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Volume 19 Issue 6
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Original Articles
Searching for (3+1)-Dimensional Painlevé Integrable Model and its Solitary Wave Solution
LI Hua-Mei
Chin. Phys. Lett. 2002, 19 (6): 745-747 .  
Abstract   PDF(pc) (171KB) ( 469 )
A (3+1)-dimensional integrable model constructed by conformal invariants is proved to be integrable. The solitary wave solution of the model is obtained by a simple algebraic transformation relation between the (3+1)-dimensional Harry-Dym equation and the cubic nonlinear Klein-Gordon equation.
Nonlocality Property of Three-Mode Correlated Fields
WANG Ying-Dan, LI Gao-Xiang, ZHAO Zhi, PENG Jin-Sheng
Chin. Phys. Lett. 2002, 19 (6): 748-751 .  
Abstract   PDF(pc) (752KB) ( 361 )
Four three-mode correlated states are generated by two beam splitters. We show that, by means of parity measurement, those light fields exhibit the nonlocality represented by the violation of the Bell inequality. The conditions of the maximum violation are also studied.
Faithful Telecloning with Multiparticle Entanglement
GU Yong-Jian, ZHENG Yi-Zhuang, CHEN Li-Bing, GUO Guang-Can
Chin. Phys. Lett. 2002, 19 (6): 752-754 .  
Abstract   PDF(pc) (207KB) ( 550 )
We study the 1 → N faithful telecloning of two linear-independent states of a one-qubit system. Based on the analysis of the probabilistic cloning machine, we construct a multiparticle entangled state, and present a telecloning scheme under local operations and classical communication (LOCC). The success probability is greater than half of the optimal probability of the probabilistic cloning machine. Specifically, we show how to prepare the three-particle entangled state needed by 1 → 2 telecloning under LOCC using the Greenberger-Horne-Zeilinger state as resource. All the operations in 1 → 2 telecloning are within the reach of current technology.


Mass-Defect Effect in the Hellings-Nordtvedt Field
HUANG Xiu-Ju, WANG Yong-Jiu
Chin. Phys. Lett. 2002, 19 (6): 755-757 .  
Abstract   PDF(pc) (170KB) ( 332 )
In the Hellings-Nordtvedt theory, we obtain some expressions of mass defect effect for a kind of the charged celestial bodies, This is meaningful to calculate the energy radiation in the procession of forming this kind of celestial bodies in astrophysics.
A Stochastic Theory of dc Superconducting Quantum Interference Device Responsitivity in the Presence of Thermal Fluctuations
JIA Ya, SUN Wen-Rong, LI Jia-Rong
Chin. Phys. Lett. 2002, 19 (6): 758-761 .  
Abstract   PDF(pc) (339KB) ( 401 )
A symmetric superconducting quantum interference device (SQUID) with two Josephson junctions in the presence of thermal fluctuations is theoretically studied through two-dimensional Fokker-Planck equations. An analytical formula of SQUID transfer function (or responsitivity) is derived by using the potential condition in the case of the steady state. It is found that the relationship between the optimum bias current Iopt and the thermal fluctuation parameter Γ is Iopt/Γ > 1. The optimal reduced dc SQUID inductance βopt is in the range of 0.80 < βopt <1.25, which is remarkably in agreement with the result of numerical simulation βopt ≈ 1.
Failure of the Ott-Grebogi-York-Type Controllers for Nonhyperbolic Chaos
HUANG De-Bin
Chin. Phys. Lett. 2002, 19 (6): 762-764 .  
Abstract   PDF(pc) (190KB) ( 484 )
It is considered that nonhyperbolicity affects the achievement of the Ott-Grebogi-York-Type (OGY-type) controllers. The result shows that, without a priori analytical knowledge to dynamics, it is impossible to estimate the local dynamics from an experimental time series due to the singularity of the corresponding least-squares problem which results from the nonhyperbolicity in the system, Thus, it is necessary to destroy chaos before obtaining the formation for attempting control by experimental time series. The result just explains a physical experimental result in the failure of chaos control in a parametrically excited pendulum model.
Dromion and Multi-soliton Structures of the (2+1)-Dimensional Higher-Order Broer-Kaup System
LIN Ji
Chin. Phys. Lett. 2002, 19 (6): 765-768 .  
