Universal superconductor-insulator transition and Tc depression in Zn-substituted high-Tc cuprates in the underdoped regime.

Abstract

The experimental results are presented on the in-plane resistivity for Zn-substituted single crystals of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$ and ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ with various hole densities. The primary effect of Zn is to produce a large residual resistivity ( ${\ensuremath{\rho}}_{0}$) as a potential scatterer in the unitarity limit. In the underdoped regime, due also to low carrier density in the ${\mathrm{CuO}}_{2}$ plane, only a few percent Zn is sufficient for ${\ensuremath{\rho}}_{0}$ 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.