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Table of contents

    05 May 2017, Volume 26 Issue 5 Previous issue    Next issue
    GENERAL
    Using wavelet multi-resolution nature to accelerate the identification of fractional order system
    Yuan-Lu Li(李远禄), Xiao Meng(孟霄), Ya-Qing Ding(丁亚庆)
    Chin. Phys. B, 2017, 26 (5):  050201.  DOI: 10.1088/1674-1056/26/5/050201
    Abstract ( 207 )   HTML   PDF (411KB) ( 238 )  
    Because of the fractional order derivatives, the identification of the fractional order system (FOS) is more complex than that of an integral order system (IOS). In order to avoid high time consumption in the system identification, the least-squares method is used to find other parameters by fixing the fractional derivative order. Hereafter, the optimal parameters of a system will be found by varying the derivative order in an interval. In addition, the operational matrix of the fractional order integration combined with the multi-resolution nature of a wavelet is used to accelerate the FOS identification, which is achieved by discarding wavelet coefficients of high-frequency components of input and output signals. In the end, the identifications of some known fractional order systems and an elastic torsion system are used to verify the proposed method.
    Smoothing potential energy surface of proteins by hybrid coarse grained approach
    Yukun Lu(卢禹锟), Xin Zhou(周昕), ZhongCan OuYang(欧阳钟灿)
    Chin. Phys. B, 2017, 26 (5):  050202.  DOI: 10.1088/1674-1056/26/5/050202
    Abstract ( 229 )   HTML   PDF (3410KB) ( 179 )  

    Coarse-grained (CG) simulations can more efficiently study large conformational changes of biological polymers but usually lose accuracies in the details. Lots of different hybrid models involving multiple different resolutions have been developed to overcome the difficulty. Here we propose a novel effective hybrid CG (hyCG) approach which mixes the fine-grained interaction and its average in CG space to form a more smoothing potential energy surface. The hyCG approximately reproduces the potential of mean force in the CG space, and multiple mixed potentials can be further combined together to form a single effective force field for achieving both high efficiency and high accuracy. We illustrate the hyCG method in Trp-cage and Villin headpiece proteins to exhibit the folding of proteins. The topology of the folding landscape and thus the folding paths are preserved, while the folding is boosted nearly one order of magnitude faster. It indicates that the hyCG approach could be applied as an efficient force field in proteins.

    Numerical analysis of a dual-pass pumping laser with weak absorption
    Guang-Ju Zhang(张光举), Ma-Li Gong(巩马理), Wen-Qi Zhang(张文启)
    Chin. Phys. B, 2017, 26 (5):  050203.  DOI: 10.1088/1674-1056/26/5/050203
    Abstract ( 250 )   HTML   PDF (616KB) ( 215 )  
    A model for a laser with dual-pass pumping is established, and an equation expressing the mode matching for this structure is presented. Through the numerical analysis of this equation, under the conditions of weak-absorption and effective absorption efficiency, the optimum radius of the pump beam waist as well as the optimum location is fitted to simple formulas, considering the quality of the pump beam, absorption coefficient, and beam waist of the cavity mode. Using these formulas, the laser with dual-pass pumping could be optimized to obtain a high slope efficiency. To test the utility of this model, an Nd:YVO4 laser with dual-pass pumping and weak-absorption was built and optimized according to the results of the calculation. A good agreement between the results of the calculations and the experiment verified the model and the numerical analysis.
    Centroids analysis for circle of confusion in reverse Hartmann test
    Zhu Zhao(赵柱), Mei Hui(惠梅), Zheng-Zheng Xia(夏峥铮), Yue-Jin Zhao(赵跃进)
    Chin. Phys. B, 2017, 26 (5):  050204.  DOI: 10.1088/1674-1056/26/5/050204
    Abstract ( 205 )   HTML   PDF (4044KB) ( 354 )  
    The point spread function (PSF) is investigated in order to study the centroids algorithm in a reverse Hartmann test (RHT) system. Instead of the diffractive Airy disk in previous researches, the intensity of PSF behaves as a circle of confusion (CoC) and is evaluated in terms of the Lommel function in this paper. The fitting of a single spot with the Gaussian profile to identify its centroid forms the basis of the proposed centroid algorithm. In the implementation process, gray compensation is performed to obtain an intensity distribution in the form of a two-dimensional (2D) Gauss function while the center of the peak is derived as a centroid value. The segmental fringe is also fitted row by row with the one-dimensional (1D) Gauss function and reconstituted by averaged parameter values. The condition used for the proposed method is determined by the strength of linear dependence evaluated by Pearson's correlation coefficient between profiles of Airy disk and CoC. The accuracies of CoC fitting and centroid computation are theoretically and experimentally demonstrated by simulation and RHTs. The simulation results show that when the correlation coefficient value is more than 0.9999, the proposed centroid algorithm reduces the root-mean-square error (RMSE) by nearly one order of magnitude, thus achieving an accuracy of ~0.01 pixel or better performance in experiment. In addition, the 2D and 1D Gaussian fittings for the segmental fringe achieve almost the same centroid results, which further confirm the feasibility and advantage of the theory and method.
    Comparative analysis of entanglement measures based on monogamy inequality
    P J Geetha, Sudha, K S Mallesh
    Chin. Phys. B, 2017, 26 (5):  050301.  DOI: 10.1088/1674-1056/26/5/050301
    Abstract ( 228 )   HTML   PDF (744KB) ( 258 )  
    We evaluate the monogamy inequality for symmetric, non-symmetric pure states of importance in terms of squared concurrence, squared entanglement of formation, squared negativity of partial transpose and compare the corresponding tangles. We show that though concurrence and concurrence tangle are zero for two special classes of mixed entangled states, both negativity tangle and entanglement of formation (EOF) tangle turn out to be non-zero. A comparison of different tangles is carried out in each case and it is shown that while the concurrence tangle captures the genuine multiqubit entanglement in N-qubit pure states with N distinct spinors (containing GHZ and superposition of W-, obverse W states) either negativity tangle or EOF tangle is to be used as a better measure of entanglement in the W-class of states with two distinct spinors and in the special classes of mixed multiqubit states.
    Time-energy high-dimensional one-side device-independent quantum key distribution
    Hai-Ze Bao(包海泽), Wan-Su Bao(鲍皖苏), Yang Wang(汪洋), Rui-Ke Chen(陈瑞柯), Hong-Xin Ma(马鸿鑫), Chun Zhou(周淳), Hong-Wei Li(李宏伟)
    Chin. Phys. B, 2017, 26 (5):  050302.  DOI: 10.1088/1674-1056/26/5/050302
    Abstract ( 226 )   HTML   PDF (844KB) ( 266 )  

    Compared with full device-independent quantum key distribution (DI-QKD), one-side device-independent QKD (1sDI-QKD) needs fewer requirements, which is much easier to meet. In this paper, by applying recently developed novel time-energy entropic uncertainty relations, we present a time-energy high-dimensional one-side device-independent quantum key distribution (HD-QKD) and provide the security proof against coherent attacks. Besides, we connect the security with the quantum steering. By numerical simulation, we obtain the secret key rate for Alice's different detection efficiencies. The results show that our protocol can performance much better than the original 1sDI-QKD. Furthermore, we clarify the relation among the secret key rate, Alice's detection efficiency, and the dispersion coefficient. Finally, we simply analyze its performance in the optical fiber channel.

    Matter wave interference of dilute Bose gases in the critical regime
    Xuguang Yue(乐旭广), Shujuan Liu(刘淑娟), Biao Wu(吴飙), Hongwei Xiong(熊宏伟)
    Chin. Phys. B, 2017, 26 (5):  050501.  DOI: 10.1088/1674-1056/26/5/050501
    Abstract ( 244 )   HTML   PDF (588KB) ( 242 )  

    Ultra-cold atomic gases provide a new chance to study the universal critical behavior of phase transition. We study theoretically the matter wave interference for ultra-cold Bose gases in the critical regime. We demonstrate that the interference in the momentum distribution can be used to extract the correlation in the Bose gas. A simple relation between the interference visibility and the correlation length is found and used to interpret the pioneering experiment about the critical behavior of dilute Bose gases [Science 315 1556 (2007)]. Our theory paves the way to experimentally study various types of ultra-cold atomic gases with the means of matter wave interference.

    Generalized analytical solutions for certain coupled simple chaotic systems
    G Sivaganesh, A Arulgnanam
    Chin. Phys. B, 2017, 26 (5):  050502.  DOI: 10.1088/1674-1056/26/5/050502
    Abstract ( 313 )   HTML   PDF (8749KB) ( 419 )  
    We present a generalized analytical solution to the normalized state equations of a class of coupled simple second-order non-autonomous circuit systems. The analytical solutions thus obtained are used to study the synchronization dynamics of two different types of circuit systems, differing only by their constituting nonlinear element. The synchronization dynamics of the coupled systems is studied through two-parameter bifurcation diagrams, phase portraits, and time-series plots obtained from the explicit analytical solutions. Experimental figures are presented to substantiate the analytical results. The generalization of the analytical solution for other types of coupled simple chaotic systems is discussed. The synchronization dynamics of the coupled chaotic systems studied through two-parameter bifurcation diagrams obtained from the explicit analytical solutions is reported for the first time.
    New results for exponential synchronization of linearly coupled ordinary differential systems
    Ping Tong(童评), Shi-Hua Chen(陈士华)
    Chin. Phys. B, 2017, 26 (5):  050503.  DOI: 10.1088/1674-1056/26/5/050503
    Abstract ( 191 )   HTML   PDF (786KB) ( 210 )  

    This paper investigates the exponential synchronization of linearly coupled ordinary differential systems. The intrinsic nonlinear dynamics may not satisfy the QUAD condition or weak-QUAD condition. First, it gives a new method to analyze the exponential synchronization of the systems. Second, two theorems and their corollaries are proposed for the local or global exponential synchronization of the coupled systems. Finally, an application to the linearly coupled Hopfield neural networks and several simulations are provided for verifying the effectiveness of the theoretical results.

