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Volume 28 Issue 10
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GENERAL
Semiquantum Key Distribution Using Entangled States
WANG Jian, ZHANG Sheng, ZHANG Quan, TANG Chao-Jing
Chin. Phys. Lett. 2011, 28 (10): 100301 .   DOI: 10.1088/0256-307X/28/10/100301
Abstract   PDF(pc) (394KB) ( 635 )
Recently, Boyer et al. presented a novel semiquantum key distribution protocol [Phys. Rev. Lett. 99 (2007) 140501] by using four quantum states, each of which is randomly prepared in the Z or X basis. Here we present a semiquantum key distribution protocol by using maximally entangled states in which quantum Alice shares a secret key with classical Bob. Quantum Alice has the ability to prepare Bell states and perform Bell basis or computational basis measurement. Classical Bob is restricted to measuring, preparing a particle in the computational basis, reflecting or reordering the particles. The qubit efficiency of the protocol improves to 50% and the protocol can be modified to a measure-resend protocol or a protocol without quantum memory. We also show that the protocol is secure against eavesdropping.
Disorder Induced Dynamic Equilibrium Localization and Random Phase Steps of Bose–Einstein Condensates
DUAN Ya-Fan, XU Zhen, QIAN Jun, SUN Jian-Fang, JIANG Bo-Nan, HONG Tao**
Chin. Phys. Lett. 2011, 28 (10): 100302 .   DOI: 10.1088/0256-307X/28/10/100302
Abstract   PDF(pc) (785KB) ( 407 )
We numerically analyze the dynamic behavior of Bose–Einstein condensate (BEC) in a one-dimensional disordered potential before it completely loses spatial quantum coherence. We find that both the disorder statistics and the atom interactions produce remarkable effects on localization. We also find that the single phase of the initial condensate is broken into many small pieces while the system approaches localization, showing a counter-intuitive step-wise phase but not a thoroughly randomized phase. Although the condensates as a whole show less flow and expansion, the currents between adjacent phase steps retain strong time dependence. Thus we show explicitly that the localization of a finite size Bose–Einstein condensate is a dynamic equilibrium state.
Area Spectra of Schwarzschild-Anti de Sitter Black Holes from Highly Real Quasinormal Modes
GUO Guang-Hai**, DING Xia
Chin. Phys. Lett. 2011, 28 (10): 100401 .   DOI: 10.1088/0256-307X/28/10/100401
Abstract   PDF(pc) (387KB) ( 425 )
Motivated by the new physical interpretation of quasinormal modes proposed by Maggiore [Phys. Rev. Lett. 100 (2008) 141301], we investigate the quantization of large Schwarzschild-Anti de Sitter black holes in even-dimensional spacetimes, from the interesting highly real quasinormal modes found recently. Following Maggiore's treatment and Kunstatter's method, we derive the area and entropy spectra of the black holes. It is found that the results from both approaches are in full consistency. This implies that one can quantize a black hole via different asymptotic quasinormal modes besides the high damping ones that are usually adopted in the literature. Furthermore, we find that the area and entropy spectra are equidistant and independent of the cosmological constant. However, the spacings depend on the black hole dimension.
Modulational Instability for Gravitoelectromagnetic Perturbations with Longitudinal and Transverse Modes
YANG Xiao-Song, LIU San-Qiu, **, LI Xiao-Qing,
Chin. Phys. Lett. 2011, 28 (10): 100402 .   DOI: 10.1088/0256-307X/28/10/100402
Abstract   PDF(pc) (520KB) ( 357 )
The modulational instability for longitudinal and transverse gravitoelectromagnetic (GEM) perturbations is investigated on the basis of the self-generated gravitomagnetic field equations in a self-gravitating system. Analytical results indicate that the instability may lead the initially uniformly distributed matter collapse into a small region where the density of matter and the quasi-static self-generated gravitomagnetic field are strongly enhanced. There will be a pancake-like structure because the characteristic scale of longitudinal perturbation is much larger than the transverse one. The anisotropic accumulation of matter and the generation of a gravitomagnetic field are in favor of the formation of a rotationally pancake-like structure.
Thermodynamic Properties of a Reissner–Nordström Quintessence Black Hole
WEI Yi-Huan**, CHU Zhong-Hui
Chin. Phys. Lett. 2011, 28 (10): 100403 .   DOI: 10.1088/0256-307X/28/10/100403
Abstract   PDF(pc) (406KB) ( 470 )
The first law of thermodynamics for the three horizons of Reissner–Nordström quintessence (RNQ) spacetime is obtained. For a general process of RNQ spacetime, the expressions for the radius changes of the three horizons are derived. When only mass changes, the heat fluxes through the three horizons are equivalent and no heat is left in the black hole region. Finally, a further discussion on the thermal properties of an RNQ black hole is given.
Robustness of Diversity Induced Synchronization Transition in a Delayed Small-World Neuronal Network
TANG Jun**, QU Li-Cheng, LUO Jin-Ming
Chin. Phys. Lett. 2011, 28 (10): 100501 .   DOI: 10.1088/0256-307X/28/10/100501
Abstract   PDF(pc) (1090KB) ( 464 )
In a diverse and delayed small-world neuronal network, we have identified the oscillatory-like synchronization transition between anti-phase and complete synchronization [Phys. Rev. E 83 (2011) 046207]. Here we study the influence of the network topology and noise on the synchronization transition. The robustness of this transition is investigated. The results show that: (i) the synchronization transition is robust to the neuron number N in the network; (ii) only when the coupled neighbor number k is in the region [4,10], does the synchronization transition exist; (iii) to some extent, the synchronization is destroyed by noise and the oscillatory−like synchronization transition exists for relatively weak noise (D<0.003).
A Neurodynamical Model for Selective Visual Attention
QU Jing-Yi**, WANG Ru-Bin, ZHANG Yuan, DU Ying
Chin. Phys. Lett. 2011, 28 (10): 100502 .   DOI: 10.1088/0256-307X/28/10/100502
Abstract   PDF(pc) (498KB) ( 373 )
A neurodynamical model for selective visual attention considering orientation preference is proposed. Since orientation preference is one of the most important properties of neurons in the primary visual cortex, it should be fully considered besides external stimuli intensity. By tuning the parameter of orientation preference, the regimes of synchronous dynamics associated with the development of the attention focus are studied. The attention focus is represented by those peripheral neurons that generate spikes synchronously with the central neuron while the activity of other peripheral neurons is suppressed. Such dynamics correspond to the partial synchronization mode. Simulation results show that the model can sequentially select objects with different orientation preferences and has a reliable shift of attention from one object to another, which are consistent with the experimental results that neurons with different orientation preferences are laid out in pinwheel patterns.
Phonon and Elastic Instabilities in Zincblende TlN under Hydrostatic Pressure from First Principles Calculations
SHI Li-Wei, **, DUAN Yi-Feng, YANG Xian-Qing, TANG Gang
Chin. Phys. Lett. 2011, 28 (10): 100503 .   DOI: 10.1088/0256-307X/28/10/100503
Abstract   PDF(pc) (649KB) ( 826 )
The lattice dynamic and elastic instabilities of zincblende (ZB) thallium nitride (TlN) under hydrostatic pressure are extensively studied to reveal the physically driven mechanism of phase transition from the ZB to a rocksalt structure using pseudopotential plane-wave density functional calculations within the local density approximation. Our calculated results shows that both transverse acoustic phonon mode softening behavior and elastic instability are responsible for the pressure-induced structural phase transition in ZB TlN.
The IOSS Chaos Synchronization Method
Choon Ki Ahn*
Chin. Phys. Lett. 2011, 28 (10): 100504 .   DOI: 10.1088/0256-307X/28/10/100504
Abstract   PDF(pc) (443KB) ( 360 )
A new synchronization method, called the input/output-to-state stable synchronization (IOSSS) method, is proposed for a general class of chaotic systems with external disturbance. By introducing Lyapunov stability theory and linear matrix inequality (LMI) for the first time, the IOSSS controller is shown to not only guarantee the synchronization of the chaotic systems, but also reduce the effect of external disturbance. The proposed IOSSS controller can be obtained by solving the LMI, which can easily be done using standard numerical packages. A numerical example is given to demonstrate the availability of the proposed method.
Spiral Wave Generation in a Vortex Electric Field
YUAN Xiao-Ping, CHEN Jiang-Xing, ZHAO Ye-Hua**, LOU Qin, WANG Lu-Lu, SHEN Qian
Chin. Phys. Lett. 2011, 28 (10): 100505 .   DOI: 10.1088/0256-307X/28/10/100505
Abstract   PDF(pc) (1140KB) ( 421 )
The effect of a vortical electric field on nonlinear patterns in excitable media is studied. When an appropriate vortex electric field is applied, the system exhibits pattern transition from chemical turbulence to spiral waves, which possess the same chirality as the vortex electric field. The underlying mechanism of this is discussed. We also show the meandering behavior of a spiral under the taming of a vortex electric field. The results obtained here may contribute to control strategies of patterns on surface reaction.
An Approach to Enhance the Efficiency of a Brownian Heat Engine
ZHANG Yan-Ping, HE Ji-Zhou**, XIAO Yu-Ling
Chin. Phys. Lett. 2011, 28 (10): 100506 .   DOI: 10.1088/0256-307X/28/10/100506
Abstract   PDF(pc) (615KB) ( 434 )
A Brownian microscopic heat engine, driven by temperature difference and consisting of a Brownian particle moving in a sawtooth potential with an external load, is investigated. The heat flows, driven by both potential and kinetic energies, are taken into account. Based on the master equation, the expressions for efficiency and power output are derived analytically, and performance characteristic curves are plotted. It is shown that the heat flow via the kinetic energy of the particle decreases. The efficiency of the engine is enhanced, but the power output reduces as the α shape parameter of the sawtooth potential increases. The influence of the α shape parameter on efficiency and power output is then analyzed in detail.
