Antiferromagnetic Topological Insulators as Magnon-Based Light Dark Matter Detectors

In recent years, the search for dark matter (DM) has stretched to lower masses, with several well-motivated theories for sub-MeV DM. However, the detection of these light DM candidates presents a substantial challenge, requiring target materials that exhibit measurable responses with just a few meV of energy deposition from DM scattering or absorption. DM-magnon interaction in magnetic materials has recently been proposed as a possible detection scheme that would also be sensitive to spin-dependent DM couplings. However, the feasibility of these detection schemes is limited by the ability to read out single magnons. In this work, we instead explore the possibility of magnons in topological insulators as a potential route to sensing. Specifically, we study the spin-wave excitation spectra of antiferromagnetic topological insulators using first-principles calculations. We explore the influence of magnons on the bulk electronic structure and symmetry-protected topological surface states of these systems and examine spin-dependent interactions with several dark matter models. Finally, we establish criteria for selecting optimal targets for magnon-based DM detectors with potential read-out schemes.