Rotation of Triangular Vortex Lattice in the Two-Band Superconductor MgB2

TL;DR

This paper develops a theoretical method combining Eilenberger theory and first-principles calculations to explain vortex lattice orientation transitions in MgB2, revealing the influence of multiband effects and anisotropy.

Contribution

It introduces a novel approach to analyze vortex lattice configurations in multiband superconductors using microscopic electronic structure data.

Findings

Successive vortex lattice orientation transitions explained by multiband effects.

Reentrant transition at low temperature linked to Fermi velocity anisotropy.

Characteristic field dependence of vortex lattice in MgB2 demonstrated.

Abstract

To identify the contributions of the multiband nature and the anisotropy of a microscopic electronic structure to a macroscopic vortex lattice morphology, we develop a method based on the Eilenberger theory near Hc2 combined with the first-principles band calculation to estimate the stable vortex lattice configuration. For a typical two-band superconductor MgB2, successive transitions of vortex lattice orientation that have been observed recently by small angle neutron scattering [Das, et al.: Phys. Rev. Lett. 108 (2012) 167001] are explained by the characteristic field-dependence of twoband superconductivity and the competition of sixfold anisotropy between the sigma- and pi-bands. The reentrant transition at low temperature reflects the Fermi velocity anisotropy of the sigma-band.