Anomalous 1/ φ noise spectrum of potassium-doped bulk C 60 and C 70 in both the normal and superconducting transition region

Abstract

We have prepared potassium-doped bulk K xC 60,70 and measured noise spectrum power as a function of temperature. We discovered that in the normal state, the magnitude of the normalized noise spectral power density is greater by about eleven orders of magnitude than the value of a normal metal predicted by Hooge's formula. Another unusual findings is the observation of a markedly enhanced peak near the superconducting transition, which cannot be explained by presently available theories.