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Volume 29 Issue 8
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GENERAL
Explicit Multisymplectic Fourier Pseudospectral Scheme for the Klein–Gordon–Zakharov Equations
CAI Jia-Xiang, and LIANG Hua
Chin. Phys. Lett. 2012, 29 (8): 080201 .   DOI: 10.1088/0256-307X/29/8/080201
Abstract   PDF(pc) (504KB) ( 1043 )

Applying the Fourier pseudospectral method to space derivatives and the symplectic Euler rule to time derivatives in the multisymplectic form of the Klein–Gordon–Zakharov equations, we derive an explicit multisymplectic scheme. The semi-discrete energy and momentum conservation laws are given. Some numerical experiments are carried out to show the accuracy of the numerical solutions. The performance of the scheme in preserving the global energy and momentum conservation laws are also checked.

The Generalized Wronskian Solution to a Negative KdV-mKdV Equation
LIU Yu-Qing, CHEN Deng-Yuan, HU Chao
Chin. Phys. Lett. 2012, 29 (8): 080202 .   DOI: 10.1088/0256-307X/29/8/080202
Abstract   PDF(pc) (428KB) ( 849 )

A negative KdV-mKdV hierarchy is presented through the KdV-mKdV operator. The generalized Wronskian solution to the negative KdV-mKdV equation is obtained. Some soliton-like solutions and a complexiton solution are presented explicitly as examples.

DNA Dynamics Studied Using the Homogeneous Balance Method
E. M. E. Zayed, and A. H. Arnous
Chin. Phys. Lett. 2012, 29 (8): 080203 .   DOI: 10.1088/0256-307X/29/8/080203
Abstract   PDF(pc) (373KB) ( 1037 )
We employ the homogeneous balance method to construct the traveling waves of the nonlinear vibrational dynamics modeling of DNA. Some new explicit forms of traveling waves are given. It is shown that this method provides us with a powerful mathematical tool for solving nonlinear evolution equations in mathematical physics. Strengths and weaknesses of the proposed method are discussed.
Quantum Gate Implementations in the Separated Ion-Traps by Fast Laser Pulses
ZHANG Miao, and WEI Lian-Fu
Chin. Phys. Lett. 2012, 29 (8): 080301 .   DOI: 10.1088/0256-307X/29/8/080301
Abstract   PDF(pc) (775KB) ( 454 )
An approach is proposed to implement the universal quantum gates between the ions confined individually in the separated traps. Instead of the typical adiabatic operations, performed for manipulating the ion-ion coupling, here the switchable couplings between ions are implemented non-adiabatically by using the fast laser pulses. Consequently, the desirable quantum gates between the ions could be implemented by using only a series of laser pulses. The proposal may be conveniently generalized to the quantum computation with the scalable ion-traps.
Approximate Analytical Solution of the Yukawa Potential with Arbitrary Angular Momenta
M. Hamzavi, M. Movahedi, K.-E. Thylwe, and A. A. Rajabi
Chin. Phys. Lett. 2012, 29 (8): 080302 .   DOI: 10.1088/0256-307X/29/8/080302
Abstract   PDF(pc) (447KB) ( 2531 )
The Yukawa potential is often used to compute bound-state normalizations and energy levels of neutral atoms. By using the generalized parametric Nikiforov–Uvarov method, we obtain approximate analytical solutions of the radial Schr?dinger equation for the Yukawa potential. The energy eigenvalues and the corresponding eigenfunctions are calculated in closed forms. Some numerical results are presented and show that these results are in good agreement with those obtained previously by other methods. Also, we find the energy levels of the familiar pure Coulomb potential energy levels when the screening parameter of the Yukawa potential goes to zero.
Controlling Excitation Inversion of a Cooper Pair Box Interacting with a Nanomechanical Resonator
C. Valverde, H. C. B. de Oliveira, A. T. Avelar, and B. Baseia
Chin. Phys. Lett. 2012, 29 (8): 080303 .   DOI: 10.1088/0256-307X/29/8/080303
Abstract   PDF(pc) (769KB) ( 410 )
We investigate the action of time-dependent detunings upon the excitation inversion of a Cooper pair box interacting with a nanomechanical resonator. The method employs the Jaynes–Cummings model with damping, assuming different decay rates of the Cooper pair box and various fixed and time-dependent detunings. It is shown that, when the presence of damping plus constant detunings destroys the collapse/revival effects, convenient choices of time-dependent detunings allow one to reconstruct such events in a perfect way. It is also shown that the mean excitation of the nanomechanical resonator is more robust against damping of the Cooper pair box for convenient values of time-dependent detunings.
Mocking up a Dephasing Channel with a Minimal-Sized Environment
WU Zhen
Chin. Phys. Lett. 2012, 29 (8): 080304 .   DOI: 10.1088/0256-307X/29/8/080304
Abstract   PDF(pc) (498KB) ( 462 )
In order to model the most general quantum operation on a d-dimensional system, a d2-dimensional environment is usually needed. We focus on the quantum dephasing process and find that this channel can be modeled by an environment with the size of at most d dimensions. An experimentally accessible matrix D is defined to characterize the dephasing channel and the minimal number of Kraus operators of the channel from the matrix D for mocking up the dephasing channel is presented in the minimal-sized environment. An experimental simulation of dephasing channels by means of nuclear magnetic resonance techniques is carried out to justify the idea.
Proposed Test of the Equivalence Principle with Rotating Cold Polar Molecules
HU Zhong-Kun, KE Yi, DENG Xiao-Bing, ZHOU Ze-Bing, and LUO Jun
Chin. Phys. Lett. 2012, 29 (8): 080401 .   DOI: 10.1088/0256-307X/29/8/080401
Abstract   PDF(pc) (602KB) ( 13367 )
We propose a novel scheme for testing the equivalence principle with rotating cold polar molecules whose angular momenta are polarized at different states. Molecules in specific rotational states are selected out via the hexapole state-selection technique and the gravitational acceleration g of molecules is measured by measuring the Doppler shift of the molecules free falling in the gravitational field. Some other possible methods of rotating molecules and measuring g are also mentioned. Molecules, as the test masses, have higher rotating speed and smaller dimension in comparison with mechanical gyroscopes and may open a new way for testing the equivalence principle and the possible coupling between rotation and gravity.
Conserved Quantities in f(R) Gravity via Noether Symmetry
M. Farasat Shamir, Adil Jhangeer, and Akhlaq Ahmad Bhatti
Chin. Phys. Lett. 2012, 29 (8): 080402 .   DOI: 10.1088/0256-307X/29/8/080402
Abstract   PDF(pc) (465KB) ( 541 )
We investigate f(R) gravity using the Noether symmetry approach. For this purpose, we consider Friedmann Robertson–Walker (FRW) universe and spherically symmetric spacetimes. The Noether symmetry generators are evaluated for some specific choice of f(R) models in the presence of the gauge term. Further, we calculate the corresponding conserved quantities in each case. Moreover, the importance and stability criteria of these models are discussed.
Casimir–Polder-Like Force for an Atom in Hartle–Hawking Vacuum outside a Schwarzschild Black Hole
ZHANG Jia-Lin, and YU Hong-Wei
Chin. Phys. Lett. 2012, 29 (8): 080403 .   DOI: 10.1088/0256-307X/29/8/080403
Abstract   PDF(pc) (435KB) ( 403 )
We calculate the energy level shift of a static ground state two-level atom interacting with fluctuating massless scalar fields in the Hartle–Hawking vacuum outside a Schwarzschild black hole. It is found that the energy level shift is position-dependent and gives rise to a force on the atom besides the classical gravitational force. This force behaves like r?1(r?2M)?1 for r approaching 2M, whereas it behaves like r?2 for large r.
LRS Bianchi Type-II Inflationary Universe with Massless Scalar Field and Time Varying Λ
Raj Bali, and Swati
Chin. Phys. Lett. 2012, 29 (8): 080404 .   DOI: 10.1088/0256-307X/29/8/080404
Abstract   PDF(pc) (431KB) ( 384 )
The locally rotationally symmetric (LRS) Bianchi type-II inflationary cosmological model is investigated for massless scalar field with flat potential and time varying Λ. To obtain the deterministic solution, it is assumed that scale factor is a(t)~eHt as we considered previously for Bianchi type-I spacetime and Λa?2 as considered by Chen and Wu, where H is the Hubble constant and effective potential V(φ)=const; φ Higg's field. It is shown that such a time varying Λ leads to no conflict with existing observations. However, it does change the predictions of standard cosmology in the matter-dominated phase and alleviates some problems in reconciling observations with the inflationary scenario. The model represents anisotropic spacetime in general. However, the model isotropizes for large values of t and β=3H2, where β is constant. The physical and geometrical aspects of the model in the context of an inflationary scenario is also discussed.
Ground State Energy of 1D Attractive δ-Function Interacting Fermi Gas
WANG Ya-Hui, and MA Zhong-Qi
Chin. Phys. Lett. 2012, 29 (8): 080501 .   DOI: 10.1088/0256-307X/29/8/080501
Abstract   PDF(pc) (414KB) ( 440 )
The ground state energy of one-dimensional two-component Fermi gas with the attractive δ-function interaction is fitted with a simple approximate function.
Modified Static Floor Field and Exit Choice for Pedestrian Evacuation
XU Yan, HUANG Hai-Jun, and YONG Gui
Chin. Phys. Lett. 2012, 29 (8): 080502 .   DOI: 10.1088/0256-307X/29/8/080502
Abstract   PDF(pc) (513KB) ( 559 )
An improved floor field model is proposed to simulate the pedestrian evacuation behavior in a room with multiple exits by modifying the static floor field. The modified static floor field is determined additionally by two cognitive coefficients of exit width and congestion degree around the exits. The logit-based discrete choice principle is used to govern the initial exit selection strategy based on the modified static floor field in such a scenario that pedestrians are distributed in the room's specified zone. Simulation results show that the proposed model can better perform the evacuation process. Sensitivity analyses of the model parameters are also presented.