    Quasi-periodic solutions and asymptotic properties for the nonlocal Boussinesq equation
    Zhen Wang(王振), Yupeng Qin(秦玉鹏), Li Zou(邹丽)
    Chin. Phys. B, 2017, 26 (5):  050504.  DOI: 10.1088/1674-1056/26/5/050504
    Abstract ( 238 )   HTML   PDF (1688KB) ( 223 )  
    We construct the Hirota bilinear form of the nonlocal Boussinesq (nlBq) equation with four arbitrary constants for the first time. It is special because one arbitrary constant appears with a bilinear operator together in a product form. A straightforward method is presented to construct quasiperiodic wave solutions of the nlBq equation in terms of Riemann theta functions. Due to the specific dispersion relation of the nlBq equation, relations among the characteristic parameters are nonlinear, then the linear method does not work for them. We adopt the perturbation method to solve the nonlinear relations among parameters in the form of series. In fact, the coefficients of the governing equations are also in series form. The quasiperiodic wave solutions and soliton solutions are given. The relations between the periodic wave solutions and the soliton solutions have also been established and the asymptotic behaviors of the quasiperiodic waves are analyzed by a limiting procedure.
    ATOMIC AND MOLECULAR PHYSICS
    Structural stability of ultra-high temperature refractory material MoSi2 and Mo5Si3 under high pressure
    Hao Liang(梁浩), Fang Peng(彭放), Cong Fan(樊聪), Qiang Zhang(张强), Jing Liu(刘景), Shi-Xue Guan(管诗雪)
    Chin. Phys. B, 2017, 26 (5):  053101.  DOI: 10.1088/1674-1056/26/5/053101
    Abstract ( 224 )   HTML   PDF (530KB) ( 435 )  

    In-situ angle dispersive x-ray diffraction (ADXRD) with synchrotron radiation source is performed on an ultra-high temperature refractory of MoSi2 and Mo5Si3 by using a diamond anvil cell (DAC) at room temperature. While the pressure-induced volume reduction is almost constant, the value of the bulk modulus increases with the decrease of molybdenum content in the system. According to the Brich-Murnaghan equation, the bulk modulus 222.1 (2.1) GPa with its pressure derivative 4 of MoSi2, and the bulk modulus 308.4 (7.6) GPa with its pressure derivative 0.7 (0.1) of Mo5Si3 are obtained. The experimental data show that MoSi2 has distinct anisotropic behavior, Mo5Si3 is less anisotropic than MoSi2. The result shows that MoSi2 and Mo5Si3 have the structural stabilities under high pressure. When the pressure reaches up to 41.1 GPa, they can still maintain their body-cantered tetragonal structures.

    Development of adjustable permanent magnet Zeeman slowers for optical lattice clocks
    Xiao-Hang Zhang(张晓航), Xin-Ye Xu(徐信业)
    Chin. Phys. B, 2017, 26 (5):  053701.  DOI: 10.1088/1674-1056/26/5/053701
    Abstract ( 181 )   HTML   PDF (601KB) ( 266 )  

    We develop a permanent-magnet Zeeman slower with adjustable magnets along the longitudinal and radial directions. Produced by four arrays of cylindrical magnets, the longitudinal magnetic field in the slower is tunable if relevant parameters vary, for example, laser detuning or intensity. The proposed Zeeman slower can be reconfigured for Sr atoms. Additionally, we demonstrate that the residual magnetic field produced by the permanent magnets in the magneto-optical trap region can be as small as 0.5 Gs.

    Production of cold CN molecules by photodissociating ICN precursors in brute-force field
    Wen-Xia Xu(徐文霞), Yong-Cheng Yang(杨永成), Lian-Zhong Deng(邓联忠)
    Chin. Phys. B, 2017, 26 (5):  053702.  DOI: 10.1088/1674-1056/26/5/053702
    Abstract ( 166 )   HTML   PDF (360KB) ( 213 )  
    We theoretically investigate the production of cold CN molecules by photodissociating ICN precursors in a brute-force field. The energy shifts and adiabatic orientation of the rotational ICN precursors are first investigated as a function of the external field strength. The dynamical photofragmentation of ICN precursors is numerically simulated for cases with and without orienting field. The CN products are compared in terms of their velocity distributions. A small portion of the CN fragments are recoiled to near zero speed in the lab frame by appropriately selecting the photo energy for dissociation. With a precursor ICN molecular beam of ~1.5 K in rotational temperature, the production of low speed CN fragments can be improved by more than 5 times when an orienting electrical field of 100 kV/cm is present. The corresponding production rate for decelerated fragments with speeds ≤ 50 m/s is simulated to be about ~2.1×10-4 and CN number densities of 108-1010 cm-3 can be reached with precursor ICN densities of ~1012-1014 cm-3 from supersonic expansion.
    ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
    Ultra-wideband RCS reduction using novel configured chessboard metasurface
    Ya-Qiang Zhuang(庄亚强), Guang-Ming Wang(王光明), He-Xiu Xu(许河秀)
    Chin. Phys. B, 2017, 26 (5):  054101.  DOI: 10.1088/1674-1056/26/5/054101
    Abstract ( 334 )   HTML   PDF (2397KB) ( 378 )  
    A novel artificial magnetic conductor (AMC) metasurface is proposed with ultra-wideband 180° phase difference for radar cross section (RCS) reduction. It is composed of two dual-resonant AMC cells, which enable a broadband phase difference of 180°±30° from 7.9 GHz to 19.2 GHz to be achieved. A novel strategy is devised by dividing each rectangular grid in a chessboard configuration into four triangular grids, leading to a further reduction of peak bistatic RCS. Both full-wave simulation and measurement results show that the proposed metasurface presents a good RCS reduction property over an ultra-wideband frequency range.
    Effective dielectric constant model of electromagnetic backscattering from stratified air-sea surface film-sea water medium
    Tao Xie(谢涛), William Perrie, He Fang(方贺), Li Zhao(赵立), Wen-Jin Yu(于文金), Yi-Jun He(何宜军)
    Chin. Phys. B, 2017, 26 (5):  054102.  DOI: 10.1088/1674-1056/26/5/054102
    Abstract ( 198 )   HTML   PDF (608KB) ( 287 )  

    Studies of surface film medium on the sea surface are carried out in this paper for developing the technology to automatically detect and classify sea surface films, and an effective dielectric constant model of electromagnetic backscattering from a stratified air-ocean interface. Numerical results of the new model show the characteristics of effective dielectric constants for the air-sea surface film-sea water medium as follows. The effective dielectric constants decrease with increasing relative dielectric constants of the sea surface films. The effective dielectric constants decrease in horizontal polarization (abbr. HH polarization) and increase in VV vertical polarization (abbr. VV polarization) with increasing radar incident angle. Effective dielectric constants vary with relative sea surface film thickness as a cosinusoidal function of sea surface film thickness. Effective dielectric constant of VV polarization is larger than that of HH polarization. Two potential applications are found with our model, i.e., the retrieval of dielectric constants from the sea surface film, and the film thickness retrieval with our model. Our model has a highly significant influence on improving the technology related to the remote sensing of sea surface films.

    Improved method for studying the propagation dynamics of ultrafast electron pulses based on mean-field models
    Meng-Chao Li(李梦超), Xuan Wang(王瑄), Guo-Qian Liao(廖国前), Yu-Tong Li(李玉同), Jie Zhang(张杰)
    Chin. Phys. B, 2017, 26 (5):  054103.  DOI: 10.1088/1674-1056/26/5/054103
    Abstract ( 223 )   HTML   PDF (441KB) ( 172 )  

    We have studied the propagation dynamics of ultrafast electron pulses by using an improved mean-field model, in which the propagation of the electron pulses across the boundary of the acceleration region is explicitly considered. A large decrease in the speed spread of the electron pulses (we called “boundary kick”) is observed and properly treated leading to a significant improvement in the simulation accuracy, particularly when the density of electrons is very large. We show that our method is consistent with the simulation by the N-particle method, while others can introduce factorial error.

    Theoretical simulation and analysis of large size BMP-LSC by 3D Monte Carlo ray tracing model
    Feng Zhang(张峰), Ning-Ning Zhang(张宁宁), Yi Zhang(张义), Sen Yan(闫森), Song Sun(孙松), Jun Bao(鲍骏), Chen Gao(高琛)
    Chin. Phys. B, 2017, 26 (5):  054201.  DOI: 10.1088/1674-1056/26/5/054201
    Abstract ( 214 )   HTML   PDF (349KB) ( 240 )  

    Luminescent solar concentrators (LSC) can reduce the area of solar cells by collecting light from a large area and concentrating the captured light onto relatively small area photovoltaic (PV) cells, and thereby reducing the cost of PV electricity generation. LSCs with bottom-facing cells (BMP-LSC) can collect both direct light and indirect light, so further improving the efficiency of the PV cells. However, it is hard to analyze the effect of each parameter by experiment because there are too many parameters involved in the BMP-LSC. In this paper, all the physical processes of the light transmission and collection in the BMP-LSC were analyzed. A three-dimensional Monte Carlo ray tracing program was developed to study the transmission of photons in the LSC. A larger-size LSC was simulated, and the effects of dye concentration, the LSC thickness, the cell area, and the cell distance were systematically analyzed.

