Manipulating the exciton fine structure of single CdTe/ZnTe quantum dots by an in-plane magnetic field

Polarization resolved photoluminescence (PL) spectroscopy of individual CdTe/ZnTe quantum dots is investigated in the presence of external in-plane magnetic field. We find that the excitonic fine structure strongly depends on the magnitude and direction of applied field. The splitting between "bright" and "dark" states increases with the magnetic field, whereas the anisotropic exchange splitting of the bright excitons can be reduced or enhanced, depending on the field direction. Increase (decrease) is observed when the field is applied parallel to the PL polarization direction of the lower (upper) energy exciton. For intermediate fields, we observe a rotation of the PL polarization orientation. The results are discussed in terms of an effective spin Hamiltonian derived for the exciton ground state.