Dynamics of a Cortical Neural Network Based on a Simple Model
QU Jing-Yi, and WANG Ru-Bin
Chin. Phys. Lett. 2012, 29 (8): 080503 .   DOI: 10.1088/0256-307X/29/8/080503
Abstract   PDF(pc) (1248KB) ( 400 )
The collective dynamics of a randomly connected neuronal network motivated by the anatomy of a mammalian cortex based on a simple model are studied. This simple model can not only reproduce the rich behaviors of biological neurons but also has only two equations and one nonlinear term. By varying some key parameters, such as the connection weights of neurons, the external current injection and the noise of intensity, this neuronal network will exhibit various collective behaviors. It is demonstrated that the synchronization status of the neuronal network has a strong relationship with the key parameters and the external current has more influence on the spiking of inhibitory neurons than that of excitatory neurons. These results may be instructive in understanding the collective dynamics of a mammalian cortex.
A Statistical Model for Predicting Thermal Chemical Reaction Rate: Application to Bimolecule Reactions
LI Wang-Yao, LIN Zheng-Zhe, XU Jian-Jun, and NING Xi-Jing
Chin. Phys. Lett. 2012, 29 (8): 080504 .   DOI: 10.1088/0256-307X/29/8/080504
Abstract   PDF(pc) (834KB) ( 538 )
A model based on the statistics of individual atoms [Europhys. Lett. 94 (2011) 40002], which has been successfully applied to predict the rate constant of unimolecular reactions, was further extended to bimolecular reactions induced by collisions. Compared with the measured rate constants of the reactions S+SO2→SO+SO and NH3+Cl→NH2+HCl, the model is proved to be significantly better than conventional transition state theory. In order to strictly test the model, we perform molecular dynamics simulation of C60+C60→C120, and show that the rate constants are in excellent agreement with our model but far away from the transition state theory.
Improvement on AMS Measurement of 236U at CIAE
WANG Xiang-Gao, HE Ming, DONG Ke-Jun, and JIANG Shan
Chin. Phys. Lett. 2012, 29 (8): 080701 .   DOI: 10.1088/0256-307X/29/8/080701
Abstract   PDF(pc) (563KB) ( 445 )
In order to improve the detection efficiency and sensitivity for 236U measurement at China Institute of Atomic Energy (CIAE) accelerator mass spectrometry (AMS) system to meet the requirement of some applications, we present some new improvements of the measurement method for AMS measurement of 236U at CIAE AMS. The main features of the method include: (i) measurement optimization; (ii) improvement of the TOF time resolution ~500 ps. Based on these improvements, the sensitivity is ~10?11 for 236U/238U in the present work, higher than before (236U/238U~5×10?10).
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Photoproduction of J/ ψ in pp and PbPb Collisions at Leading Order
ZHU Jia-Qing, and LI Yun-De
Chin. Phys. Lett. 2012, 29 (8): 081301 .   DOI: 10.1088/0256-307X/29/8/081301
Abstract   PDF(pc) (616KB) ( 350 )
The production of J/ ψ originating from photoproduction processes in pp and PbPb collisions at leading order is calculated. We use the color singlet and color octet mechanisms for heavy quarkonium production to deal with the direct photon processes, and consider fragmentation processes. The shadowing and iso-spin of the nucleus are also considered in our calculation. The numerical results show that the modification of photoproduction processes for J/ψ production becomes obvious in the large pT region at LHC energy.
NUCLEAR PHYSICS
New Measurements for 8He Excited States
XIAO Jun, YE Yan-Lin, CAO Zhong-Xin, JIANG Dong-Xing, ZHENG Tao, HUA Hui, LI Zhi-Huan, LI Xiang-Qing, GE Yu-Cheng, LOU Jian-Ling, PANG Dan-Yang, LV Lin-Hui, LI Qi-Te, QIAO Rui, YOU Hai-Bo, CHEN Rui-Jiu, H. Sakurai, H. Otsu, M. Nishimura, S. Sakaguchi, H. Baba, Y. Togano, K. Yoneda, LI Chen, WANG Shuo, WANG He, LI Kuo-Ang, Y. Nakayama, Y. Kondo, S. Deguchi, Y. Satou, and K. H. Tshoo
Chin. Phys. Lett. 2012, 29 (8): 082501 .   DOI: 10.1088/0256-307X/29/8/082501
Abstract   PDF(pc) (604KB) ( 428 )
Breakup reactions of the double borromean nucleus 8He were measured at 82.3 MeV/u on CH2 and C targets. The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are realized in this experiment. The relative energy spectrum for 8He was reconstructed with good statistics. The spectrum exhibits a structure of two resonant peaks, one at an excitation energy of about 3.0 and the other at about 4.14 MeV, respectively. Substantially larger cross section for the first resonance is observed in comparison to the results reported previously.
ATOMIC AND MOLECULAR PHYSICS
Temporal Electronic Structures of Nonresonant Raman Excited Virtual States of P-Hydroxybenzoic Acid
FANG Chao, and SUN Li-Feng
Chin. Phys. Lett. 2012, 29 (8): 083301 .   DOI: 10.1088/0256-307X/29/8/083301
Abstract   PDF(pc) (485KB) ( 370 )
An algorithm is employed to calculate molecular bond polarizabilities of p-hydroxybenzoic acid, which supplies essential electronic information of the nonresonant Raman excited virtual states. The main dynamical behavior of the excited virtual states of p-hydroxybenzoic acid with 514.5 nm excitation is such that the Raman excited electrons tend to flow to the C–C connected with –OH and –COOH from the benzene ring because of the electronic repulsion effect. The distribution of the electrons at the final stage of relaxation is given out through the comparison between the bond electronic densities of the ground states and the bond polarizabilities after de-excitation. Furthermore, the relaxation characteristic times of bond polarizabilities shows that the transport of electrons on –COOH is distinct.
Transition Spectrum Intensities and Absorption Coefficients of Hydride BH2 Free Radical Molecule
WU Dong-Lan, TAN Bin, ZHANG Xin-Qin, and XIE An-Dong
Chin. Phys. Lett. 2012, 29 (8): 083302 .   DOI: 10.1088/0256-307X/29/8/083302
Abstract   PDF(pc) (631KB) ( 347 )
We build a partition function model by product approximation first, then put the normal temperature calculated by moment square RV2, which has no rotational transition, approximately as a constant and applied to high temperature, and lastly program the compiler and compute the spectral line intensities and absorption coefficients of the 001-000 band for the hydride BH2 free radical molecule at several temperatures. The results show that the calculated values of total partition function agree with the data obtained from Gauss calculations and the fitted values by five factorial polynomials. Such excellent agreement has made it feasible to calculate the spectral line intensities and absorption coefficients at different temperatures. From the spectral figures at different temperatures, we find that they accord with the spectrum characteristic of asymmetric top molecules in some literature. This analysis has significance in measuring the high-temperature spectrum intensities of radical molecules by experiment.
Self-Consistent Approach for Mapping Interacting Systems in Continuous Space to Lattice Models
WU Biao, XU Yong, DONG Lin, and SHI Jun-Ren
Chin. Phys. Lett. 2012, 29 (8): 083701 .   DOI: 10.1088/0256-307X/29/8/083701
Abstract   PDF(pc) (563KB) ( 470 )
We propose a general variational principle for mapping the interacting systems in continuous space to lattice models. Based on the principle, we derive a set of self-consistent nonlinear equations for the Wannier functions (or, equivalently for the Bloch functions). These equations show that the Wannier functions can be strongly influenced by the interaction and be significantly different from their non-interacting counterparts. The approach is demonstrated with interacting bosons in an optical lattice, and illustrated quantitatively by a simple model of interacting bosons in a double well potential. It is shown that the so-determined lattice model parameters can be significantly different from their non-interacting values.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Self-Similar Vortex Solitons for the Distributed-Coefficient Nonlinear Schrödinger Equation
ZHAO Bi, DAI Chao-Qing, and ZHANG Jie-Fang
Chin. Phys. Lett. 2012, 29 (8): 084201 .   DOI: 10.1088/0256-307X/29/8/084201
Abstract   PDF(pc) (2476KB) ( 523 )
Via the similarity transformation method, we obtain an approximate vortex solution to the generalized (2+1)-dimensional nonlinear Schr?dinger equation with space-dependent diffraction, nonlinearity and gain/loss coefficients. Under certain parametric conditions, we investigate the propagation dynamics of self-similar vortex solitons in optical media.
Advanced Aperture Synthesis by Wave-Front Combination in Generalized Phase-Shifting Interferometry
XU Xian-Feng, CAI Lü-Zhong, LU Guang-Can, HAN Guo-Xia, TIAN Yan-Jie, ZHANG Qian, and JIAO Zhi-Yong
Chin. Phys. Lett. 2012, 29 (8): 084202 .   DOI: 10.1088/0256-307X/29/8/084202
Abstract   PDF(pc) (564KB) ( 428 )
An approach to improve the image quality by aperture synthesis in generalized phase-shifting interferometry is proposed. The aperture of the holographic system is enlarged by increasing the recording area to receive a more diffusive spectrum by moving a singular CCD. The sub-object wave fronts are combined with the index of their intensities. This method can avoid the negative effect of environmental disturbance and improve the synthesis efficiency by hundreds of times. The optical experiments have shown that it is simple and robust to stitch the complex object wave front accurately and to improve the imaging quality greatly, especially for the recording of large scale objects.
