Possibilities for exciton condensation in semiconductor quantum-well structures

Abstract

Recent progress in understanding the behavior of condensed excitonic systems is reviewed. The Bose-Einstein condensed excitonic insulator is studied numerically within the mean-field pairing approximation. In particular, we examine in some detail a system of spatially separated, two-dimensional (2D) electrons and holes, as a candidate system for study in semiconductor heterostructures. Based on these calculations, we suggest that it may be possible to create a droplet of high density exciton condensate fluid in semiconductor quantum-well structures. In heterostructures, the recombination of electrons and holes is dipole-allowed, which presents both difficulties and opportunities. The excitonic insulator state should be superradiant, which provides a direct measure of the coherence of the ground state. Additionally there is a gap between the absorption and emission spectrum, and collective modes lying within this quasiparticle gap. Coupling of the condensate to radiative modes of an optical cavity may offer an opportunity to manipulate the condensate and its optical response.