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Volume 17 Issue 5
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Original Articles
Monte Carlo Simulation of Argon in Nano-Space
CHEN Min, YANG Chun, GUO Zeng-Yuan
Chin. Phys. Lett. 2000, 17 (5): 313-315 .  
Abstract   PDF(pc) (214KB) ( 343 )
Monte Carlo simulations are performed to investigate the thermodynamic properties of argon confined in nano-scale cubes constructed of graphite walls. A remarkable depression of the system pressures is observed. The simulations reveal that the length-scale of the cube, the magnitude of the interaction between the fluid and the graphite wall and the density of the Auid exhibit reasonable effects on the thermodynamic property shifts of the fluid.
Einstein-Podolsky-Rosen Entanglement and Quantum Nonlocality for an Electron in a Uniform Magnetic Field
FAN Hong-Yi, CHEN Zeng-Bing
Chin. Phys. Lett. 2000, 17 (5): 316-318 .  
Abstract   PDF(pc) (214KB) ( 386 )
We show that there exists the precise Einstein-Podolsky-Rosen entanglement for an electron in a uniform magnetic field. Specifically, the x- and y-coordinates of the electron as well as the corresponding canonical momenta px and py become sharply correlated, which is a novel fact unnoticed before. When a harmonic potential is added to the system, the original vacuum state of the system becomes a squeezed vacuum state, whose quantum nonlocality is then demonstrated.

Solving a Generalized Jaynes-Cummings Model by Supersymmetric Unitary Transformation
LU Huai-Xin, WANG Xiao-Qin, FAN Hong-Yi
Chin. Phys. Lett. 2000, 17 (5): 319-320 .  
Abstract   PDF(pc) (126KB) ( 388 )
For the generalized Jaynes-Cummings model Hamiltonian which can describe two collectively radiation atoms, we find its supersymmetric structure. Based on supersymmetric quantum mechanics theory, we introduce a supersymmetric unitary transformation, in which the supersymmetric unitary transformation operator can be constructed by supersymmetric generators of the super-Lie algebra, to diagonalize the Hamiltonian. On doing so, its eigenvalue and eigenstates are obtained.
Realization of Quantum Logic Gates in Ion Traps Without Any Requirement on the Lamb-Dicke Parameter
ZHENG Shi-Biao, FENG Mang, ZHU Xi-Wen
Chin. Phys. Lett. 2000, 17 (5): 321-323 .  
Abstract   PDF(pc) (218KB) ( 1138 )
A scheme is presented for realizing quantum logic gate in an ion trap. In the scheme the state of the mth ion is first replicated onto the collective motion. Then a transformation, conditional on the motional state, is performed on the nth ion. Finally the motional state is replicated back onto the mth ion. By this way the quantum logic-gate between the mth and the nth ions is realized. The scheme does not put any requirement on the Lamb-Dicke parameter.
Proposed New Test of Equivalence Principle from Rotating Bodies
ZHANG Yuan-Zhong, LUO Jun, NIE Yu-Xin
Chin. Phys. Lett. 2000, 17 (5): 324-325 .  
Abstract   PDF(pc) (136KB) ( 334 )
We study a new kind of equivalence principle for rotating bodies and propose a test of the equivalence principle by comparing free-fall gravitational accelerations of two gyroscopes or a rotating and a non-rotating extended bodies.

Absorbing Charged Rotating Metric in de Sitter Space in Advanced Time Coordinates and the Related Energy-Momentum Tensor
XU Dian-Yan
Chin. Phys. Lett. 2000, 17 (5): 326-328 .  
Abstract   PDF(pc) (145KB) ( 579 )
Absorbing charged rotating (ACR) metric in de Sitter space and related energy-momentum tensor are derived. The ACR metric is very simple in advanced time coordinates. The ACR metric involves 8 independent parameters which are divided into two classes: (1) the mass M, charge Q, angular momentum per unit mass a, and cosmological constant Λ ; (2)∂M/∂v, ∂2M/∂v2, ∂Q/∂v, and ∂2Q/∂v2. The non-stationary part of the energy-momentum tensor is positive definite everywhere.

