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

TLDR

The 1/6 hole‑doped Kagome lattice has its Fermi level at a van Hove singularity with a perfectly nested Fermi surface. The study investigates electronic instabilities of the Hubbard model on this lattice. The authors employ the variational cluster approach to analyze these instabilities. For 1/6 hole‑doped Kagome, a chiral \(d_{x^{2}-y^{2}}+i d_{xy}\) superconducting state dominates at weak Hubbard interaction (U < 3 t), a scalar chiral spin‑density‑wave emerges at strong coupling (U > 5.5 t), and an intermediate spin‑disordered insulating phase is proposed.

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 ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}+i{d}_{xy}$ superconducting state is most favorable when a small Hubbard interaction $U$ ($U&lt;3.0t$) is introduced, and a scalar chiral spin order is realized at large $U$ ($U&gt;5.5t$). Between them, a spin-disordered insulating state is proposed.