Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 90: Low-dimensional systems: Topological order (organized by TT)

HL 90.1: Talk

Thursday, April 3, 2014, 09:30–09:45, HSZ 204

Silicene and germanene as topological insulators: ab-initio approach — •Lars Matthes and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

Silicene is a two-dimensional honeycomb lattice formed by silicon atoms and shares many properties of graphene, e.g. massless Dirac electrons at the Fermi level. In silicene the effect of spin-orbit interaction (SOI) is enhanced due to its buckled structure. Furthermore, by means of tight-binding calculations including SOI the emergence of topologically protected edge states has been predicted in silicene (and also germanene) nanoribbons [1] for zigzag and armchair edges, turning these crystals into topological insulators.

In this talk we study, whether or not silicene and germanene are topological insulators in a real simulation. We employ density-functional theory for the simulation of germanene nanoribbons. The band structures of ribbons of several widths as well as zigzag and armchair edges with hydrogen passivation are presented. The presence of topologically protected states is discussed versus edge shape, edge magnetization, ribbon width, and strength of spin-orbit interaction. The validity of results of the tight-binding model is critically discussed.
M. Ezawa and N. Nagaosa, Phys. Rev. B 88, 121401(R) (2013)