Numerical Experiments on the Absorption Lineshape of the Exciton under Lattice Vibrations. II. The Average Oscillator Strength per State.

Abstract

We introduce the average oscillator strength per state (AOSPS) as the ratio of the exciton absorption lineshape and the density of exciton states at a given energy. The numerical investigation of the AOSPS spectra and their dependence on temperature and dimensionality shows contrasting behaviour on the two sides of the absorption peak. Unambiguously we can ascribe the high-energy side to indirect transitions and the low-energy tails to momentarily localized states with giant oscillator strength. The calculated spectra of the participation ratio lend further support to this viewpoint.