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Chin. Phys. Lett.  
  Chin. Phys. Lett.--2016, 33 (09)   Published: 26 August 2016
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Computing Quantum Bound States on Triply Punctured Two-Sphere Surface

K. T. Chan, H. Zainuddin, K. A. M. Atan, A. A. Siddig
Chin. Phys. Lett. 2016, 33 (09): 090301 doi: 10.1088/0256-307X/33/9/090301
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We are interested in a quantum mechanical system on a triply punctured two-sphere surface with hyperbolic metric. The bound states on this system are described by the Maass cusp forms (MCFs) which are smooth square integrable eigenfunctions of the hyperbolic Laplacian. Their discrete eigenvalues and the MCF are not known analytically. We solve numerically using a modified Hejhal and Then algorithm, which is suitable to compute eigenvalues for a surface with more than one cusp. We report on the computational results of some lower-lying eigenvalues for the triply punctured surface as well as providing plots of the MCF using GridMathematica.

Total Pairwise Quantum Correlation and Entanglement in a Mixed-Three-Spin Ising-$XY$ Model with Added Dzyaloshinskii–Moriya Interaction under Decoherence

H. A. Zad
Chin. Phys. Lett. 2016, 33 (09): 090302 doi: 10.1088/0256-307X/33/9/090302
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We investigate the behavior of geometric global quantum discord (GGQD) and concurrence (C) between half-spins of a mixed-three-spin (1/2, 1, 1/2) system with the Ising-$XY$ model for which spins (1, 1/2) have the Ising interaction and half-spins (1/2, 1/2) have both $XY$ and the Dzyaloshinskii–Moriya interactions together, under the decoherence action. A single-ion anisotropy property with coefficient $\zeta$ is assumed for the spin-integer. This system which includes an analytical Hamiltonian is considered at the front of an external homogeneous magnetic field $B$ in thermal equilibrium. Finally, we compare GGQD and C and express some interesting phase flip reactions of the total quantum correlation and pairwise entanglement between spins (1/2, 1/2). Generally, we conclude that the concurrence and GGQD have different behaviors under the phase flip channel.

Measurement-Device-Independent Quantum Key Distribution with Two-Way Local Operations and Classical Communications

Yong-Gang Tan, Qiang Liu
Chin. Phys. Lett. 2016, 33 (09): 090303 doi: 10.1088/0256-307X/33/9/090303
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Measurement-device-independent quantum key distribution (MDI-QKD) is proven to be immune to all the detector side channel attacks. With two symmetric quantum channels, the maximal transmission distance can be doubled when compared with the prepare-and-measure QKD. An interesting question is whether the transmission distance can be extended further. In this work, we consider the contributions of the two-way local operations and classical communications to the key generation rate and transmission distance of the MDI-QKD. Our numerical results show that the secure transmission distances are increased by about 12 km and 8 km when the 1 B and the 2 B steps are implemented, respectively.

Hybrid of Quantum Phases for Induced Dipole Moments

Kai Ma
Chin. Phys. Lett. 2016, 33 (09): 090304 doi: 10.1088/0256-307X/33/9/090304
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The quantum phase effects for induced electric and magnetic dipole moments are investigated. It is shown that the phase shift received by the induced electric dipole has the same form as the one induced by magnetic dipole moment, therefore the total phase is a hybrid of these two types of phase. This feature indicates that to have a decisive measurement on either one of these two phases, it is necessary to measure the velocity dependence of the observed phase.

Uncertainty Quantification of Numerical Simulation of Flows around a Cylinder Using Non-intrusive Polynomial Chaos

Yan-Jin Wang, Shu-Dao Zhang
Chin. Phys. Lett. 2016, 33 (09): 090501 doi: 10.1088/0256-307X/33/9/090501
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The uncertainty quantification of flows around a cylinder is studied by the non-intrusive polynomial chaos method. Based on the validation with benchmark results, discussions are mainly focused on the statistic properties of the peak lift and drag coefficients and base pressure drop over the cylinder with the uncertainties of viscosity coefficient and inflow boundary velocity. As for the numerical results of flows around a cylinder, influence of the inflow boundary velocity uncertainty is larger than that of viscosity. The results indeed demonstrate that a five-order degree of polynomial chaos expansion is enough to represent the solution of flow in this study.

