Universal suppression by in-plane defects in high-temperature superconductors: Implications for pairing symmetry

The influence of in-plane oxygen defects on the critical temperature, resistivity, and Hall coefficient was studied in (Formula presented)(Formula presented)(Formula presented) (YBCO) films with different oxygen contents ((Formula presented) ranging from 30 to 93 K) with emphasis on the underdoped “spin-gap phase.” A strong (Formula presented) suppression was observed, but no influence of the defects on “spin-gap” features in the transport properties was found. A comparison is made with (Formula presented) suppression by other in-plane defects such as Zn substitutions for Cu, Pr substitutions for Y in YBCO, and radiation defects in Bi-2201 and Bi-2212 high-(Formula presented) superconductors. (Formula presented) suppression by defects is shown to occur in a universal way which is independent of the (Formula presented), carrier concentration, and number of (Formula presented) planes per unit cell. It is shown that, independent of whether the in-plane defects induce localized magnetic moments or not, (Formula presented) is a universal function of the impurity scattering rate, which can be described by the pair-breaking theory for potential scatterers in d-wave superconductors, but requires that the pair-breaking rate be a factor of 3 smaller than that suggested by the transport data. An alternative description of the (Formula presented) suppression in terms of the phase fluctuation theory proposed recently by Emery and Kivelson is also discussed.