A high resolution, hard X-ray photoemission investigation of BaFe${}_2$As${}_2$: moderate influence of the surface and evidence for a low degree of Fe 3d - As 4p hybridization of the near-E${}_F$ electronic states

Abstract

Photoemission data taken with hard X-ray radiation on cleaved single crystals of the barium parent compound of the MFe${}_2$As${}_2$ pnictide high temperature superconductor family are presented. Making use of the increased bulk-sensitivity upon hard X-ray excitation, and comparing the results to data taken at conventional VUV photoemission excitation energies, it is shown that the BaFe${}_2$As${}_2$ cleavage surface provides an electrostatic environment that is slightly different to the bulk, most likely in the form of a modified Madelung potential. However, as the data argue against a different surface doping level, and the surface-related features in the spectra are by no means as dominating as seen in systems such as YBa${}_2$Cu${}_3$O${}_x$, we can conclude that the itinerant, near-E${}_F$ electronic states are almost unaffected by the existence of the cleavage surface. Furthermore, exploiting the strong changes in photoionisation cross section between the Fe and As states across the wide photon energy range employed, it is shown that the degree of energetic overlap between the iron 3d and arsenic 4p valence bands is particularly small at the Fermi level, which can only mean a very low degree of hybridization between the Fe 3d and As 4p states near and at E${}_F$. Consequently, the itinerancy of the charge carriers in this group of materials involves mainly the Fe 3d - Fe 3d overlap integrals with at best a minor role for the Fe 3d - As 4p hopping parameters, and that the states which support superconductivity upon doping are essentially of Fe 3d character.

8 pages, 3 figures

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• Theory of the Magnetic Moment in Iron Pnictides
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Cited by in corpus (12)

• Classification of the electronic correlation strength in the Fe-pnictides: The case of the parent compound BaFe2As2
• The cleavage surface of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) superconductors: from diversity to simplicity
• Nanoscale superconducting gap variations, strong coupling signatures and lack of phase separation in optimally doped BaFe1.86Co0.14As2
• Electron-Hole Asymmetry in Superconductivity of Pnictides Originated from the Observed Rigid Chemical Potential Shift
• Dynamical correlations and screened exchange on the experimental bench: spectral properties of the cobalt pnictide BaCo2As2
• Dynamical Screening Effects in Correlated Electron Materials -- A Progress Report on Combined Many-Body Perturbation and Dynamical Mean Field Theory: "GW+DMFT"
• Probing the role of Co substitution in the electronic structure of iron-pnictides
• Effect of 3d-doping on the electronic structure of BaFe2As2
• Electronic Structure of CeFeAsO1-xFx (x=0, 0.11/x=0.12) compounds
• Pseudogap-less high T${}_c$ superconductivity in BaCo${}_x$Fe${}_{2-x}$As${}_2$
• Presence of magnetic excitations in SmFeAsO
• Electronic inhomogeneities in the superconducting phase of CaFe1.96Ni0.04As2 single crystals