Universal superconductor-insulator transition and T-c depression in Zn-substituted high-T-c cuprates in the underdoped regime

The experimental results are presented on the in-plane resistivity for Zn-substituted single crystals of YBa2Cu3O7-y and La2-xSrxCuO4 with various hole densities. The primary effect of Zn is to produce a large residual resistivity (rho(0)) as a potential scatterer in the unitarity limit. In the underdoped regime, due also to low carrier density in the CuO2 plane, only a few percent Zn is sufficient for rho(0) to reach the critical value near the universal two-dimensional resistance h/4e(2) and to induce a superconductor-insulator transition. By contrast, the universal behavior is not seen in the highly doped regime, suggestive of a radical change in the electronic state.