Table of contents

    05 March 2020, Volume 29 Issue 3 Previous issue    Next issue
    SPECIAL TOPIC—Topological semimetals
    Single crystal growth, structural and transport properties of bad metal RhSb2
    D S Wu(吴德胜), Y T Qian(钱玉婷), Z Y Liu(刘子懿), W Wu(吴伟), Y J Li(李延杰), S H Na(那世航), Y T Shao(邵钰婷), P Zheng(郑萍), G Li(李岗), J G Cheng(程金光), H M Weng(翁红明), J L Luo(雒建林)
    Chin. Phys. B, 2020, 29 (3):  037101.  DOI: 10.1088/1674-1056/ab696e
    Abstract ( 366 )   HTML   PDF (1974KB) ( 347 )  
    We have successfully grown an arsenopyrite marcasite type RhSb2 single crystal, and systematically investigated its crystal structure, electrical transport, magnetic susceptibility, heat capacity, and thermodynamic properties. We found that the temperature-dependent resistivity exhibits a bad metal behavior with a board peak around 200 K. The magnetic susceptibility of RhSb2 shows diamagnetism from 300 K to 2 K. The low-temperature specific heat shows a metallic behavior with a quite small electronic specific-heat coefficient. No phase transition is observed in both specific heat and magnetic susceptibility data. The Hall resistivity measurements show that the conduction carriers are dominated by electrons with ne = 8.62×1018 cm-3 at 2 K, and the electron carrier density increases rapidly above 200 K without change sign. Combining with ab-initio band structure calculations, we showed that the unusual peak around 200 K in resistivity is related to the distinct electronic structure of RhSb2. In addition, a large thermopower S(T) about -140 μV/K is observed around 200 K, which might be useful for future thermoelectric applications.
    SPECIAL TOPIC—Advanced calculation & characterization of energy storage materials & devices at multiple scale
    Computational screening of doping schemes forLiTi2(PO4)3 as cathode coating materials
    Yu-Qi Wang(王宇琦), Xiao-Rui Sun(孙晓瑞), Rui-Juan Xiao(肖睿娟), Li-Quan Chen(陈立泉)
    Chin. Phys. B, 2020, 29 (3):  038202.  DOI: 10.1088/1674-1056/ab7186
    Abstract ( 196 )   HTML   PDF (1030KB) ( 257 )  
    In all-solid-state lithium batteries, the impedance at the cathode/electrolyte interface shows close relationship with the cycle performance. Cathode coatings are helpful to reduce the impedance and increase the stability at the interface effectively. LiTi2(PO4)3 (LTP), a fast ion conductor with high ionic conductivity approaching 10-3 S·cm-1, is adopted as the coating materials in this study. The crystal and electronic structures, as well as the Li+ ion migration properties are evaluated for LTP and its doped derivatives based on density functional theory (DFT) and bond valence (BV) method. Substituting part of Ti sites with element Mn, Fe, or Mg in LTP can improve the electronic conductivity of LTP while does not decrease its high ionic conductivity. In this way, the coating materials with both high ionic conductivities and electronic conductivities can be prepared for all-solid-state lithium batteries to improve the ion and electron transport properties at the interface.
    Graphene's photonic and optoelectronic properties-A review
    A J Wirth-Lima, P P Alves-Sousa, W Bezerra-Fraga
    Chin. Phys. B, 2020, 29 (3):  037801.  DOI: 10.1088/1674-1056/ab5fc2
    Abstract ( 194 )   HTML   PDF (6013KB) ( 195 )  
    Due to its remarkable electrical and optical properties, graphene continues to receive more and more attention from researchers around the world. An excellent advantage of graphene is the possibility of controlling its charge density, and consequently, the management of its conductivity and dielectric constant, among other parameters. It is noteworthy that the control of these properties enables the obtaining of new optical/electronic devices, which would not exist based on conventional materials. However, to work in this area of science, it is necessary to have a thorough knowledge regarding the electrical/optical properties of graphene. In this review paper, we show these graphene properties very well detailed.
    Astrocyte and ions metabolism during epileptogenesis: A review for modeling studies
    Meng-Meng Du(独盟盟), Jia-Jia Li(李佳佳), Zhi-Xuan Yuan(袁治轩), Yong-Chen Fan(范永晨), Ying Wu(吴莹)
    Chin. Phys. B, 2020, 29 (3):  038701.  DOI: 10.1088/1674-1056/ab6961
    Abstract ( 130 )   HTML   PDF (726KB) ( 88 )  
    As a large group of cells in a central nervous system, astrocytes have a great influence on ion and energy metabolism in a nervous system. Disorders of neuronal ion and energy metabolism caused by impaired astrocytes play a key role in the pathogenesis of epilepsy. This paper reviews the existing computational models of epileptogenesis resulting from impaired astrocytes and presents several open perspectives with regard to ion and energy metabolism-induced epileptogenesis in a neuron-astrocyte-capillary coupled model.
    Tailoring electronic properties of two-dimensional antimonene with isoelectronic counterparts Hot!
    Ye Zhang(张也), Huai-Hong Guo(郭怀红), Bao-Juan Dong(董宝娟), Zhen Zhu(朱震), Teng Yang(杨腾), Ji-Zhang Wang(王吉章), Zhi-Dong Zhang(张志东)
    Chin. Phys. B, 2020, 29 (3):  037305.  DOI: 10.1088/1674-1056/ab6c4e
    Abstract ( 307 )   HTML   PDF (4721KB) ( 222 )  
    Using ab initio density functional theory calculations, we explore the three most stable structural phases, namely, α, β, and cubic (c) phases, of two-dimensional (2D) antimonene, as well as its isoelectronic counterparts SnTe and InI. We find that the band gap increases monotonically from Sb to SnTe to InI along with an increase in ionicity, independent of the structural phases. The band gaps of this material family cover the entire visible-light energy spectrum, ranging from 0.26 eV to 3.37 eV, rendering them promising candidates for optoelectronic applications. Meanwhile, band-edge positions of these materials are explored and all three types of band alignments can be achieved through properly combining antimonene with its isoelectronic counterparts to form heterostructures. The richness in electronic properties for this isoelectronic material family sheds light on possibilities to tailor the fundamental band gap of antimonene via lateral alloying or forming vertical heterostructures.
    Lump and interaction solutions to the (3+1)-dimensional Burgers equation
    Jian Liu(刘健), Jian-Wen Wu(吴剑文)
    Chin. Phys. B, 2020, 29 (3):  030201.  DOI: 10.1088/1674-1056/ab6964
    Abstract ( 188 )   HTML   PDF (2613KB) ( 110 )  
    The (3+1)-dimensional Burgers equation, which describes nonlinear waves in turbulence and the interface dynamics, is considered. Two types of semi-rational solutions, namely, the lump-kink solution and the lump-two kinks solution, are constructed from the quadratic function ansatz. Some interesting features of interactions between lumps and other solitons are revealed analytically and shown graphically, such as fusion and fission processes.
    Lax pair and vector semi-rational nonautonomous rogue waves fora coupled time-dependent coefficient fourth-order nonlinear Schrödinger system in an inhomogeneous optical fiber
    Zhong Du(杜仲), Bo Tian(田播), Qi-Xing Qu(屈启兴), Xue-Hui Zhao(赵学慧)
    Chin. Phys. B, 2020, 29 (3):  030202.  DOI: 10.1088/1674-1056/ab7442
    Abstract ( 113 )   HTML   PDF (4270KB) ( 93 )  
    Optical fibers are seen in the optical sensing and optical fiber communication. Simultaneous propagation of optical pulses in an inhomogeneous optical fiber is described by a coupled time-dependent coefficient fourth-order nonlinear Schrödinger system, which is discussed in this paper. For such a system, we work out the Lax pair, Darboux transformation, and corresponding vector semi-rational nonautonomous rogue wave solutions. When the group velocity dispersion (GVD) and fourth-order dispersion (FOD) coefficients are the constants, we exhibit the first- and second-order vector semi-rational rogue waves which are composed of the four-petalled rogue waves and eye-shaped breathers. Both the width of the rogue wave along the time axis and temporal separation between the adjacent peaks of the breather decrease with the GVD coefficient or FOD coefficient. With the GVD and FOD coefficients as the linear, cosine, and exponential functions, we respectively present the first- and second-order periodic vector semi-rational rogue waves, first- and second-order asymmetry vector semi-rational rogue waves, and interactions between the eye-shaped breathers and the composite rogue waves.
    Exact solutions of stochastic fractional Korteweg de-Vries equation with conformable derivatives
    Hossam A. Ghany, Abd-Allah Hyder, M Zakarya
    Chin. Phys. B, 2020, 29 (3):  030203.  DOI: 10.1088/1674-1056/ab75c9
    Abstract ( 160 )   HTML   PDF (2008KB) ( 132 )  
    We deal with the Wick-type stochastic fractional Korteweg de-Vries (KdV) equation with conformable derivatives. With the aid of the Exp-function method, white noise theory, and Hermite transform, we produce a novel set of exact soliton and periodic wave solutions to the fractional KdV equation with conformable derivatives. With the help of inverse Hermite transform, we get stochastic soliton and periodic wave solutions of the Wick-type stochastic fractional KdV equation with conformable derivatives. Eventually, by an application example, we show how the stochastic solutions can be given as Brownian motion functional solutions.
    Construction of Laguerre polynomial's photon-added squeezing vacuum state and its quantum properties
    Dao-Ming Lu(卢道明)
    Chin. Phys. B, 2020, 29 (3):  030301.  DOI: 10.1088/1674-1056/ab69e8
    Abstract ( 102 )   HTML   PDF (1734KB) ( 79 )  
    Laguerre polynomial's photon-added squeezing vacuum state is constructed by operation of Laguerre polynomial's photon-added operator on squeezing vacuum state. By making use of the technique of integration within an ordered product of operators, we derive the normalization coefficient and the calculation expression of <ala>. Its statistical properties, such as squeezing, the anti-bunching effect, the sub-Poissonian distribution property, the negativity of Wigner function, etc., are investigated. The influences of the squeezing parameter on quantum properties are discussed. Numerical results show that, firstly, the squeezing effect of the 1-order Laguerre polynomial's photon-added operator exciting squeezing vacuum state is strengthened, but its anti-bunching effect and sub-Poissonian statistical property are weakened with increasing squeezing parameter; secondly, its squeezing effect is similar to that of squeezing vacuum state, but its anti-bunching effect and sub-Poissonian distribution property are stronger than that of squeezing vacuum state. These results show that the operation of Laguerre polynomial's photon-added operator on squeezing vacuum state can enhance its non-classical properties.
