Confinement-induced enhancement of spin interactions in Mn-doped II-VI semiconductor nanocrystals

The effects of sp - d exchange interactions on the optical properties of quantum dots containing a single Mn ion are investigated within the effective mass formalism. The quantum-mechanical eigenvalue problem of an electron-hole pair in interaction with the Mn spin is solved analytically. In zinc-blende semiconductors such as CdTe the fundamental absorption line splits into six components, whose relative intensities strongly depend on the Mn spin orientation with respect to the polarization of light, suggesting the possibility of optical detection of spin. In a magnetic field the splitting between the strong components of the or and sigma(+) spectra rapidly attains a saturation value close to the overall zero-field splitting, which is inversely proportional to the nanocrystal volume. Typically, it is an order of magnitude larger than the saturation Zeeman splitting in the corresponding bulk diluted magnetic semiconductor. The numerical results for ZnSe:Mn nanocrystals show a good agreement with the published experimental data. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.