An Open Rectangular Waveguide Grating for Millimeter-Wave Traveling-Wave Tubes

Ming-Liang Liao, Yan-Yu Wei, Hai-Long Wang, Yu Huang, Jin Xu, Yang Liu, Guo Guo, Xin-Jian Niu, Yu-Bin Gong, Gun-Sik Park
Chin. Phys. Lett. 2016, 33 (09): 090701 doi: 10.1088/0256-307X/33/9/090701
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Millimeter-wave traveling-wave tube (TWT) prevails nowadays as the amplifier for radar, communication and electronic countermeasures. The rectangular waveguide grating is a promising all-metal interaction circuit for the millimeter-wave TWT with advantages of high power capacity, fine heat dissipation, scalability to smaller dimensions for shorter wavelengths, compact structure and robust performance. Compared with the traditional closed structure, the open rectangular waveguide grating (ORWG) has wider bandwidth, lower cut-off frequency, and higher machining precision for higher working frequencies due to the open transverse. It is a potential structure that can work in the millimeter wave and even Terahertz band. The rf characteristics including dispersion and interaction impedance are investigated by both theoretic calculation and software simulation. The influences of the structure parameters are also discussed and compared, and the theoretical results agree well with the simulation results. Based on the study, the ORWG will favor the design of a broadband and high-power millimeter-wave TWT.

Solution for Energies and Mixing of Two 0$^{+}$ States in $^{10}$He

H. T. Fortune
Chin. Phys. Lett. 2016, 33 (09): 092101 doi: 10.1088/0256-307X/33/9/092101
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Using results from various reactions that populate $^{10}$He, I conclude that the ground state has $E_{2n}=1.07(7)$ MeV and the excited 0$^{+}$ state is in the region of 2.1–3.1 MeV. The amount of the $(sd)^{2}$ component in the ground state is less than about 0.075.

Nonadiabatic Effect on the Rescattering Trajectories of Electrons in Strong Laser Field Ionization Process

Xin-Hai Tu, Xiao-Lei Hao, Wei-Dong Li, Shi-Lin Hu, Jing Chen
Chin. Phys. Lett. 2016, 33 (09): 093201 doi: 10.1088/0256-307X/33/9/093201
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The important features of the rescattering trajectories in strong field ionization process such as the cutoff of the return energy at $3.17 U_{\rm p}$ and that of the final energy at $10 U_{\rm p}$ are obtained, based on the adiabatic approximation in which the initial momentum of the electron is assumed to be zero. We theoretically study the nonadiabatic effect by assuming a nonzero initial momentum on the rescattering trajectories based on the semiclassical simpleman model. We show that the nonzero initial momentum will modify both the maximal return energy at collision and the final energy after backward scattering, but in different ways for odd and even number of return trajectories. The energies are increased for even number of returns but are decreased for odd number of returns when the nonzero (positive or negative) initial momentum is applied.

Investigation of Compton Profile of Molecular Propane

Xiao-Xun Mei, Xiao-Li Zhao, Long-Quan Xu, Ya-Wei Liu, Xu Kang, Shuai Yan, Dong-Dong Ni, Ke Yang, Lin-Fan Zhu
Chin. Phys. Lett. 2016, 33 (09): 093301 doi: 10.1088/0256-307X/33/9/093301
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The experimental Compton profile of the propane molecule is measured at an incident photon energy of 20 keV based on the third generation synchrotron radiation, and the statistical accuracy of 0.2% is achieved near $p_{z}=0$. The calculated Compton profile by the density functional theory with aug-cc-pVTZ basis set reproduces the experimental observation very well. The joint experimental and theoretical investigation provides the benchmark data of the electronic structure of propane.

