Table of contents

05 September 2016, Volume 25 Issue 9 Previous issue    Next issue

GENERAL

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Localized waves in three-component coupled nonlinear Schrödinger equation Tao Xu(徐涛), Yong Chen(陈勇) Chin. Phys. B, 2016, 25 (9):  090201.  DOI: 10.1088/1674-1056/25/9/090201 Abstract ( 693 )   HTML   PDF (2207KB) ( 403 )   We study the generalized Darboux transformation to the three-component coupled nonlinear Schrödinger equation. First- and second-order localized waves are obtained by this technique. In first-order localized wave, we get the interactional solutions between first-order rogue wave and one-dark, one-bright soliton respectively. Meanwhile, the interactional solutions between one-breather and first-order rogue wave are also given. In second-order localized wave, one-dark-one-bright soliton together with second-order rogue wave is presented in the first component, and two-bright soliton together with second-order rogue wave are gained respectively in the other two components. Besides, we observe second-order rogue wave together with one-breather in three components. Moreover, by increasing the absolute values of two free parameters, the nonlinear waves merge with each other distinctly. These results further reveal the interesting dynamic structures of localized waves in the three-component coupled system.

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Statistical second-order two-scale analysis and computation for heat conduction problem with radiation boundary condition in porous materials Zhi-Qiang Yang(杨志强), Shi-Wei Liu(刘世伟), Yi Sun(孙毅) Chin. Phys. B, 2016, 25 (9):  090202.  DOI: 10.1088/1674-1056/25/9/090202 Abstract ( 805 )   HTML   PDF (2703KB) ( 312 )   This paper discusses a statistical second-order two-scale (SSOTS) analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials. Firstly, the microscopic configuration for the structure with random distribution is briefly characterized. Secondly, the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell. Then, the statistical prediction algorithm based on the proposed two-scale model is described in detail. Finally, some numerical experiments are proposed, which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of porous materials and demonstrating its significant applications in actual engineering computation.

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Finite-difference time-domain modeling of curved material interfaces by using boundary condition equations method Jia Lu(卢佳), Huaichun Zhou(周怀春) Chin. Phys. B, 2016, 25 (9):  090203.  DOI: 10.1088/1674-1056/25/9/090203 Abstract ( 674 )   HTML   PDF (869KB) ( 490 )   To deal with the staircase approximation problem in the standard finite-difference time-domain (FDTD) simulation, the two-dimensional boundary condition equations (BCE) method is proposed in this paper. In the BCE method, the standard FDTD algorithm can be used as usual, and the curved surface is treated by adding the boundary condition equations. Thus, while maintaining the simplicity and computational efficiency of the standard FDTD algorithm, the BCE method can solve the staircase approximation problem. The BCE method is validated by analyzing near field and far field scattering properties of the PEC and dielectric cylinders. The results show that the BCE method can maintain a second-order accuracy by eliminating the staircase approximation errors. Moreover, the results of the BCE method show good accuracy for cylinder scattering cases with different permittivities.

SPECIAL TOPIC—Physical research in liquid crystal

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Random lasing from dye-doped negative liquid crystals using ZnO nanoparticles as tunable scatters Long-Wu Li(李龙武), Zhen-Zhen Shang(尚真真), Luogen Deng(邓罗根) Chin. Phys. B, 2016, 25 (9):  090301.  DOI: 10.1088/1674-1056/25/9/090301 Abstract ( 732 )   HTML   PDF (1620KB) ( 454 )   This work demonstrates the realization of a lasing in scattering media, which contains dispersive solution of ZnO nanoparticles (NPs) and laser dye 4-dicyanomethylene-2-methyle-6-(p-dimethylaminostyryl)-4H-pyran(DCM) in negative liquid crystals (LCs) that was injected into a cell. The lasing intensity of the dye-doped negative LC laser can be tuned from low to high if the NPs concentration is increased. The tunability of the laser is attributable to the clusters-sensitive feature in effective refractive index of the negative LCs. Such a tunable negative liquid crystal laser can be used in the fabrication of new optical sources, optical communication, and liquid crystal laser displays.

GENERAL

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Discord and entanglement in non-Markovian environments at finite temperatures Hong-Mei Zou(邹红梅), Mao-Fa Fang(方卯发) Chin. Phys. B, 2016, 25 (9):  090302.  DOI: 10.1088/1674-1056/25/9/090302 Abstract ( 749 )   HTML   PDF (371KB) ( 352 )   The dynamic evolutions of the discord and entanglement of two atoms immersed in two independent Lorentzian reservoirs at zero and finite temperatures have been investigated by using the time-convolutionless master-equation method. Our results show that, nonzero temperature can induce the entanglement sudden death and accelerate the decays of discord and entanglement. The discord and the entanglement have different robustness for different initial states and their robustness may change under certain conditions. When both the non-Markovian effect and detuning are present simultaneously, due to the memory and feedback effect of non-Markovian reservoirs, the discord and entanglement can be effectively protected even at nonzero temperature by increasing the non-Markovian effect and the detuning.

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Generating periodic interference in Bose-Einstein condensates Shen-Tong Ji(冀慎统), Yuan-Sheng Wang(王元生), Yue-E Luo(罗月娥), Xue-Shen Liu(刘学深) Chin. Phys. B, 2016, 25 (9):  090303.  DOI: 10.1088/1674-1056/25/9/090303 Abstract ( 632 )   HTML   PDF (329KB) ( 344 )   The interference between two condensates with repulsive interaction is investigated numerically by solving the one-dimensional time-dependent Gross-Pitaevskii equation. The periodic interference pattern forms in two condensates, which are prepared in a double-well potential consisting of two truncated harmonic wells centered at different positions. Dark solitons are observed when two condensates overlap. Due to the existence of atom-atom interactions, atoms are transferred among the ground state and the excited states, which coincides with the condensate energy change.

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The ground states and pseudospin textures of rotating two-component Bose-Einstein condensates trapped in harmonic plus quartic potential Yan Liu(刘燕), Su-Ying Zhang(张素英) Chin. Phys. B, 2016, 25 (9):  090304.  DOI: 10.1088/1674-1056/25/9/090304 Abstract ( 820 )   HTML   PDF (3860KB) ( 509 )   The ground states of two-component miscible Bose-Einstein condensates (BECs) confined in a rotating annular trap are obtained by using the Thomas-Fermi (TF) approximation method. The ground state density distribution of the condensates experiences a transition from a disc shape to an annulus shape either when the angular frequency increases and the width and the center height of the trap are fixed, or when the width and the center height of the trap increase and the angular frequency is fixed. Meantime the numerical solutions of the ground states of the trapped two-component miscible BECs with the same condition are obtained by using imaginary-time propagation method. They are in good agreement with the solutions obtained by the TF approximation method. The ground states of the trapped two-component immiscible BECs are also given by using the imaginary-time propagation method. Furthermore, by introducing a normalized complex-valued spinor, three kinds of pseudospin textures of the BECs, i.e., giant skyrmion, coaxial double-annulus skyrmion, and coaxial three-annulus skyrmion, are found.

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Current and efficiency optimization under oscillating forces in entropic barriers Ferhat Nutku, Ekrem Aydiner Chin. Phys. B, 2016, 25 (9):  090501.  DOI: 10.1088/1674-1056/25/9/090501 Abstract ( 756 )   HTML   PDF (3824KB) ( 375 )   The transport of externally overdriven particles confined in entropic barriers is investigated under various types of oscillating and temporal forces. Temperature, load, and amplitude dependence of the particle current and energy conversion efficiency are investigated in three dimensions. For oscillating forces, the optimized temperature-load, amplitude-temperature, and amplitude-load intervals are determined when fixing the amplitude, load, and temperature, respectively. By using three-dimensional plots rather than two-dimensional ones, it is clearly shown that oscillating forces provide more efficiency compared with a temporal one in specified optimized parameter regions. Furthermore, the dependency of efficiency to the angle between the unbiased driving force and a constant force is investigated and an asymmetric angular dependence is found for all types of forces. Finally, it is shown that oscillating forces with a high amplitude and under a moderate load lead to higher efficiencies than a temporal force at both low and high temperatures for the entire range of contact angle.

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A flux-controlled model of meminductor and its application in chaotic oscillator Guang-Yi Wang(王光义), Pei-Pei Jin(靳培培), Xiao-Wei Wang(王晓炜), Yi-Ran Shen(沈怡然), Fang Yuan(袁方), Xiao-Yuan Wang(王晓媛) Chin. Phys. B, 2016, 25 (9):  090502.  DOI: 10.1088/1674-1056/25/9/090502 Abstract ( 716 )   HTML   PDF (10402KB) ( 999 )   A meminductor is a new type of memory device developed from the memristor. We present a mathematical model of a flux-controlled meminductor and its equivalent circuit model for exploring the properties of the meminductor in a nonlinear circuit. We explore the response characteristics of the meminductor under the exciting signals of sinusoidal, square, and triangular waves by using theoretical analysis and experimental tests, and design a meminductor-based oscillator based on the model. Theoretical analysis and experiments show that the meminductor-based oscillator possesses complex bifurcation behaviors and can generate periodic and chaotic oscillations. A special phenomenon called the co-existent oscillation that can generate multiple oscillations (such as chaotic, periodic oscillations as well as stable equilibrium) with the same parameters and different initial conditions occurs. We also design an analog circuit to realize the meminductor-based oscillator, and the circuit experiment results are in accordance with the theory analysis.

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Inverse full state hybrid projective synchronizationfor chaotic maps with different dimensions Adel Ouannas, Giuseppe Grassi Chin. Phys. B, 2016, 25 (9):  090503.  DOI: 10.1088/1674-1056/25/9/090503 Abstract ( 626 )   HTML   PDF (1172KB) ( 332 )   A new synchronization scheme for chaotic (hyperchaotic) maps with different dimensions is presented. Specifically, given a drive system map with dimension n and a response system with dimension m, the proposed approach enables each drive system state to be synchronized with a linear response combination of the response system states. The method, based on the Lyapunov stability theory and the pole placement technique, presents some useful features: (i) it enables synchronization to be achieved for both cases of n < m and n > m; (ii) it is rigorous, being based on theorems; (iii) it can be readily applied to any chaotic (hyperchaotic) maps defined to date. Finally, the capability of the approach is illustrated by synchronization examples between the two-dimensional Hénon map (as the drive system) and the three-dimensional hyperchaotic Wang map (as the response system), and the three-dimensional Hénon-like map (as the drive system) and the two-dimensional Lorenz discrete-time system (as the response system).

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Period-control and chaos-anti-control of a semiconductor laser using the twisted fiber Sen-Lin Yan(颜森林) Chin. Phys. B, 2016, 25 (9):  090504.  DOI: 10.1088/1674-1056/25/9/090504 Abstract ( 784 )   HTML   PDF (1428KB) ( 399 )   A novel semiconductor laser system is presented based on a twisted fiber. To study the period-control and chaos-anti-control of the laser system, we design a type of optic path as a control setup using the combination of the twisted fiber and the polarization controller while we present a physical dynamics model of the delayed dual-feedback laser containing the twisted fiber effect. We give an analysis of the effect of the twisted fiber on the laser. We use the effects of the delayed phase and the rotation angle of the twisted fiber and the characteristics of the system to achieve control of the laser. The laser is deduced to a stable state, a double-periodic state, a period-6 state, a period-8 state, a period-9 state, a multi-period state, beat phenomenon, and so on. The periodic laser can be anti-controlled to chaos. Some chaos-anti-control area is found. The laser system is very useful for the study of chaos-control of the laser setup and the applications of some physics effects.

SPECIAL TOPIC—Physical research in liquid crystal

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Influence of amphotericin B on liquid crystal state of the Cholesterol/Dipalmitoylphosphatidylcholine monolayer in the presence of different metal cations Juan Wang(王娟), Rui-Xin Shi(史瑞新), Run-Guang Sun(孙润广), Chang-Chun Hao(郝长春), Jun-Hua Li(李俊花), Xiao-Long Lu(逯晓龙) Chin. Phys. B, 2016, 25 (9):  090505.  DOI: 10.1088/1674-1056/25/9/090505 Abstract ( 619 )   HTML   PDF (1145KB) ( 507 )   Amphotericin B is a very effective antifungal drug, but it has an adverse reaction to the membrane of mammals' cells. The interaction between AmB and cholesterol (Chol) causes the formation of pores on the membrane to destroy its integrity. In particular, AmB has a significant effect on the permeability of membrane for K+ ions. It has been reported that Na+ ions and Ca2+ ions may have some influence on the interaction between amphotericin B and lipid molecules. In this work, the effects of these metal cations on the physical state and intermolecular interaction of the Cholesterol/ Dipalmitoylphosphatidylcholine (Chol/DPPC) monolayer with and without AmB have been investigated. The addition of AmB induces the change of physical state of the lipid monolayer from liquid-gel phase to liquid phase. Different metal cations could influence the phase transition of the AmB-lipid monolayer. The K+ ions and Ca2+ ions make the obvious phase transition disappear. However, the presence of Na+ ions has little influence on the phase transition of the AmB-lipid monolayer. The addition of AmB and the presence of different metal cations weaken the attractive force on the monolayers. After addition of AmB, the force between the molecules is the strongest in the environment of K+ ions, thus is the weakest in the environment of Ca2+ ions, which may be due to the distribution of these metal cations inside and outside of cells. A large number of K+ ions distribute inside of the cells, thus most of Na+ and Ca2+ ions exist out of the cells. Hence, it may be possible that when AmB molecules are out of the cells, the reaction between the drug and lipid molecules is weaker than that inside the cells. These results may have a great reference value for further studying the toxicity mechanism of AmB and the influence of metal cations on the membrane.

