Mott Transition in Degenerate Hubbard Models: Application to Doped   Fullerenes
  The Mott-Hubbard transition is studied for a Hubbard model with orbital degeneracy N, using a diffusion Monte-Carlo method. Based on general arguments, we conjecture that the Mott-Hubbard transition takes place for U/W \propto \sqrt{N}, where U is the Coulomb interaction and W is the band width. This is supported by exact diagonalization and Monte-Carlo calculations. Realistic parameters for the doped fullerenes lead to the conclusion that stoichiometric A_3 C_60 (A=K, Rb) are near the Mott-Hubbard transition, in a correlated metallic state. 
Olle Gunnarsson (1), Erik Koch (1,2), and Richard M. Martin (1,2) ((1)   Max-Planck-Institut f\"ur Festk\"orperforschung, St...