Publication details

Highly frustrated magnetism in relativistic d4 Mott insulators: Bosonic analog of the Kitaev honeycomb model

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Year of publication 2019
Type Article in Periodical
Magazine / Source Physical Review B
MU Faculty or unit

Faculty of Science

Keywords spin models; magnetism; Kitaev model
Description We study the orbitally frustrated singlet-triplet models that emerge in the context of spin-orbit coupled Mott insulators with t2g4 electronic configuration. In these compounds, low-energy magnetic degrees of freedom can be cast in terms of three-flavor “triplon” operators describing the transitions between spin-orbit entangled J = 0 ionic ground state and excited J = 1 levels. In contrast to a conventional, flavor-isotropic O(3) singlet-triplet models, spin-orbit entangled triplon interactions are flavor-and-bond selective and thus highly frustrated. In a honeycomb lattice, we find close analogies with the Kitaev spin model—an infinite number of conserved quantities, no magnetic condensation, and spin correlations being strictly short-ranged. However, due to the bosonic nature of triplons, there are no emergent gapless excitations within the spin gap, and the ground state is a strongly correlated paramagnet of dense triplon pairs with no long-range entanglement. Using exact diagonalization, we study the bosonic Kitaev model and its various extensions, which break exact symmetries of the model and allow magnetic condensation of triplons. Possible implications for magnetism of ruthenium oxides are discussed.
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