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Behavior of lysozyme adsorbed onto biological liquid crystal lipid monolayer at the air/water interface Xiaolong Lu(逯晓龙), Ruixin Shi(史瑞新), Changchun Hao(郝长春), Huan Chen(陈欢), Lei Zhang(张蕾), Junhua Li(李俊花), Guoqing Xu(徐国庆), Runguang Sun(孙润广) Chin. Phys. B, 2016, 25 (9):  090506.  DOI: 10.1088/1674-1056/25/9/090506 Abstract ( 834 )   HTML   PDF (1303KB) ( 386 )   The interaction between proteins and lipids is one of the basic problems of modern biochemistry and biophysics. The purpose of this study is to compare the penetration degree of lysozyme into 1,2-diapalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethano-lamine (DPPE) by analyzing the data of surface pressure-area (π-A) isotherms and surface pressure-time (π-T) curves. Lysozyme can penetrate into both DPPC and DPPE monolayers because of the increase of surface pressure at an initial pressure of 15 mN/m. However, the changes of DPPE are larger than DPPC, indicating stronger interaction of lysozyme with DPPE than DPPC. The reason may be due to the different head groups and phase state of DPPC and DPPE monolayers at the surface pressure of 15 mN/m. Atomic force microscopy reveals that lysozyme was absorbed by DPPC and DPPE monolayers, which leads to self-aggregation and self-assembly, forming irregular multimers and conical multimeric. Through analysis, we think that the process of polymer formation is similar to the aggregation mechanism of amyloid fibers.

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Analysis of the induction of the myelin basic protein binding to the plasma membrane phospholipid monolayer Lei Zhang(张蕾), Changchun Hao(郝长春), Ying Feng(冯盈), Feng Gao(高峰), Xiaolong Lu(逯晓龙), Junhua Li(李俊花), Runguang Sun(孙润广) Chin. Phys. B, 2016, 25 (9):  090507.  DOI: 10.1088/1674-1056/25/9/090507 Abstract ( 681 )   HTML   PDF (1418KB) ( 444 )   Myelin basic protein (MBP) is an essential structure involved in the generation of central nervous system (CNS) myelin. Myelin shape has been described as liquid crystal structure of biological membrane. The interactions of MBP with monolayers of different lipid compositions are responsible for the multi-lamellar structure and stability of myelin. In this paper, we have designed MBP-incorporated model lipid monolayers and studied the phase behavior of MBP adsorbed on the plasma membrane at the air/water interface by thermodynamic method and atomic force microscopy (AFM). By analyzing the pressure-area (π-A) and pressure-time (π-T) isotherms, univariate linear regression equation was obtained. In addition, the elastic modulus, surface pressure increase, maximal insertion pressure, and synergy factor of monolayers were detected. These parameters can be used to modulate the monolayers binding of protein, and the results show that MBP has the strongest affinity for 1,2-dipalmitoyl-sn-glycero-3- phosphoserine (DPPS) monolayer, followed by DPPC/DPPS mixed and 1,2-dipalmitoyl-sn-glycero-3-phospho-choline (DPPC) monolayers via electrostatic and hydrophobic interactions. AFM images of DPPS and DPPC/DPPS mixed monolayers in the presence of MBP (5 nM) show a phase separation texture at the surface pressure of 20 mN/m and the incorporation of MBP put into the DPPC monolayers has exerted a significant effect on the domain structure. MBP is not an integral membrane protein but, due to its positive charge, interacts with the lipid head groups and stabilizes the membranes. The interaction between MBP and phospholipid membrane to determine the nervous system of the disease has a good biophysical significance and medical value.

GENERAL

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Fiber-based multiple-access frequency synchronization via 1f-2f dissemination Xi Zhu(朱玺), Bo Wang(王波), Chao Gao(高超), Li-Jun Wang(王力军) Chin. Phys. B, 2016, 25 (9):  090601.  DOI: 10.1088/1674-1056/25/9/090601 Abstract ( 749 )   HTML   PDF (327KB) ( 331 )   Considering the reference frequency dissemination requirements of the Square Kilometre Array telescope (SKA) project, on the basis of the 1f-2f precision frequency synchronization scheme, we propose and demonstrate a fiber-based multiple-access frequency synchronization scheme. The dissemination reference frequency can be recovered at arbitrary nodes along the entire fiber link. It can be applied to antennas close proximity to the SKA central station, and will lead to a better SKA frequency synchronization network. As a performance test, we recover the disseminated 100-MHz reference frequency at an arbitrary node chosen as being 5 km away from the transmitting site. Relative frequency stabilities of 2.0×10-14/s and 1.6×10-16/104s are obtained. We also experimentally verify the feasibility of a frequency dissemination link with three access points.

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Ultrafast optical beam deflection in a pump probe configuration Lingliang Liang(梁玲亮), Jinshou Tian (田进寿), Tao Wang(汪韬), Shengli Wu(吴胜利), Fuli Li(李福利), Junfeng Wang(王俊锋), Guilong Gao(高贵龙) Chin. Phys. B, 2016, 25 (9):  090602.  DOI: 10.1088/1674-1056/25/9/090602 Abstract ( 786 )   HTML   PDF (2991KB) ( 369 )   Propagation of a signal beam in an AlGaAs/GaAs waveguide multiple-prism light deflector is theoretically investigated by solving the scalar Helmholtz equation to obtain the dependences of the temporal and spatial resolvable characteristics of the ultrafast deflector on the material dispersion of GaAs including group velocity dispersion and angular dispersion, interface reflection, and interface scattering of multiple-prism deflector. Furthermore, we experimentally confirm that, in this ultrafast beam deflection device, the deflecting angle of the signal light beam is linear with the pump fluence and the temporal resolution of the ultrafast deflection is 10 ps. Our results show that the improvement of the temporal and spatial resolvable performances is possible by properly choosing the structural parameters and enhancing the quality of the device.

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Calibration chain design based on integrating sphere transfer radiometer for SI-traceable on-orbit spectral radiometric calibration and its uncertainty analysis Wei-Ning Zhao(赵维宁), Wei Fang(方伟), Li-Wei Sun(孙立微), Li-Hong Cui(崔立红), Yu-Peng Wang(王玉鹏) Chin. Phys. B, 2016, 25 (9):  090701.  DOI: 10.1088/1674-1056/25/9/090701 Abstract ( 727 )   HTML   PDF (921KB) ( 271 )   In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors, a transfer chain consisting of a fiber coupling monochromator (FBM) and an integrating sphere transfer radiometer (ISTR) was designed in this paper. Depending on the Sun, this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band (RSB) covering 300-2500 nm with a spectral bandwidth of 0.5-6 nm. It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard. This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor, including the weak spectral signal measurement with uncertainty of 0.28%. According to the peculiar design and comprehensive uncertainty analysis, it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%. The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality.

SPECIAL TOPIC—Physical research in liquid crystal

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High signal-to-noise ratio sensing with Shack-Hartmann wavefront sensor based on auto gain control of electron multiplying CCD Zhao-Yi Zhu(朱召义), Da-Yu Li(李大禹), Li-Fa Hu(胡立发), Quan-Quan Mu(穆全全), Cheng-Liang Yang(杨程亮), Zhao-Liang Cao(曹召良), Li Xuan(宣丽) Chin. Phys. B, 2016, 25 (9):  090702.  DOI: 10.1088/1674-1056/25/9/090702 Abstract ( 983 )   HTML   PDF (1745KB) ( 288 )   High signal-to-noise ratio can be achieved with the electron multiplying charge-coupled-device (EMCCD) applied in the Shack-Hartmann wavefront sensor (S-H WFS) in adaptive optics (AO). However, when the brightness of the target changes in a large scale, the fixed electron multiplying (EM) gain will not be suited to the sensing limitation. Therefore an auto-gain-control method based on the brightness of light-spots array in S-H WFS is proposed in this paper. The control value is the average of the maximum signals of every light spot in an array, which has been demonstrated to be kept stable even under the influence of some noise and turbulence, and sensitive enough to the change of target brightness. A goal value is needed in the control process and it is predetermined based on the characters of EMCCD. Simulations and experiments have demonstrated that this auto-gain-control method is valid and robust, the sensing SNR reaches the maximum for the corresponding signal level, and especially is greatly improved for those dim targets from 6 to 4 magnitude in the visual band.

ATOMIC AND MOLECULAR PHYSICS

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Magic wavelengths for the 7s1/2-6d3/2,5/2 transitions in Ra+ Xiao-Mei Wu(吴晓梅), Cheng-Bin Li(李承斌), Yong-Bo Tang(唐永波), Ting-Yun Shi(史庭云) Chin. Phys. B, 2016, 25 (9):  093101.  DOI: 10.1088/1674-1056/25/9/093101 Abstract ( 907 )   HTML   PDF (643KB) ( 446 )   The dynamic polarizabilities of the 7s and 6d states of Ra+ are calculated using a relativistic core polarization potential method. The magic wavelengths of the 7s1/2-6d3/2,5/2 transitions are identified. Comparing to the common radio-frequency (RF) ion traps, using the laser field at the magic wavelength to trap the ion could suppress the frequency uncertainty caused by the micromotion of the ion, and would not affect the transition frequency measurements. The heating rates of the ion and the powers of the laser for the ion trapping are estimated, which would benefit the possible precision measurements based on all-optical trapped Ra+.

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First principle calculations of thermodynamic properties of pure graphene sheet and graphene sheets with Si, Ge, Fe, and Co impurities A Kheyri, Z Nourbakhsh Chin. Phys. B, 2016, 25 (9):  093102.  DOI: 10.1088/1674-1056/25/9/093102 Abstract ( 623 )   HTML   PDF (1541KB) ( 505 )   The thermal properties of pure graphene and graphene-impurity (impurity = Fe, Co, Si, and Ge) sheets have been investigated at various pressures (0-7 GPa) and temperatures (0-900 K). Some basic thermodynamic quantities such as bulk modulus, coefficient of volume thermal expansion, heat capacities at constant pressure and constant volume of these sheets as a function of temperature and pressure are discussed. Furthermore, the effect of the impurity density and tensile strain on the thermodynamic properties of these sheets are investigated. All of these calculations are performed based on the density functional theory and full quasi harmonic approximation.

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Photoelectron angular distributions of H ionization in low energy regime: Comparison between different potentials Shu-Na Song(宋舒娜), Hao Liang(梁昊), Liang-You Peng(彭良友), Hong-Bing Jiang(蒋红兵) Chin. Phys. B, 2016, 25 (9):  093201.  DOI: 10.1088/1674-1056/25/9/093201 Abstract ( 753 )   HTML   PDF (2560KB) ( 434 )   We theoretically investigate the low energy part of the photoelectron spectra in the tunneling ionization regime by numerically solving the time-dependent Schrdinger equation for different atomic potentials at various wavelengths. We find that the shift of the first above-threshold ionization (ATI) peak is closely related to the interferences between electron wave packets, which are controlled by the laser field and largely independent of the potential. By gradually changing the short-range potential to the long-range Coulomb potential, we show that the long-range potential's effect is mainly to focus the electrons along the laser's polarization and to generate the spider structure by enhancing the rescattering process with the parent ion. In addition, we find that the intermediate transitions and the Rydberg states have important influences on the number and the shape of the lobes near the threshold.

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Controlling the contributions to high-order harmonic generation from different nuclei of N2 with an orthogonally polarizedtwo-color laser field Hui Du(杜慧), Xue-Fei Pan(潘雪飞), Hai-Feng Liu(刘海凤), Hong-Dan Zhang(张宏丹), Jun Zhang(张军), Jing Guo(郭静), Xue-Shen Liu(刘学深) Chin. Phys. B, 2016, 25 (9):  093202.  DOI: 10.1088/1674-1056/25/9/093202 Abstract ( 864 )   HTML   PDF (1779KB) ( 445 )   The generation of high-order harmonic and the attosecond pulse of the N2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model. We show that the control of contributions to high-order harmonic generation (HHG) from different nuclei is realized by properly selecting the relative phase. When the relative phase is chosen to be φ=0.4π, the contribution to HHG from one nucleus is much more than that from another. Interference between two nuclei can be suppressed greatly; a supercontinuum spectrum of HHG appears from 40 eV to 125 eV. The underlying physical mechanism is well explained by the time-frequency analysis and the semi-classical three-step model with a finite initial transverse velocity. By superposing several orders of harmonics, an isolated attosecond pulse with a duration of 80 as can be generated.