All-Optical Time Slot Interchange Using a Cascaded Optical Buffer
FENG Zhen, SHENG Xin-Zhi, WU Chong-Qing, LI Zheng-Yong, and MAO Ya-Ya
Chin. Phys. Lett. 2012, 29 (8): 084203 .   DOI: 10.1088/0256-307X/29/8/084203
Abstract   PDF(pc) (663KB) ( 413 )
A novel scheme of all-optical time slot interchanger employing two cascaded re-circulating optical buffers based on nonlinear polarization rotation in semiconductor optical amplifiers is proposed. The experimental system exhibits full interchangeable capability on three 512-bit packets at 10 Gbits/s. Theoretically, each packet length is up to 123 ns with the maximum buffer depth 30%.
Fabrication and Characterization of a 2×2 Microfiber Knot Resonator Coupler
A. A. Jasim, A. Z. Zulkifli, M. Z. Muhammad, H. Ahmad, and S. W. Harun
Chin. Phys. Lett. 2012, 29 (8): 084204 .   DOI: 10.1088/0256-307X/29/8/084204
Abstract   PDF(pc) (471KB) ( 592 )
A 2×2 microfiber knot resonator (MKR) coupler is demonstrated. The hybrid device is obtained by forming a knot within the coupling region of a microfiber coupler with a 50:50 splitting ratio. The microfiber coupler is successfully fabricated by laterally fusing and tapering two optical fibers using a flame-brushing technique. The coupler has an overlapping length of 40 mm with a uniform waist of around 5 μm . With an MKR structure, the coupler produces a resonant response at both output ports. The free spectral range of the output spectrum from both ports is obtained at 0.2 nm at a knot diameter of 260 μm . The resonance extinction ratio of the device varies from 2 to 6 dB while the calculated Q factor and finesse are ~25646 and 3.3, respectively, at both output ports.
A Compact Low Noise Single Frequency Linearly Polarized DBR Fiber Laser at 1550 nm
ZHANG Wei-Nan, LI Can, MO Shu-Pei, YANG Chang-Sheng, FENG Zhou-Ming, XU Shan-Hui, SHEN Shao-Xiong, PENG Ming-Ying, ZHANG Qin-Yuan, and YANG Zhong-Min
Chin. Phys. Lett. 2012, 29 (8): 084205 .   DOI: 10.1088/0256-307X/29/8/084205
Abstract   PDF(pc) (589KB) ( 548 )
A compact low noise single frequency linearly polarized distributed Bragg reflector (DBR) fiber laser based on a 1.4-cm-long homemade Er3+/Yb3+-codoped phosphate single mode glass fiber has been demonstrated. An over 50 mW stable single frequency linearly polarized fiber laser was achieved. The measured slope efficiency is more than 21.6%, and the signal-to-noise ratio (SNR) is higher than 65 dB and the laser linewidth is less than 2.0 kHz. The laser RIN is measured to be less than ?150 dB/Hz at the frequencies over 2.0 MHz, and the obtained linear polarization extinction ratio (LPER) is more than 30 dB.
A 1342-nm Passively Mode-Locked Picosecond Oscillator with a Semiconductor Saturable Absorber Mirror
NIU Gang, YAN Ying, MA Yun-Feng, SHI Zhao-Hui, HUANG Yu-Tao, WANG Lu-Lu, SONG Ya-Li, FAN Zhong-Wei, Mikhail Grishin, Donatas Joksas, and Zenonas Kuprionis
Chin. Phys. Lett. 2012, 29 (8): 084206 .   DOI: 10.1088/0256-307X/29/8/084206
Abstract   PDF(pc) (596KB) ( 464 )
A 1342-nm oscillator was successfully demonstrated by using a semiconductor saturable absorber mirror with the repetition rate of 65 MHz. The output coupler with appropriate transmission was chosen to suppress Q-switched mode-locking. At the pumping power of 1.7 W, the stable continuous-wave mode locked pulse was observed. The average output power was 140 mW and pulse width was measured to be 17.2 ps.
Effect of Oxygen Vacancy on the Band Gap and Nanosecond Laser-Induced Damage Threshold of Ta2O5 Films
XU Cheng, YANG Shuai, WANG Ji-Fei, NIU Ji-Nan, MA Hao, QIANG Ying-Huai, LIU Jiong-Tian, LI Da-Wei, and TAO Chun-Xian
Chin. Phys. Lett. 2012, 29 (8): 084207 .   DOI: 10.1088/0256-307X/29/8/084207
Abstract   PDF(pc) (1334KB) ( 778 )
Ta2O5 films are deposited on fused silica substrates by electron beam evaporation method. The optical property, x-ray photoelectron spectroscopy, band gap and nanosecond laser-induced damage threshold (LIDT) of the films before and after annealing are studied. It is found that the existence of an oxygen vacancy results in the decrease of the transmittance, refractive index, both macroscopic band gap and microscopic band gap, and the LIDT of Ta2O5 films. If the oxygen vacancy forms, the macroscopic band gap decreases 2%. However, when the oxygen vacancy forms the microscopic band gap decreases 73% for crystalline Ta2O5 and 77% for amorphous Ta2O5. The serious decrease of microscopic band gap may significantly increase the absorbance of the micro-area in Ta2O5 films when irradiated by laser, thus the damage probability increases. It is consistent with our experimental results that the LIDT of the as-deposited Ta2O5 films is 7.3 J/cm2, which increases 26% to 9.2 J/cm2 when the oxygen vacancy is eliminated after annealing.
Single-Fundamental-Mode 850 nm Surface Relief VCSEL
WEI Si-Min, XU Chen, DENG Jun, ZHU Yan-Xu, MAO Ming-Ming, XIE Yi-Yang, XU Kun, CAO Tian, and LIU Jiu-Cheng
Chin. Phys. Lett. 2012, 29 (8): 084208 .   DOI: 10.1088/0256-307X/29/8/084208
Abstract   PDF(pc) (887KB) ( 895 )
The performance of the oxide-confined surface-relief (SR) structure vertical-cavity surface-emitting laser (VCSEL) is simulated and analyzed by using the three-dimensional finite-difference time-domain (FDTD) method. The impacts of the device structure parameters on the far-field characteristics are researched. A single-fundamental-mode SR VCSEL with an oxide-aperture of 15 μm is designed and produced. The single-mode power of the VCSEL is 5 mW, the threshold current is 2.5 mA, far-field divergent angles range from 7.8° to 10.8° and the side-mode suppression ratio is over 30 dB. The optical and electrical properties of the device are in agreement with the results of FDTD simulation, which shows that the SR technology can effectively suppress the higher-order-mode lasing, and make the SR VCSEL work in a single mode under a larger oxide aperture.
Quantum Information Transfer Based on Frequency Modes in Circuit QED
WANG Chao-Quan
Chin. Phys. Lett. 2012, 29 (8): 084209 .   DOI: 10.1088/0256-307X/29/8/084209
Abstract   PDF(pc) (403KB) ( 474 )
We propose a scheme for implementing quantum information transfer based on frequency modes of microwave photons in a superconducting circuit. In our proposal, quantum information can be encoded on frequency modes of microwave photons, which act as a qubit in the resonator. Operations for the qubit, which is a process involving parametric frequency conversion, can be implemented by adjusting biased-dc superconducting quantum interference (SQUID). The coupling between two resonators can be controlled by tuning the frequency of the LC circuit inserted by a dc SQUID with two Josephson-junctions (2JJ-SQUID). Compared with previous ones, our work can avoid dephasing and decoherence resulting from atom decay. In addition, the resonator which includes multiple photons in two frequency modes can play a role of an identical atomic ensemble, which could lead to photon blockade.
Single-Mode Propagation and Highly Efficient Second Harmonic Generation in Periodically Poled MgO-Doped LiNbO3 on Insulator Rib Waveguide
ZHOU Yu-Jie, FENG Li-Qun, and SUN Jun-Qiang
Chin. Phys. Lett. 2012, 29 (8): 084210 .   DOI: 10.1088/0256-307X/29/8/084210
Abstract   PDF(pc) (591KB) ( 480 )
Theoretical studies on mode propagation and second harmonic generation in periodically poled MgO-doped LiNbO3 on an insulator (PPLNOI) rib waveguide are presented. With a special design, the waveguide can simultaneously support the single-mode propagation of both a pump wave (1550 nm) and a second harmonic wave (775 nm). As a result of the strong confinement and intensive nonlinear effect in the PPLNOI rib waveguide, the calculated results indicate that a second-harmonic generation conversion efficiency of 400%W?1?cm?2 can be achieved at a wavelength of 1550 nm, almost 2.6 times higher than the widely applied reverse proton-exchanged waveguide (150%W?1?cm?2).
Two-Dimensional Nonlinear Laser Spectra Calculations with Numerical Path Integral
LIANG Xian-Ting
Chin. Phys. Lett. 2012, 29 (8): 084211 .   DOI: 10.1088/0256-307X/29/8/084211
Abstract   PDF(pc) (639KB) ( 411 )
Two-dimensional three-order nonlinear response functions and the laser spectra of the two-level Frenkel-exciton model, interacting with three short laser pulses in direction ?k1+k2+k3, are calculated using the numerical path integral. The method is non-Markovian and the results show that the numerical simulation scheme provides a new pathway for theoretically investigating the multidimensional ultrafast laser spectra including the non-Markovian effects.
Two-Dimensional Optical Lattice Solitons in Photovoltaic-Photorefractive Crystals
GUO Jian-Bang, LU Ke-Qing, NIU Ping-Juan, YU Li-Yuan, and XING Hai-Ying
Chin. Phys. Lett. 2012, 29 (8): 084212 .   DOI: 10.1088/0256-307X/29/8/084212
Abstract   PDF(pc) (607KB) ( 508 )
We study two families of two-dimensional bright lattice solitons in photovoltaic-photorefractive crystals. It is shown that self-focusing and self-defocusing lattice solitons are possible only when their power level exceeds a critical threshold. It is found that self-focusing lattice solitons exist not only in the semi-infinite band gap, but also in the first band gap, whereas self-defocusing lattice solitons exist only in the first band gap. The structures of these lattice solitons are also analyzed. Our results indicate that a self-focusing lattice soliton in the semi-infinite band gap is more confined than in the first band gap so its tails in the first band gap occupy many lattice sites; when a self-defocusing lattice soliton is close to the second band, the self-defocusing lattice soliton is more confined so its tails occupy a few lattice sites.
