Stacked topological insulator built from bismuth-based graphene sheet analogues.

Rasche, Bertold; Isaeva, Anna; Ruck, Michael; Borisenko, Sergey; Zabolotnyy, Volodymyr; Büchner, Bernd; Koepernik, Klaus; Ortix, Carmine; Richter, Manuel; van den Brink, Jeroen

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.

TOPOLOGICAL insulators; BISMUTH; GRAPHENE; SPIN-orbit interactions; ELECTRONIC band structure; HONEYCOMB structures

Nature Materials, 2013, Vol 12, Issue 5, p422

1476-1122

Academic Journal

10.1038/nmat3570