Quantum interference mapping of Rashba-split Bloch states in Bi/Ag(111).
We report on low-temperature scanning tunneling spectroscopy investigations of the (sqrt[3]×sqrt[3]) Bi/Ag(111)R30° surface alloy which provides a giant Rashba-type spin splitting. We observed spectroscopic features that are assigned to two Rashba-split bands. Quantum interference mapping shows that backscattering is not only allowed below but also above the Rashba energy. We argue that the observed behavior can be understood within the Bloch picture where k refers to the crystal momentum and the velocity of an electronic state is defined as v(n)(E) = 1/ℏ ∇(k)E(n)(k). The analysis of the energy dispersion of scattering channels reveals a conventional Rashba splitting for the unoccupied Rashba bands, while hybridization is observed in the occupied states.