The possibility of a new type of elementary excitations in van der Waals magnetoelectrics—surface axion–polaritons—has been predicted. Hybrid waves are generated when an electromagnetic wave is incident on the surface of a two-dimensional A-type antiferromagnet (with opposite magnetizations of the layers), whose symmetry allows a linear magnetoelectric effect. Dynamic fluctuations of the antiferromagnetic order parameter lead to the emergence of a magnetoelectric mode undergoing the axion interaction with the electromagnetic field, which ensures hybridization of the photon and magnon components. The effective mass of the emerging axion quasiparticles decreases with an increase in the magnetoelectric coupling; this mass in a CrI 3 bilayer is about 10 –7 of the electron mass. Due to their two-dimensionality and strong magnetoelectric response, these structures provide a convenient platform for the experimental study of axion effects.
Zvezdin et al. (Thu,) studied this question.