Spherically Symmetric Static Solution for a Schwarzschild Black Hole with Its Hawking Radiation
HUANG Chao-Guang
Chin. Phys. Lett. 2000, 17 (5): 329-331 .  
Abstract   PDF(pc) (258KB) ( 703 )
A black hole and its Hawking radiation may be in stable thermal equilibrium. In this letter, the static spherically symmetric numerical solution for a Schwarzschild black hole with its Hawking radiation are obtained. In the calculation, the equilibrium system is supposed to consist of a black hole, thermal radiation and a two-dimensional surface layer. The solutions obtained are compared with the York’s back-reaction approach and the Zhao-Liu thermodynamic approach.
Dynamic Behavior of Phase Synchronization of Chaos
ZHAN Meng, HU Gang, WANG Xin-Gang
Chin. Phys. Lett. 2000, 17 (5): 332-334 .  
Abstract   PDF(pc) (288KB) ( 536 )
The dynamic nature of phase synchronization between chaotic outputs and injected periodic signals is investigated. We find that the collapse of stroboscopic section from global distribution to local one and the loss of homogeneity of stroboscopic sections in chaotic attractors for different phases are the key features of this kind of phase synchronization, meanwhile the overall structure of chaotic attractor is not affected apparently by the phase synchronization.
Influence of Width from Landau Damping on the Thermodynamic Potential in Quark-Gluon-Plasma
WANG Xin, LI Jia-Rong
Chin. Phys. Lett. 2000, 17 (5): 335-337 .  
Abstract   PDF(pc) (212KB) ( 380 )
By considering the Debye screening and the finite width of soft gluons, the effective two-loop thermodynamic potential in quark-gluon plasma was evaluated via real-time temperature quantum chromodynamics. The result that depends on damping rate of soft transverse gluons as a physical parameter is obtained, and extension of the case including the longitudinal gluon and fermion will be straightforward.

Identification of Colour Reconnection using Factorial Correlator
FU Jing-Hua, LIU Lian-Shou
Chin. Phys. Lett. 2000, 17 (5): 338-339 .  
Abstract   PDF(pc) (172KB) ( 344 )
A new signal is proposed for the colour reconnection in the hadronic decay of W+ W- in e+e- collisions. Using Pythia Monte Carlo it is shown that factorial correlators for W+ and W- without colour reconnection are almost identical to unity, while those for the cases with colour reconnection fall down approximately linearly in the loglog plot. This signal, being based on the factorial correlator, is more sensitive than the ones using only averaged quantities.

Nuclear Zpif-Type Plots
MA Yu-Gang
Chin. Phys. Lett. 2000, 17 (5): 340-342 .  
Abstract   PDF(pc) (278KB) ( 514 )
Isospin dependent classical molecular dynamics model is used to investigate the nuclear disassembly of 129Xe. Zpif-type plot in the field of linguistics is tested for the rank-classified cluster arrangement from this nuclear disassembly. It is found that the average cluster charge (or mass) of rank n in the charge (or mass) list is exactly inverse to its rank, i.e. there exists Zpif's law at the point of the liquid gas phase transition. This novel criterion can be used to diagnose the nuclear liquid gas phase transition experimentally and theoretically.
Variational Calculation of the Intrashell 2p2 3Pe States for Heliumlike N5+ and O6+ Ions
GUAN Xiao-Xu, WANG Zhi-Wen,
Chin. Phys. Lett. 2000, 17 (5): 343-345 .  
Abstract   PDF(pc) (285KB) ( 369 )
Doubly excited intrashell 2p2 3Pe states in heliumlike N5+ and O6+ions are calculated by using the original Slater-type wave function and the modified configuration interaction wave function. Using the modified Slater-type wave function having up to 393 and 276 terms for N5+ and O6+,we predicted the energy positions of the discrete 2p2 3Pe states for these two heliumlike ions. They are -11.140748676 a.u. and -14.726670741 a.u., respectively. Several expectation values of rin and r12m (-1 ≤ n ≤1, and -1 ≤ m ≤ 2) are also given in the present letter. The present results indicate that the modified Slater-type wave function in which r< and r> coordinates are incorporated is effective and powerful for the description of the 2p2 3Pe state showing strong correlation effect in two-electron systems.