    Geometric phase of an open double-quantum-dot system detected by a quantum point contact
    Qian Du(杜倩), Kang Lan(蓝康), Yan-Hui Zhang(张延惠), Lu-Jing Jiang(姜露静)
    Chin. Phys. B, 2020, 29 (3):  030302.  DOI: 10.1088/1674-1056/ab6963
    Abstract ( 133 )   HTML   PDF (604KB) ( 142 )  
    We study theoretically the geometric phase of a double-quantum-dot (DQD) system measured by a quantum point contact (QPC) in the pure dephasing and dissipative environments, respectively. The results show that in these two environments, the coupling strength between the quantum dots has an enhanced impact on the geometric phase during a quasiperiod. This is due to the fact that the expansion of the width of the tunneling channel connecting the two quantum dots accelerates the oscillations of the electron between the quantum dots and makes the length of the evolution path longer. In addition, there is a notable near-zero region in the geometric phase because the stronger coupling between the system and the QPC freezes the electron in one quantum dot and the solid angle enclosed by the evolution path is approximately zero, which is associated with the quantum Zeno effect. For the pure dephasing environment, the geometric phase is suppressed as the dephasing rate increases which is caused only by the phase damping of the system. In the dissipative environment, the geometric phase is reduced with the increase of the relaxation rate which results from both the energy dissipation and phase damping of the system. Our results are helpful for using the geometric phase to construct the fault-tolerant quantum devices based on quantum dot systems in quantum information.
    Reference-frame-independent quantum key distribution with an untrusted source
    Jia-Ji Li(李家骥), Yang Wang(汪洋), Hong-Wei Li(李宏伟), Wan-Su Bao(鲍皖苏)
    Chin. Phys. B, 2020, 29 (3):  030303.  DOI: 10.1088/1674-1056/ab695d
    Abstract ( 148 )   HTML   PDF (461KB) ( 125 )  
    Reference frame independent quantum key distribution (RFI-QKD) allows two legitimate parties to share the common secret keys with the drift of reference frames. In order to reduce the actual requirements of RFI-QKD protocol on light source and make it more suitable for practical applications, this paper gives a specific description of RFI-QKD protocol with an untrusted source and analyzes the practical security of this protocol based on the two-way “plug and play” structure commonly used in practical systems. In addition, we also investigate the performance of RFI-QKD with an untrusted source considering statistical fluctuations based on Chernoff bound. Using simulations, we compare the secret key rate of RFI-QKD with an untrusted source to RFI-QKD with trusted source. The results show that the performance of RFI-QKD with an untrusted source is similar to that of RFI-QKD with trusted source, and the finite data size clearly effects the performance of our protocol.
    Quantum speed limit time of a non-Hermitian two-level system
    Yan-Yi Wang(王彦懿), Mao-Fa Fang(方卯发)
    Chin. Phys. B, 2020, 29 (3):  030304.  DOI: 10.1088/1674-1056/ab6c45
    Abstract ( 115 )   HTML   PDF (590KB) ( 133 )  
    We investigated the quantum speed limit time of a non-Hermitian two-level system for which gain and loss of energy or amplitude are present. Our results show that, with respect to two distinguishable states of the non-Hermitian system, the evolutionary time does not have a nonzero lower bound. The quantum evolution of the system can be effectively accelerated by adjusting the non-Hermitian parameter, as well as the quantum speed limit time can be arbitrarily small even be zero.
    Applicability of coupling strength estimation for linear chains of restricted access
    He Feng(冯赫), Tian-Min Yan(阎天民), Yuhai Jiang(江玉海)
    Chin. Phys. B, 2020, 29 (3):  030305.  DOI: 10.1088/1674-1056/ab6c43
    Abstract ( 123 )   HTML   PDF (905KB) ( 73 )  
    The characterization of an unknown quantum system requires the Hamiltonian identification. The full access to the system, however, is usually restricted, hindering the direct retrieval of the relevant parameters, and a reliable indirect estimation is usually required. In this work, based on the reformulated form of the original algorithm of Burgarth et al. [Phys. Rev. A 79 020305 (2009)], the robustness of the estimation scheme against numerous sources of errors during the actual measurement is analyzed. The scheme is numerically studied for sites with a chain structure, exploring its applicability against observational errors including the limited signal-noise ratio and the finite spectral width. The spectral distribution of the end site is shown to determine the applicability of the method, and reducing the influence from truncated spectral components is critical to realize the robust reconstruction of the coupling strengths.
    Optical complex integration-transform for deriving complex fractional squeezing operator
    Ke Zhang(张科), Cheng-Yu Fan(范承玉), Hong-Yi Fan(范洪义)
    Chin. Phys. B, 2020, 29 (3):  030306.  DOI: 10.1088/1674-1056/ab6dc9
    Abstract ( 105 )   HTML   PDF (316KB) ( 63 )  
    We find a new complex integration-transform which can establish a new relationship between a two-mode operator's matrix element in the entangled state representation and its Wigner function. This integration keeps modulus invariant and therefore invertible. Based on this and the Weyl-Wigner correspondence theory, we find a two-mode operator which is responsible for complex fractional squeezing transformation. The entangled state representation and the Weyl ordering form of the two-mode Wigner operator are fully used in our derivation which brings convenience.
    Dynamics of the plane and solitary waves in a Noguchi network: Effects of the nonlinear quadratic dispersion
    S A T Fonkoua, M S Ngounou, G R Deffo, F B Pelap, S B Yamgoue, A Fomethe
    Chin. Phys. B, 2020, 29 (3):  030501.  DOI: 10.1088/1674-1056/ab696a
    Abstract ( 136 )   HTML   PDF (2230KB) ( 197 )  
    We consider a modified Noguchi network and study the impact of the nonlinear quadratic dispersion on the dynamics of modulated waves. In the semi-discrete limit, we show that the dynamics of these waves are governed by a nonlinear cubic Schrödinger equation. From the graphical analysis of the coefficients of this equation, it appears that the nonlinear quadratic dispersion counterbalances the effects of the linear dispersion in the frequency domain. Moreover, we establish that this nonlinear quadratic dispersion provokes the disappearance of some regions of modulational instability in the dispersion curve compared to the results earlier obtained by Pelap et al. (Phys. Rev. E 91 022925 (2015)). We also find that the nonlinear quadratic dispersion limit considerably affects the nature, stability, and characteristics of the waves which propagate through the system. Furthermore, the results of the numerical simulations performed on the exact equations describing the network are found to be in good agreement with the analytical predictions.
    Dynamics analysis of chaotic maps: From perspective on parameter estimation by meta-heuristic algorithm
    Yue-Xi Peng(彭越兮), Ke-Hui Sun(孙克辉), Shao-Bo He(贺少波)
    Chin. Phys. B, 2020, 29 (3):  030502.  DOI: 10.1088/1674-1056/ab695c
    Abstract ( 112 )   HTML   PDF (2458KB) ( 98 )  
    Chaotic encryption is one of hot topics in cryptography, which has received increasing attention. Among many encryption methods, chaotic map is employed as an important source of pseudo-random numbers (PRNS). Although the randomness and the butterfly effect of chaotic map make the generated sequence look very confused, its essence is still the deterministic behavior generated by a set of deterministic parameters. Therefore, the unceasing improved parameter estimation technology becomes one of potential threats for chaotic encryption, enhancing the attacking effect of the deciphering methods. In this paper, for better analyzing the cryptography, we focus on investigating the condition of chaotic maps to resist parameter estimation. An improved particle swarm optimization (IPSO) algorithm is introduced as the estimation method. Furthermore, a new piecewise principle is proposed for increasing estimation precision. Detailed experimental results demonstrate the effectiveness of the new estimation principle, and some new requirements are summarized for a secure chaotic encryption system.
    The second Hopf bifurcation in lid-driven square cavity
    Tao Wang(王涛), Tiegang Liu(刘铁钢), Zheng Wang(王正)
    Chin. Phys. B, 2020, 29 (3):  030503.  DOI: 10.1088/1674-1056/ab6b15
    Abstract ( 126 )   HTML   PDF (4480KB) ( 70 )  
    To date, there are very few studies on the second Hopf bifurcation in a driven square cavity, although there are intensive investigations focused on the first Hopf bifurcation in literature, due to the difficulties of theoretical analyses and numerical simulations. In this paper, we study the characteristics of the second Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme recently developed by us. We numerically identify the critical Reynolds number of the second Hopf bifurcation located in the interval of (11093.75,11094.3604) by bisection. In addition, we find that there are two dominant frequencies in its spectral diagram when the flow is in the status of the second Hopf bifurcation, while only one dominant frequency is identified if the flow is in the first Hopf bifurcation via the Fourier analysis. More interestingly, the flow phase portrait of velocity components is found to make transition from a regular elliptical closed form for the first Hopf bifurcation to a non-elliptical closed form with self-intersection for the second Hopf bifurcation. Such characteristics disclose flow in a quasi-periodic state when the second Hopf bifurcation occurs.
    Dynamical response of a neuron-astrocyte coupling system under electromagnetic induction and external stimulation
    Zhi-Xuan Yuan(袁治轩), Pei-Hua Feng(冯沛华), Meng-Meng Du(独盟盟), Ying Wu(吴莹)
    Chin. Phys. B, 2020, 29 (3):  030504.  DOI: 10.1088/1674-1056/ab7441
    Abstract ( 145 )   HTML   PDF (6328KB) ( 72 )  
    Previous studies have observed that electromagnetic induction can seriously affect the electrophysiological activity of the nervous system. Considering the role of astrocytes in regulating neural firing, we studied a simple neuron-astrocyte coupled system under electromagnetic induction in response to different types of external stimulation. Both the duration and intensity of the external stimulus can induce different modes of electrical activity in this system, and thus the neuronal firing patterns can be subtly controlled. When the external stimulation ceases, the neuron will continue to fire for a long time and then reset to its resting state. In this study, “delay” is defined as the delayed time from the firing state to the resting state, and it is highly sensitive to changes in the duration or intensity of the external stimulus. Meanwhile, the self-similarity embodied in the aforementioned sensitivity can be quantified by fractal dimension. Moreover, a hysteresis loop of calcium activity in the astrocyte is observed in the specific interval of the external stimulus when the stimulus duration is extended to infinity, since astrocytic calcium or neuron electrical activity in the resting state or during periodic oscillation depends on the initial state. Finally, the regulating effect of electromagnetic induction in this system is considered. It is clarified that the occurrence of “delay” depends purely on the existence of electromagnetic induction. This model can reveal the dynamic characteristics of the neuron-astrocyte coupling system with magnetic induction under external stimulation. These results can provide some insights into the effects of electromagnetic induction and stimulation on neuronal activity.
    Hexagonal arrangement of phospholipids in bilayer membranes
    Xiao-Wei Chen(陈晓伟), Ming-Xia Yuan(元明霞), Han Guo(郭晗), Zhi Zhu(朱智)
    Chin. Phys. B, 2020, 29 (3):  030505.  DOI: 10.1088/1674-1056/ab7187
    Abstract ( 154 )   HTML   PDF (4120KB) ( 72 )  
    The phospholipid membrane plays a key role in myriad biological processes and phenomena, and the arrangement structure of membrane determines its function. However, the molecular arrangement structure of phospholipids in cell membranes is difficult to detect experimentally. On the basis of molecular dynamic simulations both in a non-destructive way and at native environment, we observed and confirmed that the phospholipids self-assemble to a hexagonal arrangement structure under physiological conditions. The underlying mechanism was revealed to be that there are hexagonal arrangement regions with a lower free energy around each lipid molecule. The findings potentially advance the understanding of biological functions of phospholipid bilayers.
    An Yb-fiber frequency comb phase-locked to microwave standard and optical reference Hot!
