Terahertz Magnon Excitations and Switching in Non-Collinear Antiferromagnets

We investigate how spatiotemporal spin polarized current can lead to terahertz frequency excitations in non-collinear antiferromagnets. By solving the Landau-Lifshitz-Gilbert equation numerically for non-collinear antiferromagnet, we show that the magnon frequency spectrum exhibits standing spin wave modes and depends on the thickness of Mn${}_3$Ge in heterostructure Fe|Au|Mn${}_3$Ge. Also, we analyze the switching process of ground state as a function of a spin current. We show a switching phase diagram, which contains switching and non-switching regions. Our work suggests non-collinear antiferromagnets as an efficient platform for terahertz magnonics and ultrafast memory devices.