Lal, R. and Vajpayee, Arpita and Awana, V. P. S. and Kishan, H. and Awasthi, A. M. (2008) Hump structure below Tc in the thermal conductivity of MgB2 superconductor. Physica C: Superconductivity, 469 (2-3). pp. 106-110. ISSN 0921-4534

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Abstract

A reasonable cause of absence of hump structure in thermal conductivity of MgB2 below the superconducting transition temperature (Tc) lies in the appearance of multigap structure. The gaps of lower magnitude can be suppressed by defects so that this system becomes effectively a single-gap superconductor. When such a situation is created, it is hoped that thermal conductivity (κ) will show hump below Tc. Proceeding along these lines, a sample of MgB2 with a relatively higher residual resistivity ρo = 33.8 μΩ cm has been found to show a hump structure below Tc. The actual electronic thermal conductivity κel of this sample is less than that expected from the Wiedeman–Franz law by more than a factor of 2.6 in the considered temperature range. Modifying the Wiedeman–Franz law for the electronic contribution by replacing the Lorenz number L0 = 2.45 × 10−8 W Ω K−2 by an effective Lorenz number Leff (<L0) we have obtained two sets of κel, namely those with Leff = 0.1L0 and 0.2L0. Corresponding to these two sets of κel, two sets of the phonon thermal conductivity κph are obtained. κph has been analyzed in terms of an extended Bardeen–Rickayzen–Tewordt theory. The main result of this analysis is that the hump structure corresponds to a gap ratio of 3.5, and that large electron-point defect scattering is the main source of drastic reduction of the electronic thermal conductivity from that given by the usual Wiedeman–Franz law.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s Elsevier B.V.
Uncontrolled Keywords:	MgB2; Thermal conductivity
Subjects:	Physics
Divisions:	UNSPECIFIED
Depositing User:	Ms Neetu Chandra
Date Deposited:	03 Sep 2012 07:45
Last Modified:	03 Sep 2012 07:45
URI:	http://npl.csircentral.net/id/eprint/524

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