Theoretical Study Of The Properties Of Indirect Exciton Transport In Coupled Quantum Wells

Particle transport is an essential problem in physics.The indirect excitons in the coupled quantum well with long lifetime,low recombination rate,and dipole moment are convenient to be controlled by the electric field,so the indirect exciton system is an ideal place to study the transport phenomenon.Recently,the electrostatic conveyer experiment of indirect elections has been studied,and experimentally measured the average transport distance of indirect excitons via conveyer dependence on the exciton density and conveyer amplitude and velocity.However,the experimental phenomenon is still intriguing and worthy of further study.In this paper,inspired by previous theoretical research,by analyzing the indirect exciton photoluminescence pattern,we set up a time-dependent nonlinear Schrodinger equation including the non-Hermitian dissipation.The transport properties of coherent excitations in the moving lattice are understood by calculating the average transport distance of indirect excitons via conveyer.The analysis shows that the patterns are from two kinds of excitons approximately.The patterns near the laser spot come from the hot excitons which can be taken as classical particles whose transport can be well described by the classical diffusion equation.The patterns distant from the laser spot are formed by cooled excitons or coherent excitons.The coherent excitons also have two origins,one directly from the excitation center,which comes through cooling,the other through the conveyor to transport hot electrons and hot holes,which cool to form excitons.Inspired by the previous theoretical studies,we set up a time-dependent nonlinear Schrodinger equation including the non-Hermitian dissipation.The combination of real time-dependent evolution and imaginary-time propagation method is used to solve the model equation to achieve the purpose of describing the motion of coherent excitons,and at the same time achieve the cooling of excitons.By calculating the escape rate distribution of excitons,the average transport distance of excitons is obtained.Numerical analysis shows that the transport distance increases with the conveyer amplitude and tends to saturation,and exciton transport is the most effective at medium exciton densities and lattice velocities.The above numerical analysis also shows that the transport distance increases with the increase of cooling parameters,which indicates that cooling plays a key role in transportation.Furthermore,the influence of weak rej ection interaction on transport was discussed,and it was found that weak rej ection interaction was beneficial to transport and diffusion.Finally,two wave packets are used as the initial wave function for evolution,and a pattern consistent with the experimentally Photoluminescence images is obtained,and the luminescent stripes in the photoluminescent images are the result of the interaction between coherent excitations and motion.This study provides help to understand the dynamics of excitons in the moving lattice potential and to understand the non-Hermitian quantum walk in experiments.