L-valley Electron Spin Dynamics in GaAs
  Optical orientation experiments have been performed in GaAs epilayers with photoexcitation energies in the 3 eV region yielding the photogeneration of spin-polarized electrons in the satellite L valley. We demonstrate that a significant fraction of the electron spin memory can be conserved when the electron is scattered from the L to the $\Gamma$ valley following an energy relaxation of several hundreds of meV. Combining these high energy photo-excitation experiments with time-resolved photoluminescence spectroscopy of $\Gamma$ valley spin-polarized photogenerated electrons allows us to deduce a typical L valley electron spin relaxation time of 200 fs, in agreement with theoretical calculations. 
T. Zhang, P. Barate, C.T. Nguyen, A. Balocchi, T. Amand, P. Renucci,   H. Carrere, B. Urbaszek, X. Marie
cond-mat.mes-hall cond-mat.mtrl-sci