Nonlinear phononic coupling in antiferromagnetic monolayer MnPS3

The nonlinear coupling between phonons, though being weak, can be manifested under high intensity laser pulse. Here we use first-principles calculations to identify the third-order nonlinear coupling between Raman and IR active phonons at I' in antiferromagnetic MnPS3 monolayer. The couplings can be categorized into two types: type-A contains only A1g, while type-B contains A1g, as well as other representations of D3d. The type-A coupling A1g(24)A22u(25) turns the magnetic point group of the system from D3d(D3) to C3v(C3) if spin-orbit coupling is ignored, and induces a phase transition from antiferromagnet to i-wave altermagnet. The Eu(29 - 30) IR mode couples simultaneously with three Raman modes, and the polarization of light can be used to control the coupling between Eu and Eg mode. The degenerate IR modes [e.g., Eu(10 - 11)], when resonantly driven by circular polarized light pulse, can induce phonon orbital magnetic moment. The efficiency of transfer of energy and angular momentum from circular polarized light to phonon is discussed. Our work contributes to the understanding of light-induced magnetic phase transition in antiferromagnetic monolayers.