Determination of the actual valence band of a topological insulator Bi2Se3

A proper understanding of the electronic structure of topological insulators in terms of bulk states as well as surface spin polarized states is essential for the development of spintronic devices. In this work, we investigated the electronic structure of Bi2Se3, atypical n-type topological insulator. Experimentally, we measured the band dispersions along (Gamma) over bar-(M) over bar and the constant energy contours in the entire three-dimensional Brillouin zone, and confirmed that the valence band maximum is located at the Gamma point with a binding energy 65 +/- 15 meV higher than that of the Dirac point. The theoretical calculations performed by a quasi-particle self-consistent GW method show good agreement with the experimental results on the bulk band structure. The present results indicate that Bi2Se3 is a suitable candidate for next-generation spintronic devices.