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Branching ratio and angular distribution of ejected electrons from Eu 4f76p1/2nd auto-ionizing states Xiao-Rui Wu(武晓瑞), Li Shen(沈礼), Kai Zhang(张开), Chang-Jian Dai(戴长建), Yu-Na Yang(杨玉娜) Chin. Phys. B, 2016, 25 (9):  093203.  DOI: 10.1088/1674-1056/25/9/093203 Abstract ( 662 )   HTML   PDF (1176KB) ( 247 )   The branching ratios of ions and the angular distributions of electrons ejected from the Eu 4f76p1/2nd auto-ionizing states are investigated with the velocity-map-imaging technique. To populate the above auto-ionizing states, the relevant bound Rydberg states have to be detected first. Two new bound Rydberg states are identified in the region between 41150 cm-1 and 44580 cm-1, from which auto-ionization spectra of the Eu 4f76p1/2nd states are observed with isolated core excitation method. With all preparations above, the branching ratios from the above auto-ionizing states to different final ionic states and the angular distributions of electrons ejected from these processes are measured systematically. Energy dependence of branching ratios and anisotropy parameters within the auto-ionization spectra are carefully analyzed, followed by a qualitative interpretation.

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Intrinsic product polarization and branch ratio in theS(1D, 3P)+HD reaction on three electronic states Lin Li(李琳), Shunle Dong(董顺乐) Chin. Phys. B, 2016, 25 (9):  093401.  DOI: 10.1088/1674-1056/25/9/093401 Abstract ( 694 )   HTML   PDF (2480KB) ( 364 )   The intrinsic product polarization and intramolecular isotope effect of the S(1D, 3P)+HD reaction have been investigated on both the lowest singlet state (1A') and the triplet state (3A' and 3A'') potential energy surfaces by using quasi-classical trajectory and quantum mechanical methods. The calculations indicate that intramolecular isotope effects are different on the three electronic states. The stereodynamics study shows that the P(θr) distributions, P(φr) distributions, and polarization-dependent differential cross sections (PDDCSs) (00) are sensitive to mass factor and the product angular momentum vectors are not only aligned but also oriented.

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Helix-like structure formation of a semi-flexible chain confined in a cylinder channel Xiaohui Wen(温晓会), Tieyu Sun(孙铁昱), Wei-Bing Zhang(张卫兵), Chi-Hang Lam(林志恒), Linxi Zhang(章林溪), Huaping Zang(臧华平) Chin. Phys. B, 2016, 25 (9):  093601.  DOI: 10.1088/1674-1056/25/9/093601 Abstract ( 701 )   HTML   PDF (2284KB) ( 462 )   Molecular dynamics method is used to study the conformation behavior of a semi-flexible polymer chain confined in a cylinder channel. A novel helix-like structure is found to form during the simulation. Moreover, the detailed characteristic parameters and formation probability of these helix-like structures under moderate conditions are investigated. We find that the structure is not a perfect helix, but a bundle of elliptical turns. In addition, we conduct a statistical analysis for the chain monomer distribution along the radial direction. This research contributes to our understanding of the microscopic conformation of polymer chains in confined environments filled with a solvent.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Ultra-thin single-layer transparent geometrical phase gradient metasurface and its application to high-gain circularly-polarized lens antenna Tang-Jing Li(李唐景), Jian-Gang Liang(梁建刚), Hai-Peng Li(李海鹏), Ya-Qiao Liu(刘亚峤) Chin. Phys. B, 2016, 25 (9):  094101.  DOI: 10.1088/1674-1056/25/9/094101 Abstract ( 702 )   HTML   PDF (2241KB) ( 670 )   A new method to design an ultra-thin high-gain circularly-polarized antenna system with high efficiency is proposed based on the geometrical phase gradient metasurface (GPGM). With an accuracy control of the transmission phase and also the high transmission amplitude, the GPGM is capable of manipulating an electromagnetic wave arbitrarily. A focusing transmission lens working at Ku band is well optimized with the F/D of 0.32. A good focusing effect is demonstrated clearly by theoretical calculation and electromagnetic simulation. For further application, an ultra-thin single-layer transmissive lens antenna based on the proposed focusing metasurface operating at 13 GHz is implemented and launched by an original patch antenna from the perspective of high integration, simple structure, and low cost. Numerical and experimental results coincide well, indicating the advantages of the antenna system, such as a high gain of 17.6 dB, the axis ratio better than 2 dB, a high aperture efficiency of 41%, and also a simple fabrication process based on the convenient print circuit board technology. The good performance of the proposed antenna indicates promising applications in portable communication systems.

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Model of bidirectional reflectance distribution function for metallic materials Kai Wang(王凯), Jing-Ping Zhu(朱京平), Hong Liu(刘宏), Xun Hou(侯洵) Chin. Phys. B, 2016, 25 (9):  094201.  DOI: 10.1088/1674-1056/25/9/094201 Abstract ( 769 )   HTML   PDF (1812KB) ( 444 )   Based on the three-component assumption that the reflection is divided into specular reflection, directional diffuse reflection, and ideal diffuse reflection, a bidirectional reflectance distribution function (BRDF) model of metallic materials is presented. Compared with the two-component assumption that the reflection is composed of specular reflection and diffuse reflection, the three-component assumption divides the diffuse reflection into directional diffuse and ideal diffuse reflection. This model effectively resolves the problem that constant diffuse reflection leads to considerable error for metallic materials. Simulation and measurement results validate that this three-component BRDF model can improve the modeling accuracy significantly and describe the reflection properties in the hemisphere space precisely for the metallic materials.

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Controllable all-optical stochastic logic gates and their delay storages based on the cascaded VCSELs with optical-injection Dongzhou Zhong(钟东洲), Wei Luo(罗伟), Geliang Xu(许葛亮) Chin. Phys. B, 2016, 25 (9):  094202.  DOI: 10.1088/1674-1056/25/9/094202 Abstract ( 730 )   HTML   PDF (2204KB) ( 360 )   Using the dynamical properties of the polarization bistability that depends on the detuning of the injected light, we propose a novel approach to implement reliable all-optical stochastic logic gates in the cascaded vertical cavity surface emitting lasers (VCSELs) with optical-injection. Here, two logic inputs are encoded in the detuning of the injected light from a tunable CW laser. The logic outputs are decoded from the two orthogonal polarization lights emitted from the optically injected VCSELs. For the same logic inputs, under electro-optic modulation, we perform various digital signal processing (NOT, AND, NAND, XOR, XNOR, OR, NOR) in the all-optical domain by controlling the logic operation of the applied electric field. Also we explore their delay storages by using the mechanism of the generalized chaotic synchronization. To quantify the reliabilities of these logic gates, we further demonstrate their success probabilities.

TOPICAL REVIEW—Physical research in liquid crystal

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Latest development of display technologies Hong-Yue Gao(高洪跃), Qiu-Xiang Yao(姚秋香), Pan Liu(刘攀), Zhi-Qiang Zheng(郑志强), Ji-Cheng Liu(刘吉成), Hua-Dong Zheng(郑华东), Chao Zeng(曾超), Ying-Jie Yu(于瀛洁), Tao Sun(孙涛), Zhen-Xiang Zeng(曾震湘) Chin. Phys. B, 2016, 25 (9):  094203.  DOI: 10.1088/1674-1056/25/9/094203 Abstract ( 860 )   HTML   PDF (4928KB) ( 1580 )   In this review we will focus on recent progress in the field of two-dimensional (2D) and three-dimensional (3D) display technologies. We present the current display materials and their applications, including organic light-emitting diodes (OLEDs), flexible OLEDs quantum dot light emitting diodes (QLEDs), active-matrix organic light emitting diodes (AMOLEDs), electronic paper (E-paper), curved displays, stereoscopic 3D displays, volumetric 3D displays, light field 3D displays, and holographic 3D displays. Conventional 2D display devices, such as liquid crystal devices (LCDs) often result in ambiguity in high-dimensional data images because of lacking true depth information. This review thus provides a detailed description of 3D display technologies.

SPECIAL TOPIC—Physical research in liquid crystal

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Phase-only stereoscopic hologram calculation based on Gerchberg-Saxton iterative algorithm Xinyi Xia(夏心怡), Jun Xia(夏军) Chin. Phys. B, 2016, 25 (9):  094204.  DOI: 10.1088/1674-1056/25/9/094204 Abstract ( 1060 )   HTML   PDF (1165KB) ( 483 )   A phase-only computer-generated holography (CGH) calculation method for stereoscopic holography is proposed in this paper. The two-dimensional (2D) perspective projection views of the three-dimensional (3D) object are generated by the computer graphics rendering techniques. Based on these views, a phase-only hologram is calculated by using the Gerchberg-Saxton (GS) iterative algorithm. Comparing with the non-iterative algorithm in the conventional stereoscopic holography, the proposed method improves the holographic image quality, especially for the phase-only hologram encoded from the complex distribution. Both simulation and optical experiment results demonstrate that our proposed method can give higher quality reconstruction comparing with the traditional method.

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Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films Hong-Yue Gao(高洪跃), Pan Liu(刘攀), Chao Zeng(曾超), Qiu-Xiang Yao(姚秋香), Zhiqiang Zheng(郑志强), Jicheng Liu(刘吉成), Huadong Zheng(郑华东), Ying-Jie Yu(于瀛洁), Zhen-Xiang Zeng(曾震湘), Tao Sun(孙涛) Chin. Phys. B, 2016, 25 (9):  094205.  DOI: 10.1088/1674-1056/25/9/094205 Abstract ( 638 )   HTML   PDF (1732KB) ( 408 )   We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Coherent population trapping magnetometer by differential detecting magneto-optic rotation effect Fan Zhang(张樊), Yuan Tian(田原), Yi Zhang(张奕), Si-Hong Gu(顾思洪) Chin. Phys. B, 2016, 25 (9):  094206.  DOI: 10.1088/1674-1056/25/9/094206 Abstract ( 784 )   HTML   PDF (700KB) ( 527 )   A pocket coherent population trapping (CPT) atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated. Using the differential detecting magneto-optic rotation effect, a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained. The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order, and the ability to detect weak magnetic fields is extended one-fold. Therefore, the proposed scheme is suited to realize a pocket-size CPT magnetometer.

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Generation of 15 W femtosecond laser pulse from a Kerr-lens mode-locked Yb: YAG thin-disk oscillator Yingnan Peng(彭英楠), Jinwei Zhang(张金伟), Zhaohua Wang(王兆华), Jiangfeng Zhu(朱江峰), Dehua Li(李德华), Zhiyi Wei(魏志义) Chin. Phys. B, 2016, 25 (9):  094207.  DOI: 10.1088/1674-1056/25/9/094207 Abstract ( 685 )   HTML   PDF (584KB) ( 341 )   We demonstrated a robust power-scalable Kerr-lens mode-locked (KLM) operation based on a Yb:YAG thin-disk oscillator. 15-W, 272-fs pulses were realized at a repetition rate of 86.7 MHz with an additional Kerr medium and a 2.5 mm hard aperture in the cavity. 247-fs pulses with an average power of 11 W could also be obtained by using a 2.4 mm hard aperture. Based on this shorter pulse, high efficient second-harmonic generation (SHG) was performed with a 1.7-mm-long LiB3O5 (LBO) crystal. The SHG laser power was up to 5 W with the power fluctuation RMS of 1% measured over one hour.

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High-energy femtosecond Yb-doped all-fiber monolithic chirped-pulse amplifier at repetition rate of 1 MHz Zhi-Guo Lv(吕志国), Hao Teng(滕浩), Li-Na Wang(王立娜), Jun-Li Wang(王军利), Zhi-Yi Wei(魏志义) Chin. Phys. B, 2016, 25 (9):  094208.  DOI: 10.1088/1674-1056/25/9/094208 Abstract ( 829 )   HTML   PDF (624KB) ( 359 )   A high-energy femtosecond all ytterbium fiber amplifier based on a chirped-pulse amplification (CPA) technique at a repetition rate of 1 MHz seeded by a dispersion-management mode-locked picosecond broadband oscillator is studied. We find that the compressed pulse duration is dependent on the amplified energy, the pulse duration of 804 fs corresponds to the maximum amplified energy of 10.5 μJ, while the shortest pulse duration of 424 fs corresponds to the amplified energy of 6.75 μJ. The measured energy fluctuation is approximately 0.46% root mean square (RMS) over 2 h. The low-cost femtosecond fiber laser source with super-stability will be widely used in industrial micromachines, medical therapy, and scientific studies.

SPECIAL TOPIC—Physical research in liquid crystal

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Random lasing in dye-doped polymer dispersed liquid crystal film Rina Wu(乌日娜), Rui-xin Shi(史瑞新), Xiaojiao Wu(邬小娇), Jie Wu(吴杰), Qin Dai(岱钦) Chin. Phys. B, 2016, 25 (9):  094209.  DOI: 10.1088/1674-1056/25/9/094209 Abstract ( 715 )   HTML   PDF (1192KB) ( 844 )   A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Spectroscopy system based on a single quantum cascade laser for simultaneous detection of CO and CO2 Min Wei(魏敏), Qing-Hao Ye(叶擎昊), Rui-Feng Kan(阚瑞峰), Bing Chen(陈兵), Chen-Guang Yang(杨晨光), Zhen-Yu Xu(许振宇), Xiang Chen(陈祥), Jun Ruan(阮俊), Xue-Li Fan(范雪丽), Wei Wang(王薇), Mai Hu(胡迈), Jian-Guo Liu(刘建国) Chin. Phys. B, 2016, 25 (9):  094210.  DOI: 10.1088/1674-1056/25/9/094210 Abstract ( 796 )   HTML   PDF (632KB) ( 435 )   A quantum cascade laser (QCL) based system for simultaneous detection of CO and CO2 is developed. The QCL can scan over two neighboring CO (2055.40 cm-1) and CO2 (2055.16 cm-1) lines with a single current scan. The wavelength modulation spectroscopy (f = 20 kHz) is utilized to enhance the signal-to-noise ratio. A white cell with an effective optical path length of 74 m is used. The calibration of the sensor is performed and minimum detection limits of 1.3 ppb (1×10-9) for CO and 0.44 ppm (1×10-6) for CO2 are achieved.

