Microwave surface impedance of Y1Ba2Cu3O7 − δ crystals: Experiment and comparison to a d-wave model

Abstract We present measurements of the microwave surface resistance R s and the penetration depth λ of Y 1 Ba 2 Cu 3 O 7 − δ crystals. At low T , λ ( T ) obeys a polynomial behavior, while R s displays a characteristic non-monotonic T -dependence. A detailed comparison of the experimental data is made to a model of d -wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to π 2 and a strong coupling value of the gap parameter 2Δ(0) kT c ~ 6 is needed. On the experimental side the uncertainties regarding the material parameters λ(0) and R s , res (0) further complicate a quantitative comparison. For one sample, R s , res (0) agrees with the intrinsic value which results from the d -wave model.