Chiral Phonons Arising from Chirality-Selective Magnon-Phonon Coupling.

Chiral phonons are desirable for applications in spintronics but their generation and control remains a challenge. Here we demonstrate the emergence of truly chiral phonons from selective magnon-phonon coupling in inversion-symmetric magnetic systems. Considering bcc Fe as an example, we quantitatively calculate hybridized magnon-phonon quasiparticle states across the entire Brillouin zone utilizing first-principles calculations. Our findings challenge conventional magnetoelastic interpretations and reveal finite zero-point phonon angular momentum and strong anomalous thermal Hall responses linked to finite (spin) Berry curvatures. Our results further establish that the existence of chiral phonons, particularly along high-symmetry directions, is common in many magnetic materials, offering promising avenues for novel spintronic and phononic devices.