Conductivity anisotropy and pseudogap in the microwave response of high-Tc superconductors
Institute of Solid State Physics, Russian Academy of Sciences, Akademika Osip'yana str. 2, Chernogolovka, Moscow Region, 142432, Russian Federation
Results of investigating the temperature dependences of the surface impedance Z(T) = R(T) + iX(T) and complex
conductivity σ(T) = σ’(T)-iσ’’(T) in the ab-planes and
along the c-axis of high-Tc superconductors (HTSCs) are reviewed and critically analyzed. An electrodynamic method is
considered for extracting all components of σ(T) and Z(T) tensors from quantities measured in microwave experiments.
The main attention is focused on the evolution of Z(T) and
σ(T) dependences in a YBa2Cu3O7-x crystal with the oxygen
content variation. Possible mechanisms of conductivity are discussed in the framework of models for normal, superconducting, and pseudogap states of HTSCs.