Characteristics Improvement of L-Band Superfluorescent Fiber Source Using Unpumped Erbium-Doped Fiber
WANG Xiu-Lin, HUANG Wen-Cai, and CAI Zhi-Ping
Chin. Phys. Lett. 2012, 29 (8): 084213 .   DOI: 10.1088/0256-307X/29/8/084213
Abstract   PDF(pc) (553KB) ( 421 )
An effective method for the improvement of the characteristics of an erbium-doped L-band superfluorescent fiber source (SFS) is demonstrated using an unpumped erbium-doped fiber (EDF). With a suitable length of unpumped EDF section in the single-forward pumped configuration, broadening of the L-band spectral linewidth is achieved and the variation of mean wavelength versus pump power is eliminated. A mean wavelength stable L-band SFS with a spectral linewidth of 50.2 nm and an output power of 60.2 mW is obtained experimentally. The method of using unpumped EDF enables one to offer a stable and wideband L-band SFS with high flexibility and to overcome the shortcomings of the synchronous pumping technique.
Radially and Azimuthally Polarized Beams Generated by a Composite Spiral Zone Plate
HUA Yi-Lei, WANG Zi-Qiang, LI Hai-Liang, GAO Nan, and DU Yu-Chan
Chin. Phys. Lett. 2012, 29 (8): 084214 .   DOI: 10.1088/0256-307X/29/8/084214
Abstract   PDF(pc) (1641KB) ( 888 )
We present a diffractive method for obtaining azimuthal and radially polarized beams. This method involves a modified half-wave plate, a composite spiral zone plate, a pinhole and a lens. Two composite spiral zone plates are combined and assisted by a pinhole and a lens, to transform a circularly polarized beam into a radially polarized or an azimuthal polarized beam. This method is investigated numerically using diffraction theory. The field distributions on the focal spot of the composite spiral zone plates and the output cylindrical beams are calculated. Finally, the use of this method to generate cylindrical vector beams is validated.
Refractive Index Profiles of Copper Ion Exchange Glass Planar Waveguides
XIA Hong-Yun, TENG Chuan-Xin, ZHAO Xiao-Wei, and ZHENG Jie
Chin. Phys. Lett. 2012, 29 (8): 084215 .   DOI: 10.1088/0256-307X/29/8/084215
Abstract   PDF(pc) (752KB) ( 535 )
Glass planar optical waveguides are fabricated by the copper ion-exchange technique. The refractive index (RI) profiles of waveguides are reconstructed by the inverse Wentzel–Kramers–Brillouin (IWKB) method. Cu+ and Cu2+ ion concentrations are calculated by solving the diffusion equation, and the mechanism of RI changes is analyzed. The model between the RI and ion concentrations is proposed by taking both Cu+ and Cu2+ into account, according to polarizability changes among Cu+, Cu2+ and Na+. The results show that the contribution of Cu2+ is not negligible, and the reason for the RI change is of Cu+ and Cu2+. With the exchange time increasing, the redox process between Cu+ and Cu2+ will play an important role on RI profiles.
A Lens Assisted Phase Microscope Based on Ptychography
PAN Xing-Chen, LIN Qiang, LIU Cheng, and ZHU Jian-Qiang
Chin. Phys. Lett. 2012, 29 (8): 084216 .   DOI: 10.1088/0256-307X/29/8/084216
Abstract   PDF(pc) (1498KB) ( 492 )
Based on the recently developed ptychographical iterative engine (PIE), we suggest a lens assisted microscopy to realize quantitative phase imaging without using interferometry. The sample is imaged with a lens system; a pinhole on the image plane scans the image at a proper step interval; the diffraction pattern is recorded simultaneously by a CCD at Fresnel area. With a slightly changed PIE algorithm, the phase image of the sample can be accurately reconstructed from the recorded diffraction pattern. The main advantage of this suggested method lies in its capability to retrieve the phase information from the recorded intensity directly, and thus it has more flexibility over conventional interferometric techniques. The feasibility of the suggested method is verified by reconstructing the modulus and phase image of a biological sample from a set of 10 by 10 diffraction patterns, and the result matches the analysis well.
Swept Frequency Measurement of Electrooptic Phase Modulators Using Dispersive Fibers
ZHANG Shang-Jian, ZHANG Xiao-Xia, and LIU Yong
Chin. Phys. Lett. 2012, 29 (8): 084217 .   DOI: 10.1088/0256-307X/29/8/084217
Abstract   PDF(pc) (691KB) ( 504 )
A novel method based on the use of dispersive fibers is proposed and experimentally demonstrated for measuring the high-frequency modulation index, as well as the half-wave voltage, of electro-optic phase modulators. Fiber dispersion causes the phase modulated signal to become intensity modulated, which allows for the high resolution swept frequency measurement of phase modulators, using a vector network analyzer. The proposed method holds without the restriction of small-signal approximation, which is applicable for the measurement at different driving levels and operating wavelengths.
Group Invariant Solutions of the Two-Dimensional Elastodynamics Problem in the Polar Coordinate System
LI Hou-Guo, and HUANG Ke-Fu
Chin. Phys. Lett. 2012, 29 (8): 084601 .   DOI: 10.1088/0256-307X/29/8/084601
Abstract   PDF(pc) (1061KB) ( 393 )
Some group invariant solutions of the two-dimensional elastodynamics problem in linear homogeneous isotropic materials are considered using the group-theoretical method. In the polar coordinate system, three group invariant solutions are constructed by the invariants of the Lie group, which are admitted by the governing equations for the two-dimensional elastodynamics problem. The graphical figures of the group invariant solutions are presented, and the physical meanings of the group invariant solutions are expounded in some cases.
Global Stability Analysis of Flow Past Two Side-by-Side Circular Cylinders at Low Reynolds Numbers by a POD-Galerkin Spectral Method
ZHANG Wei, and CHEN Cheng
Chin. Phys. Lett. 2012, 29 (8): 084701 .   DOI: 10.1088/0256-307X/29/8/084701
Abstract   PDF(pc) (1449KB) ( 539 )
A proper orthogonal decomposition (POD) method is applied to the problem of a two-dimensional flow past two side-by-side circular cylinders. Based on the POD bases, which are constructed by a snapshot method, a low-dimensional model is established for representing two-dimensional incompressible Navier–Stokes equations. Coupled with the low-dimensional model, the Chiba method is used to analyze the global stability of the basic flow. Different bifurcation paths at three major regions are revealed, in good agreement with the available results by other methods. However, the computation amount in the POD method is low, which shows the availability and advantage of the POD method.
Flow Visualization of Supersonic Flow over a Finite Cylinder
WANG Deng-Pan, ZHAO Yu-Xin, XIA Zhi-Xun, WANG Qing-Hua, and LUO Zhen-Bing
Chin. Phys. Lett. 2012, 29 (8): 084702 .   DOI: 10.1088/0256-307X/29/8/084702
Abstract   PDF(pc) (5446KB) ( 959 )
The flow structures of a supersonic flow over a cylinder with a finite height are investigated using the method of flow visualization with nanoparticle-based planar laser scattering (NPLS), in a supersonic quiet wind tunnel at Ma=2.68. The complex structures of shock waves and three-dimensional vortices in a supersonic flow over a finite cylinder are visualized. Based on the time correlation of NPLS images, the time-space evolutionary characteristics of the coherent structures in a supersonic flow over a finite cylinder are studied, and the evolutionary characteristics of the coherent structure in the flow direction are obtained, which are used to identify the model and rotation direction of shedding vortices.
Flow Patterns in the Sedimentation of a Capsule-Shaped Particle
NIE De-Ming, LIN Jian-Zhong, and ZHANG Kai
Chin. Phys. Lett. 2012, 29 (8): 084703 .   DOI: 10.1088/0256-307X/29/8/084703
Abstract   PDF(pc) (917KB) ( 397 )
The main objective of this study is to numerically investigate the settling of a capsule-shaped particle in an infinitely long channel by the newly developed LB-DF/FD method. This work will focus on the effects of the particle orientation and particle/fluid density ratio on the flow patterns during sedimentation. As the density ratio is varied, our results show that there are four distinct modes of sedimentation: vertical sedimentation, horizontal sedimentation, periodically oscillating sedimentation and chaotic mode where the particle is released from the center of the domain with an initial inclination of π/4 to break the symmetry. Furthermore, we also numerically investigate the flow patterns where the particle is released with an initial inclination of 0, π/6, π/3 and π/2. We conduct a detailed study on the effects of density ratio on the transition from the vertical sedimentation mode to horizontal sedimentation mode.
A Variant of the Classical Von Kármán Flow for a Couple Stress Fluid
A. A. Farooq, A. M. Siddiqui, M. A. Rana, and T. Haroon
Chin. Phys. Lett. 2012, 29 (8): 084704 .   DOI: 10.1088/0256-307X/29/8/084704
Abstract   PDF(pc) (466KB) ( 522 )
We present an attempt to study the influence of couple stresses on the flow induced by an infinite disk rotating with a constant angular velocity. The governing equations of motion in three dimensions are treated analytically yielding the derivation of exact solutions which differ from those corresponding to the classical Von Kármán's flow. The analysis reveals that a boundary layer structure develops near the surface of the disk, whose far-field behaviour is distinct from the near-wall solution. The velocity and vorticity components for various values of the dimensionless parameters, associated with the flow, are presented graphically.