Qualitative Analysis of Low-Lying Resonances of the Dipositronium Emerging from Ps-Ps and Ps-Ps* Collisions
BAO Cheng-Guang, SHI Ting-Yun
Chin. Phys. Lett. 2000, 17 (5): 346-348 .  
Abstract   PDF(pc) (301KB) ( 403 )
An analysis of channel wave functions is made to clarify the types of resonance emerging from the Ps-Ps and Ps-Ps* collisions. The ordering of the energy levels of the states of the dipositronium is evaluated based on the inherent nodal structures of wave functions and on the existing theoretical results. The existence of a few very probable low-lying narrower resonances, namely the 01+(A2), 11-(E) ,..., benefiting from the centrifugal barrier has been suggested.

Analytic Matrix Method for the Study of Propagation Characteristics of a Bent Planar Waveguide
LIU Qing, CAO Zhuang-Qi, SHEN Qi-Shun, DOU Xiao-Ming, CHEN Ying-Li
Chin. Phys. Lett. 2000, 17 (5): 349-351 .  
Abstract   PDF(pc) (174KB) ( 378 )
An analytic matrix method is used to analyze and accurately calculate the propagation constant and bending losses of a bent planar waveguide. This method gives not only a dispersion equation with explicit physical insight, but also accurate complex propagation constants.
Obtaining the Band Structure of a Two-Dimensional Photonic Crystal by an Averaged Field Approach
HE Sai-Ling, QIU Min, Constantin R. Simovski
Chin. Phys. Lett. 2000, 17 (5): 352-354 .  
Abstract   PDF(pc) (197KB) ( 408 )
An averaged field approach is suggested for obtaining the band structure of a photonic crystal when the dimension of the inclusions is much smaller compared with the longest period of the rectangular lattice of the photonic crystal. The method is illustrated for the H-polarization of the 2-dimensional case. The band structure is obtained in an explicit and simple way The method is verified numerically by comparing with the conventional plane-wave expansion method.

Envelope Soliton in Solar Radio Emission
WANG De-Yu, G . P. Chernov
Chin. Phys. Lett. 2000, 17 (5): 355-357 .  
Abstract   PDF(pc) (246KB) ( 494 )
Several envelope soliton fine structures have been observed in solar radio metric-wave emission. We present a model of longitudinal modulational instability to explain these fine structures. It is found that this instability can only occur in the condition of sound velocity being larger than Alfvén velocity in corona. Therefore, the envelope soliton fine structures should display in the coronal region with high temperature and low magnetic field, which corresponds to the solar radio emission in the region of meter and decameter wavelength.
Binding Energy of Ionized-Donor-Bound Excitons in the GaAs-AIxGal-xAs Quant urn Wells
LIU Jian-Jun, ZHANG Shu-Fang, KONG Xiao-Jun, LI Shu-Shen
Chin. Phys. Lett. 2000, 17 (5): 358-359 .  
Abstract   PDF(pc) (196KB) ( 397 )
The binding energy of an exciton bound to an ionized donor impurity (D+, X ) located at the center or the edge in GaAs-AIxGal-xAs quantum wells is calculated variationally for the well width from 10 to 300Å by using a two-parameter wave function, The theoretical results are discussed and compared with the previous experimental results.

