Current Issue

Volume 25 Issue 10
Online Date:
Previous Issue    Next Issue
Original Articles
R-Matrix of the Coupling AKNS Equation Hierarchy
YU Fa-Jun
Chin. Phys. Lett. 2008, 25 (10): 3519-3522 .  
Abstract   PDF(pc) (181KB) ( 677 )
A new r-matrix of the integrable coupling system is obtained by nonlinearization of the coupling eigenvalue problem. As a reduction, we present the r-matrix of the coupling Ablowitz--Kaup--Newell--Segur (AKNS) equation hierarchy via enlarged matrix Lie algebra.
Decomposition for a 2+1-Dimensional Discrete Integrable Model
SU Ting, MA Yun-Ling, GENG Xian-Guo
Chin. Phys. Lett. 2008, 25 (10): 3523-3526 .  
Abstract   PDF(pc) (201KB) ( 412 )
A 2+1-dimensional discrete is presented, which is decomposed into a new integrable symplectic map and a class of finite-dimensional integrable Hamiltonian systems, with aid of the nonlinearization of Lax pairs. The system is completely integrable in the Liouville sense.
Similarity Reductions and Similarity Solutions of the (3+1)-Dimensional Kadomtsev--Petviashvili Equation
LIU Na, LIU Xi-Qiang
Chin. Phys. Lett. 2008, 25 (10): 3527-3530 .  
Abstract   PDF(pc) (169KB) ( 508 )
Employing the compatibility method, we obtain the symmetries of the (3+1)-dimensional Kadomtsev--Petviashvili (KP) equation. Four types of similarity reductions of the KP equation are obtained by solving the corresponding characteristic equations associated with symmetry equations. In addition, a lot of similarity solutions to the KP equation are obtained.
Multisymplectic Integrator of the Zakharov System
Chin. Phys. Lett. 2008, 25 (10): 3531-3534 .  
Abstract   PDF(pc) (633KB) ( 587 )
A multisymplectic formulation for the Zakharov system is presented. The semi-explicit multisymplectic integrator of the formulation is constructed by means of the Euler-box scheme. Numerical results on simulating the propagation of one soliton and the collision of two solitons are reported to illustrate the efficiency of the multisymplectic scheme.
Wigner Functions for Non-Hamiltonian Systems on Noncommutative Space
HENG Tai-Hua, LIN Bing-Sheng, JING Si-Cong
Chin. Phys. Lett. 2008, 25 (10): 3535-3538 .  
Abstract   PDF(pc) (191KB) ( 383 )
We propose a modified form of Wigner functions for generic non-Hamiltonian systems on noncommutative space and prove that it satisfies the corresponding *-genvalue equation. In addition, as an example, we derive exact energy spectra and Wigner functions for a non-Hamiltonian toy model on the noncommutative space.
Normally Ordered Bivariate-Normal-Distribution Forms of Two-Mode Mixed States with Entanglement Involved
FAN Hong-Yi, WANG Tong-Tong, HU Li-Yun
Chin. Phys. Lett. 2008, 25 (10): 3539-3542 .  
Abstract   PDF(pc) (168KB) ( 507 )
Based on the technique of integration within an ordered product of operators we have demonstrated that single-mode mixed states' density matrices can be recast into the normally ordered Gaussian forms [Chin. Phys. Lett. 24(2007)3322]. Here we employ the Weyl ordering invariance under similar transformations to show that some two-mode mixed states with entanglement involved can be put into normally ordered form in the bivariate normal distribution too and its marginal distributions can be analysed. In this way, density operators of quantum statistics can be analogous to mathematical statistics, and calculation of variances can be simplified.
Multiparty Quantum Cryptographic Protocol
M. Ramzan, M. K. Khan
Chin. Phys. Lett. 2008, 25 (10): 3543-3546 .  
Abstract   PDF(pc) (220KB) ( 538 )
We propose a multiparty quantum cryptographic protocol. Unitary operators applied by Bob and Charlie, on their respective qubits of a tripartite entangled state encoding a classical symbol that can be decoded at Alice's end with the help of a decoding matrix. Eve's presence can be detected by the disturbance of the decoding matrix. Our protocol is secure against intercept--resend attacks. Furthermore, it is efficient and deterministic in the sense that two classical bits can be transferred per entangled pair of qubits. It is worth mentioning that in this protocol, the same symbol can be used for key distribution and Eve's detection that enhances the efficiency of the protocol.
Experimental Decoy State Quantum Key Distribution Over 120km Fibre
YIN Zhen-Qiang, HAN Zheng-Fu, CHEN Wei, XU Fang-Xing, WU Qing-Lin, GUOGuang-Can
Chin. Phys. Lett. 2008, 25 (10): 3547-3550 .  
Abstract   PDF(pc) (242KB) ( 957 )
Decoy state quantum key distribution (QKD), being capable of beating PNS attack and being unconditionally secure, has become attractive recently. However, in many QKD systems, disturbances of transmission channel make the quantum bit error rate (QBER) increase, which limits both security distance and key bit rate of real-world decoy state QKD systems. We demonstrate the two-intensity decoy QKD with a one-way Faraday--Michelson phase modulation system, which is free of channel disturbance and keeps an interference fringe visibility (99%) long period, over a 120km single mode optical fibre in telecom (1550nm) wavelength. This is the longest distance fibre decoy state QKD system based on the two-intensity protocol.
Cryptanalysis of Multiparty Quantum Secret Sharing of Quantum State Using Entangled States
QIN Su-Juan, WEN Qiao-Yan, ZHU Fu-Chen
Chin. Phys. Lett. 2008, 25 (10): 3551-3554 .  
Abstract   PDF(pc) (178KB) ( 795 )
Decoy state quantum key distribution (QKD), being capable of beating PNS attack and being unconditionally secure, has become attractive recently. However, in many QKD systems, disturbances of transmission channel make the quantum bit error rate (QBER) increase, which limits both security distance and key bit rate of real-world decoy state QKD systems. We demonstrate the two-intensity decoy QKD with a one-way Faraday--Michelson phase modulation system, which is free of channel disturbance and keeps an interference fringe visibility (99%) long period, over a 120km single mode optical fibre in telecom (1550nm) wavelength. This is the longest distance fibre decoy state QKD system based on the two-intensity protocol
Efficient Construction of High-Dimensional Cluster State
DIAO Da-Sheng, ZHANG Yong-Sheng, ZHOU Xiang-Fa, GUO Guang-Can
Chin. Phys. Lett. 2008, 25 (10): 3555-3557 .  
Abstract   PDF(pc) (290KB) ( 677 )
We present a scheme for efficiently constructing high-dimensional cluster state using probabilistic entangling quantum gates. It is shown that the required computational overhead scales efficiently both with 1/p and n even if all the entangling quantum gates only succeed with an arbitrary small probability, where p is the success probability of the entangling quantum gate and n is the number of qubits in the computation.
Generation of Multiphoton Entangled States with Linear Optical Elements
SHENG Yu-Bo, DENG Fu-Guo, ZHOU Hong-Yu
Chin. Phys. Lett. 2008, 25 (10): 3558-3561 .  
Abstract   PDF(pc) (175KB) ( 536 )

We propose a linear optical protocol to generate three-photon and four-photon entangled states without resorting to entangled sources. The setup in this protocol is composed of three beam splitters and two half-wave plates. We can obtain three-photon and four-photon entangled states with postselection, as with other protocols. This protocol has the advantage of high efficiency and is more feasible than others.

Optical Generation of Single- or Two-Mode Excited Entangled Coherent States
REN Zhen-Zhong, JING Hui, ZHANG Xian-Zhou
Chin. Phys. Lett. 2008, 25 (10): 3562-3565 .  
Abstract   PDF(pc) (370KB) ( 589 )
With nonlinear Mach--Zehnder interferometer (NLMZI) and a type-I beta-barium borate (BBO) crystal, we optically generate single-mode excited entangled coherent states. This scheme can be easily generalized to generate two-mode excited entangled coherent states. We simply analyse different influences of single- and two-mode photon excitations on entangled coherent states
Tunnelling Dynamics of Bose--Einstein Condensates in a Five-Well Trap
ZHANG Ai-Xia, TIAN Shi-Ling, TANG Rong-An, XUE Ju-Kui
Chin. Phys. Lett. 2008, 25 (10): 3566-3569 .  
Abstract   PDF(pc) (500KB) ( 349 )
We develop a five-well model for describing the tunnelling dynamics of Bose--Einstein condensates (BECs) trapped in 2D optical lattices. The tunnelling dynamics of BECs in this five-well model are investigated both analytically and numerically. We focus on the self-trapped states and the difference of the tunnelling dynamics among two-well, three-well and five-well systems. The criterions for the self-trapped states and the phase diagrams of the five trapped BECs in zero-phase mode and π-phase mode are obtained. We find that the criterions and the phase diagrams are largely modified by the dimension of the system and the phase difference between wells. The five-well model is a good model and can give us an insight into the tunnelling dynamics of BECs trapped in 2D optical lattices.
Reissner--Nordström-de--Sitter-type Solution by a Gauge Theory of Gravity
V. Enache, Camelia Popa, V. Paun, M. Agop,
Chin. Phys. Lett. 2008, 25 (10): 3570-3573 .  
Abstract   PDF(pc) (169KB) ( 498 )
We use the theory based on a gravitational gauge group (Wu's model) to obtain a spherical symmetric solution of the field equations for the gravitational potential on a Minkowski spacetime. The gauge group, the gauge covariant derivative, the strength tensor of the gauge field, the gauge invariant Lagrangean with the cosmological constant, the field equations of the gauge potentials with a gravitational energy--momentum tensor as well as with a tensor of the field of a point like source are determined. Finally, a Reissner--Nordström--de Sitter-type metric on the gauge group space is obtained.
Quantum Phase Transitions in Matrix Product States
ZHU Jing-Min
Chin. Phys. Lett. 2008, 25 (10): 3574-3577 .  
Abstract   PDF(pc) (266KB) ( 623 )
We present a new general and much simpler scheme to construct various quantum phase transitions (QPTs) in spin chain systems with matrix product ground states. By use of the scheme we take into account one kind of matrix product state (MPS) QPT and provide a concrete model. We also study the properties of the concrete example and show that a kind of QPT appears, accompanied by the appearance of the discontinuity of the parity absent block physical observable, diverging correlation length only for the parity absent block operator, and other properties which are that the fixed point of the transition point is an isolated intermediate-coupling fixed point of renormalization flow and the entanglement entropy of a half-infinite chain is discontinuous.
Long-Time Dynamic Response and Stochastic Resonance of Subdiffusive Overdamped Bistable Fractional Fokker--Planck Systems
KANG Yan-Mei, JIANG Yao-Lin
Chin. Phys. Lett. 2008, 25 (10): 3578-3581 .  
Abstract   PDF(pc) (299KB) ( 491 )

