RENORMALIZED FREQUENCY-SHIFT OF SUPERRADIANT EXCITONS IN THIN SEMICONDUCTOR-FILMS

Abstract

The radiative frequency shift of an exciton in a thin semiconductor film, like its radiative level width, is shown to be superradiatively enhanced. Unlike the latter, however, a finite frequency shift can only be obtained after proper renormalization for the correlated system. The shift is found to be inversely proportional to the square of the factor k0d and proportional to the film thickness T; k0 = E(qn)/H(BAR)c, E(qn) being the exciton energy gap and d the lattice constant of the semiconductor. Therefore, the coherent frequency shift can be observed experimentally if one varies the thickness, or the exciton energy gap E(qn) by imposing high pressure.