多原子极性晶体中表面激子的性质  

PROPERTY OF SURFACE EXCITON IN POLYATOMIC POLAR CRYSTALS

作　　者：肖景林[1] 孙宝权[1] 

机构地区：[1]内蒙古民族师范学院,通辽028043

出　　处：《发光学报》1992年第2期123-135,共13页Chinese Journal of Luminescence

基　　金：内蒙古自然科学基金

摘　　要：本文研究多原子极性晶体中表面激子的性质.采用微扰法导出表面激子的有效哈密顿量.多支LO声子对表面激子的自陷能和有效势的影响是相互独立的.对于Wannier激子,电子、空穴间的相互作用的有效势仍是库仑型的,只是介电常数约化为.多支LO声子的作用使激子的自陷能更低.并得到激子的自陷条件.In the early 1970's, Ibach made the low energy electron diffracting experimentation on ZnO etc. semiconductor surface. Since then the surface polaron in the crystals have been of considerable interest. Many scholars have studied the surface polaron problem. The properties of the exciton in the surface layer of crystals influence the optical properties of the crystals very remarkably. X. X. Liang discussed the properties of weak-coupling surface exciton in polar crystals. Most polar crystals are diatomic. In these crystals there is only one mode of longitudinal optical (LO) phonon. The properties of crystals have bean studied by a great variety of techniques, in which discussions are limited only for the case of one LO phonon branch. However, a large number of polar crystals, with several atoms per unit cell, have more than one LO phonon. For example, in cuprite such as Cu2O there are two LO phonon modes and in a large number of perovskites (BaTiO3.....)and quaternary compound semiconductors (AlGaAsSb....) there are more than two modes. In recent years, a lot of scholars investigated the polaron problem of multiple LO phonon branches. However, the exciton in polyatomic polar crystal has not yet been investigated. The ground state energy of a weak, intermediate and strong-coupling exciton in polyatomic polar crystals has been obtained by means of perturbation and linear-combination-operator method by one of the authors. Recently the' properties of a strong-coupling surface exciton in polyatomic polar crystals has been studied by using a Jinear-combination-operator method by one of the authors. In this paper, the effective HamiJton;an of the surface exciton in polyatomic polar crystals is derived by perturbation method.The Hamiltonian of a polyatomic surface exciton-phonon system is We introduce two unitary transformations U1 and U2 given byWe calculate the effective Hamiltonian and the renormaJized mass of the mass centre and the reduction of surface exciton by perturbation method.For Wannier exciton, results are r

关 键 词：多原子晶体 表面激子 微扰法 

分 类 号：O734[理学—晶体学]