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O: Fachverband Oberflächenphysik

O 44: Low-Dimensional Systems: 2D - Theory (TT jointly with O)

O 44.5: Vortrag

Mittwoch, 2. April 2014, 10:30–10:45, BEY 81

The π flux honeycomb lattice: a topological crystalline insulator. — •Martin Bercx, Martin Hohenadler, and Fakher F. Assaad — Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, D-97074 Würzburg

We consider the Kane-Mele-Hubbard model with intrinsic spin-orbit coupling λ supplemented by a π flux threading each honeycomb plaquette. At U=0 and in each spin sector the band structure is characterized by a Chern number C = ± 2. Furthermore fine tuning of λ leads to a point of quadratic band crossing associated with a topological phase transition. Bulk quantum Monte Carlo simulations reveal a magnetically ordered phase which extends to weak couplings at the value of λ where the quadratic band crossing occurs. Although the spinful model carries two helical edge states and is explicitly shown to be a Z₂ trivial insulator, its edge states are robust due to protection by lattice translation symmetry. We present quantum Monte Carlo calculations which reveal that well defined edge states remain even in the case of strong interactions.