D'yakonov-Perel' spin relaxation under electron-electron collisions in QWs

The D'yakonov-Perel' mechanism of spin relaxation is connected with the spin splitting of the electron dispersion curve in crystals lacking a center of symmetry. In a two-dimensional noncentrosymmetric system, e.g. quantum well or heterojunction, the spin splitting is a linear function of ${\bm k}$, at least for small values of ${\bm k}$. We demonstrate that the spin relaxation time $\tau_s$ due to the spin splitting is controlled not only by momentum relaxation processes as widely accepted but also by electron-electron collisions which make no effect on the electron mobility. In order to calculate the time $\tau_s$ taking into account the electron-electron scattering we have solved the two-dimensional kinetic equation for the electron spin density matrix. We show how the theory can be extended to allow for degenerate distribution of the spin-polarized two-dimensional electron gas.