Anomalous sound attenuation in Weyl semimetals in magnetic and pseudomagnetic fields

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 internode 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.