Spin polarization of excitons in nonmagnetic quantum dots induced by a neighboring magnetic semiconductor quantum well

Magneto-photoluminescence (PL) experiments were carried out on double layer structures consisting of self-assembled nonmagnetic CdSe quantum dots (QDs) and a ZnCdMnSe diluted magnetic semiconductors quantum well (QW), separated by a thin ZnSe barrier layer. We observe two clearly defined PL peaks in all samples, corresponding to CdSe QD and ZnCdMnSe QW layers, respectively. The PL signal was detected using circular polarization. The degree of PL polarization from CdSe QDs in the double layer structures was much larger than that observed in single layers of nonmagnetic CdSe QD system. The effect was systematically studied by examining intensities, energy shifts, and polarizations of the PL peaks. We discuss the observed behavior in terms of antiparallel spin interaction between excitons localized in the nonmagnetic QDs and in the magnetic QWs.