Upper critical field in dirty two-band superconductors: Breakdown of the anisotropic Ginzburg-Landau theory
A. A. Golubov, A. E. Koshelev
DOI 10.1103/PhysRevB.68.104503 · Physical Review B
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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.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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