Electronic structure of CaFe2As2: Contribution of itinerant Fe 3d-states to the Fermi Level

TL;DR

This study combines DFT calculations and X-ray spectroscopy to show that Fe 3d-states dominate the Fermi level in CaFe2As2, indicating itinerant electrons and suggesting a minimal model for superconductivity in FeAs systems.

Contribution

It provides a combined theoretical and experimental analysis demonstrating the dominant role of Fe 3d-states at the Fermi level in CaFe2As2, supporting a minimal model for superconductivity.

Findings

Fe 3d-states dominate the Fermi level

Fe 3d-electrons exhibit itinerant character

Superconductivity can be modeled with Fe 3d-bands near the Fermi level

Abstract

We present density functional theory (DFT) calculations and a full set of X-ray spectra (resonant inelastic X-ray scattering and X-ray photoelectron spectra) measurements of single crystal CaFe2As2. The experimental valence band spectra are consistent with our DFT calculations. Both theory and experiment show that the Fe 3d-states dominate the Fermi level and hybridize with Ca 3d-states. The simple shape of Xray photoelectron (XPS) Fe 2p-core level spectrum (without any satellite structure typical for correlated systems) suggests itinerant character of the Fe 3d-electrons. Based on the similarity of the calculated and experimental Fe 3d-states distribution in LaOFeAs and CaFe2As2 we conclude that superconductivity in the FeAs-systems can be described within a minimal model, taking into account only Fe 3d-bands close to the Fermi level.