Regensburg 2016 – scientific programme

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DS: Fachverband Dünne Schichten

DS 20: Topological Insulators: Status Quo and Future Directions
(Joint session of DS, O and TT, organized by DS)

DS 20.2: Talk

Tuesday, March 8, 2016, 12:45–13:00, H8

Quantum-well stabilized two-dimensional topological crystalline insulators — Chengwang Niu, Patrick Buhl, •Gustav Bihlmayer, Daniel Wortmann, Stefan Blügel, and Yuriy Mokrousov — Peter Grünberg Institut (PGI-1) & Institute for Advanced Simulation (IAS-1), Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

By means of density functional theory calculations, we find that monolayers of SnTe and PbTe can be characterized as two-dimensional topological crystalline insulators (2D-TCIs) with band gaps of 50 meV and 90 meV, respectively [1]. Embedded in NaCl or NaBr films, these 2D-TCIs are not only structurally stabilized, but also the band gaps can be enhanced up to 470 meV. Moreover, in these quantum-well structures the Madelung potential of the strongly ionic rocksalt lattice acting on the SnTe or PbTe layers enhances the band-inversion. Even in thicker, topologically trivial telluride films band-inversions can be induced that trigger a transition to a TCI state [2]. We further analyse the effect of an external magnetic (exchange) field on the SnTe and PbTe monolayers and find that the quantum anomalous Hall regime can be reached with fields exceeding 0.2 eV. This happens even for an in-plane oriented field where the mirror symmetry, protecting the TCI phase, is broken. We investigate the properties of the edge states for ribbons of different orientations using maximally localized Wannier functions.
Financial support of the DFG (SPP 1666) is gratefully acknowledged.
C. Niu et al., Phys. Rev. B. 91, 201401(R) (2015).
C. Niu et al., submitted (2015).