A New Simulation of Track Structure of Low-Energy Electrons in Liquid Water: Considering the Condensed-Phase Effect on Electron Elastic Scattering

Wei Liu, Zhen-Yu Tan, C. Champion
Chin. Phys. Lett. 2016, 33 (09): 093401 doi: 10.1088/0256-307X/33/9/093401
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A new Monte Carlo simulation of the track structure of low-energy electrons ($ < $10 keV) in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid water on electron elastic scattering with the use of the Champion model, while the dielectric response formalism incorporating the optical-data model developed by Emfietzoglou et al. is applied for calculating the electron inelastic scattering. The spatial distributions of energy deposition and inelastic scattering events of low-energy electrons with different primary energies in liquid water are calculated and compared with other theoretical evaluations. The present work shows that the condensed-phase effect of liquid water on electron elastic scattering may be of the influence on the fraction of absorbed energy and distribution of inelastic scattering events at lower primary energies, which also indicate potential effects on the DNA damage induced by low-energy electrons.

Silicon-on-Insulator-Based Broadband 1$\times$3 Adiabatic Splitter with Simultaneous Tapering of Velocity and Coupling

Yuan-Hao Gong, Zhi-Yong Li, Jin-Zhong Yu, Yu-De Yu
Chin. Phys. Lett. 2016, 33 (09): 094201 doi: 10.1088/0256-307X/33/9/094201
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We propose and experimentally demonstrate a broadband $1\times3$ adiabatic splitter based on the silicon-on-insulator technology, with simultaneous tapering of velocity and coupling. The designed structure becomes simulated transmission uniformity of three outputs better than 0.5 dB in a broadband of 250 nm, and a large simulated fabrication tolerance is obtained. A manufactured splitter whose parameters greatly diverge from the design acquires a measured result of the worst splitting ratio better than 1.5 dB as well as an excess loss lower than 0.8 dB in a large wavelength range of 80 nm. A post-simulation based on the tested splitter obtains a result that meets the actual transmission well.

Pulse Propagation with Self-Phase Modulation in Nonlinear Chiral Fiber and Its Applications

Demissie Gelmecha, Jun-Qing Li Merhawit Teklu
Chin. Phys. Lett. 2016, 33 (09): 094202 doi: 10.1088/0256-307X/33/9/094202
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From Maxwell's equations and Post's formalism, a generalized chiral nonlinear Schrödinger equation (CNLSE) is obtained for the nonlinear chiral fiber. This equation governs light transmission through a dispersive nonlinear chiral fiber with joint action of chirality in linear and nonlinear ways. The generalized CNLSE shows a modulation of chirality to the effect of attenuation and nonlinearity compared with the case for a conventional fiber. Simulations based on the split-step beam propagation method reveal the role of nonlinearity with cooperation to chirality playing in the pulse evolution. By adjusting its strength the role of chirality in forming solitons is demonstrated for a given circularly polarized component. The application of nonlinear optical rotation is also discussed in an all-optical switch.

Creation of Multiple Subwavelength Focal Spot Segments Using Phase Modulated Radially Polarized Multi Gaussian Beam

K. Prabakaran, K. B. Rajesh, S. Sumathira, M. D. Bharathi, R. Hemamalini, A. M. Musthafa, V. Aroulmoji
Chin. Phys. Lett. 2016, 33 (09): 094203 doi: 10.1088/0256-307X/33/9/094203
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Based on the vector diffraction theory, the effect of complex phase filters on intensity distribution of a radially polarized multi Gaussian beam in the focal region of high NA lens is theoretically investigated. It is observed that a properly designed multi belt complex phase filter can generate subwavelength novel focal patterns including splitting of focal spots and generation of multiple focal spot segments such as eight, six and four focal spots along the optical axis are obtained. We expect that such an investigation is useful for optical manipulation and material processing, multiple high refractive index particle trapping technologies.

Passively Mode-Locked Femtosecond Laser with Disordered Crystal Nd:CGA as Gain Medium

Kun-Na He, Jia-Xing Liu, Wen-Long Tian, Zhong-Wei Shen, Xiao-Dong Xu, Zhao-Hua Wang, De-Hua Li, Jun Xu, Ju-Qing Di, Chang-Tai Xia, Zhi-Yi Wei
Chin. Phys. Lett. 2016, 33 (09): 094204 doi: 10.1088/0256-307X/33/9/094204
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We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd:CaGdAlO$_{4}$ (Nd:CGA) as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser pulses as short as 850 fs at 1079 nm are obtained with a repetition rate of 124.6 MHz. The measured threshold pump power is 1.45 W. A maximum average output power of 122 mW is obtained under the pump power of 5.9 W. These results show that Nd:CGA could be a promising laser medium for generating femtosecond ultrashort pulse at about 1 µm.

