Spin and Charge Dynamics Ruled by Antiferromagnetic Order in Iron Pnictides

TL;DR

This paper investigates the spin and charge excitations in antiferromagnetic iron pnictides using mean-field and RPA calculations, successfully reproducing experimental spin-wave spectra and predicting charge dynamics for RIXS.

Contribution

It introduces a five-band itinerant model with RPA to accurately simulate spin and charge excitations in iron pnictides, highlighting the importance of a particle-hole gap.

Findings

Reproduces spin-wave dispersions observed in neutron scattering.

Predicts the disappearance of spin waves at different energies in LaFeAsO and CaFe$_2$As$_2$.

Analyzes charge dynamics to guide RIXS experiments.

Abstract

We examine the spin and charge excitations in antiferromagnetic iron pnictides by mean-field calculations with a random phase approximation in a five-band itinerant model. The calculated excitation spectra reproduce well spin-wave dispersions observed in inelastic neutron scattering, with a realistic magnetic moment for CaFe$_2$As$_2$. A particle-hole gap is found to be crucial to obtain consistent results; we predict the spin wave in LaFeAsO disappears at a lower energy than in CaFe$_2$As$_2$. We analyze that the charge dynamics to make predictions for resonant inelastic x-ray scattering spectra.