Solitary waves of planar ferromagnets and the breakdown of the spin-polarized quantum Hall effect

A branch of uniformly propagating solitary waves of planar ferromagnets is identified. The energy dispersion and structures of the solitary waves are determined for an isotropic ferromagnet as functions of a conserved momentum. With increasing momentum, the structure undergoes a transition from a form resembling a droplet of spin waves to a Skyrmion-anti-Skyrmion pair. An instability to the formation of these solitary waves is shown to provide a mechanism for the electric field-induced breakdown of the spin-polarized quantum Hall effect.