Abstract   PDF(pc) (677KB) ( 690 )
Using the standard truncated Painlevé analysis and the Bäcklund transformation, we can obtain many significant exact soliton solutions of the (2+1)-dimensional high-order Broer-Kaup(BK) system. A special type of soliton solution is described by the variable coefficient heat-conduction-like equation. The inclusion of three arbitrary functions in the general expressions of the solitons makes the solitons of the (2+1)-dimensional high-order Broer-Kaup system possess abundant structures like the solitoff solutions, multi-dromion solutions, ring solitons and so on.
Fractal Solutions of the Nizhnik-Novikov-Veselov Equation
LOU Sen-Yue, TANG Xiao-Yan, CHEN Chun-Li
Chin. Phys. Lett. 2002, 19 (6): 769-771 .  
Abstract   PDF(pc) (843KB) ( 685 )
Considering that some types of fractal solutions may appear in many (2+1)-dimensional soliton equations because some arbitrary functions can be included in the exact solutions, we use some special types of lower dimensional fractal functions to construct higher dimensional fractal solutions of the Nizhnik-Novikov-Veselov equation. The static eagle shape fractal solutions, fractal dromion solutions and the fractal lump solutions are given in detail.
A Possible Origin of Power-Law Distribution in Stock Markets
YANG Chun-Bin, CAI Xu
Chin. Phys. Lett. 2002, 19 (6): 772-774 .  
Abstract   PDF(pc) (209KB) ( 375 )
The origin of the power-law distribution in stock markets is discussed from the view point of self-organized criticality. An analytical expression for the distribution is given from a simple model consideration. We see that power-law increasing or decreasing distribution functions can have the same origin, depending on the values of the parameters.
Hydrogenation Properties of Zr Films Under Various Conditions of Hydrogen Plasma
YAN Guo-Qiang, SHI Li-Qun, ZHOU Zhu-Ying, HAO Guo-Qing, HU Pei-Gang, LUO Shun-Zhong, PENG Shu-Ming, DING Wei, LONG Xing-Gui
Chin. Phys. Lett. 2002, 19 (6): 775-778 .  
Abstract   PDF(pc) (592KB) ( 365 )
The hydrogenation properties of Zr samples with and without an Ni overlayer under various plasma conditions were investigated by means of non-Rutherford backscattering (non-RBS) and elastic recoil detection analysis. The theoretical maximum hydrogen capacity, 66.7at.%, could be achieved at a hydrogen absolute pressure of ~2 Pa and a substrate temperature of ~393 K for a plasma irradiation of only 10 min; this was significantly greater than that for gas hydrogenation under the same hydrogen pressure and substrate temperature. It was also found that the C and O contamination on the sample surface strongly influences the hydrogenation, and that the maximum equilibrium hydrogen content drops dramatically with the increasing total contamination. In addition, the influence of the Ni overlayer on the plasma hydrogenation is discussed.
Empirical Example of Nucleus with Transitional Dynamical Symmetry X(5)
ZHANG Da-Li, ZHAO Hui-Ying
Chin. Phys. Lett. 2002, 19 (6): 779-781 .  
Abstract   PDF(pc) (303KB) ( 456 )
By analysing the energy spectrum, E2 transition rates and branching ratios, it is shown explicitly that the nucleus 150Nd provides an empirical example with X(5) symmetry at the critical point of the transition from U(5) to SU(3) symmetry.

Magnetic Surface Microtraps for Two-Species Bose-Einstein Condensations
HU Jian-Jun, YIN Jian-Ping,
Chin. Phys. Lett. 2002, 19 (6): 782-785 .  
Abstract   PDF(pc) (556KB) ( 291 )
We propose a novel magnetic surface microtraps (i.e., a double Z-wire trap) for the study of two-species Bose-Einstein condensations. The spatial distributions of the magnetic fields from the double Z-wire configurations and their gradients and curvatures are calculated and analysed. The result shows that the proposed surface trap has double magnetic wells and can be continuously changed into a single-well trap by reducing the current in a straight wire, and the maximum field gradient greater than 5 x 104G/cm and the maximum field curvature (at each trap center) greater than 2.5 x 107G/cm2 can be generated in our double-well traps, which can be used to realize two-species Bose-Einstein condensations and to study the properties of double-well Bose-Einstein condensations and so on.
