Spin and lattice dynamics in the van der Waals antiferromagnet MnPSe3

Antiferromagnetic van der Waals family $\mathit{M}\text{P}{\mathit{X}}_{3}\phantom{\rule{4pt}{0ex}}(M=\text{Fe},\phantom{\rule{4pt}{0ex}}\text{Mn},\phantom{\rule{4pt}{0ex}}\text{Co},\phantom{\rule{4.pt}{0ex}}\text{and}\phantom{\rule{4pt}{0ex}}\text{Ni};X=\text{S}\phantom{\rule{4.pt}{0ex}}\text{and}\phantom{\rule{4pt}{0ex}}\text{Se})$ have attracted significant research attention due to the possibility of realizing long-range magnetic order down to the monolayer limit. Here, we perform inelastic neutron scattering measurements on single-crystal samples of ${\mathrm{MnPSe}}_{3}$, a member of the $\mathit{M}\mathrm{P}{\mathit{X}}_{3}$ family, to study the spin dynamics and determine the effective spin model. The excited magnon bands are well characterized by a spin model, which includes a Heisenberg term with three intraplane exchange parameters (${J}_{1}=\ensuremath{-}0.73$ meV, ${J}_{2}=\ensuremath{-}0.014$ meV, ${J}_{3}=\ensuremath{-}0.43$ meV) and one interplane parameter (${J}_{c}=\ensuremath{-}0.054$ meV), and an easy-plane single-ion anisotropy term ($D=\ensuremath{-}0.035$ meV). Additionally, we observe the intersection of the magnon and phonon bands but no anomalous spectral features induced by the formation of magnon-phonon hybrid excitations at the intersecting region. We discuss possible reasons for the absence of such hybrid excitations in ${\mathrm{MnPSe}}_{3}$.