    Quantum-mathematical model of edge and peak point in Fresnel diffraction through a slit
    Xiao-He Luo(罗晓贺), Hui Mei(惠梅), Qiu-Dong Zhu(朱秋东), Shan-Shan Wang(王姗姗), Yin-Long Hou(侯银龙)
    Chin. Phys. B, 2017, 26 (5):  054202.  DOI: 10.1088/1674-1056/26/5/054202
    Abstract ( 136 )   HTML   PDF (3481KB) ( 172 )  
    The intensity distribution in Fresnel diffraction through a slit includes numerous small fluctuations referred to as ripples. These ripples make the modelling of the intensity distribution complicated. In this study, we examine the characteristics of the Fresnel diffraction intensity distribution to deduce the rule for the peak position and then propose two types of quantum-mathematical models to obtain the distance between the edge and the peak point. The analysis and simulation indicate that the error in the models is below 0.50 μm. The models can also be used to detect the edges of a diffraction object, and we conduct several experiments to measure the slit width. The experimental results reveal that the repetition accuracy of the method can reach 0.23 μm.
    Theoretical study of micro-optical structure fabrication based on sample rotation and two-laser-beam interference
    Yizhen Chen(陈宜臻), Xiangxian Wang(王向贤), Ru Wang(王茹), Hua Yang(杨华), Yunping Qi(祁云平)
    Chin. Phys. B, 2017, 26 (5):  054203.  DOI: 10.1088/1674-1056/26/5/054203
    Abstract ( 1056 )   HTML   PDF (1739KB) ( 482 )  
    A method for fabricating a micro-optical structure based on sample rotation and two-laser-beam interference is proposed. The rotation process is analyzed using the coordinate transformation in matrix presentation and the theoretical expressions of the optical field distributions corresponding to different sample rotations. By rotating the samples and changing the laser wavelength, various special micro-optical structures can be obtained, such as equally spaced concentric rings and irregular trapezoidal lattices; these structures are demonstrated by simulating the corresponding optical field distributions. The proposed approach may be developed into a low-cost laser interference lithography technology for the fabrication of various micro-optical structures.
    Wavefront reconstruction algorithm for wavefront sensing based on binary aberration modes
    Boqing Pang(庞博清), Shuai Wang(王帅), Tao Cheng(程涛), Qingfeng Kong(孔庆峰), Lianghua Wen(文良华), Ping Yang(杨平)
    Chin. Phys. B, 2017, 26 (5):  054204.  DOI: 10.1088/1674-1056/26/5/054204
    Abstract ( 301 )   HTML   PDF (1899KB) ( 290 )  
    We propose a new algorithm for wavefront sensing based on binary intensity modulation. The algorithm is based on the fact that a wavefront can be expended with a series of orthogonal and binary functions, the Walsh series. We use a spatial light modulator (SLM) to produce different binary-intensity-modulation patterns which are the simple linear transformation of the Walsh series. The optical fields under different binary-intensity-modulation patterns are detected with a photodiode. The relationships between the incident wavefront modulated with the patterns and their optical fields are built to determinate the coefficients of the Walsh series. More detailed and strict relationship equations are established with the algorithm by adding new modulation patterns according to the properties of the Walsh functions. An exact value can be acquired by solving the equations. Finally, with the help of phase unwrapping and smoothing, the wavefront can be reconstructed. The advantage of the algorithm is providing an analytical solution for the coefficients of the Walsh series to reconstruct the wavefront. The simulation experiments are presented and the effectiveness of the algorithm is demonstrated.
    Optical encryption scheme based on ghost imaging with disordered speckles
    Yu-dong Zhang(张玉东), Sheng-mei Zhao(赵生妹)
    Chin. Phys. B, 2017, 26 (5):  054205.  DOI: 10.1088/1674-1056/26/5/054205
    Abstract ( 222 )   HTML   PDF (850KB) ( 287 )  
    An optical encryption scheme based on a ghost imaging system with disordered speckles is proposed to obtain a higher security with a small key. In the scheme, Alice produces the random speckle patterns and obtains the detection results with the help of a computational ghost imaging (CGI) system. Then Alice permutes the order of the random speckle patterns and shares the permutation sequence as a secure key to the authorized users. With the secure key, Bob could recover the object with the principle of the CGI system, whereas, the unauthorized users could not obtain any information of the object. The numerical simulations and experimental results show that the proposed scheme is feasible with a small key, simultaneously, it has a higher security. When the eavesdropping ratio (ER) is less than 40%, the eavesdropper cannot acquire any useful information. Meanwhile, the authorized users could recover completely with the secure key.
    Application of multi-pulse optical imaging to measure evolution of laser-produced counter-streaming flows
    Dawei Yuan(袁大伟), Yutong Li(李玉同), Baojun Zhu(朱保君), Yanfei Li(李彦霏), Jiayong Zhong(仲佳勇), Huigang Wei(魏会冈), Chang Liu(刘畅), Xiaoxia Yuan(原晓霞), Zhe Zhang(张喆), Guiyun Liang(梁贵云), Feilu Wang(王菲鹿), Fang Li(李芳), Jiarui Zhao(赵家瑞), Neng Hua(华能), Baoqiang Zhu(朱宝强), Jianqiang Zhu(朱健强), Shaoen Jiang(江少恩), Kai Du(杜凯), Yongkun Ding(丁永坤), Gang Zhao(赵刚), Jie Zhang(张杰)
    Chin. Phys. B, 2017, 26 (5):  054206.  DOI: 10.1088/1674-1056/26/5/054206
    Abstract ( 211 )   HTML   PDF (825KB) ( 238 )  

    A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock (CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part (ne≥ 8-9×1019 cm-3) of the flow is directly measured to be of ~ 106 cm/s between 7 ns and 17 ns. Meanwhile, the average velocity of the low-density-part (ne ≤ 2×1019 cm-3) can be estimated as ~ 107 cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.

    Dynamically controlled optical nonreciprocity of a double-ladder system with spontaneously generated coherence in moving atomic optical lattice
    Nuo Ba(巴诺), Xiang-Yao Wu(吴向尧), Dong-Fei Li(李东飞), Dan Wang(王丹), Jin-You Fei(费金有), Lei Wang(王磊)
    Chin. Phys. B, 2017, 26 (5):  054207.  DOI: 10.1088/1674-1056/26/5/054207
    Abstract ( 225 )   HTML   PDF (1179KB) ( 241 )  

    A four-level double-ladder cold atoms system with spontaneously generated coherence trapped in a moving optical lattice is explored to achieve optical nonreciprocity. When spontaneously generated coherence (SGC) is present, the remarkable contrast optical nonreciprocity of light transmission and reflection can be generated at each induced photonic bandgap in the optical lattice with a velocity of a few m/s. However, when the SGC effect is absent, the optical nonreciprocity becomes weak or even vanishing due to the strong absorption. It is found that the optical nonreciprocity is related to the asymmetric Doppler effect in transmission and reflection, meanwhile the degree and position of optical nonreciprocity can be tuned by the SGC effect and the Rabi frequency of the trigger field.

    Single-photon interconnector composed of two individual one-dimensional nano-waveguides and a single emitter
    Xin-Qin Zhang(张新琴), Xiu-Wen Xia(夏秀文), Jing-Ping Xu(许静平), Ya-Ping Yang(羊亚平)
    Chin. Phys. B, 2017, 26 (5):  054208.  DOI: 10.1088/1674-1056/26/5/054208
    Abstract ( 163 )   HTML   PDF (331KB) ( 200 )  
    Recently, theoretical and experimental nano-sized fundamental devices for optical circuits have been proposed at the single-photon level. The assembly of a realistic optical circuit is now a reality. In this work, we introduce a single-photon interconnector composed of two individual nanowires and an optical N-type four-level emitter that can turn the optical connection on and off optically. Because of dipole-induced transmission at the single-photon level, a single photon can travel between the two nanowires reciprocally, which guarantees its application as an all-optical interconnector.
    Field-free molecular orientation enhanced by tuning the intensity ratio of a three-color laser field
    Zhi-Yuan Huang(黄志远), Ding Wang(王丁), Lang Zheng(郑浪), Wen-Kai Li(黎文开), Rui-Rui Zhao(赵睿睿), Yu-Xin Leng(冷雨欣)
    Chin. Phys. B, 2017, 26 (5):  054209.  DOI: 10.1088/1674-1056/26/5/054209
    Abstract ( 179 )   HTML   PDF (559KB) ( 259 )  

    We theoretically study the field-free molecular orientation induced by a three-color laser field. The three-color laser field with a large asymmetric degree can effectively enhance the molecular orientation. In particular, when the intensity ratio of the three-color laser field is tuned to a proper value of I3:I2:I1 = 0.09:0.5:1, the molecular orientation can be improved by ~ 20% compared with that of the two-color laser field at intensity ratio I2:I1 = 1:1 for the same total laser intensity of 2× 1013 W/cm2. Moreover, we investigate the effect of the carrier-envelope phase (CEP) on the molecular orientation and use the asymmetric degree of the laser field to explain the result. We also show the influences of the laser intensity, rotational temperature, and pulse duration on the molecular orientation. These results are meaningful for the theoretical and experimental studies on the molecular orientation.

    Adjustable quantum coherence effects in a hybrid optomechanical system
    Wen-Qing Xia(夏文清), Ya-Fei Yu(於亚飞), Zhi-Ming Zhang(张智明)
    Chin. Phys. B, 2017, 26 (5):  054210.  DOI: 10.1088/1674-1056/26/5/054210
    Abstract ( 225 )   HTML   PDF (534KB) ( 222 )  

    We propose a system for achieving some adjustable quantum coherence effects, including the normal-mode splitting (NMS), the optomechanically induced transparency (OMIT), and the optomechanically induced absorption (OMIA). In this system, two tunnel-coupled optomechanical cavities are each driven by a coupling field and coupled to an atomic ensemble. Besides, one of the cavities is also injected with a probe field. When the system works under different conditions, we can obtain the NMS, the OMIT, and the OMIA, respectively. These effects can be flexibly adjusted by the tunnel coupling between the two cavities, the power of the coupling lasers, and the coupling strength between the atomic ensembles and the cavity fields. Furthermore, we can realize the OMIT even if the oscillating mirrors have relatively larger decay rates.

    Silica-based microcavity fabricated by wet etching
    H Long(龙浩), W Yang(杨文), L Y Ying(应磊莹), B P Zhang(张保平)
    Chin. Phys. B, 2017, 26 (5):  054211.  DOI: 10.1088/1674-1056/26/5/054211
    Abstract ( 125 )   HTML   PDF (1133KB) ( 257 )  

    Silica whispering gallery mode (WGM) microcavities were fabricated by the buffered oxide etcher and potassium hydroxide wet etching technique without any subsequent chemical or laser treatments. The silicon pedestal underneath was an octagonal pyramid, thus providing a pointed connection area with the top silica microdisk while weakly influencing the resonance modes. The sidewalls of our microdisks were wedge shaped, which was believed to be an advantage for the mode confinement. Efficient coupling from and to the 60 μm diameter microdisk structure was achieved using tapered optical fibres, exhibiting a quality factor of 1.5×104 near a wavelength of 1550 nm. Many resonance modes were observed, and double transverse electric modes were identified by theoretical calculations. The quality factor of the microdisks was also analysed to deduce the cavity roughness. The wet etching technique provides a more convenient avenue to fabricate WGM microdisks than conventional fabrication methods.

    Scaling of Yb-doped photonic crystal fiber to 200 μm core diameter for high beam quality laser output
    Kuo Meng(孟阔), Lian-Qing Zhu(祝连庆), Fei Luo(骆飞)
    Chin. Phys. B, 2017, 26 (5):  054212.  DOI: 10.1088/1674-1056/26/5/054212
    Abstract ( 180 )   HTML   PDF (723KB) ( 214 )  

    The rare earth-doped active fibers not only have ten thousands of square-micron core-area but also deliver a laser with near-diffraction-limited beam quality. However, they have been studied little. In this paper, we design a 200-μm-core-diameter Yb3+-doped photonic crystal fiber with a large pitch in the air-hole cladding region. Simulations demonstrate that only fundamental mode (FM) with a mode field area (MFA) of ~28000 μm2 can be amplified and propagated at the gain saturation, and the beam quality M2 is about 1.5. It is predicted that almost 105 mJ single-pulse energy is available from such a 1.5-meter-length fiber.

