Determination of the actual valence band of a topological insulator Bi[formula omitted]Se[formula omitted].

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 Bi 2 Se 3 , a typical n-type topological insulator. Experimentally, we measured the band dispersions along Γ ̄ - M ̄ and the constant energy contours in the entire three-dimensional Brillouin zone, and confirmed that the valence band maximum is located at the Γ 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 G W method show good agreement with the experimental results on the bulk band structure. The present results indicate that Bi 2 Se 3 is a suitable candidate for next-generation spintronic devices. • The bulk valence band maximum (VBM) of Bi 2 Se 3 is located at the Γ point. • The VBM is located at a binding energy higher than that of the Dirac point. • Quasi-particle self-consistent G W calculations support our experimental results. [ABSTRACT FROM AUTHOR]