To Örebro University

The influence of spin-orbit interaction on an occupied surface state at Ta(110) is investigated with spin- and angle-resolved photoemission and electronic structure calculations. The surface state appears in a symmetry gap at a binding energy of 0.45 eV at Γ¯ and exhibits a free-electron-like E(k) dispersion with an effective mass m∗/me of about -1.35 along Γ¯H¯. Photoemission results for excitation with s- and p-polarized light confirm the predicted dz2-type symmetry of the state close to Γ¯. Spin-resolved data for finite k reveal a pure Rashba-type spin texture with a Rashba parameter of 0.063±0.007eVÅ. These findings clearly prove a sizable impact of spin-orbit coupling on the dz2 surface state and resolve a longstanding disagreement on this issue.