Fig. 8: Time-domain probe of phonon-magnon couplings via magnon excitation.

a THz pump-induced polarization rotation of the 800-nm probe pulse measured in CoF₂ at different temperatures, whose antiferromagnetic transition temperature is at 39 K. b Temperature-dependent Fourier amplitudes of the magnon mode (blue open circles) and phonon mode (green filled circles), both vanishing above the Néel temperature, T_N. c Fourier spectrum of the nonlinear amplitude measured in 2D terahertz spectroscopy on CoF₂ at 10 K. d Schematic illustration of magnon-mediated excitation of the B_1g phonon by the THz magnetic field. ℏ is the reduced Planck’s constant; Ω_m and Ω_ph are the magnon and phonon frequency, respectively. Adapted from ref. ²¹⁴, AAAS.