Unifying the order and disorder dynamics in photoexcited VO2

Significance Structural phase transitions driven optically through the nonequilibrium population of excited electronic states have attracted great interest in many scientific disciplines as offering ultrafast control over the matter on timescales near the limit of atomic motions. However, atomic order or disorder characteristics are currently a critical issue in ultrafast photoinduced phase transitions. In this work, using an advanced real-time time-dependent density functional theory quantum simulation, we uncover the order and disorder processes strongly depending on the competition between thermal vibrations and photoinduced deterministic motion of atoms. We theoretically unify the order and disorder dynamics and provide a complete microscopic mechanism.