INPLANE RESISTIVITY OF LA-DOPED BI2SR2CUO6-CRYSTALS(DELTA SINGLE)

The in-plane resistivity (rho(ab)) of series of Bi2Sr2-xLaxCuOy single crystals with the highest T-c(rho=0) up to 23K has been studied betwe en 4.2 similar to 300K over a wide composition range from the underdop ed insulator to the overdoped superconductor. The observed superconduc tor-insulator (ST) transition is consistent with the two dimensional ( 2D) localization We found for the first time a universal dR(sheet)/dT behavior among all high temperature superconductors (NTS) in the under doped regime. Due to a possible dimensional crossover, a change in the electronic state with the appearance of normal electrons in the overd oped regime is discussed.