The Strain Impact on Weyl Semimetals

Abstract

Weyl semimetals are a class of topological semimetals defined by a Chern number as their topological invariant. These materials exhibit unique properties, such as transverse topological currents and anomalous magnetoelectric responses, making them promising candidates for device applications.This thesis explores the effects of strain on the electronic properties of Weyl semimetals using both toy models and first-principles calculations, specifically density functional theory (DFT) combined with the Wannier method. We investigated the strain effects on two-band tight-binding toy models by tuning their hopping integrals. To connect these models to real materials, we derived a tight-binding Hamiltonian from DFT combined with Wannier functions and analyzed the surface states and density of states under varying strain conditions. Our results reveal that both tensile and compressive strains significantly alter the electronic structure of TaAs, potentially inducing topological phase transitions. Specifically, tensile strain along the [100] direction leads to the transformation and eventual disappearance of Fermi arcs, while compressive strain results in the formation of complex surface states, suggesting the emergence of a new phase at higher strain levels.