Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 63: Topology: Quantum Hall Systems

TT 63.4: Vortrag

Mittwoch, 14. März 2018, 15:45–16:00, A 053

Protected pseudohelical edge states in Z₂-trivial proximitized graphene — •Tobias Frank, Petra Högl, Martin Gmitra, Denis Kochan, and Jaroslav Fabian — Universität Regensburg

We investigate topological properties of models that describe graphene on realistic substrates which induce proximity spin-orbit coupling in graphene [1]. A Z2 phase diagram is calculated for the parameter space of (generally different) intrinsic spin-orbit coupling on the two graphene sublattices, in the presence of Rashba coupling. The most fascinating case is that of staggered intrinsic spin-orbit coupling which, despite being topologically trivial, Z₂=0, does exhibit edge states protected against time-reversal scattering for zigzag ribbons as wide as micrometers. We call these states pseudohelical as their helicity is locked to the sublattice. The spin character and robustness of the pseudohelical modes is best exhibited on a finite flake, which shows a finite spin current in the crossection of the flake, and exhibit spin-flip reflectionless tunneling at the armchair edges.

This work was supported by the DFG SFB Grant No. 689, 1277 (A09 and B07) and GRK Grant No. 1570, and the International Doctorate Program Topological Insulators of the Elite Network of Bavaria. We received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 696656. The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for funding this project.
M. Gmitra, D. Kochan, P. Högl, J. Fabian, PRB 93 155104 (2016)