In Situ Direct-Current Conductance Investigation of Cu/ C60 Nano-scale Granular Films
LI Xiang, WANG Hai-Qian, HOU Jian-Guo
Chin. Phys. Lett. 2000, 17 (5): 360-362 .  
Abstract   PDF(pc) (270KB) ( 427 )
The in situ direct-current conductance behaviors of Cu/ C60 nano-scale granular films have been investigated experimentally. The results show that the incorporation of Cu into C60 greatly increases the conductance of the film. The orientational phase transition that exists in pure C60 single crystals still retains in the Cu/C60co-evaporated films, while the transition temperature range is significantly widened. The interactions between the nano-scale Cu clusters and C60 grains are discussed.
Interaction Between Two Holes in the CuO2 Plane of Cuprate Superconductors
TIAN Hong-Mei, GONG Chang-De, HAN Fu-Xiang
Chin. Phys. Lett. 2000, 17 (5): 363-364 .  
Abstract   PDF(pc) (170KB) ( 373 )
We have studied the behavior of two holes in the CuO2 plane of cuprate superconductors which is important for making clear the origin of the superconductivity. The interaction between two holes does not show a simple form but a damped oscillating function of the distance between them. It is favorable for them to get closer with a distance about five or ten lattice constant just by thermal motion. Around the equilibrium positions, the vibration motion is considered.
Evidence of Phase Separation in the Hubbard Model
LUAN Bin-Quan, GONG Chang-De
Chin. Phys. Lett. 2000, 17 (5): 365-366 .  
Abstract   PDF(pc) (153KB) ( 399 )
We examine theoretically the possibility o f phase separation due to hole aggregation in the background of anti-ferromagnetically ordered CuO2 planes. The results which are calculated within a self-consistent mean-field-type approximation give obvious evidence of phase separation. Our conclusions agree with previous numerical results (from exact diagonalization).
Transition from Superparamagnetism to Ferromagnetic Single-Domain in a Heisenberg Model for Nano-cluster Magnetic System
SHAO Yuan-Zhi, HE Zhen-Hui
Chin. Phys. Lett. 2000, 17 (5): 367-369 .  
Abstract   PDF(pc) (194KB) ( 543 )
By considering a magnetic system of an ensemble of nanometer clusters without any external magnetic field, the Monte Carlo simulation of the Heisenberg model is used to investigate the transition from a superparamagnetism to a ferromagnetic single-domain state, which is caused by the growth of the clusters. We studied the variation of the dynamic growth exponent P and the transition critical size of the cluster Nc against the reduced temperature t and the uniaxial anisotropy constant A. We found that the growth exponent maximized at a certain temperature, other than being taken as a universal constant as some researchers suggested previously.
Enhanced Transverse Magnetoresistive Effect in Semiconducting Diamond Films
WANG Wan-Lu, LIAO Ke-Jun, WANG Bi-Ben
Chin. Phys. Lett. 2000, 17 (5): 370-372 .  
Abstract   PDF(pc) (248KB) ( 376 )
A very large magnetoresistive effect in both homoepitaxial and heteroepitaxial semiconducting diamond films by chemical vapor deposition has been observed. The changes in the resistance of the films strongly depend on both magnetic field intensity and geometric form of the samples. The effect of disk structure is greater than that of stripe type samples, also variation in the resistance of homoepitaxial diamond films is greater than that of heteroepitaxial diamond films. The resistance of homoepitaxial diamond films with the disk structure is increased by a factor of 2.1 at room temperature under magnetic field intensity of 5 T, but only 0.80 for heteroepitaxial diamond films.
Correlation Between Magnetovolume and Colossal Magnetoresistance Effects in Terbium Doped La-Sr-Mn-O Perovskite
WU Jian, ZHANG Shi-Yuan, YIN Shi-Long, CAO Qing-Qi, GU Kun-Ming, DU You-Wei
Chin. Phys. Lett. 2000, 17 (5): 373-375 .  
Abstract   PDF(pc) (217KB) ( 399 )
(La0.67Tb0.33)2/3Sr1/3MnO3 has been studied in order to probe mechanisms responsible for the giant magnetore-sistance ratios and the lattice effect in this kind of compound. The experiment has shown a strong connection between the magnetotransport and magnetovolume properties. An applied magnetic field not only gives rise to a large negative magnetoresistance (-900%) but also produces two different magnetovolume effects which reflect two different magnetostriction mechanisms in the compound.