To explore the influence of anomalous diffusion on stochastic resonance (SR) more deeply and effectively, the method of moments is extended to subdiffusive overdamped bistable fractional Fokker--Planck systems for calculating the long-time linear dynamic response. It is found that the method of moments attains high accuracy with the truncation order N=10, and in normal diffusion such obtained spectral amplification factor (SAF) of the first-order harmonic is also confirmed by stochastic simulation. Observing the SAF of the odd-order harmonics we find some interesting results, i.e. for smaller driving frequency the decrease of subdiffusion exponent inhibits the stochastic resonance (SR), while for larger driving frequency the decrease of subdiffusion exponent enhances the second SR peak, but the first one vanishes and a double SR is induced in the third-order harmonic at the same time. These observations suggest that the anomalous diffusion has important influence on the bistable dynamics.

Control Chaos in Hindmarsh--Rose Neuron by Using Intermittent Feedback with One Variable
MA Jun, WANG Qing-Yun, JIN Wu-Yin, XIA Ya-Feng
Chin. Phys. Lett. 2008, 25 (10): 3582-3585 .  
Abstract   PDF(pc) (464KB) ( 572 )
The mechanism of the famous phase compression is discussed, and it is used to control the chaos in the Hindmarsh--Rose (H-R) model. It is numerically confirmed that the phase compression scheme can be understood as one kind of intermittent feedback scheme, which requires appropriate thresholds and feedback coefficient, and the intermittent feedback can be realized with the Heaviside function. In the case of control chaos, the output variable (usually the voltage or the membrane potential of the neuron) is sampled and compared with the external standard signal of the electric electrode. The error between the sampled variable and the external standard signal of the electrode is input into the system only when the sampled variable surpasses the selected thresholds. The numerical simulation results confirm that the chaotic H-R system can be controlled to reach arbitrary n-periodical (n=1, 2, 3, 4, 5, 6, ...) orbit or stable state even when just one variable is feed backed into the system intermittently. The chaotic Chua circuit is also investigated to check its model independence and effectiveness of the schemes and the equivalence of the two schemes are confirmed again.
Two-Dimensional Discrete Gap Breathers in a Two-Dimensional Diatomic β Fermi--Pasta--Ulam Lattice
XU Quan, TIAN Qiang
Chin. Phys. Lett. 2008, 25 (10): 3586-3589 .  
Abstract   PDF(pc) (808KB) ( 401 )
We study the existence of two-dimensional discrete breathers in a two-dimensional face-centred square lattice consisting of alternating light and heavy atoms, with nearest-neighbour coupling containing quartic soft or hard
nonlinearity. This study is focused on two-dimensional breathers with frequency in the gap that separates the acoustic and optical bands of the phonon spectrum. We demonstrate the possibility of existence of two-dimensional gap breathers by using the numerical method, the local anharmonicity approximation and the rotating wave approximation. We obtain six types of two-dimensional gap breathers, i.e., symmetric, mirror-symmetric and asymmetric, no matter whether the centre of the breather is on a light or a heavy atom.
Nitrogen Dioxide Sensing Properties and Mechanism of Copper Phthalocyanine Film
QIU Cheng-Jun, DOU Yan-Wei, ZHAO Quan-Liang, QU Wei, YUAN Jie, SUN Yan-Mei, CAO Mao-Sheng
Chin. Phys. Lett. 2008, 25 (10): 3590-3592 .  
Abstract   PDF(pc) (762KB) ( 994 )
Copper phthalocyanine film, a p-type organic semiconductor, is synthesized by vacuum sublimation and its surface morphology is characterized by SEM. A silicon-based copper phthalocyanine film gas sensor for NO2 detection is fabricated by MEMS technology. The results show that the resistance and sensitivity of copper phthalocyanine film decrease obviously as the NO2 concentration increases from 0ppm to 100ppm. However, the sensitivity nearly keeps a constant of 0.158 between 30ppm and 70ppm. The best working temperature of the gas sensor is 90°C for NO2 gas concentrations of 10ppm, 20ppm and 30ppm, which is much lower than that of general metal oxide gas sensor.
Temperature-Insensitive Fibre-Optic Acceleration Sensor Based on Intensity-Referenced Fibre Bragg Gratings
SUN Li-Qun, DONG Bo, WANG Yong-Xin, Evan LALLY, WANG An-Bo
Chin. Phys. Lett. 2008, 25 (10): 3593-3596 .  
Abstract   PDF(pc) (562KB) ( 818 )

A temperature-insensitive acceleration sensor using two fibre Bragg gratings (FBGs), based on reflection spectrum intensity modulation and optical power detection, is proposed and demonstrated. A cantilever beam is used to generate acceleration-induced axial strain along two sensing gratings, which are glued on the two opposite surfaces of the beam. Because the two gratings operate within the linear spectral range of a light source, formed by a thermally-tunable extrinsic Fabry--Perot optical filter, the intensity difference of the two reflections from the gratings is proportional to the acceleration applied. This eliminates the need for sophisticated wavelength interrogation of the gratings, and it also endows the sensor with immunity to temperature variation. Compared with a commercial micromachined accelerometer, the sensor is proven to be capable of accurately detecting acceleration.

