Origin of electronic dimers in the spin-density wave phase of Fe-based superconductors

TL;DR

This paper explains how impurity-induced electronic dimers form in the spin-density wave phase of iron-based superconductors, revealing their structure, orientation, and role in transport anisotropy, consistent with experimental observations.

Contribution

It demonstrates that impurity-induced magnetic nematogens naturally form dimer structures aligned with the antiferromagnetic axis, explaining transport anisotropy in these materials.

Findings

Electronic dimers match experimental lengths (~10 lattice constants).

Nematogens are oriented along the antiferromagnetic a-axis.

Impurities induce stable magnetic unidirectional structures.

Abstract

We investigate the emergent impurity-induced states arising from point-like scatterers in the spin-density wave phase of iron-based superconductors within a microscopic five-band model. Independent of the details of the band-structure and disorder potential, it is shown how stable magnetic (pi,pi) unidirectional nematogens are formed locally by the impurities. Interestingly, these nematogens exhibit a dimer structure in the electronic density, are directed along the antiferromagnetic a-axis, and have typical lengths of order 10 lattice constants in excellent agreement with recent scanning tunnelling experiments. These electronic dimers provide a natural explanation of the dopant-induced transport anisotropy found e.g. in the 122 iron pnictides.