The Hubbard model on the kagome lattice

In itinerant magnetically frustrated materials it is important to elucidate the effect of the electronic correlation on the band structure and how it evolves as a function of the electronic concentration n. In this work we address this problem by considering the Hubbard model on a kagome lattice with a single orbital per site, treating the local Coulomb repulsion U within the coherent potential approximation. A metal-insulator transition occurs in the half- filled band (n = 1) at Uc = 3.635t. A nearly flat band, characteristic of frustrated lattices, is present at the top of the band structure. For concentrations n > 4/3, the chemical potential may be located in this very narrow band, and one obtains a significant enhancement of the. coefficient of the specific heat depending on the value of U. This effect can be at the origin of the heavy fermion behaviour observed in LiV2O4.