Disorder, metal-insulator crossover and phase diagram in high-T-c cuprates

We have studied the influence of disorder induced by electron irradiation on the normal-state resistivities rho(T) of optimally and underdoped YBa2Cu3Ox single crystals, using pulsed magnetic fields up to 60T to completely restore the normal state. We evidence that point defect disorder induces low-T upturns of rho(T) which saturate in some cases at low T in large applied fields as would be expected for a Kondo-like magnetic response. Moreover, the magnitude of the upturns is related to the residual resistivity, that is to the concentration of defects and/ or their nanoscale morphology. These upturns are found quantitatively identical to those reported in lower-Tc cuprates, which establishes the importance of disorder in these supposedly pure compounds. We therefore propose a realistic phase diagram of the cuprates, including disorder, in which the superconducting state might reach the antiferromagnetic phase in the clean limit. Copyright (C) EPLA, 2008