Phenomenological model of the microwave surface impedance of high-T c superconducting films

The model of the microwave surface impedance of thin HTS films is based on a modified two-fluid approach and includes the phenomenological description of the normal and superconducting carrier density and the relaxation time of the normal carriers. A correlation between the London penetration depth at T=0 and the model parameter, which is responsible for the temperature dependence of the superconducting carrier density, was found from numerous experimental data. This correlation allows developing the phenomenological model of the HTS film surface impedance with minimal number of the fitting parameters: the transition temperature T_c, the normal conductivity at T=T_c, the residual resistance parameter, and the exponent describing the temperature dependence of the superconducting carrier density. The validity of the model was verified by a comparison with experimental data