%0 Journal Article
%A Rogge, Paul C.
%A Chandrasena, Ravini U.
%A Cammarata, Antonio
%A Green, Robert J.
%A Shafer, Padraic
%A Lefler, Benjamin M.
%A Huon, Amanda
%A Arab, Arian
%A Arenholz, Elke
%A Lee, Ho Nyung
%A Lee, Tien-Lin
%A Nemsak, Slavomir
%A Rondinelli, James M.
%A Gray, Alexander X.
%A May, Steven J.
%T Electronic structure of negative charge transfer CaFeO 3 across the metal-insulator transition
%J Physical review materials
%V 2
%N 1
%@ 2475-9953
%C College Park, MD
%I APS
%M FZJ-2019-00554
%P 015002
%D 2018
%X We investigated the metal-insulator transition for epitaxial thin films of the perovskite CaFeO3, a material with a significant oxygen ligand hole contribution to its electronic structure. We find that biaxial tensile and compressive strain suppress the metal-insulator transition temperature. By combining hard x-ray photoelectron spectroscopy, soft x-ray absorption spectroscopy, and density functional calculations, we resolve the element-specific changes to the electronic structure across the metal-insulator transition. We demonstrate that the Fe sites undergo no observable spectroscopic change between the metallic and insulating states, whereas the O electronic configuration undergoes significant changes. This strongly supports the bond-disproportionation model of the metal-insulator transition for CaFeO3 and highlights the importance of ligand holes in its electronic structure. By sensitively measuring the ligand hole density, however, we find that it increases by ∼5–10% in the insulating state, which we ascribe to a further localization of electron charge on the Fe sites. These results provide detailed insight into the metal-insulator transition of negative charge transfer compounds and should prove instructive for understanding metal-insulator transitions in other late transition metal compounds such as the nickelates.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000423527600003
%R 10.1103/PhysRevMaterials.2.015002
%U https://juser.fz-juelich.de/record/859717