THz spectroscopy of topological magnon candidate CoTiO₃

Recent advancements in topological band theory have predicted the existence of topologically-protected magnon excitations [1] with potential spintronic applications. CoTiO₃ is an Ilmenite-structure antiferromagnet with a Néel temperature of 38 K and magnon energies in the THz range. Previous work has also identified CoTiO₃ as a candidate to host topological magnons [2]. We follow up on that research by measuring the THz transmission and reflectivity of both single crystal and pressed powder samples of CoTiO₃ and we report the results including a large absorptions near 1 and 1.6 THz. We propose that the modes broaden with decreasing temperature or a new absorption appears below the Néel temperature with energy coinciding with a zone-center magnon excitation. We will discuss these possibilities together with the details of the THz polarization response.
[1] arXiv:1807.05232. Fuyan Lu, Yuan-Ming Lu
[2] arXiv:1907.02061. Bo Yuan, Ilia Khait, Guo-Jiun Shu, F. C. Chou, M. B. Stone, J. P. Clancy, Arun Paramekanti, Young-June Kim