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Volume 16 Issue 1
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Original Articles
Nondynamical r-Matrix Structure of the sl2 Trigonometric Ruijsenaars-Schneider Model
CHEN Kai, HOU Bo-yu, YANG Wen-li, ZHEN yi
Chin. Phys. Lett. 1999, 16 (1): 1-3 .  
Abstract   PDF(pc) (196KB) ( 398 )
It is shown that the sl2 trigonometric Ruijsenaars-Schneider model admits a nondynamical r-matrix structure under a certain gauge. The corresponding r-matrix is the classical limit of a twisted trigonometric R-matrix. The new factorized classical and quantum L-operators are obtained.

Multiple Soliton Solutions of the Dispersive Long-Wave Equations
ZHANG Jie-fang
Chin. Phys. Lett. 1999, 16 (1): 4-5 .  
Abstract   PDF(pc) (110KB) ( 479 )
Using a simple homogeneous balance method, which is very concise and primary, we find the multiple soliton solutions of the dispersive long-wave equations. The method can be generalized to deal with the higher dimensional dispersive long-wave equations and other class of nonlinear equation.

Algebraic Approach to the Study of Quantum Integrability
XU Gong-ou, YANG Ya-tian
Chin. Phys. Lett. 1999, 16 (1): 6-8 .  
Abstract   PDF(pc) (233KB) ( 389 )
The basic problem of quantum integrability has been
systematically studied with an algebraic approach. With the introduction of the dynamical symmetry algebra the difficulty in transferring the classical integrability condition into quantum mechanics is resolved. Using the superconvergent technique of Kolmogorov, it has been proved that systems with Hamiltonians expressed merely with elements of a definite dynamical symmetry algebra form an integrable class of systems corresponding to that dynamical symmetry.

Factorizability of the Two-Component Bose-Einstein Condensate Ground State
HUANG Hu, LI Shi-qun
Chin. Phys. Lett. 1999, 16 (1): 9-11 .  
Abstract   PDF(pc) (220KB) ( 337 )
In this report the two-component Bose-Einstein condensate ground state is shown to be in factorized form following energy minimization argument. The argument can also be applied to excited states. This implies that for stationary states the two components are not entangled. Interaction terms between components are included.

Coherent Resonance of a Strong Electromagnetic Wave Beam to a Standing Gravitational Wave
LI Fang-yu, TANG Meng-xi, WEN De-hua
Chin. Phys. Lett. 1999, 16 (1): 12-14 .  
Abstract   PDF(pc) (247KB) ( 419 )
Coherent resonant conditions of a strong electromagnetic (EM) wave beam propagating in a static magnetic field to a standing gravitational wave (GW) are given. It is found that under the resonant conditions not only first-order perturbed energy fluxes (PEFs) propagating along the same and opposite directions to the background EM wave beam can be generated, but also radial and tangential PEFs which are perpendicular to the above directions can be produced. Such results might provide a new way to display the resonant response induced by the standing GW with h = 10-35 and λg = 0.lm at the level of the single photon avalanche effect.

