Temperature dependence of the surface resistance R(T,ω) andmean free path l(T) of YBCO-superconductors

摘要

The surface resistance R(Tω) at 10 and 145 GHz is obtained experimentally between 4 and 300 K. In the temperature range Ta ⩽T⩽Tc R(T) is quantitatively fitted by the BCS theory with a mean free path l(T) increasing exponentially below Tc . The l(T)-increase is related to diminishing plane-chain scattering and is limited at Ta by “inelastic surface scattering” at weak or strong links, e.g., at twin boundaries of an average distance aTW. They dominate scattering for l(T)⩾aTW/2. Below Ta the enforced energy transfer from YBCO-crystallites to weak links enhances R(T