The effect of carrier concentration on fulleride superconductivity is studied by x ray, Raman, magnetization, and ESR of two new cubic families: Na2CsxC60 (0<x<1) and M3-yBayC60 (0.2<y<2, M = K, Rb, or Cs). These are isostructural with known Pa3¯ and Fm3¯m trivalent superconductors, respectively, but with variable valence 2<n<5. Tc is peaked at or very near n = 3, decreasing rapidly in either direction to <0.5 K for n = 2.5 and 5. These results underscore the failure of both one-electron and strong correlation models to explain the dependence of Tc on band filling.
|Number of pages||4|
|Journal||Physical review letters|
|Publication status||Published - 1 Jan 1996|