Tunneling of zero-dimensional excitons in a single pair of correlated quantum dots

We have studied single pairs of self-assembled and strain-induced quantum dots by means of highly spatially resolved photoluminescence and photoluminescence excitation spectroscopy. A spectrally narrow resonance in the excitation spectrum of a single self-assembled quantum dot at the emission energy of the corresponding strain-induced quantum dot indicates an efficient interdot transfer of a single zero-dimensional exciton.