Characterization Method of Polycrystalline Materials Using Conductive Atomic Force Microscopy
DING Xi-Dong, FU Gang, XIONG Xiao-Min, ZHANG Jin-Xiu
Chin. Phys. Lett. 2008, 25 (10): 3597-3600 .  
Abstract   PDF(pc) (596KB) ( 415 )
An apparatus for characterization of polycrystalline materials based on conductive atomic force microscopy (cAFM) is developed and a quantitative measurement of electrical characteristics of individual grains in polycrystalline ZnO ceramic is demonstrated. Improvement of the experimental method is presented. Experimental results illuminate unambiguously the different electrical characteristics between individual grains, suggesting the suitability and maneuverability of this method in the study of local structure or properties and their relationship in polycrystalline materials such as semi-conducting ceramics.
Remarks on Two-Dimensional Power Correction in Soft Wall Model
Chin. Phys. Lett. 2008, 25 (10): 3601-3604 .  
Abstract   PDF(pc) (187KB) ( 444 )
We present a direct derivation of the two-point correlation function of the vector current in the soft wall model by using the AdS/CFT dictionary. The resulting correlator is exactly the same as the one previously obtained from dispersion relation with the same spectral function as in this model. The coefficient C2 of the two-dimensional power correction is found to be C2=-c/2 with c the slope of the Regge trajectory, rather than C2=-c/3 derived from the strategy of the first quantized string theory. Taking the slope of the ρ trajectory c≈0.9GeV2 as input, we then obtain C2≈-0.45GeV2. The gluon condensate is found to be <αsG2>≈pprox0.064GeV4, which is almost identical to the QCD sum rule estimation. By comparing these two equivalent derivation of the correlator of scalar glueball operator, we demonstrate that the two-dimensional correction cannot be eliminated by including the non-leading solution in the bulk-to-boundary propagator, as carried out by Colangelo et al.[arXiv:0711.4747]. In other words, the two-dimensional correction does exist in the scalar glueball case. Also it is manifest by using the dispersion relation that the minus sign of gluon condensate and violation of the low energy theorem are related to the subtraction scheme.
Can a Chaotic Solution in the QCD Evolution Equation Restrain High-Energy Collider Physics?
ZHU Wei, SHEN Zhen-Qi, RUAN Jian-Hong
Chin. Phys. Lett. 2008, 25 (10): 3605-3608 .  
Abstract   PDF(pc) (426KB) ( 343 )
We indicate that the random aperiodic oscillation of the gluon distributions in a modified Balitsky--Fadin--Kuraev--Lipatov (BFKL) equation has positive
Lyapunov exponents. This first example of chaos in QCD evolution equations raises the sudden disappearance of the gluon distributions at a critical small value of the Bjorken variable x and may stop the increase of the new particle events in an ultra high energy hadron collider.
Three-Dimensional Angular Momentum Projected Relativistic Point-Coupling Approach for Low-Lying Excited States in 24Mg
Yao Jiang-Ming, Meng Jie, , D. Pena Arteaga, P. Ring
Chin. Phys. Lett. 2008, 25 (10): 3609-3612 .  
Abstract   PDF(pc) (491KB) ( 511 )
A full three-dimensional angular momentum projection on top of a triaxial relativistic mean-field calculation is implemented for the first time. The underlying Lagrangian is a point coupling model and pairing correlations are taken into account by a monopole force. This method is applied for the low-lying excited states in 24Mg. Good agreement with the experimental data is found for the ground state properties. A minimum in the potential energy surface for the 2+1 state, with β≈0.55, γ≈10°, is used as the basis to investigate the rotational energy spectrum as well as the corresponding B(E2) transition probabilities as compared to the available data
Extreme Exotic Calcium Lambda Hypernuclei in the Relativistic Continuum Hartree--Bogoliubov Theory
LÜ, Hong-Feng
Chin. Phys. Lett. 2008, 25 (10): 3613-3616 .  
Abstract   PDF(pc) (408KB) ( 495 )
Exotic calcium lambda hypernuclei properties with the neutron number of 20--400 by a step of 20 are discussed by employing the relativistic continuum
Hartree--Bogoliubov theory with a zero range pairing interaction. The Bethe--Weizsäcker mass formula of a multi-strange system and the Woods--Saxon-type potential of lambda need to be modified for exotic calcium hypernuclei with unusual number of neutrons and lambdas. The possible neutron and lambda limits of exotic Ca lambda hypernuclei are also investigated.
Measurements of g-Factor of Rotational Band States in 82Sr
YUAN Da-Qing, FAN Ping, ZHENG Yong-Nan, ZUO Yi, ZHOU Dong-Mei, WU Xiao-Guang, LI Guang-Sheng, ZHU Li-Hua, XU Guo-Ji, FAN Qi-Wen, ZHANG Xi-Zhen, ZHU Sheng-Yun
Chin. Phys. Lett. 2008, 25 (10): 3617-3619 .  
Abstract   PDF(pc) (206KB) ( 431 )
The g-factors of the positive parity rotational states up to spin I=8+ for the ground state band in even-even nuclei 82Sr have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured g-factors increase with the increasing spin along the band and show that the g9/2 proton aligns only and the alignment starts from I=6+. The measured g-factors also indicate that the nuclei 82Sr gain their spins by the quasi-proton alignment at higher spin.
Calculations of Photo-Ionization Cross Sections for Lithium Atoms
QI Yue-Ying, WU Yong, WANG Jian-Guo, DING Pei-Zhu
Chin. Phys. Lett. 2008, 25 (10): 3620-3623 .  
Abstract   PDF(pc) (325KB) ( 737 )
Photo-ionization cross sections for the ground and the n≤5 excited states of lithium atoms are calculated in the photoelectron energy ranging from threshold to 0.5 Rydberg. The wavefunctions for both the bound and continuum states are obtained by solving the Schrödinger equation numerically in a symplectic scheme. Our results are in excellent agreement with the recent experimental measurements and in harmony with other
theoretical calculations.
Photoionization of 1s Electron and Corresponding Shake-Up Process in Ground and Excited Lithium Atoms
SANG Cui-Cui, DING Xiao-Bin, DONG Chen-Zhong
Chin. Phys. Lett. 2008, 25 (10): 3624-3626 .  
Abstract   PDF(pc) (342KB) ( 828 )
The cross sections of the 1s electron photoionization and corresponding shake-up processes for Li atoms in the ground state 1s22s and excited states 1s22p, 1s23s, 1s23p and 1s23d are calculated usin the multi-configuration Dirac--Fock method. The latest experimental photoelectron spectrum at h\ν=100eV [Cubaynes D et al. Phys. Rev. Lett. 99(2007)213004] has been reproduced by the present theoretical investigation excellently. The relative intensity of the shake-up satellites shows that the effects of correlation and relaxation become more important for the higher excited states of the lithium atom, which are explained very well by the spatial overlap of the initial and final state wavefunctions. In addition, strong dependence of the cross section on the atomic orbitals of the valence electrons are found, especially near the threshold.
Ionization Energies of Ions in Hot and Dense Plasma: Beryllium-Like Ions for Z=26-36
LI Yong-Qiang, WU Jian-Hua, YUAN Jian-Min
Chin. Phys. Lett. 2008, 25 (10): 3627-3630 .  
Abstract   PDF(pc) (331KB) ( 399 )
Ionization energies of beryllium-like ions for Z=26-36 in hot and dense plasmas (ne=1022-1024cm-3, kT=500-2000eV) are obtained by using an approach developed for electronic structure and transition property of ions in hot and dense plasmas based on the multi-configuration Dirac--Fock model. Influence of the plasma environment is considered by introducing a correction to the one-electron potential to account for the screening of the ionized electrons. This correction is calculated from the ionized electron micro-space distribution, which is obtained based on an average atom model for the temperature and density-dependent average ionization of atoms in plasmas. Comparison between the present and the ion sphere models is made to display the significance of the ionized electron micro-space distribution.
Magneto-Optical Trapping of Ytterbium Atoms with a 398.9nm Laser
ZHAO Peng-Yi, , XIONG Zhuan-Xian, , LIANG Jie, , HE Ling-Xiang, LU Bao-Long,
Chin. Phys. Lett. 2008, 25 (10): 3631-3634 .  
Abstract   PDF(pc) (426KB) ( 752 )
We report the realization of ytterbium magneto-optical trap (MOT) operating on the dipole-allowed 1S0-1P1 transition at 398.9nm. The MOT is loaded by a
slowed atomic beam produced by a Zeeman slower. All seven stable isotopes of Yb atoms could be trapped separately at different laser detuning values. Over 107 174Yb atoms are collected in the MOT, whereas the atom number of fermionic isotope 171Yb is roughly 2.3×106 due to a lower abundance. Without the Zeeman slower, the trapped atom numbers are one order of magnitude lower. Both the even and odd isotopes are recognized as excellent candidates of optical clock transition, so the cooling and trapping of ytterbium atoms by the blue MOT is an important step for building an optical clock.
Application of the Second Born Approximation to Excitation of Hydrogen Atoms by Protons and Antiprotons Impact
Reda S. Tantawi, Samia M. Said
Chin. Phys. Lett. 2008, 25 (10): 3635-3638 .  
Abstract   PDF(pc) (304KB) ( 533 )
We present and compare total cross sections for excitation in collisions of protons and antiprotons with hydrogen atoms in the 2s state. Calculations are performed in the framework of the second Born approximation, in the energy range of 5--1000keV. We apply the usual approach of the second Born approximation, which approximates the summation raised by retaining few terms, as well as another approach approximates all energies corresponding to the intermediate states to that corresponding to the initial state. The annihilation effect in the case of the antiproton collision is investigated. We compare the results with the previous theoretical calculations.
Variable Phase Method Used to Calculate Ultracold Scattering Properties of 7Li33Cs
DU Bing-Ge, SUN Jin-Feng, ZHANG Ji-Cai, ZHANG Ying, LI Wei, ZHU Zun-Lue
Chin. Phys. Lett. 2008, 25 (10): 3639-3642 .  
Abstract   PDF(pc) (311KB) ( 584 )