Ground-State Transition in a Two-Dimensional Frenkel–Kontorova Model
YUAN Xiao-Ping, ZHENG Zhi-Gang**
Chin. Phys. Lett. 2011, 28 (10): 100507 .   DOI: 10.1088/0256-307X/28/10/100507
Abstract   PDF(pc) (691KB) ( 381 )
The ground state of a generalized Frenkel–Kontorova model with a transversal degree of freedom is studied. When the coupling strength, K, and the frequency of a single−atom vibration in the transversal direction, ω0y, are increased, the ground state of the model undergoes a transition from a two−dimensional configuration to a one-dimensional one. This transition can manifest in different ways. Furthermore, we find that the prerequisite of a two-dimensional ground state is θ≠1/q.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Classical Exchange Algebra of the Nonlinear Sigma Model on a Supercoset Target with 2n Grading
KE San-Min, **, LI Xin-Ying, WANG Chun, YUE Rui-Hong
Chin. Phys. Lett. 2011, 28 (10): 101101 .   DOI: 10.1088/0256-307X/28/10/101101
Abstract   PDF(pc) (509KB) ( 349 )
The classical exchange algebra satisfied by the monodromy matrix of the nonlinear sigma model on a supercoset target with 2n grading is derived using a first−order Hamiltonian formulation and by adding to the Lax connection terms proportional to constraints. This enables us to show that the conserved charges of the theory are in involution. When n=2, our results coincide with the results given by Magro for the pure spinor description of AdS5×S5 string theory (when the ghost terms are omitted).
Cosmic String Universes Embedded with Viscosity
Koijam Manihar Singh*, Kangujam Priyokumar Singh**
Chin. Phys. Lett. 2011, 28 (10): 101102 .   DOI: 10.1088/0256-307X/28/10/101102
Abstract   PDF(pc) (353KB) ( 348 )
We study string cosmological models with attached particles in LRS BI type space time. The dynamical and physical properties of such universes are studied, and the possibility that during the evolution of the universe the strings disappear, leaving only the particles, is also discussed. It is found that bulk viscosity plays a large role in the evolution of the universe. In these models we find critical instances of when there was a "Bounce". The studied models are found to be of an inflationary type, and since a desirable feature of a meaningful string cosmological model is the presence of an inflationary epoch in the very early stages of evolution, our models can be thought of as realistic universes.
The Oscillation Frequency of B and
Krishna Kingkar Pathak**, D. K. Choudhury
Chin. Phys. Lett. 2011, 28 (10): 101201 .   DOI: 10.1088/0256-307X/28/10/101201
Abstract   PDF(pc) (450KB) ( 372 )
Wavefunction at the origin, with the incorporation of a relativistic effect, leads to singularity in a specific potential model. To regularize the wavefunction, we introduced a short distance scale and used it to estimate the mass and decay constants of Bd and Bs mesons within the QCD potential model. These values were then used to compute the oscillation frequency, ΔmB, of Bd and Bs mesons. The values were found to be in good agreement with experimental and other theoretical values.
Contribution of the LHT Model to Zc
WANG Ya-Bin, LI Xiang-Dong, HAN Jin-Zhong, YANG Bing-Fang, **
Chin. Phys. Lett. 2011, 28 (10): 101202 .   DOI: 10.1088/0256-307X/28/10/101202
Abstract   PDF(pc) (895KB) ( 327 )
In the littlest Higgs model with T-parity (LHT), some new particles, such as the T-odd mirror quarks and goldstone bosons, can contribute to various observables. We calculate their contribution to Zcc coupling. Some observables are related to Zcc coupling, for example, the effective vector and axial−vector Zcc coupling constants (gVc,gAc) and c−quark forward-backward asymmetry (AcFB). We give our predictions about gVc,gAc in the LHT model and show the allowed regions of the mirror quark masses based on the experimental data of gVc−gAc. Then, we present an explanation of AcFB.
NUCLEAR PHYSICS
Tensor Effect on Bubble Nuclei
WANG Yan-Zhao, GU Jian-Zhong, **, ZHANG Xi-Zhen, DONG Jian-Min,
Chin. Phys. Lett. 2011, 28 (10): 102101 .   DOI: 10.1088/0256-307X/28/10/102101
Abstract   PDF(pc) (766KB) ( 550 )
In the framework of the Hartree–Fock–Bogoliubov (HFB) approach with Skyrme interactions SLy5+T, SLy5+Tw and several sets of TIJ parametrizations, i.e. the Skyrme interaction parametrizations including the tensor terms, the proton density distribution in 34Si and 46Ar nuclei is calculated with and without the tensor force. It is shown that the bubble effect in 34Si does not depend a great deal on the Skyrme parametrization and the proton density distribution in 34Si is hardly influenced by the tensor force. As to 46Ar, the SLy5+Tw parametrization favors the formation of the bubble structure due to the inversion between the 2s1/2 and 1d3/2 orbits (2s1/2–1d3/2 inversion). The inversion mechanism induced by the SLy5+Tw interaction is analyzed based on the proton single−particle spectra obtained from the SLy5 and SLy5+Tw interactions as well as the wave functions of the 2s1/2 and 1d3/2 states.
Effects of Neutron Skin Thickness in Peripheral Nuclear Reactions
FANG De-Qing**, MA Yu-Gang, CAI Xiang-Zhou, TIAN Wen-Dong, WANG Hong-Wei
Chin. Phys. Lett. 2011, 28 (10): 102102 .   DOI: 10.1088/0256-307X/28/10/102102
Abstract   PDF(pc) (499KB) ( 457 )
Effects of neutron skin thickness in peripheral nuclear collisions are investigated using the statistical abrasion ablation (SAA) model. The reaction cross section, neutron (proton) removal cross section, one-neutron (proton) removal cross section as well as their ratios for nuclei with different neutron skin thickness are studied. It is demonstrated that there are good linear correlations between these observables and the neutron skin thickness for neutron-rich nuclei. The ratio between the (one-)neutron and proton removal cross section is found to be the most sensitive observable of neutron skin thickness. Analysis shows that the relative increase of this ratio could be used to determine the neutron skin size in neutron-rich nuclei.
ATOMIC AND MOLECULAR PHYSICS
Calculation of Multiphoton Transition in Li Atoms via Chirped Microwave Pulse
JIA Guang-Rui, **, ZHANG Xian-Zhou, LIU Yu-Fang, YU Kun, ZHAO Yue-Jin
Chin. Phys. Lett. 2011, 28 (10): 103201 .   DOI: 10.1088/0256-307X/28/10/103201
Abstract   PDF(pc) (878KB) ( 331 )
The position and width of avoided crossings of Li atom energy levels in a static electric field is presented by using the B-spline basis set method combined with the model potential. Using the time-dependent multilevel approach, the population of Li atoms is transferred to the target state completely by one-photon, two-photon or a single multiphoton adiabatic rapid passage, which requires only a small frequency sweep. The calculation results agree well with the experiment and novel explanations are given to understand the experimental results.
Field-Free Molecular Orientation with a Few Half-Cycle Pulses in the Terahertz Region
YU Jie, ZHANG Wei YANG Jing, CONG Shu-Lin**
Chin. Phys. Lett. 2011, 28 (10): 103301 .   DOI: 10.1088/0256-307X/28/10/103301
Abstract   PDF(pc) (751KB) ( 573 )
A theoretical scenario used for achieving efficient field-free molecular orientation with a few half-cycle pulses (HCPs) is proposed, with the LiH molecule as an example. Compared with a single HCP, three HCPs can excite more rovibrational transitions and enhance the degree of molecular orientation. By optimizing the laser parameters, a maximum value of 0.798 for the degree of molecular orientation is obtained.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Electromagnetic Scattering from Randomly Rough Surfaces with Hybrid FEM/BIE
LI Jie**, GUO Li-Xin, HE Qiong, WEI Bing
Chin. Phys. Lett. 2011, 28 (10): 104101 .   DOI: 10.1088/0256-307X/28/10/104101
Abstract   PDF(pc) (552KB) ( 671 )
The hybrid finite element method (FEM) together with the boundary integral equation (BIE) is firstly applied to scattering from a conducting rough surface. The BIE is used as the truncation boundary condition for the special unbounded half space, whereas the FEM is used to solve the governing equation in the region surrounded by a rough surface and artificial boundary. Tapered wave incidence is employed to cancel the so-called "edge effect". A hybrid FEM/BIE formulation for generalized one-dimensional conducting rough surface scattering is presented, as well as examples that evaluate its validity compared to the method of moments. The bistatic scattering coefficients of a Gaussian rough surface are calculated for transverse-magnetic wave incidence. Conclusions are reached after analyzing the scattering patterns of rough surfaces with different rms heights and correlation lengths
Terahertz Emission Dependence on the Fundamental Optical Intensity in Generating Terahertz Waves from Two-Color Laser-Induced Gas Plasma
DAI Hou-Mei, LIU Jin-Song**
Chin. Phys. Lett. 2011, 28 (10): 104201 .   DOI: 10.1088/0256-307X/28/10/104201
Abstract   PDF(pc) (587KB) ( 415 )
A transient photocurrent model is used to explain terahertz emission from gas plasma irritated by two-color laser pulses, with one the second harmonic of the other. Taking multiple degrees of ionization into account, the gas ionization process at different laser intensities from 1014 W/cm2 to 1015 W/cm2 is discussed. The results show that when Iω6×1014 W/cm2, double ionization plays an important role in producing electrons. The corresponding terahertz spectra and waveforms are calculated, showing that increasing laser intensity can broaden the spectra to high frequencies and enhance the terahertz field.
