Optimized unconventional superconductivity in a molecular Jahn-Teller metal

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Science Advances  17 Apr 2015:
Vol. 1, no. 3, e1500059
DOI: 10.1126/sciadv.1500059


Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above Tc 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 C603– 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 Tc with interfulleride separation, demonstrating molecular electronic structure control of superconductivity.

  • superconductivity
  • Strong correlations
  • Jahn-Teller effect
  • Metal-insulator transitions

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