Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 9: Poster I
HL 9.94: Poster
Montag, 27. März 2006, 15:15–17:45, P3
Acoustically induced spin transport in (110) GaAs quantum wells — •Odilon D. D. Couto1, Jörg Rudolph1, Yang Guang1, Fernando Iikawa2, Rudolf Hey1, Paulo V. Santos1, and Klaus H. Ploog1 — 1Paul-Drude-Institut, 10117 Berlin — 2Universidade Estadual de Campinas, Campinas, Brazil
GaAs quantum well (QW) structures grown along the [110] direction exhibit due to their symmetry much longer relaxation times for spins polarized along the growth direction than conventional (100) QWs. The electronic quality of the (110) structures, in contrast, is substantially lower than for (100) structures, as judged from the efficiency of the transport of carriers by surface acoustic waves (SAWs). In this contribution, we address this limitation for long-range spin transport by SAWs by (i) improving the sample growth process and (ii) increasing the intensity of the acoustic fields. The latter was achieved by coating the samples with a piezoelectric ZnO layer. The steady-state polarization of photogenerated spins increases substantially under a SAW due to the quenching of excitonic spin relaxation mechanisms as the electrons and holes are spatially separated by the piezoelectric field. Optically detected transport measurements under a magnetic field B in the sample plane and perpendicular to the SAW propagation direction show that the coherent transport length reduces from ls=30 µm for B=0 (corresponding to T2=ls/vSAW∼ 10 ns, where vSAW is the SAW velocity) to less than 10 µm for B=18 mT. Mechanisms for this drastic reduction in ls will be discussed.