An 80-W Laser Diode Array with 0.1 nm Linewidth for Rubidium Vapor Laser Pumping
YANG Zi-Ning, WANG Hong-Yan**, LU Qi-Sheng, HUA Wei-Hong, XU Xiao-Jun
Chin. Phys. Lett. 2011, 28 (10): 104202 .   DOI: 10.1088/0256-307X/28/10/104202
Abstract   PDF(pc) (580KB) ( 486 )
The spectral linewidth of a 64-emitter laser-diode array is effectively suppressed by using a volume Bragg grating (VBG) based external cavity. At a maximal driven current of 90 A, the device produces a cw output of 80W with 1.2 W/A slope efficiency and 0.1 nm spectral linewidth (FWHM) centered at 780 nm. The power extraction efficiency reaches 90% as compared with the free running case. The central wavelength of the narrowed spectrum is tuned over a 0.3 nm range by adjusting the VBG's temperature. The absorption of 45% laser radiation by a 5-mm-long rubidium vapor cell with 150 Torr ethane and 450 Torr helium at 383 K is demonstrated.
Electromagnetically Induced Transparency in an Optomechanical System
SHU Jing**
Chin. Phys. Lett. 2011, 28 (10): 104203 .   DOI: 10.1088/0256-307X/28/10/104203
Abstract   PDF(pc) (425KB) ( 499 )
We demonstrate a form of induced transparency enabled by the large gradient force between one optical and two mechanical modes. We tune the frequency of the mechanical flapping mode into resonance with the mechanical breathing mode to obtain the internal mechanical coupling. Compared with all-photonic physical systems, the quantum optomechanical system exhibits a significantly longer lifetime.
Wavelength Variation of a Random Laser with Concentration of a Gain Material
CHEN Shu-Jing, SHI Jin-Wei, ZHAI Tian-Rui, WANG Zhao-Na, LIU Da-He, **, CHEN Xiao
Chin. Phys. Lett. 2011, 28 (10): 104204 .   DOI: 10.1088/0256-307X/28/10/104204
Abstract   PDF(pc) (1256KB) ( 577 )
The wavelength variation of a laser-dye-type random laser is observed experimentally. It is found that the emitting wavelength of a random laser changes with the change of concentration of the gain material. Also, the actual radiation wavelength is influenced by the pumping rate of the source, the cavity competition and the concentration of scatterers.
Simulation and Analysis of Multisoliton Generation Using a PANDA Ring Resonator System
I. S. Amiri*, A. Afroozeh, M. Bahadoran
Chin. Phys. Lett. 2011, 28 (10): 104205 .   DOI: 10.1088/0256-307X/28/10/104205
Abstract   PDF(pc) (686KB) ( 752 )
A novel system of multisoliton generation using nonlinear equations of the propagating signals is presented. This system uses a PANDA ring resonator incorporated with an add/drop filter system. Using resonant conditions, the intense optical fields known as multisolitons can be generated and propagated within a Kerr-type nonlinear medium. The present simulation results show that multisolitons can be controlled by using additional Gaussian pulses input into the add port of the PANDA system. For the soliton pulse in the microring device, a balance should be achieved between dispersion and nonlinear lengths. Chaotic output signals from the PANDA ring resonator are input into the add/drop filter system. Chaotic signals can be filtered by using the add/drop filter system, in which multi dark and bright solitons can be generated. In this work multi dark and bright solitons with an FWHM and an FSR of 425 pm and 1.145 nm are generated, respectively, where the Gaussian pulse with a central wavelength of 1.55 µm and power of 600 mW is input into the system.
Broadening and Amplification of an Infrared Femtosecond Pulse for Optical Parametric Chirped-Pulse Amplification
WANG He-Lin, YANG Ai-Jun**, LENG Yu-Xin
Chin. Phys. Lett. 2011, 28 (10): 104206 .   DOI: 10.1088/0256-307X/28/10/104206
Abstract   PDF(pc) (646KB) ( 369 )
A high-average-power diode-pumped narrowband regenerative chirped pulse amplifier is developed using the thin-rod Nd:YAG laser architecture for optical parametric chirped-pulse amplification (OPCPA). The effect of the etalons on the amplified pulse in the regenerative cavity is studied experimentally and theoretically. By inserting glass etalons of thickness 1 mm and 5 mm into the regenerative cavity, the pre-stretching pulse from an Öffner stretcher is further broadened to above 200 ps, which matches the amplification windows of the signal pulses in OPCPA and is suitable for use as a pump source in the OPCPA system. The bandwidth of the amplified pulse is 1.5 nm, and an output energy of 2 mJ is achieved at a repetition rate of 10 Hz.
Narrow-Bandwidth Diode-Laser-Based Ultraviolet Light Source
PENG Yu, **, FANG Zhan-Jun, ZANG Er-Jun
Chin. Phys. Lett. 2011, 28 (10): 104207 .   DOI: 10.1088/0256-307X/28/10/104207
Abstract   PDF(pc) (624KB) ( 374 )
A compact, tunable and narrow-bandwidth laser source for ultraviolet radiation is presented. A grating stabilized diode laser at 1064 nm is frequency-stabilized to below 10 kHz by using a ultra low expansion (ULE) cavity. Injecting light of the diode laser into a tapered amplifier yields a power of 290 mW. In a first frequency-doubling stage, about 47 mW of green light at 532 nm is generated by using a periodically poled KTP crystal. Subsequent second-harmonic generation employing a BBO crystal leads to about 30 µW of ultraviolet light at 266 nm.
Two Diode Lasers Simultaneously Optically Locked by Orthogonal Polarizations of a Monolithic Confocal Cavity
PENG Yu, **, ZHAO Yang, LI Ye, YANG Tao, CAO Jian-Ping, FANG Zhan-Jun, ZANG Er-Jun
Chin. Phys. Lett. 2011, 28 (10): 104208 .   DOI: 10.1088/0256-307X/28/10/104208
Abstract   PDF(pc) (760KB) ( 415 )
We demonstrate two self-injection locking extended cavity diode lasers (ECDLs) using resonant optical feedback independently from s- and p-polarizations of a monolithic folded Fabry–Perot confocal cavity (MFC). The relative frequency shift of adjacent axial modes of s resonance and p resonance of MFC is around 1.030 GHz. Beat note measurements between the two ECDLs are performed and present a relative linewidth of 4 kHz. With the help of a narrow-linewidth reference laser, the linewidth of s-component and p-component ECDLs are measured to be about 32 kHz and 40 kHz, respectively.
A Family of Generalized Wigner Operators and Their Physical Meaning as Bivariate Normal Distribution
WANG Ji-Suo, **, MENG Xiang-Guo, FAN Hong-Yi
Chin. Phys. Lett. 2011, 28 (10): 104209 .   DOI: 10.1088/0256-307X/28/10/104209
Abstract   PDF(pc) (421KB) ( 360 )
By extending the usual Wigner operator to the s−parameterized one, we find that in the process of the generalized Weyl quantization the s parameter plays the role of correlation between two quadratures Q and P. This can be exposed by comparing the normally ordered form of Ωs with the standard form of the Gaussian bivariate normal distribution of random variables in statistics. Three different expressions of Ωs and the quantization scheme with use of it are presented.
Controllable Optical Switch in a One-Dimensional Resonator Waveguide Coupled to a Whispering-Gallery Resonator
LANG Jia-Hong*
Chin. Phys. Lett. 2011, 28 (10): 104210 .   DOI: 10.1088/0256-307X/28/10/104210
Abstract   PDF(pc) (810KB) ( 407 )
A New Ge/F−Co-doped SMF with Enhanced SBS Threshold Fabricated by PCVD
LIU Tian, TONG Wei-Jun, ZHANG Fang-Hai, ZHANG Xin-Ben, DAI Neng-Li**, LI Jin-Yan
Chin. Phys. Lett. 2011, 28 (10): 104211 .   DOI: 10.1088/0256-307X/28/10/104211
Abstract   PDF(pc) (542KB) ( 1302 )
A new single-mode fibre (SMF) with high stimulated Brillouin scattering (SBS) threshold which is co-doped with GeO2 and F2 in the core is reported. To increase the SBS threshold, the acousto−optic effective area is increased by designing a transverse acoustic waveguide and adjusting the doping level of GeO2 and F2 while the designed fiber retains a step optical refractive index profile. The optimal design is found by numerical simulation and the optimal fiber is fabricated by a plasma−activated chemical vapor deposition (PCVD) process. It yields the threshold 6.79 dB, which is higher than the conventional single-mode fiber G.652 and 3dB higher than the Corning® SMF−28e+™ optical fiber with NexCor® technology.
Fast Evaluation of Aberration-Induced Intensity Distribution in Partially Coherent Imaging Systems by Cross Triple Correlation
LIU Shi-Yuan, **, LIU Wei, WU Xiao-Fei
Chin. Phys. Lett. 2011, 28 (10): 104212 .   DOI: 10.1088/0256-307X/28/10/104212
Abstract   PDF(pc) (502KB) ( 314 )
We propose a method suitable for the fast calculation and evaluation of aberration-induced intensity distribution in partially coherent imaging systems, such as projection lithographic tools. The method is based on transmission cross coefficient (TCC) decomposition by a general operator, namely cross triple correlation (CTC). By expanding the aberrated pupil function into a Taylor series, the TCC is decomposed into different terms. Each term is further represented as a weighted sum of several CTCs. By exploring the properties of CTC, the aerial image intensity induced by wavefront aberration is calculated quickly and separated clearly from that without aberration. Simulation results and discussion are presented.