Optical Pulse Generation with Different Repetition Rates in a Dual-Wavelength Actively Mode-Locked Fiber Ring Laser
YANG Shi-Quan, ZHAO Chun-Liu, LI Zhao-Hui, YUAN Shu-Zhong, DONG Xiao-Yi
Chin. Phys. Lett. 2002, 19 (6): 786-787 .  
Abstract   PDF(pc) (326KB) ( 529 )
We propose a simple configuration for dual-wavelength operation in an actively mode-locked fiber ring laser with fiber Bragg gratings. We experimentlly demonstrate simultaneously mode-locked operation with two wavelengths at different repetition rates: one is harmonically mode-locked and the other is rational harmonically mode-locked.
Importance of Marangoni Convection in Laser Full-Penetration Welding
YE Xiao-Hu, CHEN Xi
Chin. Phys. Lett. 2002, 19 (6): 788-790 .  
Abstract   PDF(pc) (458KB) ( 341 )
We study the effects of welding speed, Marangoni convection and natural convection on heat transfer and melt flow in a laser full-penetration welding using a three-dimensional modeling approach. The computed results demonstrate the importance of considering Marangoni convection. The predicted weld pool profile is favorably compared with experimental observation.
Influence of Light Polarization States on Sum-Frequency Generation in a Chiral Medium with a Two-Coupled-Oscillator Model
ZHENG Yang-Dong, LI Jun-Qing, LI Chun-Fei
Chin. Phys. Lett. 2002, 19 (6): 791-794 .  
Abstract   PDF(pc) (562KB) ( 422 )
Sum-frequency generation (SFG) is investigated using the
two-coupled-oscillator molecular model. The influence of the polarization states and angles of two incident beams on reflected and transmitted sum-frequency lights is discussed by considering the circular birefringence in a chiral medium. The different response of media with two kinds of enantiomers to polarization states of incident beams is also discussed. Furthermore, the relations between the SFG spectrum and the polarization states are studied. The theoretical result is consistent with a known experimental fact.
A PVK-Based High-Performance Photorefractive Polymer Composite Under a Low External Electric Field
ZHENG Rui-Zhi, ZHAO You-Yuan, MIN Ke, WANG Chang-Chun, LI Fu-Ming
Chin. Phys. Lett. 2002, 19 (6): 795-797 .  
Abstract   PDF(pc) (298KB) ( 368 )
We describe a PVK-based photorefractive polymer composite doped with disperse red 1, poly-butylacrylate and TNF. By the two-beam coupling experiment, We investigate its photorefractive properties as well as the dynamic process of the index gratings in the sample. We observe the photorefractive effect in the absence of an applied external electric field. The two-beam coupling gain coefficient was measured to reach as higher as 140 cm-1 in the absence of an external applied electric field and a value of 470cm-1 at a poling dc electric field of 25V/μm.
Low Threshold Bistable Switching by the Nonlinear One-Dimensional Photonic Crystal
CHEN Li-Xue, DENG Xiao-Xu, DING Wei-Qiang, ZHANG Yu, LIU Shu-Tian
Chin. Phys. Lett. 2002, 19 (6): 798-800 .  
Abstract   PDF(pc) (300KB) ( 358 )
In the approximation of fast Debye relaxation of nonlinear Kerr medium, the nonlinear finite-difference time-domain method is derived to simulate numerically the one-dimensional nonlinear photonic crystal sandwiched by Kerr medium. Bistable switching with low threshold intensity of 0.01kW/cm2 is obtained, and the corresponding refractive index change of Kerr media is about 0.038.
Violet to Infrared Multiwavelength Generation in Periodically Poled Lithium Niobate Pumped by a Q-Switched Nd:YVO4 Laser
XU Zu-Yan, LIANG Xiao-Yan, LI Jian, YAO Ai-Yun, LIN Xue-Chun, CUI Da-Fu, WU Ling-An
Chin. Phys. Lett. 2002, 19 (6): 801-803 .  
