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 applied field modifies the excitonic fine structure, depending on the quantum dot anisotropy direction (which is randomly oriented in this system). 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, for the anisotropy orientation, respectively, perpendicular or parallel to the field. 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.