Recurrence Formulas for the Mie Series
SUN Ji-Yu, **, XIE Hong
Chin. Phys. Lett. 2011, 28 (10): 104214 .   DOI: 10.1088/0256-307X/28/10/104214
Abstract   PDF(pc) (584KB) ( 315 )
The Mie series has very important applications in electromagnetics (including optics). We employ a formulation for the Mie series which relies more on the derivatives of Legendre polynomials than Bessel functions. Recurrence formulas for derivatives related to Legendre polynomials are derived to realize the Mie series conveniently and to avoid treating special angles.
Seven Odd-Order Multi-Wave Mixing Spectra in a Five-Level Atomic System
ZHANG Ru-Yi, LI Liang, LI Jin, LI Ning, WU Zhen-Kun, LIU Hua, WANG Zhi-Guo, ZHENG Huai-Bin, ZHANG Yan-Peng**
Chin. Phys. Lett. 2011, 28 (10): 104215 .   DOI: 10.1088/0256-307X/28/10/104215
Abstract   PDF(pc) (710KB) ( 353 )
In a K-type five-level atomic system, seven odd-order multi-wave mixing (MWM) processes are considered. We can distinguish the MWM signals by selectively blocking different laser beams and changing frequency detuning. We study the interaction in seven odd-order MWM processes in a five-level atomic system and demonstrate the existence of mutual suppression of seven odd-order MWM processes by setting dual electromagnetically induced transparency windows as separated or merged.
Quantum Discord Dynamics in Two Different Non-Markovian Reservoirs
DING Bang-Fu**, WANG Xiao-Yun**, LIU Jing-Feng, YAN Lin, ZHAO He-Ping
Chin. Phys. Lett. 2011, 28 (10): 104216 .   DOI: 10.1088/0256-307X/28/10/104216
Abstract   PDF(pc) (661KB) ( 574 )
The quantum discord dynamics of two non-coupled two-level atoms independently interacting with their reservoir is studied under two kinds of non-Markovian conditions, namely, an off-resonant case with atomic transition frequency and a photonic band gap. In the first case, the phenomenon of the quantum discord loss and the oscillatory behavior of the quantum discord can occur by changing the detuning quantity and reducing the spectral coupling width for any initial Bell state. Under the second condition, the trapping phenomenon of the quantum discord can be presented by adjusting the width of gap, that is, the quantum discord of two atoms keep a nonzero constant for a long time.
Transmission Characteristics in Tubular Acoustic Metamaterials Studied with Fluid Impedance Theory
FAN Li**, ZHANG Shu-Yi, ZHANG Hui
Chin. Phys. Lett. 2011, 28 (10): 104301 .   DOI: 10.1088/0256-307X/28/10/104301
Abstract   PDF(pc) (610KB) ( 570 )
Tubular acoustic metamaterials with negative densities composed of periodical membranes set up along pipes are studied with the fluid impedance theory. In addition to the conventional forbidden bands induced by the Bragg-scattering due to the periodic distributions of different acoustic impedances, the low-frequency forbidden band (LFB) with the low-frequency limit of zero Hertz is studied, in which the LFB is explained with acoustic impedance matching and the Bloch theory. Furthermore, the influences of the structural parameters of the tubular acoustic metamaterials on the transmission characteristics, such as the transmission coefficients, dispersion curves, widths of forbidden and pass bands, fluctuations in pass bands, etc., are evaluated, which can be used in the optimization of the acoustic insulation ability of the metamaterials.
Theoretical Calculation of a Focused Acoustic Field from a Linear Phased Array on a Concave Cylindrical Transducer
YU Li-Li**, SHOU Wen-De, HUI Chun**
Chin. Phys. Lett. 2011, 28 (10): 104302 .   DOI: 10.1088/0256-307X/28/10/104302
Abstract   PDF(pc) (691KB) ( 713 )
A new linear phased array on a concave cylindrical transducer is designed for meeting the specific requirements of applications for interstitial thermal ablation. Using the array, a focal line can be generated rapidly and the focal position can be adjusted in the proper range without the use of complex mechanical structures. The focused acoustic field distributions in the axial, radial and azimuthal directions of the transducer are investigated theoretically by numerical simulation. Effects of the focal distance, steering angle, element arc-width, arc-space between adjacent elements and number of elements on the acoustic field are also thoroughly studied. Many important results are obtained.
Calculation of Loudspeaker Cabinet Diffraction and Correction
LE Yi, SHEN Yong**, XIA Jie
Chin. Phys. Lett. 2011, 28 (10): 104303 .   DOI: 10.1088/0256-307X/28/10/104303
Abstract   PDF(pc) (484KB) ( 1461 )
A method of calculating the cabinet edge diffractions for loudspeaker driver when mounted in an enclosure is proposed, based on the extended Biot–Tolstoy–Medwin model. Up to the third order, cabinet diffractions are discussed in detail and the diffractive effects on the radiated sound field of the loudspeaker system are quantitatively described, with a correction function built to compensate for the diffractive interference. The method is applied to a practical loudspeaker enclosure that has rectangular facets. The diffractive effects of the cabinet on the forward sound radiation are investigated and predictions of the calculations show quite good agreements with experimental measurements.
The Method of Variation of Parameters for Solving a Dynamical System of Relative Motion
ZHANG Yi**
Chin. Phys. Lett. 2011, 28 (10): 104501 .   DOI: 10.1088/0256-307X/28/10/104501
Abstract   PDF(pc) (391KB) ( 342 )
The integration method of a dynamical system of relative motion is studied, and the method of variation of parameters for the dynamical equations of relative motion is presented. First, the dynamic equations of relative motion are brought into the frame of generalized Birkhoffian systems and are expressed in the contravariant algebraic form. Second, an auxiliary system is constructed and its complete solution is found. Finally, the variation of parameters is given, and a complete solution of the problem is obtained by taking advantage of the properties of generalized canonical transformations. An example is given to illustrate the application of the results.
Flow Characteristics of Deionized Water in Microtubes Absorbing Fluoro-Alkyl Silanes
QU Chao, SONG Fu-Quan**
Chin. Phys. Lett. 2011, 28 (10): 104701 .   DOI: 10.1088/0256-307X/28/10/104701
Abstract   PDF(pc) (575KB) ( 392 )
In order to find the drag reduction mechanism of surface wettability, some experiments are carried out to research the flow of deionized water through microtubes. The flow rate of liquid through microtubes adsorbing Fluoro–Alkyl silanes (FAS) or not are compared. The inner diameters of the microtubes are 100 µm, 75 µm and 50 µm, respectively. The relations of shear rate and slip velocity, and shear rate and slip length are discussed. The inner surface wettability of the microtubes changes from hydrophilic at a contact angle of 23° to weak hydrophobic at a contact angle of 107° by adsorbing FAS. The results indicate that the flow rate in microtubes adsorbing FAS is larger than those without FAS, the efficiency of drag reduction if about 13%, the slip velocity near the wall is proportional to the shear rate and the slip length remains invariant for different shear rates in microtubes with different diameters.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Plasma Catalytic Synthesis of Silver Nanoparticles
ZHANG Yu-Tao**, GUO Ying, MA Teng-Cai
Chin. Phys. Lett. 2011, 28 (10): 105201 .   DOI: 10.1088/0256-307X/28/10/105201
Abstract   PDF(pc) (2574KB) ( 789 )
We present the experimental results of plasma catalytic synthesis of colloidal silver nanoparticles, using AgNO3 as the precursor, ethanol as the solvent and reducing agent, and poly vinyl pyrrolidone (PVP) as the macromolecular surfactant. The plasma is generated by an atmospheric argon dielectric barrier discharge jet. Silver nanoparticles are produced instantly once the plasma is ignited. The system is not heated so it is necessary to use traditional chemical methods. The samples are characterized by UV−visible absorbance and transmission electron microscopy. For glow discharge mode no obvious silver nanoparticles are observed. For low voltage filamentary streamer discharge mode a lot of silver nanoparticles with the mean diameter of 3.5 nm are generated and a further increase of the voltage causes the occurrence of agglomeration.
Neutron Flux Measurements in an ICRF Mode Conversion Regime Heating Plasmas on HT-7
LI Xiao-Ling**, WAN Bao-Nian, ZHONG Guo-Qiang, HU Li-Qun, LIN Shi-Yao, ZHANG Xin-Jun, ZANG Qing
Chin. Phys. Lett. 2011, 28 (10): 105202 .   DOI: 10.1088/0256-307X/28/10/105202
Abstract   PDF(pc) (945KB) ( 356 )
Ion cyclotron resonance heating experiments using antenna in the high field side (HFS) have been carried out on HT-7 in different target plasmas. Unlike a standard-mode conversion heating scheme with dominant electron heating, anomalous ion heating and DD neutron fluxes higher than those estimated from thermal ions were observed in the present experiments with the ion-ion hybrid resonant layer near the center of plasma. The features of ion cyclotron range frequency (ICRF) antenna in HFS and experiments suggest that this is most probably due to the nonlinear 3/2 harmonic deuterium heating by the mode-converted ion Bernstein wave, which could produce a high energy tail on ion energy distribution.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Instability of a Biaxial Nematic Liquid Crystal Formed by Homeotropic Anchoring on Surface Grooves
ZHANG Zhi-Dong**, XUAN Li
Chin. Phys. Lett. 2011, 28 (10): 106101 .   DOI: 10.1088/0256-307X/28/10/106101
Abstract   PDF(pc) (449KB) ( 415 )
A method used to treat the elastic distortion of a uniaxial nematic liquid crystal induced by homogeneous anchoring on the surface grooves is generalized to biaxial nematic liquid crystals under the homeotropic anchoring condition. Employing some approximations for the elastic constants, we obtain an additional term in the elastic energy per unit area which depends on the angle between the minor director at infinity and the direction of the grooves, with a period of π/2. This leads to instability on the surface grooves so that two states with crossed minor directors are energetically indistinguishable. Our theoretical study explains why the homeotropic alignment method developed for uniaxial liquid crystals loses efficacy for biaxial nematics.
