Magnon dynamics studied by two-pulse THz coherent spectroscopy*

THz multi-dimensional coherent spectroscopy (THz-MDCS) is a powerful coherent spectroscopy tool to study spin coherence in complex materials. Although THz-MDCS has been applied in magnetic materials, it has not been able to measure high order magnon correlations exceeding third order until this work. Here, we measure coherent nonlinear responses of various magnonic systems using THz-MDCS. The unique high harmonic and wave mixing peaks are resolved up to 6^th order, which reveals complicated spin interaction and multi-magnon excitations. We further achieve coherent control of the magnon dynamics by changing the two-pulse separation. Our results show THz MDCS spectroscopy is a powerful tool to study vast coherent nonlinear processed and spin correlations in complex magnetic systems.