Multivalley spin relaxation in the presence of high in-plane electric fields inn-type GaAs quantum wells

Abstract

Multivalley spin relaxation in $n$-type GaAs quantum wells with in-plane electric field is investigated at high temperature by means of kinetic spin Bloch equation approach. The spin-relaxation time first increases and then decreases with electric field, especially when the temperature is relatively low. We show that $L$ valleys play the role of a ``drain'' of the total spin polarization due to the large spin-orbit coupling in $L$ valleys and the strong $\ensuremath{\Gamma}\text{\ensuremath{-}}L$ intervalley scattering, and thus can enhance spin relaxation of the total system effectively when the in-plane electric field is high. Under electric field, spin precession resulting from the electric-field-induced magnetic field is observed. Meanwhile, due to the strong $\ensuremath{\Gamma}\text{\ensuremath{-}}L$ intervalley scattering as well as the strong inhomogeneous broadening in $L$ valleys, electron spins in $L$ valleys possess almost the same damping rate and precession frequency as those in $\ensuremath{\Gamma}$ valley. This feature still holds when a finite static magnetic field is applied in Voigt configuration, despite that the $g$ factor of $L$ valleys is much larger than that of $\ensuremath{\Gamma}$ valley. Moreover, it is shown that the property of spin precession of the whole system is dominated by electrons in $\ensuremath{\Gamma}$ valley. Temperature, magnetic field, and impurity can affect spin relaxation in low electric-field regime. However, they are shown to have marginal influence in high electric-field regime.