Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 4: Transport: Quantum Dots, Wires, Point Contacts 1 (jointly with HL and TT)

O 4.9: Vortrag

Montag, 11. März 2013, 11:45–12:00, H20

Spindephasing and Coherent Control of an Ensemble of Quantum Dots — •Andre Jovchev and Frithjof B. Anders — Technische Universität Dortmund, Lehrstuhl für Theoretische Physik II, 44221 Dortmund, Germany

We present a numerical treatment of pump-and-probe experiments with an ensemble of singly charged quantum dots in a magnetic field. We examine the excitation of trions, which is part of an effective polarization mechanism for the spin of the residual electrons, precessing around the magnetic field vector. Inhomogeneities in the magnetic g-factor of different electrons lead to dephasing. The effect of the short pump pulses is described by a unitary operator in the subspace of a spin degenerated electron and trion. For the dynamics between the pulses we apply a Lindblad theory to describe the decoherence due to environmental effects and the hyperfine interaction of the electrons with surrounding nuclei. We study the polarization of the whole ensemble after the application of different pulse protocols, and give an explanation for the polarization of the nuclear spins, which can lead to a remarkably increase of dephasing times which were already seen in experiments.