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Correction of walk-off-induced wavefront distortion for continuous-wave laser Hongxin Zou(邹宏新), Guozhu Chen(陈国柱), Yue Wu(伍越), Yong Shen(沈咏), Qu Liu(刘曲) Chin. Phys. B, 2016, 25 (9):  094211.  DOI: 10.1088/1674-1056/25/9/094211 Abstract ( 660 )   HTML   PDF (910KB) ( 375 )   We theoretically and experimentally investigate the wave front distortion in critically phase-matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM00 mode efficiently. Theoretically, we simulate the correction effect of 266-nm laser generated with SHG. The experiment results accord well with the theoretical simulation and an above 80% TEM00 component is obtained for 266-nm continuous-wave laser with a 4.8°-walk-off angle in beta barium borate (BBO) crystal.

TOPICAL REVIEW—Physical research in liquid crystal

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Kerr effect and Kerr constant enhancement in vertically aligned deformed helix ferroelectric liquid crystals Liangyu Shi, Abhishek Kumar Srivastava, Vladimir G Chigrinov, Hoi-Sing Kwok Chin. Phys. B, 2016, 25 (9):  094212.  DOI: 10.1088/1674-1056/25/9/094212 Abstract ( 730 )   HTML   PDF (1153KB) ( 626 )   In this article, we review recently achieved Kerr effect progress in novel liquid crystal (LC) material: vertically aligned deformed helix ferroelectric liquid crystal (VADHFLC). With an increasing applied electric field, the induced inplane birefringence of LCs shows quadratic nonlinearity. The theoretical calculations and experimental details are illustrated. With an enhanced Kerr constant to 130 nm/V2, this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.

REVIEW

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Optimization of multi-color laser waveform for high-order harmonic generation Cheng Jin(金成), C D Lin(林启东) Chin. Phys. B, 2016, 25 (9):  094213.  DOI: 10.1088/1674-1056/25/9/094213 Abstract ( 1025 )   HTML   PDF (3320KB) ( 716 )   With the development of laser technologies, multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms. A practical optimization algorithm is needed to generate such a waveform in order to control strong-field processes. We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order harmonic generation based on genetic algorithm. By choosing different fitness criteria, we demonstrate that: (i) harmonic yields can be enhanced by 10 to 100 times, (ii) harmonic cutoff energy can be substantially extended, (iii) specific harmonic orders can be selectively enhanced, and (iv) single attosecond pulses can be efficiently generated. The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high harmonics is also discussed. The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years.

SPECIAL TOPIC—Physical research in liquid crystal

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A high precision phase reconstruction algorithm for multi-laser guide stars adaptive optics Bin He(何斌), Li-Fa Hu(胡立发), Da-Yu Li(李大禹), Huan-Yu Xu(徐焕宇), Xing-Yun Zhang(张杏云), Shao-Xin Wang(王少鑫), Yu-Kun Wang(王玉坤), Cheng-Liang Yang(杨程亮), Zhao-Liang Cao(曹召良), Quan-Quan Mu(穆全全), Xing-Hai Lu(鲁兴海), Li Xuan(宣丽) Chin. Phys. B, 2016, 25 (9):  094214.  DOI: 10.1088/1674-1056/25/9/094214 Abstract ( 872 )   HTML   PDF (529KB) ( 421 )   Adaptive optics (AO) systems are widespread and considered as an essential part of any large aperture telescope for obtaining a high resolution imaging at present. To enlarge the imaging field of view (FOV), multi-laser guide stars (LGSs) are currently being investigated and used for the large aperture optical telescopes. LGS measurement is necessary and pivotal to obtain the cumulative phase distortion along a target in the multi-LGSs AO system. We propose a high precision phase reconstruction algorithm to estimate the phase for a target with an uncertain turbulence profile based on the interpolation. By comparing with the conventional average method, the proposed method reduces the root mean square (RMS) error from 130 nm to 85 nm with a 30% reduction for narrow FOV. We confirm that such phase reconstruction algorithm is validated for both narrow field AO and wide field AO.

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Liquid crystal Fresnel lens display Xiao-Qian Wang(王骁乾), Srivastava Abhishek Kumar, Ming-Wai Alwin Tam(谈明威), Zhi-Gang Zheng(郑致刚), Dong Shen(沈冬), Chigrinov G Vladimir, Hoi-Sing Kwok(郭海成) Chin. Phys. B, 2016, 25 (9):  094215.  DOI: 10.1088/1674-1056/25/9/094215 Abstract ( 754 )   HTML   PDF (891KB) ( 429 )   A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter.

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Configuration optimization of laser guide stars and wavefront correctors for multi-conjugation adaptive optics Li Xuan(宣丽), Bin He(何斌), Li-Fa Hu(胡立发), Da-Yu Li(李大禹), Huan-Yu Xu(徐焕宇), Xing-Yun Zhang(张杏云), Shao-Xin Wang(王少鑫), Yu-Kun Wang(王玉坤), Cheng-Liang Yang(杨程亮), Zhao-Liang Cao(曹召良), Quan-Quan Mu(穆全全), Xing-Hai Lu(鲁兴海) Chin. Phys. B, 2016, 25 (9):  094216.  DOI: 10.1088/1674-1056/25/9/094216 Abstract ( 722 )   HTML   PDF (947KB) ( 287 )   Multi-conjugation adaptive optics (MCAOs) have been investigated and used in the large aperture optical telescopes for high-resolution imaging with large field of view (FOV). The atmospheric tomographic phase reconstruction and projection of three-dimensional turbulence volume onto wavefront correctors, such as deformable mirrors (DMs) or liquid crystal wavefront correctors (LCWCs), is a very important step in the data processing of an MCAO's controller. In this paper, a method according to the wavefront reconstruction performance of MCAO is presented to evaluate the optimized configuration of multi laser guide stars (LGSs) and the reasonable conjugation heights of LCWCs. Analytical formulations are derived for the different configurations and are used to generate optimized parameters for MCAO. Several examples are given to demonstrate our LGSs configuration optimization method. Compared with traditional methods, our method has minimum wavefront tomographic error, which will be helpful to get higher imaging resolution at large FOV in MCAO.

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Bichromatic coherent random lasing from dye-doped polymer stabilized blue phase liquid crystals controlled by pump light polarization Lei Wang(王雷), Meng Wang(王萌), Mingchao Yang(杨明朝), Li-Jie Shi(石丽洁), Luogen Deng(邓罗根 ), Huai Yang(杨槐) Chin. Phys. B, 2016, 25 (9):  094217.  DOI: 10.1088/1674-1056/25/9/094217 Abstract ( 605 )   HTML   PDF (1804KB) ( 398 )   In this paper, we investigate the bichromatic coherent random lasing actions from the dye-doped polymer stabilized blue phase liquid crystals. Two groups of lasing peaks, of which the full widith at half maximum is about 0.3 nm, are clearly observed. The shorter- and longer-wavelength modes are associated with the excitation of the single laser dye (DCM) monomers and dimers respectively. The experimental results show that the competition between the two groups of the lasing peaks can be controlled by varying the polarization of the pump light. When the polarization of the pump light is rotated from 0° to 90°, the intensity of the shorter-wavelength lasing peak group reduces while the intensity of the longer-wavelength lasing peak group increases. In addition, a red shift of the longer-wavelength modes is also observed and the physical mechanisms behind the red-shift phenomenon are discussed.

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Asymmetric dynamic phase holographic grating in nematic liquid crystal Chang-Yu Ren(任常愚), Hong-Xin Shi(石宏新), Yan-Bao Ai(艾延宝), Xiang-Bao Yin(尹向宝), Feng Wang(王丰), Hong-Wei Ding(丁红伟) Chin. Phys. B, 2016, 25 (9):  094218.  DOI: 10.1088/1674-1056/25/9/094218 Abstract ( 728 )   HTML   PDF (535KB) ( 301 )   A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal (NLC) was presented. An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating. The diffraction efficiency we achieved is more than 40%, exceeding the theoretical limit for symmetric profile gratings. Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC. Finally, physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented, based on the photo-refractive-like (PR-like) effect.

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Determining the imaging plane of a retinal capillary layer in adaptive optical imaging Le-Bao Yang(杨乐宝), Li-Fa Hu(胡立发), Da-Yu Li(李大禹), Zhao-Liang Cao(曹召良), Quan-Quan Mu(穆全全), Ji Ma(马骥), Li Xuan(宣丽) Chin. Phys. B, 2016, 25 (9):  094219.  DOI: 10.1088/1674-1056/25/9/094219 Abstract ( 756 )   HTML   PDF (2252KB) ( 455 )   Even in the early stage, endocrine metabolism disease may lead to micro aneurysms in retinal capillaries whose diameters are less than 10 μ. However, the fundus cameras used in clinic diagnosis can only obtain images of vessels larger than 20 μ in diameter. The human retina is a thin and multiple layer tissue, and the layer of capillaries less than 10 μ in diameter only exists in the inner nuclear layer. The layer thickness of capillaries less than 10 μ in diameter is about 40 μ and the distance range to rod&cone cell surface is tens of micrometers, which varies from person to person. Therefore, determining reasonable capillary layer (CL) position in different human eyes is very difficult. In this paper, we propose a method to determine the position of retinal CL based on the rod&cone cell layer. The public positions of CL are recognized with 15 subjects from 40 to 59 years old, and the imaging planes of CL are calculated by the effective focal length of the human eye. High resolution retinal capillary imaging results obtained from 17 subjects with a liquid crystal adaptive optics system (LCAOS) validate our method. All of the subjects' CLs have public positions from 127 μm to 147 μm from the rod&cone cell layer, which is influenced by the depth of focus.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Influence of alkali metal superoxides on structure, electronic, and optical properties of Be12O12 nanocage: Density functional theory study Ali Raoof Toosi, Hamid Reza Shamlouei, Asghar Mohammadi Hesari Chin. Phys. B, 2016, 25 (9):  094220.  DOI: 10.1088/1674-1056/25/9/094220 Abstract ( 653 )   HTML   PDF (2664KB) ( 443 )   The effect of alkali metal superoxides M3O (M = Li, Na, K) on the electronic and optical properties of a Be12O12 nanocage was studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The energy gaps (Eg) of all configurations were calculated. Generally, the adsorption of alkali metal superoxides on the Be12O12 nanocage causes a decrease of Eg. Electric dipole moment μ, polarizability α, and static first hyperpolarizability β were calculated and it was shown that the adsorption of alkali metal superoxides on Be12O12 increases its polarizability. It was found that the absorption of M3O on Be12O12 nanocluster improves its nonlinear optical properties. The highest first hyperpolarizability (β ≈ 214000 a.u.) is obtained in the K3O-Be12O12 nanocluster. The TD-DFT calculations were performed to investigate the origin of the first hyperpolarizabilities and it was shown that a higher first hyperpolarizability belongs to the structure that has a lower transition energy.

SPECIAL TOPIC—Physical research in liquid crystal

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Optical simulation of in-plane-switching blue phase liquid crystal display using the finite-difference time-domain method Hu Dou(窦虎), Hongmei Ma(马红梅), Yu-Bao Sun(孙玉宝) Chin. Phys. B, 2016, 25 (9):  094221.  DOI: 10.1088/1674-1056/25/9/094221 Abstract ( 742 )   HTML   PDF (1479KB) ( 430 )   The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display. Compared with the matrix optic methods and the refractive method, the finite-difference time-domain method, which is used to directly solve Maxwell's equations, can consider the lateral variation of the refractive index and obtain an accurate convergence effect. The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage. The finite-difference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.

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Bridging the terahertz near-field and far-field observations of liquid crystal based metamaterial absorbers Lei Wang(王磊), Shijun Ge(葛士军), Zhaoxian Chen(陈召宪), Wei Hu(胡伟), Yanqing Lu(陆延青) Chin. Phys. B, 2016, 25 (9):  094222.  DOI: 10.1088/1674-1056/25/9/094222 Abstract ( 723 )   HTML   PDF (1591KB) ( 428 )   Metamaterial-based absorbers play a significant role in applications ranging from energy harvesting and thermal emitters to sensors and imaging devices. The middle dielectric layer of conventional metamaterial absorbers has always been solid. Researchers could not detect the near field distribution in this layer or utilize it effectively. Here, we use anisotropic liquid crystal as the dielectric layer to realize electrically fast tunable terahertz metamaterial absorbers. We demonstrate strong, position-dependent terahertz near-field enhancement with sub-wavelength resolution inside the metamaterial absorber. We measure the terahertz far-field absorption as the driving voltage increases. By combining experimental results with liquid crystal simulations, we verify the near-field distribution in the middle layer indirectly and bridge the near-field and far-field observations. Our work opens new opportunities for creating high-performance, fast, tunable, terahertz metamaterial devices that can be applied in biological imaging and sensing.

