Complex Orbital State Stabilized by Strong Spin-Orbit Coupling in a Metallic Iridium Oxide IrO${}_2$

Abstract

Resonant x-ray diffraction experiments were performed for the metallic iridium oxide IrO${}_2$. We observed anisotropic tensor of susceptibility (ATS) scattering, the spectrum of which shows a sharp contrast between the $L_3$ and $L_2$ edges. At the $L_3$ edge, resonance excitations were clearly observed from the core 2$p$ orbitals to both the 5$d$ $t_{2g}$ and $e_g$ orbitals. In contrast, the resonance mode associated with 5$d$ $t_{2g}$ orbitals was indiscernible at the $L_2$ edge. This contrasting behavior indicates that Ir 5$d$ $t_{2g}$ orbitals are fairly close to the $J_{\mathrm{eff}}$ = 1/2 state due to the strong spin--orbit coupling in 5$d$ transition metal ions, as in the Mott insulator Sr${}_2$IrO${}_4$. Our results clearly demonstrate that ATS scattering is a useful probe for investigating complex orbital states in a metallic state. Such states induce novel phenomena such as the spin Hall effect.

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Cited by in corpus (6)

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• Effect of spin orbit coupling and Hubbard $U$ on the electronic structure of IrO${}_2$
• Field-direction control of the type of charge carriers in nonsymmorphic IrO2
• Spin-orbit effects in pentavalent Iridates: Models and materials
• Stabilization of a honeycomb lattice of IrO${}_6$ octahedra in superlattices with ilmenite-type MnTiO${}_3$