Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 59: Low-Dimensional Systems: Poster Session

TT 59.11: Poster

Mittwoch, 9. März 2016, 15:00–18:30, Poster D

Breakdown of the bulk boundary correspondence in a strongly correlated model Hamiltonian — •Robert Triebl and Markus Aichhorn — Institute of Theoretical and Computational Physics, NAWI Graz, Graz Univerity of Technology, Petersgasse 16, 8010 Graz, Austria

We analyze the bulk boundary correspondence of a archetypal model for interacting Z₂ topological insulators, namely the Kane-Mele-Hubbard model, in particular focusing on the competition between topological and magnetic order. Both bulk and ribbon Green’s functions have been calculated using the variational cluster approach, employing a two-site dynamical impurity approximation (DIA). The Z₂ invariant of the bulk can be calculated with a Wannier charge center approach by mapping the interacting system to a topological Hamiltonian, which is an effective free-particle model with the same topological properties. The resulting invariants are compared to the existence of gapless edge states of the ribbon, where we use a site-dependent antiferromagnetic Weiss field on the ribbon. It turns out that spontaneous symmetry breaking occurs locally at the edges already at much smaller interactions than in the middle of the ribbon, leading to a gap in the edge spectral function. As a consequence, the topological invariant defined in the bulk may not correspond to the existence of gapless edge states since time reversal invariance is locally broken only at the edges.