Excitonic spin density wave state in iron pnictides

TL;DR

This paper investigates how excitonic instabilities lead to spin density waves in iron pnictides, highlighting the influence of band structure details and crystal distortions on magnetic order stability.

Contribution

It introduces a realistic four-band model to analyze the excitonic origin of spin density waves and the effects of structural distortions on magnetic stability.

Findings

Magnetic state is highly sensitive to band structure details.

Orthorhombic distortion enhances antiferromagnetic order.

Excitonic instability can explain spin density wave formation.

Abstract

We examine the appearance of a spin density wave in the FeAs parent compounds due to an excitonic instability. Using a realistic four-band model, we show that the magnetic state depends very sensitively upon the details of the band structure. We demonstrate that an orthorhombic distortion of the crystal enhances the stability of the antiferromagnetic order.