Compressibility of M3C60 Fullerene Superconductors: Relation Between Tc and Lattice Parameter
OTTO ZHOU 1,
QING ZHU 1,
JOHN E. FISCHER 1,
NICOLE COUSTEL 1,
GAVIN B. M. VAUGHAN 2,
PAUL A. HEINEY 2,
JOHN P. MCCAULEY JR. 3, and
AMOS B. SMITH III 3
1 Laboratory for Research on the Structure of Matter and Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
2 Laboratory for Research on the Structure of Matter and Department of Physics, University of Pennsylvania, Philadelphia, PA 19104
3 Laboratory for Research on the Structure of Matter and Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K3C60 and Rb3C60, the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature Tc measured by other groups, establish a universal first-order relation between Tc and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.
Submitted on November 18, 1991
Accepted on January 2, 1992
