Fine structure in the excitonic emission of InAs/ GaAs quantum dot molecules

The exciton fine structure in self-assembled coupled quantum dots with barriers of varying widths is studied in detail. For narrow barriers we find doublet splittings of the molecule ground state exciton in magnetic field, while for wide barriers in some cases a multiplet of emission lines is observed. Pronounced anticrossings occur in the field dispersion of such a multiplet with details depending on the particular molecule geometry. Strong variations of the fine structure including avoided crossings are observed also for the excited states that arise from the coupling-induced splitting of the quantum dot s-shell excitons. Values for the exciton diamagnetic shifts and spin splittings as functions of barrier width are given.

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