Influence of Surface Effects on the Elastic Properties of Silicon Nanowires with Different Cross Sections
GU Fang, ZHANG Jia-Hong**, XU Lin-Hua, LIU Qing-Quan, LI Min
Chin. Phys. Lett. 2011, 28 (10): 106102 .   DOI: 10.1088/0256-307X/28/10/106102
Abstract   PDF(pc) (662KB) ( 614 )
Based on the anharmonic Keating model and the modified bending theory, an analytical semi-continuum atomistic lattice model is proposed for the size-dependent bending mechanical analysis of silicon nanowires (SiNWs) with different cross-sectional shapes. The semi-continuum model proves that the elastic behavior of SiNWs is size-dependent and predicts softer or stiffer SiNWs which depend on the relaxation coefficient and the surface tension. It also shows that the size effects of the mechanical responses of SiNWs depend on not only surface effects but also the cross-sectional shapes of SiNWs.
Mechanical Properties and Defect Evolution of Kr-Implanted 6H-SiC
XU Chao-Liang, **, ZHANG Chong-Hong, ZHANG Yong, ZHANG Li-Qing, YANG Yi-Tao, JIA Xiu-Jun, LIU Xiang-Bing, HUANG Ping, WANG Rong-Shan
Chin. Phys. Lett. 2011, 28 (10): 106103 .   DOI: 10.1088/0256-307X/28/10/106103
Abstract   PDF(pc) (991KB) ( 344 )
Specimens of silicon carbide (6H-SiC) were irradiated with 5 MeV Kr ions (84Kr19+) for three fluences of 5×1013, 2×1014 and 1×1015 ions/cm2, and subsequently annealed at room temperature, 500 °C, 700 °C and 1000 °C, respectively. The strain of the specimens was investigated with high resolution XRD and different defect evolution processes are revealed. An interpretation of the defect evolution and migration is given to explain the strain variation. The mechanical properties of the specimens were studied by using a nano−indentation technique in continuous stiffness measurement (CSM) mode with a diamond Berkovich indenter. For specimens irradiated with fluences of 5×1013 or 2×1014 ions/cm2, hardness values exceed that of un−implanted SiC. However, hardness sharply degrades for specimens irradiated with the highest fluence of 1×1015 ions/cm2. The specimens with fluences of 5×1013 and 2×1014 ions/cm2 and subsequently annealed at 700 °C and 500 °C, respectively, show the maximum hardness value.
H2-Assistance One-Step Growth of Si Nanowires and Their Growth Mechanism
QIU Ming-Xia, RUAN Shuang-Chen**, GAO Biao, HUO Kai-Fu, ZHAI Jian-Pang, LI Ling, LIAO Hui, XU Xin-Tong
Chin. Phys. Lett. 2011, 28 (10): 106104 .   DOI: 10.1088/0256-307X/28/10/106104
Abstract   PDF(pc) (792KB) ( 337 )
Large-scale nanowires are grown on Si wafers by the catalyst-free one-step thermal reaction method in Ar/H2 mixture atmosphere at 1000 °C. The x−ray diffraction and energy dispersive x-ray spectroscopy results reveal that the final nanowires are of silicon nanostructures. The field emission scanning electron microscopy shows that these self-organized Si nanowires (SiNWs) possess curly crowns with diameters varying from 10 to 300 nm and lengths of up to several hundreds of micrometers. The transmission electron microscopy indicates that the nanowires are pure Si with amorphous structures. All the measurement results show that no silicon oxide is generated in our products. The growth mechanism is proposed tentatively. Silicon oxide is reduced into Si nanoparticles under the Ar/H2 mixture, which is the main reason for the formation of such SiNWs. Our experiments offer a method of preparing Si nanostructures by simply reducing silicon oxide at high temperature.
Interdiffusion Flux and Interface Movement in Metallic Multilayers
LI Yong-Sheng**, CHENG Xiao-Ling, XU Feng, DU Yu-Lei
Chin. Phys. Lett. 2011, 28 (10): 106601 .   DOI: 10.1088/0256-307X/28/10/106601
Abstract   PDF(pc) (1067KB) ( 392 )
Interdiffusion in the diffusion couples of metallic multilayers is investigated for the variation of mobility and different initial phase separation (IPS) states. A phase field simulation shows that the diffusion flux and interface movement increase for higher atomic mobility. The shorter IPS time influences the diffusion flux of two-phase diffusion couples, and has almost no influence on the interface movement.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Optical Properties and Photocatalytic Activity of Marokite-Type CaMn2O4
WU Xue-Wei, ZHANG Hai-Xin, LIU Xiao-Jun**, ZHANG Xing-Gan**
Chin. Phys. Lett. 2011, 28 (10): 107101 .   DOI: 10.1088/0256-307X/28/10/107101
Abstract   PDF(pc) (708KB) ( 955 )
The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U (LSDA+U) method. Four absorption bands are observed at 638 nm (1.94 eV), 512 nm (2.42 eV), 377 nm (3.29 eV) and 248 nm (5.00 eV), which are ascribed to the charge transfer transitions O2p↑→Mn3d eg, O2p↓→Mn3d eg, Mn3d eg↑→Mn3d t2g and O2p↑→Mn3d t2g, respectively. We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7 (AO7) under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9% under the irradiation of visible light for two hours.
Reproduced Giant Localization Length of Two-Side Surface Disordered Nanowires with Long-Range Correlation
ZHAO Wei**, DING Jian-Wen
Chin. Phys. Lett. 2011, 28 (10): 107102 .   DOI: 10.1088/0256-307X/28/10/107102
Abstract   PDF(pc) (595KB) ( 347 )
We numerically investigate the normalized localization length of two-side rough nanowires as functions of energy, magnetic field and correlation strength by using modular recursive Green's function method. It is found that in the absence of correlation, while in the presence of magnetic field, the localization length increases linearly for two-side roughness, which is different to diverging exponentially for one-side roughness. Moreover, the localization of electrons is suppressed in the low energy region, but enhanced in the high energy region. In the presence of correlation, especially, an exponential enhancement in the localization length resumes in high energy region, in contrast to that in low energy region, the long-range correlations abnormally enhance the localization of electrons. A competitive mechanism is proposed to explain this behavior.
Red Afterglow Properties of Eu3+ in CaMoO4 Phosphor
KANG Feng-Wen, HU Yi-Hua**, WU Hao-Yi, JU Gui-Fang
Chin. Phys. Lett. 2011, 28 (10): 107201 .   DOI: 10.1088/0256-307X/28/10/107201
Abstract   PDF(pc) (666KB) ( 794 )
Eu3+ doped CaMoO4 phosphors were synthesized by using the solid state reaction method. The x−ray diffraction shows that all the patterns of the obtained samples are indexed to the sheelite structure. Red afterglow originating from the 5D07FJ (J=0,1,2,3,4) transitions of Eu3+ was observed after the samples were excited by 254 nm and the optimal Eu3+ concentration in the CaMoO4 matrix was experimentally determined to be 0.50%. A possible explanation of this afterglow property is also discussed.
High-Efficiency Graphene Photo Sensor Using a Transparent Electrode
LIU Tao**, HUANG Zheng
Chin. Phys. Lett. 2011, 28 (10): 107301 .   DOI: 10.1088/0256-307X/28/10/107301
Abstract   PDF(pc) (449KB) ( 467 )
We report the first implementation of transparent electrodes in bottom-gate graphene transistors used for photo detection. Compared to conventional nontransparent electrodes, the transparent electrodes allow photons to transmit through to the graphene beneath, providing an enlarged absorption area and thereby giving rise to an enhancement of photocurrent generation. The devices are fabricated with an asymmetric metallization scheme and the experimental results show that the maximum photocurrent density using the transparent electrodes (ITO and Pd/ITO) is over two times higher than that using the nontransparent electrodes (Ti and Pd), indicating a significant enhancement in the performance of graphene photo sensors.
Direct Experimental Evidence of Hole Trapping in Negative Bias Temperature Instability
JI Xiao-Li, LIAO Yi-Ming, YAN Feng**, SHI Yi, ZHANG Guan, GUO Qiang
Chin. Phys. Lett. 2011, 28 (10): 107302 .   DOI: 10.1088/0256-307X/28/10/107302
Abstract   PDF(pc) (667KB) ( 600 )
Negative bias temperature instability (NBTI) in ultrathin-plasma-nitrided-oxide (PNO) based p-type metal-oxide-semiconductor field effect transistors (pMOSFETs) is investigated at temperatures ranging from 220 K to 470 K. It is found that the threshold voltage VT degradation below 290 K is dominated by the hole trapping process. Further studies unambiguously show that this process is unnecessarily related to nitrogen but the incorporation of nitrogen in the gate dielectric increases the probability of hole trapping in the NBTI process as it introduces extra trap states located in the upper half of the Si band gap. The possible hole trapping mechanism in NBTI stressed PNO pMOSFETs is suggested by taking account of oxygen and nitrogen related trap centers.
A High Breakdown Voltage AlGaN/GaN MOSHEMT Using Thermal Oxidized Al-Ti as the Gate Insulator
ZHOU Bin, WANG Jin-Yan**, MENG Di, LIN Shu-Xun, FANG Min, DONG Zhi-Hua, YU Min, HAO Yi-Long, Cheng P. WEN
Chin. Phys. Lett. 2011, 28 (10): 107303 .   DOI: 10.1088/0256-307X/28/10/107303
Abstract   PDF(pc) (749KB) ( 702 )
Direct oxidation of composite Al/Ti metal films as gate insulators for AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOSHEMTs/HEMTs) is successfully realized. The devices fabricated with this novel process exhibit four orders of magnitude reduction in gate leakage current and remarkable breakdown voltage (V br=490 V vs 88 V for normal HEMT) improvement, compared with conventional Schottky-gate HEMTs. Furthermore, the transconductance of the MOSHEMT is only slightly lower (2.6%) than that of Schottky-gate HEMTs and have a wider full width of half maximum. The notable enhancement in device performance renders this new process highly promising for GaN-based microwave power amplifier applications in communication and radar systems.
