Spin polarization in valence-band photoemission from non-magnetic (001) surfaces

For light in a general state of polarization incident off-normally on (001) surfaces of non-magnetic cubic solids, the intensity and spin polarization of photo-electrons in normal emission are investigated. The radiation field inside the solid is approximated firstly by the external field and secondly according to Fresnel's formulae. Analytical expressions are derived to reveal the physical origin of individual spin-polarization components. They also clearly reveal differences between photoemission from surfaces and from single atoms. Quantitative results calculated by a relativistic one-step photoemission formalism are presented for Pt(001). The components of the photo-electron spin-polarization vector are strongly affected by metal optics. In addition to changes in sign and magnitude, components which are identically zero in the external-field approximation can become sizeable as a consequence of the optical response of the solid. Linearly polarized light with the electric field rotated by pi/4 out of the reaction plane induces spin-polarization components comparable to those arising from circularly polarized light.