# Laboratoire de Physique ThéoriqueToulouse - UMR 5152

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Mardi 7 octobre 2014-14:00

## $\pi$ flux states in correlated quantum spin Hall insulators.

Martin Bercx (Institut fuer Theoretische Physik & Astrophysik, Universitaet Wuerzburg, Germany)

par - 7 octobre 2014

When an external flux of $\pi$ is applied to a quantum spin Hall insulator, it creates two spatially localized electronic in-gap modes. Depending on their occupancy, the two modes constitute a spin fluxon or a charge fluxon, thereby realizing spin-charge separation in two dimensions. We use quantum Monte Carlo methods to study the Kane-Mele-Hubbard model augmented by $\pi$ flux insertions. The response to an individual $\pi$ flux can be used to detect the quantum spin Hall effect in a correlated system. The interaction between neighboring spin fluxons is mediated in the Kane-Mele-Hubbard model by a bosonic modes of magnetic excitons. This opens the possibility to study models of interacting magnetic moments hosted in the band gap of the topological insulator. Finally, we study the Kane-Mele-Hubbard model augmented by an extensive number of $\pi$ fluxes. The resulting model has remarkably rich physical properties and can be regarded as a two-dimensional counterpart to a topological crystalline insulator.

Post-scriptum :

contact : S. Capponi