Nodal Spin Density Wave and band topology of the FeAs based materials

TL;DR

This paper investigates the nodal spin density wave and topological band features in FeAs-based materials, revealing that the SDW state remains gapless due to topological band structure effects, with implications for modeling these materials.

Contribution

It demonstrates that the SDW state in FeAs-based materials cannot be fully gapped because of topological band structure features, using both simplified and realistic models.

Findings

SDW state remains gapless due to topological band structure

Node positions differ between models and can validate models

Topological features influence SDW and superconductivity transition

Abstract

The recently discovered FeAs-based materials exhibit a $(\pi,0)$ Spin Density Wave (SDW) in the undoped state, which gives way to superconductivity upon doping. Here we show that due to an interesting topological feature of the band structure, the SDW state cannot acquire a full gap. This is demonstrated within the SDW mean-field theory of both a simplified two band model and a more realistic 5-band model. The positions of the nodes are different in the two models and can be used to detected the validity of each model.