Electronic excitations in $5d^4$ J=0 Os$^{4+}$ halides studied by RIXS and optical spectroscopy

P. Warzanowski; M. Magnaterra; P. Stein; G. Schlicht; Q. Faure; Ch. J. Sahle; T. Lorenz; P. Becker; L. Bohaty; M. Moretti Sala; G. Monaco; P. H. M. van Loosdrecht; M. Grüninger

doi:10.1103/PhysRevB.108.125120

paper

Electronic excitations in $5 d^{4}$ J=0 Os $^{4 +}$ halides studied by RIXS and optical spectroscopy

arXiv:2306.12538 · doi:10.1103/PhysRevB.108.125120

Abstract

We demonstrate that the cubic antifluorite-type halides K $_{2}$ OsCl $_{6}$ , K $_{2}$ OsBr $_{6}$ , and Rb $_{2}$ OsBr $_{6}$ are excellent realizations of non-magnetic J=0 compounds. The magnetic susceptibility shows the corresponding Van-Vleck type behavior and no sign of defects. We investigate the electronic excitations with two complementary techniques, resonant inelastic x-ray scattering (RIXS) and optical spectroscopy. This powerful combination allows us to thoroughly study, e.g., on-site intra- $t_{2 g}$ excitations and $t_{2 g}$ -to- $e_{g}$ excitations as well as inter-site excitations across the Mott gap and an exciton below the gap. In this way, we determine the electronic parameters with high accuracy, altogether yielding a comprehensive picture. In K $_{2}$ OsCl $_{6}$ , we find the spin-orbit coupling constant $ζ$ =0.34 eV, Hund's coupling $J_{H}$ =0.43 eV, the onset of excitations across the Mott gap at $Δ$ =2.2 eV, the cubic crystal-field splitting 10Dq=3.3 eV, and the charge-transfer energy $Δ_{C T}$ =4.6 eV. With $J_{H} / ζ$ =1.3, K $_{2}$ OsCl $_{6}$ is in the intermediate-coupling regime. In a $t_{2 g}$ -only Kanamori picture, the above values correspond to $ζ^{e f f}$ =0.41 eV and $J_{H}^{e f f}$ =0.28 eV, which is very close to results reported for related $5 d^{4}$ iridates. In the tetragonal phase at 5 K, the non-cubic crystal field causes a peak splitting of the J=1 state as small as 4 meV. Compared to K $_{2}$ OsCl $_{6}$ , the bromides K $_{2}$ OsBr $_{6}$ and Rb $_{2}$ OsBr $_{6}$ show about 12-14 % smaller values of 10Dq and $Δ_{C T}$ , while the spin-orbit-entangled intra- $t_{2 g}$ excitations below 2 eV and hence $ζ$ and $J_{H}$ are reduced by less than 4 %. Furthermore, the Mott gap in K $_{2}$ OsBr $_{6}$ is reduced to about 1.8 eV.

arXiv comment14 pages, 14 figures

Electronic excitations in $5 d^{4}$ J=0 Os $^{4 +}$ halides studied by RIXS and optical spectroscopy

Abstract

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Electronic excitations in 5d4 J=0 Os4+ halides studied by RIXS and optical spectroscopy

Abstract

References in corpus (59)

Cited by in corpus (7)

Electronic excitations in $5 d^{4}$ J=0 Os $^{4 +}$ halides studied by RIXS and optical spectroscopy