Abstract   PDF(pc) (364KB) ( 477 )
Six output wavelengths from violet to infrared have been observed simultaneously from an all-solid-state laser pumped optical parametric oscillator in a periodically poled lithium niobate crystal. The output wavelengths can be tuned by varying the quasi-phase matched period and/or temperature. The pump laser is a diode-pumped passive Q-switched Nd:YVO4 laser operated at 1064 nm. Using a crystal with a 29.9μm grating period, we measured six wavelengths at 448, 515, 532, 630, 773 and 1546 nm and obtained efficient output. We explain the multiwavelength generation by multiwave coupling theory. This phenomenon may have novel applications in photonic devices.
Metallic Photonic Bandgap Resonant Antennas with High Directivity and High Radiation Resistance
LIN Qing-Chun, FU Jian, HE Sai-Ling, ZHANG Jian-Wu
Chin. Phys. Lett. 2002, 19 (6): 804-806 .  
Abstract   PDF(pc) (695KB) ( 453 )
A metallic photonic bandgap (MPBG) resonant antenna is introduced, which has novel characteristics (such as high directivity and high radiation resistance for certain range of frequencies) as compared to conventional MPBG antennas. The linear MPBG resonant antenna is formed by infinitely long metallic rods in vacuum. The numerical results for the radiation pattern and the radiation resistance are presented. By adjusting the structure of the MPBG resonant antenna and its working frequency, an optimal structure is achieved. The physical reasons for the novel characteristics of the MPBG resonant antenna are also explained.
Filter Performance of a Cesium Faraday Optical Filter at 852 nm
ZHANG Yun-Dong, JIA Xiao-Ling, BI Yong, MA Zu-Guang, WANG Qi
Chin. Phys. Lett. 2002, 19 (6): 807-809 .  
Abstract   PDF(pc) (358KB) ( 462 )
We have investigated a cesium Faraday filter at 852nm in relatively weak and strong magnetic field, theoretically and experimentally. With a cesium cell of 0.02m length in an axial magnetic field of 0.06T, the line-center operation has been achieved. The calculated peak transmission reached 99% with a full width at half maximum (FWHM) bandwidth of only 3.9 GHz, the measured FWHM bandwidth of the filter is 3.29 GHz, which is in general agreement with the theoretical result.
Parameter Optimization of a 9 x 9 Polymer Arrayed Waveguide Grating Multiplexer
GUO Wen-Bin, MA Chun-Sheng, CHEN Wei-You, ZHANG Da-Ming, CHEN Cai-Xin, CUI Zhan-Chen, ZHAO Yu, LIU Shi-Yong
Chin. Phys. Lett. 2002, 19 (6): 810-813 .  
Abstract   PDF(pc) (515KB) ( 330 )
Some important parameters are optimized for a 9 x 9 polymer arrayed waveguide grating multiplexer around the central wavelength of 1.55μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, diffraction order, pitch of adjacent waveguides, path length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range, the number of input/output channels and that of arrayed waveguides. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 9 input and 9 output channels, and 91 arrayed waveguides.
Lattice Boltzmann Numerical Simulation of a Circular Cylinder
FENG Shi-De, ZHAO Ying, GAO Xian-Lin, JI Zhong-Zhen
Chin. Phys. Lett. 2002, 19 (6): 814-817 .  
Abstract   PDF(pc) (613KB) ( 367 )
The lattice Boltzmann equation (LBE) model based on the Boltzmann equation is suitable for the numerical simulation of various flow fields. The fluid dynamics equation can be recovered from the LBE model. However, compared to the Navier-Stokes transport equation, the fluid dynamics equation derived from the LBE model is somewhat different in the viscosity transport term, which contains not only Navier-Stokes transport equation but also nonsteady pressure and momentum flux terms. The two nonsteady terms can produce the same function as the random stirring force term introduced in the direct numerical or large-eddy vortex simulation of turbulence. Through computation of a circular cylinder, it is verified that the influence of the two nonsteady terms on flow field stability can not be ignored, which is helpful for the study of turbulence.
Theoretical Study of the Opacity for Mixture Materials at High Temperatures
YAN Jun, WU Ze-Qing, PANG Jin-Qiao, QIU Yu-Bo
Chin. Phys. Lett. 2002, 19 (6): 818-821 .  
