Chiral Phonons Arising From Chirality-Selective Magnon-Phonon Coupling

TL;DR

This paper demonstrates the emergence of truly chiral phonons from selective magnon-phonon coupling in magnetic systems, revealing their potential for spintronic applications and challenging traditional interpretations.

Contribution

It introduces a first-principles method to calculate hybridized magnon-phonon states and shows the widespread existence of chiral phonons in magnetic materials.

Findings

Finite zero-point phonon angular momentum observed.

Strong anomalous thermal Hall responses linked to Berry curvatures.

Chiral phonons are common in high-symmetry magnetic materials.

Abstract

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 example, we quantitatively calculate hybridized magnon-phonon quasiparticle states across the entire Brillouin zone utilizing first-principles calculations. Our findings challenge conventional magneto-elastic 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.