Local-field effects and excitonic polaritons in semiconductors: A new insight

Abstract

The influence of the local-field effects on the interpretation of the excitonic polarition dispersion curves in cubic semiconductors is investigated. It is shown that in real compounds for which the background dielectric constant is appreciably greater than one and for which the electron and the hole of the exciton are weakly bound, the usual description of the polariton effect is no more valid. In particular, the longitudinal-transverse splitting no longer preserves the center of gravity of the optically allowed multiplet; as a consequence, the value of the exchange energy which can be deduced from the available experimental data can be modified up to an order of magnitude.