Microscopic origins of hydrodynamic transport in the type-II Weyl semimetal WP2

A microscopic understanding of hydrodynamic transport in Dirac and Weyl semimetals has remained elusive in theoretical descriptions and experimental measurements. We investigate the structure and microscopic properties of transport in WP2, a type-II Weyl semimetal exhibiting hydrodynamic transport. Here, we characterize the nature of the microscopic properties of WP2 as a function of temperature through ab initio calculations of the relevant scattering processes, including electron-phonon and electron-electron lifetimes, and provide equivalent calculations for copper as a point of reference. Additionally, we present an approach to calculate phonon drag, a mechanism invoked in recent experiments, through predictions of a phonon-mediated electron-electron lifetime. We show that the resistivity is very well described by the electron-phonon interaction alone, indicating WP2 exhibits conventional metallic electrical behavior in which strong electron-electron correlations do not play a significant role. After establishing the zone-averaged behavior of the calculated lifetimes, we further investigate specific features of the spatial distribution of the electron-phonon lifetime across the Fermi surfaces of WP2 to study possible scattering channels involved in hydrodynamic transport and quantify the degree of lifetime anisotropy in electron and hole pockets. This description of microscopic dynamics in WP2 prompts additional investigation of specific scattering channels and indicates the importance of phonon interactions in understanding connections between transport in hydrodynamic materials and strongly correlated systems including unconventional metals.