Electronic structure of CeCu4In from band structure calculations and X-ray photoelectron spectroscopy

We present a combined new experimental and theoretical study of the electronic structure for the heavy fermion CeCu ₄In based on X-ray photoelectron spectroscopy (XPS) data and ab-initio band structure calculations. The compound crystallizes in the orthorhombic CeCu _4.38In _1.62 type of structure (space group Pnnm). Below the Fermi energy the total density of states contains mainly 3d–states of Cu atoms that hybridized with the Ce 4f electronic states. The Ce core-level XPS spectra point to a stable trivalent configuration of Ce atoms in CeCu ₄In, consistently with the magnetic susceptibility data. For more detailed information about electronic states the fully relativistic band structure was calculated within the density functional theory (DFT) for the first time. Based on these calculations we present calculated photoemission spectra, which very well reproduce the experimental ones. The Fermi level is located at a deep decrease in the density of electronic states and reaches a value of 3.69 states/(eV f.u.). This value is much smaller than the one obtained experimentally, which indicates the importance of many-body effects, which are not properly taken into account in ab-initio calculations. The valence band is formed mainly by Cu( 3d) electrons with a small contribution of Ce( 4f) electrons in the immediate vicinity of the Fermi level.