    Hui-Bo Wang(汪会波), Hai-Nian Han(韩海年), Zi-Yue Zhang(张子越), Xiao-Dong Shao(邵晓东), Jiang-Feng Zhu(朱江峰), Zhi-Yi Wei(魏志义)
    Chin. Phys. B, 2020, 29 (3):  030601.  DOI: 10.1088/1674-1056/ab696d
    Abstract ( 222 )   HTML   PDF (1332KB) ( 138 )  
    We present a fully stabilized Yb-fiber frequency comb locked to a microwave standard and an optical reference separately. The carrier-envelope offset frequency is generated by a standard f-2f interferometer with 40 dB signal-to-noise ratio. The offset frequency and the repetition rate are stabilized simultaneously to the radio frequency reference for more than 30 hours, and the fractional Allan deviation of the comb is the same as the microwave standard of 10-12 at 1 s. Alternatively, the comb is locked to an ultra-stable optical reference at 972 nm using an intracavity electro-optic modulator, exhibiting a residual integrated phase noise of 458 mrad (1 Hz-10 MHz) and an in-loop tracking stability of 1.77×10-18 at 1 s, which is significantly raised by six orders comparing to the case locked to the microwave frequency standard.
    Effects of electron correlation and the Breit interaction on one- and two-electron one-photon transitions in double K hole states of He-like ions (10≤Z≤47)
    Xiaobin Ding(丁晓彬), Cunqiang Wu(吴存强), Mingxin Cao(曹铭欣), Denghong Zhang(张登红), Mingwu Zhang(张明武), Yingli Xue(薛迎利), Deyang Yu(于得洋), Chenzhong Dong(董晨钟)
    Chin. Phys. B, 2020, 29 (3):  033101.  DOI: 10.1088/1674-1056/ab6c51
    Abstract ( 169 )   HTML   PDF (463KB) ( 86 )  
    The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s2 configurations of 11 selected He-like ions (10≤Z≤47) are calculated using the fully relativistic multi-configuration Dirac-Fock method (MCDF). An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of the electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon (TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of the He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.
    Vibronic spectra of aluminium monochloride relevant to circumstellar molecule
    Jian-Gang Xu(徐建刚), Cong-Ying Zhang(张聪颖), Yun-Guang Zhang(张云光)
    Chin. Phys. B, 2020, 29 (3):  033102.  DOI: 10.1088/1674-1056/ab6c46
    Abstract ( 97 )   HTML   PDF (736KB) ( 63 )  
    The A1Π→X1Σ+ transition system of aluminium monochloride is determined by using ab initio quantum chemistry. Based on the multi-reference configuration interaction method in conjugate to the Davidson correction (MRCI+Q), the potential energy curves (PECs) of the three electronic states are obtained. Transition dipole moments (TDMs) and the vibrational energy levels are studied by employing the aug-cc-pwCV5Z-DK basis set with 4220-active space. The rovibrational constants are first determined from the analytic potential by solving the rovibrational Schrödinger equation, and then the spectroscopic constants are determined by fitting the vibrational levels, and these values are well consistent with the experimental data. The effect of spin-orbit coupling (SOC) on the spectra and vibrational properties are evaluated. The results show that the SOC effect has almost no influence on the spectroscopic constants of AlCl molecules. For the A1Π→X1Σ+ transition, the highly diagonalized Frank-Condon factor (FCF) is f00 =0.9988. Additionally, Einstein coefficients and radiative lifetimes are studied, where the vibrational bands include ν"=0-19→ν'=0-9. The ro-vibrational intensity is calculated at a temperature of 296 K, which can have certain astrophysical applications. At present, there is no report on the calculation of AlCl ro-vibrational intensity, so we hope that our results will be useful in analyzing the interstellar AlCl based on the absorption from A1Π→X1Σ+.
    Precise measurement of a weak radio frequency electric field using a resonant atomic probe
    Liping Hao(郝丽萍), Yongmei Xue(薛咏梅), Jiabei Fan(樊佳蓓), Jingxu Bai(白景旭), Yuechun Jiao(焦月春), Jianming Zhao(赵建明)
    Chin. Phys. B, 2020, 29 (3):  033201.  DOI: 10.1088/1674-1056/ab6c49
    Abstract ( 127 )   HTML   PDF (4795KB) ( 83 )  
    We present a precise measurement of a weak radio frequency electric field with a frequency of ≤3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S1/2>, an excited state |6P3/2>, and Rydberg state |nD5/2>. Two radio frequency (RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency (Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of kHz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin=1.36 ±0.04 mV/m for 2.18 GHz coupling |68D5/2>→|69P3/2> transition and 1.33±0.02 mV/m for 1.32 GHz coupling |80D5/2>→|81P3/2> transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding -3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.
    Enhancement of electron-ion recombination rates at low energy range in the heavy ion storage ring CSRm
    Nadir Khan, Zhong-Kui Huang(黄忠魁), Wei-Qiang Wen(汶伟强), Shu-Xing Wang(汪书兴), Han-Bing Wang(汪寒冰), Wan-Lu Ma(马万路), Xiao-Long Zhu(朱小龙), Dong-Mei Zhao(赵冬梅), Li-Jun Mao(冒立军), Jie Li(李杰), Xiao-Ming Ma(马晓明), Mei-Tang Tang(汤梅堂), Da-Yu Yin(殷达钰), Wei-Qing Yang(杨维青), Jian-Cheng Yang(杨建成), You-Jin Yuan(原有进), Lin-Fan Zhu(朱林繁), Xin-Wen Ma(马新文)
    Chin. Phys. B, 2020, 29 (3):  033401.  DOI: 10.1088/1674-1056/ab69eb
    Abstract ( 82 )   HTML   PDF (1094KB) ( 59 )  
    Recombination of Ar14+, Ar15+, Ca16+, and Ni19+ ions with electrons has been investigated at low energy range based on the merged-beam method at the main cooler storage ring CSRm in the Institute of Modern Physics, Lanzhou, China. For each ion, the absolute recombination rate coefficients have been measured with electron-ion collision energies from 0 meV to 1000 meV which include the radiative recombination (RR) and also dielectronic recombination (DR) processes. In order to interpret the measured results, RR cross sections were obtained from a modified version of the semi-classical Bethe and Salpeter formula for hydrogenic ions. DR cross sections were calculated by a relativistic configuration interaction method using the flexible atomic code (FAC) and AUTOSTRUCTURE code in this energy range. The calculated RR + DR rate coefficients show a good agreement with the measured value at the collision energy above 100 meV. However, large discrepancies have been found at low energy range especially below 10 meV, and the experimental results show a strong enhancement relative to the theoretical RR rate coefficients. For the electron-ion collision energy below 1 meV, it was found that the experimentally observed recombination rates are higher than the theoretically predicted and fitted rates by a factor of 1.5 to 3.9. The strong dependence of RR rate coefficient enhancement on the charge state of the ions has been found with the scaling rule of q3.0, reproducing the low-energy recombination enhancement effects found in other previous experiments.
    Cherenkov terahertz radiation from Dirac semimetals surface plasmon polaritons excited by an electron beam
    Tao Zhao(赵陶), Zhenhua Wu(吴振华)
    Chin. Phys. B, 2020, 29 (3):  034101.  DOI: 10.1088/1674-1056/ab6840
    Abstract ( 130 )   HTML   PDF (1335KB) ( 75 )  
    We demonstrate a physical mechanism for terahertz (THz) generation from surface plasmon polaritons (SPPs). In a structure with a bulk Dirac semimetals (BDSs) film deposited on a dielectric substrate, the energy of the asymmetric SPP mode can be significantly enhanced to cross the light line of the substrate due to the SPP-coupling between the interfaces of the film. Therefore, the SPPs can be immediately transformed into Cherenkov radiation without removing the wavevector mismatch. Additionally, the symmetric SPP mode can also be dramatically lifted to cross the substrate light line when a buffer layer with low permittivity relative to the substrate is introduced. In this case, dual-frequency THz radiation from the two SPP modes can be generated simultaneously. The radiation intensity is significantly enhanced by over two orders due to the field enhancement of the SPPs. The radiation frequency can be tuned in the THz frequency regime by adjusting the beam energy and the chemical potential of the BDSs. Our results could find potential applications in developing room temperature, tunable, coherent, and intense THz radiation sources to cover the entire THz band.
    Paraxial propagation of cosh-Airy vortex beams in chiral medium
    Xiao-Jin Yang(杨小锦), Zhen-Sen Wu(吴振森), Tan Qu(屈檀)
    Chin. Phys. B, 2020, 29 (3):  034201.  DOI: 10.1088/1674-1056/ab683f
    Abstract ( 109 )   HTML   PDF (11848KB) ( 112 )  
    Propagation dynamics of the cosh-Airy vortex (CAiV) beams in a chiral medium is investigated analytically with Huygens-Fresnel diffraction integral formula. The results show that the CAiV beams are split into the left circularly polarized vortex (LCPV) beams and the right circularly polarized vortex (RCPV) beams with different propagation trajectories in the chiral medium. We mainly investigate the effect of the cosh parameter on the propagation process of the CAiV beams. The propagation characteristics, including intensity distribution, propagation trajectory, peak intensity, main lobe's intensity, Poynting vector, and angular momentum are discussed in detail. We find that the cosh parameter affects the intensity distribution of the CAiV beams but not its propagation trajectory. As the cosh parameter increases, the distribution areas of the LCPV and RCPV beams become wider, and the side lobe's intensity and peak intensity become larger. Besides, the main lobe's intensity of the LCPV and RCPV beams increase with the increase of the cosh parameter at a farther propagation distance, which is confirmed by the variation trend of the Poynting vector. It is significant that we can vary the cosh parameter to control the intensity distribution, main lobe's intensity, and peak intensity of the CAiV beams without changing the propagation trajectory. Our results may provide some support for applications of the CAiV beams in optical micromanipulation.
    Far-field vector-diffraction of off-axis parabolic mirror under oblique incidence
    Xia-Hui Zeng(曾夏辉), Xi-Yao Chen(陈曦曜)
    Chin. Phys. B, 2020, 29 (3):  034202.  DOI: 10.1088/1674-1056/ab683e
    Abstract ( 129 )   HTML   PDF (6205KB) ( 80 )  
    Based on a full vector-diffraction theory, a detailed theoretical study is carried out, aiming at providing a clear insight into the effects of different focusing and off-axis parabola parameters on far-field vector-diffraction properties of an off-axis parabolic mirror in the presence of misalignments of the incoming beam. The physical origin of these effects is also explored. The results show that the far-field intensity profile is altered by the distortion-, coma-, and astigmatism-like aberrations, which are caused by oblique incidence rather than inherent aberrations for the off-axis configuration. The radius of 90% encircled energy also increases but does not change monotonically with incident beam size increasing, or rather, it first decreases and then increases. The focal shift strongly depends on the effective focal length and oblique incidence angle, but it is almost independent of the beam size, which affects the focusing spot patterns. The intensity distribution produces a higher astigmatic image with off-axis angle increasing. Coma-like aberration starts to become dominant with beam size increasing and results in larger curved propagation trajectory. The incident polarization also affects the intensity distribution. The variation in the Strehl ratio with oblique incidence angle strongly depends on the misalignment direction and beam size as well. In addition, we find that the difference in locus between the catacaustic and the diffraction focus in the meridian is small. But the locus of the sagittal foci is obviously different from the locus of the meridian foci and the catacaustic focus. Moreover, the peak intensity of the sagittal focus is maximum, and the ratio of the peak intensity to that in the meridian plane is approximately 1.5. Understanding these effects is valuable for assessing a practical focused intensity and describing the motion of charged particles under a strong electric field in ultraintense laser-matter interaction.
