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

Golubov, A.A. and Koshelev, A.E. (2003) Upper critical field in dirty two-band superconductors: breakdown of the anisotropic Ginzburg-Landau theory. Physical Review B: Condensed matter and materials physics, 68 (10). p. 104503. ISSN 1098-0121

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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.
Item Type:	Article
Copyright:	© 2003 The American Physical Society
Faculty:	Science and Technology (TNW)
Research Group:	Low Temperatures - Biomagnetism (LT)
Link to this item:	http://purl.utwente.nl/publications/40676
Official URL:	http://dx.doi.org/10.1103/PhysRevB.68.104503
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