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 diamagnetic 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.