Dynamics of a single hole in the Heisenberg-Kitaev model: a self-consistent Born approximation study

TL;DR

This study investigates the charge dynamics of a single hole in the Heisenberg-Kitaev model using the self-consistent Born approximation, revealing low-energy quasiparticles with small bandwidths and their dependence on magnetic phases and Kitaev interaction strength.

Contribution

It provides a detailed analysis of quasiparticle behavior in the Heisenberg-Kitaev model, highlighting the effects of magnetic order and Kitaev coupling on charge excitations.

Findings

Low-energy quasiparticles appear around the K point in the Brillouin zone.

Quasiparticle bandwidths are very small due to hole-magnon coupling.

Quasiparticle weights are suppressed in the first BZ but recover in extended BZs, especially in the zigzag phase.

Abstract

The magnetic properties of 4d and 5d transition-metal insulating compounds with the honeycomb structure are believed to be described by the Heisenberg-Kitaev model, which contains both the isotropic Heisenberg interaction J and anisotropic Kitaev interaction K. In this paper, to investigate the charge dynamics in these materials, we study the single-hole propagation of the t-J-K model in various magnetically ordered phases by the self-consistent Born approximation. We find that there are low-energy coherent quasiparticle (QP) excitations in all of these phases which appear firstly around the K point in the Brillouin zone (BZ), but the band-widths of these QPs are very small due to the hole-magnon coupling. Interestingly, in the zigzag phase relevant to recent experiments, though the QP weights are largely suppressed in the physical spectra in the first BZ, we find that they recover in the extended BZs. Moreover, our results reveal that the low-energy QP spectra are reduced with the increase of K.