Verification of Nodeless Superconducting Pairing in Single-Crystal YBa2Cu3O7

Abstract

The temperature and field dependence of the penetration depth was determined from muon spin rotation (μ+ SR ) measurements on a single crystal of YBa 2 Cu 3 O 7 having a superconducting transition at Tc ≈ 91.3 K . Data were acquired at applied magnetic fields of 0.05, 1.0, 3.0, and 6.0 Tesla, yielding results inconsistent with any pairing state requiring nodes, including d-wave pairing. These data are, however, completely consistent with s-wave (or extended s-wave) superconductivity, with clear evidence of field-dependent, temperature-activated vortex pinning. Our results confirm the s-wave character originally observed in 1989, and show that the features of μ+ SR (and microwave) data used by other authors as evidence for d-wave superconductivity are instead due to temperature- and field-dependent vortex pinning/reordering, resulting in significant distortion of the flux lattice.