    Optical enhanced interferometry with two-mode squeezed twin-Fock states and parity detection
    Li-Li Hou(侯丽丽), Shuai Wang(王帅), Xue-Fen Xu(许雪芬)
    Chin. Phys. B, 2020, 29 (3):  034203.  DOI: 10.1088/1674-1056/ab6837
    Abstract ( 134 )   HTML   PDF (578KB) ( 108 )  
    We theoretically investigate the quantum enhanced metrology using two-mode squeezed twin-Fock states and parity detection. Our results indicate that, for a given initial squeezing parameter, compared with the two-mode squeezed vacuum state, both phase sensitivity and resolution can be enhanced when the two-mode squeezed twin-Fock state is considered as an input state of a Mach-Zehnder interferometer. Within a constraint on the total photon number, although the two-mode squeezed vacuum state gives the better phase sensitivity when the phase shift φ to be estimated approaches to zero, the phase sensitivity offered by these non-Gaussian entangled Gaussian states is relatively stable with respect to the phase shift itself. When the phase shift slightly deviates from φ=0, the phase sensitivity can be still enhanced by the two-mode squeezed twin-Fock state over a broad range of the total mean photon number where the phase uncertainty is still below the quantum standard noise limit. Finally, we numerically prove that the quantum Cramér-Rao bound can be approached with the parity detection.
    Dynamic manipulation of probe pulse and coherent generation of beating signals based on tunneling-induced inference in triangular quantum dot molecules
    Nuo Ba(巴诺), Jin-You Fei(费金友), Dong-Fei Li(李东飞), Xin Zhong(钟鑫), Dan Wang(王丹), Lei Wang(王磊), Hai-Hua Wang(王海华), Qian-Qian Bao(鲍倩倩)
    Chin. Phys. B, 2020, 29 (3):  034204.  DOI: 10.1088/1674-1056/ab683d
    Abstract ( 121 )   HTML   PDF (1847KB) ( 98 )  
    We investigate the dynamic propagation of a probe field via the tunneling-induced interference effect in a triple model of quantum dot molecules. By theoretical analysis and numerical simulation, we find that the number of transparency window relate to the energy splitting and the group velocity of probe field can be effectively controlled by the tunneling coupling intensity. In addition, in the process of light storage and retrieval, when the excited states have no energy splitting in the storage stage but opposite values of the energy splitting in the retrieval stage, the beating signals can be generated.
    A low-noise, high-SNR balanced homodyne detector for the bright squeezed state measurement in 1-100 kHz range
    Jin-Rong Wang(王锦荣), Qing-Wei Wang(王庆伟), Long Tian(田龙), Jing Su(苏静), Yao-Hui Zheng(郑耀辉)
    Chin. Phys. B, 2020, 29 (3):  034205.  DOI: 10.1088/1674-1056/ab683b
    Abstract ( 137 )   HTML   PDF (1063KB) ( 132 )  
    We report a low-noise, high-signal-to-noise-ratio (SNR) balanced homodyne detector based on the standard transimpedance amplifier circuit and the inductance and capacitance combination for the measurement of the bright squeezed state in the range from 1 kHz to 100 kHz. A capacitance is mounted at the input end of the AC branch to prevent the DC photocurrent from entering the AC branch and avoid AC branch saturation. By adding a switch at the DC branch, the DC branch can be flexibly turned on and off on different occasions. When the switch is on, the DC output provides a monitor signal for laser beam alignment. When the switch is off, the electronic noise of the AC branch is greatly reduced at audio-frequency band due to immunity to the impedance of the DC branch, hence the SNR of the AC branch is significantly improved. As a result, the electronic noise of the AC branch is close to -125 dBm, and the maximum SNR of the AC branch is 48 dB with the incident power of 8 mW in the range from 1 kHz to 100 kHz. The developed photodetector paves a path for measuring the bright squeezed state at audio-frequency band.
    Evaluation of polarization field in InGaN/GaN multiple quantum well structures by using electroluminescence spectra shift
    Ping Chen(陈平), De-Gang Zhao(赵德刚), De-Sheng Jiang(江德生), Jing Yang(杨静), Jian-Jun Zhu(朱建军), Zong-Shun Liu(刘宗顺), Wei Liu(刘炜), Feng Liang(梁锋), Shuang-Tao Liu(刘双韬), Yao Xing(邢瑶), Li-Qun Zhang(张立群)
    Chin. Phys. B, 2020, 29 (3):  034206.  DOI: 10.1088/1674-1056/ab6967
    Abstract ( 97 )   HTML   PDF (705KB) ( 92 )  
    In order to investigate the inherent polarization intensity in InGaN/GaN multiple quantum well (MQW) structures, the electroluminescence (EL) spectra of three samples with different GaN barrier thicknesses of 21.3 nm, 11.4 nm, and 6.5 nm are experimentally studied. All of the EL spectra present a similar blue-shift under the low-level current injection, and then turns to a red-shift tendency when the current increases to a specific value, which is defined as the turning point. The value of this turning point differs from one another for the three InGaN/GaN MQW samples. Sample A, which has the GaN barrier thickness of 21.3 nm, shows the highest current injection level at the turning point as well as the largest value of blue-shift. It indicates that sample A has the maximum intensity of the polarization field. The red-shift of the EL spectra results from the vertical electron leakage in InGaN/GaN MQWs and the corresponding self-heating effect under the high-level current injection. As a result, it is an effective approach to evaluate the polarization field in the InGaN/GaN MQW structures by using the injection current level at the turning point and the blue-shift of the EL spectra profiles.
    Eigenvalue spectrum analysis for temporal signals of Kerr optical frequency combs based on nonlinear Fourier transform
    Jia Wang(王佳), Ai-Guo Sheng(盛爱国), Xin Huang(黄鑫), Rong-Yu Li(李荣玉), Guang-Qiang He(何广强)
    Chin. Phys. B, 2020, 29 (3):  034207.  DOI: 10.1088/1674-1056/ab683a
    Abstract ( 103 )   HTML   PDF (1102KB) ( 100 )  
    Based on the nonlinear Schrödinger equation (NLSE) with damping, detuning, and driving terms describing the evolution of signals in a Kerr microresonator, we apply periodic nonlinear Fourier transform (NFT) to the study of signals during the generation of the Kerr optical frequency combs (OFCs). We find that the signals in different states, including the Turing pattern, the chaos, the single soliton state, and the multi-solitons state, can be distinguished according to different distributions of the eigenvalue spectrum. Specially, the eigenvalue spectrum of the single soliton pulse is composed of a pair of conjugate symmetric discrete eigenvalues and the quasi-continuous eigenvalue spectrum with eye-like structure. Moreover, we have successfully demonstrated that the number of discrete eigenvalue pairs in the eigenvalue spectrum corresponds to the number of solitons formed in a round-trip time inside the Kerr microresonator. This work shows that some characteristics of the time-domain signal can be well reflected in the nonlinear domain.
    Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect
    Yongxia Zhang(张永霞), Jinhui Yuan(苑金辉), Yuwei Qu(屈玉玮), Xian Zhou(周娴), Binbin Yan(颜玢玢), Qiang Wu(吴强), Kuiru Wang(王葵如), Xinzhu Sang(桑新柱), Keping Long(隆克平), Chongxiu Yu(余重秀)
    Chin. Phys. B, 2020, 29 (3):  034208.  DOI: 10.1088/1674-1056/ab683c
    Abstract ( 113 )   HTML   PDF (654KB) ( 108 )  
    A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber (PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio (ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.
    A compact electro-absorption modulator based on graphene photonic crystal fiber
    Guangwei Fu(付广伟), Ying Wang(王颖), Bilin Wang(王碧霖), Kaili Yang(杨凯丽), Xiaoyu Wang(王晓愚), Xinghu Fu(付兴虎), Wa Jin(金娃), Weihong Bi(毕卫红)
    Chin. Phys. B, 2020, 29 (3):  034209.  DOI: 10.1088/1674-1056/ab6838
    Abstract ( 175 )   HTML   PDF (807KB) ( 94 )  
    A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene-light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by two large semicircular holes, and monolayer graphene is deposited on the two large semicircular holes. By optimizing the structure parameters, a strong graphene-light interaction is obtained. Moreover, the switch on-off point of the modulator is unchangeable, which is only related to the frequency of the incident light. The influence factors of this composite structure have been analyzed. The proposed modulator is compared with other graphene-based modulators, and the results show that it is filled without dielectric spacer. There are some excellent performances, such as an extinction ratio 7 dB of y-polarization mode, 3-dB modulation bandwidth of 70 GHz with small footprint of 205 μm, and a consumption of energy per bit 59 pJ/bit.
    The optical nonreciprocal response based on a four-mode optomechanical system
    Jing Wang(王婧)
    Chin. Phys. B, 2020, 29 (3):  034210.  DOI: 10.1088/1674-1056/ab6836
    Abstract ( 110 )   HTML   PDF (536KB) ( 95 )  
    We propose a scheme for realizing the optical nonreciprocal response based a four-mode optomechanical system, consisting of two charged mechanical modes and two linearly coupled optical modes. Two charged mechanical modes are coupled by Coulomb interaction, and two optical modes are coupled to one of mechanical modes by radiation pressure. We numerically evaluate the transmission probability of the probe field to obtain the optimum optical nonreciprocal response parameters. Also, we show that the optical nonreciprocal response is caused by the quantum interference between the optomechanical couplings and the linearly coupled interaction that breaks the time-reversal symmetry.
    High-contrast imaging based on wavefront shaping to improve low signal-to-noise ratio photoacoustic signals using superpixel method
    Xinjing Lv(吕新晶), Xinyu Xu(徐新羽), Qi Feng(冯祺), Bin Zhang(张彬), Yingchun Ding(丁迎春), Qiang Liu(柳强)
    Chin. Phys. B, 2020, 29 (3):  034301.  DOI: 10.1088/1674-1056/ab6842
    Abstract ( 112 )   HTML   PDF (1402KB) ( 83 )  
    Photoacoustic (PA) imaging has drawn tremendous research interest for various applications in biomedicine and experienced exponential growth over the past decade. Since the scattering effect of biological tissue on ultrasound is two- to three-orders magnitude weaker than that of light, photoacoustic imaging can effectively improve the imaging depth. However, as the depth of imaging further increases, the incident light is seriously affected by scattering that the generated photoacoustic signal is very weak and the signal-to-noise ratio (SNR) is quite low. Low SNR signals can reduce imaging quality and even cause imaging failure. In this paper, we proposed a new wavefront shaping and imaging method of low SNR photoacoustic signal using digital micromirror device (DMD) based superpixel method. We combined the superpixel method with DMD to modulate the phase and amplitude of the incident light, and the genetic algorithm (GA) was used as the wavefront shaping algorithm. The enhancement of the photoacoustic signal reached 10.46. Then we performed scanning imaging by moving the absorber with the translation stage. A clear image with contrast of 8.57 was obtained while imaging with original photoacoustic signals could not be achieved. The proposed method opens new perspectives for imaging with weak photoacoustic signals.
