Superconductivity in BiO1?xFxBiS2 and possible parent phase of Bi4O4S3 superconductor

We report the discovery of superconductivity in BiOFxBiS2, an isostructural compound of the REOFxBiS2 (RE: La, Nd, Pr, Ce, and Yb) superconductors. The parent compound, Bi2OS2, is nonsuperconductive. Superconductivity is observed in a wide range of F-doping content (0.06 x 0.27). The optimal F-doping concentration is about 0.24 in BiOFxBiS2, where the highest transition temperature of 3.5 K is achieved. We suppose that the superconductivity in BiOFxBiS2, as well as that in Bi3O2S3 and Bi4O4S3, is induced by partial substitution or insertion in the Bi2OS2 parent phase.