Max-Planck-Institut für Festkörperforschung, Stuttgart, 70569, Germany

The authors constructed a model Hamiltonian for doped fullerides and discuss Monte Carlo methods for such lattice Hamiltonians including fixed-node diffusion Monte Carlo (DMC) method. Due to more efficient hopping, the orbital degeneracy increases the crit. U (on-site Coulomb interaction) at which the Mott transition takes place. This puts the integer-doped fullerides close to a Mott transition. Whether they are on the metallic or insulating side depends on the filling of the band and lattice structure; since the degeneracy enhancement works best for a half-filled band, systems doped away from half-filling tend to be more insulating. The effect of frustration, on the other hand, is to make the system more metallic.
 

in: Quantum Monte Carlo Methods in Physics and Chemistry, eds. M. P. Nightingale, C. J. Umrigar. Dordrecht: Kluwer Academic, 1998, 447-462 (Nato-ASI Workshop, Ithaca NY, 1998).