Spin coherence in a two-dimensional electron gas with Rashba spin-orbit interaction

We study spin-relaxation phenomena in a two-dimensional electron gas in the presence of Rashba spin-orbit coupling. A tight-binding model including Rashba spin-orbit coupling is used to study spin relaxation and spin diffusion in a two-dimensional electron gas within Landauer-B\"uttiker formalism. It is shown that the spin-diffusion length is not independent of the mean free path as predicted by the motional narrowing effect. Further it is demonstrated that spin relaxation is anisotropic and can show a nonmonotonic dependence on Fermi energy due to nonparabolicity of the band.