Photoinduced semiconductor-metal phase transition in a peierls system

Abstract

The dynamical equation for the order parameter of the metal-semiconductor phase transition, as well as the kinetic equation for the density of nonequilibrium electron-hole pairs of a Peierls system in a light field, has been derived. An expression for the time τ of the nonthermal photoinduced semiconductor-metal phase transition has been obtained from these equations for the case of an ultrashort light pulse. It has been shown that, to initiate the phase transition, the energy density W of the light pulse must be higher than the critical value W c. The W c, τ, and optical absorption coefficient γ0 that are calculated in the framework of the proposed model are in agreement with the experimental data (W c ≈ 12 mJ/cm2, τ ≈ 75 fs, and γ0 ≈ 105 cm−1) on the irradiation of a vanadium dioxide film by a laser pulse with a duration of τp ≈ 15 fs, a photon energy of ħθ0 = 1.6 eV, and an energy density of W = 50 mJ/cm2.