1993年, 第20卷, 第2期　
刊出日期：1993-09-15

  

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  Resonant Magnetic Fields of a Magnetopolaron in a Parabolic Quantum Dot

  Ka-Di ZHU, Shi-Wei GU

  理论物理通讯. 1993, 20(2): 129-134.

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  It is shown that for a resonant magnetic field, the two cyclotron masses (m₊^* and m_-^*) in a parabolic quantum dot are split into two cyclotron masses, respectively. The cyclotron mass (m₊^*) decreases with decreasing the size of the quantum dot, the stronger the magnetic field strength, the larger the cyclotron mass. The lower branch of the cyclotron mass (m_-^*) increases linearly with increasing the magnetic field strength. The upper branch of the cyclotron mass (m_-^*) is larger than the bare band mass and enhances as the magnetic field strength increases.
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  Dissipative Effects on Resonant Tunneling

  Ming-Li ZHOU, Yu-Mei ZHANG, Xiang WU

  理论物理通讯. 1993, 20(2): 135-140.

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  The resonant tunneling of a particle coupled with a set of local bosons can be mapped onto the single-site model in an appropriate time scale. In this paper we investigate the process of the particle through a barrier associated with the dissipative source. The frequency and temperature-dependent tunneling probability has been evaluated explicitly in the spirit of independent boson assumption by using golden rule for transition rate. The character of sideband structure is revealed and the tunneling current with dissipation is also given.
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  The Binding Energy of an Exciton in Type-Ⅱ Quantum Wells with a Dielectric Mismatch

  Er-Zhen GAO, Shi-Wei GU

  理论物理通讯. 1993, 20(2): 141-146.

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  From a general viewpoint, the binding energy of the excitons in type-Ⅱ hetero-quantum- wells with the presence of a dielectric mismatch is discussed by making use of image potentials, variational method and infinite-potential-barrier model. The calculation is performed for various parameters including the electron-hole mass ratio σ, dielectric constant ratio δ and well width d. A static Gabovish-type potential is engaged to describe the image potential inside the well. It is found that the image potential may play an important role in the formation of the excitons. The contribution of image potentials to the binding energy is compared with binding energy for two kinds of type-I1 hetero-QWs, GaSb-InAs-GaSb and AlAs-GaAs-AlAs. In these two cases, the image potentials are above 10% of the corresponding binding energies.
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  An Extension of the Pseudo-Fermion Method

  Ming SHAW, Fu-Sui LIU

  理论物理通讯. 1993, 20(2): 147-152.

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  Using Abrikosov's pseudo-fermion representation of a single spin S and Larsen's note with pseudo-fermion energy λ = 0, we describe a procedure which allows calculation of spin-spin correlation as well as spin-electron (hole) correlation using standard methods including the linked duster theorem of diagrammatic perturbation theory.
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  Four-Level Transition Analysis of the Polar Kerr Effects in Ferrornagnetics

  Wen-De ZUO, Gong-Qiang LIU

  理论物理通讯. 1993, 20(2): 153-158.

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  In ferromagnetics, besides originating from the splitting of the excited state resulting from the spin-orbit interaction, magneto-op tical effects also stem from the splitting of the ground state caused by the exchange interaction and the applied field. Theoretical calculation according to this view shows that, in ferromagnetics, there are electron transitions corresponding to two pairs of left- and right-handed circularly polarized lights, and the polar Kerr rotation θ_κ depends linearly on magnetization M in both regions of low temperature and high temperature for the material with high Curie temperature T_c. When considering the different oscillator strengths in normal temperature region between the above two regions, we obtain the expressions of θ_κ as forms similar to θ_κ ≅∑_n=0α(M/T)ⁿ and θ_κ≅∑_n=0βM^n+l/Tⁿ.
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  Intervalley Γ- X Deformation Potentials in Ⅲ-V Zincblende and Si Semiconductors by Ab Initio Pseudopotential Calculations

  Jian-Qing WANG, Zong-Quan GU, Ming-Fu LI, Wu-Yan LAI

  理论物理通讯. 1993, 20(2): 159-170.

