title: Direct evidence for the dirac-cone topological surface states in the ternary chalcogenide TlBiSe₂.
abstract: We have performed angle-resolved photoemission spectroscopy on TlBiSe₂, which is a member of the ternary chalcogenides theoretically proposed as candidates for a new class of three-dimensional topological insulators. We found direct evidence for a nontrivial surface metallic state showing an "X"-shaped energy dispersion within the bulk-band gap. The present result unambiguously establishes that TlBiSe₂ is a strong topological insulator with a single Dirac cone at the Brillouin-zone center. The observed bulk-band gap of 0.35 eV is the largest among known topological insulators, making TlBiSe₂ the most promising material for studying room-temperature topological phenomena.
authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sato
authors.forename: Kouji
authors.initials: K
authors.lastname: Segawa
authors.forename: Hua
authors.initials: H
authors.lastname: Guo
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Sugawara
authors.forename: Seigo
authors.initials: S
authors.lastname: Souma
authors.forename: Takashi
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ando