Detector Calibration by Monte Carlo Simulation Based on the Energy-Range Relationship of Energetic Ions
FANG De-qing, FENG Jun, CAI Xiang-zhou, WANG Jian-song, SHEN Wen-qing, MA Yu-gang, ZHU Yong-tai LI Song-lin, WU He-Yu, GOU Quan-bu, JIN Gen-ming, ZHAN Wen-long, GUO Zhong-yan, XIAO Guo-qing
Chin. Phys. Lett. 1999, 16 (1): 15-17 .  
Abstract   PDF(pc) (210KB) ( 417 )
The experimental measurement of the total interaction cross sections of N, C, B, and Be isotopes on 12C target at medium energies is described. A new formula that gives a good description of the energy-range relationship of energetic ions over a wide energy range is presented. The energy calibration of detectors is made by a Monte Carlo simulation method based on this new formula.
Observation of Decay of 92Rh
ZHOU Shu-hua, LI Zhi-hong, LI Xiao-mei, TIAN Wei, WU Xiao-guang, LI Jing-wen, JIANG Li-yang
Chin. Phys. Lett. 1999, 16 (1): 18-19 .  
Abstract   PDF(pc) (102KB) ( 335 )
By means of beam chopping and γ - γ coincidence technique, the in-beam γ-rays and decay γ-rays of the 15OMeV 40Ca+ 58Ni reaction products have been measured. The four strongest transition γ-rays of 92Rh have been clearly observed. The decay γ-rays of 92Rh have been identified for the first time. The spin and parity of 6+ are tentatively assigned to the ground state of 92Rh. Part of the decay scheme of 92Rh is proposed.
A Novel Two-Dimensional Photonic Crystal
JIN Chong-jun, LI Zhao-lin, ZHANG Dao-zhong, CHENG Bing-ying
Chin. Phys. Lett. 1999, 16 (1): 20-22 .  
Abstract   PDF(pc) (185KB) ( 383 )
A novel two-dimensional photonic crystal that possesses absolute photonic band gaps for both transverse-magnetic and transverse-electric polarized waves is proposed. Plane wave method is used for calculating their photonic band structures. Results show that, for this structure, two absolute photonic band gaps appear in dielectric cylinders periodically imbedded in an air background.
Resonance Fluorescence Spectrum by Two-Level System Without the Rotating Wave Approximation
LIU Ren-hong, TAN Wei-han
Chin. Phys. Lett. 1999, 16 (1): 23-25 .  
Abstract   PDF(pc) (179KB) ( 429 )
In this paper the theory of resonance fluorescence spectrum by two-level system is presented without the assumption of rotating wave approximation. However, in this case, the application of quantum fluctuation-regression theorem to evaluate the resonance fluorescence spectrum takes a more complicated form. The prominent features of the spectrum calculated are the double splitting on the central and side bands and the emergence of harmonics in the asymmetric spectra.
Quantum Theory of the Two-Photon Mazer: General Theory and Emission Probability
ZHANG Zhi-ming, HE Lin-sheng
Chin. Phys. Lett. 1999, 16 (1): 26-28 .  
Abstract   PDF(pc) (203KB) ( 422 )
The idea of the two-photon mazer (microwave amplification via z-motion-induced emission of radiation) is put forward. The dressed states for the interaction of a cascade three-level atom with a quantum cavity field are derived. The general quantum theory of the two-photon mazer is established and its emission probability is studied. The effects of the atomic c.m. momentum and of the atom-field detuning are examined. It is found that the two-photon mazer shows new features that differ from both the one-photon mazer and the conventional two-photon micromaser.
Stationary Photorefractive Self-Pump Phase-Conjugation with Stimulated Backward Scattering in LiNbO3:Fe Crystals
XU Jing-jun, ZHANG Xin-zheng, SUN Qian, ZHANG Guo-quan N. Kamber, LIU Si-min, ZHANG Guang-yin
Chin. Phys. Lett. 1999, 16 (1): 29-31 .  
Abstract   PDF(pc) (268KB) ( 420 )
Stationary photorefractive self-pumped phase-conjugation with one four-wave-mixing interaction region, stimulated by the photorefractive amplified backward scattering, is obtained in LiNbO3:Fe crystals, in which the strong backward scattered light is gotten by putting a scattering particle on the backface of the sample. Even though its reflectivities are not high (its temporal and stationary reflectivities are 10% and 3%, respectively), due to the low electrooptic coefficients of LiNbO3:Fe crystals, our experimental results prove that this mechanism is effective and simple comparing with the “cat ”self-pumped phase-conjugator.

