Lattice Relaxation Dynamics of Excitons and Elementary Nonlinear Processes in Photoinduced Structural Phase Transitions - Aggregation, Growth and Proliferation -

Abstract

We theoretically study the lattice relaxation dynamics of a photogenerated single exciton which finally results in a macroscopic domain in insulating solids. Especially, we focus on three elementary nonlinear processes of this domain formation, which we call aggregation, growth and proliferation. This domain formation phenomenon is usually called `photoinduced structural phase transition' (PSPT). In these three elementary processes, the exciton does not stay within a single adiabatic potential surface but transits diabatically between the different potential ones. Hence, the full-quantum-mechanical treatment is indispensable. As one of the models for this type of phase transition, we consider a strongly coupled many exciton-Einstein phonon system. This is our relevant system. We also assume this system to interact with even and odd reservoir modes as well as photons. The even modes couple linearly with Einstein phonons and dissipate their energies, while the odd modes couple linearly with excitons and non...