Detection of large magnetoanisotropy of electron spin dephasing in a high-mobility two-dimensional electron system in a [001] GaAs/AlxGa1−xAs quantum well

In time-resolved Faraday rotation experiments, we have detected an in-plane anisotropy of the electron spin-dephasing time SDT in an n-modulation-doped GaAs/Al0.3Ga0.7As single quantum well. The SDT was measured with magnetic fields of B1 T, applied in the 110 and 11¯0 in-plane crystal directions of the GaAs quantum well. For fields along 11¯0, we have found up to a factor of about 2 larger SDT than in the perpendicular direction. The observed SDTs also show strong anisotropic magnetic-field dependence. Fully microscopic calculations, by numerically solving the kinetic spin Bloch equations considering the Dyakonov- Perel and the Bir-Aronov-Pikus mechanisms, reproduce the experimental findings quantitatively. This quantitative analysis of the data allowed us to determine the relative strengths of Rashba and Dresselhaus terms in our sample. Moreover, we could predict the SDT for spins aligned in the 110 in-plane direction to be on the order of several nanoseconds, which is up to 2 orders of magnitude larger than that in the perpendicular in-plane direction