MICROWAVE SURFACE IMPEDANCE OF Y1BA2CU3O7-DELTA CRYSTALS - EXPERIMENTAND COMPARISON TO A D-WAVE MODEL

We present measurements of the microwave surface resistance R(s) and t he penetration depth lambda of Y1Ba2Cu3O7-delta crystals. At low T, la mbda(T) obeys a polynomial behavior, while R(s) displays a characteris tic non-monotonic T-dependence. A detailed comparison of the experimen tal 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 param eters needed are worth noting. The elastic scattering rate required to at the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to pi/2 and a strong coupling value of the gap parameter 2 Delta(0)/kT(c) similar to 6 is needed. O n the experimental side the uncertainties regarding the material param eters lambda(0) and R(s,res)(0) further complicate a quantitative comp arison. For one sample, R(s,res)(0) agrees with the intrinsic value wh ich results from the d-wave model.