• Jeglič, Peter

Abstract

<jats:p>Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above <jats:italic>T</jats:italic><jats:sub>c</jats:sub> is a major challenge for all unconventional superconductors. The molecular A<jats:sub>3</jats:sub>C<jats:sub>60</jats:sub> fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C<jats:sub>60</jats:sub><jats:sup>3–</jats:sup> 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. The balance between these molecular and extended lattice features of the electrons at the Fermi level gives a dome-shaped variation of <jats:italic>T</jats:italic><jats:sub>c</jats:sub> with interfulleride separation, demonstrating molecular electronic structure control of superconductivity.</jats:p>

Topics

• impedance spectroscopy
• superconductivity
• superconductivity