    Diode-pumped passively mode-locked sub-picosecond Yb:LuAG ceramic laser
    Jiang-Feng Zhu(朱江峰), Kai Liu(刘凯), Jiang Li(李江), Jun-Li Wang(王军利), Yang Yu(于洋), Hui-Bo Wang(汪会波), Zi-Ye Gao(高子叶), Teng-Fei Xie(谢腾飞), Chao-Yu Li(李超宇), Yu-Bai Pan(潘裕柏), Zhi-Yi Wei(魏志义)
    Chin. Phys. B, 2017, 26 (5):  054213.  DOI: 10.1088/1674-1056/26/5/054213
    Abstract ( 239 )   HTML   PDF (479KB) ( 253 )  

    In this paper the laser activities of a diode-pumped Yb:LuAG ceramic which was prepared by the solid-state reactive sintering method were reported. The maximum output power was 1.86 W in the continuous wave (CW) laser operation, corresponding to a slope efficiency of 53.6%. The CW laser could be tuned from 1030 to 1096 nm by inserting a prism in the cavity. With the assist of a semiconductor saturable absorber mirror (SESAM), passive mode-locking was realized, delivering sub-picosecond pulses with 933 fs duration and an average power of 532 mW at a repetition rate of 90.35 MHz.

    Novel inspection of welded joint microstructure using magneto-optical imaging technology
    Xiang-dong Gao(高向东), Zheng-wen Li(李正文), De-yong You(游德勇), Seiji Katayama
    Chin. Phys. B, 2017, 26 (5):  054214.  DOI: 10.1088/1674-1056/26/5/054214
    Abstract ( 185 )   HTML   PDF (4012KB) ( 208 )  
    A novel method for measuring differences of microstructure by advanced use of the Faraday magneto-optical effect is proposed. Two groups of YAG laser welds on Q235 have been investigated in order to compare MO imaging and traditional methods. Microstructure images have been compared with MO images, and MO diagrams display different colors and gray scales for the base metal, the weld zone, and the heat affected zone. Experimental results indicate that the welded joint microstructure can be inspected by MO imaging without metallographic preparation.
    Influence of low temperature on the surface deformation of deformable mirrors
    Juncheng You(尤俊成), Chunlin Guan(官春林), Hong Zhou(周虹)
    Chin. Phys. B, 2017, 26 (5):  054215.  DOI: 10.1088/1674-1056/26/5/054215
    Abstract ( 201 )   HTML   PDF (9271KB) ( 213 )  
    The two factors which influence the low temperature performance of deformable mirrors (DMs) are the piezoelectric stroke of the actuators and the thermally induced surface deformation of the DM. A new theory was proposed to explain the thermally induced surface deformation of the DM: because the thermal strain between the actuators and the base leads to an additional moment according to the theory of plates, the base will be bent and the bowing base will result in an obvious surface deformation of the facesheet. The finite element method (FEM) was used to prove the theory. The results showed that the thermally induced surface deformation is mainly caused by the base deformation which is induced by the coefficient of thermal expansion (CTE) mismatching; when the facesheet has similar CTE with the actuators, the surface deformation of the DM would be smoother. Then an optimized DM design was adopted to reduce the surface deformation of the DMs at low temperature. The low temperature tests of two 61-element discrete PZT actuator sample deformable mirrors and the corresponding optimized DMs were conducted to verify the simulated results. The results showed that the optimized DMs perform well.
    Numerical investigation on broadband mid-infrared supercontinuum generation in chalcogenide suspended-core fibers
    Kundong Mo(莫坤东), Bo Zhai(翟波), Jianfeng Li(李剑峰), E Coscelli, F Poli, A Cucinotta, S Selleri, Chen Wei(韦晨), Yong Liu(刘永)
    Chin. Phys. B, 2017, 26 (5):  054216.  DOI: 10.1088/1674-1056/26/5/054216
    Abstract ( 200 )   HTML   PDF (3924KB) ( 285 )  

    As2S3 and As2Se3 chalcogenide 3-bridges suspended-core fibers (SCFs) are designed with shifted zero-dispersion wavelengths (ZDWs) at around 1.5 μm, 2 μm, and 2.8 μm, respectively. A generalized nonlinear Schrödinger equation is used to numerically compare supercontinuum (SC) generation in these SCFs pumped at an anomalous dispersion region nearby their ZDWs. Evolutions of the long-wavelength edge (LWE), the power proportion in the long-wavelength region (PPL), and spectral flatness (SF) are calculated and analyzed. Meanwhile, the optimal pump parameters and fiber length are given with LWE, PPL, and SF taken into account. For As2S3 SCFs, SC from a 14 mm-long fiber with a ZDW of 2825 nm pumped at 2870 nm can achieve the longest LWE of ~13 μm and PPL up to ~72%. For As2Se3 SCFs, the LWE of 15.5 μm and the highest PPL of ~87% can be achieved in a 10 mm-long fiber with ZDW of 1982 nm pumped at 2000 nm. Although the As2Se3 SCFs can achieve much longer LWE than the As2S3 SCFs, the core diameter of As2Se3 SCFs will be much smaller to obtain a similar ZDW, leading to lower damage threshold and output power. Finally, the optimal parameters for generating SC spanning over different mid-IR windows are given.

    Impact of cavitation on lesion formation induced by high intensity focused ultrasound
    Pengfei Fan(范鹏飞), Jie Yu(于洁), Xin Yang(杨鑫), Juan Tu(屠娟), Xiasheng Guo(郭霞生), Pintong Huang(黄品同), Dong Zhang(章东)
    Chin. Phys. B, 2017, 26 (5):  054301.  DOI: 10.1088/1674-1056/26/5/054301
    Abstract ( 203 )   HTML   PDF (2452KB) ( 289 )  

    High intensity focused ultrasound (HIFU) has shown a great promise in noninvasive cancer therapy. The impact of acoustic cavitation on the lesion formation induced by HIFU is investigated both experimentally and theoretically in transparent protein-containing gel and ex vivo liver tissue samples. A numerical model that accounts for nonlinear acoustic propagation and heat transfer is used to simulate the lesion formation induced by the thermal effect. The results showed that lesions could be induced in the samples exposed to HIFU with various acoustic pressures and pulse lengths. The measured areas of lesions formed in the lateral direction were comparable to the simulated results, while much larger discrepancy was observed between the experimental and simulated data for the areas of longitudinal lesion cross-section. Meanwhile, a series of stripe-wiped-off B-mode pictures were obtained by using a special imaging processing method so that HIFU-induced cavitation bubble activities could be monitored in real-time and quantitatively analyzed as the functions of acoustic pressure and pulse length. The results indicated that, unlike the lateral area of HIFU-induced lesion that was less affected by the cavitation activity, the longitudinal cross-section of HIFU-induced lesion was significantly influenced by the generation of cavitation bubbles through the temperature elevation resulting from HIFU exposures. Therefore, considering the clinical safety in HIFU treatments, more attention should be paid on the lesion formation in the longitudinal direction to avoid uncontrollable variation resulting from HIFU-induced cavitation activity.

    Noninvasive treatment efficacy monitoring and dose control for high-intensity focused ultrasound therapy using relative electrical impedance variation
    Huidan Su(宿慧丹), Gepu Guo(郭各朴), Qingyu Ma(马青玉), Juan Tu(屠娟), Dong Zhang(章东)
    Chin. Phys. B, 2017, 26 (5):  054302.  DOI: 10.1088/1674-1056/26/5/054302
    Abstract ( 184 )   HTML   PDF (3002KB) ( 284 )  

    As an effective therapeutic modality, high-intensity focused ultrasound (HIFU) can destroy tumour tissues by thermocoagulation with less metastasis, but it is still limited by inaccurate non-invasive temperature monitoring and efficacy evaluation. A model of electrical impedance measurement during HIFU therapy was established using the temperature-impedance relationship. Based on the simulations of acoustic pressure, temperature, and electrical conductivity, the impedance of the phantom was calculated and experimentally demonstrated for different values of acoustic power values and treatment time. We proved that the relative impedance variation (RIV) increases linearly with the increasing treatment time at a fixed acoustic power, and the relative impedance variation rate shows a linear relationship with the acoustic power. The RIV and treatment time required for HIFU treatment efficacy are inversely proportional to the acoustic power and the square of acoustic power, respectively. The favourable results suggest that RIV can be used as an efficient indicator for noninvasive temperature monitoring and efficacy evaluation and may provide new strategy for accurate dose control of HIFU therapy.

    Fully nonlinear (2+1)-dimensional displacement shallow water wave equation
    Feng Wu(吴锋), Zheng Yao(姚征), Wanxie Zhong(钟万勰)
    Chin. Phys. B, 2017, 26 (5):  054501.  DOI: 10.1088/1674-1056/26/5/054501
    Abstract ( 186 )   HTML   PDF (1500KB) ( 231 )  
    Recently, a new (2+1)-dimensional displacement shallow water wave equation (2DDSWWE) was constructed by applying the variational principle of analytic mechanics in the Lagrange coordinates. However, the simplification of the nonlinear term related to the incompressibility of the shallow water in the 2DDSWWE is a disadvantage of this approach. Applying the theory of nonlinear continuum mechanics, we add some new nonlinear terms to the 2DDSWWE and construct a new fully nonlinear (2+1)-dimensional displacement shallow water wave equation (FN2DDSWWE). The presented FN2DDSWWE contains all nonlinear terms related to the incompressibility of shallow water. The exact travelling-wave solution of the proposed FN2DDSWWE is also obtained, and the solitary-wave solution can be deduced from the presented travelling-wave solution under a special selection of integral constants.
    Effect of the Al/O ratio on the Al reaction of aluminized RDX-based explosives
    Qian Zhao(赵倩), Jian-Xin Nie(聂建新), Wei Zhang(张伟), Qiu-Shi Wang(王秋实), Qing-Jie Jiao(焦清介)
    Chin. Phys. B, 2017, 26 (5):  054502.  DOI: 10.1088/1674-1056/26/5/054502
    Abstract ( 158 )   HTML   PDF (696KB) ( 171 )  

    Aluminum (Al) powders are used in composite explosives as a typical reducing agent for improving explosion performance. To understand energy release of aluminum in aluminized RDX-based explosives, a series of thermal measurements and underwater explosion (UNDEX) experiments were conducted. Lithium fluoride (LiF) was added in RDX-based explosives, as a replacement of aluminum, and used in constant temperature calorimeter experiments and UNDEXs. The influence of aluminum powder on explosion heat (Qv) was measured. A rich supply of data about aluminum energy release rate was gained. There are other oxides (CO2, CO, and H2O) in detonation products besides alumina when the content of RDX is maintained at the same levels. Aluminum cannot fully combine with oxygen in the detonation products. To study the relationship between the explosive formulation and energy release, pressure and impulse signals in underwater experiments were recorded and analyzed after charges were initiated underwater. The shock wave energy (Esk), bubble energy (Eb), and total energy (Et) monotony increase with the Al/O ratio, while the growth rates of the shock wave energy, bubble energy, and total energy become slow.

