Role of Dirac cones in the anisotropic properties associated with the spin-density wave state of iron pnictides

TL;DR

This paper shows that Dirac cones near the Fermi level significantly contribute to the anisotropic electronic properties in the spin-density wave state of iron pnictides, beyond the traditional symmetry-breaking explanation.

Contribution

It introduces a minimal two-orbital model highlighting the role of Dirac cones in anisotropic properties of iron pnictides' SDW state, supported by optical and quasiparticle interference analyses.

Findings

Dirac cones contribute significantly to anisotropy in SDW state

Optical conductivity reveals Dirac cone effects

Low-energy spin-wave excitations are influenced by Dirac semimetallic state

Abstract

The origin of unusual anisotropic electronic properties in the spin-density wave state of iron pnictides has conventionally been attributed to the breaking of four-fold rotational symmetry associated with the collinear magnetic order. By using a minimal two-orbital model, we show that a significant portion of the contribution to the anisotropy may come from the Dirac cones, which are not far away from the Fermi level. We demonstrate this phenomenon by examining optical conductivity and quasiparticle interference in the Dirac-semimetallic state with spin-density wave order, and the latter can be obtained by choosing appropriate interaction parameters and orbital splitting between the $d_{xz}$ and $d_{yz}$ orbitals. We further extend this study to investigate the low-energy spin-wave excitations in the Dirac-semimetallic state with spin-density wave order.