Axion Electrodynamics in Topological Materials

Understand

One of the intriguing properties characteristic to three-dimensional topological materials is the topological magnetoelectric phenomena arising from a topological term called the $\theta$ term.

• Such magnetoelectric phenomena are often termed the axion electrodynamics, since the $\theta$ term has exactly the same form as the action describing the coupling between a hypothetical elementary particle, axion, and a photon.
• The axion was proposed about forty years ago to solve the so-called strong CP problem in quantum chromodynamics, and is now considered as a candidate for dark matter.
• In this tutorial, we overview theoretical and experimental studies on the axion electrodynamics in three-dimensional topological materials.