An ab-initio study of nodal-arcs, axial strain's effect on nodal-lines Weyl nodes and Weyl-contributed Seebeck coefficient in TaAs class of Weyl semimetals

This work verifies the existence of dispersive nodal-arcs and their evolution into Weyl nodes under the effect of spin-orbit coupling (SOC) in NbAs NbP. The obtained features mimic the observations as reported for TaAs TaP in our previous work. In addition, this work reports that the number of nodes in TaAs class of Weyl semimetals (WSMs) can be altered via creating strain along a or c direction of the crystal. For instance, the number of nodes in NbAs under SOC-effect along with 2 found to be 40 (56) in its full Brillouin zone (BZ). Besides the nodes, such strain are found to have considerable impact on the nodal-lines of these WSMs when effect of SOC is ignored. A 3% tensile (compressive) strain along the a (c) direction leads to the partially merging of nodal-lines (without SOC) in the extended BZ of NbAs & NbP, which is not observed in TaAs TaP within the range of -3 physics in affecting the Seebeck coefficient (S) of any WSM. In this direction, it is discussed that how a symmetric Weyl cone, even if tilted, will have no contribution to the S of WSMs. Furthermore, the work highlights the conditions under which a Weyl cone can contribute to the S of a given WSM. Lastly, the discussion of Weyl contribution to S is validated over TaAs class of WSMs via investigating the features of their Weyl cones and calculating the contributions of such cones to the S of these semimetals. The value of S contributed from Weyl cone is found to be as large as ∼65 μV/K below 25 K in case of TaAs. The findings of this work present a possibility of engineering the topological properties of TaAs class of WSMs via creating strain in their crystal. It also makes the picture of Weyl physics impact on the S of WSMs a more clear.