Photogalvanic effects due to quantum interference in optical transitions   demonstrated by terahertz radiation absorption in Si-MOSFETs
  We report on the observation of the circular (helicity-dependent) and linear photogalvanic effects in Si-MOSFETs with inversion channels. The developed microscopic theory demonstrates that the circular photogalvanic effect in Si structures it is of pure orbital nature originating from the quantum interference of different pathways contributing to the light absorption. 
P. Olbrich, S.A. Tarasenko, C. Reitmaier, J. Karch, D. Plohmann, Z.D.   Kvon, and S.D. Ganichev