Normal-state Hall effect and the insulating resistivity of high-Tccuprates at low temperatures

The normal-state Hall coefficient $R_H$ and the in-plane resistivity ${\rho }_{\mathrm{ab}}$ are measured in La-doped ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CuO}}_y$ ${(T}_c\simeq 13$ K) single crystals and ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ thin films by suppressing superconductivity with 61-T pulsed magnetic fields. In contrast to data above $T_c,$ the $R_H$ below ∼10 K shows little temperature dependence in all the samples measured, irrespective of whether ${\rho }_{\mathrm{ab}}$ exhibits insulating or metallic behavior. Thus, whatever physical mechanism gives rise to insulating behavior in the low-temperature normal state, it leaves the Hall conductivity relatively unchanged.