Rashba Splitting Of The Tamm Surface State On Re(0001) Observed By Spin-Resolved Photoemission And Scanning Tunneling Spectroscopy

Using spin-resolved time-of-flight momentum microscopy, the Rashba splitting of the Tamm surface state is investigated. This state resides at the Fermi level in a projected bulk band gap of the close-packed (0001) surface of hcp Re. The Rashba splitting amounts to 0.4 angstrom(-1). The state with smaller parallel momentum is fully separated from bulk states, whereas the Rashba branch with larger momentum hybridizes with bulk states, which leads to a suppression of spin-momentum locking. We find a good agreement of the experimental results with one step photoemission calculations that are based on ab initio theory within the local density approximation. The spin polarization of the inner Rashba state is not complete, which manifests in the occurrence of quantum interference patterns as observed by scanning tunneling microscopy. A one-to-one agreement of scanning tunneling spectroscopy and photoemission results is observed, suggesting that the quantum interference pattern originates from the inner Rashba state.