Suppression of the plasma high-frequency electrical conductivity under a radiation field

Abstract

From the quantum mechanical viewpoint we derive the dielectric function of an electron plasma system in the presence of a radiation field. By using time-dependent wavefunctions for plasma electrons under the external ac field, we calculate the charge density fluctuation of the electronic system under a weak probing potential and the spectrum of the collective excitation is calculated and found to be strongly dependent upon the amplitude and frequency of the radiation field. We show, in the classical limit, that the reduction of the collective excitation frequency under the radiation field can be associated with the suppression of the plasma high-frequency reactive electrical conductivity. The result is consistent with the recent experimental observation of increased high-frequency mobility in two-dimensional electron gases under a radiation field.