Optical Transient-Grating Measurements of Spin Diffusion andRelaxation in a Two-Dimensional Electron Gas

Abstract

Spin diffusion in n-GaAs quantum wells, as measured by our optical transient-grating technique, is strongly suppressed relative to that of charge. Over a broad range of temperatures and dopings, the suppression of D s relative to D c agrees quantitatively with the prediction of "spin Coulomb drag" theory, which takes into account the exchange of spin in electron-electron collisions.Moreover, the spin-diffusion length, L s , is a nearly constant 1 µm over the same range of T and n, despite D s 's varying by nearly two orders of magnitude. This constancy supports the D'yakonov-Perel'-Kachorovskii model of spin relaxation through interrupted precessional dephasing in the spin-orbit field.