Synthesis of Nano-crystalline Diamond Films
ZHANG Fan, ZHANG Yu-Feng, GAO Qiao-Jun, ZHANG Shu-Lin, LIN Ting, PENG Xiao-Fu, LIN Zeng-Dong
Chin. Phys. Lett. 2000, 17 (5): 376-378 .  
Abstract   PDF(pc) (364KB) ( 520 )
We have deposited nano-crystalline diamond films in a routine hot filament chemical vapor deposition system, using CH4/H2 gas mixture. We used various measurements such as field emission scanning electron microscopy, micro-Raman spectroscopy, x-ray photoelectron spectroscopy, and transmission electron microscopy for characterization. The result show that the films consist of a crystalline diamond phase with small grain sizes ranging from 20 to 100nm.
Relationship Between the Shape of Suspension Particle and Ground State Structure of Electrorheological Solid
WU Feng, HE Pei, CHEN Zu-Yao, JIANG Wan-Quan
Chin. Phys. Lett. 2000, 17 (5): 379-381 .  
Abstract   PDF(pc) (184KB) ( 494 )
The effect of the shape of suspension particle in electrorheological (ER) fluid on the ground state structure of ER solid is discussed. The results of computation show that the ground state structure will change with the shape of suspension particle. This phenomenon is a kind of phase transitions that takes the shape factors of suspension particle as tuning parameters. The variation-value of interaction energy of the lattice structure of ER solid with the shape factors of suspension particle is sometimes noticeable.
Two Special Solutions of the Non-ideal Magnetohydrodynamics
FENG Xue-Shang, LIU Yong, WEI Feng-Si, YE Zhan-Yin
Chin. Phys. Lett. 2000, 17 (5): 382-384 .  
Abstract   PDF(pc) (213KB) ( 470 )
A special transformation is found to solve the Magnetohydrodynamic equations, by which two classes of exact analytic time-dependent solutions of magnetic annihilation for incompressible magnetic fluid have been obtained. The solutions derived here possesses scaling property with time t as the scale factor. We find that the current can perform the soliton-like behaviour in the case of asymmetric inflow. The relevant evolution characteristics in the process of magnetic annihilation are also revealed.

Halo Mass of Three-Dimension Milky Way
PENG Fang, PENG Qiu He,
Chin. Phys. Lett. 2000, 17 (5): 385-387 .  
Abstract   PDF(pc) (236KB) ( 528 )
We emphasize the effects of several factors on halo mass for our Galaxy, such as the disk thickness, the local surface density, and the shape of the rotation curve. By fitting the observed rotation curve of our Galaxy with the five-component model, we deduce a halo with a mass of 6.62x1011 MO within 50kpc and a local density of 0.009Mopc-3. It is found that the realistic Galaxy needs only about half of the halo mass that the Galaxy with an infinitesmally thin disk requires.

Protruding Structure Buried in Radio Map by Wavelet
CHEN Pu-chun, , ZHANG Xi-Zhen, XIANG Shou-Ping, FENG Long-Long, W. Reich
Chin. Phys. Lett. 2000, 17 (5): 388-389 .  
Abstract   PDF(pc) (329KB) ( 380 )
An efficient method to identify supernova remnants is provided, in order to iron out the great gap between the predicted number and the observed. We make an attempt to apply D4 wavelet to detect the useful structures buried in radio map, showing that it is an efficient way to separate noises from signals.

28 articles