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Low voltage transflective blue-phase liquid crystal display with a non-uniform etching substrate Jian Wang(王健), Jiang-Lin Mao(毛江林), Hao-Xiang Fan(范昊翔), Qiong-Hua Wang(王琼华) Chin. Phys. B, 2016, 25 (9):  094223.  DOI: 10.1088/1674-1056/25/9/094223 Abstract ( 949 )   HTML   PDF (1025KB) ( 378 )   A transflective polymer-stabilized blue-phase liquid crystal display (BP-LCD) with a non-uniform etching substrate is proposed. In-plane switching (IPS) electrodes on the bottom substrate are put on the different gaps, and the bottom substrate between the electrodes is etched into different depths in transmissive (T) and reflective (R) regions. This structure can balance the optical phase retardation in the two regions and is helpful to achieve well-matched voltag-dependent transmittance and reflectance curves. This transflective display has high optical efficiency, a wide viewing angle, and low operating voltage (approximately 6 V).

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Characteristics and generation of elastic turbulence in a three-dimensional parallel plate channel using direct numerical simulation Hong-Na Zhang(张红娜), Feng-Chen Li(李凤臣), Xiao-Bin Li(李小斌), Dong-Yang Li(李东阳), Wei-Hua Cai(蔡伟华), Bo Yu(宇波) Chin. Phys. B, 2016, 25 (9):  094701.  DOI: 10.1088/1674-1056/25/9/094701 Abstract ( 710 )   HTML   PDF (4264KB) ( 509 )   Direct numerical simulations (DNSs) of purely elastic turbulence in rectilinear shear flows in a three-dimensional (3D) parallel plate channel were carried out, by which numerical databases were established. Based on the numerical databases, the present paper analyzed the structural and statistical characteristics of the elastic turbulence including flow patterns, the wall effect on the turbulent kinetic energy spectrum, and the local relationship between the flow motion and the microstructures' behavior. Moreover, to address the underlying physical mechanism of elastic turbulence, its generation was presented in terms of the global energy budget. The results showed that the flow structures in elastic turbulence were 3D with spatial scales on the order of the geometrical characteristic length, and vortex tubes were more likely to be embedded in the regions where the polymers were strongly stretched. In addition, the patterns of microstructures' elongation behave like a filament. From the results of the turbulent kinetic energy budget, it was found that the continuous energy releasing from the polymers into the main flow was the main source of the generation and maintenance of the elastic turbulent status.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Investigation of molecular penetration depth variation with SMBI fluxes Yu-Lin Zhou(周雨林), Zhan-Hui Wang(王占辉), Min Xu(许敏), Qi Wang(王奇), Lin Nie(聂林), Hao Feng(冯灏), Wei-Guo Sun(孙卫国) Chin. Phys. B, 2016, 25 (9):  095201.  DOI: 10.1088/1674-1056/25/9/095201 Abstract ( 702 )   HTML   PDF (5884KB) ( 519 )   We study the molecular penetration depth variation with the SMBI fluxes. The molecular transport process and the penetration depth during SMBI with various injection velocities and densities are simulated and compared. It is found that the penetration depth of molecules strongly depends on the radial convective transport of SMBI and it increases with the increase of the injection velocity. The penetration depth does not vary much once the SMBI injection density is larger than a critical value due to the dramatic increase of the dissociation rate on the fueling path. An effective way to improve the SMBI penetration depth has been predicted, which is SMBI with a large radial injection velocity and a lower molecule injection density than the critical density.

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Formation and dissociation of dust molecules in dusty plasma Jia Yan(闫佳), Fan Feng(冯帆), Fucheng Liu(刘富成), Lifang Dong(董丽芳), Yafeng He(贺亚峰) Chin. Phys. B, 2016, 25 (9):  095202.  DOI: 10.1088/1674-1056/25/9/095202 Abstract ( 690 )   HTML   PDF (530KB) ( 345 )   Dust molecules are observed in a dusty plasma experiment. By using measurements with high spatial resolution, the formation and dissociation of the dust molecules are studied. The ion cloud in the wake of an upper dust grain attracts the lower dust grain nearby. When the interparticle distance between the upper dust grain and the lower one is less than a critical value, the two dust grains would form a dust molecule. The upper dust grain always leads the lower one as they travel. When the interparticle distance between them is larger than the critical value, the dust molecule would dissociate.

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Influence of tip geometry on the spatial resolution of tip enhanced Raman mapping Chao Zhang(张超), Bao-Qin Chen(陈宝琴), Zhi-Yuan Li(李志远) Chin. Phys. B, 2016, 25 (9):  095203.  DOI: 10.1088/1674-1056/25/9/095203 Abstract ( 771 )   HTML   PDF (2560KB) ( 451 )   In 2013, a breakthrough experiment pushed the Raman mapping of molecules via the tip-enhanced Raman scattering (TERS) technique to a sub-nanometer spatial resolution, going into the single-molecule level. This surprising result was well explained by accounting for the critical role of elastic molecule Rayleigh scattering within a plasmonic nanogap in enhancing both the localization and the intensity level of the Raman scattering signal. In this paper, we theoretically explore the influence of various geometric factors of the TERS system on the spatial resolution of Raman mapping, such as the tip curvature radius, tip conical angle, tip-substrate distance, and tip-molecule vertical distance. This investigation can help to find out the most critical geometric factor influencing the spatial resolution of TERS and march along in the right direction for further improving the performance of the TERS system.

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Conditions for laser-induced plasma to effectively remove nano-particles on silicon surfaces Jinghua Han(韩敬华), Li Luo(罗莉), Yubo Zhang(张玉波), Ruifeng Hu(胡锐峰), Guoying Feng(冯国英) Chin. Phys. B, 2016, 25 (9):  095204.  DOI: 10.1088/1674-1056/25/9/095204 Abstract ( 832 )   HTML   PDF (1372KB) ( 393 )   Particles can be removed from a silicon surface by means of irradiation and a laser plasma shock wave. The particles and silicon are heated by the irradiation and they will expand differently due to their different expansion coefficients, making the particles easier to be removed. Laser plasma can ionize and even vaporize particles more significantly than an incident laser and, therefore, it can remove the particles more efficiently. The laser plasma shock wave plays a dominant role in removing particles, which is attributed to its strong burst force. The pressure of the laser plasma shock wave is determined by the laser pulse energy and the gap between the focus of laser and substrate surface. In order to obtain the working conditions for particle removal, the removal mechanism, as well as the temporal and spatial characteristics of velocity, propagation distance and pressure of shock wave have been researched. On the basis of our results, the conditions for nano-particle removal are achieved.

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Influence of air pressure on the performance of plasma synthetic jet actuator Yang Li(李洋), Min Jia(贾敏), Yun Wu(吴云), Ying-hong Li(李应红), Hao-hua Zong(宗豪华), Hui-min Song(宋慧敏), Hua Liang(梁华) Chin. Phys. B, 2016, 25 (9):  095205.  DOI: 10.1088/1674-1056/25/9/095205 Abstract ( 693 )   HTML   PDF (1382KB) ( 313 )   Plasma synthetic jet actuator (PSJA) has a wide application prospect in the high-speed flow control field for its high jet velocity. In this paper, the influence of the air pressure on the performance of a two-electrode PSJA is investigated by the schlieren method in a large range from 7 kPa to 100 kPa. The energy consumed by the PSJA is roughly the same for all the pressure levels. Traces of the precursor shock wave velocity and the jet front velocity vary a lot for different pressures. The precursor shock wave velocity first decreases gradually and then remains at 345 m/s as the air pressure increases. The peak jet front velocity always appears at the first appearance of a jet, and it decreases gradually with the increase of the air pressure. A maximum precursor shock wave velocity of 520 m/s and a maximum jet front velocity of 440 m/s are observed at the pressure of 7 kPa. The averaged jet velocity in one period ranges from 44 m/s to 54 m/s for all air pressures, and it drops with the rising of the air pressure. High velocities of the precursor shock wave and the jet front indicate that this type of PSJA can still be used to influence the high-speed flow field at 7 kPa.

TOPICAL REVIEW—Physical research in liquid crystal

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Research progress of cholesteric liquid crystals with broadband reflection characteristics in application of intelligent optical modulation materials Lan-Ying Zhang(张兰英), Yan-Zi Gao(高延子), Ping Song(宋平), Xiao-Juan Wu(武晓娟), Xiao Yuan(苑晓), Bao-Feng He(何宝凤), Xing-Wu Chen(陈兴武), Wang Hu(胡望), Ren-Wei Guo(郭仁炜), Hang-Jun Ding(丁杭军), Jiu-Mei Xiao(肖久梅), Huai Yang(杨槐) Chin. Phys. B, 2016, 25 (9):  096101.  DOI: 10.1088/1674-1056/25/9/096101 Abstract ( 806 )   HTML   PDF (7760KB) ( 1357 )   Cholesteric liquid crystals (CLCs) have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship. Nowadays, by the virtue of building the self-organized nanostructures with pitch gradient or non-uniform pitch distribution, extensive work has already been performed to obtain CLC films with a broad reflection band. Based on authors' many years' research experience, this critical review systematically summarizes the physical and optical background of the CLCs with broadband reflection characteristics, methods to obtain broadband reflection of CLCs, as well as the application in the field of intelligent optical modulation materials. Combined with the research status and the advantages in the field, the important basic and applied scientific problems in the research direction are also introduced.

SPECIAL TOPIC—Physical research in liquid crystal

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Azobenzene mesogens mediated preparation of SnS nanocrystals encapsulated with in-situ N-doped carbon and their enhanced electrochemical performance for lithium ion batteries application Meng Wang(王勐), Yang Zhou(周旸), Junfei Duan(段军飞), Dongzhong Chen(谌东中) Chin. Phys. B, 2016, 25 (9):  096102.  DOI: 10.1088/1674-1056/25/9/096102 Abstract ( 833 )   HTML   PDF (1592KB) ( 384 )   In this work, azobenzene mesogen-containing tin thiolates have been synthesized, which possess ordered lamellar structures persistent to higher temperature and serve as liquid crystalline precursors. Based on the preorganized tin thiolate precursors, SnS nanocrystals encapsulated with in-situ N-doped carbon layer have been achieved through a simple solventless pyrolysis process with the azobenzene mesogenic thiolate precursor served as Sn, S, N, and C sources simultaneously. Thus prepared nanocomposite materials as anode of lithium ion batteries present a large specific capacity of 604.6 mAh·g-1 at a current density of 100 mA·g-1, keeping a high capacity retention up to 96% after 80 cycles, and display high rate capability due to the synergistic effect of well-dispersed SnS nanocrystals and N-doped carbon layer. Such encouraging results shed a light on the controlled preparation of advanced nanocomposites based on liquid crystalline metallomesogen precursors and may boost their novel intriguing applications.

TOPICAL REVIEW—Physical research in liquid crystal

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Thermo- and photo-driven soft actuators based on crosslinked liquid crystalline polymers Wei Gu(顾伟), Jia Wei(韦嘉), Yanlei Yu(俞燕蕾) Chin. Phys. B, 2016, 25 (9):  096103.  DOI: 10.1088/1674-1056/25/9/096103 Abstract ( 634 )   HTML   PDF (10704KB) ( 572 )   Crosslinked liquid crystalline polymers (CLCPs) are a type of promising material that possess both the order of liquid crystals and the properties of polymer networks. The anisotropic deformation of the CLCPs takes place when the mesogens experience order to disorder change in response to external stimuli; therefore, they can be utilized to fabricate smart actuators, which have potential applications in artificial muscles, micro-optomechanical systems, optics, and energy-harvesting fields. In this review the recent development of thermo- and photo-driven soft actuators based on the CLCPs are summarized.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Monte Carlo simulation of asymmetrical growth of cube-shaped nanoparticles Yuanyuan Wang(王元元), Huaqing Xie(谢华清), Zihua Wu(吴子华), Jiaojiao Xing(邢姣娇) Chin. Phys. B, 2016, 25 (9):  096104.  DOI: 10.1088/1674-1056/25/9/096104 Abstract ( 757 )   HTML   PDF (2739KB) ( 421 )   We simulated the asymmetrical growth of cube-shaped nanoparticles by applying the Monte Carlo method. The influence of the specific mechanisms on the crystal growth of nanoparticles has been phenomenologically described by efficient growth possibilities along different directions (or crystal faces). The roles of the thermodynamic and kinetic factors have been evaluated in three phenomenological models. The simulation results would benefit the understanding about the cause and manner of the asymmetrical growth of nanoparticles.

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Stable single helical C- and I-chains inside single-walled carbon nanotubes Z Yao(姚震), C J Liu(刘春见), Y Li(李义), X D Jing(敬晓丹), F S Meng(孟凡顺), S P Zheng(郑士鹏), X Zhao(赵星), J H Li(李久会), Z Y Qiu(邱忠媛), Q Yuan(袁泉), W X Wang(王文新), L Bi(毕磊), H Liu(刘辉), Y P Zhang(张玉璞), B B Liu(刘冰冰) Chin. Phys. B, 2016, 25 (9):  096105.  DOI: 10.1088/1674-1056/25/9/096105 Abstract ( 607 )   HTML   PDF (797KB) ( 242 )   The helicity of stable single helical carbon chains and iodine chains inside single-walled carbon nanotubes (SWCNTs) is studied by calculating the systematic van der Waals interaction energy. The results show that the optimal helical radius increases linearly with increasing tube radius, which produces a constant separation between the chain structure and the tube wall. The helical angle exhibits a ladder-like decrease with increasing tube radius, indicating that a large tube can produce a small helicity in the helical structures.

