Quantum Monte Carlo study of the attractive kagome-lattice Hubbard model

The recent experimental discovery of several families of kagome materials has boosted the interest in electronic correlations on a kagome lattice. As an initial step to understand the observed complex phenomena, it is helpful to know the correspondence between the simple forms of interactions and the induced correlated states on a kagome lattice. Considering the lack of such studies, here we systematically investigate the attractive kagome-lattice Hubbard model using the mean-field approach and determinant quantum Monte Carlo (DQMC). A charge-density-wave order satisfying the triangle rule is predicted by the mean-field treatment, and subsequent DQMC simulations provide indirect evidence for its existence. The s-wave superconductivity is found to be stabilized at low temperatures, and to exist in dome regions of the phase diagrams. We then determine the superconducting critical temperature quantitatively by finite-size scaling of the pair structure factor. These results may be helpful in understanding the observed superconductivity in kagome materials.