### Session W10: Focus Session: Spin Transport and Spin Hall Effect

2:30 PM–5:18 PM, Thursday, March 24, 2005
LACC Room: 153B

Chair: Allan MacDonald, University of Texas

Abstract ID: BAPS.2005.MAR.W10.2

### Abstract: W10.00002 : Spin diffusion in GaAs quantum wells

3:06 PM–3:18 PM

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#### Authors:

C.P. Weber
N. Gedik
J.E. Moore
J. Orenstein
(UC Berkeley and LBNL)

J. Stephens
D.D. Awschalom
(UC Santa Barbara)

The diffusion coefficient of spin in semiconductors is often estimated using the Einstein relation,$D=\chi ^{-1}\mu$, relating diffusion and mobility. However, direct measurements of spin diffusion coefficient $D_{s}$ and the mobility \textit{$\mu$} in an n-GaAs quantum well sample with carrier density $n=7\times 10^{11}$cm$^{-2}$ have revealed that spin diffusion is substantially suppressed [1] relative to $\chi ^{-1}\mu$ because of the spin-Coulomb drag'' effect [2]. In this talk we present data that illustrate the behavior of D$_{s}$, \textit{$\mu$}, and the spin relaxation time as $n$ is lowered towards the metal to insulator transition. Spin transport is characterized by the transient spin grating technique [3], which is based on optical injection of an electron-spin polarization wave with variable wavevector. Spin relaxation is measured by polarization-resolved transient absorption and \textit{$\mu$} is obtained from 4-contact transport measurements. We discuss the evolution of spin Coulomb drag and D'yakanov-Perel spin relaxation from the degenerate to nondegenerate regimes. [1] J. Orenstein, APS invited talk, this session. [2] I. D'Amico and G. Vignale, Phys. Rev. B 62, 4853 (2000). [3] A.R. Cameron, et al., Phys. Rev. Lett., 4793 (1996).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.W10.2