Jun 2007, Volume 2 Issue 2

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  • Yanhua Shih
    One of the most surprising consequences of quantum mechanics is the entanglement of two or more distant particles. In an entangled EPR two-particle system, the value of the momentum (position) for neither single subsystem is determined. However, if one of the subsystems is measured to have a certain momentum (position), the other subsystem is determined to have a unique corresponding value, despite the distance between them. This peculiar behavior of an entangled quantum system has surprisingly been observed experimentally in two-photon temporal and spatial correlation measurements, such as ghost  interference and ghost  imaging. This article addresses the fundamental concerns behind these experimental observations and to explore the nonclassical nature of two-photon superposition by emphasizing the physics of 2"`1 + 1.
  • LIN Qiang, CAI Yang-jian, WANG Li-gang
    The recent progresses on the propagation, generation and application of partially coherent beam (PCB) are reviewed in this paper. A new tensor ABCD law for treating the propagation of partially coherent Gaussian-Schell model (GSM) beams through a paraxial optical system is derived. The focusing, spectral shift and fractional Fourier transform of the GSM beam are investigated by using the tensor method. The generation of PCB with special optical resonator is studied both theoretically and experimentally. Furthermore, the ghost imaging and superluminal propagation of the PCB is discussed. The results show clearly that the coherence of light have strong influences on the ghost imaging and superluminal propagation.
  • ZHANG Le-xin, ZHANG Ran, LI Zhi-quan
    In this paper, we set up a sensing model of PSMs (porous silicon microcavities) by applying the Bruggeman effective medium approximation theory and the transfer matrix method. In addition, we explain in detail the adsorption characteristics of porous silicon. Finally, using an experimental setup to measure the reflectivity spectrum of PSMs when the sensor is exposed to different organic vapors, the experimental results prove that it is a feasible optical sensor for the detection of organic species. Resolution of the PSMs sensor is high, response time and resume time is short and repetition is good.
  • LIU Hui-jun
    We review our density functional study of oxygen adsorption on the outer surface of 4 Å single-wall carbon nanotubes, which have been recently synthesized using a templating method. The stability of these 4 Å tubes under ambient conditions is investigated by the nudged elastic band technique and further confirmed by the experimentally measured Raman spectra. Different adsorption pictures of singlet O2 could be used to select a single chirality from a mixture of these ultra-small radius tubes.
  • XIE Bai-song, DU Shu-cheng
    Single or/and multipeak solitons in plasma under relativistic electromagnetic field are reviewed. The incident electromagnetic field is allowed to have a zero or/and nonzero initial constant amplitude. Some interesting numerical results are obtained that include a high-number multipeak laser pulse and single or/and low-number multipeak plasma wake structures. It is also shown that there exists a combination of soliton and oscillation waves for plasma wake field. Also, the electron density exhibits multi-caviton structure or the combination of caviton and oscillation. A complete eigenvalue spectrum of parameters is given wherein some higher peak numbers of multipeak electromagnetic solitons in the plasma are included. Moreover, some interesting scaling laws are presented for field energy via numerical approaches. Some implications of results are discussed.
  • HE Ju-long, LIU Zhong-yuan, YU Dong-li, XU Bo, TIAN Yong-jun
    Isoelectronic BCxN compounds have been researched widely. However, electron-deficient boron-rich B-C-N solids have also attracted much interest both theoretically and experimentally. In this paper, we introduce the synthesis, theoretical prediction, and physical properties of crystalline ternary B-C-N compounds. Our recent work reveals that the novel B-C-N materials may have a wide variety of crystal structures with different characteristics.
  • XIA Kai, YAO Xiao-yan, LIU Jun-ming
    The Wang-Landau algorithm is an efficient Monte Carlo approach to the density of states of a statistical mechanics system. The estimation of state density would allow the computation of thermodynamic properties of the system over the whole temperature range. We apply this sampling method to study the phase transitions in a triangular Ising model. The entropy of the lattice at zero temperature as well as other thermodynamic properties is computed. The calculated thermodynamic properties are explained in the context of the magnetic phase transition.
  • CHEN Hong-sheng, QI Jun-jie, LIAO Qing-liang, HUANG Yun-hua, ZHANG Yue
    The direct growth of a tetrapod-like ZnO nanostructure has been accomplished by using a thermal oxidation method without any catalysts. Studies on the field emission properties of the ordered ZnO nanotetrapods films found that the shape of the ZnO nanotetrapods has considerable effect on their field emission properties, especially the turn-on field and the emission current density. Compared with the rod-like legs ZnO nanotetrapods, the nanotetrapods with acicular legs have a lower turn-on field of 2.7 V/μm at a current density of 10 μA/cm2, a high field enhancement factor of 1830, and an available stability. More importantly, the emission current density reached 1 mA/cm2 at a field of 4.8 V/μm without showing saturation. The results could be valuable for using the ZnO nanostructure as a cold-cathode field-emission material.
