Magnon anomalous interactions from SU(2) gauge symmetry: Are magnons 'charged' under spin?

The Pauli-Schrödinger non-relativistic theory of spin-12 charged fermions requires invariance under the U(1)×SU(2) gauge group. The U(1) symmetry responds for the usual coupling of a charged particle to the electromagnetic gauge potentials Aμ, while the spin interactions with the electromagnetic fields are obtained by changing the status of the global SU(2) rotational invariance of the Pauli-Schrödinger Lagrangian density to a local SU(2) gauge symmetry, for which the electric and magnetic fields E and B play the role of gauge potentials. Assuming that local gauge invariance under rotations can be applied to an arbitrary spin-S quantum field we extend the SU(2) gauge symmetry to the magnon field theory of Heisenberg ferromagnets. It is shown that the magnon field couples to the corresponding gauge fields, E and B, yielding 'anomalous' interactions of magnons with the electric component of the electromagnetic field, as in the case of charged excitations.