Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 87: Low-dimensional systems: Topological order 2 (TT with DS/HL/MA/O)

HL 87.12: Talk

Thursday, March 19, 2015, 18:00–18:15, H 3010

Calculation of topological properties of strongly correlated electrons without inversion symmetry using Wannier charge centres. — •Robert Triebl and Markus Aichhorn — Institute of Theoretical Physics and Computational Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria

We study the topological properties of a role model for interacting Z₂ topological insulators, namely the Kane-Mele-Hubbard model including a staggered sublattice potential controlled by a parameter λ_ν, which breaks inversion symmetry. The applicability of a naïve mean field approach was analysed by comparing to a variational cluster approach, employing a two-site dynamical impurity approximation (DIA). The obtained Greens function determines the topological Hamiltonian, which maps the interacting system to an effective free-particle model with the same topological properties. Since inversion symmetry is lost, we calculate the Z₂ invariant for both Mean Field and topological Hamiltonian using Wannier charge centers. We conclude that a two-site DIA in combination with Wannier charge centers is an easy-to-implement and stable method to determine topological invariants for interacting systems. Comparing with mean field results we find that the direction of magnetisation is crucial for topological properties and hence an inherent mean field magnetisation may lead to incorrect results.