Termination-dependent surface in-gap states in a potential mixed-valent topological insulator: SmB6

We have investigated the surface states of a potential mixed-valent topological insulator SmB6 based on first-principles density functional theory slab band structure analysis. We have found that metallic surface states are formed in the bulk band gap region, providing evidence for the topological insulating nature of SmB6. The obtained surface in-gap states are quite different from those in existing reports in that they are formed differently depending on the Sm or B6 surface termination, and are composed of mainly the Sm 4f state indicating the essentiality of including f electrons in describing the surface states. We have obtained the spin chiral structures of the Fermi surfaces, which are also in accordance with the topological insulating nature of SmB6.