Biexciton spin and angular momentum transitions in vertically coupled quantum dots

Abstract

An "exact" numerical calculation is presented for the energy spectrum of biexcitons, with spatially separated electrons and holes, in coupled quantum dots in the presence of a perpendicular magnetic field. When the interdot distance is small the two electrons and two holes form a strongly correlated complex whose spin state undergoes characteristic transitions with increasing interdot separation and magnetic field. For the smallest distances and magnetic fields the biexciton is bound with respect to dissociation into two excitons. At larger distances we observe angular momentum transitions with sawtooth-shaped phase boundaries. The biexciton diamagnetic shift shows a sign reversal as a function of the interdot distance. ©2005 The American Physical Society.