SmallTalks "Magnetization from circularly polarized phonons"

Abstract 

The proportionality between the angular momentum and the magnetic moment suggests that circular movement of ions on a crystal lattice will induce magnetization of the material. Such circular motion is characteristic of axial, or circularly polarized, phonons. Experimentally, these phonons were indeed shown to induce magnetization, but the size of the effect was measured to be several orders of magnitude larger than could be predicted from the ionic motion alone [1]. This suggests a need for a new theoretical description of this effect.

One such description involves studying the phonon induced magnetization by using the phonon inverse Faraday effect formalism. This formalism involves considering the coupling between the electrons and phonons as the second order perturbation [2]. Using this approach, we are able to calculate the effective magnetic field resulting from axial phonons that is consistent with the experimental observations. Furthermore, we also consider the potential of axial phonons to influence other physical phenomena, such as the anomalous Hall effect.