    Experimental investigation on underwater drag reduction using partial cavitation
    Bao Wang(王宝), Jiadao Wang(汪家道), Darong Chen(陈大融), Na Sun(孙娜), Tao Wang(王涛)
    Chin. Phys. B, 2017, 26 (5):  054701.  DOI: 10.1088/1674-1056/26/5/054701
    Abstract ( 184 )   HTML   PDF (844KB) ( 291 )  

    For underwater drag reduction, one promising idea is to form a continuous gas or discrete bubbly layer at the submerged surface. Owing to the lower viscosity of gas than of water, this could considerably reduce underwater drag by achieving slippage at the liquid-gas interface. This paper presents an experimental investigation on underwater drag reduction using partial cavitation. Dense hydrophobic micro-grooved structures sustain gas in the valleys, which can be considered as defects that weaken the strength of the water body. Therefore, partial cavities are easily formed at lower flow speeds, and the dense cavities connect to form a lubricating gas layer at the solid-liquid interface. The results indicate that the proposed method achieves drag reduction without any additional energy or gas-providing devices, which should stimulate the development of underwater vehicles.

    PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
    Simulations of fast component and slow component of SMBI on HL-2A tokamak
    Yong-Fu Shi(史永福), Zhan-Hui Wang(王占辉), Qi-Long Ren(任启龙), Ai-Ping Sun(孙爱萍), De-Liang Yu(余德良), Wen-Feng Guo(郭文峰), Min Xu(许敏)
    Chin. Phys. B, 2017, 26 (5):  055201.  DOI: 10.1088/1674-1056/26/5/055201
    Abstract ( 169 )   HTML   PDF (1684KB) ( 213 )  
    It is very important to improve the penetration depth and fueling efficiency of supersonic molecular beam injection (SMBI) especially for the next generation fusion devices such as ITER. Two components, a fast component (FC) and a slow component (SC), have been observed in the HL-2A SMBI experiments for several years, and the FC can penetrate much more deeply than the common SMBIs which draws a great deal of attention for a better fueling method. It is the first time to the FC and SC of SMBI have been simulated and interpreted in theory and simulation in this paper with the trans-neut module of the BOUT++ code. The simulation results of the FC and SC are clear and distinguishable in the same way as the observation in experiment. For the major mechanism of the FC and SC, it is found that although the difference in the injection velocity has some effect on the penetration depth difference between the FC and SC, it is mainly caused by the self-blocking effect of the first ionized SMB. We also discuss the influence of the initial plasma density on the FC and SC, and the variation of the SC penetration depth with its injection velocity.
    Bow shocks formed by a high-speed laser-driven plasma cloud interacting with a cylinder obstacle Hot!
    Yan-Fei Li(李彦霏), Yu-Tong Li(李玉同), Da-Wei Yuan(袁大伟), Fang Li(李芳), Bao-Jun Zhu(朱保君), Zhe Zhang(张喆), Jia-Yong Zhong(仲佳勇), Bo Han(韩波), Hui-Gang Wei(魏会冈), Xiao-Xing Pei(裴晓星), Jia-Rui Zhao(赵家瑞), Chang Liu(刘畅), Xiao-Xia Yuan(原晓霞), Guo-Qian Liao(廖国前), Yong-Joo Rhee, Xin Lu(鲁欣), Neng Hua(华能), Bao-Qiang Zhu(朱宝强), Jian-Qiang Zhu(朱健强), Zhi-Heng Fang(方智恒), Xiu-Guang Huang(黄秀光), Si-Zu Fu(傅思祖), Gang Zhao(赵刚), Jie Zhang(张杰)
    Chin. Phys. B, 2017, 26 (5):  055202.  DOI: 10.1088/1674-1056/26/5/055202
    Abstract ( 324 )   HTML   PDF (2534KB) ( 306 )  

    A bow shock is formed in the interaction of a high-speed laser-driven plasma cloud with a cylinder obstacle. Its temporal and spatial structures are observed by shadowgraphy and interferometry. The width of the shock transition region is ~ 50 μm, comparable to the ion-ion collision mean free path, which indicates that collision is dominated in the shock probably. The Mach-number of the ablating plasma cloud is ~ 15 at first, and decreases with time resulting in a changing shock structure. A two-dimension hydrodynamics code, USim, is used to simulate the interaction process. The simulated shocks can well reproduce the observed.

    CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
    Diffusion and thermite reaction process of film-honeycomb Al/NiO nanothermite: Molecular dynamics simulations using ReaxFF reactive force field
    Hua-Dong Zeng(曾华东), Zhi-Yang Zhu(祝志阳), Ji-Dong Zhang(张吉东), Xin-Lu Cheng(程新路)
    Chin. Phys. B, 2017, 26 (5):  056101.  DOI: 10.1088/1674-1056/26/5/056101
    Abstract ( 202 )   HTML   PDF (1716KB) ( 462 )  
    The diffusion and thermite reaction process of Al/NiO nanothermite composed of Al nanofilm and NiO nano honeycomb are investigated by molecular dynamics simulations in combination with the ReaxFF. The diffusion and thermite reaction are characterized by measuring energy release, adiabatic reaction temperature, and activation energy. Based on time evolution of atomic configuration and mean square displacement, the initialization of the thermite reaction process of Al/NiO nanothermite results from the diffusion of Al atoms. Under the microcanonical ensemble, it is found that the adiabatic reaction temperature of the thermite reaction process of Al/NiO nanothermite reaches over 5500 K, and activation energy is 8.43 kJ/mol. The release energy of the thermite reaction process of Al/NiO nanothermite is 2.2 kJ/g, which is in accordance with the available experimental value. With the same initial temperature, the adiabatic reaction temperature of the thermite reaction process of Al/NiO nanothermite has a tendency to decrease dramatically as the equivalence ratio increases. On the basis of chemical bond analysis, the initial temperature and equivalence ratio have great effects on the thermite reaction process, but do not significantly affect the average length of Al-Ni nor Al-O bond. Overall, the thermite reaction of film-honeycomb Al/NiO nanothermite is a complicated process instead of a theoretical equation.
    Predicted novel insulating electride compound between alkali metals lithium and sodium under high pressure
    Yang-Mei Chen(陈杨梅), Hua-Yun Geng(耿华运), Xiao-Zhen Yan(颜小珍), Zi-Wei Wang(王紫薇), Xiang-Rong Chen(陈向荣), Qiang Wu(吴强)
    Chin. Phys. B, 2017, 26 (5):  056102.  DOI: 10.1088/1674-1056/26/5/056102
    Abstract ( 187 )   HTML   PDF (1472KB) ( 238 )  

    The application of high pressure can fundamentally modify the crystalline and electronic structures of elements as well as their chemical reactivity, which could lead to the formation of novel materials. Here, we explore the reactivity of lithium with sodium under high pressure, using a swarm structure searching techniques combined with first-principles calculations, which identify a thermodynamically stable Li-Na compound adopting an orthorhombic oP8 phase at pressure above 355 GPa. The formation of Li-Na may be a consequence of strong concentration of electrons transfering from the lithium and the sodium atoms into the interstitial sites, which also leads to open a relatively wide band gap for LiNa-oP8. This is substantially different from atoms sharing or exchanging electrons in common compounds and alloys. In addition, lattice-dynamic calculations indicate that LiNa-oP8 remains dynamically stable when pressure decompresses down to 70 GPa.

    Effect of thermo-mechanical process on structure and high temperature shape memory properties of Ti-15Ta-15Zr alloy
    Xiao-Hang Zheng(郑晓航), Jie-He Sui(隋解和), Zhe-Yi Yang(杨哲一), Guo-Zhang Zhi(张治国), Wei Cai(蔡伟)
    Chin. Phys. B, 2017, 26 (5):  056103.  DOI: 10.1088/1674-1056/26/5/056103
    Abstract ( 193 )   HTML   PDF (1355KB) ( 272 )  
    The effect of thermo-mechanical treatment on microstructure evolution, martensite transformation, and shape memory behavior of Ti-15Ta-15Zr high temperature shape memory alloy were investigated. Different martensite morphologies were found with different annealing temperatures. The Ti-15Ta-15Zr alloy exhibits almost perfect shape memory recovery strain of 6% after annealing at 973 K for 0.5 h.
    Structural, electronic, and magnetic behaviors of 5d transition metal atom substituted divacancy graphene: A first-principles study
    Rafique Muhammad, Yong Shuai(帅永), He-Ping Tan, Hassan Muhammad
    Chin. Phys. B, 2017, 26 (5):  056301.  DOI: 10.1088/1674-1056/26/5/056301
    Abstract ( 160 )   HTML   PDF (4657KB) ( 331 )  

    Structural, electronic, and magnetic behaviors of 5d transition metal (TM) atom substituted divacancy (DV) graphene are investigated using first-principles calculations. Different 5d TM atoms (Hf, Ta, W, Re, Os, Ir, and Pt) are embedded in graphene, these impurity atoms replace 2 carbon atoms in the graphene sheet. It is revealed that the charge transfer occurs from 5d TM atoms to the graphene layer. Hf, Ta, and W substituted graphene structures exhibit a finite band gap at high symmetric K-point in their spin up and spin down channels with 0.783 μB, 1.65 μB, and 1.78 μB magnetic moments, respectively. Ir and Pt substituted graphene structures display indirect band gap semiconductor behavior. Interestingly, Os substituted graphene shows direct band gap semiconductor behavior having a band gap of approximately 0.4 eV in their spin up channel with 1.5 μB magnetic moment. Through density of states (DOS) analysis, we can predict that d orbitals of 5d TM atoms could be responsible for introducing ferromagnetism in the graphene layer. We believe that our obtained results provide a new route for potential applications of dilute magnetic semiconductors and half-metals in spintronic devices by employing 5d transition metal atom-doped graphene complexes.