Abstract   PDF(pc) (317KB) ( 418 )
Using a detailed configuration accounting model with term structures treated by the unresolved transition array model, we have extensively investigated the opacities of mixture materials. For plasmas at the temperature of 250 eV and density of 1 g/cm3, our calculated Rosseland mean opacities are in good agreement with other theoretical results, a high increase in the Rosseland mean opacity to 2944 cm2/g is achieved for a multi-element mixture compared to the value 1729 cm2/g for pure gold. Various mixtures at other plasma conditions are also studied.
Jump Conditions of a Non-Neutral Plasma Shock with Current and Potential Difference
HU Xi-Wei
Chin. Phys. Lett. 2002, 19 (6): 822-824 .  
Abstract   PDF(pc) (185KB) ( 330 )
Jump conditions about the total momentum flux and energy flux in a non-neutral plasma shock with electric current and field are given, which are derived from the double fluid equations and the Poisson equation for electron and ion fluids. Furthermore, We derive the relations between the upstream and downstream velocities and temperatures, and the minimum upstream Mach number for the plasma shock existence Mmin1, which depend on the current through the shock front J0, the electric potential difference between the upstream and downstream of shock ΔФ, and the ion charge Z.
Fractal Pattern Growth in Ti-Implanted Steel with High Ion Flux
ZHANG Tong-He, WU Yu-Guang, LIU An-Dong
Chin. Phys. Lett. 2002, 19 (6): 825-827 .  
Abstract   PDF(pc) (1427KB) ( 444 )
We report on the formation of metal nanometer phase and fractal patterns in steel using metal vapor vacuum arc source ion implantation with high ion flux. The dense nanometer phases are cylindrical and well dispersed in the Ti-implanted layer with an ion flux up to 50μA/cm2. The collision fractal pattern is formed in Ti-implanted steel with ion flux of 25μA/cm2 and the disconnected fractal pattern is observed with ion flux of 50μA/cm2. The average density of nanometer phases decreases from 1.2 x 1011/cm2 to 6.5 x 1010/cm2 as the ion flux increases from 25μA/cm2 to 50μA/cm2. Fractal pattern growth is in remarkable agreement with Sander's diffusion-limited aggregation model. The alloy clusters have diffused and aggregated in chains forming branches to grow a beautiful tree during Ti implantation with ion flux raging from 75μA/cm2 to 85μA/cm2. The model of fractal pattern growth during ion implantation with high ion flux is discussed.
Insitu Plane-View and Cross-Section Transmission Electron Microscopy of Fractal Formation in Au/a-Ge Bilayer Films
ZHANG Shu-Yuan, PAN Deng-Yu, WU Zi-Qin
Chin. Phys. Lett. 2002, 19 (6): 828-831 .  
Abstract   PDF(pc) (1773KB) ( 445 )
Fractal crystallization in Au/a-Ge bilayer films was studied by in-situ plane-view and cross-section transmission electron microscopy. The experimental evidences suggest that the fractal crystallization is controlled by both diffusion and reaction processes. The growth kinetics analysis indicates that both diffusion-limited aggregation and random successive nucleation mechanisms play an important role in fractal crystallization in Au/a-Ge bilayer films.
Influence of Combination of Casimir Force and Residual Stress on the Behaviour of Micro- and Nano-Electromechanical Systems
ZHENG Mao-Sheng, ZHOU Gen-Shu, ZHAO Wen-Zhen, GU Hai-Cheng
Chin. Phys. Lett. 2002, 19 (6): 832-834 .  
Abstract   PDF(pc) (237KB) ( 352 )
Casimir force and residual stresses actually appear in over-layers or films simultaneously, the study of the behaviour of micro-/nano-electromechanical systems in the presence of Casimir force and residual stress is of significance to the design of the relevant devices. We derive analytical expressions of the deflection of a bridge shaped device under the mutual actions of Casimir force and residual stress in films. It is shown that the tensile residual stress enhances wavy behaviour of the deflection, while the compressive residual stress increases the deflection value and reduces the wavy behaviour.
Molecular Dynamics of Structural Organization in Binary Fluids with Fixed Particles
TANG Yan-Li, MA Yu-Qiang
Chin. Phys. Lett. 2002, 19 (6): 835-838 .  