RAPID COMMUNICATION

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Controllable preparation of vertically standing graphene sheets and their wettability and supercapacitive properties Hai-Tao Zhou(周海涛), Ning Yu(喻宁), Fei Zou(邹飞), Zhao-Hui Yao(姚朝晖), Ge Gao(高歌), Cheng-Min Shen(申承民) Chin. Phys. B, 2016, 25 (9):  096106.  DOI: 10.1088/1674-1056/25/9/096106 Abstract ( 688 )   HTML   PDF (1875KB) ( 472 )   Vertically standing graphene (VSG) sheets have been fabricated by using plasma enhanced chemical vapor deposition (PECVD) method. The lateral size of VSG nanosheets could be well controlled by varying the substrate temperature. The higher temperature usually gives rise to a smaller sheet size. The wettability of VSG films was tuned between hydrophobicity and hydrophilicity by means of oxygen and hydrogen plasma treatment. The supercapacitor electrode made of VSG sheets exhibited an ideal double-layer-capacitor feature and the specific capacitance reached a value up to 9.62 F·m-2.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Influence of Tb on easy magnetization direction and magnetostriction of ferromagnetic Laves phase GdFe2 compounds Adil Murtaza, Sen Yang(杨森), Chao Zhou(周超), Xiaoping Song(宋晓平) Chin. Phys. B, 2016, 25 (9):  096107.  DOI: 10.1088/1674-1056/25/9/096107 Abstract ( 939 )   HTML   PDF (1614KB) ( 393 )   The crystal structure, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase GdFe2 compound have been investigated. High resolution synchrotron x-ray diffraction (XRD) analysis shows that GdFe2 has a lower cubic symmetry with easy magnetization direction (EMD) along [100] below Curie temperature TC. The replacement of Gd with a small amount of Tb changes the EMD to [111]. The Curie temperature decreases while the field dependence of the saturation magnetization (Ms) measured in temperature range 5-300 K varies with increasing Tb concentration. Coercivity Hc increases with increasing Tb concentration and decays exponentially as temperature increases. The anisotropy in GdFe2 is so weak that some of the rare-earth substitution plays an important role in determining the easy direction of magnetization in GdFe2. The calculated magnetostrictive constant λ100 shows a small value of 37×10-6. This value agrees well with experimental data 30×10-6. Under a relatively small magnetic field, GdFe2 exhibits a V-shaped positive magnetostriction curve. When the field is further increased, the crystal exhibits a negative magnetostriction curve. This phenomenon has been discussed in term of magnetic domain switching. Furthermore, magnetostriction increases with increasing Tb concentration. Our work leads to a simple and unified mesoscopic explanation for magnetostriction in ferromagnets. It may also provide insight for developing novel functional materials.

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Electronic structure and magnetic properties of (Cu, N)-codoped 3C-SiC studied by first-principles calculations Feng-chun Pan(潘凤春), Zhi-peng Chen(陈治鹏), Xue-ling Lin(林雪玲), Fu Zheng(郑富), Xu-ming Wang(王旭明), Huan-ming Chen(陈焕铭) Chin. Phys. B, 2016, 25 (9):  096108.  DOI: 10.1088/1674-1056/25/9/096108 Abstract ( 747 )   HTML   PDF (437KB) ( 351 )   The electronic structures and magnetic properties of the Cu and N codoped 3C-SiC system have been investigated by the first-principles calculation. The results show that the Cu doped SiC system prefers the anti-ferromagnetic (AFM) state. Compared to the Cu doped system, the ionicities of C-Cu and C-Si in Cu and N codoped SiC are respectively enhanced and weakened. Especially, the Cu and N codoped SiC systems favor the ferromagnetic (FM) coupling. The FM interactions can be explained by virtual hopping. However, higher N concentration will weaken the ferromagnetism. In order to keep the FM interaction, the N concentration should be restricted within 9.3% according to our analysis.

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Pattern dependence in synergistic effects of total dose onsingle-event upset hardness Hongxia Guo(郭红霞), Lili Ding(丁李利), Yao Xiao(肖尧), Fengqi Zhang(张凤祁), Yinhong Luo(罗尹虹), Wen Zhao(赵雯), Yuanming Wang(王园明) Chin. Phys. B, 2016, 25 (9):  096109.  DOI: 10.1088/1674-1056/25/9/096109 Abstract ( 828 )   HTML   PDF (325KB) ( 246 )   The pattern dependence in synergistic effects was studied in a 0.18 μ static random access memory (SRAM) circuit. Experiments were performed under two SEU test environments: 3 MeV protons and heavy ions. Measured results show different trends. In heavy ion SEU test, the degradation in the peripheral circuitry also existed because the measured SEU cross section decreased regardless of the patterns written to the SRAM array. TCAD simulation was performed. TID-induced degradation in nMOSFETs mainly induced the imprint effect in the SRAM cell, which is consistent with the measured results under the proton environment, but cannot explain the phenomena observed under heavy ion environment. A possible explanation could be the contribution from the radiation-induced GIDL in pMOSFETs.

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Comparison of radiation degradation induced by x-rayand 3-MeV protons in 65-nm CMOS transistors Lili Ding(丁李利), Simone Gerardin, Marta Bagatin, Dario Bisello, Serena Mattiazzo, Alessandro Paccagnella Chin. Phys. B, 2016, 25 (9):  096110.  DOI: 10.1088/1674-1056/25/9/096110 Abstract ( 886 )   HTML   PDF (251KB) ( 334 )   The total ionizing dose (TID) response of 65-nm CMOS transistors is studied by 10-keV x-ray and 3-MeV protons up to 1 Grad (SiO2) total dose. The degradation levels induced by the two radiation sources are different to some extent. The main reason is the interface dose enhancement due to the thin gate oxide and the low energy photons. The holes' recombination also contributes to the difference. Compared to these two mechanisms, the influence of the dose rate is negligible.

SPECIAL TOPIC—Physical research in liquid crystal

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Effect of fluorine groups and different terminal chains on the electro-isomerization of azobenzene liquid crystals Jing-Jing Xiong(熊晶晶), Dong Shen(沈冬), Zhi-Gang Zheng(郑致刚), Xiao-Qian Wang(王骁乾) Chin. Phys. B, 2016, 25 (9):  096401.  DOI: 10.1088/1674-1056/25/9/096401 Abstract ( 820 )   HTML   PDF (620KB) ( 259 )   A series of azobenzene liquid crystals with one or two terminal acrylate groups were synthesized and their polymers were fabricated. The azobenzene liquid crystals and their polymers achieved the photoisomerization from the liquid crystalline trans-isomer to the isotropic cis-isomer with UV irradiation. Then, the cis to trans isomerization induced by an electric field was studied, the time required for electro-isomerization was measured, the texture change and absorption variation from cis to trans form induced by the electric field were observed clearly, and the time required for electro-isomerization was much shorter than that for thermal relaxation. The influence of the polar group (fluorine), terminal acrylate group, and flexible alkyl chain on the time of electro-isomerization was studied. The results show that the compounds with polar fluorine group require shorter time for electro-isomerization and the polymerization of terminal acrylate group delays the electro-isomerization.

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Phase behaviors of binary mixtures composed of electron-richand electron-poor triphenylene discotic liquid crystals Lingling An(安玲玲), Min Jing(景敏), Bo Xiao(肖波), Xiao-Yan Bai(白小燕), Qing-Dao Zeng(曾庆祷), Ke-Qing Zhao(赵可清) Chin. Phys. B, 2016, 25 (9):  096402.  DOI: 10.1088/1674-1056/25/9/096402 Abstract ( 711 )   HTML   PDF (2850KB) ( 453 )   Disk-like liquid crystals (DLCs) can self-assemble to ordered columnar mesophases and are intriguing one-dimensional organic semiconductors with high charge carrier mobility. To improve their applicable property of mesomorphic temperature ranges, we exploit the binary mixtures of electronic donor-acceptor DLC materials. The electron-rich 2,3,6,7,10,11-hexakis(alkoxy)triphenylenes (C4, C6, C8, C10, C12) and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated. The mesomorphism of the 1:1 (molar ratio) mixtures has been characterized by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and small angel x-ray scattering (SAXS). The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy (STM). The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Growth condition optimization and mobility enhancement through inserting AlAs monolayer in the InP-based InxGa1-xAs/In0.52Al0.48As HEMT structures Shu-Xing Zhou(周书星), Ming Qi(齐鸣), Li-Kun Ai(艾立鹍), An-Huai Xu(徐安怀) Chin. Phys. B, 2016, 25 (9):  096801.  DOI: 10.1088/1674-1056/25/9/096801 Abstract ( 730 )   HTML   PDF (303KB) ( 397 )   The structure of InP-based InxGa1-xAs/In0.52Al0.48As pseudomorphic high electron mobility transistor (PHEMT) was optimized in detail. Effects of growth temperature, growth interruption time, Siδ-doping condition, channel thickness and In content, and inserted AlAs monolayer (ML) on the two-dimensional electron gas (2DEG) performance were investigated carefully. It was found that the use of the inserted AlAs monolayer has an enhancement effect on the mobility due to the reduction of interface roughness and the suppression of Si movement. With optimization of the growth parameters, the structures composed of a 10 nm thick In0.75Ga0.25As channel layer and a 3 nm thick AlAs/In0.52Al0.48As superlattices spacer layer exhibited electron mobilities as high as 12500 cm2·V-1·s-1 (300 K) and 53500 cm2·V-1·s-1 (77 K) and the corresponding sheet carrier concentrations (Ns) of 2.8×1012 cm-2 and 2.9×1012 cm-2, respectively. To the best of the authors' knowledge, this is the highest reported room temperature mobility for InP-based HEMTs with a spacer of 3 nm to date.

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Strain effect on graphene nanoribbon carrier statistic in the presence of non-parabolic band structure N A Izuani Che Rosid, M T Ahmadi, Razali Ismail Chin. Phys. B, 2016, 25 (9):  096802.  DOI: 10.1088/1674-1056/25/9/096802 Abstract ( 766 )   HTML   PDF (966KB) ( 504 )   The effect of tensile uniaxial strain on the non-parabolic electronic band structure of armchair graphene nanoribbon (AGNR) is investigated. In addition, the density of states and the carrier statistic based on the tight-binding Hamiltonian are modeled analytically. It is found that the property of AGNR in the non-parabolic band region is varied by the strain. The tunable energy band gap in AGNR upon strain at the minimum energy is described for each of n-AGNR families in the non-parabolic approximation. The behavior of AGNR in the presence of strain is attributed to the breakable AGNR electronic band structure, which varies the physical properties from its normality. The linear relation between the energy gap and the electrical properties is featured to further explain the characteristic of the deformed AGNR upon strain.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Effect of NO annealing on charge traps in oxide insulator and transition layer for 4H-SiC metal-oxide-semiconductor devices Yifan Jia(贾一凡), Hongliang Lv(吕红亮), Yingxi Niu(钮应喜), Ling Li(李玲), Qingwen Song(宋庆文), Xiaoyan Tang(汤晓燕), Chengzhan Li(李诚瞻), Yanli Zhao(赵艳黎), Li Xiao(肖莉), Liangyong Wang(王梁永), Guangming Tang(唐光明), Yimen Zhang(张义门), Yuming Zhang(张玉明) Chin. Phys. B, 2016, 25 (9):  097101.  DOI: 10.1088/1674-1056/25/9/097101 Abstract ( 719 )   HTML   PDF (775KB) ( 342 )   The effect of nitric oxide (NO) annealing on charge traps in the oxide insulator and transition layer in n-type 4H-SiC metal-oxide-semiconductor (MOS) devices has been investigated using the time-dependent bias stress (TDBS), capacitance-voltage (C-V), and secondary ion mass spectroscopy (SIMS). It is revealed that two main categories of charge traps, near interface oxide traps (Nniot) and oxide traps (Not), have different responses to the TDBS and C-V characteristics in NO-annealed and Ar-annealed samples. The Nniot are mainly responsible for the hysteresis occurring in the bidirectional C-V characteristics, which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor. However, Not is mainly responsible for the TDBS induced C-V shifts. Electrons tunneling into the Not are hardly released quickly when suffering TDBS, resulting in the problem of the threshold voltage stability. Compared with the Ar-annealed sample, Nniot can be significantly suppressed by the NO annealing, but there is little improvement of Not. SIMS results demonstrate that the Nniot are distributed within the transition layer, which correlated with the existence of the excess silicon. During the NO annealing process, the excess Si atoms incorporate into nitrogen in the transition layer, allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.

