Variational study of the Kitaev-Heisenberg-Gamma model

We compute the low-energy excitation spectrum and the dynamical spin structure factor of the Kitaev-Heisenberg-Gamma model through a variational approach based on the exact fractionalized excitations of the pure Kitaev honeycomb model. This novel approach reveals the physical reason for the asymmetric stability of the Kitaev spin liquid phases around the ferromagnetic and antiferromagnetic Kitaev limits. Moreover, we demonstrate that the fractionalized excitations form bound states in specific regions of each Kitaev spin liquid phase and that certain phase transitions induced by Heisenberg and Gamma interactions are driven by the condensation of such a bound state. Remarkably, this bound state appears as a sharp mode in the dynamical spin structure factor, while its condensation patterns at the appropriate phase transitions provide a simple explanation for the magnetically ordered phases surrounding each Kitaev spin liquid phase.

Automated summary

This study computes the low-energy excitation spectrum and dynamical structure of the Kitaev-Heisenberg-Gamma model, revealing the physical reasons for the asymmetric stability of Kitaev spin liquid phases and the formation of bound states by fractionalized excitations in specific regions. The condensation of these bound states drives certain phase transitions induced by Heisenberg and Gamma interactions, providing a simple explanation for the magnetically ordered phases surrounding each Kitaev spin liquid phase.