Abstract   PDF(pc) (1225KB) ( 466 )
We have numerically studied the structural organization in binary immiscible fluids with fixed particles. The particles that have a finite excluded volume and a selective affinity for one fluid component have the significant influence on the organization process, where the hydrodynamic flows induced by the interface motion are suppressed and the domain growth is slowed down at late stages. Two different cases with weak and strong preferential interactions are considered, and the results show that the particles in the former can be left in the unfavorable phase during the process but are permanently surrounded by the favorable phase in the latter. The study indicates that the system would develop into a dynamical steady state and the final domain size might be dependent not only on the number of particles but also on the preferential interaction strength.
Preparation and Photoemission Spectra of Rb3C60 Single Crystal Thin Film
LI Hong-Nian, WU Tai-Quan, CHEN Xiao, LI Hai-Yang, BAO Shi-Ning, XU Ya-Bo, QIAN Hai-Jie, Ibrahim KURASH, LIU Feng-Qin
Chin. Phys. Lett. 2002, 19 (6): 839-842 .  
Abstract   PDF(pc) (350KB) ( 416 )
Rb3C60 single-crystal thin films were prepared on the cleaved (111) surface of C60 single crystal. The photoemission spectrum line shapes of the lowest unoccupited molecular orbital (LUMO) derived band at room temperature and 150 K were established by the synchrotron radiation photoemission spectrum measurements. The density of states near the Fermi level was distinctly affected by temperature. No less than six sub-peaks of the LUMO band were observed even at room temperature. The existence of so many sub-peaks offered the opportunities to analyses in more detail the orientational structure and the electron-Boson interactions of the narrow-band metallic Rb3C60.
In-Plane Propagation of Cavity Polaritons in Quantum Semiconductor Microcavity
LIU Wen-Kai, LIN Shi-Ming, ZHANG Cun-Shan
Chin. Phys. Lett. 2002, 19 (6): 843-845 .  
Abstract   PDF(pc) (250KB) ( 340 )
Considering that the coupling among the heavy-hole exciton, light-hole exciton and the cavity photon can form bipolaritons in a quantum semiconductor microcavity, we calculate the group velocities of the cavity polaritons at different incident angle s using the coupling model of three harmonic oscillators. The result indicates that the group velocities of the low and middle branches of the cavity polaritons have extrema, but the group velocities of the high branch increase with the increasing incident angle.
Effects of Electric Field on the Valence-Bond Property of an Electron in a Quantum-Dot Molecule
WANG Li-Min, LUO Ying, MA Ben-Kun
Chin. Phys. Lett. 2002, 19 (6): 846-849 .  
Abstract   PDF(pc) (357KB) ( 378 )
The electronic structure of the quantum-dot molecules in an electric field is investigated by the finite element method with the effective mass approximation. The numerical calculation results show that the valence bond of the quantum-dot molecule alternates between covalent bonds and ionic bonds as the electric field increases. The valence-bond property can be reflected by the oscillator strength of the intraband transition. The bound state with the highest energy level in the quantum-dot molecule gradually changes into a quasibound state when the electric field increases.
Barriers Formation on YBa2Cu3Oy Thin Film Using CF4 Plasma Fluorination
Abbas A. Essa, KANG Lin, XU Wei-Wei, YANG Sen-Zu, WU Pei-Heng
Chin. Phys. Lett. 2002, 19 (6): 850-853 .  
Abstract   PDF(pc) (594KB) ( 378 )
We investigate the surface structure and composition of
YBa2Cu3Oy (YBCO) thin film modified by CF4 plasma fluorination. In addition to the absorption of hydrocarbons, chemical reactions of the YBCO surface take place during CF4 plasma treatment. Various x-ray photoelectron spectroscopic data are reported and discussed, and the existence of a thin barrier is confirmed, which homogeneously covers the edge of the base YBCO film in our interface engineering Josephson junction. Measurements of Auger electron spectroscopic data and the resistance versus temperature indicate that the barrier is a controllable-insulating layer.
Modification of YBa2Cu3O27-δ Thin Film Using Atomic Force Microscope
YOU Li-Xing, YIN Xiao-Bo, FENG Yi-Jun, YANG Sen-Zu, KANG Lin, WANG Mu, WU Pei-Heng
Chin. Phys. Lett. 2002, 19 (6): 854-856 .  
