Extended Hubbard model on a C20 molecule

The electronic correlations on a C20 molecule, as described by an extended Hubbard Hamiltonian with a nearest-neighbor Coulomb interaction of strength V, are studied using quantum Monte Carlo and exact diagonalization methods. For electron-doped C20, it is known that pair binding arising from a purely electronic mechanism is absent within the standard Hubbard model (V = 0). Here we show that this is also the case for hole doping for 0