Spin photocurrents in quantum wells

Prof.dr. S.D. Ganichev
Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg

A new property of the electron spin in a spin-polarized electron gas is investigated. It is shown that a non-equilibrium spin polarization of electrons in a quantum well is inevitably linked with an electric current in the well if some general symmetry requirements are met. Two microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a QW: the spin polarization induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asymmetric distribution of spin polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate the spin-splitting of the band structure and to make a conclusion on the in-plane symmetry of QWs.