Experiments on high-quality, high-T-c single crystals show a large and broa
d peak in the real part of the complex microwave conductivity sigma(s)(T) =
sigma(1)(T) - i sigma(2)(T) below the transition temperature T-c. This pea
k in sigma(1)(T) is analyzed in the framework of a two-fluid model proposed
by the authors. Agreement between theory and experiments on Bi2Sr2CaCu2O8
crystals by the Cambridge and other groups is found if the experimental res
idual resistance R-res = R-s(T --> 0) is taken into account in evaluating s
igma(1) from the microwave surface resistance data R-s(T). (C) 2000 Elsevie
r Science B.V. All rights reserved.