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

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-$t_{2g}$ excitations and $t_{2g}$-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 $\zeta$=0.34 eV, Hund's coupling $J_H$=0.43 eV, the onset of excitations across the Mott gap at $\Delta$=2.2 eV, the cubic crystal-field splitting 10Dq=3.3 eV, and the charge-transfer energy ${\Delta }_{CT}$=4.6 eV. With $J_H/\zeta$=1.3, K${}_2$OsCl${}_6$ is in the intermediate-coupling regime. In a $t_{2g}$-only Kanamori picture, the above values correspond to ${\zeta }^{eff}$=0.41 eV and $J_H^{eff}$=0.28 eV, which is very close to results reported for related $5d^4$ 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 ${\Delta }_{CT}$, while the spin-orbit-entangled intra-$t_{2g}$ excitations below 2 eV and hence $\zeta$ 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.

14 pages, 14 figures

References in corpus (20)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Strong electronic correlations from Hund's coupling
• Models and Materials for Generalized Kitaev Magnetism
• Spin-orbit-entangled electronic phases in 4$d$ and 5$d$ transition-metal compounds
• Spin-Orbit-Induced Orbital Excitations in Sr2RuO4 and Ca2RuO4: A Resonant Inelastic X-ray Scattering Study
• Resonant inelastic x-ray incarnation of Young's double-slit experiment
• Observation of spin-orbit excitations and Hund's multiplets in Ca${}_2$RuO${}_4$
• Magnetic Excitations in Spin-Orbit Coupled $d^4$ Mott Insulator on Square Lattice
• Exchange interactions, Jahn-Teller coupling, and multipole orders in pseudospin one-half $5{\mathbf{d}}^2$ Mott insulators
• Ferro-octupolar order and low-energy excitations in d${}^2$ double perovskites of Osmium
• Nonmagnetic $J=0$ State and Spin-Orbit Excitations in K${}_2$RuCl${}_6$
• Toward cubic symmetry for Ir${}^{4+}$: structure and magnetism of antifluorite K${}_2$IrBr${}_6$
• Octupolar order and Ising quantum criticality tuned by strain and dimensionality: Application to $d$-orbital Mott insulators
• Lone octupole and bulk magnetism in osmate 5d2 double perovskites
• Quasimolecular electronic structure of the spin-liquid candidate Ba${}_3$InIr${}_2$O${}_9$
• Field-induced Kitaev multipolar liquid in spin-orbit coupled $d^2$ honeycomb Mott insulators
• Vibronic excitations in resonant inelastic x-ray scattering spectra of K${}_2$RuCl${}_6$
• Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^4$ magnet
• Spin-orbit coupling and crystal-field splitting in Ti-doped Ca2RuO4 studied by ellipsometry
• J = 0 nonmagnetic insulating state in K${}_2$Os$X_6$ (X = F, Cl and Br)

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• Multipolar magnetism in $5d^2$ vacancy-ordered halide double perovskites
• Spin-orbit coupling in a half-filled $t_{2g}$ shell: the case of $5d^3$ K${}_2$ReCl${}_6$
• Spin-orbital-lattice entanglement in the ideal j=1/2 compound K${}_2$IrCl${}_6$
• Rotational phase transitions in antifluorite-type osmate and iridate compounds
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$
• Coupled-cluster approach to vibronic effects in resonant inelastic x-ray scattering of quantum materials: Application to a $5d^1$ rhenium oxide
• Local site behavior of the 5d and 4f ions in the frustrated pyrochlore Ho2Os2O7