Exact Analytic Solutions for a Finite Width Strip with a Single Edge Crack
FAN Tian-you, YANG Xiao-chun, LI He-xin
Chin. Phys. Lett. 1999, 16 (1): 32-34 .  
Abstract   PDF(pc) (141KB) ( 483 )
The present study develops a conformal mapping technique and deals with the exact analytic solutions in closed form to the finite width strip with single edge crack. Some exact solutions including a universal suitable constant are found, which are very useful in science and engineering.
Effects of Initial Conditions on Energy Distribution of Suprathermal Electrons in Interaction of Intense Ultrashort Laser Pulse with a Preplasma
LIU Shi-bing, ZHANG Jie, YU Wei, ZHANG Guang-cai
Chin. Phys. Lett. 1999, 16 (1): 35-37 .  
Abstract   PDF(pc) (226KB) ( 323 )
Relativistic momentum and energy equations of electrons in an intense laser field are derived with Hamilton-Jacobi equation. For initial electrons in non-equilibrium or Maxwellian equilibrium distributions in preplasmas, suprathermal electron energy distributions are obtained analytically and numerically. The calculation results agree well with the experiments.
Uniaxial Compressive Property of the Lattice of Colossal Magnetoresistance Perovskite Compound Lal-xSrxMnO3
ZHANG Ning, DING Wei-ping, ZHONG Wei
Chin. Phys. Lett. 1999, 16 (1): 38-40 .  
Abstract   PDF(pc) (250KB) ( 428 )
Under a uniaxial pressure of 10-20 MPa, the unusual changes of lattice parameters and remarkable structural distortions in colossal magnetoresistance perovskite Lal-xSrxMnO3 (0.15 ≤ x≤ 0.25) have been observed. The structural distortions were found to be in good agreement with Bridgman equation. These phenomena suggest that the lattice of the manganese perovskite is flexible and the versatility of the electronic and magnetic properties in the perovskites may stems from the lattice flexibility.

Semiconductor-Like Properties of Sputtered FexCul-x Thin Films
GE Hong-liang, SHA Jian, WANG Zhuang-bing, FENG Chun-mu, JIAO Zheng-kuan
Chin. Phys. Lett. 1999, 16 (1): 41-43 .  
Abstract   PDF(pc) (189KB) ( 414 )
Amorphous FexCul-x thin films with x ranging from 0.21 to 0.81 have been obtained by rf-magnetron sputtering. The structure and the electric transport properties of the films can be controlled by both the composition and annealing temperature. The resistances of the films decrease with the temperature increasing from 12 to 300K, which is the typical semiconductor characteristic. After annealing at 400°C for 5h, the amorphous FexCul-x thin film is crystallized and exhibits electric transport property an normal metal film. The dependence of resistance- temperature characteristics of the films on the composition and deposition time is described.
Interfaces in the XY Model and Conformal Invariance
ZHANG De-gang, CHEN Zhong-jun, LI Bo-zang
Chin. Phys. Lett. 1999, 16 (1): 44-46 .  
Abstract   PDF(pc) (206KB) ( 642 )
The one-dimensional XY model with n arbitrarily placed interfaces is investigated. The energy spectrum is shown to have a tower structure only for a commensurate configuration of the critical parameters. The interfacial critical exponents in such cases are determined from conformal invariance theory. The underlying algebra generating the conformal spectrum is the shifted SO(4c) Kac-Moody algebra, the central charge is 2c, which is exactly two times of that in the Ising model with the same structure of interfaces.

Evidence of the Precipitates in the V-Shaped Defects of Undoped GaN
KANG Jun-yong, HUANG Qi-sheng, OGAWA Tomoya
Chin. Phys. Lett. 1999, 16 (1): 47-49 .  
Abstract   PDF(pc) (285KB) ( 414 )
Precipitates in undoped GaN epilayers with specular surfaces grown on sapphire substrates were imaged by super high-resolution electron microscopy (HREM) and analyzed by energy-dispersive x-ray spectrometry (EDXS). The HREM images of the precipitates appeared more or less hexagonal intersection with several ten-nanometer large, which is the same as that of the V-shape defects. The EDXS spectra of the precipitates were mainly composed of the characteristic x-rays of oxygen, carbon, and gallium elements. The results suggest that the precipitates nucleate at the pinholes of the V-shape cavities and grow as the GaN growth.
Investigation of Hole Mobility in GaInP/(In) GaAs/GaAs p-Type Modulation Doped Heterostructures
YANG Quan-kui, LI Ai-zhen, CHEN Jian-xin
Chin. Phys. Lett. 1999, 16 (1): 50-52 .  
Abstract   PDF(pc) (243KB) ( 636 )
Ga0.51In0.49P/(In)GaAs/GaAs heterostructure is regarded as an excellent candidate for two dimensional hole gas system as it has a large valence band offset ratio. In this paper, we report the hole mobility in GaInP/GaAs and GaInP/ In0.20G0.80As/GaAs p-type modulation doped heterostructures grown by gas source molecular beam epitaxy with different p-channels and doping methods. The influences of Be:GaAs cap layer, δ-doping, and strained InGaAs p-channel on hole mobility are discussed, and qualitatively explained by the ionized impurity scattering mechanism. Finally, it was shown that the improvement of hole mobility could be achieved by the δ-doping method combined with strained InGaAs channel.

