STRUCTURE AND SUPERCONDUCTIVITY OF C60 FULLERIDES

In alkali-metal (A) doped C60 fullerides superconductivity is found only for face-centered cubic (f.c.c.) crystal phases with the composition A3C60. The highest T(c) of 33 K found in these f.c.c. A3C60 superconductors family is surpassed only by that of the high T(c) copper oxides. We describe here the stability and dopant site selectivity of A3C60 fullerides as well as the factors controlling the f.c.c. lattice parameters. Superconductivity studied by diamapetic susceptibility measurements is described in detail, especially in the small lattice parameter region. The relationship between the f.c.c. structure and the superconductivity is described and the phonon frequency associated with electron pairing is discussed within the framework of the phonon-mediated type McMillan equation. Experimental results, which are not well understood, are also discussed with reference to the literature.