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Title: Axion quasiparticle and axion polariton in antiferromagnetic topological insulators
Plain: In antiferromagnetic topological insulators, magnetic fluctuations should make the axion angle oscillate, producing a collective excitation that mixes with light, and its coupling to light has not been observed.
Precise: Li, Wang, Qi and Zhang (Nature Physics, 2010) predicted that in antiferromagnetic topological insulators the axion field $\theta(r,t)$ acquires dynamics through coupling to the Neel order, giving an axion quasiparticle that hybridizes with photons into axion polaritons under a static magnetic field. Determine whether the polariton exists in a candidate material (MnBi2Te4 family) and measure the axion mass and photon coupling. An answer is spectroscopic detection with the predicted dependence on applied field.
Settled by: Terahertz or microwave spectroscopy showing a polariton gap that scales with the applied field and disappears outside the antiferromagnetic phase.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: partially-resolved
Status note: A 2025 ultrafast-optics study reported coherent axion-mode oscillations in 2D MnBi2Te4; axion-polariton hybridization with light is not observed as of 2026, to this survey's knowledge.
Posed since: 2010