Spin-orbit Mott insulators composed of t2g4 transition metal ions may host excitonic magnetism due to the condensation of spin-orbital J=1 triplons. Prior experiments suggest that the 4d antiferromagnet Ca2RuO4 embodies this notion, but a J=0 nonmagnetic state as a basis of the excitonic picture remains to be confirmed. We use Ru L3-edge resonant inelastic x-ray scattering to reveal archetypal J multiplets with a J=0 ground state in the cubic compound K2RuCl6, which are well described within the LS-coupling scheme. This result highlights the critical role of unquenched orbital moments in 4d-electron compounds and calls for investigations of quantum criticality and excitonic magnetism on various crystal lattices.
@article{arxiv.2107.10046,
title = {Nonmagnetic $J = 0$ State and Spin-Orbit Excitations in K$_{2}$RuCl$_{6}$},
author = {H. Takahashi and H. Suzuki and J. Bertinshaw and S. Bette and C. Mühle and J. Nuss and R. Dinnebier and A. Yaresko and G. Khaliullin and H. Gretarsson and T. Takayama and H. Takagi and B. Keimer},
journal= {arXiv preprint arXiv:2107.10046},
year = {2021}
}