In-plane resistivity of La-doped Bi 2Sr 2CuO 6+δ single crystals

Abstract

The in-plane resistivity ( ϱ ab) of series of Bi 2Sr 2− x La x CuO y single crystals with the highest T c ( ϱ=0) up to 23K has been studied between 4.2∼300K over a wide composition range from the underdoped insulator to the overdoped superconductor. The observed superconductor-insulator (SI) 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 (HTS) in the underdoped regime. Due to a possible dimensional crossover, a change in the electronic state with the appearance of normal electrons in the overdoped regime is discussed.