Superconductivity in Conducting Polymer/Fullerence Composite Doped by Alkali Metal

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Abstract
Superconductivity in poly(3-alkylthiophene)- C60 composite (PAT- C60) is found upon doping by potassium from vapor phase. The superconducting (SC) transition at T C=17 K is detected by superconducting quantum interference device (SQUID), which showed 0.8% of SC fraction for C60 content of 5 mol%. An exceptionally strong low-field microwave absorption (LFMA) implies the existence of granular SC phase. A rather small hysteresis of LFMA indicates the important role of the Josephson weak link network, probably formed between SC K x C60 clusters separated by conductive K x PAT barriers. ESR of PAT(C60) y K x composite shows two types of lines: one from negative polarons P - in PAT chains, and another assigned to K x C60 clusters and C1- 60 radical.