nanoribbons, which exhibits group behaviors.

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Developing improved measures of non-Gaussianity and Gaussianity for quantum states based on normalized Hilbert-Schmidt distance Shaohua Xiang(向少华), Shanshan Li(李珊珊), and Xianwu Mi(米贤武) Chin. Phys. B, 2023, 32 (5): 050309.   DOI: 10.1088/1674-1056/acb0bd Abstract （263）   HTML （3）    PDF （1151KB）（1801）       Knowledge map    Non-Gaussianity of quantum states is a very important source for quantum information technology and can be quantified by using the known squared Hilbert-Schmidt distance recently introduced by Genoni et al. (Phys. Rev. A 78 042327 (2007)). It is, however, shown that such a measure has many imperfects such as the lack of the swapping symmetry and the ineffectiveness evaluation of even Schrödinger-cat-like states with small amplitudes. To deal with these difficulties, we propose an improved measure of non-Gaussianity for quantum states and discuss its properties in detail. We then exploit this improved measure to evaluate the non-Gaussianities of some relevant single-mode non-Gaussian states and multi-mode non-Gaussian entangled states. These results show that our measure is reliable. We also introduce a modified measure for Gaussianity following Mandilara and Cerf (Phys. Rev. A 86 030102(R) (2012)) and establish a conservation relation of non-Gaussianity and Gaussianity of a quantum state.

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An overview of quantum error mitigation formulas Dayue Qin(秦大粤), Xiaosi Xu(徐晓思), and Ying Li(李颖) Chin. Phys. B, 2022, 31 (9): 090306.   DOI: 10.1088/1674-1056/ac7b1e Abstract （686）   HTML （6）    PDF （953KB）（1941）       Knowledge map    Minimizing the effect of noise is essential for quantum computers. The conventional method to protect qubits against noise is through quantum error correction. However, for current quantum hardware in the so-called noisy intermediate-scale quantum (NISQ) era, noise presents in these systems and is too high for error correction to be beneficial. Quantum error mitigation is a set of alternative methods for minimizing errors, including error extrapolation, probabilistic error cancellation, measurement error mitigation, subspace expansion, symmetry verification, virtual distillation, etc. The requirement for these methods is usually less demanding than error correction. Quantum error mitigation is a promising way of reducing errors on NISQ quantum computers. This paper gives a comprehensive introduction to quantum error mitigation. The state-of-art error mitigation methods are covered and formulated in a general form, which provides a basis for comparing, combining and optimizing different methods in future work.

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Twisted and coiled bamboo artificial muscles for moisture responsive torsional and tensile actuation Xiaoyu Hu(胡晓宇), Xueqi Leng(冷雪琪), Tianjiao Jia(贾天娇), and Zunfeng Liu(刘遵峰) Chin. Phys. B, 2020, 29 (11): 118103.   DOI: 10.1088/1674-1056/abbbda Abstract （1431）   HTML    PDF （1197KB）（7290）       Knowledge map    Smart textiles responding to the ambient environment like temperature, humidity, and light are highly desirable to improve the comfortability and realize multifunctions. The bamboo yarn has merits like air permeability, biodegradability, and excellent heat dissipation performance, but it has not been prepared for responsive materials and smart textiles. In this paper, the moisture-responsive twisted bamboo yarns were plied to form a self-balanced torsional actuator and wrapped around a mandrel to form a coil, followed by water immersion and evaporation to fix the shape and serve as a tensile actuator. A torsional actuation of 64.4°⋅ mm−1 was realized for the twisted actuator in 4.2 s; a maximum elongation of 133% or contraction of 50% was achieved for a coiled tensile actuator with good cyclability. The porous structure of bamboo yarns helped improve the water absorbance speed and decrease the response time of moisture. The self-balanced two-ply physical structure and reversible generation of chemical phase after soaking in aqueous solution fixed internal stress and provided good cyclability. With the unique properties including aqueous water-induced shape fixation and moisture-induced actuation, the application of tensile actuation of bamboo yarns was demonstrated, showing promising prospects on smart textiles.

