Penetration depth in a mixed-wave superconductor

We have calculated the penetration depth in a mixed-wave superconductor. At low temperatures the ground state has d(x2-y2) symmetry which at elevated temperatures becomes of the type of s wave. We have used the experimental measurements of the surface resistance of Bi2Sr2CaCu2O8+delta crystals of T-c similar or equal to 82 K at microwave frequencies to extract the London penetration depth as a function of temperature. It is found that the experimental data is consistent with the interpretation of d(x2-y2) wave at low temperatures becoming s wave at high temperatures. The d(x2-y2) fis wave is estimated to start changing over to s at a temperature of similar or equal to 40 K. The theoretically calculated values of the penetration depth as a function of temperature are in reasonable agreement with those extracted from the experimental measurements.