Observation of terahertz (THz) radiation from a continuum of coherent magnons in a layered triangular ferromagnet

Magnons, the collective excitations of spins in magnetic materials, offer exciting possibilities for spintronic and photonic applications. In this talk, I will discuss our recent investigation of magnons in the layered ferromagnet CrGeTe₃ using nonlinear THz spectroscopy. We observe a broadband THz emission from a continuum of coherent magnons generated by an ultrafast optical pump, with a strong dependence on pump polarization and external magnetic field. We attribute this emission to magnetic-dipole transitions induced by impulsive stimulated Raman scattering (ISRS), distinguishing it from the typical THz radiation linked to incoherent hot magnon emission during electron relaxation.