Surface electronic structure of SmB6(111)

Samarium hexaboride (SmB₆) is the most extensively studied candidate of topological Kondo insulators. To clarify the topological origin of metallic surface states observed on the SmB₆(001) surfaces, we studied the surface electronic structure of SmB₆ on the other surface orientation, SmB₆(111). Although the SmB₆(111) surface cannot be obtained by cleaving, we successfully obtained the well-defined clean surface by high-temperature annealing of the mechanically polished single crystal of SmB₆(111) in an ultra-high vacuum. The valence band spectra obtained by photoelectron spectroscopy with the bulk and surface-sensitive incident photon energies imply that the surface is covered with $B_6$ cluster without Sm atoms.