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

Abstract

Absi'ruct-The surface resistance R(T,o) at 10 and 145 GHz is obtained experimentally between 4 and 300 K. In the temperaiture range Ta I T I Tc R(T) is quantitatively fitted by the BCS theory with a mean free path !(T) increasing exponentially below Tc. The e (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 a T w They dominate scattering for C(T) 2 a~~/ 2 . Below Ta the enforced energy transfer from YBCO-crystallites to weak links enhances R(T<Ta) until at T i~ T* the 'weak link surface impedance' dominates R(TIT*) fi: Rres(T).

Microwave surface resistance in MgB2

“…Hence, the temperature dependence of the surface resistance could easily be associated with weak link effects within each grain [34]. However, it is also possible to explain R s (T)∝T in the framework of two-band superconductivity theory with an s-wave order parameter in each band.…”

Synthesis and microwave properties of TI2Ba2CaCu2O8 superconducting films grown by MOCVD

“…Rather, in the past years different mechanisms have been considered, based on magnetic pair interactions, and strong quasiparticle correlations [6,16,29,30].…”

Influence of magnetic impurities on the microwave resistance of overdopedYBa2Cu3OProkhorov1, Kaminsky2, Lee3 2001Phys. Rev. B1000View full textAdd to dashboardCite

“…The weak links act as Josephson junctions of the weakened superconductivity, and the temperature dependence of the surface resistance is governed by the critical Josephson current and the leakage current. 2 The grain or twin boundaries are usually considered as the weak links. However, the maximum on the R s (T) curves is observed for the YBa 2 Cu 3 O 7Ϫ␦ single crystals as well as for the films, prepared by various methods and obviously having different imperfections.…”

“…͑4͒ we used a relation, ⌬ 0 ϭ2.1k B T c0 , which is very often obtained experimentally. 1,2 From Eq. ͑4͒ it follows that the value of the energy gap vanishes in both cases, i.e., when F(T)→0 above the critical temperature and when the term in square brackets becomes zero due to the spin-flip scattering, and then the pairbreaking effect results in a normal state.…”

“…The first of them suggests the existence of weak links such as grain or twin boundaries in the HTSC materials. [1][2][3] The second one is based on the semimicroscopic d-wave model. 4,5 The third takes into account a variety of electron scattering mechanisms.…”