Testing models of the symmetry of the superconducting pairing state by low-temperature electron irradiation of an untwinned single crystal of YBa2Cu3O7-δ

We have carried out in situ resistivity measurements in a high-voltage electron microscope to determine how the superconducting transition temperature Tc and the resistivity ρ(T) change with low-temperature electron irradiation. We find that point defects introduced by oxygen displacements from the CuO2 planes make the dominant contribution to the irradiation-induced suppression of Tc. We find that dTc/dρ is ∼-0.30±0.04 K/μΩ cm. Analysis of this result indicates the effect of strongly anisotropic superconductivity, and rules out isotropic s-wave pairing. Even though our data cannot determine whether the pairing symmetry is s or d wave, they provide a test for further theoretical developments