CHARACTERISTIC FEATURES OF THE TEMPERATURE-DEPENDENCE OF THE SURFACE IMPEDANCE OF YBA2CU3O6.95 SINGLE-CRYSTALS

The real and imaginary parts of the surface impedance Z(s)=R-s+iX(s) o f YBa2Cu3O6.95 single crystals are measured at a frequency omega/2 pi= 9.4 GHz. The quantities R-s(T) and X-s(T) are linear functions of temp erature for T<0.3T(c) (T-c=93.5 K). A maximum of R-s(T) and a plateau of X-s(T) are observed in the interval 35<T<65 K. Our experimental dat a, just as all recent measurements of R-s(T) in: YBa2Cu3O6.95 Single c rystals in the temperature range 0<T<1.3T(c), are described well in a two-fluid model which assumes electron-phonon scattering of quasiparti cles. (C) 1997 American Institute of Physics.