Kane-Mele-Hubbard model on the π-flux honeycomb lattice

Martin Bercx, Martin Hohenadler, and Fakher F. Assaad
Phys. Rev. B 90, 075140 – Published 22 August 2014

Abstract

We consider the Kane-Mele-Hubbard model with a magnetic π flux threading each honeycomb plaquette. The resulting model has remarkably rich physical properties. In each spin sector, the noninteracting band structure is characterized by a total Chern number C=±2. Fine-tuning of the intrinsic spin-orbit coupling λ leads to a quadratic band crossing point associated with a topological phase transition. At this point, quantum Monte Carlo simulations reveal a magnetically ordered phase that extends to weak coupling. Although the spinful model has two Kramers doublets at each edge and is explicitly shown to be a Z2 trivial insulator, the helical edge states are protected at the single-particle level by translation symmetry. Drawing on the bosonized low-energy Hamiltonian, we predict a correlation-induced gap as a result of umklapp scattering for half-filled bands. For strong interactions, this prediction is confirmed by quantum Monte Carlo simulations.

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  • Received 30 June 2014
  • Revised 6 August 2014

DOI:https://doi.org/10.1103/PhysRevB.90.075140

©2014 American Physical Society

Authors & Affiliations

Martin Bercx*, Martin Hohenadler, and Fakher F. Assaad

  • Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

  • *martin.bercx@physik.uni-wuerzburg.de

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Issue

Vol. 90, Iss. 7 — 15 August 2014

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