Impurity Effects on Superconductivity of LaO1−xFxBi1−ySbyS2 through Specific Heat Measurements

In this study, we illustrate the effect of Sb substitution on a single crystal of the layered superconductor LaO1−xFxBi1−ySbyS2 through specific heat measurements. LaO1−xFxBiS2 (x = 0.4 and 0.5) and LaO0.5F0.5Bi1−ySbyS2 (y = 0–0.20) were synthesized by the flux method under ambient pressure. The electronic specific heat Ce of LaO1−xFxBiS2 (x = 0.4 and 0.5) below ∼Tc can be explained by s-wave superconductivity with either a single gap or two gaps. The Ce/T at T ≪ Tc in LaO0.5F0.5Bi1−ySbyS2 below y = 0.06 is hardly recovered by Sb substitution, indicating that the superconductivity is robust against nonmagnetic impurities.