Thermal and quantum fluctuations in extended Kitaev-Yao-Lee spin-orbital model

TL;DR

This paper explores how thermal and quantum fluctuations influence the stability of disordered nematic phases in an extended Kitaev-Yao-Lee spin-orbital model, revealing the role of spin-orbital degrees of freedom.

Contribution

It provides the first analysis of thermal and quantum fluctuation effects on the nematic phase in an extended Kitaev-Yao-Lee model using Monte Carlo and spin wave theory.

Findings

Thermal and quantum fluctuations are enhanced by spin-orbital degrees of freedom.

Disordered nematic phases are stabilized by these fluctuations.

Insights into the emergence of spin-orbital liquids are gained.

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 have identified various disordered phases, including a broad region of the nematic phase that is 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.