Upper critical field in dirty two-band superconductors: Breakdown of the anisotropic Ginzburg-Landau theory

A. A. Golubov and A. E. Koshelev
Phys. Rev. B 68, 104503 – Published 4 September 2003
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Abstract

We investigate the upper critical field in a dirty two-band superconductor within quasiclassical Usadel equations. The regime of very high anisotropy in the quasi-2D band, relevant for MgB2, is considered. We show that strong disparities in pairing interactions and diffusion constant anisotropies for two bands influence the in-plane Hc2 in a different way at high and low temperatures. This causes temperature-dependent Hc2 anisotropy, in accordance with recent experimental data in MgB2. The three-dimensional band most strongly influences the in-plane Hc2 near Tc, in the Ginzburg-Landau (GL) region. However, due to a very large difference between the c-axis coherence lengths in the two bands, the GL theory is applicable only in an extremely narrow temperature range near Tc. The angular dependence of Hc2 deviates from a simple effective-mass law even near Tc.

  • Received 11 March 2003

DOI:https://doi.org/10.1103/PhysRevB.68.104503

©2003 American Physical Society

Authors & Affiliations

A. A. Golubov

  • Faculty of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands

A. E. Koshelev

  • Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439

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Vol. 68, Iss. 10 — 1 September 2003

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