Phenomenological description of "coherence peak" of high-Tc superconductors by improved three-fluid model

So-called "coherence peak" of real part of complex conductivity for low-Tc superconductors, which is expected by BCS theory, was observed experimentally by the dielectric resonator method for high-Tc superconductors. This peak can be explained phenomenologically by an improved three-fluid model, where the momentum relaxation time is assumed to depend on temperature both in the superconducting and normal states.