Resonant inversion of circular photogalvanic effect in n-doped quantum wells,

We show that the sign of the circular photogalvanic effect can be changed by tuning the radiation frequency of circularly polarized light. Here resonant inversion of the photogalvanic effect has been observed for direct intersubband transition in n-type GaAs quantum well structures. This inversion of the photon helicity driven current is a direct consequence of the lifting of the spin degeneracy due to k-linear terms in the Hamiltonian in combination with energy and momentum conservation and optical selection rules

Spin galvanic effect due to optical spin orientation in n-type GaAs quantum well structures

Under oblique incidence of circularly polarized infrared radiation the spin-galvanic effect ~SGE! has been unambiguously observed in ~001!-grown n-type GaAs quantum well structures in the absence of any external magnetic field. Resonant intersubband transitions have been obtained making use of the tunability of the free-electron laser FELIX. A microscopic theory of the SGE for intersubband transitions has been developed, which is in good agreement with experimental findings