Spin-orbit influence on dz2-type surface state at Ta(110)

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 (sic) and exhibits a free-electron-like E(k(parallel to)) dispersion with an effective mass m*/m(e) of about -1.35 along (Gamma) over bar(H) over bar. Photoemission results for excitation with s- and p-polarized light confirm the predicted d(z2)-type symmetry of the state close to (Gamma) over bar. Spin-resolved data for finite k(parallel to) reveal a pure Rashba-type spin texture with a Rashba parameter of 0.063 +/- 0.007 eV A. These findings clearly prove a sizable impact of spin-orbit coupling on the d(z2) surface state and resolve a longstanding disagreement on this issue