Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 3: III-V-Compounds: GaAs and related Materials
HL 3.4: Talk
Monday, March 14, 2011, 11:00–11:15, POT 151
Hole spin initialization mechanisms in 2D hole systems at low temperatures — •Michael Kugler1, Stephan Furthmeier1, Tobias Korn1, Pawel Machnikowski2, Michael Griesbeck1, Marika Hirmer1, Dieter Schuh1, Werner Wegscheider3, and Christian Schüller1 — 1Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Germany — 2Institute of Physics, Wrocław University of Technology, Poland — 3Solid State Physics Laboratory, ETH Zurich, Switzerland
For the realization of scalable solid-state quantum-bit systems, spins in semiconductor quantum dots are promising candidates. A key requirement for quantum logic operations using holes is the generation of a resident hole spin polarization (RHSP).
Here, we report on two different mechanisms that lead to a RHSP of hole ensembles, confined in so-called natural quantum dots, in narrow GaAs/AlGaAs quantum wells at low temperatures after optical excitation. The first mechanism is driven by relaxation of the hole spins in the first few ps after excitation and leads to a RHSP pointing in the opposite direction than the optically generated hole spins after carrier recombination. It is enhanced by increased temperature, excitation density and excess carrier energy provided by detuning the laser from resonant excitation. The second mechanism is driven by applying a magnetic field and having hole and electron spins precess at different frequencies defined by their g-factors. This leads to a modified recombination behavior and therefore again to a RHSP. The interconnected electron and hole spin dynamics are well reproduced theoretically.