Ground-State Transitions in Two Vertically Coupled Single Electron Quantum Dots
XIE Wen-fang
Chin. Phys. Lett. 1999, 16 (1): 53-55 .  
Abstract   PDF(pc) (200KB) ( 454 )
Exact results for the two vertically coupled two-dimensional single electron quantum dots are obtained as a function of magnetic field. The ground-state transition is investigated and the effect of the distance between a double-layer dot on the Coulomb interaction is studied. Our results show that when the inter-dot distance increases, a higher magnetic field is needed to induce ground-state transitions and that for sufficiently large distance no transitions occur. Hence, the short-ranged component of Coulomb interaction is important whether the ground-state transition appears in double-layer quantum dots.
A New Interface Anisotropic Potential of Zinc-Blende Semiconductor Interface Induced by Lattice Mismatch
CHEN Yong-hai, WANG Zhan-guo, YANG Zhi-yu
Chin. Phys. Lett. 1999, 16 (1): 56-58 .  
Abstract   PDF(pc) (277KB) ( 537 )
A new interface anisotropic potential, which is proportional to the lattice mismatch of interfaces and has no fitting parameter, has been deduced for (001) zinc-blende semiconductor interfaces. The comparison with other interface models is given for GaAs/AlAs and GaAs/InAs interfaces. The strong influence of the interface anisotropic potential on the inplane optical anisotropy of GaAs/AlGaAs low dimensional structures is demonstrated theoretically within the envelope function approximation.

Large Low-Field Magnetoresistance Observed in Polycrystalline La0.7Ca0.3MnO3 Films
WANG Zhi-hai, LIAN Gui-jun, GAO Ju, ZHOU Ya-qin, KANG Jin-feng, LI Mei-ya, XIONG Guang-cheng
Chin. Phys. Lett. 1999, 16 (1): 59-61 .  
Abstract   PDF(pc) (276KB) ( 827 )
Large low-field magnetoresistance (LFMR) of ∆p/pH = 40% is obtained at 163 K within ±3000 Oe in a polycrystalline La0.7Ca0.3MnO3 (LCMO) films prepared by pulsed laser deposition. The ratio ∆p/pH increases almost linearly with H in the measuring magnetic field range and the peak of LFMR ratios is observed near the resistivity peak temperature, which is different from the observation of spin-polarized intergrain tunnels. This experiment suggests that grain boundaries have large influences on the LFMR. The results indicate that a suitable film process can be used to increase the LFMR of LCMO films.
Magnetoresistance in Magnetic Tunnel Junctions with Nonmagnetic Metallic Spacers and Cap Layers
ZHANG Wu-shou, LI Bo-zang
Chin. Phys. Lett. 1999, 16 (1): 62-64 .  
Abstract   PDF(pc) (262KB) ( 334 )
In a free-electron approximation, transport properties of magnetic tunnel junctions with nonmagnetic metallic spacers and cap layers were studied. The magnetoresistance is oscillatory functions of the thicknesses of non-magnetic metallic spacers and ferromagnets, their period is determined by the Fermi surface properties of the metals, and magnetoresistances (up to about 103%) much greater than those predicted by the Julliere's model are obtained. The results indicate that this structure has potential in designing spin-polarized tunneling devices.
Improvement of Magnetoresistive Character of NiO/NiFeCo/Cu/NiFeCo Exchange-Biased Spin-Valves Through Annealing in Magnetic Field
LU Zhi-hong, LI Tie, QIU Jin-jun, XUN Kun, SHEN Hong-lie, LI Zuo-yi, SHEN De-fang
Chin. Phys. Lett. 1999, 16 (1): 65-67 .  
Abstract   PDF(pc) (220KB) ( 421 )
NiO(70 nm)/NiFeCo(5 nm)/Cu(2 nm)/NiFeCo(5 nm) spin-valve multilayers were prepared by electron beam evaporation. It is found that the magnetoresistive (MR) ratio of the as-deposited films is relatively small (about 1.6% ) and there is no apparent biasing in MR curves of as-deposited multilayers due to weak exchange coupling. Through heat treatment at a proper temperature in a magnetic field, the exchange field of the materials increases and the multilayers show good exchange-biased spin-valve MR character with MR value reaching about 2.5%. The proper temperature range for annealing is 200-250oC. With further increasing temperature, MR ratio drops rapidly.
Lateral Ordered InGaAs Self-organized Quantum Dots Grown on (311) GaAs by Conventional Molecular Beam Epitaxy
XU Huai-zhe, JIANG Wei-hong, XU Bo, ZHOU Wei, WANG Zhan-guo
Chin. Phys. Lett. 1999, 16 (1): 68-70 .  
Abstract   PDF(pc) (355KB) ( 415 )
Self-assembled InxGal-xAs quantum dots (QDs) on (311) and (100) GaAs surfaces have been grown by conventional solid source molecular beam epitaxy. Spontaneously ordering alignment of InxGal-xAs QDs with lower In content around 0.3 has been observed on As-terminated (B type) surfaces. The direction of alignment orientation of the QDs formation differs from the direction of misorientation of the (311) B surface, and is strongly dependent upon the In content x. The ordering alignment becomes significantly deteriorated as the In content is increased to above 0.5 or as the QDs are formed on (100) and (311) Ga-terminated (A type) substrates.

