Manipulating light with axion electrodynamics - Emily Been

The magnetoelectric response in condensed matter physics has recently been mapped to a hypothetical elementary particle, the axion. The existence of the axion was postulated in 1977 to resolve the strong charge-parity problem in quantum chromodynamics (QCD), and has gained attention as a leading dark matter candidate. Despite significant efforts, no QCD axion has been detected to date. However, some topological materials are able to host exact analogues to the axion field.
A background axion response (e.g. quantized θ in 3D topological insulators) can be promoted to a dynamical field by spontaneous symmetry breaking, though an unambiguous signature of these analogue axions is highly nontrivial. We laid the theoretical foundation for a pump–probe protocol for sensing dynamical axion quasiparticles, recently validated in the antiferromagnetic topological insulator MnBi₂Te₄. This framework is further extended to dark-matter detection and to topological platforms with emergent curved spacetimes. Engineering light-matter interactions in these systems lays groundwork for simulating and sensing high energy theories in solid-state platforms.