Comment on "Nonmagnetic Impurity Resonances as a Signature of Sign-Reversal Pairing in Fe-As-Based Superconductors"

TL;DR

This paper critiques a recent model of Fe-As-based superconductors, arguing that the proposed tight-binding model does not accurately capture the symmetry of the Fe-As planes.

Contribution

It challenges the validity of a recent tight-binding model for Fe-As superconductors, emphasizing the importance of correct symmetry representation.

Findings

The proposed model lacks the necessary symmetry properties.

The critique highlights discrepancies in the model's assumptions.

It underscores the need for accurate symmetry considerations in modeling.

Abstract

In a recent Letter [PRL 103, 186402 (2009)], the energy band structure of Fe-As-based superconductors is fitted with a tight-binding model with two Fe ions per unit cell and two degenerate xz and yz orbitals per Fe ion. The author claims that the proposed model, which differs markedly from a model previously used by other authors for the same two orbitals in the same compounds, possesses the symmetry required to describe the Fe-As planes in iron-pnictide superconductors. In this comment we argue that this is not the case.