Nonequilibrium phase transition in v-group semimetals,induced by ultrashort laser pulses

Coherent, totally symmetric large-amplitude phonons in bismuth and antimony were investigated by the pump—probe method using femtosecond laser pulses. The obtained results are compared to time-resolved Raman data. It is shown that intense photoexcitation by laser pulses with a duration shorter than the lifetime and reverse phonon frequency in Bi and Sb can lead to a nonequilibrium semimetal—metal phase transition, most likely caused by the instability of the crystal’s electron subsystem.