  Weyl semimetals are materials with topologically nontrivial band structure
both in the bulk and on the surface, hosting chiral nodes which are sinks and
sources of Berry curvature. Weyl semimetals have been predicted, and recently
measured, to exhibit large nonlinear optical responses. This discovery, along
with their high mobilities, makes Weyl semimetals relevant to a broad spectrum
of applications in optoelectronic, nanophotonic and quantum optical devices.
While there is growing interest in understanding and characterizing the linear
and nonlinear behavior of Weyl semimetals, an ab initio calculation of the
linear optical and optoelectronic responses at finite temperature remains
largely unexplored. Here, we specifically address the temperature dependence of
the linear optical response in type-I Weyl semimetals TaAs and NbAs. We
evaluate from first principles the scattering lifetimes due to electron-phonon
and electron-electron interaction and incorporate these lifetimes in evaluating
an experimentally relevant frequency-, polarization- and temperature-dependent
complex dielectric function for each semimetal. From these calculations we
present linear optical conductivity predictions which agree well where
experiment exists (for TaAs) and guide the way for future measurements of
type-I Weyl semimetals. Importantly, we also examine the optical conductivity's
dependence on the chemical potential, a crucial physical parameter which can be
controlled experimentally and can elucidate the role of the Weyl nodes in
optoelectronic response. Through this work, we present design principles for
Weyl optoelectronic devices that use photogenerated carriers in type-I Weyl
semimetals.