Simulation and Design of Fluorescence Collector

Hao Shi, Jie Ma, Xiao-Feng Li, Jie Liu, Shou-Gang Zhang
Chin. Phys. Lett. 2016, 33 (09): 094205 doi: 10.1088/0256-307X/33/9/094205
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Fluorescence collector is a critical component in optically pumped Cs beam frequency standards. We design a new fluorescence collector by means of a new method. By means of two simulation methods, a smaller fluorescence collector with the same collection efficiency is achieved. It can be applied to almost all fluorescence detection systems in atom-light interaction experiments. We select the practical fluorescence collector studied by comparing three designing schemes. Its structure is very plain. Moreover, its fluorescence collection efficiency is very high. The collection efficiency of the practical fluorescence collector we designed is over 33% by means of two different ways.

Wavelength-Tunable Rectangular Pulses Generated from All-Fiber Mode-Locked Laser Based on Semiconductor Saturable Absorber Mirror

Zhao-Kun Wang, Feng Zou, Zi-Wei Wang, Song-Tao Du, Jun Zhou
Chin. Phys. Lett. 2016, 33 (09): 094206 doi: 10.1088/0256-307X/33/9/094206
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The wavelength-tunable rectangular mode-locking operation is demonstrated in an all-fiber laser based on semiconductor saturable absorber mirror. As the dissipative soliton resonance signature, the pulse duration varies from 580 ps to 2.1 ns as a function of the increasing pump power. Correspondingly, the maximum pulse energy is 9.11 nJ. Moreover, it is found that the wavelength tunable operation with a range of approximately 10 nm could be obtained by properly adjusting the polarization controllers. The characteristics of the rectangular pulses at different wavelengths are similar to each other. The demonstration of the wavelength tunable rectangular pulses would be beneficial to some applications for many fields such as spectroscopy and sensing research.

Spectrum-Splitting Diffractive Optical Element of High Concentration Factor and High Optical Efficiency for Three-Junction Photovoltaics

Dong-Feng Lin, Bao-Gang Quan, Qiu-Lin Zhang, Dong-Xiang Zhang, Xin Xu, Jia-Sheng Ye, Yan Zhang, Dong-Mei Li, Qing-Bo Meng, Li Pan, Guo-Zhen Yang
Chin. Phys. Lett. 2016, 33 (09): 094207 doi: 10.1088/0256-307X/33/9/094207
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A spectrum-splitting and beam-concentrating (SSBC) diffractive optical element (DOE) for three-junction photovoltaics (PV) system is designed and fabricated by five-circle micro-fabrication. The incident solar light is efficiently split into three sub-spectrum ranges and strongly concentrated on the focal plane, which can be directly utilized by suitable spectrum-matching solar cells. The system concentration factor reaches 12$\times$. Moreover, the designed wavelengths (450 nm, 550 nm and 650 nm) are spatially distributed on the focal plane, in good agreement with the theoretical results. The average optical efficiency of all the cells over the three designed wavelengths is 60.07%. The SSBC DOE with a high concentration factor and a high optical efficiency provides a cost-effective approach to achieve higher PV conversion efficiencies.

Optimization Design of Electromagnetic Nihility Nanoparticles

Ya-Ming Xie, Chang-Yu Liu, Ze-Jun Ding, Zhi-Guo Wang
Chin. Phys. Lett. 2016, 33 (09): 094208 doi: 10.1088/0256-307X/33/9/094208
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Nihility material is a medium whose relative permittivity and permeability tend to zero simultaneously. In this work, comparing with the scattering properties of perfect nihility nanoparticles (made from nihility material), we provide an optimization design of electromagnetic nihility nanoparticles, which is a coated hybrid nanosphere constituted by commutative $\varepsilon$-negative (ENG) and $\mu$-negative (MNG) media. Compared to a single ENG or MNG nanosphere, it is found that the total and back scattering spectra of coated hybrid nanospheres are much closer to those of perfect nihility nanospheres. Moreover, it is observed that the scattered electromagnetic field distribution of coated hybrid nanospheres is identical to that of perfect nihility nanospheres. These results indicate that the combination of commutative ENG and MNG media can constitute a composite structure which gives the closest approximation of electromagnetic scattering of perfect nihility nanospheres in a wide frequency range.

