title: Stacked topological insulator built from bismuth-based graphene sheet analogues.
abstract: Commonly, materials are classified as either electrical conductors or insulators. The theoretical discovery of topological insulators has fundamentally challenged this dichotomy. In a topological insulator, the spin-orbit interaction generates a non-trivial topology of the electronic band structure dictating that its bulk is perfectly insulating, whereas its surface is fully conducting. The first topological insulator candidate material put forward--graphene--is of limited practical use because its weak spin-orbit interactions produce a bandgap of ~0.01 K. Recent reexaminations of Bi2Se3 and Bi2Te3, however, have firmly categorized these materials as strong three-dimensional topological insulators. We have synthesized the first bulk material belonging to an entirely different, weak, topological class, built from stacks of two-dimensional topological insulators: Bi14Rh3I9. Its Bi-Rh sheets are graphene analogues, but with a honeycomb net composed of RhBi8 cubes rather than carbon atoms. The strong bismuth-related spin-orbit interaction renders each graphene-like layer a topological insulator with a 2,400 K bandgap.
authors.affiliation: Department of Chemistry and Food Chemistry, TU Dresden, D-01062 Dresden, Germany.
authors.forename: Bertold
authors.initials: B
authors.lastname: Rasche
authors.forename: Anna
authors.initials: A
authors.lastname: Isaeva
authors.forename: Michael
authors.initials: M
authors.lastname: Ruck
authors.forename: Sergey
authors.initials: S
authors.lastname: Borisenko
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Zabolotnyy
authors.forename: Bernd
authors.initials: B
authors.lastname: Büchner
authors.forename: Klaus
authors.initials: K
authors.lastname: Koepernik
authors.forename: Carmine
authors.initials: C
authors.lastname: Ortix
authors.forename: Manuel
authors.initials: M
authors.lastname: Richter
authors.forename: Jeroen
authors.initials: J
authors.lastname: van den Brink