Spectroscopic study of dark excitons in InxGa1-xAs self-assembled quantum dots by a magnetic-field-induced symmetry breaking

The dark states of the heavy-hole ground-state exciton have been studied by photoluminescence spectroscopy of single self-assembled In0.60Ga0.40As qua ntum dots in magnetic fields of varying strengths and orientations. When ti lting B out of the [001] crystal direction the exciton states with angular momenta \ m \ = 2 are mixed with the \ m \ = 1 states and become observable . In combination with a detailed analysis of the corresponding Hamiltonian a comprehensive picture of the exciton fine structure is obtained. This fin e structure is characteristic for direct gap semiconductors with a twofold degenerate valence band.