Metal-to-insulator crossover in the low-temperature normal state of Bi2Sr2-xLaxCuO6+δ

We measure the normal-state in-plane resistivity of Bi2Sr2-xLaxCuO6+delta single crystals at low temperatures by suppressing superconductivity with 60 T pulsed magnetic fields. With decreasing hole doping, we observe a crossover from a metallic to an insulating behavior in the low-temperature normal state. This crossover is estimated to occur near 1/8 doping, well inside the underdoped regime, and not at optimum doping as reported for other cuprates. The insulating regime is marked by a logarithmic temperature dependence of the resistivity over two decades of temperature, suggesting that a peculiar charge localization is common to the cuprates.