高分子中双激子态对外电场的线性响应

THE LINEAR RESPONSE OF BIEXCITON TO EXTERNAL ELECTRICAL FIELD IN POLYMER 

在外电场中，非简并基态共轭高分子中的双激子具有反向极化的奇异特性．利用响应函数求得高分子链的双激子态在任意频率下的动态极化率 χ（ ω） ，并通过求 ω→０ 极限，给出双激子态的静态极化率 χ，证实了 χ确实为负值．并与激子态和基态作了比较，分析了分子负极化率的起因．考察了响应函数在低频时的行为，指出激子和双激子的激发浓度增大会导致材料折射率 ｎ（ ω） 向不同方向变化．

In external electrical field,the self\|trapping biexciton in non\|degenerate ground state conjugated polymer has an abnormal characteristic\|its static polarizability was found to be negative.We calculated the dynamic response function χ(ω) of biexciton.By putting ω to the zero limit,we got the static polarizability χ which proved to be negative.We compared it with that of self\|trapping exciton and ground state and gave some analysis on the origin of negative polarizability.Finally,we investigated the behavior of χ(ω) when ω is small,and deduced that if more biexcitons are excited,the n(ω) of the material will decrease,whereas if more excitons are excited,the n(ω) will increase. PACC: 7150; 6320; 7870