Interplay between the axion field and the lattice vibrations in insulators

Axion electrodynamics describes the magnetoelectric phenomena that follow from a θE·B term in the electromagnetic Lagrangian, where θ is the axion field and E and B are the electric and magnetic fields (respectively). In topological materials, axion electrodynamics has been predicted to produce remarkable phenomena such as the half-quantized Hall effect, the quantized topological magnetoelectric effect and the chiral magnetic effect. In this talk, we concentrate on phononic manifestations of axion electrodynamics in insulators, which have remained unexplored. By evaluating the change in the theta field due to electron-phonon interactions, we predict a magnetic-field-induced Born effective charge and show that it displays a maximum across a topological phase transition. We comment on the application of our theory to the MnBiTe family of materials.