Charge instabilities and topological phases in the extended Hubbard model on the honeycomb lattice with enlarged unit cell

Abstract

We study spontaneous symmetry breaking in a system of spinless fermions in the honeycomb lattice paying special emphasis to the role of an enlarged unit cell on time reversal symmetry broken phases. We use a tight-binding model with nearest-neighbor hopping t and Hubbard interaction V1 and V 2 and extract the phase diagram as a function of electron density and interaction within a mean-field variational approach. The analysis completes the previous work done in Phys. Rev. Lett.107.106402 (2011) where phases with nontrivial topological properties were found with only a nearest-neighbor interaction V1 in the absence of charge decouplings. We see that the topological phases are suppressed by the presence of metallic charge density fluctuations. The addition of next to nearest-neighbor interaction V2 restores the topological nontrivial phases. © 2013 American Physical Society.