Chiral superconducting phase and chiral spin-density-wave phase in a Hubbard model on the kagome lattice

Abstract

We study the electronic instabilities of the Hubbard model in the 1/6 hole-doped Kagome lattice using the variational cluster approach. The 1/6 hole doping is unique in the sense that the Fermi level is at the van Hove singularity and the Fermi surface has a perfect nesting. In this case, a density wave is usually realized. However, we demonstrate here that the chiral $d_{x^2-y^2}+i{d}_{xy}$ superconducting state is most favorable when a small Hubbard interaction $U$ ($U<3.0t$) is introduced, and a scalar chiral spin order is realized at large $U$ ($U>5.5t$). Between them, a spin-disordered insulating state is proposed. DOI: http://dx.doi.org/10.1103/PhysRevB.85.144402 ©2012 American Physical Society