Geometry contribution to sound attenuation in double-Weyl semimetals

The axial coupling of strain to the nodes of the simple Weyl semimetals leads to anomalous contributions to sound attenuation in such materials. However, in double Weyl semimetals, there is no such axial coupling. Strain instead couples as a symmetry-breaking director field that deforms the Fermi surface around each Weyl node. In this work, we show that absence of axial coupling in double Weyl semimetals implies a very different mechanism of relaxation due to sound. The deformed geometry of the Fermi surface is the only source of sound attenuation under these conditions. Thus, we identify a geometric contribution to sound attenuation in double Weyl semimetals that is entirely absent in simple Weyl semimetals.