# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 42: Topological insulators (organized by O)

### HL 42.8: Vortrag

### Dienstag, 1. April 2014, 12:15–12:30, GER 38

**The edge state at the dark side of the weak topological insulator Bi**_{14}**Rh**_{3}**I**_{9}** probed by STM** — •Christian Pauly^{1}, Bertold Rasche^{2}, Marcus Liebmann^{1}, Marco Pratzer^{1}, Klaus Koepernik^{3}, Manuel Richter^{3}, Michael Ruck^{2}, Jeroen van den Brink^{3}, and Markus Morgenstern^{1} — ^{1}II. Institute of Physics B, RWTH Aachen University and Jara Fit, Germany — ^{2}Departement of Chemistry and Food Chemistry, TU Dresden, Germany — ^{3}Institute for Theoretical Solid State Physics, IFW Dresden, Germany

Using scanning tunneling microscopy (STM) and spectroscopy (STS) at 6 K, we probe the local atomic and electronic structure of the weak topological insulator Bi_{14}Rh_{3}I_{9} [1]. In [001]-direction, the material is built from stacks of intermetallic planes with non-trivial 2D topology and spacer layers in between. Thus, the surfaces of the intermetallic planes, which are the natural cleaving planes of the material, exhibit a trivial band gap however with topologically protected states at each step edge [1]. Bi_{14}Rh_{3}I_{9} is cleaved at a base pressure of 10^{−10} mbar giving rise to several hundreds of nm large terraces of the intermetallic layer interrupted by step edges. Using STS, we identified the band gap on top of the intermetallic layer, which is in agreement with ARPES data, whereas at the step edges we directly mapped the edge state. The edge state appears continuously through the band gap and exhibits a spatial distribution of 0.4 nm FWHM. The observed spatial periodicity along the step edge is in line with the atomic structure confirming the Bloch type of this state. Partially, dispersive features appear which will be discussed. [1] B. Rasche et al., Nature Mater. 12, 422 (2013)