Ab initio electronic structure of solid coronene: Differences from and commonalities to picene

We have obtained the first-principles electronic structure of solid coronene, which has been recently reported to exhibit superconductivity with potassium doping. Since coronene, along with picene, the first aromatic superconductor, now provides a class of superconductors as solids of aromatic compounds, here we compare the two cases by examining the electronic structures. In the undoped coronene crystal, where the molecules are arranged in a herringbone structure with two molecules in a unit cell, the conduction band above an insulating gap is found to comprise four bands, which basically originate from the lowest two unoccupied molecular orbitals (doubly-degenerate, reflecting the high symmetry of the molecular shape) in an isolated molecule but the bands are entangled as in solid picene. The Fermi surface for a candidate of the structure of K(x)coronene with x = 3, for which superconductivity is found, comprises multiple sheets, as in doped picene but exhibiting a larger anisotropy with different topology.