Structure and Tribological Property of TiBN Nanocomposite Multilayer Synthesized by Ti-BN Composite Cathode Plasma Immersion Ion Implantation and Deposition

Wen-Quan Lv, Lang-Ping Wang, Yong-Zhi Cao, Zhi-Wei Gu, Xiao-Feng Wang, Yong-Da Yan, Fu-Li Yu
Chin. Phys. Lett. 2016, 33 (09): 095201 doi: 10.1088/0256-307X/33/9/095201
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A Ti-BN complex cathode is made from Ti and h-BN powders by the powder metallurgy technology, and TiBN coating is obtained by plasma immersion ion implantation and deposition with this Ti-BN composite cathode. The TiBN coating shows a self-forming multilayered nanocomposite structure while with relative uniform elemental distributions. High resolution transmission electron microscopy images reveal that the multilayered structure is derived from different grain sizes in the nanocomposite. Due to the existence of h-BN phase, the friction coefficient of the coating is about 0.25.

Laser Wakefield Acceleration Using Mid-Infrared Laser Pulses

Guo-Bo Zhang, N. A. M. Hafz, Yan-Yun Ma, Lie-Jia Qian, Fu-Qiu Shao, Zheng-Ming Sheng
Chin. Phys. Lett. 2016, 33 (09): 095202 doi: 10.1088/0256-307X/33/9/095202
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We study a laser wakefield acceleration driven by mid-infrared (mid-IR) laser pulses through two-dimensional particle-in-cell simulations. Since a mid-IR laser pulse can deliver a larger ponderomotive force as compared with the usual 0.8 µm wavelength laser pulse, it is found that electron self-injection into the wake wave occurs at an earlier time, the plasma density threshold for injection becomes lower, and the electron beam charge is substantially enhanced. Meanwhile, our study also shows that quasimonoenergetic electron beams with a narrow energy-spread can be generated by using mid-IR laser pulses. Such a mid-IR laser pulse can provide a feasible method for obtaining a high quality and high charge electron beam. Therefore, the current efforts on constructing mid-IR terawatt laser systems can greatly benefit the laser wakefield acceleration research.

New Method of Total Ionizing Dose Compact Modeling in Partially Depleted Silicon-on-Insulator MOSFETs

Jian-Qiang Huang, Wei-Wei He, Jing Chen, Jie-Xin Luo, Kai Lu, Zhan Chai
Chin. Phys. Lett. 2016, 33 (09): 096101 doi: 10.1088/0256-307X/33/9/096101
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On the basis of a detailed discussion of the development of total ionizing dose (TID) effect model, a new commercial-model-independent TID modeling approach for partially depleted silicon-on-insulator metal-oxide-semiconductor field effect transistors is developed. An exponential approximation is proposed to simplify the trap charge calculation. Irradiation experiments with $^{60}$Co gamma rays for IO and core devices are performed to validate the simulation results. An excellent agreement of measurement with the simulation results is observed.

Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

Dong Wang, Ning Gao, W. Setyawan, R. J. Kurtz, Zhi-Guang Wang, Xing Gao, Wen-Hao He, Li-Long Pang
Chin. Phys. Lett. 2016, 33 (09): 096102 doi: 10.1088/0256-307X/33/9/096102
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The influence of strain field on defect formation energy and threshold displacement energy ($E_{\rm d})$ in body-centered cubic tungsten (W) is studied with molecular dynamics simulation. Two different W potentials (Fikar and Juslin) are compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affect the threshold displacement energy and its direction-specific values. The minimum $E_{\rm d}$ direction calculated with the Fikar potential is $\langle100\rangle$ and with the Juslin potential is $\langle111\rangle$. Nevertheless, the most stable self-interstitial configuration is found to be a $\langle111\rangle$-crowdion for both the potentials. This stable configuration does not change with the applied strain. Varying the strain from compression to tension increases the vacancy formation energy while decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that $E_{\rm d}$ decreases with the applied hydrostatic strain from compression to tension.

