Photoinduced phase transitions

Abstract

Optically induced ultrafast electronic excitations with sufficiently long lifetimes may causestrong effects on phase transitions like structural and ones and on supercooling, supersaturation, etc. Examples are the transitions , , , and , solid. Photoinduced formation of graphene and water condensation of saturated orsupersaturated vapor due to increased bonding amongst water molecules are of particularinterest. These nonequilibrium transitions are an ultrafast response, on a few hundred fstime scale, to the fast low to large energy electronic excitations. The energy of the photonsis converted into electronic energy via electronic excitations changing the cohesive energy.This changes the chemical potential controlling the phase transition. In view of theadvances in laser optics photon induced transitions are expected to become an active areain nonequilibrium physics and phase transition dynamics. Conservation laws like energy orangular momentum conservation control the time during which the transitions occur. Sincethe photon induced effects result from weakening or strengthening of the bonding betweenthe atoms or molecules transitions like solid/liquid, etc can be shifted in bothdirections. Photoinduced transitions will be discussed from a unified point of view.