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Mixed state in dirty two-band superconductors: application to MgB2

Summary: Mixed state in dirty two-band superconductors:
application to MgB2
A.A. Golubov a,*, A.E. Koshelev b
Department of Applied Physics, Faculty of Science and Technology, University of Twente, P.O. Box 217,
7500 AE Enschede, The Netherlands
Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA
We investigate a two-band superconductor with strong intraband and weak interband electronic scattering rates in
the framework of coupled Usadel equations. We calculate the upper critical field for different field orientation. Due to a
very large difference between the c-axis coherence lengths in two-bands, the GL theory is applicable only in the ex-
tremely narrow temperature range. This leads to the strong temperature dependence of the Hc2 anisotropy and large
deviations of the angular dependence of Hc2 from a simple effective-mass law. In the case of field along c-direction we
solved coupled nonlinear Usadel equations numerically to find field evolution of the pair potentials and local densities
of states for two-bands. The existence of two distinct length and field scales corresponding to different bands is
2004 Elsevier B.V. All rights reserved.
PACS: 74.25.Ha; 74.60.Ec
Keywords: MgB2; Two-band superconductors; Mixed state; Upper critical field


Source: Alexei, Koshelev - Materials Science Division, Argonne National Laboratory


Collections: Materials Science; Physics