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The complex band structure for armchair graphene nanoribbons Zhang Liu-Jun(张留军) and Xia Tong-Sheng(夏同生) Chin. Phys. B, 2010, 19 (11): 117105.   DOI: 10.1088/1674-1056/19/11/117105 Abstract （1508）      PDF （741KB）（2727）       Knowledge map    Using a tight binding transfer matrix method, we calculate the complex band structure of armchair graphene nanoribbons. The real part of the complex band structure calculated by the transfer matrix method fits well with the bulk band structure calculated by a Hermitian matrix. The complex band structure gives extra information on carrier's decay behaviour. The imaginary loop connects the conduction and valence band, and can profoundly affect the characteristics of nanoscale electronic device made with graphene nanoribbons. In this work, the complex band structure calculation includes not only the first nearest neighbour interaction, but also the effects of edge bond relaxation and the third nearest neighbour interaction. The band gap is classified into three classes. Due to the edge bond relaxation and the third nearest neighbour interaction term, it opens a band gap for N=3M-1. The band gap is almost unchanged for N=3M+1, but decreased for N=3M. The maximum imaginary wave vector length provides additional information about the electrical characteristics of graphene nanoribbons, and is also classified into three classes.

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Fundamental study towards a better understanding of low pressure radio-frequency plasmas for industrial applications Yong-Xin Liu(刘永新), Quan-Zhi Zhang(张权治), Kai Zhao(赵凯), Yu-Ru Zhang(张钰如), Fei Gao(高飞),Yuan-Hong Song(宋远红), and You-Nian Wang(王友年) Chin. Phys. B, 2022, 31 (8): 085202.   DOI: 10.1088/1674-1056/ac7551 Abstract （658）   HTML （0）    PDF （11486KB）（1632）       Knowledge map    Two classic radio-frequency (RF) plasmas, i.e., the capacitively and the inductively coupled plasmas (CCP and ICP), are widely employed in material processing, e.g., etching and thin film deposition, etc. Since RF plasmas are usually operated in particular circumstances, e.g., low pressures (mTorr-Torr), high-frequency electric field (13.56 MHz-200 MHz), reactive feedstock gases, diverse reactor configurations, etc., a variety of physical phenomena, e.g., electron resonance heating, discharge mode transitions, striated structures, standing wave effects, etc., arise. These physical effects could significantly influence plasma-based material processing. Therefore, understanding the fundamental processes of RF plasma is not only of fundamental interest, but also of practical significance for the improvement of the performance of the plasma sources. In this article, we review the major progresses that have been achieved in the fundamental study on the RF plasmas, and the topics include 1) electron heating mechanism, 2) plasma operation mode, 3) pulse modulated plasma, and 4) electromagnetic effects. These topics cover the typical issues in RF plasma field, ranging from fundamental to application.

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Molecular dynamics simulation of self-diffusion coefficients for liquid metals Ju Yuan-Yuan (巨圆圆), Zhang Qing-Ming (张庆明), Gong Zi-Zheng (龚自正), Ji Guang-Fu (姬广富) Chin. Phys. B, 2013, 22 (8): 083101.   DOI: 10.1088/1674-1056/22/8/083101 Abstract （825）      PDF （347KB）（2753）       Knowledge map    The temperature-dependent coefficients of self-diffusion for liquid metals are simulated by molecular dynamics methods based on the embedded-atom-method (EAM) potential function. The simulated results show that a good inverse linear relation exists between the natural logarithm of self-diffusion coefficients and temperature, though the results in the literature vary somewhat, due to the employment of different potential functions. The estimated activation energy of liquid metals obtained by fitting the Arrhenius formula is close to the experimental data. The temperature-dependent shear-viscosities obtained from the Stokes-Einstein relation in conjunction with the results of molecular dynamics simulation are generally consistent with other values in the literature.

