Bulk superconductivity at 38 K in a molecular system

Ganin, A.Y. , Takabayashi, Y., Khimyak, Y.Z., Margadonna, S., Tamai, A., Rosseinsky, M.J. and Prassides, K. (2008) Bulk superconductivity at 38 K in a molecular system. Nature Materials, 7(5), pp. 367-371. (doi: 10.1038/nmat2179)

Abstract

C₆₀based solids¹ are archetypal molecular superconductors with transition temperatures (T_c) as high as 33 K (refs 2–4). T_c of face-centred-cubic (f.c.c.) A₃C₆₀ (A=alkali metal) increases monotonically with inter C₆₀ separation, which is controlled by the A⁺ cation size. As Cs⁺ is the largest such ion, Cs₃C₆₀ is a key material in this family. Previous studies revealing trace superconductivity in Cs_xC₆₀ materials have not identified the structure or composition of the superconducting phase owing to extremely small shielding fractions and low crystallinity. Here, we show that superconducting Cs₃C₆₀ can be reproducibly isolated by solvent-controlled synthesis and has the highest T_c of any molecular material at 38 K. In contrast to other A₃C₆₀materials, two distinct cubic Cs₃C₆₀ structures are accessible. Although f.c.c. Cs₃C₆₀ can be synthesized, the superconducting phase has the A15 structure based uniquely among fullerides on body-centred-cubic packing. Application of hydrostatic pressure controllably tunes A15 Cs₃C₆₀ from insulating at ambient pressure to superconducting without crystal structure change and reveals a broad maximum in T_c at []7 kbar. We attribute the observed T_c maximum as a function of inter C₆₀separation—unprecedented in fullerides but reminiscent of the atom-based cuprate superconductors—to the role of strong electronic correlations near the metal–insulator transition onset.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ganin, Dr Alexey
• Authors: Ganin, A.Y., Takabayashi, Y., Khimyak, Y.Z., Margadonna, S., Tamai, A., Rosseinsky, M.J., and Prassides, K.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Nature Materials
• Publisher: Nature Publishing Group
• ISSN: 1476-1122
• ISSN (Online): 1476-4660