Quasiparticle interactions in CoPS₃ (Co₂P₂S₆), a semiconducting 2D antiferromagnet

The MPX family (M =transition metal, X = S or Se) of magnetic van der Waals (vdW) materials features a transition metal honeycomb lattice where magnetism has already been observed as the 2D limit is approached. Here, we study the bulk properties of single crystal CoPS3, an antiferromagnet below 130 K, via temperature-, wavelength- and polarization-dependent magneto-Raman spectroscopy. Magnetometry, calorimetric, and X-ray diffraction data complement the optical data. Multiple phonons are observed, and their numbers and magnitudes change with temperature; especially noting phonons from outside the gamma point due to zone folding. A spin wave or magnon mode was observed at unusually high energy and in the energy proximity to a high density of phonons. These quasiparticles interact and it is possible the track the interaction with our unique measurement capabilities. In addition, temperature-dependent high-resolution synchrotron powder diffraction was collected and analyzed. We explore the implications of these data with the additional help of density functional theory.