Relation between spin–orbit induced spin polarization, Fano-effect and circular dichroism in soft x-ray photoemission

Abstract

A Feynman diagram analysis of photoemission probabilities suggests a relation between two final-state spin polarization effects, the optical spin-orientation originating from the interaction with circularly polarized light (, Fano effect) and the spin polarization induced by the spin–orbit scattering (, Mott effect). The analysis predicts that is proportional to the product of and the circular dichroism in the angular distribution (CDAD) of photoelectrons. To confirm this prediction, the spin polarization of photoelectrons excited by soft x-ray radiation from initial spin-degenerate bulk states of tungsten using time-of-flight momentum microscopy with parallel spin detection has been measured. By measurement of four independent photoemission intensities for two opposite spin directions and opposite photon helicity, CDAD, Fano, and Mott effect are distinguished. The results confirm the prediction from the Feynman diagram analysis.