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  Intervalley Γ- X deformation potential constants (IVDP's) have been calculated by first principle pseudopotential method for the Ⅲ-V zincblende semiconductors Alp, AlAs, AlSb, Gap, GaAs, GaSb, InP, ZnAs and ZnSb. As a pro to type crystal we have also carried out calculations on Si. When comparing the calculated IVDP's of LA phonon for Gap, InP and InAs and LO phonon for AlAs, AlSb, GaAs, GaSb and InSb with a previous calculation by EPM in rigid approximation, good agreements are found. However, our ab initio pseudopotential results of LA phonon for AlAs, AlSb, GaAs, GaSb and InSb and LO phonon for Gap, InP and ZnAs are about one order of magnitude smaller than those obtained by EPM calculations, which indicate that the electron redistributions upon the phonon deformations may be important in affecting Γ- X intervalley shatteri'ngs for these phonon modes when the anions are being displaced. In our calculations the phonon modes of LA and LO at X point have been evaluated in frozen phonon approximation. We have obtained, at the same time, the LAX and LOX phonon frequencies for these materials from total energy calculations. The calculated phonon frequencies agree very well with experimental values for these semiconductors.
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  Variat ional-Cumulant Expansion on the Five-State Clock Model

  Wen-Jun MA, Tian-Lun CHEN

  理论物理通讯. 1993, 20(2): 171-178.

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  The phase transition of the 5-state dock model has been studied by standard variationalcumulant expansion (VCE) method. We calculated the fiee energy (F) and the internal energy (E) to the fourth order approximation and the specific heat (C) to the third order approximation with the trial action of one variational parameter. The position of the phase transition point given above is in agreement with the results of the Monte Carlo (MC). We also calculated the model to the third order approximation with the trial action of two variational parameters. The comparison of the results for one variational parameter with that for two is given. From this, we can see how the choice of the trial action affects the result and the trial action must be equivalent to the action of the system. All above has shown that the VCE is convergent in the calculation of the 5-state clock model.
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  Transient Properties of One-Dimensional Stochastic Processes: Unified-Colored-Noise Approximation

  Dong-Cheng MEI, Li CAO, Da-Jin WU

  理论物理通讯. 1993, 20(2): 179-186.

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  By virtue of the unified-colored-noise approximation the formulas of mean, variance and skewness of first-passage-time distributions (FPTD) for the systems driven by colored noise are derived. The mean and variance of FPTD of bistable system driven by colored noise are calculated. The approximation expressions of the mean, variance and skewness of FPTD for the colored cubic model of a dye laser are obtained. The role of the "color" of pump noise in the dye laser transient is analyzed.
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  Zakharov-Shabat Equations for Dark Soliton Solutions to the NLS Equation

  Nian-Ning HUANG, Zong-Yun CHEN

  理论物理通讯. 1993, 20(2): 187-194.

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  For dark soliton solutions of the NLS equation, an inverse scattering transform is redeveloped. Deductions are essentially simplified in terms of an auxiliary spectral parameter from the beginning. Equations of inverse scattering transform in the form of Zakharov-Shabat are found to be simpler than those in the form of Marchenko. An explicate expression for the dark N-soliton solution and its asymptotic behaviors in the limits as t →±∞ are simply derived.
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  A New Representation of Birman-Wenzl Algebra and Solution of Yang-Baxter Equation

  LU-YU WANG, Jim-Hui DAI, Jun ZHANG

  理论物理通讯. 1993, 20(2): 195-200.

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  Corresponding to a new braid group representation, a representation of Birman-Wenzl algebra is provided. The trigonometric type solutions of spectral-dependent Yang-Baxter equation are obtained in the framework of the Yang-Baxterization, and the related vertex models are also mentioned.
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  Irreducible Representations of Quasispin Group S0(5)_t

  Qi-Zhi HAN, Hong-Zhou SUN, Jia-Jun WANG

  理论物理通讯. 1993, 20(2): 201-212.

