Zusammenfassung
It is shown that a homogeneous spin polarization of electron gas drives an electric current in quantum well(QW) structures if some general symmetry requirements are met. Two effects, the spin-galvanic effect and the circular photogalvanic effect (CPGE), have been observed in n- and p-type QWs based on various semiconductor materials. These effects have in common, that the current flow is driven ...
Zusammenfassung
It is shown that a homogeneous spin polarization of electron gas drives an electric current in quantum well(QW) structures if some general symmetry requirements are met. Two effects, the spin-galvanic effect and the circular photogalvanic effect (CPGE), have been observed in n- and p-type QWs based on various semiconductor materials. These effects have in common, that the current flow is driven by an asymmetric distribution of carriers in k-space in gyrotropic systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. The spin-galvanic effect may be caused by any means of spin injection, while CPGE needs optical excitation with circularly polarized radiation. The spin-galvanic effect is due to asymmetric spin-flip scattering of spin polarized carriers and it is determined by the process of spin relaxation. The CPGE is the result of selective photoexcitation of carriers in k-space with circularly polarized light due to optical selection rules. In some optical experiments the photocurrent may represent a sum of both effects. Both effects provide methods to determine spin relaxation times.
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