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Superconductivity and unconventional density waves in vanadium-based kagome materials AV3Sb5 Hui Chen(陈辉), Bin Hu(胡彬), Yuhan Ye(耶郁晗), Haitao Yang(杨海涛), and Hong-Jun Gao(高鸿钧) Chin. Phys. B, 2022, 31 (9): 097405.   DOI: 10.1088/1674-1056/ac7f95 Abstract （724）   HTML （6）    PDF （6290KB）（852）       Knowledge map    Recently, the discovery of vanadium-based kagome metal AV3Sb5 (A= K, Rb, Cs) has attracted great interest in the field of superconductivity due to the coexistence of superconductivity, non-trivial surface state and multiple density waves. In this topical review, we present recent works of superconductivity and unconventional density waves in vanadium-based kagome materials AV3Sb5. We start with the unconventional charge density waves, which are thought to correlate to the time-reversal symmetry-breaking orders and the unconventional anomalous Hall effects in AV3Sb5. Then we discuss the superconductivity and the topological band structure. Next, we review the competition between the superconductivity and charge density waves under different conditions of pressure, chemical doping, thickness, and strains. Finally, the experimental evidence of pseudogap pair density wave is discussed.

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Statistical distribution of Chinese names Guo Jin-Zhong(郭金忠), Chen Qing-Hua(陈清华), and Wang You-Gui(王有贵) Chin. Phys. B, 2011, 20 (11): 118901.   DOI: 10.1088/1674-1056/20/11/118901 Abstract （1485）      PDF （553KB）（2515）       Knowledge map    This paper studies the statistical characteristics of Chinese surnames, first names and full names based on a credible sample. The distribution of Chinese surnames, unlike that in any other countries, shows an exponential pattern in the top part and a power-law pattern in the tail part. The distributions of Chinese first names and full names have the characteristics of a power law with different exponents. Finally, the interrelation of the first name and the surname is demonstrated by using a computer simulation and an exhibition of the name network. Chinese people take the surname into account when they choose a first name for somebody.

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Parallel optimization of underwater acoustic models: A survey Zi-jie Zhu(祝子杰), Shu-qing Ma(马树青), Xiao-Qian Zhu(朱小谦), Qiang Lan(蓝强), Sheng-Chun Piao(朴胜春), and Yu-Sheng Cheng(程玉胜) Chin. Phys. B, 2022, 31 (10): 104301.   DOI: 10.1088/1674-1056/ac7ccc Abstract （540）   HTML （5）    PDF （1765KB）（1191）       Knowledge map    Underwater acoustic models are effective tools for simulating underwater sound propagation. More than 50 years of research have been conducted on the theory and computational models of sound propagation in the ocean. Unfortunately, underwater sound propagation models were unable to solve practical large-scale three-dimensional problems for many years due to limited computing power and hardware conditions. Since the mid-1980s, research on high performance computing for acoustic propagation models in the field of underwater acoustics has flourished with the emergence of high-performance computing platforms, enabling underwater acoustic propagation models to solve many practical application problems that could not be solved before. In this paper, the contributions of research on high-performance computing for underwater acoustic propagation models since the 1980s are thoroughly reviewed and the possible development directions for the future are outlined.

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Quantum interferometer with two-mode squeezed vacuum：Ŝz2 measurement Zhang Yuan-Ming (张渊明), Li Xin-Wei (李昕伟), Jin Guang-Ri (金光日) Chin. Phys. B, 2013, 22 (11): 114206.   DOI: 10.1088/1674-1056/22/11/114206 Abstract （783）      PDF （262KB）（741）       Knowledge map    Quantum interferometric strategy with input two-mode squeezed vacuum [Phys. Rev. Lett. 104 103602] is reexamined for both parity and Ŝz2 measurements. Unlike the previous scheme, we find that phase sensitivity obtained with the Ŝz2 measurement is minimized at phase origin, which may be useful to estimate a small phase shift at high precision. For the phase deviated from zero, the sensitivity increases more slowly than that of the parity detection.

