Bulk band structure of Sb2Te3 determined by angle-resolved photoemission spectroscopy

The bulk band structure of the topological insulator Sb-2 Te-3 is investigated by angle-resolved photoemission spectroscopy. Of particular interest is the dispersion of the uppermost valence band with respect to the topological surface state Dirac point. The valence band maximum has been calculated to be either near the Brillouin zone centre or in a low-symmetry position in the (Gamma) over bar-(M) over bar azimuthal direction. In order to observe the full energy range of the valence band, the strongly p-doped crystals are counter-doped by surface alkali adsorption. The data show that the absolute valence band maximum is likely to be found at the bulk Gamma point and predictions of a low-symmetry position with an energy higher than the surface Dirac point can be ruled out.