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-principle calculations. The RPES study indicates the presence of a charge-transfer screened 3 d n L ( L hole in the N-2 p ) and 3 d n−1 final-states in the valence band regime. The combined experimental electronic band structure along with the orbital resolved electronic density of states from the first-principle calculations reveals the presence of Cr(3 d )-N(2 p ) hybridized (3 d n L ) states between lower Hubbard (3 d n−1 ) and upper Hubbard (3 d n+1 ) bands with onsite Coulomb repulsion energy (U) and charge-transfer energy (Δ) estimated as ≈ 4.5 and 3.6 eV, respectively. It verifies the participation of ligand (N-2 p ) states in low energy charge fluctuations and provides concrete evidence for the charge-transfer (Δ<U) insulating nature of CrN thin film.