Orbital Ordering and Jahn-Teller Distortion in Perovskite RuthenateSrRuO3

Local density approximation plus on-site Coulomb interaction $U$ band structure calculations reveal that ${\mathrm{SrRuO}}_3$ exhibits a half-metallic ground state with an integer spin moment of $2.0{\mu }_B/{\mathrm{SrRuO}}_3$. An associated tilting $4d{t}_{2g}$ orbital ordering on a Ru sublattice is observed under the on-site Coulomb interaction $U$ in the presence of lattice distortion. This finding unravels the on-site Coulomb correlation as the driving force of the $4d$ orbital ordering and Jahn-Teller distortion as well as of the half-metallic ground state.