Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 44: Semiconductor Microcavities and Entangled States in Quantum Dots

HL 44.7: Invited Talk

Thursday, March 29, 2007, 17:15–17:45, H15

Configuration mixing of electronic states in quantum dots — Kroner M.¹, Govorov S.², Remi S.¹, Seidl S.¹, Badoleto A.⁴, Petroff P.⁴, Warburton R.³, and •Kahled Karrai¹ — ¹Center for NanoScience, Sektion Physik, Ludwig-Maximilians-Universität,Geschwister-Scholl-Platz 1, 80539 München, Germany — ²Department of Physics and Astronomy, Ohio University, Athens, OH, USA — ³Department of Physics, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK — ⁴Materials Department, University of California, Santa Barbara, CA 93106, USA

Charge tunable self-assembled semiconductor quantum dots are typically charac-terized by extremely sharp lines in their optical absorption and emission spectra. When the probing laser frequency is in resonance with one of such exciton lines, the quantum dot states can couple very strongly to the radiation field, to the point that the photon and electron states hybridize to become indistinguishable. A signature for such coherent dressed states formed under modest laser power is the observation of Rabi oscillations, of ac-stark effect and of cavity quantum electrodynamics in the weak and strong coupling regime. In this talk we present new data showing that when the laser power is further in-creased, a competing pathway for optical excitations in charge tunable quantum dots is revealed through a novel quantum optical interference. The interfering optical excitation channel originates from a weak transition of the charge tunable quantum dot ground state to an electronic continuum of states extended beyond the dot location. We will argue that this effect should apply generally to optically active few-level quantum systems in which one of the levels interacts with a continuum of states. The existence of alternative optical transition channels to localized and delocalized states has implications on coherence is-sues in quantum information processing. We developed a new quantum optical version of the ubiquitous Fano model that describes interactions between localized and extended dressed states. The model is in good qualitative agreement with the data.