First-principles investigation of the metal-insulator transition in rutile RuO2

Abstract

The electronic and magnetic properties of rutile ruthenium dioxide (RuO2) are extensively investigated by employing density functional theory. The material RuO2 is observed as a nonmagnetic metal. The sharing of a single Ru 4d electron by the dyz/xz orbitals is responsible for the metallicity of RuO2. The ground-state properties of this material change significantly upon the application of on-site Coulomb interaction U. RuO2 preserves its nonmagnetic metallic character up to U=3 eV. Nevertheless, RuO2 encounters a first step transition from nonmagnetic metal to a ferromagnetic metal (FM) at U=4 eV. The present system remains in its FM phase till U=5 eV. It exhibits a second step transition from the FM to a half-metallic ferromagnetic phase at U=6 eV. Eventually, RuO2 encounters metal-insulator transition (MIT) at U=7 eV with a band gap of Eg ∼0.3 eV upholding ferromagnetism. It is revealed that the spin polarization arising from the strong dynamical electron correlation due to the application of U is responsible for the metal to half-metal and MIT in RuO2.