Discovery of Superconductivity in Potassium-Doped Tri- p-tolylbismuthine

Explorations of benzene-based organic superconductors and bismuth-based functional materials are today's hottest topics in chemistry, physics, and materials science. Here, we show that by doping potassium into an organobismuth molecule, tri-p-tolylbismuthine, which is composed of one bismuth atom and three methylphenyl groups, all synthesized samples exhibit type-II superconductivity at 3.6 K at ambient pressure and one sample also shows superconductivity at 5.3 K. The common 3.6 K superconducting phase is identified to have a triclinic P1 structure, with a mole ratio of 3:1 between potassium and tri-p-tolylbismuthine. The calculated electronic structure indicates that superconductivity is produced by transferring an electron from K 4s to the C 2p orbital, which results in both red and blue shifts of the Raman spectra. Our study enriches the physical functionality of organobismuth compounds and illustrates a new route for the search of organic superconductors.