Topological Singularity Induced Chiral Kohn Anomaly in a Weyl Semimetal*

The way electrons interact with phonons determines many physical processes that occur within electronic devices and material systems, but it has been difficult to investigate due to the weak strength of the electron-phonon interaction (EPI). An unusual kind of EPI is the Kohn anomaly, first discovered in the 1950s, whereby phonon softening is observed due to the divergence of the electron screening. This has been previously observed in several material systems, ranging from elemental metals to carbon-based allotropes, but not yet in topological materials whose topology imparts an inherent robustness against perturbations. In this talk, I will describe the observation of a chiral Kohn anomaly in the Weyl semimetal tantalum phosphide using inelastic x-ray and neutron scattering, which were guided upon by theoretical calculations [1]. In particular, the strong agreement between theory and calculations related to the unique features of Kohn anomalies in this topological material can help shed light on the strength of the EPI and on fundamental processes that would underlie some of these exotic materials.

[1] Nguyen, T. et al. Phys. Rev. Lett. 124, 236401 (2020).