title: Electronic Structure of the Dark Surface of the Weak Topological Insulator Bi14Rh3I9.
abstract: Compound Bi14Rh3I9 consists of ionic stacks of intermetallic [(Bi4Rh)3I](2+) and insulating [Bi2I8](2-) layers and has been identified to be a weak topological insulator. Scanning tunneling microscopy revealed the robust edge states at all step edges of the cationic layer as a topological fingerprint. However, these edge states are found 0.25 eV below the Fermi level, which is an obstacle for transport experiments. Here, we address this obstacle by comparing results of density functional slab calculations with scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. We show that the n-type doping of the intermetallic layer is intrinsically caused by the polar surface and is well-screened toward the bulk. In contrast, the anionic "spacer" layer shows a gap at the Fermi level, both on the surface and in the bulk; that is, it is not surface-doped due to iodine desorption. The well-screened surface dipole implies that a buried edge state, probably already below a single spacer layer, is located at the Fermi level. Consequently, a multilayer step covered by a spacer layer could provide access to the transport properties of the topological edge states. In addition, we find a lateral electronic modulation of the topologically nontrivial surface layer, which is traced back to the coupling with the underlying zigzag chain structure of the spacer layer.
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , D-52074 Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Pauly
authors.affiliation: Department of Chemistry and Food Chemistry, TU Dresden , D-01062 Dresden, Germany.
authors.forename: Bertold
authors.initials: B
authors.lastname: Rasche
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden e.V. , P.O. Box 270116, D-01171 Dresden, Germany.|Dresden Center for Computational Materials Science (DCMS), TU Dresden , D-01069 Dresden, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Koepernik
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden e.V. , P.O. Box 270116, D-01171 Dresden, Germany.|Dresden Center for Computational Materials Science (DCMS), TU Dresden , D-01069 Dresden, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Richter
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden e.V. , P.O. Box 270116, D-01171 Dresden, Germany.
authors.forename: Sergey
authors.initials: S
authors.lastname: Borisenko
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , D-52074 Aachen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Liebmann
authors.affiliation: Department of Chemistry and Food Chemistry, TU Dresden , D-01062 Dresden, Germany.|Max Planck Institute for Chemical Physics of Solids , D-01187 Dresden, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Ruck
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW Dresden e.V. , P.O. Box 270116, D-01171 Dresden, Germany.|Dresden Center for Computational Materials Science (DCMS), TU Dresden , D-01069 Dresden, Germany.
authors.forename: Jeroen
authors.initials: J
authors.lastname: van den Brink
authors.affiliation: II. Institute of Physics B and JARA-FIT, RWTH Aachen University , D-52074 Aachen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Morgenstern
keywords: density functional theory calculation; scanning tunneling spectroscopy; topological insulators