Electronic correlations in epitaxial CrN thin film

Abstract

AbstractChromium 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$$d ^n{\underline{L}}$$ d n L ̲ ($$L$$ L : hole in the N-2$$p$$ p ) and 3$$d ^{n-1}$$ d n - 1 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$$d$$ d )-N(2$$p$$ p ) hybridized (3$$d ^n{\underline{L}}$$ d n L ̲ ) states between lower Hubbard (3$$d ^{n-1}$$ d n - 1 ) and upper Hubbard (3$$d ^{n+1}$$ d n + 1 ) bands with onsite Coulomb repulsion energy (U) and charge-transfer energy ($$\Delta$$ Δ ) estimated as $$\approx$$ ≈  4.5 and 3.6 eV, respectively. It verifies the participation of ligand (N-2$$p$$ p ) states in low energy charge fluctuations and provides concrete evidence for the charge-transfer ($$\Delta<$$ Δ < U) insulating nature of CrN thin film.