Solitons and the excitation spectrum of the classical Ising-Heisenberg ferromagnetic chain

Using the molecular-dynamics technique and nonlinear spin wave theory, the authors clarify the relevance of envelope solitons for dynamic form factors in the classical Ising-Heisenberg ferromagnetic chain. They find that the classical limit of magnon bound states and thus the envelope solitons gives rise to a central peak, a 'bound-state resonance' and the removal of unphysical singularities.