Kinetic Ferromagnetism on a Kagome Lattice

We study strongly correlated electrons on a kagome lattice at $1/6$ (and $5/6$) filling. They are described by an extended Hubbard Hamiltonian. We are concerned with the limit |t|VU with a hopping amplitude t, nearest-neighbor repulsion V, and on-site repulsion U. We derive an effective Hamiltonian and show, with the help of the Perron--Frobenius theorem, that the system is ferromagnetic at low temperatures. The robustness of ferromagnetism is discussed and extensions to other lattices are indicated.