Direct observation of acoustic phonon mediated relaxation between coupled exciton states in a single quantum dot molecule

Nakaoka, T.; Krenner, H. J.; Clark, E. C.; Sabathil, M.; Bichler, M.; Arakawa, Y.; Abstreiter, G.; Finley, J. J.

Direct observation of acoustic phonon mediated relaxation between coupled exciton states in a single quantum dot molecule

Authors

Description

We probe acoustic phonon mediated relaxation between tunnel coupled exciton states in an individual quantum dot molecule in which the inter-dot quantum coupling and energy separation between exciton states is continuously tuned using static electric field. Time resolved and temperature dependent optical spectroscopy are used to probe inter-level relaxation around the point of maximum coupling. The radiative lifetimes of the coupled excitonic states can be tuned from ~2 ns to ~10 ns as the spatially direct and indirect character of the wavefunction is varied by detuning from resonance. Acoustic phonon mediated inter-level relaxation is shown to proceed over timescales comparable to the direct exciton radiative lifetime, indicative of a relaxation bottleneck for level spacings in the range $ΔE\$ ~3-6 meV.
6 pages, 4 figures, submitted for publication