采用线性组合算符法和幺正变换方法,研究极性晶体膜中束缚极化子的基态能量、自陷能随膜厚d的变化关系。得出束缚极化子的自陷能由两部分组成:第一部分是由于电子-体LO声子相互作用所引起的(E^tre-LO)极化子效应;第二部分则是电子-SO声子相互作用引起的。后者又包含两部分,分别是电子与极性膜中两支表面声子相互作用的贡献(E^tre-SO(+),E^tre-SO(-))。通过对KCl半导体膜的数值计算表明,E^tre-LO随膜厚d的增加而增加;但是E^tre-SO、极化子的振动频率以及电子-声子相互作用所产生的总自陷能E^tre-ph随膜厚d的增加而减少,当膜厚大于5nm时,总自陷能E^tre-hp趋于一稳定值。另外,由于束缚势的存在,使极化子的振动频率增大,这主要是由于束缚势的存在,使电子一声子间的相互作用增强,极化子效应增大而引起的。
Taking into account the interaction of an electron with bulk longitudinal-optical (LO) and surface longitudinal-optical (SO) phonons, we study the ground state energy and self-trapping energy of the bound polaron in a polar slab by using the Huybrecht's linear combination operator method. The ground state energy and the self-trapping energy are all derived as function of slab thickness. E^tr e-ph includes two parts, one is E^tr e-LO, the other is E^tre-SO, and E^tre-SO also includes two parts, E^tre-SO ( + ) and E^tre-SO ( - ) ; taking KCI as an example, E^tre-LO increases with the increase of the slab thickness, but E^tre-SO ,E^tre-ph and A all reduce with the increase of the slab thickness, and when the slab thickness d is more than 5 nm, E^tre-ph is about to a stable number. Especially, vibration frequency ( A ) increases when there is the Coulomb potential, because of the interactions are strengthened between the electrons and phonons.