Exchange-induced splitting of radiative exciton levels in a single quantumwire

We report on polarization-resolved micro-photoluminescence experiments perf ormed on a single GaAs/GaAlAs V-shaped quantum wire. At low temperature the micro-photoluminescence spectra are composed of sharp peaks corresponding to excitons localized in naturally formed quantum boxes. We observed splitt ings of the radiative doublet of these exciton levels into two linearly pol arized states due to the exchange interaction. The exchange splittings are of the order of 100 mu eV. A theoretical model of the exchange interaction on localized states in quantum wires is developed. It shows that the exchan ge splitting is characteristic of the uniaxial anisotropy of the localized states and thus related to their extension along the wire ;axis. The experi mental results are discussed within the frame of this model. (C) 2001 Elsev ier Science B.V. All rights reserved.