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~√N, where U is the Coulomb interaction and W is the bandwidth. This is supported by exact-diagonalization and Monte Carlo calculations. Realistic parameters for the doped fullerenes lead to the conclusions that stoichiometric A₃C₆₀(A=K,0ex0exRb) are near the Mott-Hubbard transition, in a correlated metallic state.
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Gunnarsson et al. (1996) studied this question.