Spin dephasing in n-type GaAs quantum wells -: art. no. 075312

We perform a many-body study of the spin dephasing due to the D'yakonov-Perel' effect in n-type GaAs (100) quantum wells for high temperatures (greater than or equal to120 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 and electron-nonmagnetic impurities 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, and magnetic field as well as 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 38, 1053 (1971)]), but also the recently proposed many-body dephasing due to the inhomogeneous broadening provided by the DP term [M. W. Wu, J. Supercond.: Incorp. Novel Mechanism 14, 245 (2001); M. W. Wu and C. Z. Ning, Eur. Phys. J. B 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, 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.