Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 85: Poster Session II
HL 85.112: Poster
Thursday, March 17, 2011, 18:00–21:00, P4
Asymmetric optical nuclear spin pumping in a single uncharged quantum dot — •Heike Schwager1, Florian Klotz2, Vase Jovanov2, Johannes Kierig2, Emily C. Clark2, Gerhard Abstreiter2, Martin Brandt2, Geza Giedke1, and Jonathan Finley2 — 1Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching — 2Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching
Highly asymmetric dynamic nuclear spin pumping is observed in a single self-assembled InGaAs quantum dot subject to resonant optical excitation of the neutral exciton transition. A large maximum polarization of 54% is observed and the effect is found to be much stronger upon pumping of the higher energy Zeeman level. Time-resolved measurements allow us to directly monitor the buildup of the nulcear spin polarization in real time and to quantitatively study the dynamics of the process. A strong dependence of the observed dynamic nuclear polarization on the applied magnetic field is found, with resonances in the pumping efficiency observed for particular magnetic fields. We develop a model that accounts for the observed behaviour, where the pumping of the nuclear spin system is due to hyperfine-mediated spin flip transitions between the states of the neutral exciton manifold.