Highly Efficient Power Conversion from Salinity Gradients with Ion-Selective Polymeric Nanopores

Yun Ling, Dong-Xiao Yan, Peng-Fei Wang, Mao Wang, Qi Wen, Feng Liu, Yu-Gang Wang
Chin. Phys. Lett. 2016, 33 (09): 096103 doi: 10.1088/0256-307X/33/9/096103
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A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion efficiency and power density are often limited due to the challenge in reliably controlling the size of the nanopores with the conventional chemical etching method. Here we report that without chemical etching, polyimide (PI) membranes irradiated with GeV heavy ions have negatively charged nanopores, showing nearly perfect selectivity for cations over anions, and they can generate electrical power from salinity gradients. We further demonstrate that the power generation efficiency of the PI membrane approaches the theoretical limit, and the maximum power density reaches 130 mW/m$^{2}$ with a modified etching method, outperforming the previous energy conversion device that was made of polymeric nanopore membranes.

Structural Phase Transitions of ZnTe under High Pressure Using Experiments and Calculations

Hu Cheng, Yan-Chun Li, Gong Li, Xiao-Dong Li
Chin. Phys. Lett. 2016, 33 (09): 096104 doi: 10.1088/0256-307X/33/9/096104
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The pressure-induced structural transitions of ZnTe are investigated at pressures up to 59.2 GPa in a diamond anvil cell by using synchrotron powder x-ray diffraction method. A phase transition from the initial zinc blende (ZB, ZnTe-I) structure to a cinnabar phase (ZnTe-II) is observed at 9.6 GPa, followed by a high pressure orthorhombic phase (ZnTe-III) with $Cmcm$ symmetry at 12.1 GPa. The ZB, cinnabar (space group $P3_{1}21$), $Cmcm$, $P3_{1}$ and rock salt structures of ZnTe are investigated by using density functional theory calculations. Based on the experiments and calculations, the ZnTe-II phase is determined to have a cinnabar structure rather than a $P3_{1}$ symmetry.

Strain Avalanches in Microsized Single Crystals: A Theoretical Study of the Relation between the Avalanche Size and Duration

Xu Zhang, Zhi Wang, Qian Li, Fu-Lin Shang
Chin. Phys. Lett. 2016, 33 (09): 096401 doi: 10.1088/0256-307X/33/9/096401
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Single crystal micropillars deform via a sequence of discrete strain avalanches, observed as displacement jumps or stress drops. Here we develop a simple crystal plasticity model to provide a quantitative expression of the relation between avalanche duration and avalanche size. It is found that the avalanche durations in scale with the averaged avalanche sizes only hold for those larger magnitudes. We show that the theoretical predictions are capable of capturing the essential aspects of scaling behaviors from micro-compression tests.

A Lateral Regulator Diode with Field Plates for Light-Emitting-Diode Lighting

Yi-Tao He, Ming Qiao, Lu Li, Gang Dai, Bo Zhang, Zhao-Ji Li
Chin. Phys. Lett. 2016, 33 (09): 097101 doi: 10.1088/0256-307X/33/9/097101
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A lateral current regulator diode (CRD) with field plates is proposed and experimentally demonstrated. The proposed CRD is based on the junction field-effect transistor (JFET) structure. A cathode field plate is adopted to alleviate the channel-length modulation effect and to improve the saturated $I$–$V$ characteristics. An anode field plate is induced to achieve a high breakdown voltage $V_{\rm B}$ of the CRD. The influence of the key device parameters on the $I$–$V$ characteristics of the lateral CRD are discussed. Experimental results show that the proposed CRD presents good $I$–$V$ characteristics with a high $V_{\rm B}$ about 180 V and a low knee voltage ($V_{\rm k})$ below 3 V. Furthermore, the proposed CRD has a negative temperature coefficient. The well characteristic of the proposed CRD makes it a cost-effective solution for light-emitting-diode lighting.

