Superconductivity in the Narrow Gap Semiconductor RbBi 11/3 Te 6 .

Superconductivity was discovered in the layered compound RbBi11/3 Te6 , featuring Bi vacancies and a narrow band gap of 0.25(2) eV at room temperature. A sharp superconducting transition at ∼3.2 K was observed in polycrystalline ingots. The superconducting volume fraction of oriented single crystals is almost 100%, confirming bulk superconductivity. Systematic Se and Sb substitutions in RbBi11/3-y Sby Sex Te6-x revealed a dependence of the superconducting transition on composition that can increase the Tc up to ∼10%. The RbBi11/3 Te6 system is the first member of the new homologous series Rb[Bi2n+11/3 Te3n+6 ] with infinite Bi2 Te3 -like layers. The large degree of chemical tunability of the electronic structure of the homology via doping and/or substitution gives rise to a new family of superconductors.