Elastic scattering properties of singlet and triplet states of 7Li133Cs at ultralow temperatures are calculated using the constructed potential curves gleaned from high-precision spectroscopy measurement. We show how to reach the scattering length and the number of bound states via the variable phase method. The scattering lengths of the singlet and triplet states of 7Li133Cs are 50.5 a.u. and -135.7 a.u., respectively. We derive two corrections, arising from long range interactions, accurately to at least first order, which provide upper and lower computed bounds to the scattering length. Our results are consistent with the recent experimental data and the theoretical calculation.
Sputtering Induced by Arq+ Impact on Nb Surface
WANG Tie-Shan, CHEN Liang, PENG Hai-Bo, CHENG Rui, XIANG Yang, WANG Yu-Yu, XIAO Guo-Qing
Chin. Phys. Lett. 2008, 25 (10): 3643-3645 .  
Abstract   PDF(pc) (330KB) ( 320 )
The relative sputtering yield induced by highly charged Arq+ impacting on Nb surface is investigated. The yield increases drastically as the incidence angle increases. A formula Y=A*tanB(θ)+C, developed from classical sputtering theory, fits well with the yield. By analysing a series of coefficients A and C extracted by curve fitting, the results demonstrate the presence of a synergy of the linear cascade collision and potential energy deposition.
Optically Forbidden Excitations of 2s Electron of Neon Studied by Fast Electron Impact
GE Min, ZHU Lin-Fan, LIU Cun-Ding, XU Ke-Zun
Chin. Phys. Lett. 2008, 25 (10): 3646-3648 .  
Abstract   PDF(pc) (205KB) ( 359 )
The electron energy loss spectrum in the energy region of 42--48.5eV of neon is measured with an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of 2500eV. Besides the dipole-allowed autoionization transitions of 2s-1np(n=3,4) and 2p-23s3p, the dipole-forbidden ones of 2s-1ns(n=3-6) and 2-13d are observed. The line profile parameters, i.e. Er, Γ and q for these transitions, are determined, and the momentum transfer dependence behaviour is discussed.
Inner Shell Excitations of Lithium Studied by Fast Electron Impact
JIANG Wei-Chun, ZHU Lin-Fan, XU Ke-Zun
Chin. Phys. Lett. 2008, 25 (10): 3649-3651 .  
Abstract   PDF(pc) (405KB) ( 472 )
Electron energy loss spectra for the inner shell excitations of atomic lithium are measured at an incident electron energy of 2500eV and scattering angles of 0°, 2°, 4° and 6°. Two optically forbidden transitions of (1s2s2)2S and (1s2s3S)3s2S are observed. The generalized oscillator strength ratios for
1s(2s2p3P)2P0 to 1s(2s2p1P)2P0 were determined, and they are independent of the momentum transfer.
Three-Photon Resonant Nondegenerate Six-Wave Mixing in a Dressed Atomic System
SUN Jiang, FU Guang-Sheng, SU Hong-Xin, ZUO Zhan-Chun, WU Ling-An, FU Pan-Ming
Chin. Phys. Lett. 2008, 25 (10): 3652-3655 .  
Abstract   PDF(pc) (338KB) ( 432 )
We report a three-photon resonant nondegenerate six-wave mixing (NSWM) in a dressed cascade five-level system. It has advantages that phase match condition is not stringent and NSWM signal is enhanced tremendously due to the multiple resonance with the atomic transition frequencies. In the presence of a strong coupling field, the three-photon resonant NSWM spectrum exhibits Autler--Townes splitting. This technique provides a spectroscopic tool for measuring not only the resonant frequency and dephasing rate but also the transition dipole moment between two highly excited atomic states.
Trichromatic Manipulation of Kerr Nonlinearity in a Three-Level Λ Atomic System
GUO Hong-Ju, NIU Yue-Ping, WANG Li-Chun, JIN Shi-Qi, GONG Shang-Qing
Chin. Phys. Lett. 2008, 25 (10): 3656-3659 .  
Abstract   PDF(pc) (345KB) ( 795 )
Trichromatic manipulation of Kerr nonlinearity in a three-level Λ atomic configuration is investigated theoretically. It is shown that for a weak monochromatic probe field, the enhanced Kerr nonlinearity can be achieved in multiple separate transparent windows due to interference effect of multiple two-photon Raman channels. Furthermore, the property of Kerr nonlinearity can be controlled by the sum of the relative phases of the sideband components of the trichromatic pump field compared to the central component.
Separation of Isotopes via Dynamical Delocalization
Farhan Saif
Chin. Phys. Lett. 2008, 25 (10): 3660-3662 .  
Abstract   PDF(pc) (200KB) ( 496 )
Based on the dynamical de-localization phenomenon we show that different isotopes of a material can be separated. We explain that the suggested scheme can be realized in the laboratory using presently available experimental facilities.
Experimental Realization of Perfect Discrimination for Two Unitary Operations
LIU Jian-Jun, HONG Zhi
Chin. Phys. Lett. 2008, 25 (10): 3663-3665 .  
Abstract   PDF(pc) (421KB) ( 366 )
We experimentally demonstrate perfect discrimination between two unitary operations by using the sequential scheme proposed by Duan et al.[Phys. Rev. Lett. 98 (2007) 100503] Also, we show how to understand the scheme and to calculate the parameters for two-dimensional operations in the picture of the Bloch sphere.
Temporal Characteristic of M--M Transition Lasers in Strontium Atom Vapour
CHEN Gang, CHENG Cheng
Chin. Phys. Lett. 2008, 25 (10): 3666-3669 .  
Abstract   PDF(pc) (444KB) ( 332 )
The kinetic process of Sr atom metastable--metastable transition lasers in He--Sr longitudinal pulsed discharge is analysed and a concise self-consistent physical model is developed. The temporal evolutions of discharge parameters, main particle densities, the electron temperature, and the lasing pulses are numerically calculated. The results provided by the model agree well with the experiment, and the temporal behaviour of each laser pulse is explained successfully by the simulation results.
Monolithic Integration of Sampled Grating DBR with Electroabsorption Modulator by Combining Selective-Area-Growth MOCVD and Quantum-Well Intermixing
LIU Hong-Bo, ZHAO Ling-Juan, PAN Jiao-Qing, ZHU Hong-Liang, ZHOU Fan, WANG Bao-Jun, WANG Wei
Chin. Phys. Lett. 2008, 25 (10): 3670-3672 .  
Abstract   PDF(pc) (438KB) ( 493 )
We present the monolithic integration of a sampled-grating distributed Bragg reflector (SG-DBR) laser with a quantum-well electroabsorption modulator (QW-EAM) by combining ultra-low-pressure (55mbar) selective-area-growth (SAG) metal-organic chemical vapour deposition (MOCVD) and quantum-well intermixing (QWI) for the first time. The QW-EAM and the gain section can be grown simultaneously by using SAG MOCVD technology. Meanwhile, the QWI technology offers an abrupt band-gap change between two functional sections, which reduces internal absorption loss. The experimental results show that the threshold current Ith=62 mA, and output power reaches 3.6mW. The wavelength tuning range covers 30nm, and all the corresponding side mode suppression ratios are over 30dB. The extinction ratios at available wavelength channels can reach more than 14dB with bias of -5 V
A Continuous-Wave Diode-Side-Pumped Tm:YAG Laser with Output 51W
ZHANG Xiao-Fu, XU Yi-Ting, LI Cheng-Ming, ZONG Nan, XU Jia-Lin, CUI Qian-Jin, LU Yuan-Fu, BO Yong, PENG Qin-Jun, CUI Da-Fu, XUZu-Yan
Chin. Phys. Lett. 2008, 25 (10): 3673-3675 .  
Abstract   PDF(pc) (336KB) ( 705 )
A compact diode-side-pumped Tm:YAG laser is presented, which can output 51W of cw power at 2.02μm. The Tm:YAG rod is side pumped by nine diode arrays with the central wavelength of 783nm and the with bandwidth of about 2.5nm at 25°C. To decrease the thermal effect on the both ends and dissipate the heat effectively, one composite Tm:YAG rod with the undoped YAG end caps and the screw threads on the side surface of the rod is used as the laser crystal. The maximum optical-to-optical conversion efficiency of the 2.02-μm laser output is 14.2%, with a slope efficiency of 26.8%..
A Diode-Stack End-Pumped Electro-Optically Q-Switched Nd:YAG Slab Oscillator--Amplifier System
ZHANG Heng-Li, YAN Ying, LI Dai-Jun, SHI Peng, DU Ke-Ming
Chin. Phys. Lett. 2008, 25 (10): 3676-3678 .  
Abstract   PDF(pc) (359KB) ( 1030 )
A laser diode-stack end-pumped electro-optically Q-switched Nd:YAG slab oscillator-amplifier system with near-diffraction-limited output is demonstrated by a stable-unstable hybrid resonator. The average power of 100W at a repetition rate of 10kHz with a pulse width 14.7ns and average
power of 76.3W at a repetition rate of 5kHz with a pulse width of 10.2ns are measured. At the repetition rate of 10kHz and at an output power of 89W, the beam quality factors M2 in the unstable and stable directions are 1.3 and 1.5, respectively.
Highly Efficient Self-Starting Femtosecond Cr:Forsterite Laser
ZHOU Bin-Bin, ZHANG Yong-Dong, ZHONG Xin, WEI Zhi-Yi
Chin. Phys. Lett. 2008, 25 (10): 3679-3681 .  
Abstract   PDF(pc) (234KB) ( 483 )
We report a highly efficient and high power self-starting femtosecond Cr:forsterite laser pumped by a 1064-nm Yb doped fibre laser. Five chirped mirrors are used to compensate for the intra-cavity group-delay dispersion, and the mode-locking is initiated by a semiconductor saturable absorber mirror (SESAM). Under pump power of 7.9W, stable femtosecond laser pulses with average power of 760mW are obtained, yielding a pump power slope efficiency of 12.3%. The measured pulse duration and spectral bandwidth (FWHM) are 46fs and 45nm; the repetition rate is 82MHz.
Generation of Anti-Stokes Line in Fundamental Mode of Photonic Crystal Fibre
WANG Wei, HOU Lan-Tian, LIU Zhao-Lun, ZHOU Gui-Yao,
Chin. Phys. Lett. 2008, 25 (10): 3682-3684 .  
Abstract   PDF(pc) (487KB) ( 425 )
A photonic crystal fibre (PCF) with zero-dispersion wavelength around 800nm is designed and fabricated. Simulated results show that the zero-dispersion wavelength of fundamental mode for this PCF is at 826nm, and phase-matched four-wave mixing can be achieved in fundamental mode. Using 200fs Ti:sapphire laser with central wavelength at 810nm as pump, the anti-Stokes line around 610nm is generated efficiently. The output signal has a Gaussian-like profile, which indicates that the anti-Stokes signal is in the fundamental mode of the PCF. The energy of anti-Stokes signal is higher than that of residual pump laser and the maximum ratio of the anti-Stokes signal to the pump component in the output spectrum is estimated to be 1.2.
Influence of Cascaded Nonlinear Phase Shifts on Second-Harmonic Generation in High-Intensity Pumped QPM Structures
ZHANG Dong-Fang, QIAN Lie-Jia, WANG Ke, ZHU He-Yuan
Chin. Phys. Lett. 2008, 25 (10): 3685-3688 .  
Abstract   PDF(pc) (422KB) ( 407 )

