Change of the vortex core structure in two-band superconductors at impurity-scattering-driven $s_\pm/s_{++}$ crossover

TL;DR

This paper investigates how impurity scattering causes a transition in vortex core structures in two-band superconductors, revealing the formation of moat-like profiles near the $s_ ext{±}$ to $s_{++}$ crossover.

Contribution

It uncovers a novel vortex core transition involving circular nodal lines and moat-like profiles driven by impurity scattering in two-band superconductors.

Findings

Vortex cores develop circular nodal lines near the crossover.

Moat-like profiles form in one superconducting gap.

Transitions occur near the $s_ ext{±}$ to $s_{++}$ crossover.

Abstract

We report a nontrivial transition in the core structure of vortices in two-band superconductors as a function of interband impurity scattering. We demonstrate that, in addition to singular zeros of the order parameter, the vortices there can acquire a circular nodal line around the singular point in one of the superconducting components. It results in the formation of the peculiar "moat"-like profile in one of the superconducting gaps. The moat-core vortices occur generically in the vicinity of the impurity-induced crossover between $s_{\pm}$ and $s_{++}$ states.