Resonant inversion of the 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 inter-subband 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.