Magnetic penetration depth and condensate density of cuprate high-Tc superconductors determined by muon-spin-rotation experiments.

We summarize our results of transverse-field muon-spin-relaxation (TF-\ensuremath{\mu}SR) experiments on a variety of polycrystalline cuprate high-${\mathit{T}}_{\mathit{c}}$ superconducting systems. In this paper we present the conditions under which the \ensuremath{\mu}SR depolarization rate at low temperatures ${\mathrm{\ensuremath{\sigma}}}_{0}$\ensuremath{\propto}${\ensuremath{\lambda}}_{\mathit{a}\mathit{b}}^{\mathrm{\ensuremath{-}}2}$(0)\ensuremath{\propto}${\mathit{n}}_{\mathit{s}}$(0)/${\mathit{m}}_{\mathit{a}\mathit{b}}^{\mathrm{*}}$ is determined in a unique way by the doping state of ${\mathrm{CuO}}_{2}$ planes and the consequent critical temperature ${\mathit{T}}_{\mathit{c}}$. Disorder and pinning effects due to various sorts and amounts of dopant atoms do not affect ${\mathrm{\ensuremath{\sigma}}}_{0}$. From our results on ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$, ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$, and ${\mathrm{Y}}_{2}$${\mathrm{Ba}}_{4}$${\mathrm{Cu}}_{7}$${\mathrm{O}}_{15\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ (systems having both planes and chains) we conclude that a superconducting condensate is not only formed in the ${\mathrm{CuO}}_{2}$ planes but is induced additionally in the CuO chains. This chain condensate is rapidly suppressed by any disorder in the chains and depends strongly on the oxygen ordering.