Fabrication of a ZnO:Al/Amorphous-FeSi2 Heterojunction at Room Temperature
XU Jia-Xiong, YAO Ruo-He*, LIU Yu-Rong
Chin. Phys. Lett. 2011, 28 (10): 107304 .   DOI: 10.1088/0256-307X/28/10/107304
Abstract   PDF(pc) (505KB) ( 421 )
A prototype ZnO:Al/amorphous-FeSi2 heterojunction was successfully prepared on a glass substrate by magnetron sputtering at room temperature. The structural and electrical properties of as−deposited FeSi2 thin films were investigated using x−ray diffraction, Raman scattering, resistivity, and carrier lifetime measurement. The FeSi2 thin film showed an amorphous phase with resistivity of 9.685 Ω⋅cm and carrier lifetime of 9.5 µs. The prototype ZnO:Al/amorphous−FeSi2 heterojunction exhibited a rectifying property of the diode from the dark current−voltage characteristic. This propert was evaluated using the shunt resistance and diode ideal factor. The experimental results suggest that the amorphous-FeSi2 thin film has promising applications in heterojunction devices with low thermal budget and low product cost.
Neutrino-Electron Scattering and the Little Higgs Models
LI Na, YUE Chong-Xing**, LI Xu-Xin
Chin. Phys. Lett. 2011, 28 (10): 107305 .   DOI: 10.1088/0256-307X/28/10/107305
Abstract   PDF(pc) (467KB) ( 439 )
The neutrino-electron scattering process is sensitive to the standard model (SM) and the new physics beyond the SM. We calculate the corrections of the littlest Higgs model and the SU(3) simple group model to the νe e scattering cross section. Using the LSND experimental measured values, we obtain the bounds on the relevant free parameters, which might be compatible with those from the electroweak precision data.
Tunneling Processes in Optically Excited Quantum Dots
LI Xiu-Ping, WEI Hua-Rong, XU Li-Ping, GONG Jian-Ping, YAN Wei-Xian
Chin. Phys. Lett. 2011, 28 (10): 107306 .   DOI: 10.1088/0256-307X/28/10/107306
Abstract   PDF(pc) (557KB) ( 334 )
The single-electron tunneling processes in optically excited coupled quantum dots can be divided into two parts: the electron and the hole parts, which are analytically obtained in the framework of the Keldysh formalism. The tunneling process is selective tunneling, which results in dark tunneling states. The tunneling currents are co-determined by the resonance energies and probability distributions of the particular quantum channels defined by the electron-hole complex resonant states.
Behaviour of Charge Carriers in As-Deposited and Annealed Undoped TCO Films
ZHOU Yan-Wen**, WU Fa-Yu, ZHENG Chun-Yan
Chin. Phys. Lett. 2011, 28 (10): 107307 .   DOI: 10.1088/0256-307X/28/10/107307
Abstract   PDF(pc) (629KB) ( 501 )
We examine the structures, cut-off points of transmittance spectra and electric properties of undoped ZnO, SnO2 and CdO films by scanning electron microscopy, x-ray diffraction, spectrophotometer and Hall-effect measurements, respectively. The films are deposited by using an rf magnetron sputtering system from powder targets in argon and then annealed in vacuum. The structures and properties of the as-deposited films are compared with those of the annealed one. We try to explain the behaviour of charge carriers based on the semiconductor physics theory.
Reversible and Reproducible Giant Universal Electroresistance Effect
SYED Rizwan, ZHANG Sen, YU Tian, ZHAO Yong-Gang, ZHANG Shu-Feng, HAN Xiu-Feng**
Chin. Phys. Lett. 2011, 28 (10): 107308 .   DOI: 10.1088/0256-307X/28/10/107308
Abstract   PDF(pc) (868KB) ( 358 )
After the prediction of the giant electroresistance effect, much work has been carried out to find this effect in practical devices. We demonstrate a novel way to obtain a large electroresistance (ER) effect in the multilayer system at room temperature. The current-in-plane (CIP) electric transport measurement is performed on the multilayer structure consisting of (011)-Pb(Mg1/3Nb2/3)O3−PbTiO3(PMN−PT)/Ta/Al-O/metal. It is found that the resistance of the top metallic layer shows a hysteretic behavior as a function electric field, which corresponds well with the substrate polarization versus electric field (PE) loop. This reversible hysteretic RE behavior is independent of the applied magnetic field as well as the magnetic structure of the top metallic layer and keeps its memory state. This novel memory effect is attributed to the polarization reversal induced electrostatic potential, which is felt throughout the multilayer stack and is enhanced by the dielectric Al-O layer producing unique hysteretic, reversible, and reproducible resistance switching behavior. This novel universal electroresistance effect will open a new gateway to the development of future multiferroic memory devices operating at room temperature.
Electric and Magnetic Field Tunable Rectification and Magnetoresistance in FexGe1−x/Ge Heterojunction Diodes
QIN Yu-Feng, YAN Shi-Shen, KANG Shi-Shou, XIAO Shu-Qin, LI Qiang, DAI Zheng-Kun, SHEN Ting-Ting, DAI You-Yong**, LIU Guo-Lei, CHEN Yan-Xue, MEI Liang-Mo, ZHANG Ze
Chin. Phys. Lett. 2011, 28 (10): 107501 .   DOI: 10.1088/0256-307X/28/10/107501
Abstract   PDF(pc) (591KB) ( 397 )
FexGe1−x/Ge amorphous heterojunction diodes with p-FexGe1−x ferromagnetic semiconductor layers are grown on single-crystal Ge substrates of p-type, n-type and intrinsic semiconductors, respectively. The IV curves of p−Fe0.4Ge0.6/p−Ge diodes only show slight changes with temperature or with magnetic field. For the p-Fe0.4Ge0.6/n−Ge diode, good rectification is maintained at room temperature. More interestingly, the IV curve of the p−Fe0.4Ge0.6/i-Ge diode can be tuned by the magnetic field, indicating a large positive magnetoresistance. The resistances of the junctions decrease with the increasing temperature, suggesting a typical semiconductor transport behavior. The origin of the positive magnetoresistance is discussed based on the effect of the electric and magnetic field on the energy band structures of the interface.
Effect of Porous Structure on the Magnetic Properties of NixMgyZn1−x-yFe2O4 Magnetic Materials
QI Xin, ZHOU Xin, SHU Di, ZHAO Jing-Jing, WANG Wei, CHEN Juan**
Chin. Phys. Lett. 2011, 28 (10): 107502 .   DOI: 10.1088/0256-307X/28/10/107502
Abstract   PDF(pc) (714KB) ( 377 )
We deal with the preparation of NiMgZnFeIII−SO4 layered double hydroxides (LDHs) with the layered precursor method and introduce excessive ZnO into the NiMgZnFeIII−SO4 LDHs to produce NixMgyZn1−x-yFe2O4 ferrites that contain massive ZnO. Then the NixMgyZn1−x-yFe2O4 ferrites are treated with NaOH solution to remove ZnO to produce the porous NixMgyZn1−x-yFe2O4 magnetic material: when y=0, porous NiZnFe2O4 ferrite magnetic materials are obtained; when y≠0, porous NiMgZnFe2O4 ferrite magnetic materials are obtained. From analyses of these two ferrites, their pore−forming mechanism and comparison of their properties before and after they undergo the alkali treatment, we find that after being treated by the NaOH solution, NiZnFe2O4/ NiMgZnFe2O4 have better uniform-structure pores, which will greatly expand their pore volume, widen their application scope and improve their magnetic properties.
High Magnetoelectric Coupling in Nano–Microscale Particulate Composites at Low Frequency
ZHOU Yun**, CHEN Miao-Gen, FENG Zhen-Jie, WANG Xin-Yan, CUI Yu-Jian, ZHANG Jin-Cang
Chin. Phys. Lett. 2011, 28 (10): 107503 .   DOI: 10.1088/0256-307X/28/10/107503
Abstract   PDF(pc) (888KB) ( 471 )
Nontoxic lead-free multiferroic magnetoelectric composites are successfully prepared by incorporating the dispersed Ni0.98Co0.02Fe2O4 (NCF) ferromagnetic nanoparticles into a (K0.5Na0.5)NbO3−LiSbO3 (KNN−LS) ferroelectric micromatrix. The dependence of the dielectric properties and dc magnetization on NCF phase content has been studied. Variation of dielectric constant and dielectric loss with frequency show dispersion in the low frequency range, and the dielectric constants decrease with the increase in ferrite NCF content. The magnetoelectric (ME) coupling effects including direct ME (DME) and converse ME (CME) effects are investigated in detail at room temperature. The results show that the NCF content significantly affects the ME effects. The CME and DME behaviors are strongly dependent on the driving field frequency and the bias magnetic field. High DME and CME coefficients are obtained at low frequency and at low magnetic bias field. The maximum value of DME and CME coefficients are 197.3 ps/m (12.2 mV⋅cm−1⋅Oe−1) and 314.7 ps/m, respectively.
