在群论框架下电子三重态与声子耦合的理论研究

Theoretical studies on vibronic Jahn-Teller systems using group theory

本文基于绝热近似和群论导出了电声耦合系统的哈密顿量的一般形式,讨论了电声耦合系统中的电子算符和活跃的声子模式.应用幺正平移变换和能量最小化方法,进一步计算了正四面体群下T(e+t2)杨-泰勒系统中的激发态能量,从对称性的角度分析了T1电子态的能级分裂以及晶格体系的对称性破缺,得出了对称性的破缺方式和电声耦合系统密切相关的结论.结果表明:通过群论与对称性分析完全可以定性地解释由于电声耦合所造成的简并电子态的能级分裂,在某些情况下还可以给出分裂后的基态与激发态的对称性.

A general form of Hamiltonian for vibronic Jahn-Teller systems is derived on the basis of adiabatic approximation and group theory. The electronic operators and active Jahn-Teller modes appearing in a vibronic system are also discussed. Further calculations of excited states in minima are carried out using unitary transformation method and energy minimization procedure. The results of energy splitting for an electronic triplet Jahn-Teller system are analyzed and compared with particular reference to tetrahedral and its related crystal systems. It is shown that the lift of electronic degeneracy can be quantitatively described by the decomposition of irreducible representations of related group and subgroups.