Cubic-BN-Like Structure of B-C-N Films Synthesized by Plasma Source Ion Nitriding
LEI Ming-kai, YUAN Li-jiang, ZHANG Zhong-lin, MA Teng-cai
Chin. Phys. Lett. 1999, 16 (1): 71-73 .  
Abstract   PDF(pc) (211KB) ( 348 )
Plasma source ion nitriding has emerged as a low-temperature, low-pressure nitriding approach for implanting nitrogen ions and then diffusing them into bulk materials. The ion-plating B-C films were nitrided to synthesize B-C-N films at a nitriding temperature from 300 to 500°C. The x-ray photoelectron spectroscopy and diffuse reflectance Fourier transform infrared spectra analyses showed that the amorphous B-C-N films synthesized at 500°C are composed mainly of cubic-BN-like and hexagonal-BN-like plain microdomains. The higher nitriding temperature contributes to the formation of cubic-BN-like B-C-N structure in the B-C-N films.
K Parameter Analysis of the Radio Emission Region of Pulsars
WU Xin-ji, K. N. Yu, ZHANG Cheng-min, WEN Xue-shi
Chin. Phys. Lett. 1999, 16 (1): 74-75 .  
Abstract   PDF(pc) (181KB) ( 291 )
Using a new method of multi-frequency of K parameter, we estimate the ratio of altitudes of radio emission region of pulsars at 430 and 1418 MHz. The value of the ratio is 1.34±0.12 and the power law index of altitude-frequency is 0.24±0.08. It is indicated that the lower radio frequencies originate further out and the emission region is radially narrow.
Quantum Cosmology with a Complex ø6 Field at Finite Temperature
SHEN You-gen, ZHANG Tong-jie, XU Chong-ming
Chin. Phys. Lett. 1999, 16 (1): 76-78 .  
Abstract   PDF(pc) (177KB) ( 376 )
Quantum cosmology with complex ø6 fields at finite temperature for the Vilenkin boundary conditions and Hartle-Hawking boundary conditions has been studied in this paper. The corresponding Wheeler-DeWitt equations and the Universe wave functions are obtained. At the same time, the probability density distribution is calculated and the effect of temperature on probability density distribution is found.
27 articles