SFB 1170


    Electron spectroscopy of topological insulators: elemental and hybrid systems


    At the heart of this project are tailor-made epitaxial topological insulators (TIs), which allow access to fundamental modifications by lattice strain, impurities as well as interfaces of interacting nature. The project is in part based on α-Sn, for which we developed the in situ growth, and will comprise magnetic atoms to break time-reversal symmetry (TRS). Studies will include hybrid structures with interfaces, where charge transfer, magnetic interactions and superconductivity can create unusual topological situations. An important variant is a decreased Sn film thickness, which will evoke 1D edge states relevant for quantum spin Hall physics. A completely new thrust is epitaxial fabrication of graphene-like honeycomb monolayers of high-Z atoms, where Sn and Bi on various substrates are promising candidates. The aim is to provide 2D honeycomb TI materials with a large energy gap suitable for spin transport applications. A rather different approach to topological physics is taken via Topological Crystalline Insulators (TCI), represented by the Pb1-xSnxTe material class, fabricated within the SFB with varied Sn content and strain. They allow to explore the phase boundary between trivial and topological phases, as well as the selective breaking of Dirac cones by strain or external fields. Our spectroscopic approach exploits angle- and spin-resolved photoemission (ARPES, Spin-ARPES) for the topological bands, and scanning tunneling microscopy and spectroscopy (STM, STS) for the edge state phenomena.


    [1] Y. L. Chen, et al., Science 329, 659 (2010).

    [A08.1] A. Barfuss, L. Dudy, M. R. Scholz, H. Roth, P. Höpfner, C. Blumenstein, G. Landolt, J. H. Dil, N. C. Plumb, M. Radovic, A. Bostwick, E. Rotenberg, A. Fleszar, G. Bihlmayer, D. Wortmann, G. Li, W. Hanke, R. Claessen, and J. Schäfer, Elemental Topological Insulator with Tunable Fermi Level: Strained α-Sn on InSb(001), Phys. Rev. Lett. 111, 157205 (2013).

    [2] Y. Tanaka, et al., Phys. Rev B 87, 155105 (2013).