Fermi Surface Topology and the Upper Critical Field in Two-Band Superconductors: Application to MgB2
T. Dahm, N. Schopohl
DOI 10.1103/PhysRevLett.91.017001 · Physical Review Letters
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Abstract
Recent measurements of the anisotropy of the upper critical field Bc2 on MgB2 single crystals have shown a puzzling strong temperature dependence. Here, we present a calculation of the upper critical field based on a detailed modeling of band structure calculations that takes into account both the unusual Fermi surface topology and the two gap nature of the superconducting order parameter. Our results show that the strong temperature dependence of the Bc2 anisotropy can be understood as an interplay of the dominating gap on the σ band, which possesses a small c-axis component of the Fermi velocity, with the induced superconductivity on the π-band possessing a large c-axis component of the Fermi velocity. We provide analytic formulas for the anisotropy ratio at T=0 and T=Tc and quantitatively predict the distortion of the vortex lattice based on our calculations.
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. | 39 | Pressure not reported | unknown |
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