Fachgruppe Nanostrukturierte Materialien    

The authors have studied the circulary polarized photoluminescence of excitons confined in semimagnetic CdMnSe quantum dots (QDs) with nominal Mn concentrations of up to 2%. From the polarization, magnetic properties like exciton g-factors and spin relaxation times were studied. For sufficiently low doping of the QDs with Mn, it is possible to tune the exciton g-factor to zero, i.e., no Zeeman splitting occurs by applying a magnetic field. By light-controlled heating it was also observed that the QD polarization can be reduced, and even inverted. We relate this polarization inversion to the optical heating of the Mn system, which reduces the circular polarization of QD emission originating from Zeeman-split states below the initial polarization of laser-polarized electron-hole pairs.