Cascaded nonlinear phase shifts may be imposed on the interacting waves during second-harmonic generation (SHG) in a quasi-phase-matched (QPM) structure, which are severe in high-intensity regime and may result in lower conversion efficiency. We propose a configuration of QPM structure with reduced domain-length, which may depress the nonlinear phase shifts to some extent and lead to an improvement on the conversion efficiency. The numerical analyses on the conversion efficiency as well as the relative phase angle are discussed in detail for better understanding of the SHG process.

Temperature Controlled Filamentation in Argon Gas
CAO Shi-Ying, KONG Wei-Peng, SONG Zhen-Ming, QIN Yu, LI Ru-Xin, WANG Qing-Yue, ZHANG Zhi-Gang,
Chin. Phys. Lett. 2008, 25 (10): 3689-3692 .  
Abstract   PDF(pc) (410KB) ( 372 )
Temperature controlled filamentation is experimentally demonstrated in a temperature gradient gas-filled tube. The proper position of the tube is heated by a furnace and two ends of the tube are cooled by air. The experimental results show that multiple filaments are shrunken into a single filament or no filament only by increasing the temperature at the beginning of the filament. This technique offers another degree of freedom of controlling the filamentation and opens a new way for intense monocycle pulse generation through gradient temperature in a noble gas.
Realization of MMI Power Splitter by UV-light Imprinting Technique Using Hybrid Sol-Gel SiO2 Materials
WANG Yue, WU Yuan-Da, LI Jian-Guang, WANG Hong-Jie, HU Xiong-Wei
Chin. Phys. Lett. 2008, 25 (10): 3693-3695 .  
Abstract   PDF(pc) (500KB) ( 381 )
An efficient fabrication scheme of buried ridge waveguide devices is demonstrated by UV-light imprinting technique using organic-inorganic hybrid sol-gel Zr-doped SiO2 materials. The refractive indices of a guiding layer and a cladding layer for the buried ridge waveguide structure are 1.537 and 1.492 measured at 1550nm, respectively. The tested results show more circular mode profiles due to existence of the cladding layer. A buried ridge single-mode waveguide operating at 1550nm has a low propagation loss (0.088dB/cm) and the 1×2 MMI power splitter exhibits uniform outputs, with a very low splitting loss of 0.029dB at 1549nm.
Impedance-Matched Reduced Acoustic Cloaking with Realizable Mass and Its Layered Design
CHEN Huan-Yang, YANG Tao, LUO Xu-Dong, MA Hong-Ru
Chin. Phys. Lett. 2008, 25 (10): 3696-3699 .  
Abstract   PDF(pc) (351KB) ( 615 )
We present an impedance-matched reduced version of acoustic cloaking whose mass is in a reasonable range. A layered cloak design with isotropic material is also proposed for the reduced cloak. Numerical calculations from the transfer matrix methods show that the present layered cloak can reduce the scattering of an air cylinder substantially.
Turbulent Boundary Layer Control via a Streamwise Travelling Wave Induced by an External Force
QIN Tong, GAO Peng, LIU Nan-Sheng, LU Xi-Yun
Chin. Phys. Lett. 2008, 25 (10): 3700-3703 .  
Abstract   PDF(pc) (817KB) ( 386 )
Turbulent boundary layer control via a streamwise travelling wave is investigated based on direct numerical simulation of an incompressible turbulent channel flow. The streamwise travelling wave is induced on one side wall of the channel by a spanwise external force, e.g., Lorenz force, which is confined in the viscous sublayer. As the control strategy used in this study has never been examined, we pay our attention to its efficiency of drag control. It is revealed that the propagating direction of the travelling wave, i.e., the downstream or upstream propagating direction with respect to the streamwise flow, has an important role on the drag control, leading to a significant drag reduction or enhancement for the parameters considered. The coherent structures of turbulent boundary layer are altered and the underlying mechanisms are analysed. The results obtained provide physical insight into the understanding of turbulent boundary layer control.
Half-Cell Law of Regular Cellular Detonations
WANG Chun, JIANG Zong-Lin, GAO Yun-Liang
Chin. Phys. Lett. 2008, 25 (10): 3704-3707 .  
Abstract   PDF(pc) (413KB) ( 401 )
Numerical simulations illustrate the half-cell law of regular cellular detonations propagating in confined space, i.e., the number of cells always maintains an
integral multiple of half cell. The cells adapt themselves larger or smaller to the size of the unconfined space by maintaining the cell scale larger or smaller than the original cells of detonation.
Observation of Fishbone-Like Instabilities Excited by Energetic Electrons on the HL-2A Tokamak
CHEN Wei, DING Xuan-Tong, LIU Yi, YUAN Guo-Liang, ZHANG Yi-Po, DONG Yun-Bo, SONG Xian-Ying, ZHOU Jun, SONG Xian-Ming, DENG Wei, YANG Qing-Wei
Chin. Phys. Lett. 2008, 25 (10): 3708-3711 .  
Abstract   PDF(pc) (909KB) ( 351 )
Strong burst of an internal kink mode is observed on the HL-2A tokamak. Features of the fishbone-like mode are presented. The fishbone-like instabilities can be driven during electron cyclotron resonance heating (ECRH) and can be excited on the high field side (HFS) by ECRH. It is found for the first time that the modes also present themselves on the low field side (LFS) during ECRH. Experiments show that the energetic electrons with energy of 35--70keV play a dominant role in the excitation mechanism, and the experimental results are also consistent with our calculation ones.
Numerical Simulation of Plasma Antenna with FDTD Method
LIANG Chao, XU Yue-Min, WANG Zhi-Jiang
Chin. Phys. Lett. 2008, 25 (10): 3712-3715 .  
Abstract   PDF(pc) (580KB) ( 1238 )
We adopt cylindrical-coordinate FDTD algorithm to simulate and analyse a 0.4-m-long column configuration plasma antenna. FDTD method is useful for solving electromagnetic problems, especially when wave characteristics and plasma properties are self-consistently related to each other. Focus on the frequency from 75MHz to 400MHz, the input impedance and radiation efficiency of plasma antennas are computed. Numerical results show that, different from copper antenna, the characteristics of plasma antenna vary simultaneously with plasma frequency and collision frequency. The property can be used to construct dynamically reconfigurable antenna. The investigation is meaningful and instructional for the optimization of plasma antenna design.
Effect of Pulse Width and Fluence of Femtosecond Laser on Electron--Phonon Relaxation Time
FANG Ran-Ran, ZHANG Duan-Ming WEI Hua, LI Zhi-Hua, YANG Feng-Xia, TAN Xin-Yu
Chin. Phys. Lett. 2008, 25 (10): 3716-3719 .  
Abstract   PDF(pc) (639KB) ( 652 )
The electron--phonon relaxation time as functions of pulse width and fluence of femtosecond laser is studied based on the two-temperature model. The two-temperature model is solved using a finite difference method for copper target. The temperature distribution of the electron and the lattice along with
space and time for a certain laser fluence is presented. The time-dependence of lattice and electron temperature of the surface for different pulse width and different laser fluence are also performed, respectively. Moreover, the variation of heat-affected zone per pulse with laser fluence is obtained. The satisfactory agreement between our numerical results and experimental data
indicates that the electron--phonon relaxation time is reasonably accurate with the influences of pulse width and fluence of femtosecond laser.
Effects of Helium and Oxygen Common Implantation in Silicon Wafer
LI Bing-Sheng, ZHANG Chong-Hong, ZHOU Li-Hong, YANG Yi-Tao,
Chin. Phys. Lett. 2008, 25 (10): 3720-3723 .  
Abstract   PDF(pc) (443KB) ( 589 )
Defect engineering for SiO2 precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen (SIMOX). Cavities are created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120keV 8.0×1016cm-2 O ions. The O ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectional transmission electron microscopy (XTEM), Fourier transform infrared absorbance spectrometry (FTIR) and atomic force microscopy (AFM) measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation
Planar Channelling Criticalities of MeV Protons in Si Crystal: Simulations, Evaluation and Applications
Mukhtar Ahmed Rana
Chin. Phys. Lett. 2008, 25 (10): 3724-3727 .  
Abstract   PDF(pc) (664KB) ( 428 )
We reports a phase-space structure of MeV proton beam planar channelled along {110} planes in Si crystal using simulation results with the help of a computer code FLUX. The aim is to understand channelling conditions suitable for disorder measurement in crystals. Phase-space distribution of a planar channelled proton beam evolutes in a systematic fashion when it travels into the crystal. Planar channelled beam oscillates between phase-like and space-like conditions in which a part of the beam becomes under phase and space criticalities. These criticality conditions in planar channelling are analysed, explained and discussed with the perspective of defect measurement in crystals.
NO--CO--O2 Reaction on a Metal Catalytic Surface using Eley--Rideal Mechanism
Waqar Ahmad
Chin. Phys. Lett. 2008, 25 (10): 3728-3731 .  
Abstract   PDF(pc) (280KB) ( 418 )
Interactions among the reacting species NO, CO and O2 on metal catalytic surfaces are studied by means of Monte Carlo simulation using the Eley--Rideal (ER) mechanism. The study of this three-component system is important for understanding of the reaction kinetics by varying the relative ratios of the reactants. It is found that contrary to the conventional Langmuir--Hinshelwood (LH) thermal mechanism in which two irreversible phase transitions are obtained between active states and poisoned states, a single phase transition is observed when the ER mechanism is combined with the LH mechanism. The phase diagrams of the surface coverage and the steady state production of CO2, N2 and N2O are evaluated as a function of the partial pressures of the reactants in the gas phase. The continuous production of CO2 starts as soon as the CO pressure is switched on and the second order phase transition at the first critical point is eliminated, which is in agreement with the experimental findings.
Effect of Temperature and Ionic Concentration on Self-Assembled Films of Chicago Sky Blue
D. Dey, M. N. Islam, S. A. Hussain, D. Bhattacharjee
Chin. Phys. Lett. 2008, 25 (10): 3732-3734 .  
Abstract   PDF(pc) (401KB) ( 549 )
We employ a layer-by-layer adsorption technique for deposition on solid substrates of polyionic films of Chicago Sky Blue. Film growth was significant with the increasing number of layers. Photochemical properties of these films are investigated for different ionic concentrations. A significant blue shift is observed with the increasing ionic strength of the solution, suggesting the formation of aggregation. Temperature effect studies show some preferable reorientation of molecules in the film during cooling process. Most remarkable observation is that the absorption intensity is the highest for a particular degree of inclination. Deposition time is fixed at 15min because adsorption kinetics results show saturation after 15min.
First-Principles Calculation of Electronic Structure and Optical Properties of Sb-Doped ZnO
ZHANG Fu-Chun, ZHANG Zhi-Yong, ZHANG Wei-Hu, YAN Jun-Feng, YUN Jiang-Ni
Chin. Phys. Lett. 2008, 25 (10): 3735-3738 .  
Abstract   PDF(pc) (639KB) ( 863 )
The geometric structure, electronic structure, optical properties and the formation energy of Sb-doped ZnO with the wurtzite structure are investigated using the first-principles ultra-soft pseudo-potential approach of plane wave based upon the density functional theory. The calculated results indicate that the volume of ZnO doped with Sb becomes larger, and the doping system yields the lowest formation energy of Sb on the interstitial site and the oxygen site. Furthermore, Sb dopant first occupies the octahedral oxygen sites of the wurtzite structure. It is found that Sb substituting on oxygen site behaves as a deep acceptor and shows the p-type degenerate semiconductor character. After doping, the electron density difference demonstrates the considerable electron charge density redistribution, which induces the effect of Sb-doped ZnO to increase the charge overlap between atoms. The density of states move towards lower energy and the optical band gap is broadened. Our calculated results are in agreement with other experimental results and could make more precise monitoring and controlling possible during the growth of ZnO p-type materials.
Spin Polarization and Andreev Conductance through a Diluted Magnetic Semiconductor Quantum Wire with Spin--Orbit Interaction
LI Yu-Xian
Chin. Phys. Lett. 2008, 25 (10): 3739-3741 .  
Abstract   PDF(pc) (259KB) ( 414 )
Spin-dependent Andreev reflection and spin polarization through a diluted magnetic semiconductor quantum wire coupled to normal metallic and superconductor electrodes are investigated using scattering theory. When the spin--orbit coupling is considered, more Andreev conductance steps appear at the same Fermi energy. Magnetic semiconductor quantum wire separates the spin-up and spin-down electrons. The Fermi energy, at which different-spin-state electrons begin to separate, becomes lower due to the effect of the spin--orbit interaction. The spin filter effect can be measured more easily by investigating the Andreev conductance than by investigating the normal conductance.
Thermal Stability of Reliable Polycrystalline Zirconium Oxide for Nonvolatile Memory Application
ZHOU Peng, LI Jing, CHEN Liang-Yao, TANG Ting-Ao, LIN Yin-Yin
Chin. Phys. Lett. 2008, 25 (10): 3742-3745 .  
Abstract   PDF(pc) (534KB) ( 513 )
Thermal stability of resistive switching of stoichiometric zirconium oxide thin films is investigated for high yielding nonvolatile memory application. The
Al/ZrO2/Al cell fabricated in the conventional device process shows highly reliable switching behaviour between two distinct stable resistance states. The retention capabilities are also tested under various conditions and temperatures. The excellent performance of Al/ZrO2/Al cell can be explained by assuming that anode/ZrO2 interface exists and by conducting filament
forming/rupture mechanism. The device failure is illustrated in terms of permanent conducting filaments formation.
Electronic Raman Scattering in Graphene
LU Hong-Yan, WANG Qiang-Hua
Chin. Phys. Lett. 2008, 25 (10): 3746-3749 .  
Abstract   PDF(pc) (413KB) ( 604 )
Linear dispersion near the Dirac points in the band structure of graphenes can give rise to novel physical properties. We calculate the electronic contribution to the Raman spectra in graphenes, which also shows novel features. In the clean limit, the Raman spectrum in the undoped graphene is linear (with a universal slope against impurity scattering) at low energy due to the linear dispersion near the Dirac points, and it peaks at a position corresponding to the van Hove singularity in the band structure. In a doped graphene, the electronic Raman absorption is forbidden up to a vertical inter-band particle--hole gap. Beyond the gap the spectrum follows the undoped case. In the presence of impurities, absorption within the gap (in the otherwise clean case) is induced, which is identified as the intra-band contribution. The Drude-like intra-band contribution is seen to be comparable to the higher energy inter-band Raman peak. The results are discussed in connection to experiments.
Chemical Structure of HfO2/Si Interface with Angle-Resolved Synchrotron Radiation Photoemission Spectroscopy
TAN Ting-Ting, LIU Zheng-Tang, LIU Wen-Ting, ZHANG Wen-Hua
Chin. Phys. Lett. 2008, 25 (10): 3750-3752 .  
Abstract   PDF(pc) (390KB) ( 383 )

