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The Disorder-Free Non-BCS Superconductor Cs 3 C 60 Emerges from an Antiferromagnetic Insulator Parent State

2009; American Association for the Advancement of Science; Volume: 323; Issue: 5921 Linguagem: Inglês

10.1126/science.1169163

1095-9203

Yasuhiro Takabayashi, Alexey Y. Ganin, P. Jeglič, Denis Arčon, Takumi Takano, Yoshihiro Iwasa, Yasuo Ohishi, Masaki Takata, Nao Takeshita, Kosmas Prassides, Matthew J. Rosseinsky,

High-pressure geophysics and materials

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.