Flux phases in the extended Hubbard model on the triangular lattice

Using the unrestricted Hartree-Fock variational method, we study the extended Hubbard model in the triangular lattice at 3/4 filling. Due to the nesting instability of the Fermi surface, various density wave states compatible with the 2 × 2 supercell are found as the ground state by tuning the onsite and nearest neighbor repulsions U and V. Surprisingly, the flux phases with complex bond order parameters are realized in a wide range of the U-V phase diagram. They also acquire nontrivial topological properties due to the spontaneous breaking of the time-reversal symmetry. Our study suggests that the flux phases can be stabilized by the interplay between short-range repulsive interactions in correlated electron systems.