Electronic state around vortex in a two-band superconductor

TL;DR

This paper uses quasiclassical theory to analyze vortex states in a two-band superconductor with different gap sizes and Fermi surface geometries, revealing anisotropic behaviors and field-dependent density of states.

Contribution

It provides a detailed theoretical investigation of vortex states in a two-band superconductor considering Fermi surface geometry and anisotropy effects.

Findings

Field dependence of zero-energy density of states varies with field orientation.

Vortex core shape exhibits anisotropy depending on field direction.

Fermi surface geometry influences the electronic state behavior at high fields.

Abstract

Based on the quasiclassical theory, we investigate the vortex state in a two-band superconductor with a small gap on a three dimensional Fermi surface and a large gap on a quasi-two dimensional one, as in MgB_2. The field dependence of zero-energy density of states is compared for fields parallel and perpendicular to the ab plane, and the anisotropy of the vortex core shape is discussed for a parallel field. The Fermi surface geometry of two-bands, combining the effect of the normal-like electronic state on the small gap band at high fields, produces characteristic behavior in the anisotropy of c- and ab-directions.