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HL: Halbleiterphysik

HL 35: II-VI semiconductors III

HL 35.1: Vortrag

Mittwoch, 29. März 2006, 14:30–14:45, POT 151

Optical orientation and thermal relaxation of excitons in semimagnetic CdMnSe/ZnSe quantum dots — •Thomas Schmidt¹, Michael Scheibner^1,2, Lukas Worschech¹, Alfred Forchel¹, Taras Slobodskyy³, and Laurens Molenkamp³ — ¹Technische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany — ²Naval Research Laboratories, Washington, DC 20375 USA — ³EP III, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

Polarization dynamics of quantum dots (QDs) represent actually an intensely studied field of research. Of special interest are semimagnetic quantum dots due to their distinct magnetic properties caused by the interaction of carrier spins with the Mn spin system. It is clear that with decreasing Mn content the semimagnetic properties are reduced. We have studied the polarization dynamics of a series of optical orientation and thermal relaxation of excitons in CdMnSe/ZnSe quantum dots for different Mn contents ranging from 0 to 2%. From the dependence of the polarization on the magnetic field strength we determined the exciton g factors of the QDs for different Mn contents and the relevant spin relaxation times. In particular, we have been able to resolve the sign reversal of the g factor. In QDs with negligible g factor the polarization properties are dominated by the optical orientation of the excited light. The spin relaxation times extracted from the thermal relaxation depend sensitively on the Mn concentration in a range of a few picoseconds.