Circular phonon dichroism in Weyl semimetals

TL;DR

This paper explores how strong spin-orbit coupling in magnetic Weyl semimetals leads to circular phonon dichroism, enabling control over phonon polarization through dissipationless and dissipative viscosities.

Contribution

It derives the phonon dynamics in magnetic metals with spin-orbit coupling, revealing a new mechanism for manipulating phonon polarization via circular dichroism in Weyl semimetals.

Findings

Strong circular phonon dichroism in Weyl semimetals breaking time-reversal and inversion symmetry

Dissipationless viscosity causes splitting of left- and right-handed phonon dispersion

Dissipative viscosity results in differential damping of circularly polarized phonons

Abstract

We derive the phonon dynamics of magnetic metals in the presence of strong spin-orbit coupling. We show that both a dissipationless viscosity and a dissipative viscosity arise in the dynamics. While the dissipationless viscosity splits the dispersion of left-handed and right-handed circularly polarized phonons, the dissipative viscosity damps them differently, inducing circular phonon dichroism. The effect offers a new degree of manipulation of phonons, i.e., the control of the phonon polarization. We investigate the effect in Weyl semimetals. We find that there exists strong circular phonon dichroism in Weyl semimetals breaking both the time-reversal and the inversion symmetry, making them potential materials for realizing the acoustic circular polarizer.