Thermal and quantum fluctuations in the extended Kitaev-Yao-Lee spin-orbital model
Phys. Rev. B 113, 174430 – Published 20 May, 2026
DOI: https://doi.org/10.1103/dx3p-s4f3
Abstract
Building upon the spin-1/2 Kitaev model on a honeycomb lattice, the Yao-Lee spin-orbital model provides exactly solvable quantum spin liquids with potentially better stability against perturbations due to the additional degree of freedom. Recently, the microscopic mechanism underlying the Yao-Lee interaction in honeycomb materials has been uncovered, leading to an extended Kitaev-Yao-Lee spin-orbital model when the celebrated Kugel-Khomskii interaction is included. Numerical studies of this model identified various disordered phases, including a broad region of the nematic phase that was reminiscent of a spin-orbital liquid. Here, we investigate the origin and stability of this nematic phase via thermal and quantum fluctuations using classical Monte Carlo simulations and a generalized spin-wave theory appropriate for the spin-orbital model. We demonstrate that the additional spin-orbital degree of freedom gives rise to strong thermal and quantum fluctuations in spin-orbital models, providing insight into the emergence of disordered phases.
