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Phys. Rev. Lett. 91, 127006 (2003) [4 pages]

Anomalous Coherence Peak in the Microwave Conductivity of c-Axis Oriented MgB2 Thin Films

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B. B. Jin1, T. Dahm2, A. I. Gubin3, Eun-Mi Choi4, Hyun Jung Kim4, Sung-IK Lee4, W. N. Kang5, and N. Klein1
1Forschungszentrum Jülich GmbH, Institute of Thin Films and Interfaces, D-52425 Jülich, Germany
2Universität Tübingen, Institut für Theoretische Physik, Auf der Morgenstelle 14, 72076 Tübingen, Germany
3Usikov Institute of Radiophysics and Electronics, NAS of Ukraine, 12 Acad. Proskura Str., 61085 Kharkov, Ukraine
4National Creative Research Initiative Center for Superconductivity, Department of Physics, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea
5Department of Physics, Pukyung National University, Pusan, 608-737, Korea

Received 31 March 2003; published 19 September 2003

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 MgB2 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 MgB2. Our model assumes there is no interband impurity scattering and a weak interband pairing interaction, as suggested by band structure 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.

© 2003 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.91.127006
DOI:
10.1103/PhysRevLett.91.127006
PACS:
74.25.Fy, 74.25.Nf, 74.70.Ad
 
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