Abstract   PDF(pc) (1142KB) ( 371 )
A YBa2Cu3O27-δ thin film is modified by a probe electric field of an atomic force microscope to form a ridge with the width of only a grain cell. The modification varies with operation parameters of the bias voltage, the moving velocity of probe and the ambient humidity. Energy dispersive spectroscopy analysis shows only oxygen deficient in the modified YBCO thin film. As a result, the suppressed superconductivity was found in the junction crossed the ridge.
Giant Magnetoresistance Effect of the Nanoscale Layered-Perovskite La2.5-xK0.5+xMn2O7 (0 < x < 0.5)
ZHONG Wei, ZHANG Ning, LIU Xian-Song, ZHAO Li-Juan, ZHANG Jian-Rong, DU You-Wei
Chin. Phys. Lett. 2002, 19 (6): 857-860 .  
Abstract   PDF(pc) (540KB) ( 381 )
Nanoscale layered-perovskite La2.5-xK0.5+xMn2O7 (0 < x < 0.5) have been prepared by the modified sol-gel method, and their structures, magnetic and electric properties have been studied. The experimental results show that these materials exhibit paramagnetic-to-ferromagnetic phase transitions at 183, 216, 230, 238, and 249 K for x = 0.05, 0.15, 0.25, 0.35, and 0.45, respectively. For all compositions of La2.5-xK0.5+xMn2O7 investigated here, we have not observed the metal-nonmetal transition phenomena for the whole temperature region (80 - 300 K). The nanoscale samples exhibit highly enhanced magnetoresistance (MR) effects especially at low temperatures (< TC). The MR behaviour can be explained by taking account of the two-dimensionality with anisotropy of the Mn-O networks and nanoscale grain size effect in the layered manganese perovskites.
Raman Spectra of the Calix[n]arene-C60 Complex
CHENG Guang-Xu, GU Gang, ZHANG Wei, ZANG Wen-Cheng, DU You-Wei, WU Yong, XU Zheng, CHENG Jia, CHU Hao-Yu
Chin. Phys. Lett. 2002, 19 (6): 861-863 .  
Abstract   PDF(pc) (420KB) ( 491 )
We have obtained the Raman spectra of the calix[n]arene C60 complex of anti-conformation. Very different interactions between C60 and calix[n]arene (n = 4,8) have been found from the vibratory spectroscopy, which are more complicated than that reported in previous works. It is of interest to find three low frequency modes, i.e., the spheroidal, torsional and E2 clearly shown at 39, 130 and 208 cm-1, respectively. It is primarily interpreted as relaxation effect of calix[8]arene framework for C60 where the intramolecular bridge between C60 and calix[8]arene are partly packed and two axes of C60 ([100] and [101]) are changed from the original configuration. The change of vibratory environment of carbon atom of C60 made some new modes create. The Hg5 mode (at 1101cm-1) and Hg2 (at 431cm-1) have been split and some modes (the Ag2 and other six Hg modes) were hidden.
Temperature Effect on Single Bubble Sonoluminescence
LU Mei-Jun, CHEN Wei-Zhong, SHEN Jian-Hua, WANG Wen-Jie, LI Sheng-Qiong
Chin. Phys. Lett. 2002, 19 (6): 864-866 .  
Abstract   PDF(pc) (360KB) ( 347 )
Experiments of the temperature effect on single bubble sonoluminescence (SBSL) are performed with a mixture of water and anti-freezer. Since experiments of constant pressure (keep sound pressure constant) are not feasible for a wide temperature range, experiments of constant-luminance (keep light intensity stable), which reflect pure sensitivity of SBSL to temperature, are investigated. The results show that lower temperature needs less pressure to obtain the same light intensity, which means that lower temperature is better for SBSL. Numerical calculations show a qualitative agreement with experiments.
Influence of Ambient Atmosphere on the Plasmon Resonance Absorption of Ag/SiOx (0 ≤ x ≤ 2) Nanocomposite Film
YANG Lin, LIU Yu-Liang, WANG Qi-Ming, LI Guang-Hai, ZHANG Li-De
Chin. Phys. Lett. 2002, 19 (6): 867-870 .  
