19 November 2020 Thu 5 pm

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It has been suggested that certain antiferromagnetic topological insulators contain axion quasiparticles and that such materials could be used to detect axion dark matter. The axion quasiparticle is the antiferromagnetic magnon coupled to the electromagnetic (EM) Chern-Simons term, which leads to mass mixing between the axion quasiparticle and the electric field. A model for including losses into this system is presented, and the modified dispersion relation is computed. The EM boundary conditions and transmission and reflection coefficients are also computed. It is shown how transmission spectroscopy can be used to determine the resonant frequencies and damping coefficients of the material, and an ongoing experiment on material candidates is discussed. The modified dispersion relation and boundary conditions permit the resonant conversion of dark matter axions into THz photons. The range of desirable material parameters is identified that would allow for the detection of the QCD axion in the mass range near 1 meV using current or near-future technology.