Many-body interaction effects in quasi-one-dimensional photo-excited electron-hole systems

Abstract

The work in this thesis concerns rnany-body interaction effects in a quasi-onedimensional electron-hole plasma, which may be generated under intense photoexcitation in a semiconductor quantum-well wire. In particular, we investigate how these interactions affect the optical properties of the semiconductor quantum wire. We address this question in two parts: First, the band-gap renormalization (BGR) induced by self-energy corrections of electrons and holes is studied. A two subband model arising from the confinement of the quantum wire is developed to include the multisubband effects. The many-body theoretical formalism of electron (hole) self-energy is given within the GW approximation. We use the dielectric function both in full dynamical random-phase approximation, and in cjuasi-static approximation, in order to emphasize the dynamical properties of screening. The dependence of BGR on the e — h plasma density, temperature and wire width is studied. In the second part, the exciton renormalization induced by e — h plasma screening, and Goulomb correlation effects on the optical spectra of a quantum wire are considered. The optical properties are directly associated with the e — h two particle propogator, which obeys the Bethe-Salpeter equation. Based on recent studies, we review the solution of this equation with screened Coulomb interaction. In particular it is shown* that the dynamical treatment of screening produces an optical absorption/luminescence spectra which is consistent with experimental results. We present a discussion on the interplay of excitons and unbound carriers and on the reflection of this interplay to the optical spectra.