Phenomenological description of the microwave surface impedance and complex conductivity of High-T-c single crystals

Measurements of the microwave surface impedance Z(s)(T) = R-s(T) + iX(s)(T) and the complex conductivity sigma (s)(T) in the ab-plane of high-quality high-T-c YBCO, BSCCO, TBCCO, and TBCO single crystals are analyzed. Experim ental data of Z(s)(T) and sigma (s)(T) are compared with calculations based on a modified two-fluid model that includes a temperature-dependent quasip article scattering and a unique temperature variation of the density of sup erconducting carriers. We describe the agreement and disagreement of our an alysis with the salient features of the experimental data. We review the ex isting microscopic models based on unconventional symmetry types of the ord er parameter and on novel quasiparticle relaxation mechanisms. (C) 2000 MAI K "Nauka/Interperiodica".