Muon Spin Relaxation Studies of Zn-Substitution Effects in High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Cuprate Superconductors

We have performed transverse-field muon spin relaxation measurements of the Zn-substituted cuprate high- ${T}_{c}$ superconductors: ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}({\mathrm{Cu}}_{1\ensuremath{-}y}{\mathrm{Zn}}_{y}){\mathrm{O}}_{4}$ and ${\mathrm{YBa}}_{2}({\mathrm{Cu}}_{1\ensuremath{-}y}{\mathrm{Zn}}_{y}{)}_{3}{\mathrm{O}}_{6.63}$. The superconducting carrier density/effective mass ${n}_{s}/{m}^{*}$ ratio at $T\ensuremath{\rightarrow}0$ decreases with increasing Zn concentration, in a manner consistent with our ``swiss cheese'' model in which charge carriers within an area $\ensuremath{\pi}{\ensuremath{\xi}}_{\mathrm{ab}}^{2}$ around each Zn are excluded from the superfluid. We discuss this result in the context of Bose condensation, pair localization, and pair breaking.