Anisotropic critical fields of MgB2 single crystals

TL;DR

This paper introduces a model with two anisotropic energy gaps to better explain the temperature-dependent anisotropy in the critical fields and magnetic properties of MgB2 superconductors, addressing limitations of previous models.

Contribution

It proposes a novel two-gap anisotropic model that accurately describes the peculiar temperature-dependent anisotropy in MgB2 superconductors.

Findings

Model explains temperature-dependent anisotropy in H_c2

Model accounts for anisotropic magnetic penetration depth

Describes peculiar properties of MgB2 revealed by single crystals

Abstract

The recently discovered superconductivity in MgB2 has created the world sensation. In spite of the relatively high superconducting transition temperature Tc=39K, the superconductivity is understood in terms of rare two gap superconductor with energy gaps attached to the sigma- and pi-band. However, this simple model cannot describe the temperature dependent anisotropy in H_c2 or the temperature dependence of the anisotropic magnetic penetration depth. Here we propose a model with two anisotropic energy gaps with different shapes. Indeed the present model describes a number of pecularities of MgB2 which have been revealed only recently through single crystal MgB2.