    Second harmonic magnetoacoustic responses of magnetic nanoparticles in magnetoacoustic tomography with magnetic induction
    Gepu Guo(郭各朴), Ya Gao(高雅), Yuzhi Li(李禹志), Qingyu Ma(马青玉), Juan Tu(屠娟), Dong Zhang(章东)
    Chin. Phys. B, 2020, 29 (3):  034302.  DOI: 10.1088/1674-1056/ab6843
    Abstract ( 91 )   HTML   PDF (858KB) ( 104 )  
    Due to the unique magnetic, mechanical and thermal properties, magnetic nanoparticles (MNPs) have comprehensive applications as the contrast and therapeutic agents in biomedical imaging and magnetic hyperthermia. The linear and nonlinear magnetoacoustic responses determined by the magnetic properties of MNPs have attracted more and more attention in biomedical engineering. By considering the relaxation time of MNPs, we derive the formulae of second harmonic magnetoacoustic responses (2H-MARs) for a cylindrical MNP solution model based on the mechanical oscillations of MNPs in magnetoacoustic tomography with magnetic induction (MAT-MI). It is proved that only the second harmonic magnetoacoustic oscillations can be generated by MNPs under an alternating magnetic excitation. The acoustic pressure of the 2H-MAR is proportional to the square of the magnetic field intensity and exhibits a linear increase with the concentration of MNPs. Numerical simulations of the 2H-MAR are confirmed by the experimental measurements for various magnetic field intensities and solution concentrations using a laser vibrometer. The favorable results demonstrate the feasibility of the harmonic measurements without the fundamental interference of the electromagnetic excitation, and suggest a new harmonic imaging strategy of MAT-MI for MNPs with enhanced spatial resolution and improved signal-to-noise ratio in biomedical applications.
    Bubble translation driven by pulsation in a double-bubble system
    Ling-Ling Zhang(张玲玲), Wei-Zhong Chen(陈伟中), Yuan-Yuan Zhang(张圆媛), Yao-Rong Wu(武耀蓉), Xun Wang(王寻), Guo-Ying Zhao(赵帼英)
    Chin. Phys. B, 2020, 29 (3):  034303.  DOI: 10.1088/1674-1056/ab69ee
    Abstract ( 103 )   HTML   PDF (652KB) ( 104 )  
    The pulsation and translation of two cavitation bubbles are studied numerically in sound field. The results show that bubbles' pulsation driven by the sound makes them translate. Different pulsations lead to different translations. Two bubbles will be mutually attractive to each other if they pulsate in phase, while they will be repulsive if out of phase. Furthermore, the secondary Bjerknes force for small phase difference is attractive, and it becomes repulsive for other phase differences up to π phase difference due to the nonlinear effect, although the attractive strength between two bubbles is much larger than the repulsive strength. Finally, one bubble pulsation and the other bubble stationary make the bubbles repel each other.
    Ultrasonic beam focusing characteristics of shear-vertical waves for contact-type linear phased array in solid
    Yu-Xiang Dai(戴宇翔), Shou-Guo Yan(阎守国), Bi-Xing Zhang(张碧星)
    Chin. Phys. B, 2020, 29 (3):  034304.  DOI: 10.1088/1674-1056/ab69ed
    Abstract ( 93 )   HTML   PDF (904KB) ( 76 )  
    We investigate the beam focusing technology of shear-vertical (SV) waves for a contact-type linear phased array to overcome the shortcomings of conventional wedge transducer arrays. The numerical simulation reveals the transient excitation and propagation characteristics of SV waves. It is found that the element size plays an important role in determining the transient radiation directivity of SV waves. The transient beam focusing characteristics of SV waves for various array parameters are deeply studied. It is particularly interesting to see that smaller element width will provide the focused beam of SV waves with higher quality, while larger element width may result in erratic fluctuation of focusing energy around the focal point. There exists a specific range of inter-element spacing for optimum focusing performance. Moreover, good beam focusing performance of SV waves can be achieved only at high steering angles.
    Influence of dynamic tissue properties on temperature elevation and lesions during HIFU scanning therapy: Numerical simulation
    Xiao Zou(邹孝), Hu Dong(董胡), Sheng-You Qian(钱盛友)
    Chin. Phys. B, 2020, 29 (3):  034305.  DOI: 10.1088/1674-1056/ab6c4f
    Abstract ( 96 )   HTML   PDF (1244KB) ( 94 )  
    When large tumors are treated, ablation of the entire volume of tumors requires multiple treatment spots formed by high intensity-focused ultrasound (HIFU) scanning therapy. The heating effect of HIFU on biological tissue is mainly reflected in temperature elevation and tissue lesions. Tissue property parameters vary with temperature and, in turn, the distribution of temperature as well as the heating effects change accordingly. In this study, an HIFU scanning therapy model considering dynamic tissue properties is provided. The acoustic fields and temperature fields are solved combining the Helmholtz wave equation with Pennes bio-heat transfer equation based on the finite element method (FEM) to investigate the effects of various tissue properties (i.e., the attenuation coefficient, acoustic velocity, thermal conductivity, specific heat capacity, density, and blood perfusion rate) on heating performance. Comparisons of the temperature distribution and thermal lesions under static and dynamic properties are made based on the data of tissue property parameters varying with temperature. The results show that the dynamic changes of thermal conductivity, specific heat capacity, and acoustic velocity may account for the decrease of temperature elevation in HIFU treatment, while the dynamic changes of attenuation coefficient, density, and blood perfusion rate aggravate the increase of temperature on treatment spots. Compared with other properties, the dynamic change of attenuation coefficient has a greater impact on tissue temperature elevation. During HIFU scanning therapy, the temperature elevation and tissue lesions of the first treatment spot are smaller than those of the subsequent treatment spots, but the temperature on the last treatment spot drops faster during the cooling period. The ellipsoidal tissue lesion is not symmetrical; specifically, the part facing toward the previous treatment spot tends to be larger. Under the condition of the same doses, the temperature elevation and the size of tissue lesions under dynamic properties present significant growth in comparison to static properties. Besides, the tissue lesion begins to form earlier with a more unsymmetrical shape and is connected to the tissue lesion around the previous treatment spot. As a result, lesions around all the treatment spots are connected with each other to form a closed lesion region. The findings in this study reveal the influence of dynamic tissue properties on temperature elevation and lesions during HIFU scanning therapy, providing useful support for the optimization of treatment programs to guarantee higher efficacy and safety.
    Simulation-based optimization of inner layout of a theater considering the effect of pedestrians
    Qing-Fei Gao(高庆飞), Yi-Zhou Tao(陶亦舟), Yan-Fang Wei(韦艳芳), Cheng Wu(吴成), Li-Yun Dong(董力耘)
    Chin. Phys. B, 2020, 29 (3):  034501.  DOI: 10.1088/1674-1056/ab6c44
    Abstract ( 99 )   HTML   PDF (6011KB) ( 84 )  
    We propose an extended cellular automaton model based on the floor field. The floor field can be changed accordingly in the presence of pedestrians. Furthermore, the effects of pedestrians with different speeds are distinguished, i.e., still pedestrians result in more increment of the floor field than moving ones. The improved floor field reflects impact of pedestrians as movable obstacles on evacuation process. The presented model was calibrated by comparing with previous studies. It is shown that this model provides a better description of crowd evacuation both qualitatively and quantitatively. Then we investigated crowd evacuation from a middle-size theater. Four possible designs of aisles in the theater are studied and one of them is the actual design in reality. Numerical simulation shows that the actual design of the theater is reasonable. Then we optimize the position of the side exit in order to reduce the evacuation time. It is shown that the utilization of the two exits at bottom is less than that of the side exits. When the position of the side exit is shifted upwards by about 1.6 m, it is found that the evacuation time reaches its minimum.
    A mass-conserved multiphase lattice Boltzmann method based on high-order difference
    Zhang-Rong Qin(覃章荣), Yan-Yan Chen(陈燕雁), Feng-Ru Ling(凌风如), Ling-Juan Meng(孟令娟), Chao-Ying Zhang(张超英)
    Chin. Phys. B, 2020, 29 (3):  034701.  DOI: 10.1088/1674-1056/ab6834
    Abstract ( 102 )   HTML   PDF (2294KB) ( 77 )  
    The Z-S-C multiphase lattice Boltzmann model [Zheng, Shu, and Chew (ZSC), J. Comput. Phys. 218, 353 (2006)] is favored due to its good stability, high efficiency, and large density ratio. However, in terms of mass conservation, this model is not satisfactory during the simulation computations. In this paper, a mass correction is introduced into the ZSC model to make up the mass leakage, while a high-order difference is used to calculate the gradient of the order parameter to improve the accuracy. To verify the improved model, several three-dimensional multiphase flow simulations are carried out, including a bubble in a stationary flow, the merging of two bubbles, and the bubble rising under buoyancy. The numerical simulations show that the results from the present model are in good agreement with those from previous experiments and simulations. The present model not only retains the good properties of the original ZSC model, but also achieves the mass conservation and higher accuracy.
    Multi-bubble motion behavior of uniform magnetic field based on phase field model
    Chang-Sheng Zhu(朱昶胜), Zhen Hu(胡震), Kai-Ming Wang(王凯明)
    Chin. Phys. B, 2020, 29 (3):  034702.  DOI: 10.1088/1674-1056/ab6839
    Abstract ( 110 )   HTML   PDF (2279KB) ( 83 )  
    Aiming at the interaction and coalescence of bubbles in gas-liquid two-phase flow, a multi-field coupling model was established to simulate deformation and dynamics of multi-bubble in gas-liquid two-phase flow by coupling magnetic field, phase field, continuity equation, and momentum equation. Using the phase field method to capture the interface of two phases, the geometric deformation and dynamics of a pair of coaxial vertical rising bubbles under the applied uniform magnetic field in the vertical direction were investigated. The correctness of results is verified by mass conservation method and the comparison of the existing results. The results show that the applied uniform magnetic field can effectively shorten the distance between the leading bubble and the trailing bubble, the time of bubbles coalescence, and increase the velocity of bubbles coalescence. Within a certain range, as the intensity of the applied uniform magnetic field increases, the velocity of bubbles coalescence is proportional to the intensity of the magnetic field, and the time of bubbles coalescence is inversely proportional to the intensity of the magnetic field.
    Electrohydrodynamic behaviors of droplet under a uniform direct current electric field
    Zi-Long Deng(邓梓龙), Mei-Mei Sun(孙美美), Cheng Yu(于程)
    Chin. Phys. B, 2020, 29 (3):  034703.  DOI: 10.1088/1674-1056/ab6835
    Abstract ( 106 )   HTML   PDF (966KB) ( 81 )  
    The electrohydrodynamic behaviors and evolution processes of silicone oil droplet in castor oil under uniform direct current (DC) electric field are visually observed based on a high-speed microscopic platform. Subsequently, the effects of different working conditions, such as electric field strength, droplet size, etc., on droplet behaviors are roundly discussed. It can be found that there are four droplet behavior modes, including Taylor deformation, typical oblique rotation, periodic oscillation, and fracture, which change with the increase of electric field strength. It is also demonstrated that the degree of flat ellipse deformation gets larger under a stronger electric field. Moreover, both of the stronger electric field and smaller droplet size lead to an increase in the rotation angle of the droplet.
