Effects of electron-phonon coupling on the phonon transport properties of the Weyl semimetals NbAs and TaAs: A comparative study

Abstract

It has now become recognized that the electron-phonon coupling (EPC) may play an important role in governing the phonon transport, especially for metallic and semiconducting systems at high carrier concentration. Here we focus on the Weyl semimetals TaAs and NbAs and give a comparative study on their phonon transport properties by explicitly including the EPC in first-principles calculations. It is found that the lattice thermal conductivities of both systems are significantly reduced by the EPC, which is more pronounced for the TaAs compared with the NbAs at the same carrier concentration. Detailed analysis indicates that the TaAs exhibits smaller EPC phonon relaxation time, as characterized by stronger EPC strength which is associated with larger deformation potential constant and Born effective charge. Moreover, we see that the TaAs exhibits obviously larger overlap between the EPC relaxation time and that from intrinsic phonon-phonon scattering, which could further reduce the lattice thermal conductivity. Our work not only highlights the vital importance of EPC in accurately predicting the phonon transport behaviors, but also offers a simple alternative to evaluate the EPC strength of various material systems.

Keywords

• Electron-phonon coupling
• Phonon transport
• Weyl semimetals
• First-principles
• Lattice thermal conductivity