Spin-Orbit Excitons in a Correlated Metal: Raman Scattering Study of Sr 2 RhO 4

Using Raman spectroscopy to study the correlated 4 d -electron metal Sr 2 RhO 4 , we observe pronounced excitations at 220 meV and 240 meV with A 1 g and B 1 g symmetries, respectively. We identify them as transitions between the spin-orbit multiplets of the Rh ions, in close analogy to the spin-orb...

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Published in:Physical review letters 2024-03, Vol.132 (11), Article 116502
Main Authors: Wang, Lichen, Liu, Huimei, Zimmermann, Valentin, Yogi, Arvind Kumar, Isobe, Masahiko, Minola, Matteo, Hepting, Matthias, Khaliullin, Giniyat, Keimer, Bernhard
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Language:English
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Summary:Using Raman spectroscopy to study the correlated 4 d -electron metal Sr 2 RhO 4 , we observe pronounced excitations at 220 meV and 240 meV with A 1 g and B 1 g symmetries, respectively. We identify them as transitions between the spin-orbit multiplets of the Rh ions, in close analogy to the spin-orbit excitons in the Mott insulators Sr 2 IrO 4 and α − RuCl 3 . This observation provides direct evidence for the unquenched spin-orbit coupling in Sr 2 RhO 4 . A quantitative analysis of the data reveals that the tetragonal crystal field Δ in Sr 2 RhO 4 has a sign opposite to that in insulating Sr 2 IrO 4 , which enhances the planar x y orbital character of the effective J = 1 / 2 wave function. This supports a metallic ground state, and suggests that c -axis compression of Sr 2 RhO 4 may transform it into a quasi-two-dimensional antiferromagnetic insulator.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.132.116502