A Proposal to Detect Dark Matter Using Axionic Topological Antiferromagnets*

Astrophysical and cosmological observations of the last 40 years provide strong evidence for the existence of non-baryonic dark matter. Among possible candidates are dark axions, hypothetical particles suggested to solve the CP problem in quantum chromodynamics. It is known that magnetically doped topological insulators can become "axionic insulators" and host axionic excitations. In particular, antiferromagnetically doped topological insulators (A-TI) are among the candidates to host dynamical axion fields and axion-polaritons. Here we demonstrate that using the axion quasiparticle and antiferromagnetic fluctuations in A-TI's in conjunction with low-noise methods of detecting THz photons presents a viable route to detect axion dark matter with mass 0.7 to 3.5 meV, a range currently inaccessible to all other dark matter detection experiments and proposals.