Regensburg 2016 – scientific programme

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DS: Fachverband Dünne Schichten

DS 27: Symposium Topological Insulators: Status Quo and Future Directions
(Joint symposium of DS, HL, MA, O and TT, organized by TT)

DS 27.4: Invited Talk

Wednesday, March 9, 2016, 11:15–11:45, H1

Sub-nm wide edge states at the dark side of a weak topological insulator — •Markus Morgenstern — II. Institute of Physics B and JARA-FIT, RWTH Aachen, 52074 Aachen

Three-dimensional insulating crystals, which respect time reversal symmetry, can be classified as trivial insulators, strong topological insulators and weak topological insulators (WTIs). Many examples of trivial or strong topological insulators are known, but WTIs have barely been probed. They offer pairs of topologically protected surface states on most surfaces, but exhibit one dark surface without such surface states. The step edges of this dark surface naturally belong to the bright surfaces such that they contain spin helical edge states with perfect e²/h conductivity. The first WTI Bi₁₄Rh₃I₉ was synthesized recently [1]. Here, we show by scanning tunneling spectroscopy that the edge states indeed exist and are below 1 nm wide. They can be scratched into the surface using an atomic force microscope providing a simple tool to guide them [2]. Moreover, it is shown that the edge state can be removed by chemically dimerizing adjacent layers of the WTI. Strategies to bring the edge state to the Fermi level are discussed.
B. Rasche, A. Isaeva, M. Ruck, S. Borisenko, V. Zabolotnyy,

B. Büchner, K. Koepernik, C. Ortix, M. Richter,

and J. van den Brink, Nature Mater. 12, 422 (2012)
C. Pauly, B. Rasche, K. Koepernik, M. Liebmann, M. Pratzer,

M. Richter, J. Kellner, M. Eschbach, B. Kaufmann, L. Plucinski,

C. M. Schneider, M. Ruck, J. van den Brink, and M. Morgenstern,