Superconductivity in the Narrow Gap Semiconductor RbBiTe.

Superconductivity was discovered in the layered compound RbBiTe, 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 RbBiSbSeTe revealed a dependence of the superconducting transition on composition that can increase the T up to ∼10%. The RbBiTe system is the first member of the new homologous series Rb[BiTe] with infinite BiTe-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.