Nonequilibrium phase change in gold films induced by ultrafast laser heating.

Ultrafast laser-induced melting in a gold thin film is simulated by an integrated continuum-atomistic method with the extended Drude model for dynamic optical properties. The local order parameter of atoms is used to identify solid and liquid regions. It is shown that the film is superheated in the early nonequilibrium stage and the melted region grows very quickly with a very high rate of melting up to ∼13,300 m/s. It is also found that the continuum approach could significantly underestimate the ultrafast phase-change response, and temperature-dependent optical properties should be considered in atomic-level modeling for ultrafast laser heating.