Hubbard model and fullerenes: Stability of the Nagaoka state.

Abstract

We prove numerically that the saturated ferromagnetic state in the Hubbard model with infinitely large Coulomb repulsion and one hole (Nagaoka state) is unstable for a fullerene cluster if the hopping integral is negative, and possibly stable if possible. We analyze the stability versus the variation of the ratio between the hopping values for the two types of carbon-carbon bonds. The results suggest the existence of ferromagnetism in doped fullerene when the electronic correlation leads to a large effective electron-electron interaction.