Spin-polarized surface states on Br/Ge(111)-(1x1): Surface spin polarization without heavy elements

We have investigated the atomic and electronic structure of the Br/Ge(111)-(1x1) surface. A couple of surface bands were found near the bulk valence band maximum by angle-resolved photoelectron spectroscopy (ARPES). Spin-resolved ARPES (SARPES) experiments showed that these surface bands are spin polarized. The results of the first-principles calculation based on the atomic structure determined by low-energy electron diffraction are in good agreement with the ARPES and SARPES results. The present result clearly shows that the significant spin polarization of the surface electronic states due to the Rashba spin-orbit interaction can be obtained without heavy elements belonging to the fifth or higher rows of the periodic table.