Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 77: Quantum Dots and Wires: Optical Properties II (mainly Luminescence and Electronic Structure)

HL 77.2: Vortrag

Donnerstag, 29. März 2012, 09:45–10:00, EW 203

Geometry and electric field dependence of exciton fine structure in semiconductor quantum dots — •Erik Welander and Guido Burkard — Department of Physics, University of Konstanz, D-78457 Konstanz, Germany

We investigate theoretically the exciton fine structure splitting (FSS) in semiconductor quantum dots. The exciton, the bound state of an electron and a hole, plays the important role of the intermediate step in the biexciton cascade recombination, potentially a source of entangled photons. The two relevant states of the exciton, |X⟩ and |Y⟩, where X and Y correspond to polarization directions, are energetically split by the FSS. For the production of entangled photons it is essential that the FSS vanishes so that the intermediate exciton states are degenerate and the which-way information separated from frequency. Hence, a rigorous understanding of the exciton FSS is important for an accurate study of the light from a biexciton cascade recombination. Experiments have also shown a non-trivial dependence of the FSS on an external electric field. We develop a model incorporating the particle-antiparticle nature of the exciton system and find that the FSS depends on the QD geometry. Further, we investigate the effects of an external in-plane electric field, focusing on the possibility to eliminate the FSS completely.