Electronic correlation effects (exiton manifestation) in the single-particle band structure of nonmetallic crystals

Abstract The effect of electron correlation on the single‐particle spectrum of electrons in nonmetallic crystals is investigated starting from the full Hamiltonian of the interacting electron system. By these effects excitons become manifest in the single‐particle spectrum entering Dyson's equation of the corresponding Green's functions via the screeningof the Coulomb potential in the self‐energy. Dyson's equation is solved to render the spectral function by a systematic perturbative approach recently introduced in connection with the electron gas problem. The single‐particle spectrum exhibits modified main bands accompanied by exciton satellites contributing remarkably to the density of states. This picture appears not to be fully obtained by the electronic polaron theory starting from a model Hamiltonian which is also investigated in this study.