Effect of Initial Spin Polarization on Spin Dephasing and the ElectrongFactor in a High-Mobility Two-Dimensional Electron System

Abstract

We have investigated the spin dynamics of a high-mobility two-dimensional electron system (2DES) in a $\mathrm{GaAs}\mathrm{\text{\ensuremath{-}}}{\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ single quantum well by time-resolved Faraday rotation in dependence on the initial degree of spin polarization, $P$, of the 2DES. From $P\ensuremath{\sim}0$ to $P\ensuremath{\sim}30%$, we observe an increase of the spin dephasing time, ${T}_{2}^{*}$, by an order of magnitude, from about 20 ps to 200 ps, in good agreement with theoretical predictions by Weng and Wu [Phys. Rev. B 68, 075312 (2003)]. Furthermore, also the electron $g$ factor is found to decrease for increasing $P$. Fully microscopic calculations reproduce the most salient features of the experiments, i.e., a dramatic decrease of spin dephasing and a moderate decrease of the electron $g$ factor with increasing $P$. We show that both results are determined dominantly by the Hartree-Fock contribution of the Coulomb interaction.