Isotope Effect in Superconducting Fullerenes

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Science  29 May 1992:
Vol. 256, Issue 5061, pp. 1306-1308
DOI: 10.1126/science.256.5061.1306


The effect of isotopic substitution on the superconducting transition temperature, Tc, in alkali-doped C60 has been examined. Paradoxically, it is found that a substantial decrease in Tc with the increasing isotopic mass is possible even when the attractive interaction is not mediated by phonons but is instead of purely electronic origin. In particular, it is shown that the experimentally measured isotopic shifts are consistent with a recently proposed electronic mechanism. Further predictions are presented that can be tested by experiment.