Spectroscopic signature of shape anisotropy in single CdSe nanocrystals

We study single zinc blende CdSe nanocrystals for the high symmetry of their cubic structure, which makes them very sensitive to deformations around the spherical shape. We have developed a photoluminescence excitation technique (PLE) to probe the whole band edge exciton fine structure. We observe both split 1L and 1U states, which we attribute to shape anisotropy. The polarizations of the doublets are anticorrelated and the splittings are comparable, as predicted by the valence band mixing model.