Strongly interacting model for antiferromagnetism in one-dimensional C-60 polymers: A C-60

We study the antiferromagnetic phase of the C-60 polymer doped with one electron per one C-60 by using a tight-binding model with long-range Coulomb interactions. The model is solved by the unrestricted Hartree-Fock approximation, and a phase diagram is obtained by changing Coulomb interaction strengths and a conjugation parameter between C-60 molecules. We find that the antiferromagnetism is well described by the present model. The comparison with the photoemission studies shows that the new band around the Fermi energy of the AC(60) phase can be explained by the extremely large intrusion of an energy level into the gap of the neutral system. This indicates that the interaction effects among electrons are important in doped C-60 polymers.