Strong correlation effects in the fullerene C20 studied using a one-band Hubbard model

The smallest fullerene, dodecahedral C20, is studied using a one-band Hubbard model parametrized by U∕t. Results are obtained using exact diagonalization of matrices with linear dimensions as large as 5.7×109, supplemented by quantum Monte Carlo. We report the magnetic and spectral properties of C20 as a function of U∕t and investigate electronic pair binding. Solid forms of C20 are studied using cluster perturbation theory, and evidence is found for a metal-insulator transition at U∼4t. We also investigate the relevance of strong correlations to the Jahn-Teller effect in C20.