The effects of chain disorder on superconductivity in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ are discussed within the context of a proximity model. Chain disorder causes both pair breaking and localization. The hybridization of chain and plane wave functions reduces the importance of localization, so that the transport anisotropy remains large in the presence of a finite fraction $\delta$ of oxygen vacancies. Penetration depth and specific heat measurements probe the pair breaking effects of chain disorder, and are discussed in detail at the level of the self-consistent T-matrix approximation. Quantitative agreement with these experiments is found when chain disorder is present.

• Received 19 October 1998

DOI:https://doi.org/10.1103/PhysRevB.59.3377