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Finesse measurement for high-power optical enhancement cavity Xin-Yi Lu(陆心怡), Xing Liu(柳兴), Qi-Li Tian(田其立), Huan Wang(王焕), Jia-Jun Wang(汪嘉俊), and Li-Xin Yan(颜立新) Chin. Phys. B, 2024, 33 (1): 014205.   DOI: 10.1088/1674-1056/acd8ad Abstract （290）   HTML （1）    PDF （1176KB）（808）       Knowledge map    Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity (OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range (FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down (CRD) method, the rapidly swept-frequency (SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.

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Quantum spin Hall effect in a square-lattice model under a uniform magnetic field Guo Huai-Ming(郭怀明) and Feng Shi-Ping(冯世平) Chin. Phys. B, 2012, 21 (7): 077303.   DOI: 10.1088/1674-1056/21/7/077303 Abstract （1594）      PDF （517KB）（2063）       Knowledge map    We study a toy square-lattice model under a uniform magnetic field. Using the Landauer--B黷tiker formula, we calculate the transport properties of the system on a two-terminal, a four-terminal, and a six-terminal device. We find that the quantum spin Hall (QSH) effect appears in energy ranges where the spin-up and spin-down subsystems have different filling factors. We also study the robustness of the resulting QSH effect and find that it is robust when the Fermi levels of both spin subsystems are far away from the energy plateaus but is fragile when the Fermi level of any spin subsystem is near the energy plateaus. These results provide an example of QSH effect with the physical origin other than time-reversal (TR) preserving spin-orbit coupling (SOC).

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Band structures of strained kagome lattices Luting Xu(徐露婷) and Fan Yang(杨帆) Chin. Phys. B, 2024, 33 (2): 027101.   DOI: 10.1088/1674-1056/ad0291 Abstract （355）   HTML （11）    PDF （1764KB）（510）       Knowledge map    Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands. We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential. It is found that the Dirac points move with applied strain. Furthermore, the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction, forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction. Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

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Review of cavity optomechanical cooling Liu Yong-Chun (刘永椿), Hu Yu-Wen (胡毓文), Wong Chee Wei (黄智维), Xiao Yun-Feng (肖云峰) Chin. Phys. B, 2013, 22 (11): 114213.   DOI: 10.1088/1674-1056/22/11/114213 Abstract （1158）      PDF （1300KB）（1703）       Knowledge map    Quantum manipulation of macroscopic mechanical systems is of great interest in both fundamental physics and applications ranging from high-precision metrology to quantum information processing. For these purposes, a crucial step is to cool the mechanical system to its quantum ground state. In this review, we focus on the cavity optomechanical cooling, which exploits the cavity enhanced interaction between optical field and mechanical motion to reduce the thermal noise. Recent remarkable theoretical and experimental efforts in this field have taken a major step forward in preparing the motional quantum ground state of mesoscopic mechanical systems. This review first describes the quantum theory of cavity optomechanical cooling, including quantum noise approach and covariance approach; then, the up-to-date experimental progresses are introduced. Finally, new cooling approaches are discussed along the directions of cooling in the strong coupling regime and cooling beyond the resolved sideband limit. Cited: Web of science (54)

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A review on the design of ternary logic circuits Xiao-Yuan Wang(王晓媛), Chuan-Tao Dong(董传涛), Zhi-Ru Wu(吴志茹), and Zhi-Qun Cheng(程知群) Chin. Phys. B, 2021, 30 (12): 128402.   DOI: 10.1088/1674-1056/ac248b Abstract （824）   HTML （6）    PDF （697KB）（1952）       Knowledge map    A multi-valued logic system is a promising alternative to traditional binary logic because it can reduce the complexity, power consumption, and area of circuit implementation. This article briefly summarizes the development of ternary logic and its advantages in digital logic circuits. The schemes, characteristics, and application of ternary logic circuits based on CMOS, CNTFET, memristor, and other devices and processes are reviewed in this paper, providing some reference for the further research and development of ternary logic circuits.