title: The disorder-free non-BCS superconductor Cs3C60 emerges from an antiferromagnetic insulator parent state.
abstract: The body-centered cubic A15-structured cesium fulleride Cs3C60 is not superconducting at ambient pressure and is free from disorder, unlike the well-studied face-centered cubic A3C60 alkali metal fulleride superconductors. We found that in Cs3C60, where the molecular valences are precisely assigned, the superconducting state at 38 kelvin emerges directly from a localized electron antiferromagnetic insulating state with the application of pressure. This transition maintains the threefold degeneracy of the active orbitals in both competing electronic states; it is thus a purely electronic transition to a superconducting state, with a dependence of the transition temperature on pressure-induced changes of anion packing density that is not explicable by Bardeen-Cooper-Schrieffer (BCS) theory.
authors.affiliation: Department of Chemistry, University of Durham, Durham DH1 3LE, UK.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takabayashi
authors.forename: Alexey Y
authors.initials: AY
authors.lastname: Ganin
authors.forename: Peter
authors.initials: P
authors.lastname: Jeglic
authors.forename: Denis
authors.initials: D
authors.lastname: Arcon
authors.forename: Takumi
authors.initials: T
authors.lastname: Takano
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iwasa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohishi
authors.forename: Masaki
authors.initials: M
authors.lastname: Takata
authors.forename: Nao
authors.initials: N
authors.lastname: Takeshita
authors.forename: Kosmas
authors.initials: K
authors.lastname: Prassides
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Rosseinsky