Single vortex structure in two models of iron pnictide $s^\pm$ superconductivity

TL;DR

This study investigates the vortex structure in iron pnictide superconductors using two models of $s^$ pairing, revealing how impurities affect local density of states near vortices.

Contribution

It compares continuum and lattice models of $s^$ superconductivity, analyzing vortex core states and impurity effects in iron pnictides.

Findings

LDOS peak at vortex center varies with model and band filling

Impurities near vortex core significantly alter LDOS features

Vortex core states are sensitive to impurity positioning

Abstract

The structure of a single vortex in a FeAs superconductor is studied in the framework of two formulations of superconductivity for the recently proposed sign-reversed $s$ wave ($s^\pm$) scenario: {\it (i)} a continuum model taking into account the existence of an electron and a hole band with a repulsive local interaction between the two; {\it (ii)} a lattice tight-binding model with two orbitals per unit cell and a next-nearest-neighbour attractive interaction. In the first model, the local density of states (LDOS) at the vortex centre, as a function of energy, exhibits a peak at the Fermi level, while in the second model such LDOS peak is deviated from the Fermi level and its energy depends on band filling. An impurity located outside the vortex core has little effect on the LDOS peak, but an impurity close to the vortex core can almost suppress it and modify its position.