Two-peak temperature dependence of microwave surface impedance of single-crystalline YBCO thin films : Role of pairing symmetry and defect structure

Temperature dependencies of microwave surface impedance were measured for c-oriented highly perfect YBCO thin films deposited by off-axis dc magnetron sputtering onto CeO2-buffered r-cut sapphire substrates. A distinct two-peak structure of R s(T) and X s(T) dependencies with peaks at 28-30, K and 5...

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Bibliographic Details
Published in:Journal of superconductivity and novel magnetism 2006-11, Vol.19 (7-8), p.561-569
Main Authors: PAN, V. M, KASATKIN, A. L, KOMASHKO, V. A, TRETIATCHENKO, C. G, IVANYUTA, O. M, MELKOV, G. A
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Exact sciences and technology
Physics
Properties of type I and type II superconductors
Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.)
Superconductivity
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Summary:Temperature dependencies of microwave surface impedance were measured for c-oriented highly perfect YBCO thin films deposited by off-axis dc magnetron sputtering onto CeO2-buffered r-cut sapphire substrates. A distinct two-peak structure of R s(T) and X s(T) dependencies with peaks at 28-30, K and 50, K has been revealed. The peaks become smeared at higher frequencies or in applied dc magnetic field, while the peak positions remain almost unchanged. The two-peak Z s(T) behavior is believed to be an intrinsic electron property of extremely perfect quasi-single-crystalline YBCO films. A theoretical model is suggested to explain the observed anomalous Z s(T) behavior. The model is based on the Boltzman kinetic equation for quasiparticles in layered high-T c superconductors (HTS) cuprates. It takes into account the supposed s + d wave symmetry of electron pairing and strong energy-dependent relaxation time of quasiparticles, determined mainly by their elastic scattering on extended defects parallel to the c-axis.
ISSN:1557-1939
1557-1947
DOI:10.1007/s10948-006-0225-0