Abstract
Local density approximation plus on-site Coulomb interaction U electronic structure calculations reveal that layered perovskite oxide Sr2RuO4 exhibits the ferromagnetic (FM) half-metallic ground state, which is nearly degenerate with the antiferromagnetic (AFM) phase with a slightly higher total energy. The nearly degenerate FM/AFM total energies provide a reasonable explanation for the experimentally observed spin-fluctuation. In addition, a dumbbell-shape 4d − t2g recombined dxz − dyz orbital ordering on the Ru sublattice is obtained owing to the on-site Coulomb interaction U associated with the elongated RuO6 octahedron local structure. The discovered orbital ordering is robust against the spin-orbit interaction as well as the surface terminations. Our findings unravel the on-site Coulomb correlation as the driving force of the Ru-4d orbital ordering as well as the inherent magnetic degeneracy.
Highlights
Rich physical properties of transition metal oxides, such as electronic, magnetic, and transport properties, is largely connected with the orbital, charge, spin, and lattice degrees of freedom
Polarized dumbbell-shape 4d − t2g recombined dxz − dyz orbital ordering on the Ru sublattice driven by the strongly correlated on-site Coulomb interaction U associated with the elongated RuO6 octahedron local structure
To study the magnetism based on this lattice structure, we consider the nonmagnetic (NM) phase and three possible magnetic configurations, i.e., ferromagnetic (FM), antiferromagnetic 1 (AFM1), and antiferromagnetic 2 (AFM2) as depicted in Fig. 1(b–d), respectively
Summary
Rich physical properties of transition metal oxides, such as electronic, magnetic, and transport properties, is largely connected with the orbital, charge, spin, and lattice degrees of freedom. A first real-space orbital ordering image at the cobalt-terminated surface of the well-studied heavy fermion compound CeCoIn5 is observed by using high accuracy sub-atomic resolution STM16. It is generally believed that this superconducting state has a spin triplet state[24,25,26], which may be chiral p-wave state[27] This makes Sr2RuO4 a potential candidate for intrinsic topological superconductor[28], though debates remain among different experiments[29]. Sr2RuO4 crystallizes in the tetragonal (space group I4/mmm) perovskite structure with 2 f.u. per unit cell[33]. It contains SrO-RuO2-SrO sandwiched layers with a lateral shift between alternative layers. Polarized dumbbell-shape 4d − t2g recombined dxz − dyz orbital ordering on the Ru sublattice driven by the strongly correlated on-site Coulomb interaction U associated with the elongated RuO6 octahedron local structure
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