Efficiency of optical spin injection and spin loss from a diluted magnetic semiconductor ZnMnSe to CdSe nonmagnetic quantum dots

D. Dagnelund, I. A Buyanova, W. M. Chen, A. Murayama, T. Furuta, K. Hyomi, I. Souma, and Y. Oka

Phys. Rev. B 77, 035437 – Published 31 January 2008

Abstract

Magneto-optical spectroscopy in combination with tunable laser spectroscopy is employed to study optical spin injection from a diluted magnetic semiconductor (DMS) ZnMnSe into nonmagnetic CdSe quantum dots (QDs). Observation of a DMS feature in the excitation spectra of the QD photoluminescence polarization provides clear evidence for optical spin-injection from the DMS to the QDs. By means of a rate equation analysis, the injected spin polarization is deduced to be about 32% at $5 T$ , decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process including crossing the heterointerfaces and energy relaxation within the QDs.