Collective spin dynamics of Z_{2} vortex crystals in triangular Kitaev-Heisenberg antiferromagnets

Abstract

We show that the mesoscopic incommensurate Z_{2} vortex crystals proposed for layered triangular anisotropic magnets can be most saliently identified by two distinctive signatures in dynamical spin response experiments: the presence of pseudo-Goldstone phononlike modes at low frequencies ω, associated with the collective vibrations of the vortex cores, and a characteristic multiscattered intensity profile at higher ω, arising from a large number of Bragg reflections and magnon band gaps. These are direct fingerprints of the large vortex sizes and magnetic unit cells and the solitonic spin profile around the vortex cores.