Anomalous microwave conductivity coherence peak in c-axis MgB2 thin film
/ Authors
B. Jin, T. Dahm, A. Gubin, E. Choi, Hyun Jung Kim, Sung-Ik Lee, W.N.Kang, N. K. ISG-2, Forschungszentrum Juelich GmbH, Juelich
and 13 more authors
Germany University Tuebingen, I. Physik, Germany Usikov Institute of Radiophysics, Electronics, Kharkov, Ukraine National Creative Research Initiative Center for Superconductivity, D. Physics, Pohang University of Science, Technology, K. D. O. Physics, Pukyung National University, Pusan, Korea
/ Abstract
----The temperature dependence of the real part of the microwave complex conductivity at 17.9 GHz obtained from surface impedance measurements of two c-axis oriented MgB 2 thin films reveals a pronounced maximum at a temperature around 0.6 times the critical temperature. Calculations in the frame of a two-band model based on Bardeen-Cooper-Schrieffer (BCS) theory suggest that this maximum corresponds to an anomalous coherence peak resembling the two-gap nature of MgB 2 . Our model assumes there is no interband impurity scattering and a weak interband pairing interaction, as suggested by bandstructure calculations. In addition, the observation of a coherence peak indicates that the π -band is in the dirty limit and dominates the total conductivity of our films.