Nonlinear spin Hall effect in GaAs (110) quantum wells
  We consider stationary spin current in a (110)-oriented GaAs-based symmetric quantum well due to a nonlinear response to an external periodic electric field. The model assumed includes the Dresselhaus spin-orbit interaction and the random Rashba spin-orbit coupling. The Dresselhaus term is uniform in the quantum well plane and gives rise to spin splitting of the electron band. The external electric field of frequency $\omega$ - in the presence of random Rashba coupling -- leads to virtual spin-flip transitions between spin subbands, generating stationary pure spin current proportional to the square of the field amplitude. 
V. I. Ivanov, V. K. Dugaev, E. Ya. Sherman, and J. Barnas
cond-mat.mtrl-sci