On the Exact Solution for Axisymmetric Flow and Heat Transfer over a Nonlinear Radially Stretching Sheet
Azeem Shahzad, Ramzan Ali, and Masood Khan
Chin. Phys. Lett. 2012, 29 (8): 084705 .   DOI: 10.1088/0256-307X/29/8/084705
Abstract   PDF(pc) (482KB) ( 863 )
We investigate the boundary-layer flow and heat transfer of a magnetohydrodynamic viscous fluid over a nonlinear radially porous stretching sheet within a porous medium. The flow is generated due to a nonlinear stretching sheet and influenced by a continuous suction/blowing of the fluid through the porous sheet. The governing momentum and thermal boundary layer equations are converted into ordinary differential equations by appropriate similarity transformations. The exact solution for the velocity and the temperature fields are derived in the form of an incomplete Gamma function. Also analytic solutions are found by the homotopy analysis method. The graphical results for velocity and temperature fields are presented and discussed. Further, the numerical values of the skin friction coefficient and the Nusselt number are calculated and discussed.
Dynamic Analysis of the Smooth-and-Discontinuous Oscillator under Constant Excitation
TIAN Rui-Lan, WU Qi-Liang, LIU Zhong-Jia, and YANG Xin-Wei
Chin. Phys. Lett. 2012, 29 (8): 084706 .   DOI: 10.1088/0256-307X/29/8/084706
Abstract   PDF(pc) (1547KB) ( 543 )
The effects of constant excitation on the recently proposed smooth-and-discontinuous (SD) oscillator are investigated, which may lead to the variation of equilibrium and the property of phase portrait. By solving a quartic algebraic equation, the transition set and bifurcation for SD oscillator under constant excitation (CSD) are presented, while the number of equilibria depends on the values of the smoothness parameter and the constant excitation. Complicated structures of Kolmogorov–Arnold–Moser (KAM) structures on the Poincaré section are depicted for the driven system without dissipation. Chaotic behaviour is also demonstrated numerically for the system perturbed by both viscous-damping and external excitation. The results show that CSD is an unsymmetrical system that displays different dynamical behaviours from an SD oscillator and will enrich the range of the SD oscillator in research and application.
Applications of the CE/SE Scheme to Incompressible Viscous Flows in Two-Sided Lid-Driven Square Cavities
YANG Duo-Xing, and ZHANG De-Liang
Chin. Phys. Lett. 2012, 29 (8): 084707 .   DOI: 10.1088/0256-307X/29/8/084707
Abstract   PDF(pc) (865KB) ( 463 )
The spacetime conservation element-solution element (CE/SE) method is extended to two-dimensional incompressible viscous flow in a two-sided lid-driven square cavity. Based on the SIMPLE method concept, the preconditioned dual-time scheme is introduced for unsteady computations. The CE/SE-based code is validated by simulating one-sided lid-driven cavity flows. The two-sided lid-driven square cavity problem involves several interesting characteristics being successfully predicted, including development of a pair of off-corner vortices and a free shear layer in the case of parallel wall motion, as well as the appearance of corner vortices for lower Reynolds numbers in the case of anti-parallel motion of the walls. It is found that both the Reynolds number and the direction of the moving walls affect the fluid flow in the cavity.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Mode Conversion and Whistler Wave Generation on an Alfvén Resonance Layer in High Beta Plasmas
LUAN Qi-Bin, SHI Yi-Peng, and WANG Xiao-Gang
Chin. Phys. Lett. 2012, 29 (8): 085201 .   DOI: 10.1088/0256-307X/29/8/085201
Abstract   PDF(pc) (431KB) ( 487 )
Alfvén resonance in high beta plasmas is studied with a five-field model based on the two-fluid theory. The mode conversion and low frequency oblique whistler wave generation are found in the resonance layer. Properties of wave propagation, polarity, and interaction with charged particles are also investigated.
K-Shell Spectra from CH Foam Tamped Ti Layers Irradiated with Nanosecond Laser Pulses
ZHAO Yang, ZHU Tuo, WEI Min-Xi, XIONG Gang, SONG Tian-Ming, HU Zhi-Min, HUANG Cheng-Wu, SHANG Wan-Li, YANG Guo-Hong, ZHANG Ji-Yan, and YANG Jia-Min
Chin. Phys. Lett. 2012, 29 (8): 085202 .   DOI: 10.1088/0256-307X/29/8/085202
Abstract   PDF(pc) (837KB) ( 417 )
Hot dense titanium plasma was produced by irradiating a CH foam coated titanium layer with nanosecond laser pulses. The time-integrated emission spectra of He-like titanium were measured by using an absolutely calibrated flat crystal spectrometer. The synthetic spectra obtained by the steady collisional-radiative (CR) equilibrium model associated with the hydrodynamic simulations were compared with the experimental spectra. The results show that the electron density increases up to 5×1021 cm?3 with CH foam of density 40 mg/cc. This work indicates that an overlay of CH foam on a solid target is beneficial to create an optimum condition for K-shell emissions from a high density plasma region.
Combining Effects between LHW and IBW Injections on EAST
DUAN Wen-Xue, MA Zhi-Wei, and WU Bin
Chin. Phys. Lett. 2012, 29 (8): 085203 .   DOI: 10.1088/0256-307X/29/8/085203
Abstract   PDF(pc) (470KB) ( 359 )
The quasilinear combining effects between lower hybrid wave (LHW) and ion Bernstein wave (IBW) injections on current drive profiles are systematically studied based on the MHD equilibrium profiles of the Experimental Advanced Superconducting Tokamak (EAST). The simulation results indicate that the modifications of the distribution function due to IBW injection are nonlocalized in space and can affect the current drive profiles. The lower hybrid current drive efficiency can be either enhanced or reduced depending on the spectrum of the IBW injected into the plasma. In order to achieve stronger driven current, an appropriate IBW spectrum should be chosen for the combination of the LHW and IBW injections.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Pressure Effects on the Magnetic Phase Transition of Mn3SnC1−xNx (x=0, 0.5)
HU Jing-Yu, WEN Yong-Chun, YAO Yuan, WANG Cong, ZHAO Qing, JIN Chang-Qing, and YU Ri-Cheng
Chin. Phys. Lett. 2012, 29 (8): 086201 .   DOI: 10.1088/0256-307X/29/8/086201
Abstract   PDF(pc) (623KB) ( 899 )
The electronic transport properties of Mn3SnC and Mn3SnC0.5N0.5 were measured under pressures up to 1.8 GPa. At ambient pressure, an abrupt increase of resistance occurs around the temperature of magnetic phase transition in both samples. The transition temperature TC from paramagnetic to ferrimagnetic state decreases linearly at rates of 12.6 and 6.3 K/GPa with pressure for Mn3SnC and Mn3SnC0.5N0.5, respectively. This phenomenon could be understood by the Labbe–Jardin tight binding approximation model.
Scaling of the Leading Response in Linear Quench Dynamics in the Quantum Ising Model
YU Wing-Chi, WANG Li-Gang, GU Shi-Jian, and LIN Hai-Qing
Chin. Phys. Lett. 2012, 29 (8): 086402 .   DOI: 10.1088/0256-307X/29/8/086402
Abstract   PDF(pc) (561KB) ( 409 )
We study the scaling behavior of the linear response in the quench dynamics in the one-dimensional transverse-field Ising model. It is found that the leading response of the system scales linearly with the system size. By considering the second derivative of the leading term of the response, we also found that it exhibits a non-trivial scaling behavior at the quantum critical point of the model.
Sacrifice-Template Synthesis of CdTe Nanorod Arrays in Glycol via a Solvothermal Process
DENG Yuan, LIU Jing, WANG Yao, and LIANG Li-Xing
Chin. Phys. Lett. 2012, 29 (8): 086801 .   DOI: 10.1088/0256-307X/29/8/086801
Abstract   PDF(pc) (1104KB) ( 448 )
CdTe nanorod arrays were prepared by using a simple solvothermal process using Te nanorod arrays as the sacrifice template. The CdTe nanorods are orientation stacked by lots of CdTe nanoparticles. The photoluminescence properties of these arrays include excellent fluorescence. The concentration of KOH plays a key role in the formation of CdTe nanorod arrays. The possible formation mechanism of CdTe nanorod arrays is proposed.
Electric-Field Switching of Exciton Spin Splitting in Asymmetrical Coupled Quantum Dots
LI Xiao-Jing
Chin. Phys. Lett. 2012, 29 (8): 086802 .   DOI: 10.1088/0256-307X/29/8/086802
Abstract   PDF(pc) (737KB) ( 401 )
The spin splitting of the exciton states in semiconductor asymmetrical coupled quantum dots (CQDs) containing a single magnetic ion is theoretically investigated. It is found that the spin splitting is not the largest when the electric field is zero. An electric field stronger than that in symmetrical CQDs is necessary to switch the splitting on/off. The mixing between the bonding and antibonding hole states consequently results in the bright-to-dark transition of the ground exciton in the photoluminescence spectrum.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Unipolar Resistive Switching Effects Based on Al/ZnO/P++-Si Diodes for Nonvolatile Memory Applications
SHI Wei, TAI Qiang, XIA Xian-Hai, YI Ming-Dong, XIE Ling-Hai, FAN Qu-Li, WANG Lian-Hui, WEI Ang, and HUANG Wei
Chin. Phys. Lett. 2012, 29 (8): 087201 .   DOI: 10.1088/0256-307X/29/8/087201
Abstract   PDF(pc) (939KB) ( 663 )
Al/ZnO/P++-Si diodes exhibit typical unipolar resistive switching behaviors. The electroforming-free characteristics are observed after annealing the ZnO thin film at 400°C in air. The ON/OFF ratios of the resistance are in the range of 104–105 at a very low operation voltage of 0.1 V, and the devices show good endurance characteristics of over 400 cycles with negligible reduction. Finally, the memory mechanisms of the diodes are proposed on the basis of the current-voltage and resistance-voltage results. These results indicate that Al/ZnO/P++-Si devices have potential applications in nonvolatile memory devices.