Electronic and Magnetic Properties of Co- and Mn-codoped ZnO by Density Functional Theory

A. Stashans, K. Rivera
Chin. Phys. Lett. 2016, 33 (09): 097102 doi: 10.1088/0256-307X/33/9/097102
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Zinc oxide crystal containing intrinsic oxygen vacancy defect as well as codoped with Mn and Co impurities is studied using density functional theory (DFT) calculations. An intra-atomic interaction term for the strongly correlated $d$-electrons by an unrestricted Hartree–Fock approximation (DFT+$U$ method) is introduced to more precisely describe the system under study. The electronic and magnetic properties are investigated and discussed in detail. In particular, it is found that relative defect positions might influence the outcome if the material exhibits or not the n-type electrical conductivity.

Experimental Observation of Phase Transition in Sb$_{2}$O$_{3}$ under High Pressure

Ai-Hui Geng, Li-Hua Cao, Yan-Mei Ma, Qi-Liang Cui, Chun-Ming Wan
Chin. Phys. Lett. 2016, 33 (09): 097401 doi: 10.1088/0256-307X/33/9/097401
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The in situ high-pressure behavior of the semiconductor antimony trioxide (Sb$_{2}$O$_{3})$ is investigated by the Raman spectroscopy techniques and angle-dispersive synchrotron x-ray powder diffraction in a diamond anvil cell up to 31.5 and 30.7 GPa, respectively. New peaks observed in the external lattice mode range in the Raman spectra at 13.5 GPa suggest that the structural phase transition occurs. The group mode (140 cm$^{-1}$) in Sb$_{2}$O$_{3}$ exhibits anomalous pressure dependence; that is, the frequency decreases gradually with the increasing pressure. High pressure synchrotron x-ray diffraction measurements at room temperature reveal that the transition from the orthorhombic structure to high-pressure new phase occurs at about 14.2 GPa, corresponding to the softening of the group optic mode (140 cm$^{-1}$).

Synthesis of Ordered Ultra-long Manganite Nanowires via Electrospinning Method

Jun Zheng, Kai Du, Di Xiao, Zheng-Yang Zhou, Wen-Gang Wei, Jin-Jie Chen, Li-Feng Yin, Jian Shen
Chin. Phys. Lett. 2016, 33 (09): 097501 doi: 10.1088/0256-307X/33/9/097501
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We develop a new electrospinning method to prepare ultra-long ordered La$_{1-x}$Sr$_{x}$MnO$_{3}$ (LSMO) nanowires. The length is up to several centimeters and is only limited by the size of the collector. The well-ordered straight-line structure ensures the transport measurement, which is impossible to be carried out for the random nanowires fabricated by the traditional electrospinning method. Magnetic and transport measurements indicate that the physical properties of the LSMO nanowires depend sensitively on the doping concentration. At the optimum doping, the LSMO wires are ferromagnetic at room temperature with a metal-insulator transition temperature close to room temperature. Magnetic force microscopy studies are also performed to provide a microscopic view of these ultra-long nanowires.

Effect of In$_{x}$Ga$_{1-x}$As Interlayer on Surface Morphology and Optical Properties of GaSb/InGaAs Type-II Quantum Dots Grown on InP (100) Substrates

Yu-Long Chen, You Gao, Hong Chen, Hui Zhang, Miao He, Shu-Ti Li, Shu-Wen Zheng
Chin. Phys. Lett. 2016, 33 (09): 098101 doi: 10.1088/0256-307X/33/9/098101
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The effects of indium composition in InGaAs interlayer on morphology of GaSb/InGaAs quantum dots (QDs) and on optical properties of GaSb/InGaAs QD material system are studied. AFM images show that the change of the indium composition in InGaAs interlayer can alter the GaSb QD morphology. It is found that low indium composition in InGaAs interlayer can promote the formation of QDs, while high indium composition can inhibit the formation of QDs. The photoluminescence (PL) spectra of GaSb/InGaAs QDs at 8 K under low excitation power indicate that the third root of the excitation power is linear with the peak position, which provides a direct evidence for their luminescence belonging to type-II material optical transition. The PL spectra at 8 K under an excitation power of 90 mW show that the optical properties of GaSb/InGaAs QD material system can be affected by the indium composition in the InGaAs interlayer, and the PL peak position is linear with the indium composition. The optical properties of GaSb/InGaAs QDs can be improved by adjusting the indium composition in the InGaAs interlayer.

