Coulomb mediated hybridization of excitons in coupled quantum dots

P. -L. Ardelt, K. Gawarecki, K. Müller, A. M. Waeber, A. Bechtold, K. Oberhofer, J. M. Daniels, F. Klotz, M. Bichler, T. Kuhn, H. J. Krenner, P. Machnikowski, J. J. Finley

Physical Review Letters 116, 077401 (2016) DOI: Physical Review Letters

We report Coulomb mediated hybridization of excitonic states in optically active InGaAs quantum dot molecules. By probing the optical response of an individual quantum dot molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic 8-band k·p calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial semiconductor molecule.