Electronic correlations in epitaxial CrN thin film

Chromium nitride (CrN) spurred enormous interest due to its coupled magnetostructural and unique metal-insulator transition. The underneath electronic structure of CrN remains elusive. Herein, the electronic structure of epitaxial CrN thin film has been explored by employing resonant photoemission spectroscopy (RPES) and X-ray absorption near edge spectroscopy study in combination with the first-principles calculations. The RPES study indicates the presence of a charge-transfer screened 3[Formula: see text] ([Formula: see text] : hole in the N-2[Formula: see text] ) and 3[Formula: see text] final-states in the valence band regime. The combined experimental electronic structure along with the orbital resolved electronic density of states from the first-principles calculations reveals the presence of Cr(3[Formula: see text] )-N(2[Formula: see text] ) hybridized (3[Formula: see text] ) states between lower Hubbard (3[Formula: see text] ) and upper Hubbard (3[Formula: see text] ) bands with onsite Coulomb repulsion energy (U) and charge-transfer energy ([Formula: see text] ) estimated as [Formula: see text] 4.5 and 3.6 eV, respectively. It verifies the participation of ligand (N-2[Formula: see text] ) states in low energy charge fluctuations and provides concrete evidence for the charge-transfer ([Formula: see text] U) insulating nature of CrN thin film.