    Interface coupling effects of weakly nonlinear Rayleigh-Taylor instability with double interfaces
    Zhiyuan Li(李志远), Lifeng Wang(王立锋), Junfeng Wu(吴俊峰), Wenhua Ye(叶文华)
    Chin. Phys. B, 2020, 29 (3):  034704.  DOI: 10.1088/1674-1056/ab6965
    Abstract ( 129 )   HTML   PDF (793KB) ( 96 )  
    Taking the Rayleigh-Taylor instability with double interfaces as the research object, the interface coupling effects in the weakly nonlinear regime are studied numerically. The variation of Atwood numbers on the two interfaces and the variation of the thickness between them are taken into consideration. It is shown that, when the Atwood number on the lower interface is small, the amplitude of perturbation growth on the lower interface is positively related with the Atwood number on the upper interface. However, it is negatively related when the Atwood number on the lower interface is large. The above phenomenon is quantitatively studied using an analytical formula and the underlying physical mechanism is presented.
    Fractional variant of Stokes-Einstein relation in aqueous ionic solutions under external static electric fields
    Gan Ren(任淦), Shikai Tian(田时开)
    Chin. Phys. B, 2020, 29 (3):  036101.  DOI: 10.1088/1674-1056/ab695b
    Abstract ( 92 )   HTML   PDF (651KB) ( 98 )  
    Both ionic solutions under an external applied static electric field E and glassy-forming liquids under undercooled state are in non-equilibrium state. In this work, molecular dynamics (MD) simulations with three aqueous alkali ion chloride (NaCl, KCl, and RbCl) ionic solutions are performed to exploit whether the glass-forming liquid analogous fractional variant of the Stokes-Einstein relation also exists in ionic solutions under E. Our results indicate that the diffusion constant decouples from the structural relaxation time under E, and a fractional variant of the Stokes-Einstein relation is observed as well as a crossover analogous to the glass-forming liquids under cooling. The fractional variant of the Stokes-Einstein relation is attributed to the E introduced deviations from Gaussian and the nonlinear effect.
    Synthesis, structure, and properties of Ba9Co3Se15 with one-dimensional spin chains Hot!
    Lei Duan(段磊), Xian-Cheng Wang(望贤成), Jun Zhang(张俊), Jian-Fa Zhao(赵建发), Li-Peng Cao(曹立朋), Wen-Min Li(李文敏), Run-Ze Yu(于润泽), Zheng Deng(邓正), Chang-Qing Jin(靳常青)
    Chin. Phys. B, 2020, 29 (3):  036102.  DOI: 10.1088/1674-1056/ab69ea
    Abstract ( 151 )   HTML   PDF (1055KB) ( 112 )  
    A new compound with one-dimensional spin chains, Ba9Co3Se15, was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. Ba9Co3Se15 crystallizes in a hexagonal structure with the space group P-6c2 (No. 188) and lattice constants of a =b = 9.6765 Å and c = 18.9562 Å. The structure consists of trimeric face-sharing octahedral CoSe6 chains, which are arranged in a triangular lattice in the ab-plane and separated by Ba atoms. The distance of the nearest neighbor of CoSe6 chains is very large, given by the lattice constant a= 9.6765 Å. The Weiss temperature Tθ associated with the intra-chain coupling strength is about -346 K. However, no long-range magnetic order but a spin glass transition at ~3 K has been observed. Our results indicate that the spin glass behavior in Ba9Co3Se15 mainly arises from the magnetic frustration due to the geometrically frustrated triangular lattice.
    First-principles investigation on ideal strength of B2 NiAl and NiTi alloys
    Chun-Yao Zhang(张春尧), Fu-Yang Tian(田付阳), Xiao-Dong Ni(倪晓东)
    Chin. Phys. B, 2020, 29 (3):  036201.  DOI: 10.1088/1674-1056/ab7440
    Abstract ( 133 )   HTML   PDF (2090KB) ( 106 )  

    For B2 NiAl and NiTi intermetallic compounds, the ideal stress-strain image is lack from the perspective of elastic constants. We use first-principles calculation to investigate the ideal strength and elastic behavior under the tensile and shear loads. The relation between the ideal strength and elastic constants is found. The uniaxial tension of NiAl and NiTi along <001> crystal direction leads to the change from tetragonal path to orthogonal path, which is driven by the vanishing of the shear constant C66. The shear failure under {110}<111> shear deformation occurring in process of tension may result in a small ideal tensile strength (~2 GPa) for NiTi. The unlikeness in the ideal strength of NiAl and NiTi alloys is discussed based on the charge density difference.

    Effect of overdrive voltage on PBTI trapping behavior in GaN MIS-HEMT with LPCVD SiNx gate dielectric
    Tao-Tao Que(阙陶陶), Ya-Wen Zhao(赵亚文), Liu-An Li(李柳暗), Liang He(何亮), Qiu-Ling Qiu(丘秋凌), Zhen-Xing Liu(刘振兴), Jin-Wei Zhang(张津玮), Jia Chen(陈佳), Zhi-Sheng Wu(吴志盛), Yang Liu(刘扬)
    Chin. Phys. B, 2020, 29 (3):  037201.  DOI: 10.1088/1674-1056/ab696b
    Abstract ( 118 )   HTML   PDF (1180KB) ( 95 )  
    The effect of high overdrive voltage on the positive bias temperature instability (PBTI) trapping behavior is investigated for GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) with LPCVD-SiNx gate dielectric. A higher overdrive voltage is more effective to accelerate the electrons trapping process, resulting in a unique trapping behavior, i.e., a larger threshold voltage shift with a weaker time dependence and a weaker temperature dependence. Combining the degradation of electrical parameters with the frequency-conductance measurements, the unique trapping behavior is ascribed to the defect energy profile inside the gate dielectric changing with stress time, new interface/border traps with a broad distribution above the channel Fermi level are introduced by high overdrive voltage.
    High-mobility SiC MOSFET with low density of interface traps using high pressure microwave plasma oxidation
    Xin-Yu Liu(刘新宇), Ji-Long Hao(郝继龙), Nan-Nan You(尤楠楠), Yun Bai(白云), Yi-Dan Tang(汤益丹), Cheng-Yue Yang(杨成樾), Sheng-Kai Wang(王盛凯)
    Chin. Phys. B, 2020, 29 (3):  037301.  DOI: 10.1088/1674-1056/ab68c0
    Abstract ( 115 )   HTML   PDF (1104KB) ( 118 )  
    The microwave plasma oxidation under the relatively high pressure (6 kPa) region is introduced into the fabrication process of SiO2/4H-SiC stack. By controlling the oxidation pressure, species, and temperature, the record low density of interface traps (~ 4×1010 cm-2·eV-1@Ec - 0.2 eV) is demonstrated on SiO2/SiC stack formed by microwave plasma oxidation. And high quality SiO2 with very flat interface (0.27-nm root-mean-square roughness) is obtained. High performance SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with peak field effect mobility of 44 cm-2·eV-1 is realized without additional treatment. These results show the potential of a high-pressure plasma oxidation step for improving the channel mobility in SiC MOSFETs.
    Defect engineering on the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons
    Huakai Xu(许华慨), Gang Ouyang(欧阳钢)
    Chin. Phys. B, 2020, 29 (3):  037302.  DOI: 10.1088/1674-1056/ab69ec
    Abstract ( 102 )   HTML   PDF (3168KB) ( 110 )  
    We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons (APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs. Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.
    Influence of Zr50Cu50 thin film metallic glass as buffer layer on the structural and optoelectrical properties of AZO films
    Bao-Qing Zhang(张宝庆), Gao-Peng Liu(刘高鹏), Hai-Tao Zong(宗海涛), Li-Ge Fu(付丽歌), Zhi-Fei Wei(魏志飞), Xiao-Wei Yang(杨晓炜), Guo-Hua Cao(曹国华)
    Chin. Phys. B, 2020, 29 (3):  037303.  DOI: 10.1088/1674-1056/ab6c50
    Abstract ( 105 )   HTML   PDF (5750KB) ( 93 )  
    Aluminum-doped ZnO (AZO) thin films with thin film metallic glass of Zr50Cu50 as buffer are prepared on glass substrates by the pulsed laser deposition. The influence of buffer thickness and substrate temperature on structural, optical, and electrical properties of AZO thin film are investigated. Increasing the thickness of buffer layer and substrate temperature can both promote the transformation of AZO from amorphous to crystalline structure, while they show (100) and (002) unique preferential orientations, respectively. After inserting Zr50Cu50 layer between the glass substrate and AZO film, the sheet resistance and visible transmittance decrease, but the infrared transmittance increases. With substrate temperature increasing from 25 ℃ to 520 ℃, the sheet resistance of AZO(100 nm)/ Zr50Cu50(4 nm) film first increases and then decreases, and the infrared transmittance is improved. The AZO(100 nm)/Zr50Cu50(4 nm) film deposited at a substrate temperature of 360 ℃ exhibits a low sheet resistance of 26.7 Ω/□, high transmittance of 82.1% in the visible light region, 81.6% in near-infrared region, and low surface roughness of 0.85 nm, which are useful properties for their potential applications in tandem solar cell and infrared technology.
    Comparative study on transport properties of N-, P-, and As-doped SiC nanowires: Calculated based on first principles
    Ya-Lin Li(李亚林), Pei Gong(龚裴), Xiao-Yong Fang(房晓勇)
    Chin. Phys. B, 2020, 29 (3):  037304.  DOI: 10.1088/1674-1056/ab6c4c
    Abstract ( 102 )   HTML   PDF (1418KB) ( 87 )  
    According to the one-dimensional quantum state distribution, carrier scattering, and fixed range hopping model, the structural stability and electron transport properties of N-, P-, and As-doped SiC nanowires (N-SiCNWs, P-SiCNWs, and As-SiCNWs) are simulated by using the first principles calculations. The results show that the lattice structure of N-SiCNWs is the most stable in the lattice structures of the above three kinds of doped SiCNWs. At room temperature, for unpassivated SiCNWs, the doping effect of P and As are better than that of N. After passivation, the conductivities of all doped SiCNWs increase by approximately two orders of magnitude. The N-SiCNW has the lowest conductivity. In addition, the N-, P-, As-doped SiCNWs before and after passivation have the same conductivity-temperature characteristics, that is, above room temperature, the conductivity values of the doped SiCNWs all increase with temperature increasing. These results contribute to the electronic application of nanodevices.
    General principles to high-throughput constructing two-dimensional carbon allotropes Hot!
