Table of contents

15 April 1999, Volume 8 Issue 4 Previous issue    Next issue

GENERAL

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SYMMETRIES AND DROMION SOLUTION OF A (2+1)-DIMENSIONAL NONLINEAR SOHR?DINGER EQUATION Ruan Hang-yu (阮航宇), Chen Yi-xin (陈一新) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  241-251.  DOI: 10.1088/1004-423X/8/4/001 Abstract ( 1182 )   PDF (236KB) ( 367 )   The Painlevé property, infinitely many symmetries and exact solutions of a (2+1)-dimensional nonlinear Schr$\ddot{o}$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

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INFLUENCE OF THE DIPOLE-DIPOLE INTERACTION BETWEEN ATOMS ON THE PHASE PROPERTIES OF LIGHT Tian Yong-hong (田永红), Peng Jin-sheng (彭金生), Xu Da-hai (徐大海), Han Li-bo (韩立波) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  252-260.  DOI: 10.1088/1004-423X/8/4/002 Abstract ( 1264 )   PDF (239KB) ( 712 )   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.

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EVOLUTION OF ENTROPY IN THE NONLINEAR JAYNES-CUMMINGS MODEL Zhang Jing-tao (张敬涛), Chen Zhao-yang (陈朝阳), Tong Zhao-yang (童朝阳) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  261-268.  DOI: 10.1088/1004-423X/8/4/003 Abstract ( 1233 )   PDF (280KB) ( 452 )   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.

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LASER-CONTROLLED STATE EXCITATION AND QUANTUM COMPUTATION Zhang Deng-yu (张登玉), Zhan Ming-sheng (詹明生) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  269-274.  DOI: 10.1088/1004-423X/8/4/004 Abstract ( 1404 )   PDF (205KB) ( 465 )   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.

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STABILITY OF MULTI-ATOM MICROMASERS Tan Wei-han (谭维翰), Fan Wei (范薇) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  275-283.  DOI: 10.1088/1004-423X/8/4/005 Abstract ( 914 )   PDF (227KB) ( 339 )   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.

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PERTURBED SPATIAL DARK SOLITONS Chen Xiang-jun (陈向军), Zhang Jing-qiao (张京桥), Wang Yan-zhong (王彦中) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  284-287.  DOI: 10.1088/1004-423X/8/4/006 Abstract ( 934 )   PDF (169KB) ( 384 )   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

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A MOVING SCREW DISLOCATION IN A ONE-DIMENSIONAL HEXAGONAL QUASICRYSTAL Fan Tian-you (范天佑), Li Xian-fang (李显方), Sun Ying-fei (孙应飞) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  288-295.  DOI: 10.1088/1004-423X/8/4/007 Abstract ( 1285 )   PDF (206KB) ( 751 )   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 $\varphi$ and $\psi$ which satisfy wave equations, respectively, a general solution is suggested in terms of $\varphi$ and $\psi$. 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.

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MOLECULAR DYNAMICS SIMULATION OF ENERGETIC ATOM DEPOSITIONS OF Au/Au(100) FILM Zhang Qing-yu (张庆瑜), Pan Zheng-ying (潘正瑛), Tang Jia-yong (汤家镛) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  296-305.  DOI: 10.1088/1004-423X/8/4/008 Abstract ( 1107 )   PDF (265KB) ( 462 )   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

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WEAK FERROMAGNETIC PROPERTIES OF Eu1.85Ca0.15CuO4 Guo Shu-quan (郭树权), Yao Yu-shu (姚玉书), Xiong Yu-feng (熊玉峰), Wu Fei (吴非), Dong Cheng (董成) Acta Physica Sinica (Overseas Edition), 1999, 8 (4):  306-308.  DOI: 10.1088/1004-423X/8/4/009 Abstract ( 1170 )   PDF (164KB) ( 384 )   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.