The disorder-free non-BCS superconductor Cs3C60 emerges from an antiferromagnetic insulator parent state.
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.
Takabayashi
Yasuhiro
Y
Department of Chemistry, University of Durham, Durham DH1 3LE, UK.
Ganin
Alexey Y
AY
Jeglic
Peter
P
Arcon
Denis
D
Takano
Takumi
T
Iwasa
Yoshihiro
Y
Ohishi
Yasuo
Y
Takata
Masaki
M
Takeshita
Nao
N
Prassides
Kosmas
K
Rosseinsky
Matthew J
MJ