  Temperature and carrier density dependent spin dynamics for GaAs/AlGaAs
quantum wells (QWs) with different structural symmetry has been studied by
using time-resolved Kerr rotation technique. The spin relaxation time is
measured to be much longer for the symmetrically-designed GaAs quantum well
comparing with the asymmetrical one, indicating the strong influence of Rashba
spin-orbit coupling on spin relaxation. D'yakonov-Perel' (DP) mechanism has
been revealed to be the dominant contribution for spin relaxation in
GaAs/AlGaAs QWs. The spin relaxation time exhibits non-monotonic dependent
behavior on both temperature and photo-excited carrier density, revealing the
important role of non-monotonic temperature and density dependence of
electron-electron Coulomb scattering. Our experimental observations demonstrate
good agreement with recently developed spin relaxation theory based on
microscopic kinetic spin Bloch equation approach.
