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Chin. Phys. B  
  Chin. Phys. B--1999, Vol.8, No.4
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GENERAL

SYMMETRIES AND DROMION SOLUTION OF A (2+1)-DIMENSIONAL NONLINEAR SOHR?DINGER EQUATION

Ruan Hang-yu, Chen Yi-xin
Chin. Phys. B 1999, 8 (4): 0241;  doi: 10.1088/1004-423X/8/4/001
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The Painlevé property, infinitely many symmetries and exact solutions of a (2+1)-dimensional nonlinear Schr?dinger equation, which are obtained from the constraints of the Kadomtsev-Petviashvili equation, are studied in this paper. The Painlevé property is proved by the Weiss-Kruskal approach, the infinitely many symmetries are obtained by the formal series symmetry method and the dromion-like solution which is localized exponentially in all directions is obtained by a variable separation method.
CLASSICAL AREAS OF PHENOMENOLOGY

INFLUENCE OF THE DIPOLE-DIPOLE INTERACTION BETWEEN ATOMS ON THE PHASE PROPERTIES OF LIGHT

Tian Yong-hong, Peng Jin-sheng, Xu Da-hai, Han Li-bo
Chin. Phys. B 1999, 8 (4): 0252;  doi: 10.1088/1004-423X/8/4/002
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The time evolution and the statistic characteristic of the light phase in the Tavis-Cummings (T-C) model of two identical two-level atoms coupled to a strong coherent light field are studied by means of the Pegg-Barnett phase theory. It is proved that the dipole-dipole interaction between atoms will lead to the frequency shift of light, the weakening of the degree of atom-field coupling and the restraint of light phase diffusion.

EVOLUTION OF ENTROPY IN THE NONLINEAR JAYNES-CUMMINGS MODEL

Zhang Jing-tao, Chen Zhao-yang, Tong Zhao-yang
Chin. Phys. B 1999, 8 (4): 0261;  doi: 10.1088/1004-423X/8/4/003
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In this paper we study the correlation between the external and the internal state of the trapped atoms by means of the nonlinear Jaynes-Cummings Hamiltonian, in which we pay special attention to the influence of the nonlinearity. We find that the correlation is reflected by the entropy of the vibration mode, which is strongly affected by the nonlinearity. The nonlinearity, embodied by the nonlinear Rabi frequency, exhitits various effects, of which the most important feature is the appearance of the second local minimum value of the entropy in each collapse-revival cycle of the atomic inversion.

LASER-CONTROLLED STATE EXCITATION AND QUANTUM COMPUTATION

Zhang Deng-yu, Zhan Ming-sheng
Chin. Phys. B 1999, 8 (4): 0269;  doi: 10.1088/1004-423X/8/4/004
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Based on the dependence of the molecular excitation probabilities on the laser phases and amplitudes in the model of a three-mode laser interacting with a three-level molecule, we propose a scheme to implement quantum XOR logic gate and to construct quantum error prevention code.

STABILITY OF MULTI-ATOM MICROMASERS

Tan Wei-han, Fan Wei
Chin. Phys. B 1999, 8 (4): 0275;  doi: 10.1088/1004-423X/8/4/005
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In view of the one-atom micromasers output sensitive to the interaction parameters, we propose a new multi-atom micromasers defined by passing multi-atom each time through the cavity regularly. Through analysis and numerical simulation, great progress has been made in the improvement of stability of mean photon number and variance of micromasers.

PERTURBED SPATIAL DARK SOLITONS

Chen Xiang-jun, Zhang Jing-qiao, Wang Yan-zhong
Chin. Phys. B 1999, 8 (4): 0284;  doi: 10.1088/1004-423X/8/4/006
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Effect of perturbations on spatial dark optical solitons is studied analytically with a novel direct perturbation approach for dark solitons. The problems of two-photon absorption and gain with saturation are reconsidered. The corresponding shifts of the soliton centers which have never been obtained by previous theories are given.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

A MOVING SCREW DISLOCATION IN A ONE-DIMENSIONAL HEXAGONAL QUASICRYSTAL

Fan Tian-you, Li Xian-fang, Sun Ying-fei
Chin. Phys. B 1999, 8 (4): 0288;  doi: 10.1088/1004-423X/8/4/007
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This paper extends a moving screw dislocation theory in a conventional crystal to a one-dimensional hexagonal quasicrystal in the framework of the Landau theory. By introducing two functions φ and ψ which satisfy wave equations, respectively, a general solution is suggested in terms of φ and ψ. The analytical expressions for displacement and stress fields induced by a moving screw dislocation as well as the energy are found. The results obtained here when imposing the condition that the phason fields is absent reduce to those for a moving screw dislocation in a crystal.

MOLECULAR DYNAMICS SIMULATION OF ENERGETIC ATOM DEPOSITIONS OF Au/Au(100) FILM

Zhang Qing-yu, Pan Zheng-ying, Tang Jia-yong
Chin. Phys. B 1999, 8 (4): 0296;  doi: 10.1088/1004-423X/8/4/008
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The energetic atom deposition of thin Au/Au(100) film has been studied by molecular dynamics simulation using the Au-Au interatomic interaction potential with embedded atom method. By investigating the variation of coverage curves and Bragg diffraction intensities during the film growth, the transition of Stranski-Kranstanov growth mode to Frank-van der Merwe growth mode was observed with the increase of the incident energy of deposition atoms. The role of energetic atoms in the film growth is discussed by analyzing the transport properties of deposited atoms and the evolution of incident energy and substrate temperatures.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

WEAK FERROMAGNETIC PROPERTIES OF Eu1.85Ca0.15CuO4

Guo Shu-quan, Yao Yu-shu, Xiong Yu-feng, Wu Fei, Dong Cheng
Chin. Phys. B 1999, 8 (4): 0306;  doi: 10.1088/1004-423X/8/4/009
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A weak ferromagnetic transition has been observed for the T'-type compound Eu1.85Ca0.15CuO4. The samples were prepared by a high pressure (5 GPa) synthesis technique. Their transition temperature occurred at 27 K. At 5 K the residual magnetization was 0.033 emu/g, the coercive force was 6.3×104 A/m and the saturation field was larger than 1.6×105 A/m. A field cooling method is proposed as a very convenient way to determine the residual magnetization and coercive force. The compound Eu1.85Ca0.15CuO4 is suggested to use as a sensor to measure the remanant field of SQUID magnetometer.
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