Mott transition and superconductivity in alkali-doped fullerides

摘要

We study the effects of deviations from cubic symmetry on superconductivity and on Mott transitions by comparing A_3C_(60) and NH_3K_3C_(60). The reduced frustration in NH_3K_3C_(60) favours a Mott transition at a lower ratio U/W, where U is the Coulomb repulsion of two electrons on the same molecule and W is the width of the t_(1u) band. The closeness of NH_3K_3C_(60) to a Mott transition may influence the superconductivity negatively, due to an inefficient screening of the Coulomb repulsion.