Metal-to-Insulator Crossover in the Low-Temperature Normal State of ${{\mathrm{Bi}}_2\mathrm{Sr}}_{2-\mathit{x}}{\mathrm{La}}_{\mathit{x}}{\mathrm{CuO}}_{6+\delta }$

We measure the normal-state in-plane resistivity of ${\mathrm{Bi}}_2{\mathrm{Sr}}_{2-x}{\mathrm{La}}_x{\mathrm{CuO}}_{6+\delta }$ 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.