Surface electronic structure of Re(0001): A spin-resolved photoemission study

The surface electronic structure of Re(0001) has been investigated in a combined experimental and theoretical study. Spin-and angle-resolved photoemission was employed to unravel the spin-dependent E (k4) dispersion of electronic states along the F M and F K directions. The results are compared with band-structure calculations based on density-functional theory. Additional calculations include transitions into final states by taking into account the corresponding matrix elements. Recently, Shockley-and Tamm-type surface states close to EF were identified, which were found to be mixed by spin-orbit coupling. Here, we determined the Rashba parameter aR of the surface state around F to 0.32 and 0.34 eV A along F M and F K, respectively. Furthermore, we extend our analysis to a wider E (kii) range revealing a multitude of electronic states along both high-symmetry directions. In particular, Rashba-type spin splittings are observed around the high-symmetry F and M points. At variance with theoretical predictions for a perfect hcp(0001) surface, we do not find any out-of-plane spin polarization. This is caused by monatomic steps of a real Re(0001) surface with alternating terminations, leading on average to an effective sixfold surface symmetry and vanishing net out-of-plane spin polarization.