On the electronic structure of electron doped LaOFeAs as seen by X-ray absorption spectroscopy

TL;DR

This study uses X-ray absorption spectroscopy to analyze the electronic structure of electron-doped LaOFeAs, revealing insights into its covalency, charge transfer, and the effects of doping on its spectra.

Contribution

It provides detailed spectroscopic analysis of LaOFeAs, determining key electronic parameters and the role of covalency and doping effects, with comparison to theoretical calculations.

Findings

Good agreement between XAS data and LDA calculations.

Hubbard U limited to values not significantly larger than 1 eV.

System exhibits high covalency with many ligand holes.

Abstract

We investigated the recently found superconductor LaO_{1-x}F_xFeAs by X-ray absorption spectroscopy (XAS). From a comparison of the O K-edge with LDA calculations we find good agreement and are able to explain the structure and changes of the spectra with electron doping. An important result from this edge is a limitation of the Hubbard U to values not significantly larger than 1 eV. From experimental Fe L_2,3-edge spectra and charge transfer multiplet calculations we gain further information on important physical values such as hopping parameters, the charge transfer energy Delta, and the on-site Hubbard U. Furthermore we find the system to be very covalent with a large amount of ligand holes. A shift in the chemical potential is visible in the O K- and Fe L_2,3-edge spectra which emphasizes the importance of band effects in these compounds.