Microwave complex resistivity in YBCO films above Tc: effects of fluctuations

• Published in: Physica. C, Superconductivity Vol. 341-348; pp. 2679 - 2680
• Main Authors: Neri, D., Marcon, R., Rogai, R., Silva, E., Fastampa, R., Giura, M., Sarti, S., Cucolo, A.M., Beneduce, C., Bobba, F., Boffa, M., Cucolo, M.C.
• Format: Journal Article
• Language: English
• Published: 2000
• ISSN: 0921-4534
• DOI: 10.1016/S0921-4534(00)01463-5

Authors present measurements of the (a,b) plane complex resistivity at 24 GHz in nearly optimally doped YBCO films grown by dc sputtering with Tc approx equals 90 K. Attention is focused above Tc, whereAUTHors discuss the data in terms of 3-D, anisotropic fluctuations.AUTHors find that, at microwave frequencies, simple Gaussian fluctuations are unable to describe the data both above and in the vicinity of Tc. The discrepancy above Tc is recovered by including a short-wavelength cutoff in the frequency-dependent fluctuational conductivity. In order to follow the slowing down of the fluctuations at Tc, Authors treat the region close to Tc including the quartic term of the order parameter in the Ginzburg-Landau functional within the Hartree approximation. Authors then find agreement with data from high temperature (T = 1.3 Tc) down to Tc. 6 refs.