Unusual T-c variation with hole concentration in Bi2Sr2-xLaxCuO6+delta

We have investigated the T-c variation with the hole concentration p in the La-doped Bi-2201 system, Bi2Sr2-xLaxCuO6+delta. It is found that the Bi-22 01 system does not follow the systematics in T-c and p observed in other hi gh-T-c cuprate superconductors (HTSC's). The T-c vs p characteristics are q uite similar to those observed in Zn-doped HTSC's. An exceptionally large r esidual resistivity component in the in-plane resistivity indicates that st rong potential scatterers of charge carriers reside in CuO2 planes and are responsible for the unusual T-c variation with p, as in the Zn-doped system s. However, contrary to the Zn-doped HTSC's, the strong scatter in the Bi-2 201 system is possibly a vacancy in the Cu site.