Superconductivity and Site-Selective Intercalation in KRbCsC₆₀

Abstract

Ternary-alkali-metal-intercalated fullerides, KRbCsC₆₀, was prepared by method employing alkali metal azides reported by Bensebaa et al. (F. Bensebaa, B. Xiang and L. Kevan: J. Phys. Chem. 96 (1992) 6118). We found that KRbCsC₆₀ is a superconductor with the transitipn temperature of 28(bulk)∼29 K (onset). It was also found, from nuclear magnetic resonance (NMR) study of ⁸⁷Rb and ¹³³Cs in this system, that the alkali atoms are site-selectively intercalated into C₆₀ face-centered-cubic (fcc) lattice. The largest alkali-metal ion, Cs, occupies octahedral sites of the C₆₀ fcc lattice, and the K and Rb atoms occupy mainly tetrahedral sites.