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Unified semiclassical approach to electronic transport from diffusive to ballistic regimes Hot! Hao Geng(耿浩), Wei-Yin Deng(邓伟胤), Yue-Jiao Ren(任月皎), Li Sheng(盛利), Ding-Yu Xing(邢定钰) Chin. Phys. B, 2016, 25 (9):  097201.  DOI: 10.1088/1674-1056/25/9/097201 Abstract ( 857 )   HTML   PDF (354KB) ( 527 )   We show that by integrating out the electric field and incorporating proper boundary conditions, a Boltzmann equation can describe electron transport properties, continuously from the diffusive to ballistic regimes. General analytical formulas of the conductance in D=1,2,3 dimensions are obtained, which recover the Boltzmann-Drude formula and Landauer-Büttiker formula in the diffusive and ballistic limits, respectively. This intuitive and efficient approach can be applied to investigate the interplay of system size and impurity scattering in various charge and spin transport phenomena, when the quantum interference effect is not important.

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Spectral response modeling and analysis of p-n-p In0.53Ga0.47As/InP HPTs Jun Chen(陈俊), Jiabing Lv(吕加兵) Chin. Phys. B, 2016, 25 (9):  097202.  DOI: 10.1088/1674-1056/25/9/097202 Abstract ( 832 )   HTML   PDF (233KB) ( 289 )   We report our results on the modeling of the spectral response of the near-infrared (NIR) lattice-matched p-n-p In0.53Ga0.47As/InP heterojunction phototransistors (HPTs). The spectral response model is developed from the solution of the steady state continuity equations that dominate the excess optically generated minority-carriers in the active regions of the HPTs with accurate boundary conditions. In addition, a detailed optical-power absorption profile is constructed for the device modeling. The calculated responsivity is in good agreement with the measured one for the incident radiation at 980 nm, 1310 nm, and 1550 nm. Furthermore, the variation in the responsivity of the device with the base region width is analyzed.

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Different optical properties in different periodic slot cavity geometrical morphologies Jing Zhou(周静), Meng Shen(沈萌), Lan Du(杜澜), Caisong Deng(邓彩松), Haibin Ni(倪海彬), Ming Wang(王鸣) Chin. Phys. B, 2016, 25 (9):  097301.  DOI: 10.1088/1674-1056/25/9/097301 Abstract ( 901 )   HTML   PDF (1049KB) ( 462 )   In this paper, optical properties of two-dimensional periodic annular slot cavity arrays in hexagonal close-packing on a silica substrate are theoretically characterized by finite difference time domain (FDTD) simulation method. By simulating reflectance spectra, electric field distribution, and charge distribution, we confirm that multiple cylindrical surface plasmon resonances can be excited in annular inclined slot cavities by linearly polarized light, in which the four reflectance dips are attributed to Fabry-Perot cavity resonances in the coaxial cavity. A coaxial waveguide mode TE11 will exist in these annular cavities, and the wavelengths of these reflectance dips are effectively tailored by changing the geometrical pattern of slot cavity and the dielectric materials filled in the cavities. These resonant wavelengths are localized in annular cavities with large electric field enhancement and dissipate gradually due to metal loss. The formation of an absorption peak can be explained from the aspect of phase matching conditions. We observed that the proposed structure can be tuned over the broad spectral range of 600-4000 nm by changing the outer and inner radii of the annular gaps, gap surface topography. Meanwhile, different lengths of the cavity may cause the shift of resonance dips. Also, we study the field enhancement at different vertical locations of the slit. In addition, dielectric materials filling in the annular gaps will result in a shift of the resonance wavelengths, which make the annular cavities good candidates for refractive index sensors. The refractive index sensitivity of annular cavities can also be tuned by the geometry size and the media around the cavity. Annular cavities with novel applications can be implied as surface enhanced Raman spectra substrates, refractive index sensors, nano-lasers, and optical trappers.

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A high-quality factor hybrid plasmonic nanocavity based on distributed Bragg reflectors Hot! Linlin Tu(屠林林), Chi Zhang(张弛), Zhong Huang(黄忠), Jason Yau, Peng Zhan(詹鹏), Zhenlin Wang(王振林) Chin. Phys. B, 2016, 25 (9):  097302.  DOI: 10.1088/1674-1056/25/9/097302 Abstract ( 821 )   HTML   PDF (552KB) ( 401 )   Herein, we propose a high-quality (Q) factor hybrid plasmonic nanocavity based on distributed Bragg reflectors (DBRs) with low propagation loss and extremely strong mode confinement. This hybrid plasmonic nanocavity is composed of a high-index cylindrical nanowire separated from a metal surface possessing shallow DBRs gratings by a sufficiently thin low-index dielectric layer. The hybrid plasmonic nanocavity possesses advantages such as a high Purcell factor (Fp) of up to nearly 20000 and a gain threshold approaching 266 cm-1 at 1550 nm, promising a greater potential in deep sub-wavelength lasing applications.

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Charge susceptibilities of armchair graphene nanoribbon in the presence of magnetic field H Rezania, F Azizi Chin. Phys. B, 2016, 25 (9):  097303.  DOI: 10.1088/1674-1056/25/9/097303 Abstract ( 593 )   HTML   PDF (1007KB) ( 582 )   We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green's function approach in the context of tight binding model Hamiltonian. Specifically, the effects of magnetic field on the the plasmon modes of armchair graphene nanoribbon are investigated via calculating the correlation function of charge density operators. Our results show that the increase of magnetic field makes the high-frequency plasmon mode for both metallic and insulating cases disappear. We also show that low-frequency plasmon mode for metallic nanoribbon appears due to increase of magnetic field. Furthermore, the number of collective excitation modes increases with ribbon width at zero magnetic field. Finally, the temperature dependence of the static charge structure factor of armchair graphene nanoribbon is studied. The effects of both magnetic field and ribbon width on the static charge structure factor are discussed in detail.

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Scaling dependence of memory windows and different carrier charging behaviors in Si nanocrystal nonvolatile memory devices Jie Yu(于杰), Kun-ji Chen(陈坤基), Zhong-yuan Ma(马忠元), Xin-xin Zhang(张鑫鑫), Xiao-fan Jiang(江小帆), Yang-qing Wu(吴仰晴), Xin-fan Huang(黄信凡), Shunri Oda Chin. Phys. B, 2016, 25 (9):  097304.  DOI: 10.1088/1674-1056/25/9/097304 Abstract ( 696 )   HTML   PDF (1151KB) ( 322 )   Based on the charge storage mode, it is important to investigate the scaling dependence of memory performance in silicon nanocrystal (Si-NC) nonvolatile memory (NVM) devices for its scaling down limit. In this work, we made eight kinds of test key cells with different gate widths and lengths by 0.13-μm node complementary metal oxide semiconductor (CMOS) technology. It is found that the memory windows of eight kinds of test key cells are almost the same of about 1.64 V @ ± 7 V/1 ms, which are independent of the gate area, but mainly determined by the average size (12 nm) and areal density (1.8×1011/cm2) of Si-NCs. The program/erase (P/E) speed characteristics are almost independent of gate widths and lengths. However, the erase speed is faster than the program speed of test key cells, which is due to the different charging behaviors between electrons and holes during the operation processes. Furthermore, the data retention characteristic is also independent of the gate area. Our findings are useful for further scaling down of Si-NC NVM devices to improve the performance and on-chip integration.

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Structural, electronic, and magnetic properties of transition-metal atom adsorbed two-dimensional GaAs nanosheet Jia Luo(罗佳), Gang Xiang(向钢), Tian Yu(余天), Mu Lan(兰木), Xi Zhang(张析) Chin. Phys. B, 2016, 25 (9):  097305.  DOI: 10.1088/1674-1056/25/9/097305 Abstract ( 810 )   HTML   PDF (761KB) ( 434 )   By using first-principles calculations within the framework of density functional theory, the electronic and magnetic properties of 3d transitional metal (TM) atoms (from Sc to Zn) adsorbed monolayer GaAs nanosheets (GaAsNSs) are systematically investigated. Upon TM atom adsorption, GaAsNS, which is a nonmagnetic semiconductor, can be tuned into a magnetic semiconductor (Sc, V, and Fe adsorption), a half-metal (Mn adsorption), or a metal (Co and Cu adsorption). Our calculations show that the strong p-d hybridization between the 3d orbit of TM atoms and the 4p orbit of neighboring As atoms is responsible for the formation of chemical bonds and the origin of magnetism in the GaAsNSs with Sc, V, and Fe adsorption. However, the Mn 3d orbit with more unpaired electrons hybridizes not only with the As 4p orbit but also with the Ga 4p orbit, resulting in a stronger exchange interaction. Our results may be useful for electronic and magnetic applications of GaAsNS-based materials.

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X-band inverse class-F GaN internally-matched power amplifier Bo-Chao Zhao(赵博超), Yang Lu(卢阳), Wen-Zhe Han(韩文哲), Jia-Xin Zheng(郑佳欣), Heng-Shuang Zhang(张恒爽), Pei-jun Ma(马佩军), Xiao-Hua Ma(马晓华), Yue Hao(郝跃) Chin. Phys. B, 2016, 25 (9):  097306.  DOI: 10.1088/1674-1056/25/9/097306 Abstract ( 805 )   HTML   PDF (861KB) ( 815 )   An X-band inverse class-F power amplifier is realized by a 1-mm AlGaN/GaN high electron mobility transistor (HEMT). The intrinsic and parasitic components inside the transistor, especially output capacitor Cds, influence the harmonic impedance heavily at the X-band, so compensation design is used for meeting the harmonic condition of inverse class-F on the current source plane. Experiment results show that, in the continuous-wave mode, the power amplifier achieves 61.7% power added efficiency (PAE), which is 16.3% higher than the class-AB power amplifier realized by the same kind of HEMT. To the best of our knowledge, this is the first inverse class-F GaN internally-matched power amplifier, and the PAE is quite high at the X-band.

RAPID COMMUNICATION

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Carrier transport in III-V quantum-dot structures for solar cells or photodetectors Hot! Wenqi Wang(王文奇), Lu Wang(王禄), Yang Jiang(江洋), Ziguang Ma(马紫光), Ling Sun(孙令), Jie Liu(刘洁), Qingling Sun(孙庆灵), Bin Zhao(赵斌), Wenxin Wang(王文新), Wuming Liu(刘伍明), Haiqiang Jia(贾海强), Hong Chen(陈弘) Chin. Phys. B, 2016, 25 (9):  097307.  DOI: 10.1088/1674-1056/25/9/097307 Abstract ( 837 )   HTML   PDF (593KB) ( 460 )   According to the well-established light-to-electricity conversion theory, resonant excited carriers in the quantum dots will relax to the ground states and cannot escape from the quantum dots to form photocurrent, which have been observed in quantum dots without a p-n junction at an external bias. Here, we experimentally observed more than 88% of the resonantly excited photo carriers escaping from InAs quantum dots embedded in a short-circuited p-n junction to form photocurrent. The phenomenon cannot be explained by thermionic emission, tunneling process, and intermediate-band theories. A new mechanism is suggested that the photo carriers escape directly from the quantum dots to form photocurrent rather than relax to the ground state of quantum dots induced by a p-n junction. The finding is important for understanding the low-dimensional semiconductor physics and applications in solar cells and photodiode detectors.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Thermal fluctuation conductivity and dimensionality in iron-based superconductors Rui Wang(王蕊), Ding-Ping Li(李定平) Chin. Phys. B, 2016, 25 (9):  097401.  DOI: 10.1088/1674-1056/25/9/097401 Abstract ( 759 )   HTML   PDF (444KB) ( 480 )   The time-dependent Ginzburg-Landau Lawrence-Doniach model is used to investigate the superconducting fluctuation electrical conductivities. The theoretical result based on the self-consistent Gaussian approximation is used to fit the transport measurement data of iron-based superconductors F-doped LaOFeAs and BaFe2-xNixAs2. We demonstrate that LaOFeAs shows layered behavior, while BaFe2-xNixAs2 is more of a 3D feature. The conductivity in the region near Tc is well described by the theoretical formula.

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Observation of selective surface element substitution in FeTe0.5Se0.5 superconductor thin film exposed to ambient air bysynchrotron radiation spectroscopy Nian Zhang(张念), Chen Liu(刘晨), Jia-Li Zhao(赵佳丽), Tao Lei(雷涛), Jia-Ou Wang(王嘉鸥), Hai-Jie Qian(钱海杰), Rui Wu(吴蕊), Lei Yan(颜雷), Hai-Zhong Guo(郭海中), Kurash Ibrahim(奎热西) Chin. Phys. B, 2016, 25 (9):  097402.  DOI: 10.1088/1674-1056/25/9/097402 Abstract ( 733 )   HTML   PDF (850KB) ( 458 )   A systematic investigation of oxidation on a superconductive FeTe0.5Se0.5 thin film, which was grown on Nb-doped SrTiO3 (001) by pulsed laser deposition, has been carried out. The sample was exposed to ambient air for one month for oxidation. Macroscopically, the exposed specimen lost its superconductivity due to oxidation. The specimen was subjected to in situ synchrotron radiation photoelectron spectroscopy (PES) and x-ray absorption spectroscopy (XAS) measurements following cycles of annealing and argon ion etching treatments to unravel what happened in the electronic structure and composition after exposure to air. By the spectroscopic measurements, we found that the as-grown FeTe0.5Se0.5 superconductive thin film experienced an element selective substitution reaction. The oxidation preferentially proceeds through pumping out the Te and forming Fe-O bonds by O substitution of Te. In addition, our results certify that in situ vacuum annealing and low-energy argon ion etching methods combined with spectroscopy are suitable for depth element and valence analysis of layered structure superconductor materials.

