Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 12: Quantenpunkte und -dr
ähte: Optische Eigenschaften II

HL 12.6: Talk

Friday, March 4, 2005, 16:15–16:30, TU P-N201

Direct Observation of Controlled Coupling in an Individual Quantum Dot Molecule — •Emily C. Clark, H. J. Krenner, M. Sabathil, A. F. Kress, D. Schuh, M. Bichler, G. Abstreiter, and J. J. Finley — Walter Schottky Institut and Physik Department, TU Muenchen, Am Coulombwall 3, D-85748 Garching, Germany

The realization of robust and scalable hardware for quantum information processing is one of the most challenging goals of solid-state physics. Excitons in semiconductor quantum dots (QDs) represent a particularly attractive quantum bit because they can be coherently manipulated using ultrafast laser pulses.

We report the direct spectroscopic observation of quantum coupling in individual quantum dot molecules (QDMs) and its manipulation using static electric fields. We performed photoluminescence spectroscopy on single pairs of stacked, self assembled InGaAs/GaAs QDMs which were embedded in a n-i Schottky junction. A clear anti-crossing of spatially direct (e,h in same QD) and indirect (e,h in different QDs) excitonic states is observed as the electric field along the QDM axis is tuned. At the anticrossing the electron component of the wavefunction hybridizes into bonding and antibonding states split by the tunnel coupling energy of 1.6 meV. Comparison with realistic calculations, which include strain, piezo-electric and Coulomb effects, indicate a wetting layer separation of 11.9 nm. This is in very good agreement with the nominal growth separation of 10 nm. See: cond-mat/0410206