Orbital Zeeman effect: Signature of charge in the carriers of ferromagnetism

By deriving quantum hydrodynamic equations for an isotropic single-band ferromagnet in a finite magnetic field, we find that a massive mode recently predicted splits under the action of the field. The splitting is a peculiarity of charged fermions and is linear in the field to leading order in q , bearing a resemblance to the Zeeman effect in this limit, and providing a way to determine whether ferromagnetism arises from charged objects or not.