We present a theoretical study of ultrafast phase transitions induced by femtosecond laser pulses of arbitrary form. Molecular-dynamics simulations on time dependent potential-energy surfaces derived from a microscopic Hamiltonian are performed. Applying this method to diamond, we show that a nonequilibrium transition to graphite takes place for a wide range of laser pulse durations and intensities. This ultrafast transition $\left(\sim 100\hspace{0.5em}\mathrm{fs}\right)$ is driven by the suppression of the diamond minimum in the potential-energy surface of the laser excited system.

• Received 8 March 1999

DOI:https://doi.org/10.1103/PhysRevB.60.R3701