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O: Fachverband Oberflächenphysik

O 122: Topology and Symmetry Protected Materials II

O 122.1: Vortrag

Freitag, 20. März 2020, 10:30–10:45, WIL A317

Coupling of topologically protected edge states on the TCI (Pb,Sn)Se(001) — •Johannes Jung, Robin Boshuis, Artem Odobesko, and Matthias Bode — Physikalisches Institut, Lehrstuhl für Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany

In a recent publication [1] we reported on the existence of one-dimensional (1D) edge states at odd step edges of the (001) surface of the topological crystalline insulator (Pb,Sn)Se, which were found to be extraordinarily robust against high temperatures and magnetic fields. It was also observed, that the edge states vanish if two steps merge into each other. In this contribution we present a systematic STM and STS study of converging, wedge-shaped step edges. Our results elucidate a distance-dependent coupling between adjacent 1D edge states. Three regimes with qualitatively different electronic structures are found: (i) At step–step distances larger than about 20 nm the tunneling spectrum of either step features a single peak at the Dirac point, which—within our signal-to-noise level—is indistinguishable from individual 1D edge state. In contrast, (ii) wherever the inter-step distance decreases below this value, we observe a splitting into a double peak. (iii) As the distance decreases below a critical limit of about 5 to 10 nm, the double peak vanishes and the 2D surface spectra remains. The results will be discussed in terms of the crystal structure and the symmetry at odd step edges.
[1] P. Sessi et al., Science 354, 1269 (2016).