Transition metal-doped quantum dots: Optical detection and manipulation of spin states

The quantum-mechanical eigenvalue problem of an exciton (electron–hole pair) in interaction with a single paramagnetic ion in a II–VI semiconductor quantum dot (QD) is studied within the multiband effective mass formalism. Initially developed for spherical nanocrystals, the model is extended to cylindrical or lower symmetries, which concern ellipsoidal and/or wurtzite nanocrystals as well as self-assembled QDs. The zero-field splitting pattern of the exciton, arising from the confinement-enhanced sp–d exchange interactions, is studied as a function of the energy separating the light- and heavy-hole-like QD valence states. The energy and polarization characteristics of the components, promising for optical detection, are calculated. We also estimate the possibility of optical manipulation of the impurity spin by a circularly polarized laser pulse.