Interfacial chemical structure of HfO2/Si (100) is investigated using angle-resolved synchrotron radiation photoemission spectroscopy (ARPES). The chemical states of Hf show that the Hf 4f binding energy changes with the probing depth and confirms the existence of Hf--Si--O and Hf--Si bonds. The Si 2p spectra are taken to make sure that the interfacial structure includes the Hf silicates, Hf silicides and SiOx. The metallic characteristic of the Hf--Si bonds is confirmed by the valence band spectra. The depth distribution model of this interface is established.

Modified SQUID Operator Equation for a Single-Qubit Structure Coupled to a Quantum Resonator
LIANG Bao-Long, WANG Ji-Suo, FAN Hong-Yi, MENG Xiang-Guo
Chin. Phys. Lett. 2008, 25 (10): 3753-3756 .  
Abstract   PDF(pc) (203KB) ( 376 )
Role of self-inductance in superconducting quantum interference device (SQUID) charge qubit is considered. It is found that when an SQUID charge qubit is coupled to a quantum LC resonator, the SQUID voltage operator equation is modified in accompanying with the modification of operator Faraday equation describing the inductance. It is shown that when the extra energy is applied to the junction, the mean phase will be squeezed according to a damping factor.
Quantum Spontaneous Magnetization in Single-Junction Superconducting π-Rings
TIAN Ye, ZHU Xue-Min, LIU Dang-Ting, ZHAO Shi-Ping, CHEN Geng-Hua
Chin. Phys. Lett. 2008, 25 (10): 3757-3760 .  
Abstract   PDF(pc) (429KB) ( 379 )
Based upon the calculations of energy levels and quantum states, we discuss the probability of quantum spontaneous magnetization flux as a function of the screen parameter β for the superconducting ring containing one Josephson π-junction, and compare the result with that in the classical case. Our results indicate that there is significant difference in the magnetization behaviour around β=1 between the quantum and classical situations.
Pseudogap and Superconducting Gap in SmFeAs(O1-xFx) Superconductor from Photoemission Spectroscopy
Hai-Yun, JIA Xiao-Wen, ZHANG Wen-Tao, ZHAO Lin, MENG Jian-Qiao, LIU Guo-Dong, DONG Xiao-Li, WU Gang, LIU Rong-Hua, CHEN Xian-Hui, REN Zhi-An, YI Wei, CHE Guang-Can, CHEN Gen-Fu, WANG Nan-Lin, WANG Gui-Ling, ZHOU Yong, ZHU Yong, WANG Xiao-Yang, ZHAO Zhong-Xian, XU Zu-Yan, CHEN Chuang-Tian, ZHOU Xing-Jiang
Chin. Phys. Lett. 2008, 25 (10): 3761-3764 .  
Abstract   PDF(pc) (784KB) ( 529 )

High resolution photoemission measurements are carried out on non-superconducting SmOFeAs parent compound and superconducting SmFeAs(O1-xFx) (x=0.12, and 0.15) compounds. The momentum-integrated spectra exhibit a clear Fermi cutoff that shows little leading-edge shift in the superconducting state. A robust feature at 13meV is identified in all these samples. Spectral weight suppression near EF with decreasing temperature is observed in both undoped and doped samples that points to a possible existence of a pseudogap in these Fe-based compounds.

