Transfer of spin orientation into electric current in quantum wells

A monopolar spin polarization has been achieved in quantum well structures applying terahertz circularly polarized radiation. The spin polarization results in a directed motion of free carriers in the plane of a quantum well perpendicularly to the direction of light propagation. Due to spin selection rules the direction of the current is determined by the helicity of the light and can be reversed by switching the helicity from right- to left handed.