  • WANG Rui, DENG Hui-qiu, YUAN Xiao-jian, HU Wang-yu
    In the present paper the adsorption kinetics of the hydrogen molecule on the (111) and (100) surfaces have been studied with the model proposed by Panczyk and the grand canonical Monte Carlo simulation method. The equilibrium adsorption isotherms are calculated at five different temperatures ranging from 314 K to 376 K and compared with the experimental equilibrium adsorption isotherms. The effects of temperature and pressure on coverage are also analyzed.
  • MA Rong, LIU Mei, HUANG Gui-qin
    Using the linear response-linearized Muffin-tin orbital (LR-LMTO) method, we study the electronic band structure, phonon spectra, electron-phonon coupling and superconductivity for c-axis ferromagnetic-like (F-like) and antiferromagnetic-like (AF-like) structures in ternary silicide CaAlSi. The following conclusions are drawn from our calculations. If Al and Si atoms are assumed to arrange along the c axis in an F-like long-range ordering (-Al-Al-Al- and Si-Si-Si-), one could obtain the ultrasoft B1g phonon mode and thus very strong electron-phonon coupling in CaAlSi. However, the appearance of imaginary frequency phonon modes indicates the instability of such a structure. For Al and Si atoms arranging along the c axis in an AF-like long-range ordering (-Al-Si-Al-), the calculated electron-phonon coupling constant is equal to 0.8 and the logarithmically averaged frequency is 146.8 K. This calculated result can correctly yield the superconducting transition temperature of CaAlSi by the standard BCS theory in the moderate electron-phonon coupling strength. We propose that an AF-like superlattice model for Al (or Si) atoms along the c direction may mediate the inconsistency estimated from theory and experiment, and explain the anomalous superconductivity in CaAlSi.
  • HE Jian-e
    We derive from the Kaluza-Klein theory a formula for the gravity-induced phase shift around a circuit loop, which amounts to the order of 10-6 We propose experiments to detect this phase shift by using the high-Tc d-wave Josephson junction, which is included in a cuprate superconductor circuit loop. By rotating the loop around the horizontal axis, the gravity-induced phase shift can be detected as a frequency shift. These settings can also be used in turn to determine the gravitational constant. This method will be sensitive and accurate.
  • HUANG Chao-shang
    We review the neutral Higgs boson (NHB) contributions to rare leptonic and semi-leptonic B decays in 2HDM and MSSM with large tan β. We present relevant Wilson coefficients of NHB induced operators. We discuss branching ratios and other observables in those decays. Finally we present CP violation in rare leptonic B decays.
  • CAO Li-ke, LIANG Hong, PENG Dan-tao, YANG Tao, YUE Rui-hong
    Gaudin model is a very important integrable model in both quantum field theory and condensed matter physics. The integrability of Gaudin models is related to classical r-matrices of simple Lie algebras and semi-simple Lie algebra. Since most of the constructions of Gaudin models works concerned mainly on rational and trigonometric Gaudin algebras or just in a particular Lie algebra as an alternative to the matrix entry calculations often presented, in this paper we give our calculations in terms of a basis of the typical Lie algebra, An, Bn, Cn, Dn, and we calculate a classical r-matrix for the elliptic Gaudin system with spin.
  • ZHOU Hai-jun
    At sufficiently low temperatures, the configurational phase space of a large spin-glass system breaks into many separated domains, each of which is referred to as a macroscopic state. The system is able to visit all spin configurations of the same macroscopic state, while it can not spontaneously jump between two different macroscopic states. Ergodicity of the whole configurational phase space of the system, however, can be recovered if a temperature-annealing process is repeated an infinite number of times. In a heating-annealing cycle, the environmental temperature is first elevated to a high level and then decreased extremely slowly until a final low temperature T is reached. Different macroscopic states may be reached in different rounds of the annealing experiment; while the probability of finding the system in macroscopic state ? decreases exponentially with the free energy F α(T) of this state. For finite-connectivity spin glass systems, we use this free energy Boltzmann distribution to formulate the cavity approach of M?zard and Parisi [Eur. Phys. J. B, 2001, 20: 217] in a slightly different form. For the ?J spin-glass model on a random regular graph of degree K = 6, the predictions of the present work agree with earlier simulational and theoretical results.