Evidence for s+d Wave Pairing in Copper Oxide Superconductors from an Analysis of NMR and NQR Data

Knight shift and spin-lattice relaxation rate data of high temperature copper oxide superconductors are analyzed within a two-band model for superconductivity with coupled s+d wave superconducting gaps. The two-gap approach leads to substantial modifications of the coherence factors, which reflects itself in the Knight shift and the relaxation rate 1/T ₁ T. From the analysis it is concluded that the data are consistent with 40% s-wave and 60% d-wave gap admixtures, in agreement with earlier penetration depth data.