RKKY interaction in SDW phase of iron-based superconductors

TL;DR

This paper investigates the RKKY interaction in iron-based superconductors, revealing how magnetic order and Fermi surface structure influence the interaction's anisotropy and strength.

Contribution

It provides a theoretical analysis of the RKKY interaction in the SDW phase, highlighting the anisotropic XXZ model and dependence on AF gap and Fermi surface folding.

Findings

In the normal state, the RKKY interaction is spin isotropic and influenced by Fermi surface nesting.

In the AF state, the interaction becomes anisotropic, described by an XXZ-type Heisenberg model.

The anisotropy strength depends on the AF gap size and Fermi surface structure.

Abstract

Using the multiband model we analyze the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the magnetic impurities in layered ferropnictide superconductors. In the normal state the interaction is spin isotropic and is dominated by the nesting features of the electron and hole bands separated by the antiferromagnetic momentum, ${\bf Q}_{AF}$. In the AF state the RKKY interaction maps into an effective anisotropic XXZ-type Heisenberg exchange model. The anisotropy originates from the breaking of the spin-rotational symmetry induced by the AF order and its strength depends on the size of the AF gap and the structure of the folded Fermi surface. We discuss our results in connection to the recent experiments.