paper

Quantum liquids of the S=3/2 Kitaev honeycomb and related Kugel-Khomskii models

arXiv:2304.13378 · doi:10.1103/PhysRevB.108.075111

Abstract

The Kitaev honeycomb model (KHM) is unique among the spin- Kitaev models due to a massive ground state quasi-degeneracy that hampered previous numerical and analytical studies. In a recent work~\cite{jin2022unveiling}, we showed how an SO(6) Majorana parton mean-field theory of the isotropic KHM explains the anomalous features of this Kitaev spin liquid (KSL) in terms of an emergent low-energy Majorana flat band. Away from the isotropic limit, the KSL generally displays a quadrupolar order with gapped or gapless Majorana excitations, features that were quantitatively confirmed by DMRG simulations. In this paper, we explore the connection between the KHM with Kugel-Khomskii models and discover new exactly soluble examples for the latter. We perform a symmetry analysis for the variational parton mean-field \emph{Ans{ä}tze} in the spin and orbital basis for different quantum liquid phases of the KHM. Finally, we investigate a proposed time-reversal symmetry breaking spin liquid induced by a {[}111{]} single ion anisotropy and elucidate its topological properties as well as experimental signatures, e.g. an unquantized thermal Hall response.

17 pages, 9 figures

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