Anomalous coherence peak in the microwave conductivity of c-axis oriented MgB2 thin films.
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 pi band is in the dirty limit and dominates the total conductivity of our films.
Jin
B B
BB
Forschungszentrum Jülich GmbH, Institute of Thin Films and Interfaces, D-52425 Jülich, Germany.
Dahm
T
T
Gubin
A I
AI
Choi
Eun-Mi
EM
Kim
Hyun Jung
HJ
Lee
Sung-Ik
SI
Kang
W N
WN
Klein
N
N