    Qing Xie(谢庆), Lei Wang(王磊), Jiangxu Li(李江旭), Ronghan Li(李荣汉), Xing-Qiu Chen(陈星秋)
    Chin. Phys. B, 2020, 29 (3):  037306.  DOI: 10.1088/1674-1056/ab6c4b
    Abstract ( 173 )   HTML   PDF (6056KB) ( 171 )  
    We propose general principles to construct two-dimensional (2D) single-atom-thick carbon allotropes. They can be viewed as the generalization of patterning Stone-Walse defects (SWDs) by manipulating bond rotation and of patterning inverse SWDs by adding (or removing) carbon pairs on the pristine graphene, respectively. With these principles, numerous 2D allotropes of carbon can be systematically constructed. Using 20 constructed 2D allotropes as prototypical and benchmark examples, besides nicely reproducing all well-known ones, such as pentaheptites, T-graphene, OPGs, etc, we still discover 13 new allotropes. Their structural, thermodynamic, dynamical, and electronic properties are calculated by means of first-principles calculations. All these allotropes are metastable in energy compared with that of graphene and, except for OPG-A and C3-10-H allotropes, the other phonon spectra of 18 selected allotropes are dynamically stable. In particular, the proposed C3-11 allotrope is energetically favorable than graphene when the temperature is increased up to 1043 K according to the derived free energies. The electronic band structures demonstrate that (i) the C3-8 allotrope is a semiconductor with an indirect DFT band gap of 1.04 eV, (ii) another unusual allotrope is C3-12 which exhibits a highly flat band just crossing the Fermi level, (iii) four allotropes are Dirac semimetals with the appearance of Dirac cones at the Fermi level in the lattices without hexagonal symmetry, and (vi) without the spin-orbit coupling (SOC) effect, the hexagonal C3-11 allotrope exhibits two Dirac cones at K and K' points in its Brillouin zone in similarity with graphene.
    Time-dependent Ginzburg-Landau equations for multi-gap superconductors
    Minsi Li(李敏斯), Jiahong Gu(古家虹), Long Du(杜龙), Hongwei Zhong(钟红伟), Lijuan Zhou(周丽娟), Qinghua Chen(陈庆华)
    Chin. Phys. B, 2020, 29 (3):  037401.  DOI: 10.1088/1674-1056/ab69ef
    Abstract ( 109 )   HTML   PDF (482KB) ( 108 )  
    We numerically solve the time-dependent Ginzburg-Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors.
    Three- and two-dimensional calculations for the interface anisotropy dependence of magnetic properties of exchange-spring Nd2Fe14B/α-Fe multilayers with out-of-plane easy axes
    Qian Zhao(赵倩), Xin-Xin He(何鑫鑫), Francois-Jacques Morvan(李文瀚), Guo-Ping Zhao(赵国平), Zhu-Bai Li(李柱柏)
    Chin. Phys. B, 2020, 29 (3):  037501.  DOI: 10.1088/1674-1056/ab69e9
    Abstract ( 97 )   HTML   PDF (1128KB) ( 97 )  
    Hysteresis loops, energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe14B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional (3D) and one-dimensional (1D) micromagnetic methods, focused on the influence of the interface anisotropy. The calculated results are carefully compared with each other. The interface anisotropy effect is very palpable on the nucleation, pinning and coercive fields when the soft layer is very thin. However, as the soft layer thickness increases, the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises. Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field. The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal, i.e., nucleation, evolution and irreversible motion of the domain wall. The above results calculated by two models are in good agreement with each other. Moreover, the in-plane magnetic moment orientations based on two models are different. The 3D calculation shows a progress of generation and disappearance of vortex state, however, the magnetization orientations within the film plane calculated by the 1D model are coherent. Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally.
    Giant low-field magnetocaloric effect in EuTi1-xNbxO3 (x=0.05, 0.1, 0.15, and 0.2) compounds
    Wen-Hao Jiang(姜文昊), Zhao-Jun Mo(莫兆军), Jia-Wei Luo(罗佳薇), Zhe-Xuan Zheng(郑哲轩), Qiu-Jie Lu(卢秋杰), Guo-Dong Liu(刘国栋), Jun Shen(沈俊), Lan Li(李岚)
    Chin. Phys. B, 2020, 29 (3):  037502.  DOI: 10.1088/1674-1056/ab69e7
    Abstract ( 109 )   HTML   PDF (1439KB) ( 87 )  
    The magnetic properties and magnetocaloric effect (MCE) of EuTi1-xNbxO3 (x=0.05, 0.1, 0.15, and 0.2) compounds are investigated. Owing to electronic doping, parts of Ti ions are replaced by Nb ions, the lattice constant increases and a small number of Ti4+ (3d0) ions change into Ti3+ (3d1). It is the ferromagnetism state that is dominant in the derivative balance. The values of the maximum magnetic entropy change (-ΔSMmax) are 10.3 J/kg·K, 9.6 J/kg·K, 13.1 J/kg·K, and 11.9 J/kg·K for EuTi1-xNbxO3 (x=0.05, 0.1, 0.15, and 0.2) compounds and the values of refrigeration capacity are 36, 33, 86, and 80 J/kg as magnetic field changes in a range of 0 T-1 T. The EuTi1-xNbxO3 (x=0.05, 0.1, 0.15, and 0.2) compounds with giant reversible MCE are considered as a good candidate for magnetic refrigerant working at low-temperature and low-field.
    Magnetoelectric effects in multiferroic Y-type hexaferrites Ba0.3Sr1.7CoxMg2-xFe12O22
    Yanfen Chang(畅艳芬), Kun Zhai(翟昆), Young Sun(孙阳)
    Chin. Phys. B, 2020, 29 (3):  037701.  DOI: 10.1088/1674-1056/ab696c
    Abstract ( 121 )   HTML   PDF (723KB) ( 119 )  
    Y-type hexaferrites with tunable conical magnetic structures are promising single-phase multiferroics that exhibit large magnetoelectric effects. We have investigated the influence of Co substitution on the magnetoelectric properties in the Y-type hexaferrites Ba0.3Sr1.7CoxMg2-xFe12O22 (x = 0.0, 0.4, 1.0, 1.6). The spin-induced electric polarization can be reversed by applying a low magnetic field for all the samples. The magnetoelectric phase diagrams of Ba0.3Sr1.7CoxMg2-xFe12O22 are obtained based on the measurements of magnetic field dependence of dielectric constant at selected temperatures. It is found that the substitution of Co ions can preserve the ferroelectric phase up to a higher temperature, and thus is beneficial for achieving single-phase multiferroics at room temperature.
    Surface passivation in n-type silicon and its application insilicon drift detector
    Yiqing Wu(吴怡清), Ke Tao(陶科), Shuai Jiang(姜帅), Rui Jia(贾锐), Ye Huang(黄也)
    Chin. Phys. B, 2020, 29 (3):  037702.  DOI: 10.1088/1674-1056/ab695e
    Abstract ( 87 )   HTML   PDF (1954KB) ( 94 )  
    Based on the surface passivation of n-type silicon in a silicon drift detector (SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon (NAOS) method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition (PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate. The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×1015 cm-3. When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.
    Processes underlying the laser photochromic effect in colloidal plasmonic nanoparticle aggregates
    A E Ershov, V S Gerasimov, I L Isaev, A P Gavrilyuk, S V Karpov
    Chin. Phys. B, 2020, 29 (3):  037802.  DOI: 10.1088/1674-1056/ab6551
    Abstract ( 106 )   HTML   PDF (998KB) ( 81 )  
    We have studied the dynamic and static processes occurring in disordered multiparticle colloidal Ag aggregates with natural structure and affecting their plasmonic absorption spectra under pico- and nanosecond pulsed laser radiations, as well as the physical origin responsible for these processes. We have shown that depending on the duration of the laser pulse, the mechanisms of laser modification of such aggregates can be associated both with changes in the resonant properties of the particles due to their heating and melting (picosecond irradiation mode) and with the particle shifts in the resonant domains of the aggregates (nanosecond pulses) which depend on the wavelength, intensity, and polarization of the radiation. These mechanisms result in formation of a narrow dip in the plasmonic absorption spectrum of the aggregates near the laser radiation wavelength and affect the shape and position of the dip. The effect of polydispersity of nanoparticle aggregates on laser photochromic reaction has been studied.
    A low-dimensional crystal growth model on an isotropic and quasi-free sustained substrate
    Chenxi Lu(卢晨曦), Senjiang Yu(余森江), Lingwei Li(李领伟), Bo Yang(杨波), Xiangming Tao(陶向明), Gaoxiang Ye(叶高翔)
    Chin. Phys. B, 2020, 29 (3):  038101.  DOI: 10.1088/1674-1056/ab6968
    Abstract ( 102 )   HTML   PDF (758KB) ( 84 )  
    A new crystal growth theoretical model is established for the low-dimensional nanocrystals on an isotropic and quasi-free sustained substrate. The driven mechanism of the model is based on the competitive growth among the preferential growth directions of the crystals possessing anisotropic crystal structures, such as the hexagonal close-packed and wurtzite structures. The calculation results are in good agreement with the experimental findings in the growth process of the low-dimensional Zn nanocrystals on silicone oil surfaces. Our model shows a growth mechanism of various low-dimensional crystals on/in the isotropic substrates.
    Low-temperature plasma enhanced atomic layer deposition of large area HfS2 nanocrystal thin films
    Ailing Chang(常爱玲), Yichen Mao(毛亦琛), Zhiwei Huang(黄志伟), Haiyang Hong(洪海洋), Jianfang Xu(徐剑芳), Wei Huang(黄巍), Songyan Chen(陈松岩), Cheng Li(李成)
    Chin. Phys. B, 2020, 29 (3):  038102.  DOI: 10.1088/1674-1056/ab6c4a
    Abstract ( 89 )   HTML   PDF (996KB) ( 78 )  
    Hafnium disulfide (HfS2) is a promising two-dimensional material for scaling electronic devices due to its higher carrier mobility, in which the combination of two-dimensional materials with traditional semiconductors in the framework of CMOS-compatible technology is necessary. We reported on the deposition of HfS2 nanocrystals by remote plasma enhanced atomic layer deposition at low temperature using Hf(N(CH3)(C2H5))4 and H2S as the reaction precursors. Self-limiting reaction behavior was observed at the deposition temperatures ranging from 150℃ to 350℃, and the film thickness increased linearly with the growth cycles. The uniform HfS2 nanocrystal thin films were obtained with the size of nanocrystal grain up to 27 nm. It was demonstrated that higher deposition temperature could enlarge the grain size and improve the HfS2 crystallinity, while causing crystallization of the mixed HfO2 above 450℃. These results suggested that atomic layer deposition is a low-temperature route to synthesize high quality HfS2 nanocrystals for electronic device or electrochemical applications.
    Comparison study of GaN films grown on porous andplanar GaN templates
    Shan Ding(丁姗), Yue-Wen Li(李悦文), Xiang-Qian Xiu(修向前), Xue-Mei Hua(华雪梅), Zi-Li Xie(谢自力), Tao Tao(陶涛), Peng Chen(陈鹏), Bin Liu(刘斌), Rong Zhang(张荣), You-Dou Zheng(郑有炓)
    Chin. Phys. B, 2020, 29 (3):  038103.  DOI: 10.1088/1674-1056/ab6c48
    Abstract ( 117 )   HTML   PDF (650KB) ( 87 )  
    The GaN thick films have been grown on porous GaN template and planar metal-organic chemical vapor deposition (MOCVD)-GaN template by halide vapor phase epitaxy (HVPE). The analysis results indicated that the GaN films grown on porous and planar GaN templates under the same growth conditions have similar structural, optical, and electrical properties. But the porous GaN templates could significantly reduce the stress in the HVPE-GaN epilayer and enhance the photoluminescence (PL) intensity. The voids in the porous template were critical for the strain relaxation in the GaN films and the increase of the PL intensity. Thus, the porous GaN converted from β-Ga2O3 film as a novel promising template is suitable for the growth of stress-free GaN films.