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  A recurrent method for irreducible represen tation calculation of five-dimensional quasispin group S0(5)_t is proposed. The explicit IRs in physical orthonormal basis with multiplicity up to three, such as (2tt), (2t + 2t) and (2ε) when t = 1, 3/2, 2, 5/2 are given.
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  One Loop Effects of Supersymmetry on Z Decays into bb

  Chong-Sheng LI, Jin-Min YANG, Bing-Quan HU

  理论物理通讯. 1993, 20(2): 213-220.

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  Virtual effects of supersymmetry on the partial width Γ(Z → bb) and on the branching ratio R_b = Γ(Z → bb)/Γ(Z → hadrons) are calculated in the minimal supersymmetric standard model. We found that the virtual gluino contribution to the width is negligibly small if the squark and gluino masses take their experimen t-allowed values. Also, we have calculated the contributions to Rb from the charged Higgs and charginos. As to the discrepancy between two previous works about the virtual chargino correction, our calculations provide a confirmation.
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  Integrable Systems and Two-Dimensional Gravity from Conformally Reduced WZNW Model

  L. CHAO

  理论物理通讯. 1993, 20(2): 221-230.

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  Imposing constraints with an integer ordering on WZNW model a large series of conformal invariant integrable systems will result. In this letter, a general approach for imposing the first and the second class constraints based on an arbitrary grading scheme of the Lie algebras of the WZNW groups is presented. The first order constraints correspond to integrable systems containing super Toda and conformal affine Toda systems as examples and are related to two-dimensional induced gravity, whilst the second order constraints correspond to supersymmetric-like integrable systems containing super Toda and conformal affine super Toda systems (for super WZNW groups) and are conjectured to be related to twodimensional induced supergravity.
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  Charged Vortices in an Abelian Higgs Model with Chern-Simons Term at Finite Temperature

  Ing AN, Shu-Xue DING, He-Shan SONG

  理论物理通讯. 1993, 20(2): 231-238.

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  Charged vortex solutions are found iri a (2+1)-dimensional Abelian Higgs model with Chern- Simons term at finite temperature. It is shown that there exists a finite critical temperature at which vortices disappear and it implies that the system changes fiom superconducting state to normal state at this critical temperature.
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  A General Theory of Self-consistent Field Beyond Hartree-Fock

  Huan-Wu PENG

  理论物理通讯. 1993, 20(2): 239-242.

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  A general scheme is devised in the formalism of second quantization to make the Hamiltonian of an electronic system diagonal by a unitary transformation together with a suitable choice of the basis of one-electron wave functions. The scheme can be regarded as a generalization of the HartreeFodr approximation of self-consisten t field, and can be carried to any order of approximation in principle. Formulae for the lowest order approximation beyond Hartree Fodr are given.
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  Diffraction Pattern for a Class of One-Dimensional Quasicrystals

  Xiu-Qing HUANG, Dang MO, You-Yan LIU

  理论物理通讯. 1993, 20(2): 243-248.

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  We study the diffraction pattern and indexing problems for a class of 1D quasiperiodic lattices, for which the substitution rules are B ⇒ BA and A ⇒ BAB. The similarity property of diffraction pattern has been found. The numerical calculation is performed to prove the theoretical results.
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  Phason Contribution to the Lattice Heat Capacity and Thermoconductivity

  M. Apostol

  理论物理通讯. 1993, 20(2): 249-252.

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  The phason contributions to the lattice heat capacity and thermoconductivity are obtained in the low-temperature limit for quasi-one-dimensional compounds. They are concentrated around temperatures related to the pinning frequency and the heat capacity is controlled by the density of states while the thermo,conductivity is governed by the phason velocity.
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  A Study of ¹⁶O + ¹²C Elastic Scattering at E/A = 10 MeV in the α-Particle Model

  Yong-Xu YANG, Qing-Run LI, En-Guang ZHAO

  理论物理通讯. 1993, 20(2): 253-256.

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  Using a folding model based on the α-particle model, the differential cross sections for ¹⁶O + ¹²C elastic scattering at 168 MeV have been calculated. This folding model, having no need of the renormalization, provides a good description of the experimental data.