Common Features in Electronic Structure of the Oxypnictide Superconductors from Photoemission Spectroscopy
JIA Xiao-Wen, LIU Hai-Yun, ZHANG Wen-Tao, ZHAO Lin, MENG Jian-Qiao, LIU Guo-Dong, DONG Xiao-Li, WU Gang, LIU Rong-Hua, CHEN Xian-Hui, REN Zhi-An, YI Wei, CHE Guang-Can, CHEN Gen-Fu, WANG Nan-Lin, WANG Gui-Ling, ZHOU Yong, ZHU Yong, WANG Xiao-Yang, ZHAO Zhong-Xian, XU Zu-Yan, CHEN Chuang-Tian, ZHOU Xing-Jiang
Chin. Phys. Lett. 2008, 25 (10): 3765-3768 .  
Abstract   PDF(pc) (907KB) ( 482 )

High resolution photoemission measurements are carried out on non-superconducting LaFeAsO parent compound and various superconducting RFeAs(O1-xFx) (R=La, Ce and Pr) compounds. It is found that the parent LaFeAsO compound shows a metallic character. By extensive measurements, several common features are identified in the electronic structure of these Fe-based compounds: (1) 0.2eV feature in the valence band, (2) a universal 13--16meV feature, (3) near EF spectral weight suppression with decreasing temperature. These universal features can provide important information about band structure, superconducting gap and pseudogap in these Fe-based materials.

Large Magnetoresistance Based on Double Spin Filter Tunnel Barriers
TANG Xiao-Li, ZHANG Huai-Wu, SU Hua, JING Yu-Lan
Chin. Phys. Lett. 2008, 25 (10): 3769-3772 .  
Abstract   PDF(pc) (409KB) ( 351 )

We propose and theoretically analyse a double magnetic tunnel device that takes advantages of the spin filter effect. Two magnetic tunnel barriers are formed by different spin filters which have different barrier heights. The magnetoresistance of the device is low (high) when the magnetic moments of the two spin filters are parallel (antiparallel). We present a theoretical calculation of the magnetoresistance based on electric tunnel effect. In addition, the effect of the difference barrier heights and exchange splitting energies between the two spin filters are also analysed in detail. The numerical results show that the spin filter in this configuration gives a magnetoresistance larger than that with standard magnetic tunnel junctions.

Correlation between Electroresistance and Magnetoresistance in Slight Oxygen-Deficient Nd0.67Sr0.33MnO3-δ Polycrystalline Ceramics
YANG Chang-Ping, DENG Heng, CHEN Shun-Sheng, WANG Hao, WEN Zhen-Chao, HAN Xiu-Feng, K. Bä, rner
Chin. Phys. Lett. 2008, 25 (10): 3773-3775 .  
Abstract   PDF(pc) (366KB) ( 398 )
A colossal electroresistance effect is found in Nd0.67Sr0.33MnO3-δ polycrystalline ceramics with a very slight oxygen deficiency δ = 0.05. The electroresistance behaviour of Nd0.67Sr0.33MnO3-δ(δ= 0.0 ) displays the striking similarity to its counterpart magnetoresistance. It reveals that the boundary effect plays an important role in electroresistance and the same physical origin is likely responsible for both magnetoresistance and electroresistance effects in Nd0.67Sr0.33MnO3-δ polycrystals.
Effects of Li Substitution and Sintering Temperature on Properties of Bi0.5(Na,K)0.5TiO3 Lead-Free Piezoelectric Ceramics
MING Bao-Quan, WANG Jin-Feng, ZANG Guo-Zhong
Chin. Phys. Lett. 2008, 25 (10): 3776-3778 .  
Abstract   PDF(pc) (362KB) ( 490 )
Bi0.5(Na0.72K0.28-xLix)0.5TiO3 (BNKLT-100x) lead-free piezoelectric ceramics are synthesized by conventional solid state sintering techniques. The dielectric and piezoelectric properties of the BNKLT-100x ceramics as a function of Li content are systematically investigated. It is found that not only Li content but also the sintering temperature has a strong effect on the piezoelectric properties of BNKLT. The piezoelectric constant d33 of BNKLT varies from 120 to 252pC/N in the Li content range from 0.03 to 0.16. In the sintering temperature range from 1080 to 1130°C, the d33 value of BNKLT-6 changes from 200pC/N to 252pC/N. The BNKLT-6 sample sintered at 1100°C has the highest piezoelectric constant d33 of 252pC/N, with the electromechanical coupling factors kp of 0.32 and kt of 0.44.
Enhanced Laser Cooling of Rare-Earth-Ion-Doped Composite Material
JIA You-Hua, ZHONG Biao, JI Xian-Ming, YIN Jian-Ping
Chin. Phys. Lett. 2008, 25 (10): 3779-3782 .  
Abstract   PDF(pc) (262KB) ( 382 )
We predict enhanced laser cooling performance of rare-earth-ions-doped glasses containing nanometre-sized ultrafine particles, which can be achieved by the enhancement of local field around rare earth ions, owing to the surface plasma resonance of small metallic particles. The influence of energy transfer between ions and the particle is theoretically discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption is predicted. It is concluded that the absorption are greatly enhanced in these composite materials, the cooling power is increased as compared to the bulk material.
Ultraviolet Luminescence Depending on Zn Interstitial in ZnO Polycrystalline Films
XU Xiao-Qiu, TIAN Ke, SHI Yuan-Yuan, ZHONG Sheng, ZHANG Wei-Ying, FU Zhu-Xi
Chin. Phys. Lett. 2008, 25 (10): 3783-3786 .  
Abstract   PDF(pc) (531KB) ( 650 )

The ultraviolet emission line at 3.315eV is observed at 8K in ZnO polycrystalline films and investigated by temperature-dependent photoluminescence spectra and cathodoluminescence spatial image. The relative intensity of 3.315eV emission line depends strongly on growth and annealing conditions. The cathodoluminescence image shows that the 3.315eV emission localizes on the surface and ridge of ZnO grain. These results suggest that the 3.315eV emission attributes to Zn interstitials at the grain surface and ridge. This emission is stable in the range from 8K to 300K and contributes to the room temperature ultraviolet band.

Structural and Photoluminescence Properties of β-Ga2O3 Nanofibres Fabricated by Electrospinning Method
ZHAO Jian-Guo, ZHANG Zhen-Xing, MA Zi-Wei, DUAN Hui-Gao, GUO Xiao-Song, XIE Er-Qing
Chin. Phys. Lett. 2008, 25 (10): 3787-3789 .  
Abstract   PDF(pc) (500KB) ( 658 )
We have prepared the β-Ga2O3 nanofibres by electrospinning method followed by calcining in air at 900°C. The morphology and structure of the nanofibres are characterized by field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD) and Raman technique. These nanofibres have diameters ranging from 60 to 130nm and lengths up to several millimetres. Photoluminescence (PL) spectrum under excitation at 325nm shows that these β-Ga2O3 nanofibres have a blue emission peaking at 466nm, which may be attributed to defects such as the oxygen vacancies, gallium vacancies and gallium-oxygen vacancy pairs.
VUV/UV/X-Ray Excited Luminescent Properties of Eu3+ nd Pr3+ Doped BiSbO4
LI Hui-Liang, WANG Xiao-Jun, YUAN Jun-Lin, ZHAO Jing-Tai, YANG Xin-Xin, ZHANG Zhi-Jun, CHEN Hao-Hong, ZHANG Guo-Bin, SHI Chao-Shu
Chin. Phys. Lett. 2008, 25 (10): 3790-3793 .  
Abstract   PDF(pc) (521KB) ( 564 )

Absorption spectra of BiSbO4 are studied. The electronic structure calculated by the DFT shows that BiSbO4 is a semiconductor, with direct band gap 2.96 eV, which is consistent with UV-visible diffuse reflectance experiment. The host lattice emission band is located at 440 nm under VUV excitation. Eu3+ and Pr3+ doped samples have high luminescence efficiency in emitting red and green light, respectively. From the partial density of states, Eu3+ doped emitting spectrum, and the host crystal structure parameters, the relationship between structure and optical properties is discussed. It is found that the Eu3+ ions occupied Bi3+ sites, and there could be an energy transfer from Bi3+ ions to RE3+ ions.

Synthesizing of ZnO Micro/Nanostructures at Low Temperature with New Reducing Agents
LI Hong-Dong, LÜ, Hang, SANG Dan-Dan, LI Dong-Mei LI Bo, LÜ, Xian-Yi, ZOU Guang-Tian
Chin. Phys. Lett. 2008, 25 (10): 3794-3797 .  
Abstract   PDF(pc) (618KB) ( 589 )
Instead of the conventional graphite, new additional reducing agents (diamond, silicon, metal elements, etc.) have been mixed with zinc oxide (ZnO) powder to fabricate ZnO micro/nanostructures by a thermal vapour transport method. Due to the strong reducibility for those additions, the corresponding heating temperature is decreased by 100-500°C compared to the case of graphite, which subsequently decreases the corresponding growth temperature for the products. Being placed separately for the powder sources of ZnO and addition, a vapour--vapour reduction--oxidation reaction mechanism between the sources is proposed as an important channel to fabricate ZnO. Photoluminescence and magnetic examinations indicate that the ZnO products synthesized have strong ultraviolet (visible) emissions and are room-temperature ferromagnetic, meaning that the products are available for applications.
Demonstration of a 4H SiC Betavoltaic Nuclear Battery Based on Schottky Barrier Diode
QIAO Da-Yong, YUAN Wei-Zheng, GAO Peng, YAO Xian-Wang, ZANG Bo, ZHANG Lin, GUO Hui, ZHANG Hong-Jian
Chin. Phys. Lett. 2008, 25 (10): 3798-3800 .  
Abstract   PDF(pc) (303KB) ( 1556 )
A 4H SiC betavoltaic nuclear battery is demonstrated. A Schottky barrier diode is utilized for carrier separation. Under illumination of Ni-63 source with an apparent activity of 4mCi/cm2, an open circuit voltage of 0.49V and a short circuit current density of 29.44nA/cm2 are measured. A power conversion efficiency of 1.2%} is obtained. The performance of the device is limited by low shunt resistance, backscattering and attenuation of electron energy in air and Schottky electrode. It is expected to be significantly improved by optimizing the design and processing technology of the device.
Effects of Al and Ti/Cu on Synthesis of Type-IIa Diamond Crystals in Ni70Mn25Co5-C System at HPHT
LI Shang-Sheng, JIA Xiao-Peng, ZANG Chuan-Yi, TIAN Yu, ZHANG Ya-Fei, XIAO Hong-Yu, HUANG Guo-Feng, MA Li-Qiu, LI Yong, LI Xiao-Lei, MA Hong-An
Chin. Phys. Lett. 2008, 25 (10): 3801-3804 .  
Abstract   PDF(pc) (425KB) ( 651 )

