Magneto-photoluminescence and spin dynamics of self-assembled CdSe quantum dots in Zn1-xMnxSe

Abstract

We have studied photoluminescence spectra of CdSe self-assembled quantum dots (QD's) embedded in Zn1-xMnxSe (x = 0.05 and 0.15) with and without an external magnetic field. Under a magnetic field, the photoluminescence from CdSe QD's was circularly polarized under light excitation above the bandgap energy of ZnMnSe, indicating carrier spin polarization in CdSe QD's. The time-resolved photoluminescence study showed that spin-flip occured very rapidly as photocarriers transfered from the ZnMnSe to the CdSe QD's to reach statistical equilibrium of the spin states in the CdSe QD's. The Zeeman splitting in the CdSe QD's was several meV, still larger than the thermal energy at 5 K. These results suggest that the spin-polarization in CdSe QD's is mainly due to the Zeeman splitting of carriers in the CdSe quantum dots.