Femtosecond-scale response of GaAs to ultrafast laser pulses RID A-7793-2008

Abstract

We present nonadiabatic simulations of the coherent response of crystalline GaAs irradiated by intense femtosecond-scale laser pulses. Above a threshold fluence, which corresponds to promotion of about 12% of the valence electrons into the conduction band, the lattice is destabilized and the electronic band gap collapses to zero. This confirms the nonthermal nature of recently observed structural changes driven by electronic excitations and occurring during the first few hundred femtoseconds.