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Novel 0-π transitions in Josephson junctions between noncentrosymmetric superconductors Jun-Feng Liu(刘军丰), Huan Zhang(张欢), Jun Wang(汪军) Chin. Phys. B, 2016, 25 (9):  097403.  DOI: 10.1088/1674-1056/25/9/097403 Abstract ( 878 )   HTML   PDF (3468KB) ( 308 )   We study the Josephson effect between two noncentrosymmetric superconductors (NCSs) with opposite polarization vectors of Rashba spin-orbit coupling (RSOC). We find a 0-π transition driven by the triplet-singlet ratio of NCSs. Different from conventional 0-π transitions, the Andreev bound states change their energy range instead of phase shift in the 0-π transition found here. This novel property results in a feature that the critical current becomes almost zero at the transition point, not only a minimum. Furthermore, when the directions of RSOC polarization vectors are the same in two NCSs, the similar effect can also be found in the presence of a perpendicular exchange field or a Dresselhause spin-orbit coupling in the interlayer. We find novel oscillations of critical current without 0-π transition. These novel 0-π transitions or oscillations of critical current present new understanding of the Josephson effect and can also serve as a tool to determine the unknown triplet-singlet ratio of NCSs.

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Manipulating magnetic anisotropies of Co/MgO(001) ultrathin films via oblique deposition Syed Sheraz Ahmad, Wei He(何为), Jin Tang(汤进), Yong Sheng Zhang(张永圣), Bo Hu(胡泊), Jun Ye(叶军), Qeemat Gul, Xiang-Qun Zhang(张向群), Zhao-Hua Cheng(成昭华) Chin. Phys. B, 2016, 25 (9):  097501.  DOI: 10.1088/1674-1056/25/9/097501 Abstract ( 812 )   HTML   PDF (1058KB) ( 380 )   We present a systematic investigation of magnetic anisotropy induced by oblique deposition of Co thin films on MgO (001) substrates by molecular beam epitaxy at different deposition angles, i.e., 0°, 30°, 45°, 60°, and 75° with respect to the surface normal. Low energy electron diffraction (LEED), surface magneto-optical Kerr effect (SMOKE), and anisotropic magnetoresistance (AMR) setups were employed to investigate the magnetic properties of cobalt films. The values of in-plane uniaxial magnetic anisotropy (UMA) constant Ku and four-fold magnetocrystalline anisotropy constant K1 were derived from magnetic torque curves on the base of AMR results. It was found that the value of Ku increases with increasing deposition angle with respect to the surface normal, while the value of K1 remains almost constant for all the samples. Furthermore, by using MOKE results, the Ku values of the films deposited obliquely were also derived from the magnetization curves along hard axis. The results of AMR method were then compared with that of hard axis fitting method (coherent rotation) and found that both methods have almost identical values of UMA constant for each sample.

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Room-temperature ferromagnetism observed in Nd-doped In2O3 dilute magnetic semiconducting nanowires Zhanpeng Lv(吕占朋), Junran Zhang(张军然), Wei Niu(钮伟), Minhao Zhang(张敏昊), Li Song(宋丽), Hairong Zhu(朱海荣), Xuefeng Wang(王学锋) Chin. Phys. B, 2016, 25 (9):  097502.  DOI: 10.1088/1674-1056/25/9/097502 Abstract ( 784 )   HTML   PDF (668KB) ( 440 )   Nd-doped In2O3 nanowires were fabricated by an Au-catalyzed chemical vapor deposition method. Nd atoms were successfully doped into the In2O3 host lattice structure, as revealed by energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. Robust room temperature ferromagnetism was observed in Nd-doped In2O3 nanowires, which was attributed to the long-range-mediated magnetization among Nd3+-vacancy complexes through percolation-bound magnetic polarons.

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Effects of (La, Sr) co-doping on electrical conduction and magnetic properties of BiFeO3 nanoparticles Li Liu(刘莉), Shouyu Wang(王守宇), Zi Yin(殷子), Weifang Liu(刘卫芳), Xunling Xu(徐训岭), Chuang Zhang(张闯), Xiu Li(李秀), Jiabin Yang(杨佳斌) Chin. Phys. B, 2016, 25 (9):  097801.  DOI: 10.1088/1674-1056/25/9/097801 Abstract ( 711 )   HTML   PDF (1696KB) ( 385 )   Multiferroic material as a photovoltaic material has gained considerable attention in recent years. Nanoparticles (NPs) La0.1Bi0.9-xSrxFeOy (LBSF, x=0, 0.2, 0.4) with dopant Sr2+ ions were synthesized by the sol-gel method. A systematic change in the crystal structure from rhombohedral to tetragonal upon increasing Sr doping was observed. There is an obvious change in the particle size from 180 nm to 50 nm with increasing Sr substitution into LBFO. It was found that Sr doping effectively narrows the band gap from ～2.08 eV to ～1.94 eV, while it leads to an apparent enhancement in the electrical conductivity of LBSF NPs, making a transition from insulator to semiconductor. This suggests an effective way to modulate the conductivity of BiFeO3-based multiferroic materials with pure phase by co-doping with La and Sr at the A sites of BiFeO3.

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Effects of dispersion and filtering induced by periodic multilayer mirrors reflection on attosecond pulses Cheng-You Lin(林承友), Liang Yin(尹亮), Shu-Jing Chen(陈淑静), Zhao-Yang Chen(陈朝阳), Ying-Chun Ding(丁迎春) Chin. Phys. B, 2016, 25 (9):  097802.  DOI: 10.1088/1674-1056/25/9/097802 Abstract ( 810 )   HTML   PDF (715KB) ( 255 )   Using temporal and spectral methods, the effects of dispersion and filtering induced by Mo/Si multilayer mirrors reflection on incident attosecond pulses were studied. First, two temporal parameters, the pulse broadening factor, and the energy loss factor, were defined to evaluate the effects of dispersion and filtering. Then, by analyzing these temporal parameters, we investigated and compared the dispersion and filtering effects on attosecond pulses. In addition, we explored the origins of pulse broadening and energy loss by analyzing the spectral and temporal characteristics of periodic Mo/Si multilayer mirrors. The results indicate that the filtering effect induced by Mo/Si multilayer mirrors reflection is the dominant reason for pulse broadening and energy loss.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Mid/far-infrared photo-detectors based on graphene asymmetric quantum wells E Ben Salem, R Chaabani, S Jaziri Chin. Phys. B, 2016, 25 (9):  098101.  DOI: 10.1088/1674-1056/25/9/098101 Abstract ( 644 )   HTML   PDF (2461KB) ( 506 )   We conducted a theoretical study on the electronic properties of a single-layer graphene asymmetric quantum well. Quantification of energy levels is limited by electron-hole conversion at the barrier interfaces and free-electron continuum. Electron-hole conversion at the barrier interfaces can be controlled by introducing an asymmetry between barriers and taking into account the effect of the interactions of the graphene sheet with the substrate. The interaction with the substrate induces an effective mass to carriers, allowing observation of Fabry-Pérot resonances under normal incidence and extinction of Klein tunneling. The asymmetry, between barriers creates a transmission gap between confined states and free-electron continuum, allowing the large graphene asymmetric quantum well to be exploited as a photo-detector operating at mid- and far-infrared frequency regimes.

SPECIAL TOPIC—Physical research in liquid crystal

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Synthesis of ZnO quantum dots and their agglomeration mechanisms along with emission spectra based on ageing time and temperature Bo Qiao(乔泊), Suling Zhao(赵谡玲), Zheng Xu(徐征), Xurong Xu(徐叙瑢) Chin. Phys. B, 2016, 25 (9):  098102.  DOI: 10.1088/1674-1056/25/9/098102 Abstract ( 723 )   HTML   PDF (1964KB) ( 469 )   The ZnO quantum dots (QDs) were synthesized with improved chemical solution method. The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm, which are homogeneously dispersed in ethanol. The optical absorption edge shifts from 370 nm of bulk material to 359 nm of QD materials due to the quantum size effect, while the photoluminescence peak shifts from 375 nm to 387 nm with the increase of the density of ZnO QDs. The stability of ZnO QDs was studied with different dispersion degrees at 0 ℃ and at room temperature of 25 ℃. The agglomeration mechanisms and their relationship with the emission spectra were uncovered for the first time. With the ageing of ZnO QDs, the agglomeration is aggravated and the surface defects increase, which leads to the defect emission.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Phonon-assisted excitation energy transfer in photosynthetic systems Hao Chen(陈浩), Xin Wang(王信), Ai-Ping Fang(方爱平), Hong-Rong Li(李宏荣) Chin. Phys. B, 2016, 25 (9):  098201.  DOI: 10.1088/1674-1056/25/9/098201 Abstract ( 703 )   HTML   PDF (307KB) ( 312 )   The phonon-assisted process of energy transfer aiming at exploring the newly emerging frontier between biology and physics is an issue of central interest. This article shows the important role of the intramolecular vibrational modes for excitation energy transfer in the photosynthetic systems. Based on a dimer system consisting of a donor and an acceptor modeled by two two-level systems, in which one of them is coupled to a high-energy vibrational mode, we derive an effective Hamiltonian describing the vibration-assisted coherent energy transfer process in the polaron frame. The effective Hamiltonian reveals in the case that the vibrational mode dynamically matches the energy detuning between the donor and the acceptor, the original detuned energy transfer becomes resonant energy transfer. In addition, the population dynamics and coherence dynamics of the dimer system with and without vibration-assistance are investigated numerically. It is found that, the energy transfer efficiency and the transfer time depend heavily on the interaction strength of the donor and the high-energy vibrational mode, as well as the vibrational frequency. The numerical results also indicate that the initial state and dissipation rate of the vibrational mode have little influence on the dynamics of the dimer system. Results obtained in this article are not only helpful to understand the natural photosynthesis, but also offer an optimal design principle for artificial photosynthesis.

SPECIAL TOPIC—Physical research in liquid crystal

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Fullerene solar cells with cholesteric liquid crystal doping Lulu Jiang(姜璐璐), Yurong Jiang(蒋玉荣), Congcong Zhang(张丛丛), Zezhang Chen(陈泽章), Ruiping Qin(秦瑞平), Heng Ma(马恒) Chin. Phys. B, 2016, 25 (9):  098401.  DOI: 10.1088/1674-1056/25/9/098401 Abstract ( 782 )   HTML   PDF (1188KB) ( 312 )   This paper reports the doping effect of cholesteric liquid crystal 3β-Hydroxy-5-cholestene 3-oleate on polymer solar cells composed of the poly 3-hexyl thiophene and the fullerene derivative. With a doping ratio of 0.3 wt%, the device achieves an ideal improvement on the shunt resistor and the fill factor. Compared with the reference cell, the power conversion efficiency of the doped cell is improved 24%. The photoelectric measurement and the active layer characterization indicate that the self-assembly liquid crystal can improve the film crystallization and reduce the membrane defect.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Non-ionizing energy loss calculations for modeling electron-induced degradation of Cu(In, Ga)Se2 thin-film solar cells Ming Lu(鲁明), Jing Xu(徐晶), Jian-Wei Huang(黄建微) Chin. Phys. B, 2016, 25 (9):  098402.  DOI: 10.1088/1674-1056/25/9/098402 Abstract ( 779 )   HTML   PDF (272KB) ( 446 )   The lowest energies which make Cu, In, Ga, and Se atoms composing Cu(In, Ga)Se2 (CIGS) material displaced from their lattice sites are evaluated, respectively. The non-ionizing energy loss (NIEL) for electron in CIGS material is calculated analytically using the Mott differential cross section. The relation of the introduction rate (k) of the recombination centers to NIEL is modified, then the values of k at different electron energies are calculated. Degradation modeling of CIGS thin-film solar cells irradiated with various-energy electrons is performed according to the characterization of solar cells and the recombination centers. The validity of the modeling approach is verified by comparison with the experimental data.

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Self-organized phenomena of pedestrian counterflow through a wide bottleneck in a channel Li-Yun Dong(董力耘), Dong-Kai Lan(蓝冬恺), Xiang Li(李翔) Chin. Phys. B, 2016, 25 (9):  098901.  DOI: 10.1088/1674-1056/25/9/098901 Abstract ( 823 )   HTML   PDF (1544KB) ( 336 )   The pedestrian counterflow through a bottleneck in a channel shows a variety of flow patterns due to self-organization. In order to reveal the underlying mechanism, a cellular automaton model was proposed by incorporating the floor field and the view field which reflects the global information of the studied area and local interactions with others. The presented model can well reproduce typical collective behaviors, such as lane formation. Numerical simulations were performed in the case of a wide bottleneck and typical flow patterns at different density ranges were identified as rarefied flow, laminar flow, interrupted bidirectional flow, oscillatory flow, intermittent flow, and choked flow. The effects of several parameters, such as the size of view field and the width of opening, on the bottleneck flow are also analyzed in detail. The view field plays a vital role in reproducing self-organized phenomena of pedestrian. Numerical results showed that the presented model can capture key characteristics of bottleneck flows.