Symmetry constraints on magnon-induced dynamics of skyrmion helicity in frustrated magnets

The helicity of a magnetic skyrmion in a centrosymmetric frustrated magnet is a soft collective coordinate and a candidate variable for encoding quantum information. Its coherence is ultimately influenced by coupling to the magnon environment, which is commonly incorporated only phenomenologically. Here we combine a microscopic Keldysh treatment of the helicity–magnon coupling to resolve the contribution of individual magnon modes to the effective helicity dynamics. In the U(1)-symmetric model, the magnon bath generates, to leading order, a reactive helicity mass renormalization. When U(1) symmetry is broken, additional direct helicity–magnon couplings become allowed. In the presence of finite magnon lifetimes, these couplings generate an Ohmic contribution to the low-frequency helicity dynamics. The spatial symmetry of the perturbation determines which magnon sectors contribute to this damping, providing mode-resolved selection rules for the helicity–magnon coupling. Thus, we establish a microscopic connection between helicity dynamics and the excitation spectrum of frustrated skyrmions and identify the symmetry constraints governing dissipation of helicity-based quantum states.