A strongly-interacting model for antiferromagnetism in one-dimensional C60-polymers: A1C60

We study the antiferromagnetic phase of the C60-polymer doped with one electron per one C60 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 C60 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 A1C60 phase can be explaind 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 C60-polymers. ∗E-mail address: [email protected]; URL: http://www.etl.go.jp/People/harigaya/