表面极化子光学声子平均数的磁场和温度依赖性

采用变分法、幺正变换和拉格朗日乘子法,研究了有限温度下纯二维晶体中表面磁极化子的性质.讨论了表面光学声子平均数、磁极化子振动频率λ与磁场B、温度T及Lsgrange乘子u之间的关系.对KCl晶体进行了数值计算,结果表明:磁极化子振动频率、表面光学声子平均数均随磁场B的增强而增加,且随温度T升高而增加.当bgrange乘子u超出慢电子范围时磁极化子振动频率、表面光学声子平均数均随u增加而增大且变化越来越显著.

Magnetic Field and Temperature Dependence of the Mean Number of Optical Phonons of Surface Polaron

In recent years,the problem of a magnetopolaron has been of considerable interest.Larsen proposed a fourth-order perturbation method to calculate the ground state energy of two-dimensional polaron in a magnetic field.Employing Haga’s perturbation method,Ze et al.derived an effective Hamiltonian for the interface magnetopolaron in polar crystals at zero temperature,in which the interactions of both bulk LO phonons and interface phonons have been taken into account.Using the Green’s function method,Wei et al,studied the cyclotron resonance mass of an electron interacting with bulk longitudinal optical(BO)phonons as well as surface optical(SO)phonons in a polar crystals slab at finite temperature and found that the temperature dependence of magnetopolaron depends strongly on the strength of the magnetic field.Wang et al,investigated the magnetic field and temperature dependence of the properties of a magnetopolaron at the interface of polar-polar crystals in an external magnetic field by using the generalized Haga perturbation method.By using variational method of Pekar type,Zhou and co-workers studied the energy levels of strong coupling magnetopolaron in disk-shape quantum dot(QD)and quantum well(QW).Madkour et al. studied the effect of magnetic field on surface polaron states in a polar crystal interface and emphasized the result that the presence of magnetic field leads to a local potential for charge carriers at the interface.Based on Wigner-Brillouin theory,D.E.N.Brancus and G.Stan investigated the state energy of an anisotropic three-dimensional polaron in a magnetica field.One of our authors have done a lot of works on the proterties of the surface magnetopolaron.The properties of surface polaron in a magnetic field have been further discussed by the present authors and co-workers.Tokuda studied the property of the mean number of the optical and the piezoelectric polarons and the mean number of the acoustic and optical polarons via deformation potential by using improved variational method.However,the mean number of optical phonon of surface magnetopolarons at finite temperature has not been studied so far.In this paper,the properties of surface magnetopolaron which is a strong,weak-coupling of optical phonon was discussed by using Tokuda’s improved linear combination operator,the unitry transformation and the Lagrange multiplier methods.The mean number of optical phonons of the strong,weak-coupling magnetopolaron are calculated.Numerical calculations for KCl crystals,as an example,are performed.The relation of the vibration frequency and the mean number of optical phonons to magnetic field B,temperature T and Lagrange multiplier u are discussed.The result illustrates that the vibration frequency λ of surface magnetopolaron will increase with increasing magnetic field B,temperature T and Lagrange multiplier u;the mean number of optical phonons will increase with increasing B,T and u.