摘要
在Huybrechts关于强耦合极化子的模型基础上,采用LLP变分法研究了极性晶体中激子与IO声子强耦合、与LO声子弱耦合体系的基态能量,推导出了激子的自陷能和诱生势的表达式,并以AgCl/AgBr晶体为例进行了数值计算,结果表明,激子的自陷能不仅与激子的坐标z有关,而且电子-空穴间距离ρ对激子自陷能的影响也十分显著;激子的诱生势不仅与电子-空穴间距离ρ有关,而且激子距离晶体界面的位置z对诱生势的影响也十分显著。
Based on model of Huybrechts strong-coupling polaron, the ground state energy of the system., in which the excitons interact with both the weak-coupling bulk longitudinal-optical （LO） phonons and strong-coupling inter- face-optical （IO） phonons in a polar crystal, is studied by using the Lee-Low-Pines variational method, the self-trap- ping energy and the induced potential of the excitons are derived. The results are shown as following： 1. The self-trapping energy of the excitons is composed of two parts. One part is the polaron effects resulting from the exciton-LO phonon interaction, the other part is induced by the exciton-IO phonon interaction. The self-trap- ping energy Ee,h-LO^tr, which is produced by the interaction between the exciton and LO-phonon, will increase with in- creasing the coordinate z, it tends to a constant finally. The self-trapping energy Ee,h-LO^tr, which is induced by the in- teraction between the exciton and IO-phonon, will increase with decreasing the coordinate, especially near the inter- face, the decrease in z will lead to drastic increase in Ee,h-LO^tr. It is indicated that near the interface, the contribution of the electron-IO phoflon interaction to the self-trapping energy of the excitons is dominant, whereas the exciton in the bulk far from the interface, the contribution of the electron-LO phonon interaction to the self-trapping energy of exciton is dominant. The influence of the distance p between the electron and hole on the self-trapping energy Ee,h-LO^tr is also remarkable. Ee,h-LO^tr will increase with increasing p. With p increasing, the decrease in coordinate z will lead to drastic increase in Ee,h-LO^tr 2. The induced potential of the excitons is also composed of two parts, one part is the polaron effects produced by the interaction between the exciton and LO phonons, the other part is induced by the exciton-IO phonon interac- tion. The variation law of the induced potential Ve,h-LO and Ve,h-LO resulting from the exciton-LO phonon and exciton-IO phonon interaction, respectively, is agreement with the variation law of the induced potential produced by the weak- coupling exciton-LO pbonon interaction in 3D polar crystal and the strong-coupling exciton-SO phonon interaction in 2D polar crystal respectively. The influence of the coordinate of the exciton on the induced potential Ve,h-LO and Ve,h-LO is notable. Ve,h-LO increases with increasing the coordinate z. With z increasing, the increase in the distancep between the electron and hole will lead to drastic decrease in Ve,h-LO. The induced potential Ve,h-LO decreases with increasing z. With z decreasing, the decrease in p will lead to drastic increase in induced potential Ve.h_lo. The results show that the influence of the surface and interface phonon in polar crystal can not be neglected, h is especially important for the polar slab, quantum well and heterostructures, in which the carriers are both strong-cou- pling with surface or interface optical phonon and weak-coupling with bulk longitudinal optical phonon.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2007年第6期837-842,共6页
Chinese Journal of Luminescence
基金
河北科技师范学院博士基金资助项目(2006D001)~~
关键词
激子
强耦合
自陷能
诱生势
exciton
strong-coupling
self-trapping energy
induced potential
