Optical spectroscopy of magnetic excitations in the honeycomb antiferromagnet Na₃Co₂SbO₆

The Kitaev honeycomb model offers a potential platform for realizing quantum spin liquid (QSL) states. Co-based honeycomb magnets, and specifically Na₃Co₂SbO₆, stand out as promising systems with possible dominant Kitaev interactions¹. Na₃Co₂SbO₆ features relatively low Neel temperature and saturation magnetic fields, and much smaller Na-occupation disorder compared to its sister Kitaev QSL candidate Na₂Co₂TeO₆ ². Here we use infrared and Raman spectroscopy to probe low-energy magnetic excitations in single-crystal Na₃Co₂SbO₆ as the magnetic field drives the system from the antiferromagnet to the spin-polarized state. We identified multiple magnetic excitations for different orientations of the magnetic field in respect to crystal axes. While the single-magnon excitations can be well-described using linear spinW calculations (which allows us to extract parameters of the Heisenberg-Kitaev-G- G’ model), the in-plane anisotropy of the g-factor is much smaller compared to the expectations based on the reported magnetization data ³.

¹ Liu, et al. PRL 125, 047201 (2020)

² Xiang, PRL 131, 076701 (2023)

³ Li, et al. PRX 12, 041024 (2022)