Magnons in the strained Heisenberg-Kitaev magnet

The properties of magnons hosted in strained Heisenberg-Kitaev magnets are investigated using numerical and analytical calculations. Considering that deformation fields modulate the coupling parameters, we find a general expression for the weakly strained magnon Hamiltonian that depends on the (symmetric) strain tensor. We numerically tested our results in finite nanoribbon structures. We found that uniaxial deformations make the bulk bands more dispersive while topologically protected in-gap edge modes become nonreciprocal at the boundary of the Brillouin Zone. On the other hand, when applying a twist deformation, the simultaneous modulation of both Heisenberg and Kitaev parameters enables the apparition of flat bands, promoting the presence of non-propagative topologically protected magnonic edge states, whose properties strongly depends on the strain strength. In addition, the characteristic localization of magnon edge modes is preserved, which allows for testing the robustness of the bulk-boundary correspondence under lattice deformations. Our results contribute to a major understanding of Heisenberg-Kitaev magnets and how applying different strains allows for precise control over magnon properties.