Excellent-Performance AlGaN/GaN Fin-MOSHEMTs with Self-Aligned Al$_{2}$O$_{3}$ Gate Dielectric

Xin Tan, Xing-Ye Zhou, Hong-Yu Guo, Guo-Dong Gu, Yuan-Gang Wang, Xu-Bo Song, Jia-Yun Yin, Yuan-Jie Lv, Zhi-Hong Feng
Chin. Phys. Lett. 2016, 33 (09): 098501 doi: 10.1088/0256-307X/33/9/098501
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AlGaN/GaN fin-shaped metal-oxide-semiconductor high-electron-mobility transistors (fin-MOSHEMTs) with different fin widths (300 nm and 100 nm) on sapphire substrates are fabricated and characterized. High-quality self-aligned Al$_{2}$O$_{3}$ gate dielectric underneath an 80-nm T-shaped gate is employed by aluminum self-oxidation, which induces 4 orders of magnitude reduction in the gate leakage current. Compared with conventional planar MOSHEMTs, short channel effects of the fabricated fin-MOSHEMTs are significantly suppressed due to the tri-gate structure, and excellent dc characteristics are obtained, such as extremely flat output curves, smaller drain induced barrier lower, smaller subthreshold swing, more positive threshold voltage, higher transconductance and higher breakdown voltage.

Three-Dimensional Simulations of RESET Operation in Phase-Change Random Access Memory with Blade-Type Like Phase Change Layer by Finite Element Modeling

Qiu-Xue Jin, Bo Liu, Yan Liu, Wei-Wei Wang, Heng Wang, Zhen Xu, Dan Gao, Qing Wang, Yang-Yang Xia, Zhi-Tang Song, Song-Lin Feng
Chin. Phys. Lett. 2016, 33 (09): 098502 doi: 10.1088/0256-307X/33/9/098502
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An optimized device structure for reducing the RESET current of phase-change random access memory (PCRAM) with blade-type like (BTL) phase change layer is proposed. The electrical thermal analysis of the BTL cell and the blade heater contactor structure by three-dimensional finite element modeling are compared with each other during RESET operation. The simulation results show that the programming region of the phase change layer in the BTL cell is much smaller, and thermal electrical distributions of the BTL cell are more concentrated on the TiN/GST interface. The results indicate that the BTL cell has the superiorities of increasing the heating efficiency, decreasing the power consumption and reducing the RESET current from 0.67 mA to 0.32 mA. Therefore, the BTL cell will be appropriate for high performance PCRAM device with lower power consumption and lower RESET current.

Effects of Tensor Couplings on Nucleonic Direct URCA Processes in Neutron Star Matter

Yan Xu, Xiu-Lin Huang, Cheng-Zhi Liu, Tmurbagan Bao, Guang-Zhou Liu
Chin. Phys. Lett. 2016, 33 (09): 099701 doi: 10.1088/0256-307X/33/9/099701
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The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree–Fock approximation. We particularly study the influences of the tensor couplings of vector mesons $\omega$ and $\rho$ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons $\omega$ and $\rho$ can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons $\omega$ and $\rho$ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non-superfluid neutron star matter. However, when considering only the tensor coupling of vector meson $\rho$, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson $\rho$ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.

The Pulsation Induced by Mass Transfer in Critically Rotating Stars

Jiang-Tao Wang, Han-Feng Song
Chin. Phys. Lett. 2016, 33 (09): 099702 doi: 10.1088/0256-307X/33/9/099702
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The structural characteristics of the critically rotating accretor in binaries are investigated during rapid mass transfer. It is found that the accretor is subjected to periodic pulsation due to accretions and rejections of mass and angular momentum. The gainer attempts to attain both hydrostatic and thermal balances. This physical process can cause the thermal structure of the accreting star to fluctuate with a period of $\sim0.19$ y. Stellar wind can be enhanced by a factor of $\sim $$1.25$$\,\times\,$$10^{4}$ when the accretor approaches break-down velocity. Surface entropy and density decrease with the increase of the stellar radius due to the fact that rapid rotation leads to a reduction in the number density and surface temperature. The rotational energy has the same trend as stellar radius due to stellar expansion. Surface opacity which is extremely sensitive to surface temperature has an opposite trend to stellar radius. Moreover, the rate of nuclear energy must be adjusted due to mass removal or accretion at the stellar surface.
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