Observation of spin-orbit excitations and Hund's multiplets in Ca${}_2$RuO${}_4$

Abstract

We use Ru $L_3$-edge (2838.5 eV) resonant inelastic x-ray scattering (RIXS) to quantify the electronic structure of Ca${}_2$RuO${}_4$, a layered $4d$-electron compound that exhibits a correlation-driven metal-insulator transition and unconventional antiferromagnetism. We observe a series of Ru intra-ionic transitions whose energies and intensities are well described by model calculations. In particular, we find a $\mathrm{J}=0\to 2$ spin-orbit excitation at 320 meV, as well as Hund's-rule driven $\mathrm{S}=1\to 0$ spin-state transitions at 750 and 1000 meV. The energy of these three features uniquely determines the spin-orbit coupling, tetragonal crystal-field energy, and Hund's rule interaction. The parameters inferred from the RIXS spectra are in excellent agreement with the picture of excitonic magnetism that has been devised to explain the collective modes of the antiferromagnetic state. $L_3$-edge RIXS of Ru compounds and other $4d$-electron materials thus enables direct measurements of interactions parameters that are essential for realistic model calculations.

9 pages and 4 figures. accepted in PRB

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Cited by in corpus (21)

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• Distinct spin and orbital dynamics in Sr${}_2$RuO${}_4$
• Van Vleck excitons in Ca${}_2$RuO${}_4$
• Spin and charge excitations in the correlated multiband metal Ca3Ru2O7
• Electronic excitations in $5d^4$ J=0 Os${}^{4+}$ halides studied by RIXS and optical spectroscopy
• Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^4$ magnet
• Hund bands in spectra of multiorbital systems
• Spin-orbit coupling and crystal-field splitting in Ti-doped Ca2RuO4 studied by ellipsometry
• Magnetic ground state of the dimer-based hexagonal perovskite Ba${}_3$ZnRu${}_2$O${}_9$
• Spin-orbit excitons and electronic configuration of the $5d^4$ insulator Sr${}_3$Ir${}_2$O${}_7$F${}_2$
• Photoemission Spectrum of Ca2RuO4: Spin Polaron Physics in an S=1 Antiferromagnet with Anisotropies
• Spin-orbital mechanisms for negative thermal expansion in Ca2RuO${}_4$
• Resonant Inelastic X-ray Scattering from Electronic Excitations in $\alpha$-RuCl${}_3$ Nanolayers
• Orbitally-selective Breakdown of the Fermi Liquid and Simultaneous Enhancement of Metallic and Insulating States in Correlated Multi-band Systems with Spin-orbit Coupling
• Photoinduced phase switching at a Mott insulator-to-metal transition
• Spin-orbit excitons in a correlated metal: Raman scattering study of Sr2RhO4
• Collective mode excitations and simulated $L$-edge resonant-inelastic x-ray scattering spectra in antiferromagnetic Ca${}_2$RuO${}_4$
• Critical magnetic fluctuations in the layered ruthenates Ca${}_2$RuO${}_4$ and Ca${}_3$Ru${}_2$O${}_7$
• Coexistence of insulator-like paramagnon and metallic spin-orbit exciton modes in SrIrO${}_3$
• Automated evaluation of imaginary time strong coupling diagrams by sum-of-exponentials hybridization fitting
• Formation of orbital molecules on a pyrochlore lattice induced by A-O bond covalency