Spin Filtering in a Rashba Electron Waveguide Induced by Edge Disorder
XIAO Xian-Bo, LI Fei, and LIU Nian-Hua
Chin. Phys. Lett. 2012, 29 (8): 087202 .   DOI: 10.1088/0256-307X/29/8/087202
Abstract   PDF(pc) (629KB) ( 366 )
We theoretically study the spin-dependent electron transport in a Rashba electron waveguide with rough edges, attached to ideal leads without spin-orbit interaction. The influence of the edge disorder on the charge and spin conductances is clarified by using the spin-resolved lattice Green function method. It is found that a spin-polarized current can be generated in the output lead and its spin polarization can be manipulated by varying the waveguide length. The underlying physics is attributed to the broken longitudinal symmetry and the spin-dependent quantum interference induced by the rough boundaries. Our results may provide a new method to design a spin filter without using magnetic materials or applying a magnetic field.
Determination of Channel Temperature in AlGaN/GaN HEMTs by Pulsed IV Characteristics
WANG Jian-Hui, WANG Xin-Hua, PANG Lei, CHEN Xiao-Juan, JIN Zhi, and LIU Xin-Yu
Chin. Phys. Lett. 2012, 29 (8): 087203 .   DOI: 10.1088/0256-307X/29/8/087203
Abstract   PDF(pc) (743KB) ( 758 )
Electrical determination of the channel temperature used for AlGaN/GaN high-electron-mobility transistors (HEMTs) is proposed. The measurement is based on the pulse technique that superposes a detecting pulse on the quiescent bias to acquire the electrical response under various thermal conditions. Practical experiments and electro-thermal simulations manifest that the duration of the pulse used has a fairly slight influence in the measured results. Finally, noticeable variance of thermal resistance at different gate biases is reported and the thermal resistance as a function of gate voltage decreases from 18.6 to 12.3°C?mm/W as the gate bias increases from ?1 V to 2 V under low power density condition.
Forward Current Transport Mechanism and Schottky Barrier Characteristics of a Ni/Au Contact on n-GaN
YAN Da-Wei, ZHU Zhao-Min, CHENG Jian-Min, GU Xiao-Feng, and LU Hai
Chin. Phys. Lett. 2012, 29 (8): 087204 .   DOI: 10.1088/0256-307X/29/8/087204
Abstract   PDF(pc) (606KB) ( 1103 )
The forward current transport mechanism and Schottky barrier characteristics of a Ni/Au contact on n-GaN are studied by using temperature-dependent current-voltage (TIV) and capacitance-voltage (CV) measurements. The low-forward-bias IV curve of the Schottky junction is found to be dominated by trap-assisted tunneling below 400 K, and thus can not be used to deduce the Schottky barrier height (SBH) based on the thermionic emission (TE) model. On the other hand, TE transport mechanism dominates the high-forward-bias region and a modified IV method is adopted to deduce the effective barrier height. It is found that the estimated SBH (~0.95 eV at 300 K) by the IV method is ~0.20 eV lower than that obtained by the CV method, which is explained by a barrier inhomogeneity model over the Schottky contact area.
Energy Band Structure of the Electron Gas in Periodic Quantum Wells
MAO Sheng-Hong, MA Yu-Ting, and XUE Ju-Kui
Chin. Phys. Lett. 2012, 29 (8): 087301 .   DOI: 10.1088/0256-307X/29/8/087301
Abstract   PDF(pc) (608KB) ( 529 )
The energy band structure and current density of electron gas with an exchange-correlation effect in periodic quantum wells are discussed. It is found that the energy band shows a swallowtail structure at the boundary of the first Brillouin zone when the electron exchange-correlation effect is presented and the average electron density is smaller than a critical value. The energy band structure is closely related to the current density of the system.
Numerical Simulation of a P+ a-SiC:H/N+ Poly-Si Solar Cell with High Efficiency and Fill Factor
SHAO Qing-Yi, CHEN A-Qing, ZHU Kai-Gui, and ZHANG Juan
Chin. Phys. Lett. 2012, 29 (8): 087302 .   DOI: 10.1088/0256-307X/29/8/087302
Abstract   PDF(pc) (702KB) ( 599 )
The P+ a-SiC:H/N+ poly-Si solar cell is simulated by an AMPS-1D device simulator to characterize the new thin film polycrystalline-silicon solar cell. In order to analyze the characteristics of the device, the thickness, working temperature, and impurity concentration for the N+ polysilicon layer are considered. The results show that the performance of the cells shows little change when the thickness of N+ polysilicon varies from 10 to 30 μm . It is concluded that the P+ a-SiC:H/N+ poly-Si solar cell has the highest performance with high open circuit voltages (Voc) of 1.31 V, high conversion efficiency of 17.363% and high fill factor of 0.884. Therefore, the P+ a-SiC:H/N+ poly-Si solar cell has promising future applications.
Double-Peak N-Shaped Negative Differential Resistance in a Quantum Dot Field Effect Transistor
XU Xiao-Na, WANG Xiao-Dong, LI Yue-Qiang, CHEN Yan-Ling, JI An, ZENG Yi-Ping, and YANG Fu-Hua
Chin. Phys. Lett. 2012, 29 (8): 087303 .   DOI: 10.1088/0256-307X/29/8/087303
Abstract   PDF(pc) (535KB) ( 428 )
Double-peak N-shaped negative differential resistance (NDR) with a high peak-to-valley ratio is observed in the output characteristics of a GaAs-based modulation-doped field effect transistor with InAs quantum dots in the barrier layer (QDFET). One NDR peak with a higher source-drain voltage VDS is explained as the real-space transfer (RST) of high-mobility electrons in the channel into the quantum dots layer, while the other with a lower VDS is caused by the high-mobility RST electrons in the channel into the modulation-doped AlGaAs barrier layer on the other side. We depict a point how a thinner Schottky barrier layer provides a stronger potential, opening a possibility of two-directional channel electron transfer when a much higher VG is applied. The result suggests that the QDFET can be an attractive candidate for high-speed logic application and memory devices.
Optical Investigation of Sm3+ Doped Zinc-Lead-Phosphate Glass
Raja J. Amjad, M. R. Sahar, S. K. Ghoshal, M. R. Dousti, S. Riaz, and B. A. Tahir
Chin. Phys. Lett. 2012, 29 (8): 087304 .   DOI: 10.1088/0256-307X/29/8/087304
Abstract   PDF(pc) (638KB) ( 941 )
Samarium doped lead-zinc-phosphate glasses having composition (60?x)P2O5-20PbO-20ZnO-xSm2O3 where x=0, 0.5, 1.0, 3.0mol% were prepared by using the melt quenching technique. The Archimedes method was used to measure their densities, which are used to calculate the molar volumes. The values of densities lie in the range 3.698–4.090 gm/cm3 whereas those of molar volume lie in the range of 37.24–40.00 cm?3. UV-vis-NIR absorption spectroscopy in the wavelength range 200–2000 nm was carried out. Absorption spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels. The energy band gap measured from the optical absorbance is found to be in the range of 3.88–4.43 eV and 3.68–4.33 eV for direct and indirect transitions, respectively. In addition, the photoluminescence spectrum shows four prominent emission bands centered at 560, 597, 642 and 700 nm corresponding to the 4G5/26HJ (J=5/2, 7/2, 9/2, 11/2) transitions respectively and the intensity of all the bands are enhanced as the concentration of Sm3+ ions increases.
Growth and Characterization of High-Quality Single Crystals of Ni- and Zn-Doped Bi2Sr2Ca(Cu2−xMx)O8 (M = Ni or Zn) High-Temperature Superconductors
LIU Shan-Yu, ZHANG Wen-Tao, ZHAO Lin, LIU Hai-Yun, WU Yue, LIU Guo-Dong, DONG Xiao-Li, and ZHOU Xing-Jiang
Chin. Phys. Lett. 2012, 29 (8): 087401 .   DOI: 10.1088/0256-307X/29/8/087401
Abstract   PDF(pc) (697KB) ( 1003 )
High-quality large single crystals of Ni- and Zn-doped Bi2Sr2Ca(Cu2?xMx)O8 (M = Ni or Zn) have been successfully grown by the traveling solvent floating zone technique. The single crystals are characterized by compositional and structural analyses and their physical properties are investigated by magnetic susceptibility and resistivity measurements. A record high critical temperature with a Tc=97.5 K has been achieved in the annealed pristine Bi2212 single crystal. Substitution of Cu by Ni or Zn reduces the superconducting transition temperature when compared with pristine Bi2Sr2CaCu2O8 (Bi2212) grown under similar conditions. The successful growth of such pristine Ni- and Zn-doped Bi2212 single crystals will facilitate studies of the relationship between the magnetism and superconductivity in high-temperature cuprate superconductors.
Tailoring the Microstructure of NiZn Ferrite for Power Field Applications
TANG Xiao-Li, SU Hua, and ZHANG Huai-Wu
Chin. Phys. Lett. 2012, 29 (8): 087501 .   DOI: 10.1088/0256-307X/29/8/087501
Abstract   PDF(pc) (935KB) ( 436 )
The effects of grain size and magnetic domain state on the power loss (from low to high induction conditions) and permeability characteristics of NiZn ferrites are investigated. It is found that under relatively low induction conditions (Bm<50 mT), a NiZn ferrite with a dense and monodomain microstructure obtains the lowest power loss. However, a NiZn ferrite with a larger average grain size displays a lower power loss under high induction conditions, and the influence of domain state on power loss is inconspicuous. Extremely large grain size and closed pores also lead to a poor frequency stability of permeability. Thus, synthetically considering the power loss and permeability characteristics, a NiZn ferrite with an even and large average grain size also has few closed pores and is the best choice for use under high induction conditions.
