Impurities of arbitrary range and strength in d-wave superconductors

The self-consistent T-matrix approximation for an alloy model of defects, described by scattering potentials of arbitrary range, is used to calculate quasiparticle lifetime effects as well as the order parameter renormalization in 2D d-wave superconductors. The study has been motivated by measurements of the microwave conductivity at low temperatures of extremely high quality samples of YBCO, the results of which do not really fit into the widely accepted d-wave picture. Poorly screened defects outside the CuO2-planes could be the cause of the discrepancy. Apart from changing the single particle properties, the finite range of the defects affects the conductivity through vertex corrections, which project out forward scattering. (C) 2003 Elsevier Science B.V. All rights reserved.