Effect of shape anisotropy in nanocrystals of semiconductors with small spin-orbit splitting.

We derive an effective spin-Hamiltonian accounting for the shape anisotropy of the zinc blende semiconductor nanocrystals within the k · p formalism explicitly taking into account the spin-orbit split-off valence band. It is shown that, for small InP nanocrystals, neglect of the spin-orbit split-off band can lead to significant underestimation of one of the two parameters determining the exciton fine-structure splittings. This parameter is only important for nanocrystals with shape anisotropy.