Theory of Photoinduced Phase Transitions

TL;DR

This paper reviews the development of theories explaining photoinduced phase transitions, highlighting classical and electronic models, recent ultrafast dynamics, and the importance of electron-lattice interactions.

Contribution

It provides a comprehensive overview of theoretical approaches to photoinduced phase transitions, emphasizing recent advances in understanding ultrafast and coherent dynamics.

Findings

Classical models explain coarse-grained dynamics.

Electronic models describe ultrafast and coherent phenomena.

Certain transitions are nearly unidirectional due to electronic processes.

Abstract

Theories of photoinduced phase transitions have developed along with the progress in experimental studies, especially concerning their nonlinear characters and transition dynamics. At an early stage, paths from photoinduced local structural distortions to global ones are explained in classical statistical models. Their dynamics are governed by transition probabilities and inevitably stochastic, but they were sufficient to describe coarse-grained time evolutions. Recently, however, a variety of dynamics including ultrafast ones are observed in different electronic states. They are explained in relevant electronic models. In particular, a coherent lattice oscillation and coherent motion of a macroscopic domain boundary need appropriate interactions among electrons and lattice displacements. Furthermore, some transitions proceed almost in one direction, which can be explained by considering relevant electronic processes. We describe the history of theories of photoinduced phase transitions and discuss a future perspective.