Superconductivity in Conducting Polymer/Fullerence Composite Doped by Alkali Metal

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 C^1- ₆₀ radical.