Effects of polarons on static polarizabilities and second order hyperpolarizabilities of conjugated polymers  

作　　者：王亚东 孟艳 邸冰 王淑玲 安忠 

机构地区：[1]College of Physics,Hebei Normal University [2]Hebei Advanced Thin Films Laboratory [3]Zhangjiakou Vocational and Technical College

出　　处：《Chinese Physics B》2010年第12期1-8,共8页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.10574037);the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-05-0262);the Hebei Provincial Outstanding Youth Science Fund(Grant No.A2009001512);the Key Project of Ministry of Education of China(Grant No.210021);the Natural Science Fund of Hebei Province,China(Grant No.A2010000357);the Educational Commission of Hebei Province, China(Grant No.2007124)

摘　　要：According to the one-dimensional tight-binding Su-Schrieffer-Heeger model, we have investigated the effects of charged polarons on the static polarizability, axx, and the second order hyperpolarizabilities, γxxxx, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su Schrieffer-Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron-electron interactions on αxx and γxxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of αxx and γxxxx increase as the on-site Coulomb interaction U increases for U 〈 Uc and decrease with U for U 〉 Uc, where Uc is a critical value of U at which the static polarizability or the second order hypcrpolarizability reaches a maximal value of αxx or γxxxx. It is found that the effect of the e-e interaction on the value of αxx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γxxxx is sensitive both to the ratio of U to V and to the size of the molecule.According to the one-dimensional tight-binding Su-Schrieffer-Heeger model, we have investigated the effects of charged polarons on the static polarizability, axx, and the second order hyperpolarizabilities, γxxxx, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su Schrieffer-Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron-electron interactions on αxx and γxxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of αxx and γxxxx increase as the on-site Coulomb interaction U increases for U 〈 Uc and decrease with U for U 〉 Uc, where Uc is a critical value of U at which the static polarizability or the second order hypcrpolarizability reaches a maximal value of αxx or γxxxx. It is found that the effect of the e-e interaction on the value of αxx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γxxxx is sensitive both to the ratio of U to V and to the size of the molecule.

关 键 词：POLARON nonlinear optics conjugated polymer 

分 类 号：O437[机械工程—光学工程]