双分子链中非线性多激子态的动力学研究  

Theoretical study of nonlinear multi-exciton dynamics in coupled molecular chains

作　　者：符晓倩 吕思远 王鹿霞 Fu Xiao-Qian;LüSi-Yuan;Wang Lu-Xia(Physics Department,School of Mathematics and Physics,University of Science and Technology Beijing,Beijing 100083,China)

机构地区：[1]北京科技大学数理学院物理系,北京100083

出　　处：《物理学报》2020年第19期266-274,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11774026,21961132023)资助的课题.

摘　　要：在超快激光激发下分子聚集体内有多个激子产生.针对具有链间耦合的双分子链系统,应用密度矩阵理论,在偶极-偶极近似和算符算术平均值近似下通过求解量子主方程计算了不同双链构型下的多激子动力学过程.研究发现在光激发作用下的多激子离域在双链分子系统中,在能量表象下形成激子态能带.激子态能带的宽度和激子占据能级随双分子链构型的不同而不同.对于链间和链内均为H型排列的分子链,激子态能带变宽,激子态优先占据在高阶能级上.在不同能级下的激子具有不同的动力学演变特点.若链间耦合较强,激子态通过链间耦合传递,与分子是否直接受到激发没有直接关系,激发态在两个链内的转移周期与最近邻的链间耦合有直接关系.Details of exciton dynamics in dye aggregates and supra-molecular complexes are substantially important for the functionality of molecular based opto-electronic devices.There are intensive theoretical studies of the multi-exciton dynamics in quantum dot structures but much less in molecular systems.Multiple excitons can be produced in molecular chains as well as two-dimensional and three-dimensional aggregates under an excitation of ultrafast strong laser pulse.According to the dipole arrangements of molecular chains,the coupled molecular chains are designed as H-H,H-J and J-H types of dipole configurations.In the scheme of density matrix theory,the dynamic processes of multiple excitons of different configurations are investigated by solving the quantum master equation through using the approximate dipole-dipole and expectation values of interest.The equations of motion for expectation values of interest governing the respective density operator are used to describe the temporal evolution of the multi-exciton states.It is found that the exciton energy band can be formed in the energy representation,and the multiple excitons are delocalized in the aggregates.The excitons represent different temporal evolutions excited by different resonant excitations.Compared with single-chain systems,double-chain systems have different degrees of blue shift or red shift due to interchain coupling.In the H-H type of aggregate,the electron population is lower if the double-molecule chain is simultaneously excited by the resonance frequency of a single molecule;the electron population increases to a certain extent if the frequency of the field is higher than the vibration frequency of a single molecule.The band width and the energy levels of the multiple excitons vary for different configurations of coupled molecular chains,and the wave packets show their own characters in these energetic levels.In the H-H type of aggregate,exciton state has priority to occupy the high-order energy level.The width of the exciton band of H-J type i

关 键 词：耦合双分子链 偶极-偶极近似 密度矩阵理论 多激子动力学 

分 类 号：O471.1[理学—半导体物理]