    Effect of substrate temperature on the morphological, structural, and optical properties of RF sputtered Ge1-xSnx films on Si substrate
    H Mahmodi, M R Hashim
    Chin. Phys. B, 2017, 26 (5):  056801.  DOI: 10.1088/1674-1056/26/5/056801
    Abstract ( 207 )   HTML   PDF (2375KB) ( 338 )  
    In this study, Ge1-xSnx alloy films are co-sputtered on Si(100) substrates using RF magnetron sputtering at different substrate temperatures. Scanning electron micrographs, atomic force microscopy (AFM), Raman spectroscopy, and x-ray photoemission spectroscopy (XPS) are conducted to investigate the effect of substrate temperature on the structural and optical properties of grown GeSn alloy films. AFM results show that RMS surface roughness of the films increases from 1.02 to 2.30 nm when raising the substrate temperature. This increase could be due to Sn surface segregation that occurs when raising the substrate temperature. Raman spectra exhibits the lowest FWHM value and highest phonon intensity for a film sputtered at 140 ℃. The spectra show that decreasing the deposition temperature to 140 ℃ improves the crystalline quality of the alloy films and increases nanocrystalline phase formation. The results of Raman spectra and XPS confirm Ge-Sn bond formation. The optoelectronic characteristics of fabricated metal-semiconductor-metal photodetectors on sputtered samples at room temperature (RT) and 140 ℃ are studied in the dark and under illumination. The sample sputtered at 140 ℃ performs better than the RT sputtered sample.
    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Effect of anionic ordering on the electronic and optical properties of BaTaO2N: TB-mBJ density functional calculation
    K Bettine, O Sahnoun, M Sahnoun, M Driz
    Chin. Phys. B, 2017, 26 (5):  057101.  DOI: 10.1088/1674-1056/26/5/057101
    Abstract ( 284 )   HTML   PDF (2586KB) ( 468 )  
    This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO2N by means of density functional theory (DFT) calculations using the full-potential linearized augmented plane wave (FP-LAPW) method. Three possible structures (P4mm, I4/mmm, and Pmma) are considered according to the TaO4N2 octahedral configurations. The calculated structural parameters are found to be in good agreement with the previous theoretical and experimental results. Moreover, the electronic band structure dispersion, total, and partial densities of electron states are investigated to explain the origin of bandgaps and the contribution of each orbital's species in the valence and the conduction bands. The calculated minimum bandgaps of the P4mm, I4/mmm, and Pmma structures are 1.83 eV, 1.59 eV, and 1.49 eV, respectively. Furthermore, the optical properties represented by the dielectric functions calculated for BaTaO2N show that the I4/mmm phase absorbs the light at a large window in both the visible and UV regions, whereas the other two structures (P4mm and Pmma) are more active in the UV region. Our investigations provide important information for the potential application of this material.
    Strain engineering of electronic and magnetic properties of Ga2S2 nanoribbons
    Bao-Ji Wang(王宝基), Xiao-Hua Li(李晓华), Li-Wei Zhang(张利伟), Guo-Dong Wang(王国东), San-Huang Ke(柯三黄)
    Chin. Phys. B, 2017, 26 (5):  057102.  DOI: 10.1088/1674-1056/26/5/057102
    Abstract ( 202 )   HTML   PDF (1305KB) ( 326 )  

    Using first-principles calculations, we study the tailoring of the electronic and magnetic properties of gallium sulfide nanoribbons (Ga2S2NRs) by mechanical strain. Hydrogen-passivated armchair- and zigzag-edged NRs (ANRs and ZNRs) with different widths are investigated. Significant effects in band gap and magnetic properties are found and analyzed. First, the band gaps and their nature of ANRs can be largely tailored by a strain. The band gaps can be markedly reduced, and show an indirect-direct (I-D) transition under a tensile strain. While under an increasing compressive strain, they undergo a series transitions of I-D-I-D. Five strain zones with distinct band structures and their boundaries are identified. In addition, the carrier effective masses of ANRs are also tunable by the strain, showing jumps at the boundaries. Second, the magnetic moments of (ferromagnetic) ZNRs show jumps under an increasing compressive strain due to spin density redistribution, but are unresponsive to tensile strains. The rich tunable properties by stain suggest potential applications of Ga2S2NRs in nanoelectronics and optoelectronics.

    First-principle study of the structural, electronic, and optical properties of SiC nanowires
    Wei-Hu Zhang(张威虎), Fu-Chun Zhang(张富春), Wei-Bin Zhang(张伟斌), Shao-Lin Zhang(张绍林), Woochul Yang
    Chin. Phys. B, 2017, 26 (5):  057103.  DOI: 10.1088/1674-1056/26/5/057103
    Abstract ( 199 )   HTML   PDF (1586KB) ( 630 )  
    We preform first-principle calculations for the geometric, electronic structures and optical properties of SiC nanowires (NWs). The dielectric functions dominated by electronic interband transitions are investigated in terms of the calculated optical response functions. The calculated results reveal that the SiC NW is an indirect band-gap semiconductor material except at a minimum SiC NW (n=12) diameter, showing that the NW (n=12) is metallic. Charge density indicates that the Si-C bond of SiC NW has mixed ionic and covalent characteristics: the covalent character is stronger than the ionic character, and shows strong s-p hybrid orbit characteristics. Moreover, the band gap increases as the SiC NW diameter increases. This shows a significant quantum size and surface effect. The optical properties indicate that the obvious dielectric absorption peaks shift towards the high energy, and that there is a blue shift phenomenon in the ultraviolet region. These results show that SiC NW is a promising optoelectronic material for the potential applications in ultraviolet photoelectron devices.
    Thermal emission properties of one-dimensional grating with different parameters
    Weixin Lin(林伟新), Guozhou Li(李国洲), Qiang Li(李强), Hongjin Hu(胡宏锦), Fang Han(韩防), Fanwei Zhang(张樊伟), Lijun Wu(吴立军)
    Chin. Phys. B, 2017, 26 (5):  057301.  DOI: 10.1088/1674-1056/26/5/057301
    Abstract ( 250 )   HTML   PDF (3117KB) ( 244 )  

    Thermal emission is often presented as a typical incoherent process. Incorporating periodic structures on the tungsten surface offers the possibility to obtain coherent thermal emission sources. Here we illustrate grating as an example to examine the influence of the geometric parameters on the thermal emission properties. It is found that for very shallow gratings, only surface plasmon polariton (SPP) modes can be excited and the emission efficiency is closely related with the filling factor. When the ratio of the depth to period of the grating is in the range from 1/20 to 1/2, the field between the adjacent corners can be coupled to each other across the air gap for the filling factor larger than 0.5 and produce a similar resonance as in an air rod. Further increase of the grating depth can cause the groove of the grating forming metal-insulator-metal (MIM) structures and induce surface plasmon standing wave modes. Our investigations will not only be helpful for manipulating thermal emission properties according to applications, but also help us understand the coupling mechanism between the incident electromagnetism waves and gratings with different parameters in various research fields.

    Dielectric loaded surface plasmon polariton properties of the Al2O3-Al nanostructure
    Jie Yao(姚洁), Qi Wei(魏琦), Qing-Yu Ma(马青玉), Da-Jian Wu(吴大建)
    Chin. Phys. B, 2017, 26 (5):  057302.  DOI: 10.1088/1674-1056/26/5/057302
    Abstract ( 128 )   HTML   PDF (296KB) ( 240 )  

    Surface plasmons (SPs) in ultraviolet (UV) have attracted a great deal of attention because of their emerging applications in energy resources, environmental protection, and biotechnology. In this article, the dielectric loaded surface plasmon polariton (DLSPP) properties of the Al2O3-Al nanostructure are investigated theoretically. Sharp SP responses can be obtained in deep UV by setting an insulator grating on the aluminum film. It is found that the height of the grating element, the lattice parameter, and the filling factor can all modulate the DLSPPs of the Al2O3-Al nanostructure. We further find that this structure is sensitive to the embedding medium and can serve as a refractive index sensor in the UV region. The corresponding sensitivity increases with the decrease of the filling factor. The Al2O3-Al nanostructure may be useful for medical diagnostics and biotechnology in deep UV.

    Generation of Fabry-Pérot oscillations and Dirac state in two-dimensional topological insulators by gate voltage
    Bin Xu(徐斌), Rao Li(李饶), Hua-Hua Fu(傅华华)
    Chin. Phys. B, 2017, 26 (5):  057303.  DOI: 10.1088/1674-1056/26/5/057303
    Abstract ( 188 )   HTML   PDF (1527KB) ( 233 )  
    We investigate electron transport through HgTe ribbons embedded by strip-shape gate voltage through using a non-equilibrium Green function technique. The numerical calculations show that as the gate voltage is increased, an edge-related state in the valence band structure of the system shifts upwards, then hangs inside the band gap and merges into the conduction band finally. It is interesting that as the gate voltage is increased continuously, another edge-related state in the valence band also shifts upwards in the small-k region and contacts the previous one to form a Dirac cone in the band structure. Meanwhile in this process, the conductance spectrum displays as multiple resonance peaks characterized by some strong antiresonance valleys in the band gap, then behaves as Fabry-Pérot oscillations and finally develops into a nearly perfect quantum plateau with a value of 2e2/h. These results give a physical picture to understand the formation process of the Dirac state driven by the gate voltage and provide a route to achieving particular quantum oscillations of the electronic transport in nanodevices.
    Superconductivity in self-flux-synthesized single crystalline R2Pt3Ge5(R = La, Ce, Pr) Hot!
    Q Sheng(盛琪), J Zhang(张建), K Huang(黄百畅), Z Ding(丁兆峰), X Peng(彭小冉), C Tan(谭程), L Shu(殳蕾)
    Chin. Phys. B, 2017, 26 (5):  057401.  DOI: 10.1088/1674-1056/26/5/057401
    Abstract ( 296 )   HTML   PDF (1260KB) ( 447 )  

    In order to study the basic superconductivity properties of Pr2Pt3Ge5, we synthesized the single crystalline samples by the Pt-Ge self-flux method. R2Pt3Ge5 (R = La, Ce) were also grown for a systematic study. Zero-resistivity was observed in both the La- and Pr-based samples below the reported superconducting transition temperatures. However, magnetic susceptibility measurements showed low superconductivity volume fractions in both La2Pt3Ge5 and Pr2Pt3Ge5 (less than 2%). Ce2Pt3Ge5 did not show any signature of superconductivity. From the specific heat measurements, we did not observe a superconducting transition peak in Pr2Pt3Ge5, suggesting that it is not a bulk superconductor. The magnetic susceptibility and heat capacity measurements revealed two antiferromagnetic (AFM) orders in Pr2Pt3Ge5 at TN1 = 4.2 K and TN2=3.5 K, as well as a single AFM transition at TN = 3.8 K in Ce2Pt3Ge5.