    Coulomb blockade and hopping transport behaviors of donor-induced quantum dots in junctionless transistors
    Liu-Hong Ma(马刘红), Wei-Hua Han(韩伟华), Fu-Hua Yang(杨富华)
    Chin. Phys. B, 2020, 29 (3):  038104.  DOI: 10.1088/1674-1056/ab74ce
    Abstract ( 121 )   HTML   PDF (2676KB) ( 112 )  
    The ionized dopants, working as quantum dots in silicon nanowires, exhibit potential advantages for the development of atomic-scale transistors. We investigate single electron tunneling through a phosphorus dopant induced quantum dots array in heavily n-doped junctionless nanowire transistors. Several subpeaks splittings in current oscillations are clearly observed due to the coupling of the quantum dots at the temperature of 6 K. The transport behaviors change from resonance tunneling to hoping conduction with increased temperature. The charging energy of the phosphorus donors is approximately 12.8 meV. This work helps clear the basic mechanism of electron transport through donor-induced quantum dots and electron transport properties in the heavily doped nanowire through dopant engineering.
    Theoretical study on the relationship between the position of the substituent and the ESIPT fluorescence characteristic of HPIP
    Xin Zhang(张馨), Jian-Hui Han(韩建慧), You Li(李尤), Chao-Fan Sun(孙朝范), Xing Su(苏醒), Ying Shi(石英), Hang Yin(尹航)
    Chin. Phys. B, 2020, 29 (3):  038201.  DOI: 10.1088/1674-1056/ab6d50
    Abstract ( 135 )   HTML   PDF (3217KB) ( 90 )  
    The influences of the substituent base position on the excited state intramolecular proton transfer fluorescence properties were explored in 2-(2'-hydroxyphenyl)imidazo[1,2-a]-pyridine (HPIP) and HPIP's derivatives (5'Br-HPIP and 6'Br-HPIP). And the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods were used to calculate the molecule structures. The calculated results showed that the influence of 5'Br-HPIP on the fluorescence intensity is stronger than that of 6'Br-HPIP. The fluorescence emission peak of 5'Br-HPIP occurred a blue shift compared with HPIP, and 6'Br-HPIP exhibited an opposite red shift. The change of the fluorescence emission peak was attributed to the decrease of the energy gap from 6'Br-HPIP to 5'Br-HPIP. Our work on the substituent position influence could be helpful to design and develop new materials.
    Investigation of gate oxide traps effect on NAND flash memory by TCAD simulation
    He-Kun Zhang(章合坤), Xuan Tian(田璇), Jun-Peng He(何俊鹏), Zhe Song(宋哲), Qian-Qian Yu(蔚倩倩), Liang Li(李靓), Ming Li(李明), Lian-Cheng Zhao(赵连城), Li-Ming Gao(高立明)
    Chin. Phys. B, 2020, 29 (3):  038501.  DOI: 10.1088/1674-1056/ab695f
    Abstract ( 146 )   HTML   PDF (964KB) ( 107 )  
    The effects of gate oxide traps on gate leakage current and device performance of metal-oxide-nitride-oxide-silicon (MONOS)-structured NAND flash memory are investigated through Sentaurus TCAD. The trap-assisted tunneling (TAT) model is implemented to simulate the leakage current of MONOS-structured memory cell. In this study, trap position, trap density, and trap energy are systematically analyzed for ascertaining their influences on gate leakage current, program/erase speed, and data retention properties. The results show that the traps in blocking layer significantly enhance the gate leakage current and also facilitates the cell program/erase. Trap density ~1018 cm-3 and trap energy ~1 eV in blocking layer can considerably improve cell program/erase speed without deteriorating data retention. The result conduces to understanding the role of gate oxide traps in cell degradation of MONOS-structured NAND flash memory.
    Enhancement of radiation hardness of InP-based HEMT with double Si-doped plane
    Ying-Hui Zhong(钟英辉), Bo Yang(杨博), Ming-Ming Chang(常明铭), Peng Ding(丁芃), Liu-Hong Ma(马刘红), Meng-Ke Li(李梦珂), Zhi-Yong Duan(段智勇), Jie Yang(杨洁), Zhi Jin(金智), Zhi-Chao Wei(魏志超)
    Chin. Phys. B, 2020, 29 (3):  038502.  DOI: 10.1088/1674-1056/ab6962
    Abstract ( 93 )   HTML   PDF (714KB) ( 77 )  
    An anti-radiation structure of InP-based high electron mobility transistor (HEMT) has been proposed and optimized with double Si-doped planes. The additional Si-doped plane under channel layer has made a huge promotion in channel current, transconductance, current gain cut-off frequency, and maximum oscillation frequency of InP-based HEMTs. Moreover, direct current (DC) and radio frequency (RF) characteristic properties and their reduction rates have been compared in detail between single Si-doped and double Si-doped structures after 75-keV proton irradiation with dose of 5×1011 cm-2, 1×1012 cm-2, and 5×1012 cm-2. DC and RF characteristics for both structures are observed to decrease gradually as irradiation dose rises, which particularly show a drastic drop at dose of 5×1012 cm-2. Besides, characteristic degradation degree of the double Si-doped structure is significantly lower than that of the single Si-doped structure, especially at large proton irradiation dose. The enhancement of proton radiation tolerance by the insertion of another Si-doped plane could be accounted for the tremendously increased native carriers, which are bound to weaken substantially the carrier removal effect by irradiation-induced defects.
    Numerical and analytical investigations for the SOI LDMOS with alternated high-k dielectric and step doped silicon pillars
    Jia-Fei Yao(姚佳飞), Yu-Feng Guo(郭宇锋), Zhen-Yu Zhang(张振宇), Ke-Meng Yang(杨可萌), Mao-Lin Zhang(张茂林), Tian Xia(夏天)
    Chin. Phys. B, 2020, 29 (3):  038503.  DOI: 10.1088/1674-1056/ab6960
    Abstract ( 113 )   HTML   PDF (637KB) ( 93 )  
    This paper presents a new silicon-on-insulator (SOI) lateral-double-diffused metal-oxide-semiconductor transistor (LDMOST) device with alternated high-k dielectric and step doped silicon pillars (HKSD device). Due to the modulation of step doping technology and high-k dielectric on the electric field and doped profile of each zone, the HKSD device shows a greater performance. The analytical models of the potential, electric field, optimal breakdown voltage, and optimal doped profile are derived. The analytical results and the simulated results are basically consistent, which confirms the proposed model suitable for the HKSD device. The potential and electric field modulation mechanism are investigated based on the simulation and analytical models. Furthermore, the influence of the parameters on the breakdown voltage (BV) and specific on-resistance (Ron,sp) are obtained. The results indicate that the HKSD device has a higher BV and lower Ron,sp compared to the SD device and HK device.
    A method to extend wavelength into middle-wavelength infrared based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector
    Xuan-Zhang Li(李炫璋), Ling Sun(孙令), Jin-Lei Lu(鲁金蕾), Jie Liu(刘洁), Chen Yue(岳琛), Li-Li Xie(谢莉莉), Wen-Xin Wang(王文新), Hong Chen(陈弘), Hai-Qiang Jia(贾海强), Lu Wang(王禄)
    Chin. Phys. B, 2020, 29 (3):  038504.  DOI: 10.1088/1674-1056/ab6969
    Abstract ( 135 )   HTML   PDF (494KB) ( 104 )  
    We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified InAsSb quantum well, GaSb is replaced with AlSb/AlGaSb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.
    Role of remote Coulomb scattering on the hole mobility at cryogenic temperatures in SOI p-MOSFETs
    Xian-Le Zhang(张先乐), Peng-Ying Chang(常鹏鹰), Gang Du(杜刚), Xiao-Yan Liu(刘晓彦)
    Chin. Phys. B, 2020, 29 (3):  038505.  DOI: 10.1088/1674-1056/ab6966
    Abstract ( 94 )   HTML   PDF (667KB) ( 97 )  
    The impacts of remote Coulomb scattering (RCS) on hole mobility in ultra-thin body silicon-on-insulator (UTB SOI) p-MOSFETs at cryogenic temperatures are investigated. The physical models including phonon scattering, surface roughness scattering, and remote Coulomb scatterings are considered, and the results are verified by the experimental results at different temperatures for both bulk (from 300 K to 30 K) and UTB SOI (300 K and 25 K) p-MOSFETs. The impacts of the interfacial trap charges at both front and bottom interfaces on the hole mobility are mainly evaluated for the UTB SOI p-MOSFETs at liquid helium temperature (4.2 K). The results reveal that as the temperature decreases, the RCS due to the interfacial trap charges plays an important role in the hole mobility.
    Microstructure evolution and passivation quality of hydrogenated amorphous silicon oxide (a-SiOx:H) on <100>- and <111>-orientated c-Si wafers
    Jun-Fan Chen(陈俊帆), Sheng-Sheng Zhao(赵生盛), Ling-Ling Yan(延玲玲), Hui-Zhi Ren(任慧志), Can Han(韩灿), De-Kun Zhang(张德坤), Chang-Chun Wei(魏长春), Guang-Cai Wang(王广才), Guo-Fu Hou(侯国付), Ying Zhao(赵颖), Xiao-Dan Zhang(张晓丹)
    Chin. Phys. B, 2020, 29 (3):  038801.  DOI: 10.1088/1674-1056/ab6c47
    Abstract ( 105 )   HTML   PDF (1302KB) ( 91 )  
    Hydrogenated amorphous silicon oxide (a-SiOx:H) is an attractive passivation material to suppress epitaxial growth and reduce the parasitic absorption loss in silicon heterojunction (SHJ) solar cells. In this paper, a-SiOx:H layers on different orientated c-Si substrates are fabricated. An optimal effective lifetime (τeff) of 4743 μs and corresponding implied open-circuit voltage (iVoc) of 724 mV are obtained on <100>-orientated c-Si wafers. While τeff of 2429 μs and iVoc of 699 mV are achieved on <111>-orientated substrate. The FTIR and XPS results indicate that the a-SiOx:H network consists of SiOx (Si-rich), Si-OH, Si-O-SiHx, SiO2≡Si-Si, and O3≡Si-Si. A passivation evolution mechanism is proposed to explain the different passivation results on different c-Si wafers. By modulating the a-SiOx:H layer, the planar silicon heterojunction solar cell can achieve an efficiency of 18.15%.
    Simulation study on cooperation behaviors and crowd dynamics in pedestrian evacuation
    Ya-Ping Ma(马亚萍), Hui Zhang(张辉)
    Chin. Phys. B, 2020, 29 (3):  038901.  DOI: 10.1088/1674-1056/ab6b14
    Abstract ( 135 )   HTML   PDF (2363KB) ( 95 )  
    Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton (CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.
    Erratum to “Indium doping effect on properties of ZnO nanoparticles synthesized by sol-gel method”
    S Mourad, J El Ghoul, K Omri, K Khirouni
    Chin. Phys. B, 2020, 29 (3):  039901.  DOI: 10.1088/1674-1056/ab77fc
    Abstract ( 77 )   HTML   PDF (711KB) ( 56 )  
    Figure 2 in our original paper [Chin. Phys. B 28 047701 (2019)] was downloaded by default. We present the correct figure in this erratum.
ISSN 1674-1056   CN 11-5639/O4
, Vol. 29, No. 3

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