A Comparison of the Effects of Sm and Pb Doping in Bi4O4S3 Superconductor

The effects of isovalent Sm doping and bivalent Pb doping at the Bi site on the superconductivity of Bi4O4S3 superconductor are studied and compared. It is found that the bivalent Pb doping results in much faster decrease of superconducting transition temperature and upper critical field, compared with the isovalent Sm doping. Hall effect measurements suggest that bivalent Pb doping gives rise to rapid decrease in electron-like charge carrier concentration. Our results indicate that the bivalent Pb ions not only act as the impurity scatterers but also introduce hole-type charge carriers, which is harmful to the superconductivity in Bi4O4S3 system.