Dynamical multiferroicity

In this talk, I present how circularly polarized optical phonons create magnetic moments, reminiscent of atomistic electromagnetic coils. An appealing mechanism for inducing multiferroicity in materials is the generation of electric polarization by a spatially varying magnetization that is coupled to the lattice through the spin-orbit interaction. Here, I describe the reciprocal effect, in which a time-dependent electric polarization induces magnetization even in materials with no existing spin structure. I present a formalism for this dynamical multiferroic effect in the case for which the polarization derives from optical phonons, and estimate the strength of the phonon Zeeman effect, which is the solid-state equivalent of the well-established vibrational Zeeman effect in molecules, using density functional theory. I further show that a recently observed behavior—the resonant excitation of a magnon by optically driven phonons—is described by the formalism.