Influence of spin-orbit coupling on the momentum distribution of electron pairs emitted from Au on Ir(111)

We explore by theory and experiment the effects of spin–orbit coupling (SOC) on the pair creation of electrons by spin-polarized primary electrons incident on a pseudomorphic monolayer of Au on Ir(111). An ab-initio calculation of the electronic structure reveals a Rashba-type sp-like surface state in the Au layer, which turns out to lead to a large electron pair creation intensity. The distribution of this intensity over the momenta of the emitted electrons depends strongly on the primary electron spin due to spin–orbit coupling mainly in the incident and the outgoing electron states. For normal incidence, the six-fold rotation symmetry, which would hold without spin–orbit coupling, is broken in a manner depending on the orientation of the primary electron spin