Relativistic effects on the surface electronic structure of Mo(011)

High-resolution photoemission studies of the Mo(011) surface have allowed us to isolate and to study the effects of the spin-orbit interaction on the surface electronic structure of Mo(011). We have observed and characterized three distinct phenomena, all related to the breaking of symmetry by the spin-orbit interaction. The first is a zone-center surface resonance which exists in a pseudogap between the bulk 8+ and the 7+ points, and is similar to one observed previously on W(011). We also have observed a surface state in a projected band gap opened by spin-orbit-induced hybridization between bulk bands at N. Finally, we have observed avoided crossings of surface bands along the symmetry azimuths. These bands would be of opposite mirror-plane symmetry in the absence of the spin-orbit interaction, but hybridize under its influence. The transfer of both the polarization behavior and contamination sensitivity from one band to another is observed and characterized. We speculate on the relevance of these results to other surface properties, including reconstruction and work-function change.