High-quality type-IIa gem diamond crystals are successfully synthesized in a Ni70Mn25Co5-C system by temperature gradient method (TGM) at about 5.5GPa and 1560K. Al and Ti/Cu are used as nitrogen getters respectively. While nitrogen getter Al or Ti/Cu is added into the synthesis system, some inclusions and caves tend to be introduced into the crystals. When Al is added into the solvent alloy, we would hardly gain high-quality type-IIa diamond crystals with nitrogen concentration Nc< 1ppm because of the reversible reaction of Al and N at high pressure and high temperature (HPHT). However, when Ti/Cu is added into the solvent alloy, high-quality type-IIa diamond crystals with Nc < 1ppm can be grown by decreasing the growth rate of diamonds.

Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma
HU Wen-Juan, XIE Fen-Yan, CHEN Qiang, WENG Jing
Chin. Phys. Lett. 2008, 25 (10): 3805-3807 .  
Abstract   PDF(pc) (809KB) ( 502 )

We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C--O--C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C--O--C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

Undercooling and Unidirectional Solidification of CuNi Alloy Melts
WANG Qiang, MA Ming-Zhen, JING Qin, LI Gong, QI Li, ZHANG Xin-Yu, WANG Wen-Kui, LIU Ri-Ping
Chin. Phys. Lett. 2008, 25 (10): 3808-3810 .  
Abstract   PDF(pc) (809KB) ( 404 )

Cylinder-shaped Cu80Ni20 alloy melt is undercooled and solidified by the combination of the electromagnetic levitation technique and the flux treatment method. Nearly constant temperature gradient of 8-10K/cm is realized for the cylindrical melts with different undercooling levels at the bottom ends. The experimental results reveal that with the increase of the undercooling of the melts from 35 to 220K, the microstructures undergo transition from coarse dendrites to granular grains, unidirectional dendrites, and finally to equiaxed grains.

An in-situ Observation on Initial Aggregation Process of Colloidal Particles near Three-Phase Contact Line of Air, Water and Vertical Substrate
YAO Can, WANG Yu-Ren, LAN Ding, DUAN Li, KANG Qi
Chin. Phys. Lett. 2008, 25 (10): 3811-3814 .  
Abstract   PDF(pc) (389KB) ( 334 )
The self-assembling process near the three-phase contact line of air, water and vertical substrate is widely used to produce various kinds of nanostructured materials and devices. We perform an in-situ observation on the self-assembling process in the vicinity of the three phase contact line. Three kinds of aggregations, i.e. particle--particle aggregation, particle--chain aggregation and chain--chain aggregation, in the initial stage of vertical deposition process are revealed by our experiments. It is found that the particle--particle aggregation and the particle--chain aggregation can be qualitatively explained by the theory of the capillary immersion force and mirror image force, while the chain--chain aggregation leaves an opening question for the further studies. The present study may provide more deep insight into the self-assembling process of colloidal particles.
A 0.18-μm 3.3V 16k Bits 1R1T Phase Change Random Access Memory (PCRAM) Chip
DING Sheng, SONG Zhi-Tang, LIU Bo, ZHU Min, CHEN Xiao-Gang, CHEN Yi-Feng, SHEN Ju, FU Cong, FENG Song-Lin
Chin. Phys. Lett. 2008, 25 (10): 3815-3817 .  
Abstract   PDF(pc) (410KB) ( 578 )

Using standard 0.18-μm CMOS process and the special platform for 8-inch phase change random access memory (PCRAM), the first Chinese 16k bits PCRAM chip has been successfully achieved. A 1R1T structure has been designed for low voltage drop and low cost compared to the 1R1D structure and the BJT-switch structure. Full integration of the 16k bits PCRAM chip, including memory cell, array structure, critical circuit module, and physical layout, has been designed and verified. The critical integration technology of the phase change material (PCM) fabrication and the standard CMOS process has been solved. Test results about PCM in a large-scale array have been generated for the next research of PCRAM chip.

Electric Field-Induced Fluid Velocity Field Distribution in DNA Solution
ZHANG Ling-Yun, WANG Peng-Ye
Chin. Phys. Lett. 2008, 25 (10): 3818-3821 .  
Abstract   PDF(pc) (318KB) ( 432 )

We present an analytical solution for fluid velocity field distribution of polyelectrolyte DNA. Both the electric field force and the viscous force in the DNA solution are considered under a suitable boundary condition. The solution of electric potential is analytically obtained by using the linearized Poisson--Boltzmann equation. The fluid velocity along the electric field is dependent on the cylindrical radius and concentration. It is shown that the electric field-induced fluid velocity will be increased with the increasing cylindrical radius, whose distribution also varies with the concentration

Cascading Failures of Complex Networks Based on Two-Step Degree
WU Zhi-Hai, FANG Hua-Jing
Chin. Phys. Lett. 2008, 25 (10): 3822-3825 .  
Abstract   PDF(pc) (341KB) ( 455 )

We propose a new concept, two-step degree. Defining it as the capacity of a node of complex networks, we establish a novel capacity--load model of cascading failures of complex networks where the capacity of nodes decreases during the process of cascading failures. For scale-free networks, we find that the average two-step degree increases with the increase of the heterogeneity of the degree distribution, showing that the average two-step degree can be used for measuring the heterogeneity of the degree distribution of complex networks. In addition, under the condition that the average degree of a node is given, we can design a scale-free network with the optimal robustness to random failures by maximizing the average two-step degree.

Effect Attack on Scale-Free Networks due to Cascading Failures
WANG Jian-Wei, RONG Li-Li
Chin. Phys. Lett. 2008, 25 (10): 3826-3829 .  
Abstract   PDF(pc) (398KB) ( 647 )

Adopting the initial load of a node j to be Lj = [kj(∑m∈Γjkm)]α with kj and Γj being the degree of the node j and the set of its neighbouring nodes respectively, we propose a cascading model based on a local preferential redistribution rule of the load after removing a node. Assuming that a failed node leads only to a redistribution of the load passing through it to its neighbouring nodes, we explore the response of scale-free networks subject to two different attack strategies on nodes and find some interesting and counterintuitive results in our cascading model. On the one hand, unexpectedly, the attack on the nodes with the lowest degree is more harmful than the attack on the highest degree nodes when α<1/2. On the other hand, when α=1/2, the effects of two attacks for the robustness against cascading failures are almost identical. In addition, the numerical simulations are also verified by the theoretical analysis. These results may be very helpful for real-life networks to protect the key nodes selected effectively and to avoid cascading-failure-induced disasters.

Water Vapour Potential Vorticity and Its Applications in Tropical Cyclones
GAO Shou-Ting, ZHOU Fei-Fan,
Chin. Phys. Lett. 2008, 25 (10): 3830-3833 .  
Abstract   PDF(pc) (828KB) ( 553 )

A new tracer is presented to diagnose tropical cyclones (TCs) and their correspondent rainfall. It is defined as water vapour potential vorticity (WPV) by replacing potential temperature with specific humidity in the potential vorticity (PV). The WPV is compared with PV and moist potential vorticity (MPV) in diagnosing three tropical cyclone cases occurred in North-West Pacific during 10 July to 21 July 2005 (Haitang), 30 July to 9 August 2005 (Matsa) and 25 September to 3 October 2005 (Longwang) separately. The results show that in tracing the track of TCs, WPV is not nicer than PV but better than MPV. While diagnosing TCs' onshore rainfall, WPV is better than MPV in all the three cases. Moreover, the advection of WPV is a good indication of TC rainfall after its landing.

Viscous Dark Energy Models with Variable G and Λ
Arbab I. Arbab
Chin. Phys. Lett. 2008, 25 (10): 3834-3836 .  
Abstract   PDF(pc) (162KB) ( 464 )
We consider a cosmological model with bulk viscosity η and variable cosmological Λ∝ρ , alpha= const and gravitational G constants. The model exhibits many interesting cosmological features. Inflation proceeds du to the presence of bulk viscosity and dark energy without requiring the equation of state p=-ρ. During the inflationary era the energy density ρ does not remain constant, as in the de-Sitter type. Moreover, the cosmological and gravitational constants increase exponentially with time, whereas the energy density and viscosity decrease exponentially with time. The rate of mass creation during inflation is found to be very huge suggesting that all matter in the universe is created during inflation.
86 articles