High temperature spin dephasing in n-typed GaAs quantum wells

We perform a many-body study of the spin dephasing due to the D'yakonov-Perel' effect in n-typed GaAs (100) quantum wells for high temperatures ($\geq 120$ K) under moderate magnetic fields in the Voigt configuration by constructing and numerically solving the kinetic Bloch equations. We include all the spin conserving scattering such as the electron-phonon, the electron-nonmagnetic impurity as well as the electron-electron Coulomb scattering in our theory and investigate how the spin dephasing rate is affected by the initial spin polarization, temperature, impurity, magnetic field as well as the electron density. The dephasing obtained from our theory contains not only that due to the effective spin-flip scattering first proposed by D'yakonov and Perel' [Zh. Eksp. Teor. Fiz. 60, 1954(1971)[Sov. Phys.-JETP {\bf 38}, 1053(1971)]], but also the recently proposed many-body dephasing due to the inhomogeneous broadening provided by the DP term [Wu, J. Supercond.:Incorp. Novel Mechanism {\bf 14}, 245 (2001); Wu and Ning, Eur. Phys. J. B {\bf 18}, 373 (2000)]. We show that for the electron densities we study, the spin dephasing rate is dominated by the many-body effect. Equally remarkable is that we are now able to investigate the spin dephasing with extra large spin polarization (up to 100 %) which has not been discussed both theoretically and experimentally. We find a dramatic decrease of the spin dephasing rate for large spin polarizations. The spin dephasing time (SDT), which is defined as the inverse of the spin dephasing rate, we get at low initial spin polarization is in agreement with the experiment both qualitatively and quantitatively.