Structural and Electrical Characteristics of Amorphous ErAlO Gate Dielectric Films
ZHU Yan-Yan, FANG Ze-Bo, and TAN Yong-Sheng
Chin. Phys. Lett. 2012, 29 (8): 087701 .   DOI: 10.1088/0256-307X/29/8/087701
Abstract   PDF(pc) (642KB) ( 404 )
Ultrathin high-k dielectric ErAlO films were deposited on Si (100) substrates by using radio-frequency magnetron sputtering. The very flat surface of the annealed film with a rms roughness less than 0.25 nm was observed by using an atomic force microscope. The film shows good thermal stability when annealing at 900°C for 30 s in the O2 ambient. The effective dielectric constant of the film is around 15.2, and a low leakage current of 8.4×10?5 A/cm2 at an electric field of 1 MV/cm was achieved for the film with the equivalent oxide thickness of 2.0 nm after annealing.
Observation of Two-Photon Induced Excited-State Absorption Phenomena in C60 and C70 Derivatives
OUYANG Xin-Hua, LU Liang, and GE Zi-Yi
Chin. Phys. Lett. 2012, 29 (8): 087801 .   DOI: 10.1088/0256-307X/29/8/087801
Abstract   PDF(pc) (542KB) ( 374 )
Four fullerene dyads with different cabazole units, named a, b, c, d, were studied by using a femtosecond laser with 780 nm wavelength using Z-scan methods. Interestingly, all of them show strong two-photon induced excited-state absorption behaviors, which were observed firstly in femtosecond timescale. The values of their excited-state absorption cross-section were up to 6.07×10?18, 7.27×10?18, 3.86×10?18 and 4.51×10?18 cm?1 for a, b, c, and d, respectively.
Effects of Annealing on Thermoluminescence Peak Positions and Trap Depths of Synthetic and Natural Quartz by Means of the Various Heating Rate Method
Hüseyin Toktamiş, and A. Necmeddin Yazici
Chin. Phys. Lett. 2012, 29 (8): 087802 .   DOI: 10.1088/0256-307X/29/8/087802
Abstract   PDF(pc) (510KB) ( 771 )
Some environmental and experimental variables such as annealing process alter the structure of glow curves of some thermoluminescence materials. We investigate the effects of annnealing on thermoluminescence peaks of synthetic and natural quartz at different heating rates. The experimental results show that the peak temperatures of glow peaks in annealed samples shift to higher temperature sides. The amount of shifting is higher for low temperature peaks than high temperature peaks. The trap depths of annealed and unannealed samples of both synthetic and natural quartz are also obtained by various heating rate methods. It is noted that the annealing process affects the trap depth of all glow peaks and the trap depth increases after the annealing process.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Effects of the V/III Ratio of a Low-Temperature GaN Buffer Layer on the Structural and Optical Properties of a-GaN Films Grown on r-Plane Sapphire Substrates by MOCVD
TIAN Yu, DAI Jiang-Nan, XIONG Hui, ZHENG Guang, RYU My, FANG Yan-Yan, and CHEN Chang-Qing
Chin. Phys. Lett. 2012, 29 (8): 088101 .   DOI: 10.1088/0256-307X/29/8/088101
Abstract   PDF(pc) (677KB) ( 529 )
We investigate the effects of the V/III ratio of a low-temperature GaN buffer layer on the growth of the overlaying nonpolar -plane GaN film grown on -plane sapphire by metal-organic chemical-vapor deposition (MOCVD). With other experimental conditions keeping fixed, the low-temperature GaN buffer layers are grown under various V/III ratios of 1000, 3000, 6000 and 9000, respectively. The characteristics of the -plane GaN films are analyzed by scanning electron microscopy, high resolution x-ray diffraction, Raman spectrum, and low temperature photoluminescence. The results show that the V/III ratio of the buffer layer has significant effects on the crystal quality of the a-plane GaN film, and a V/III ratio of 6000 is found to be the most suitable condition to achieve pit-free flat GaN surface.
Improvement of the Quality of a GaN Epilayer by Employing a SiNx Interlayer
YANG De-Chao, LIANG Hong-Wei, SONG Shi-Wei, LIU Yang, SHEN Ren-Sheng, LUO Ying-Min, ZHAO Hai-Feng, and DU Guo-Tong
Chin. Phys. Lett. 2012, 29 (8): 088102 .   DOI: 10.1088/0256-307X/29/8/088102
Abstract   PDF(pc) (1530KB) ( 1055 )
GaN epilayers with a porous SiNx interlayer were grown by metal-organic chemical vapor deposition on c-plane sapphire substrates. It is found that the crystalline qualities are significantly improved with SiNx growth. The improvement is attributed to the reduction of the density of threading dislocations (TDs) by an over-growth process of GaN grown on a SiNx interlayer. The influence mechanism of SiNx interlayers on GaN growth mode is also discussed.
Superhydrophilic and Wetting Behavior of TiO2 Films and their Surface Morphologies
WANG Wei, ZHANG Da-Wei, TAO Chun-Xian, WANG Qi, WANG Wen-Na, HUANG Yuan-Shen, NI Zheng-Ji, ZHUANG Song-Lin, LI Hai-Xia, and MEI Ting
Chin. Phys. Lett. 2012, 29 (8): 088103 .   DOI: 10.1088/0256-307X/29/8/088103
Abstract   PDF(pc) (4336KB) ( 979 )
TiO2 films, showing superhydrophilic behavior, are prepared by electron beam evaporation. Atomic force microscopy and the contact angle measurement were performed to characterize the morphology and wetting behavior of the TiO2 films. Most studies attribute the wetting behavior of TiO2 surfaces to their physical characteristics rather than surface chemistry. These physical characteristics include surface morphology, roughness, and agglomerate size. We arrange these parameters in order of effectiveness. Surface morphologies are demonstrated to be the most important. TiO2 films with particular morphologies show superhydrophilic behavior without external stimuli, and these thin films also show stable anti-contamination properties during cyclical wetting and drying.
Effect Mechanism of a Direct Current on the Solidification of Immiscible Alloys
JIANG Hong-Xiang, and ZHAO Jiu-Zhou
Chin. Phys. Lett. 2012, 29 (8): 088104 .   DOI: 10.1088/0256-307X/29/8/088104
Abstract   PDF(pc) (1679KB) ( 501 )
Continuous solidification experiments are carried out with Al-Pb alloys under the effect of a direct current. The microstructure evolution in the samples is calculated. The numerical results obtained indicate that a direct current has great effects on the solidification of immiscible alloys. It mainly affects the microstructure evolution during a liquid-liquid decomposition by changing the spatial motions of the minority phase droplets and the temperature field in front of the solidification interface. A sample with either a well dispersed or a core/shell microstructure can be obtained by solidifying Al-Pb alloys under the effect of properly selected direct currents.
Cathode-Control Alloying at an Au-ZnSe Nanowire Contact via in Situ Joule Heating
ZENG Ya-Ping, WANG Yan-Guo, QU Bai-Hua, and YU Hong-Chun
Chin. Phys. Lett. 2012, 29 (8): 088105 .   DOI: 10.1088/0256-307X/29/8/088105
Abstract   PDF(pc) (533KB) ( 419 )
Controllable interfacial alloying is achieved at a Au-ZnSe nanowire (M-S) contact via in situ Joule heating inside transmission electron microscopy (TEM). TEM inspection reveals that the Au electrode is locally molten at the M-S contact and the tip of the ZnSe nanowire is covered by the Au melting. Experimental evidences confirm that the alloying at the reversely biased M-S contact is due to the high resistance of the Schottky barrier at this M-S contact, coincident to cathode-control mode. Consequently, in situ Joule heating can be an effective method to improve the performance of nanoelectronics based on a metal-semiconductor-metal nanostructure.
Single and Double Superconducting Coplanar Waveguide Resonators
ZHAO Na, LIU Jian-She, LI Hao, LI Tie-Fu, and CHEN Wei
Chin. Phys. Lett. 2012, 29 (8): 088401 .   DOI: 10.1088/0256-307X/29/8/088401
Abstract   PDF(pc) (635KB) ( 794 )
Transmission characteristics of single and double coplanar waveguide (CPW) resonators are simulated. The crosstalk of two CPW resonators located on the same chip is observed in simulation as well as in low temperature measurement results. The crosstalk behaves as exponential attenuation versus the distance between two resonators.
Low Power and High Sensitivity MOSFET-Based Pressure Sensor
ZHANG Zhao-Hua, REN Tian-Ling, ZHANG Yan-Hong, HAN Rui-Rui, and LIU Li-Tian
Chin. Phys. Lett. 2012, 29 (8): 088501 .   DOI: 10.1088/0256-307X/29/8/088501
Abstract   PDF(pc) (533KB) ( 1457 )
Based on the metal-oxide-semiconductor field effect transistor (MOSFET) stress sensitive phenomenon, a low power MOSFET pressure sensor is proposed. Compared with the traditional piezoresistive pressure sensor, the present pressure sensor displays high performances on sensitivity and power consumption. The sensitivity of the MOSFET sensor is raised by 87%, meanwhile the power consumption is decreased by 20%.
