Broadband Excitation of Antiferromagnetic Dynamics by Acoustic Phonons.

Excitation of antiferromagnetic dynamics is at the core of ultrafast spintronics. Coherent excitation of antiferromagnetic magnons is typically monochromatic, confined at dispersion intersections between antiferromagnetic magnons and the excitation source. Broadband excitation can be enabled by introducing electron spins in an incoherent manner, albeit accompanied by high energy consumption from Joule heating. Here, we demonstrate a broadband excitation of antiferromagnetic dynamics of 2D antiferromagnet CrSBr without Joule heating, by Rayleigh-type surface acoustic wave (R-SAW). Incoherent magnons are efficiently excited via the angular momentum transfer from acoustic phonons, across a wide range up to the spin-flop field. The collinear alignment between the Néel vector and phonon angular momenta induces strong excitation of magnons with high phonon dissipation, whereas orthogonal alignment suppresses dissipation, as revealed by R-SAW transmission. Our work uncovers a mutual interplay between phonon transport and antiferromagnetic order parameters, offering a broadband, low-loss route to manipulate antiferromagnetic dynamics.