Density functional calculations of electronic structure and magnetic properties of the hydrocarbon K₃picene superconductor near the metal-insulator transition

We have investigated the electronic structures and magnetic properties of a newly discovered hydrocarbon superconductor, K₃picene, having T _c = 18 K. We have shown that the metal-insulator transition is driven in K₃picene by 5% volume enhancement with the formation of the local magnetic moment. Active bands for the superconductivity near the Fermi level (E_F) have hybridized character of LUMO and LUMO+1 of the picene molecule. Fermi surfaces of K₃picene manifest neither prominent nesting feature nor marked two-dimensional behavior. By estimating the ratio of the Coulomb interaction, U, and the bandwidth, W, of the active bands near E_F, we have demonstrated that K₃picene is located in the vicinity of the Mott transition. Our findings suggest that K₃picene is a strongly correlated electron system.