Exchange Splitting of Zero-Dimensional Exciton Levels

Abstract

The zero-dimensional (OD) microstructures which are also known as quantum dot (QD) structures can be realized in practice in semiconductor nanocrystals embedded in glass matrices and in quantum wells with monolayer-high islands of well-width fluctuations. Optical properties of 0D systems have been widely studied in the last few years (see [1, 2] and references therein). The three-dimensional confinement in quantum dots leads to a discrete exciton-level structure. Taking into account only direct Coulomb interaction between an electron and a hole, the ground-state exciton energy level is degenerate due to the free-carrier spin degeneracy. This degeneracy is, however, removed partially or completely as a result of electron—hole exchange interaction which includes a longand a short-range contribution. In the present paper we analyze the long-range (or nonanalytic) contribution which is shown to play a crucial role in the interpretation of recent experiments.