    RAPID COMMUNICATION
    Doping Mn into (Li1-xFex)OHFe1-ySe superconducting crystals via ion-exchange and ion-release/introduction syntheses Hot!
    Huaxue Zhou(周花雪), Shunli Ni(倪顺利), Jie Yuan(袁洁), Jun Li(李军), Zhongpei Feng(冯中沛), Xingyu Jiang(江星宇), Yulong Huang(黄裕龙), Shaobo Liu(刘少博), Yiyuan Mao(毛义元), Fang Zhou(周放), Kui Jin(金魁), Xiaoli Dong(董晓莉), Zhongxian Zhao(赵忠贤)
    Chin. Phys. B, 2017, 26 (5):  057402.  DOI: 10.1088/1674-1056/26/5/057402
    Abstract ( 551 )   HTML   PDF (1050KB) ( 582 )  

    We report the success in introducing Mn into (Li1-xFex)OHFe1-ySe superconducting crystals by applying two different hydrothermal routes, ion exchange (1-step) and ion release/introduction (2-step). The micro-region x-ray diffraction and energy dispersive x-ray spectroscopy analyses indicate that Mn has been doped into the lattice, and its content in the 1-step fabricated sample is higher than that in the 2-step one. Magnetic susceptibility and electric transport properties reveal that Mn doping influences little on the superconducting transition, regardless of 1-step or 2-step routes. By contrast, the characteristic temperature T*, at which the negative Hall coefficient reaches its minimum, is significantly reduced by Mn doping. This implies that the hole carriers contribution is obviously modified, and hence the hole band might have no direct relationship with the superconductivity in (Li1-xFex)OHFe1-ySe superconductors. Our present hydrothermal methods of ion exchange and ion release/introduction provide an efficient way for elements substitution/doping into (Li1-xFex)OHFe1-ySe superconductors, which will promote the in-depth investigations on the role of multiple electron and hole bands and their interplay with the high-temperature superconductivity in the FeSe-based superconductors.

    CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
    Structure dependence of magnetic properties in yttrium iron garnet by metal-organic decomposition method
    Yuan Liu(刘园), Xiang Wang(王翔), Jie Zhu(朱杰), Runsheng Huang(黄润生), Dongming Tang(唐东明)
    Chin. Phys. B, 2017, 26 (5):  057501.  DOI: 10.1088/1674-1056/26/5/057501
    Abstract ( 213 )   HTML   PDF (848KB) ( 205 )  

    The yttrium iron garnet (YIG) samples are prepared at different temperatures from 900 ℃ to 1300 ℃ by the metal-organic decomposition (MOD) method. The chemical composition and crystal structure of the samples are studied by scanning electron microscope (SEM), XRD, and Mössbauer spectrometer. It is shown that the ratio of ferric ions on two types of sites, the octahedral and the tetrahedral, is increased with the sintering temperature. At 1300 ℃, the pure garnet phase has been obtained, in which the ferric ions ratio is 2:3 leading to the minimum magnetic coercivity and maximum saturation magnetization. These results provide a route to synthesize pure YIG materials as the basic materials used in various spintronics applications.

    Influence of misch metal content on microstructure and magnetic properties of R-Fe-B magnets sintered by dual alloy method
    Rong-Xiang Shang(商荣翔), Jie-Fu Xiong(熊杰夫), Dan Liu(刘丹), Shu-Lan Zuo(左淑兰), Xin Zhao(赵鑫), Rui Li(李锐), Wen-Liang Zuo(左文亮), Tong-Yun Zhao(赵同云), Ren-Jie Chen(陈仁杰), Ji-Rong Sun(孙继荣), Bao-Gen Shen(沈保根)
    Chin. Phys. B, 2017, 26 (5):  057502.  DOI: 10.1088/1674-1056/26/5/057502
    Abstract ( 186 )   HTML   PDF (707KB) ( 192 )  

    MM14Fe79.9B6.1/Nd13.5Fe80.5B6 magnets were fabricated by dual alloy method (MM, misch metal). Some magnets have two Curie temperatures. Curie temperatures Tc1 corresponds to the main phase which contains more LaCe, and Tc1 decreases from 276.5 ℃ to 256.6 ℃ with the content of MM increasing from 30.3 at.% to 50.6 at.%. The variation of Br with the increase of MM indicates the existence of inter-grain exchange coupling in the magnets. When MM/R ≤ 30.3 at.%, the magnetic properties can reach the level of the intrinsic coercivity Hcj ≥ 7.11 kOe and the maximum energy product (BH)max ≥ 41 MGOe. Compared with Nd, La and Ce are easier to diffuse to the grain boundaries in the sintering process, and this will cause the decrease of Hcj. Due to the diffusion between the grains, the atomic ratio of La, Ce, Pr, and Nd in each grain is different and the percentage of Nd in all grains is higher than that in misch metal.

    Single-layer broadband planar antenna using ultrathin high-efficiency focusing metasurfaces
    Hai-Sheng Hou(侯海生), Guang-Ming Wang(王光明), Hai-Peng Li(李海鹏), Wen-Long Guo(郭文龙), Tang-jing Li(李唐景), Tong Cai(蔡通)
    Chin. Phys. B, 2017, 26 (5):  057701.  DOI: 10.1088/1674-1056/26/5/057701
    Abstract ( 209 )   HTML   PDF (4287KB) ( 486 )  
    Phase gradient metasurfaces (PGMS) offer a fascinating ability to control the amplitude and phase of the electromagnetic (EM) waves on a subwavelength scale, resulting in new applications of designing novel microwave devices with improved performances. In this paper, a reflective symmetrical element, consisting of orthogonally I-shaped structures, has been demonstrated with an approximately parallel phase response from 15 GHz to 22 GHz, which results in an interesting wideband property. For practical design, a planar antenna is implemented by a well-optimized focusing metasurface and excited by a self-designed Vivaldi antenna at the focus. Numerical and experimental results coincide well. The planar antenna has a series of merits such as a wide 3-dB gain bandwidth of 15-22 GHz, an average gain enhancement of 16 dB, a comparable aperture efficiency of better than 45% at 18 GHz, and also a simple fabrication process. The proposed reflective metasurface opens up a new avenue to design wideband microwave devices.
    Performance and reliability improvement of La2O3/Al2O3 nanolaminates using ultraviolet ozone post treatment
    Ji-Bin Fan(樊继斌), Hong-Xia Liu(刘红侠), Bin Sun(孙斌), Li Duan(段理), Xiao-Chen Yu(于晓晨)
    Chin. Phys. B, 2017, 26 (5):  057702.  DOI: 10.1088/1674-1056/26/5/057702
    Abstract ( 248 )   HTML   PDF (1315KB) ( 273 )  

    La-based binary or ternary compounds have recently attracted a great deal of attention as a potential candidate to replace the currently used Hf-based dielectrics in future transistor and capacitor devices for sub-22 generation. However, the hygroscopic nature of La2O3 hampers its application as dielectrics in electron devices. To cope with this challenge, ultraviolet (UV) ozone post treatment is proposed to suppress the moisture absorption in the H2O-based atomic layer deposition (ALD) La2O3/Al2O3 nanolaminates which is related to the residual hydroxyl/hydrogen groups after annealing. The x-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (AFM) results indicate that the moisture absorption of the H2O-based ALD La2O3/Al2O3 nanolaminates is efficiently suppressed after 600 ℃ annealing, and the electrical characteristics are greatly improved.

    Fabrication of broadband antireflection coatings using broadband optical monitoring mixed with time monitoring
    Qi-Peng Lv(吕起鹏), Song-Wen Deng(邓淞文), Shao-Qian Zhang(张绍骞), Fa-Quan Gong(公发全), Gang Li(李刚)
    Chin. Phys. B, 2017, 26 (5):  057801.  DOI: 10.1088/1674-1056/26/5/057801
    Abstract ( 146 )   HTML   PDF (346KB) ( 317 )  
    Multi-layer optical coatings with complex spectrum requirements, such as multi-band pass filters, notch filters, and ultra-broadband antireflection coating, which usually contain very thin layers and sensitive layers, are difficult to be fabricated using a quartz crystal monitoring method or a single wavelength optical monitoring system (SWLOMS). In this paper, a broadband antireflection (AR) coating applied in the wavelength range from 800 nm to 1800 nm was designed and deposited by ion beam sputtering (IBS). Ta2O5 and SiO2 were chosen as high and low refractive index coating materials, respectively. The optimized coating structure contains 9 non-quarter-wave (QW) layers totally with ultra-thin layers and sensitive layers in this coating stack. In order to obtain high transmittance, it is very important to realize the thickness accurate control on these thin layers and sensitive layers. A broadband optical monitoring mixed with time monitoring strategy was successfully used to control the layer thickness during the deposition process. At last, the measured transmittance of AR coating is quite close to the theoretical value. A 0.6% variation in short wavelength edge across the central 180 mm diameter is demonstrated. A spectrum shift of less than 0.5% for 2 continuous runs is also presented.
    RAPID COMMUNICATION
    Tunable monoenergy positron annihilation spectroscopy of polyethylene glycol thin films
    Peng Kuang(况鹏), Xiao-Long Han(韩小龙), Xing-Zhong Cao(曹兴忠), Rui Xia(夏锐), Peng Zhang(张鹏), Bao-Yi Wang(王宝义)
    Chin. Phys. B, 2017, 26 (5):  057802.  DOI: 10.1088/1674-1056/26/5/057802
    Abstract ( 242 )   HTML   PDF (1152KB) ( 287 )  

    Doppler broadening and coincidence Doppler broadening of annihilation radiation experiments have been performed in three kinds of polyethylene glycol (PEG) membrane formed with different average molecular weight using the tunable monoenergy slow positron probe as a function of implantion energy. The obtained positron annihilation parameters are interpreted from two aspects: surface effect and differences in micro-structure or chemical environment of positron annihilation. The experimental results show that the regulation of densification of PEG molecular packing and distribution uniformity from the near surface layer to the bulk region in the film forming process can be well realized by changing its molecular weight. Combining a variable monoenergetic slow positron beam and these two positron annihilation spectroscopy methods is a powerful tool to study positron annihilation characteristics and for polymeric thin-film fine structure analysis.

    INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    Carbon-nanodot-coverage-dependent photocatalytic performance of carbon nanodot/TiO2 nanocomposites under visible light
    Ming-Ye Sun(孙明烨), You-Jin Zheng(郑友进), Lei Zhang(张蕾), Li-Ping Zhao(赵立萍), Bing Zhang(张冰)
    Chin. Phys. B, 2017, 26 (5):  058101.  DOI: 10.1088/1674-1056/26/5/058101
    Abstract ( 200 )   HTML   PDF (994KB) ( 229 )  
    Carbon nanodots (CDs) with visible absorption band and TiO2 are integrated to enhance the photosensitivity of TiO2. The CD/TiO2 nanocomposites show obvious CD-coverage-dependent photocatalytic performance. The CD/TiO2 nanocomposites with moderate CD coverge exhibit the highest photocatalytic activity after being irradiated with visible light, which is more excellent than that of TiO2. Too little CD coverage could result in poor visible light absorption, which limits the photocatalytic performance of CD/TiO2 nanocomposites. While, too much CD coverage weakens the photocatalytic activity of CD/TiO2 nanocomposites by restraining the extraction of conduction band electrons within TiO2 to generate active oxygen radicals and the electron transfer (ET) process from CDs to TiO2. These results indicate that rational regulation of CD coverage and the realization of efficient ET process are important means to optimize the photocatalytic performance of CD/TiO2 nanocomposites.
    Synthesis of N-type semiconductor diamonds with sulfur, boron co-doping in FeNiMnCo-C system at high pressure and high temperature
    He Zhang(张贺), Shangsheng Li(李尚升), Taichao Su(宿太超), Meihua Hu(胡美华), Hongan Ma(马红安), Xiaopeng Jia(贾晓鹏), Yong Li(李勇)
    Chin. Phys. B, 2017, 26 (5):  058102.  DOI: 10.1088/1674-1056/26/5/058102
    Abstract ( 198 )   HTML   PDF (1171KB) ( 296 )  

    A series of diamonds with boron and sulfur co-doping were synthesized in the FeNiMnCo-C system by temperature gradient growth (TGG) under high pressure and high temperature (HPHT). Because of differences in additives, the resulting diamond crystals were colorless, blue-black, or yellow. Their morphologies were slab, tower, or minaret-like. Analysis of the x-ray photoelectron spectra (XPS) of these diamonds shows the presence of B, S, and N in samples from which N was not eliminated. But only the B dopant was assuredly incorporated in the samples from which N was eliminated. Resistivity and Hall mobility were 8.510 Ω·cm and 760.870 cm2/V·s, respectively, for a P-type diamond sample from which nitrogen was eliminated. Correspondingly, resistivity and Hall mobility were 4.211×105Ω·cm and 76.300 cm2/V·s for an N-type diamond sample from which nitrogen was not eliminated. Large N-type diamonds of type Ib with B-S doping were acquired.

    Wavelength dependence of electron localization of H2+ and its isotopomers in the UV-pump-probe scheme
    Shan Xue(薛山), Hong-Chuan Du(杜洪川), Sheng-Jun Yue(岳生俊), Hong-Mei Wu(吴红梅), Bi-Tao Hu(胡碧涛)
    Chin. Phys. B, 2017, 26 (5):  058201.  DOI: 10.1088/1674-1056/26/5/058201
    Abstract ( 181 )   HTML   PDF (4345KB) ( 569 )  

    The wavelength dependence of electron localization of H2+ and its isotopomers in the ultraviolet pump-probe scheme is investigated by numerically solving the time-dependent Schrödinger equation. By combining with a semiclassical method, an effective analytical formula expressed in the adiabatic representation is established to describe the localization probability with several zero crossings. A stable zone with respect to the laser intensity and carrier envelope phase is found at a relatively long probe wavelength. Finally, the critical probe wavelengths to reach at the stable zone are derived by using the three-dimensional model. Slower nuclear motion of heavier isotopomers leads to a longer critical wavelength.

    Removal of rhodamine B from aqueous solutions using vanadium pentoxide/titanium butyl oxide hybrid xerogels
    Surayya Mukhtar, Mona Liu, Jie Han, Wei Gao
    Chin. Phys. B, 2017, 26 (5):  058202.  DOI: 10.1088/1674-1056/26/5/058202
    Abstract ( 150 )   HTML   PDF (1960KB) ( 295 )  
    A stable and insoluble V2O5·nH2O/tetra-n-butyl titanate (TBO) hybrid xerogel was synthesized by the sol-gel method. This novel material proved to be an efficient absorbent with an absorption capacity of 179 mg·g-1 for Rhodamine B (RhB) in water due to its unique layered structure, which can effectively accommodate RhB molecules between its layers as demonstrated by XRD and FTIR spectroscopic analyses.
    Improving power conversion efficiency of perovskite solar cells by cooperative LSPR of gold-silver dual nanoparticles
    Peng Liu(刘鹏), Bing-chu Yang(杨兵初), Gang Liu(刘钢), Run-sheng Wu(吴闰生), Chu-jun Zhang(张楚俊), Fang Wan(万方), Shui-gen Li(李水根), Jun-liang Yang(阳军亮), Yong-li Gao(高永立), Cong-hua Zhou(周聪华)
    Chin. Phys. B, 2017, 26 (5):  058401.  DOI: 10.1088/1674-1056/26/5/058401
    Abstract ( 286 )   HTML   PDF (1270KB) ( 361 )  

    Enhancing optical and electrical performances is effective in improving power conversion efficiency of photovoltaic devices. Here, gold and silver dual nanoparticles were imported and embedded in the hole transport layer of perovskite solar cells. Due to the cooperative localized surface plasmon resonance of these two kinds of metal nanostructures, light harvest of perovskite material layer and the electrical performance of device were improved, which finally upgraded short circuit current density by 10.0%, and helped to increase power conversion efficiency from 10.4% to 11.6% under AM 1.5G illumination with intensity of 100 mW/cm2. In addition, we explored the influence of silver and gold nanoparticles on charge carrier generation, dissociation, recombination, and transportation inside perovskite solar cells.

    RAPID COMMUNICATION
    High quality factor superconducting coplanar waveguide fabricated with TiN
    Qiang Liu(刘强), Guang-Ming Xue(薛光明), Xin-Sheng Tan(谭新生), Hai-Feng Yu(于海峰), Yang Yu(于扬)
    Chin. Phys. B, 2017, 26 (5):  058402.  DOI: 10.1088/1674-1056/26/5/058402
    Abstract ( 264 )   HTML   PDF (1014KB) ( 255 )  

    We fabricated TiN coplanar waveguides using standard lithography techniques followed by ICP etch. In order to achieve high quality factor, we investigated the film growth by choosing different deposition conditions for various substrates. Quality factors of waveguide resonators were measured at 20 mK in both high and low microwave power limits. An inner quality factor of several million was achieved at high power limit for a predominantly (200)-oriented TiN film which was grown on HF cleaned silicon wafer. A quality factor of larger than one million was achieved at high power limit for TiN film grown on sapphire.

    INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
    An optimized fitting function with least square approximation inInAs/AlSb HFET small-signal model for characterizingthe frequency dependency of impact ionization effect
    He Guan(关赫), Hui Guo(郭辉)
    Chin. Phys. B, 2017, 26 (5):  058501.  DOI: 10.1088/1674-1056/26/5/058501
    Abstract ( 171 )   HTML   PDF (1375KB) ( 170 )  
    An enhanced small-signal model is introduced to model the influence of the impact ionization effect on the performance of InAs/AlSb HFET, in which an optimized fitting function D(ωτi) in the form of least square approximation is proposed in order to further enhance the accuracy in modeling the frequency dependency of the impact ionization effect. The enhanced model with D(ωτi) can accurately characterize the key S parameters of InAs/AlSb HFET in a wide frequency range with a very low error function EF. It is demonstrated that the new fitting function D(ωτi) is helpful in further improving the modeling accuracy degree.
    Modeling and understanding of the thermal failure induced by high power microwave in CMOS inverter
    Yu-Hang Zhang(张宇航), Chang-Chun Chai(柴常春), Yang Liu(刘阳), Yin-Tang Yang(杨银堂), Chun-Lei Shi(史春蕾), Qing-Yang Fan(樊庆扬), Yu-Qian Liu(刘彧千)
    Chin. Phys. B, 2017, 26 (5):  058502.  DOI: 10.1088/1674-1056/26/5/058502
    Abstract ( 171 )   HTML   PDF (1101KB) ( 248 )  
    The thermal failure induced by high power microwave (HPM) in a complementary metal oxide semiconductor (CMOS) inverter is investigated and its dependence on microwave parameters is discussed in detail. An analytical model of the temperature distribution is established and the relationships between hotspot temperature and pulse width and between hotspot temperature and frequency are predicted, which reveals a more severe rise in temperature under the influence of microwave with longer width and lower frequency. The temperature variation mechanism and the theoretical temperature model are validated and explained by the simulation. Furthermore, variation trend of damage threshold with microwave parameters is derived theoretically, and the conclusions are consistent with simulation results and reported data.
    RAPID COMMUNICATION
    A high-temperature superconducting filter withcontrollable transmission zero
    Tianqi Gao(高天琪), Bin Wei(魏斌), Yong Heng(衡勇)
    Chin. Phys. B, 2017, 26 (5):  058503.  DOI: 10.1088/1674-1056/26/5/058503
    Abstract ( 236 )   HTML   PDF (507KB) ( 203 )  

    This paper presents a novel microstrip feedline structure to introduce an extra and controllable transmission zero (TZ) with high rejection for a narrowband filter. This structure loads a reconfigurable capacitor at the end of the input feedline without changing the main structure of the filter. The capacitor is recognized by a 2-bit inter-digital capacitor array. The asymmetrical microstrip feedline structure is suitable for multiple-pole filter designs. A low-loss six-pole high-temperature superconducting bandpass filter with a reconfigurable TZ is designed and fabricated. The center frequency of the filter is 5.22 GHz with TZ at the lower stopband. The TZ can be tuned among four different states. The out-of-band rejection at the TZ frequency is higher than 90 dB, and the insertion loss is lower than 0.92 dB. The measured results are consistent with the simulations.

ISSN 1674-1056   CN 11-5639/O4
, Vol. 26, No. 5

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