Modeling, Simulation and Analysis of Thermal Resistance in Multi-finger AlGaN/GaN HEMTs on SiC Substrates
WANG Jian-Hui, WANG Xin-Hua, PANG Lei, CHEN Xiao-Juan, and LIU Xin-Yu
Chin. Phys. Lett. 2012, 29 (8): 088502 .   DOI: 10.1088/0256-307X/29/8/088502
Abstract   PDF(pc) (720KB) ( 896 )
The effects of varying layout geometries and various thermal boundary resistances (TBRs) on the thermal resistance of multi-finger AlGaN/GaN HEMTs are thoroughly investigated using a combination of a two-dimensional electro-thermal model coupled with the three-dimensional thermal model. Temperature measurement using micro-Raman thermography is performed to verify and enhance the accuracy of the thermal model. Simulation results indicate that thermal resistance weakly depends on the layout design because of the high thermal conductivity of SiC. Meanwhile, the analysis reveals that optimizing the TBR of the device could efficiently reduce the thermal resistance since TBR takes a significant proportion of the total thermal resistance.
Experimental Study of Entropy Production in Cells under Alternating Electric Field
DING Chang-Jiang, and LUO Liao-Fu
Chin. Phys. Lett. 2012, 29 (8): 088701 .   DOI: 10.1088/0256-307X/29/8/088701
Abstract   PDF(pc) (436KB) ( 455 )
We put forward a new method for measuring the entropy production in the living cell. It involves heating the sample by alternating the electric field and recording the outward heat flow. The entropy production in a normal cell MCF10A and a cancerous cell MDA-MB-231 were measured and compared. The results show that the method is effective for the entropy measurement of a living organism. The scaled electro-induced entropy production rate (SEEP) of MDA-MB-231 monotonically increases with the electric field strength at 5–40 V/cm. While that of MCF10A changes non-monotonically and there exists a peak at 5–30 V/cm. The electro-induced entropy production ratio (EEPR) is smaller than 1 in a large range of field strengths, from 5 to 25 V/cm, which reveals that under 5–25 V/cm electric field exposure, the direction of the entropy flow may be changed from normal tissue to cancerous cells. We present a facile and effective strategy for experimentally investigating the thermodynamic properties of the cell and give a deeper insight into the physical difference between normal and cancerous cells under electric field exposure.
Modulation of Amyloid-β Conformation by Charge State of N-Terminal Disordered Region
XI Wen-Hui, LI Wen-Fei, and WANG Wei
Chin. Phys. Lett. 2012, 29 (8): 088702 .   DOI: 10.1088/0256-307X/29/8/088702
Abstract   PDF(pc) (658KB) ( 306 )
Based on molecular dynamics simulations, we show that variations of the charge states of the histidines, which are the main effects of pH-value change and metal binding, can lead to a drastic change of the intra-peptide interactions of the segment 17–42 and the conformational distribution of the monomeric amyloid-β (Aβ). Since we already knew that the conformational distribution of monomeric Aβ can largely affect Aβ fibrillar aggregation, our results suggest that the pH value change and metal binding can affect the Aβ aggregation by much more complex mechanism than just affecting the inter-peptide interactions. To fully understand the mechanism of metal binding and pH-value induced Aβ aggregation, we also need to consider their effects on the conformational distribution of monomeric Aβ.
Weak Field-Induced Evolution of Spiral Wave in Small-World Networks of Hodgkin–Huxley Neurons
WANG Ya-Min, LIU Yong, WANG Jing, and LIU Yu-Rong
Chin. Phys. Lett. 2012, 29 (8): 088703 .   DOI: 10.1088/0256-307X/29/8/088703
Abstract   PDF(pc) (1973KB) ( 468 )
An external weak electric field is introduced into the small-world networks of Hodgkin–Huxley neurons to study the control and breakup of a spiral wave. The effect of an external electric field on the neurons in the small-world network is described by an additive perturbation on the membrane potentials of neurons at the cellular level, in which an additive term VE is imposed on the physiological membrane potential. A statistical factor of synchronization is used to measure the collective behaviour of spiral waves by changing the electric field; it is confirmed that a smaller factor of synchronization is associated with the survival of a spiral wave. In the case of no channel noise, the spiral wave could be removed under a certain intensity of constant electric field; it keeps robustly to the weak electric field when the electric field changes periodically. In the case of weak channel noise, a breakup of the spiral wave is observed when the intensity of the electric field exceeds certain thresholds, which could be measured from the curve for synchronization factors. No drift of the spiral wave is observed under the weak electric field.
Polymer Photovoltaic Cells Based on Ultraviolet-Ozone-Treated Vanadium-Doped Indium Oxide Anodes
GUO Xiao-Yang, LUO Jin-Song, CHEN Hong, and LIU Xing-Yuan
Chin. Phys. Lett. 2012, 29 (8): 088801 .   DOI: 10.1088/0256-307X/29/8/088801
Abstract   PDF(pc) (548KB) ( 645 )
Polymer photovoltaic (PV) cells based on UV-ozone(UVO)-treated indium vanadium oxide (IVO) anodes are developed. The performance of cells with UVO-treated IVO film anodes without interfacial layers was significantly improved compared with those containing untreated IVO anodes. The origin of the enhancement is investigated by atomic force microscopy and photoelectron spectroscopy measurements. The results demonstrate that UVO treatment can smooth the IVO surface, and increase the work function of IVO films due to the removal of carbon contamination and a dipole resulting from a surface rich in negatively charged oxygen. UVO-treated IVO films are potential electrode materials for polymer PV cells.
Cooperative Enhancement of Cost Threshold in the Spatial N-Person Snowdrift Game
LU Dong-Liang, ZHANG Hong-Bin, GE Juan, and XU Chen
Chin. Phys. Lett. 2012, 29 (8): 088901 .   DOI: 10.1088/0256-307X/29/8/088901
Abstract   PDF(pc) (586KB) ( 412 )
We study the cooperative behaviour of the N-person snowdrift game on a square lattice with different neighbourhoods and the cost threshold M for the cooperators. We apply the imitation mechanism for the players and find that there is an optimal frequency of cooperation fC as M varies in the game and the peak of fC shifts to higher M when more neighbours on the lattice are involved in the game. For a given cost-to-benefit ratio r, the system shows discontinuous phase transitions and the behaviour of fC vs M shows step-like structures. We construct payoff level structures and find that the above features can be understood by analyzing the transition behaviour between the payoff levels. The variations of r and M are equivalent to tune the payoff level structures. The plateaus in the step-like structure have similar payoff level structures and the discontinuous jumps correspond to different payoff level structures.
Power-Law Exponent for Exponential Growth Network
WANG Li-Na, CHEN Bin, and ZANG Chen-Rui
Chin. Phys. Lett. 2012, 29 (8): 088902 .   DOI: 10.1088/0256-307X/29/8/088902
Abstract   PDF(pc) (696KB) ( 420 )
The question of the power-law exponent of exponential growth networks is studied here. In a discrete case, the degree distribution is defined as the probability distribution of the discrete variable. Based on this, the degree distribution of the pseudofractal scale-free web, an exponential growth network, is obtained. The power-law exponent ln3/ln2 is analyzed according to the maximum likelihood principle. It satisfies consistency and is good for small generations of the network. For many exponential growth networks, their power-law exponent needs to be tested. The work provides a new view on the power-law exponent of an exponential growth network.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
Anomalous Resistivity Associated with Secondary Islands in the Reconnection Region
ZHOU Meng, SU Wei, DENG Xiao-Hua, and YAO Ming
Chin. Phys. Lett. 2012, 29 (8): 089401 .   DOI: 10.1088/0256-307X/29/8/089401
Abstract   PDF(pc) (667KB) ( 346 )
We calculate the anomalous resistivity (AR) due to electrostatic waves, including possibly the lower hybrid wave and electron beam mode, around the secondary islands in the reconnection region observed by the Cluster spacecraft. Our main findings are: AR is important on the reconnection separatrix layer but heavily suppressed at the central current sheet where Bx0. Moreover, there is a highly asymmetric pattern of AR across the island along the outflow direction, with much larger AR on one side of island than on the other side. Our results may be helpful in understanding the role of AR in reconnection.
Spatial Evolution of Electrostatic Solitary Waves along Plasma Sheet Boundary Layer Adjacent to the Magnetic Reconnection X-Line
LI Shi-You, ZHANG Shi-Feng, DENG Xiao-Hua, and CAI Hong
Chin. Phys. Lett. 2012, 29 (8): 089402 .   DOI: 10.1088/0256-307X/29/8/089402
Abstract   PDF(pc) (928KB) ( 393 )
Analysis on the spatial structure of electrostatic solitary waves (ESWs) along the plasma sheet boundary layer (PSBL) near an on-going magnetic reconnection X-line is performed. Most of the ESWs in the PSBL of R3 region near reconnection X-line are propagating earthwards away from the reconnecting site. An analysis of their spatial structure shows that, when ESWs propagate along the ambient field in the PSBL, outwards from the magnetic reconnection X-line, their amplitude will finally attenuate and thus the electron hole will fade away but their spatial scale remains unchanged. However, the spatial structure of propagating ESWs evolves from 1-D-like to 2-D-like though totally in a 1-D structure.
Cross-Shock Electrostatic Potential and Ion Reflection in Quasi-Parallel Supercritical Collisionless Shocks
SU Yan-Qing, and LU Quan-Ming
Chin. Phys. Lett. 2012, 29 (8): 089601 .   DOI: 10.1088/0256-307X/29/8/089601
Abstract   PDF(pc) (560KB) ( 445 )
The time evolution of the cross-shock electrostatic potential jump during one specific high Mach number quasi-parallel shock reformation cycle is examined via a 1D hybrid simulation. It is shown that when the average value of the electrostatic potential jump is low, its instant value can be large so that the shock is in a favorable profile to directly reflect the incident ions. Our simulation also suggests that, for the ones that finally become injected ions (which can be further accelerated by diffusive shock acceleration mechanism), the first step of their reflections should be mainly attributed to the electrostatic potential jump, instead of the magnetic force, as stated in some previous studies.
83 articles