Spin and exchange effects in CdSe/ZnSe quantum dots probed by single-dot spectroscopy

The influence of exchange interaction on the eigenstate symmetry in a variety o CdSe/ZnSe single quantum dots is studied by photoluminescence spectroscopy. The lifting of spin degeneracy of the optically allowed exciton states results in a linearly polarized doublet of both the single exciton and the biexciton transitions, with an energy splitting reflecting the symmetry of the dots. Comparing different single dots, we found that most of the dots are almost symmetric, i.e. have an energy splitting < 0.2 meV, while strongly asymmetric dots (i.e. a symmetry lower than D 2d ) with energy splittings up to about 1 meV are predominantly oriented along the [110] and [110] axes of the crystal.

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