MWCNTs/SiO2 Composite System: Carrier Transmission, Twin-Percolation and Dielectric Properties
CAO Wen-Qiang, , LU Ming-Ming, WEN Bo, CHEN Yuan-Lu, LI Hong-Bo, YUAN Jie**, CAO Mao-Sheng**
Chin. Phys. Lett. 2011, 28 (10): 107701 .   DOI: 10.1088/0256-307X/28/10/107701
Abstract   PDF(pc) (1564KB) ( 347 )
We synthesize composite systems of multi-wall carbon nanotubes (MWCNTs)/SiO2 by using the sol−gel method. The dielectric properties of the systems with different-concentration MWCNTs are studied. In our MWCNTs/SiO2 inorganic systems, the twin−percolation phenomenon exists when the concentrations of MWCNTs are 5–10% and 15–20%. The permittivity and conductivity have jumping changes. The twin−percolation phenomenon is attributed to the special transfer mechanism of MWCNTs in the system, determined by hopping and migrating electrons. Variations of dielectric properties and conductance of the MWCNTs/SiO2 systems are conformed to the percolation theory. The special percolation phenomenon and electric properties of MWCNTs/SiO2 can help us comprehend the conductivity mechanism of the MWCNTs/SiO2 systems effectively, and promote the development of a high performance function composite system.
Thickening of Non-Ferroelectric Capacitive Layers with Enhanced Domain Switching Speed in Polyvinylidence Fluoride Copolymer Thin Films
LIU Xiao-Bing, MENG Jian-Wei, JIANG An-Quan**, WANG Jian-Lu
Chin. Phys. Lett. 2011, 28 (10): 107702 .   DOI: 10.1088/0256-307X/28/10/107702
Abstract   PDF(pc) (790KB) ( 379 )
The large coercive field of domain switching in poly(vinylidene fluoride-trifluoroethylene) thin films is in much part due to the contribution of nonpolar impurity phases rather than the manifestation of an intrinsic domain switching mechanism of the ferroelectric layer. We coincidentally derive the equivalent electrical capacitance for the total non-ferroelectric capacitive layers from either domain switching current transient or voltage dependence of the switched polarization. Unexpectedly, the non-ferroelectric capacitance reduces by more than 71% with the enhancement of domain switching speed spanning over 5 orders of magnitude in company with the continuous reduction of the remanent polarization, which suggests the thickening of the above capacitive layers with enhanced domain switching speed.
Rectifying the Current−Voltage Characteristics of a LiNbO3 Film/GaN Heterojunction
HAO Lan-Zhong, **, LIU Yun-Jie, ZHU Jun**, LEI Hua-Wei, LIU Ying-Ying, TANG Zheng-Yu, ZHANG Ying, ZHANG Wan-Li, LI Yan-Rong
Chin. Phys. Lett. 2011, 28 (10): 107703 .   DOI: 10.1088/0256-307X/28/10/107703
Abstract   PDF(pc) (619KB) ( 814 )
Epitaxial LiNbO3 (LNO) films are grown on n−type GaN semiconductor substrates, forming LNO/GaN p-n junctions. The current-voltage (IV) and capacitance−voltage (CV) characteristics of the junctions are studied. The IV curve shows a clear rectifying property with a turn−on voltage of 2.4 V. For the forward voltages, the conduction mechanism transits from Schottky thermionic emission for low voltages to space-charge-limited current for large voltages. Reverse CV characteristics exhibit a linear 1/C2 versus V plot, from which a built-in potential of 0.34 V is deduced. These results are explained using the energy-band structure of the LNO/GaN junction.
Frequency Response of Modulated Electroluminescence of Light-Emitting Diodes
FENG Lie-Feng**, LI Yang, LI Ding, WANG Cun-Da, ZHANG Guo-Yi, YAO Dong-Sheng, LIU Wei-Fang, XING Peng-Fei
Chin. Phys. Lett. 2011, 28 (10): 107801 .   DOI: 10.1088/0256-307X/28/10/107801
Abstract   PDF(pc) (584KB) ( 1061 )
Frequency responses of modulated electroluminescence (EL) of light-emitting diodes were measured using a testing setup. With increasing frequency of the ac signal, the relative light intensity (RLI) clearly decreases. Furthermore, a peculiar asynchrony between the RLI and ac small-signal is observed. At frequencies higher than 10 kHz, the RLI clearly lags behind the ac signal and the absolute value of the lagging angle is nearly proportional to the signal frequency. Using the classical recombination model of light-emitting diodes under ac small-signal modulation, these abnormal characteristics of modulated EL can be clearly explained.
Structural and Magnetic Properties of Ni-Implanted Rutile Single Crystals
DING Bin-Feng**, LI Yong-Ping, WANG Li-Ming
Chin. Phys. Lett. 2011, 28 (10): 107802 .   DOI: 10.1088/0256-307X/28/10/107802
Abstract   PDF(pc) (738KB) ( 517 )
The structural and magnetic properties of Ni-implanted rutile single crystals are discussed. Ni nanocrystals (NCs) are formed in TiO2 after ion implantation. Their crystalline sizes increase with increasing post−annealing temperature. Metallic Ni nanocrystals inside the TiO2 matrix are stable up to an annealing temperature of 1073 K. The Ni NCs formed inside TiO2 are the major contribution to the measured ferromagnetism.
Nonlinear Optical Studies of [(C4H9)4N][Ni(dmit)2] by Z-Scan Technique
SUN Jing**, ZHAO Yi-Kun, WANG Xin-Qiang, REN Quan, CHEN Jing-Wei, ZHANG Guang-Hui, XU Dong, WANG He-Zhou
Chin. Phys. Lett. 2011, 28 (10): 107803 .   DOI: 10.1088/0256-307X/28/10/107803
Abstract   PDF(pc) (544KB) ( 577 )
Nonlinear optical properties of an organo-metallic compound [(C4H9)4N][Ni(dmit)2] (dmit=2−thioxo-1,3-dithiole-4,5-dithiolate), abbreviated as BuNi, dissolved in acetone, are investigated using the Z-scan technique with a 40 ps pulse width at 1064 nm and a 1 ns and 15 ns pulse width at 1053 nm. Strong saturable absorption is found when the sample solution is irradiated by 40 ps and 1 ns laser pulses. When irradiated with a 15 ns laser pulse, a stronger reverse saturable absorption is found. The nonlinear optical absorption coefficients are -1.06×10-11, −2.02×10-11 and 2.73×10−10 m/W, respectively. All the results suggest that BuNi may be a promising candidate in the application of laser pulse compression in the near-infrared waveband.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Ultraviolet-Visible Electroluminescence of a p-ZnO:As/n-Si Device Formed by the GaAs Interlayer Doping Method
XIA Xiao-Chuan, WANG Hui, ZHAO Yang, WANG Jin, ZHAO Jian-Ze, SHI Zhi-Feng, LI Xiang-Ping, LIANG Hong-Wei, ZHANG Bao-Lin, DU Guo-Tong, **
Chin. Phys. Lett. 2011, 28 (10): 108101 .   DOI: 10.1088/0256-307X/28/10/108101
Abstract   PDF(pc) (578KB) ( 414 )
Arsenic doped p-type ZnO films were grown on n-type silicon substrates using the GaAs interlayer doping method. Under our growth conditions the main doping element is arsenic, which was confirmed by x-ray photoelectroscopy. X-ray diffraction measurements revealed that the p-ZnO:As film was still in the (002) preferred orientation. The Hall test showed that the hole concentration of the p-ZnO:As film was 2.6 × 1017 cm−3. The acceptor level was located at 135 meV above the valance band maximum, according to the low-temperature photoluminescence results. We then fabricated a p-ZnO:As/n-Si heterojunction light-emitting device. Its current-voltage curve showed the typical rectifying behavior of a p–n diode. At forward current injections, the electroluminescence peaks, which cover the ultraviolet-to-visible region, could be clearly detected.
In Situ Observation of NaCl Crystal Growth by the Vapor Diffusion Method with a Mach–Zehnder Interferometer
ZHAO Jing, MIAO Hong**, DUAN Li, KANG Qi, HE Ling-Hui
Chin. Phys. Lett. 2011, 28 (10): 108102 .   DOI: 10.1088/0256-307X/28/10/108102
Abstract   PDF(pc) (585KB) ( 424 )
Vapor diffusion experiments with different thicknesses of oil barriers are observed by a real-time optical diagnostic system consisting of a Mach–Zehnder interferometer, a microscope and an image processor. Spatiotemporal analysis is first employed to extract the absolute concentration evolution and supersaturation during the entire crystallization process. The nucleation and crystal growth processes are then analyzed. It is found that the crystallization process can be easily classified into four stages in our experiments, according to the analysis of interferograms and the absolute concentration curve. This can help us understand the details of crystal growth. The rule of quality change of crystals with increasing thickness of oil barriers is also analyzed, and could be interpreted by the absolute concentration variation and crystallization phase diagram.
The Fabrication and Characterization of Well Aligned Petal-Like Arsenic-Doped Zinc Oxide Microrods
FENG Qiu-Ju**, JIANG Jun-Yan, TAO Peng-Cheng, LIU Shuang, XU Rui-Zhuo, LI Meng-Ke, SUN Jing-Chang
Chin. Phys. Lett. 2011, 28 (10): 108103 .   DOI: 10.1088/0256-307X/28/10/108103
Abstract   PDF(pc) (674KB) ( 334 )
Arsenic-doped petal-like zinc oxide microrods are grown on silicon (100) substrates by the chemical vapor deposition method without the use of catalysts. Scanning electron microscopy shows that As-doped petal-like ZnO microrods with a preferred c−axial orientation are obtained, which is well in accordance with x-ray diffraction analysis. The obtained ZnO microrods have uniform lengths of about 2 µm and side lengths of about 100 nm. As-related acceptor emissions are observed from photoluminescence spectra of the ZnO microrods at a temperature of 11 K. The acceptor binding energy is estimated to be 128 meV.
