Signature of a Z2 Vortex in the Dynamical Correlations of the Triangular-Lattice Heisenberg Antiferromagnet

Dynamical properties of the classical Heisenberg antiferromagnet on the triangular lattice are investigated by means of a spin-dynamics simulation and an analytical calculation. While the model was suggested to exhibit a topological transition driven by the Z(2)-vortex binding-unbinding, weakness of the associated thermodynamic singularity has made it difficult to observe the evidence of the Z(2) vortex experimentally so far, only some indirect support. Here, we show that the signature of the Z(2)-vortex excitation and the vortex-induced topological transition can be captured from the dynamical spin correlations. In particular, the dynamical spin structure factor exhibits a characteristic central peak around the Z(2)-vortex transition, and this central peak will be a fingerprint of the Z(2)-vortex excitation.