Abstract   PDF(pc) (380KB) ( 436 )
Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si-containing matrices were prepared by the radio frequency magnetron co-sputtering deposition. We studied the influence of ambient atmosphere during the preparation and heat-treatment of Ag/SiOx (0 ≤ x ≤ 2) nanocomposite film on its optical absorption properties. We found that the plasmon resonance absorption peak shifts to shorter wavelengths with theincreasing oxygen content in the SiOx matrix. The analysis indicates that the potential barrier between Ag nanoparticles and SiOx matrix increases with the increasing x value, which will induce the surface resonance state to shift to higher energy. The electrons in the vicinity of the Fermi level of Ag nanoparticles must absorb more energy to be transferred to the surface resonance state with the increasing x value. It was also found that the plasmon resonance absorption peaks of the samples annealed in different ambient atmospheres are located at about the same position. This is because the oxidation surface layer is dense enough to prevent the oxygen from penetrating into the sample to oxidize the silicon in the inner layer.
Self-Organization of CdS Nanoparticles in Polystyrene Film
LIANG Hai-Chun, XIANG Hong, RONG Min-Zhi, ZHANG Ming-Qiu, ZENG Han-Min, WANG Shu-Feng, GONG Qi-Huang
Chin. Phys. Lett. 2002, 19 (6): 871-874 .  
Abstract   PDF(pc) (498KB) ( 544 )
Self-organization of nano-CdS particles in polystyrene can be observed by encapsulating the particles with n-dodecyl mercaptan owing to a strong electron transfer interaction between the modified CdS nanoparticles and aliphatic carbons in polystyrene. Consequently, ultraviolet/visible absorption edge of the treated nano-CdS/polystyrene composites is further blue-shifted in addition to the shift caused by quantum size effect, and the fluorescence emission peak of the composite becomes red-shifted and narrow.
Effect of N2 Plasma Annealing on Properties of Fluorine Doped Silicon Dioxide Films with Low Dielectric Constant for Ultra-Large-Scale Integrated Circuits
ZHANG Wei, WANG Peng-Fei, DING Shi-Jin, WANG Ji-Tao, LEE William Wei
Chin. Phys. Lett. 2002, 19 (6): 875-877 .  
Abstract   PDF(pc) (321KB) ( 411 )
The influence of N2 plasma annealing on the properties of fluorine doped silicon oxide (SiOF) films is investigated. The stability of dielectric constant of SiOF film is remarkably improved by the N2 plasma annealing. After enduring moisture absorption test for six hours in a chamber with 60% humidity at 50°C, the dielectric constant variation of the annealed SiOF films is only 1.5%, while the variation for those SiOF films without annealing is 15.5%. Fourier transform infrared spectroscopic results show that the absorption peaks of Si-OH and H-OH of SiOF films are reduced after the N2 plasma annealing because the annealing can wipe off some unstable Si-F2 bonds in SiOF films. These unstable Si-F2 bonds are suitable to react with water, resulting in the degradation of SiOF film properties. Therefore, the N2 plasma annealing meliorates the properties of SiOF films with low dielectric constant.
Moist Potential Vorticity Anomaly with Heat and Mass Forcings in Torrential Rain Systems
GAO Shou-Ting, LEI Ting, ZHOU Yu-Shu
Chin. Phys. Lett. 2002, 19 (6): 878-880 .  
Abstract   PDF(pc) (173KB) ( 502 )
The moist potential vorticity (MPV) equation is derived from complete atmospheric dynamic equations with both heat and mass forcings, with which the impermeability theorem of the“MPV substance”is proved. It is clarified that both heat and mass forcings induced by the intensive precipitation in torrential rain systems can lead to the MPV anomaly. The MPV substance anomaly is a dynamical tracer for tracking a torrential rain system.
Special Effect of Parallel Inductive Electric Field
CHEN Tao, LIU Zhenxing, W. Heikkila
Chin. Phys. Lett. 2002, 19 (6): 881-884 .  
Abstract   PDF(pc) (802KB) ( 268 )
Acceleration of electron by a field-aligned electric field during a magnetospheric substorm in the deep geomagnetic tail is studied by means of a one-dimensional electromagnetic particle code. It was found that the free acceleration of the electrons by parallel electric field is obvious, kinetic energy variation is greater than electromagnetic energy variation in the presence of parallel electric field. Magnetic energy is greater than kinetic energy variation and electric energy variation in the absence of parallel electric field. More wave modes in the presence of the parallel electric field are generated than those in the absence of the parallel electric field.
41 articles