The Preparation and Characteristics of InxGa1−xN (0.06≤x≤0.58) Films Deposited by ECR-PEMOCVD
LIU Xing-Long, QIN Fu-Wen, **, BIAN Ji-Ming, ZHANG Dong, CHEN Wei-Ji, ZHOU Zhi-Feng, ZHI An-Bo, YU Bo, WU Ai-Min, JIANG Xin,
Chin. Phys. Lett. 2011, 28 (10): 108104 .   DOI: 10.1088/0256-307X/28/10/108104
Abstract   PDF(pc) (728KB) ( 429 )
We investigate the structural property and surface morphology of InxGa1−xN films for In compositions ranging from 0.06 to 0.58, which are deposited by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The results of x-ray diffraction (XRD) in InGaN films confirm that they have excellent c−axis orientation. The In content in the InGaN epilayers is checked by electron probe microanalysis (EPMA), which reveals that In fractions determined by XRD are in good agreement with the EPMA results. Atomic force microscopy measurements reveal that the grown films have a surface roughness that varies between 4.16 and 8.14 nm. The results suggest that it is possible to deposit high-c-axis-orientation InGaN films with different In contents.
Robust Half-Metallicity in a Chromium-Substituted AlN
S. Arif, Iftikhar Ahmad*, B. Amin, H. A. Rahnamaye Aliabad
Chin. Phys. Lett. 2011, 28 (10): 108501 .   DOI: 10.1088/0256-307X/28/10/108501
Abstract   PDF(pc) (556KB) ( 444 )
We investigate half metallicity in a chromium (Cr)-substituted AlN dilute magnetic semiconductor using the full-potential linearized augmented plane-wave method. Our results show that Al0.75Cr0.25N is half metal and holds a net integer magnetic moment of 3μβ with lattice compression. The half−metallic nature is maintained from the relaxed lattice constant 4.36 Å to 4.09 Å. An abrupt change of the physical properties is observed at a robust transition lattice constant of 4.09 Å, and the material transforms from half metal to metal. We find that up to 6% compression, the material maintains its half-metallic nature. Furthermore, we also confirm that the origin of ferromagnetism in Al0.75Cr0.25N is double exchange.
Cu2SixSn1−xS3 Thin Films Prepared by Reactive Magnetron Sputtering For Low-Cost Thin Film Solar Cells
YAN Chang, LIU Fang-Yang, LAI Yan-Qing**, LI Jie, LIU Ye-Xiang
Chin. Phys. Lett. 2011, 28 (10): 108801 .   DOI: 10.1088/0256-307X/28/10/108801
Abstract   PDF(pc) (659KB) ( 630 )
We report the preparation of Cu2SixSn1xS3 thin films for thin film solar cell absorbers using the reactive magnetron co−sputtering technique. Energy dispersive spectrometer and x-ray diffraction analyses indicate that Cu2Si1xSnxS3 thin films can be synthesized successfully by partly substituting Si atoms for Sn atoms in the Cu2SnS3 lattice, leading to a shrinkage of the lattice, and, accordingly, by 2θ shifting to larger values. The blue shift of the Raman peak further confirms the formation of Cu2SixSn1xS3. Environmental scanning electron microscope analyses reveal a polycrystalline and homogeneous morphology with a grain size of about 200–300 nm. Optical measurements indicate an optical absorption coefficient of higher than 104 cm−1 and an optical bandgap of 1.17±0.01 eV.
A Macroscopic Approach to the Lane Formation Phenomenon in Pedestrian Counterflow
XIONG Tao, ZHANG Peng**, WONG S. C., SHU Chi-Wang, ZHANG Meng-Ping
Chin. Phys. Lett. 2011, 28 (10): 108901 .   DOI: 10.1088/0256-307X/28/10/108901
Abstract   PDF(pc) (985KB) ( 507 )
We simulate pedestrian counterflow by adopting an optimal path-choice strategy and a recently observed speed-density relationship. Although the whole system is symmetric, the simulation demonstrates the segregation and formation of many walking lanes for two groups of pedestrians. The symmetry breaking is most likely triggered by a small numerical viscosity or "noise", and the segregation is associated with the minimization of travel time. The underlying physics can be compared with the "optimal self-organization" mechanism in Helbing's social force model, by which driven entities in an open system tend to minimize their interaction to enable them to reach some ordering state.
Thermal Efficiency for Each Zone of a Solar Pond
BEZ�, R C�, CEK Nalan**, &Scedil, AH�, N &Scedil, ENCAN Arzu
Chin. Phys. Lett. 2011, 28 (10): 108902 .   DOI: 10.1088/0256-307X/28/10/108902
Abstract   PDF(pc) (470KB) ( 1079 )
A salt gradient solar pond with a surface area of 3.5×3.5 m2 and a depth of 2 m is built. Two collapsible covers are used to reduce thermal energy loss from the surface of the solar pond during the night and to increase the thermal efficiency of the pond solar energy harvesting during daytime. The covers can be rotated between 0 and 180° by a controlled electric motor and has insulation and reflection properties. The thermal efficiency for each solar pond zone is investigated theoretically and experimentally.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
The Wave-Like Auroral Structure around Auroral Expansion Onset
TANG Chao-Ling**
Chin. Phys. Lett. 2011, 28 (10): 109401 .   DOI: 10.1088/0256-307X/28/10/109401
Abstract   PDF(pc) (1945KB) ( 322 )
We present the direct connection between the wave-like auroral structure around the time of auroral expansion onset and the ballooning mode waves in the near-Earth magnetotail. Based on the NASA mission time history of events and macroscale interactions during substorms (THEMIS) ground-based all-sky imagers, we show that around the time of auroral expansion onset, a wave-like auroral structure first has four luminosity peaks separated by 2–3° magnetic longitude (MLON). Subsequently, the wave-like structure propagates in the azimuthal direction and an overall bright arc spans approximately 1 h magnetic local time. The wavelength is estimated to be 120–180 km. Finally, a noticeable poleward auroral expansion is observed. The ballooning mode waves are identified by two THEMIS probes in the near-Earth magnetotail. The observed wavelength of the ballooning mode waves is approximately equal to the order of the ion Larmor radius. The wavelength of 1500–3000 km in the near-Earth magnetotail is comparable with the wave-like auroral structure estimate. This study suggests that the ballooning mode waves might play a crucial role in auroral expansion onset, corresponding to the wave-like auroral structure in this study.
Observation of a Sharp Negative Dipolarization Front in the Reconnection Outflow Region
ZHOU Meng, **, HUANG Shi-Yong, DENG Xiao-Hua, PANG Ye,
Chin. Phys. Lett. 2011, 28 (10): 109402 .   DOI: 10.1088/0256-307X/28/10/109402
Abstract   PDF(pc) (773KB) ( 322 )
A sharp dipolarization front (DF) has recently been detected in the Earth's magnetotail and is associated with complex kinetic effects. We present one event where a tailward propagating negative DF (with Bz decreasing sharply to negative value) was observed near a reconnection region. The thickness of the negative DF is comparable with the local ion gyro-radius/inertial length. There is a strong field-aligned current at the front. Electromagnetic whistler wave enhancements are observed around the front, associated with counter-streaming electron beams. We further compare the features of the observed negative DF with the recent kinetic simulation results, as well as the Earthward propagating DFs observed by the THEMIS spacecraft.
Nonthermal Emission of Tycho's Supernova Remnant
TANG Yun-Yong, FANG Jun, ZHANG Li**
Chin. Phys. Lett. 2011, 28 (10): 109501 .   DOI: 10.1088/0256-307X/28/10/109501
Abstract   PDF(pc) (562KB) ( 443 )
The time-dependent non-thermal particle and photon spectra are reproduced for a Type Ia SNR Tycho with radio, x-ray, GeV and TeV emission within the framework of the diffusive shock acceleration of the non-thermal particles. TeV photons can come from the inverse Compton scattering of relativistic electrons and from the π0−decay process in proton-proton interaction. The results show that (1) the hadronic case can model the observed multiwavelength spectrum well and, peculiarly, the π0-decay process appears to be necessary to explain the GeV emission; and (2) magnetic field amplification is vital in the SNR.
Restrictions on Purely Kinetic K-Essence
YANG Rong-Jia, QI Jing-Zhao, YANG Bao-Zhu
Chin. Phys. Lett. 2011, 28 (10): 109502 .   DOI: 10.1088/0256-307X/28/10/109502
Abstract   PDF(pc) (454KB) ( 406 )
We restrict purely kinetic k-essence. Assuming that the equation of state is a power law of the kinetic energy, i.e. w=w0Xα, we find that α must be positive to obtain accelerated phases, constrained from the conditions for stability and causality. In this case the k-essence behaves like a phantom. We also study the evolutions of the equation of state and the speed of sound with numerical simulations.
Extension of Radiative Viscosity to Superfluid Matter
PI Chun-Mei, YANG Shu-Hua**, ZHENG Xiao-Ping
Chin. Phys. Lett. 2011, 28 (10): 109701 .   DOI: 10.1088/0256-307X/28/10/109701
Abstract   PDF(pc) (437KB) ( 291 )
The radiative viscosity of superfluid npe matter is studied and it is found that to the lowest order of δμ/T, the ratio of radiative viscosity to bulk viscosity is the same as that of its normal matter.
COMMENTS AND ERRATA
Withdrawal of Chinese Physics Letters 28 (2011) 043401
WANG Ji-Cheng, ZHOU Ke-Ya, WANG Yue-Yuan, LIAO Qing-Hong, LIU Shu-Tian**
Chin. Phys. Lett. 2011, 28 (10): 109901 .   DOI: 10.1088/0256-307X/28/10/109901
Abstract   PDF(pc) (217KB) ( 307 )
82 articles