Renormalization of f levels away from the Fermi energy in electron excitation spectroscopies: Density-functional results for Nd2-xCexCuO4

T. Jarlborg, University of Geneva
B. Barbiellini, Northeastern University
H. Lin, Northeastern University
R. S. Markiewicz, Northeastern University
A. Bansil, Northeastern University

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Originally published in Physical Review B v.84 (2011): 045109. DOI: 10.1103/PhysRevB.84.045109

Abstract

Relaxation energies for photoemission where an occupied electronic state is excited and for inverse photoemission where an empty state is filled are calculated within the density-functional theory with application to Nd₂₋ₓCeₓCuO₄. The associated relaxation energies are obtained by computing differences in total energies between the ground state and an excited state in which one hole or one electron is added into the system. The relaxation energies of f electrons are found to be of the order of several eV’s, indicating that f bands will appear substantially away from the Fermi energy (E_F) in their spectroscopic images, even if these bands lie near E_F. Similar shifts are obtained for the Gd-f states in Gd₂CuO₄. Our analysis explains why it would be difficult to observe f electrons at the E_F even in the absence of strong electronic correlations.