Single Dirac cone on the Cs-covered topological insulator surface Sb2Te3(0001)

Using angle-resolved photoelectron spectroscopy we investigate the surface electronic structure of the three-dimensional topological insulator (TI) Sb2Te3(0001). Our data show the presence of a topological surface state in the bulk energy gap with the Dirac point located above the Fermi level. The adsorption of Cs atoms on Sb2Te3(0001) gives rise to a downward energy shift of the electronic valence band states which saturates at a value of similar to 200 meV. For the saturation coverage the Dirac point of the linearly dispersive surface state resides in close proximity to the Fermi level. The electronic structure of the Cs/Sb2Te3 interface therefore considerably deviates from previously studied metal-TI interfaces based on the isostructural compound Bi2Se3 which points to the importance of atomic composition in these hetero systems.