Low-field microwave absorption and ESR in “conducting polymer-fullerene-alkali metal” superconductors: Comparative study of various host matrices

Superconducting (SC) phases in various conducting polymer with fullerene C60 are found upon alkali metal vapor doping by low-field microwave absorption (LFMA) and probed by SQUID. At small C60 content, only normal phase of LFMA appears at rather low critical temperature. At large C60 content, the LFMA reveals unusual multipeaked spectra. In-phase LFMA and the paramagnetic Meissner effect in SQUID found for large y are interpreted in terms of π-junctions. The polarons in chains of CP are suggested as the possible origin of π-junctions.