Optimized unconventional superconductivity in a molecular Jahn-Teller metal.

Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above T c is a major challenge for all unconventional superconductors. The molecular A3C60 fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C60 (3-) electronic structure controls the geometry and spin state of the structural building unit via the on-molecule Jahn-Teller effect. We identify the Jahn-Teller metal as a fluctuating microscopically heterogeneous coexistence of both localized Jahn-Teller-active and itinerant electrons that connects the insulating and superconducting states of fullerides.

Synthesis of face-centred cubic Cs3C60 in THF.

A solution chemistry synthetic route yields Cs(3)C(60) with a face-centred cubic structure. The described method uses well-established Schlenk techniques and THF as a solvent. The controlled addition of an organo-metallic salt reducing agent prevents the formation of C(60)(4-) salts.