Anisotropy of the upper critical field in superconductors with anisotropic gaps. Anisotropy parameters of MgB2

TL;DR

This paper models the anisotropic upper critical field in MgB2 superconductors using a two-band approach, showing how the anisotropy ratio varies with temperature in agreement with experimental data.

Contribution

It introduces a two-band model with realistic Fermi surface parameters to analyze the anisotropy of Hc2 in MgB2, providing insights into its temperature dependence.

Findings

Hc2 anisotropy ratio increases as temperature decreases.

Model aligns well with experimental measurements.

Two-band effects are crucial for understanding MgB2's anisotropic properties.

Abstract

The upper critical field Hc2 is evaluated for weakly-coupled two-band superconductors. By modeling the actual bands and the gap distribution of MgB2 by two Fermi surface spheroids with average parameters of the real material, we show that H_{c2,ab}/H_{c2,c} increases with decreasing temperature in agreement with available data.