Anomalous sound attenuation in Weyl semimetals in magnetic and pseudomagnetic fields

TL;DR

This paper investigates how magnetic and pseudomagnetic fields influence sound attenuation in Weyl semimetals, revealing effects like magnetic sound dichroism and strain-induced attenuation changes due to complex scattering and screening interactions.

Contribution

It introduces the concept of magnetic sound dichroism in Weyl semimetals and explores how pseudomagnetic fields from strain can activate and modify sound attenuation.

Findings

Fields generally reduce sound absorption in Weyl semimetals.

Directional dependence leads to magnetic sound dichroism.

Strain-induced pseudomagnetic fields can activate dichroism.

Abstract

We evaluate the sound attenuation in a Weyl semimetal subject to a magnetic field or a pseudomagnetic field associated with a strain. Due to the interplay of intra- and inter-node scattering processes as well as screening, the fields generically reduce the sound absorption. A nontrivial dependence on the relative direction of the magnetic field and the sound wave vector, i.e., the magnetic sound dichroism, can occur in materials with nonsymmetric Weyl nodes (e.g., different Fermi velocities and/or relaxation times). It is found that the sound dichroism in Weyl materials can also be activated by an external strain-induced pseudomagnetic field. In view of the dependence on the field direction, the dichroism may lead to a weak enhancement of the sound attenuation compared with its value at vanishing fields.