Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 10: Spintronics II (joint session DS, HL, MA, TT, organized by HL)
TT 10.4: Talk
Monday, March 20, 2017, 15:30–15:45, POT 151
Anisotropy of the spin diffusion in GaAs-based two-dimensional electron gases — •Markus Schwemmer1, Andreas Hanninger1, Dieter Schuh1, Werner Wegscheider2, Tobias Korn1, and Christian Schüller1 — 1Institute of Experimental and Applied Physics, Faculty of Physics, University of Regensburg, Germany — 2ETH Zurich, Switzerland
The combination of a femtosecond pulsed TiSa-Laser system with a magneto-optical Kerr effect microscope setup allows us to study time- and space-resolved propagation of an optically injected electron spin packet in a two-dimensional electron system (2DES) based on a modulation-doped AlGaAs/GaAs quantum well. The electron spin dynamics, and thus the electron spin diffusion, is determined by the interplay between Dresselhaus and Rashba fields. The geometry of the Dresselhaus field, which arises due to the bulk inversion asymmetry, is mostly determined by the growth direction of the quantum well. The Rashba field instead is caused by a structure inversion asymmetry, which can be controlled, e.g. by the modulation doping. For the specific case of a symmetrically modulation-doped, (110)-grown GaAs quantum well, optically injected electron spins align parallel or antiparallel to the spin-orbit field. Therefore, D'yakonov-Perel spin dephasing is suppressed and a long spin coherence time can be attained. For such a system one would expect naively isotropic electron spin diffusion in the quantum well plane. Nevertheless a strongly direction-dependent behaviour of the electron spin diffusion is observed.