Terahertz nonlinear optical response from transition metal monopnictide Weyl semimetal TaAs

Weyl semimetals are a newly discovered class of materials whose low-energy excitations are massless chiral fermions known as Weyl fermions. It has recently been shown that the transition metal monopnictide (TMMP) family of Weyl semimetals has a giant anisotropic nonlinear optical response, [arXiv:1609.04894] as revealed by optical second harmonic generation. We report here the nonlinear response of the TMMP TaAs through optical rectification of amplified femtosecond laser radiation, a phenomenon related to photogalvanic and nonlinear Hall effects. The emitted rectified radiation is in the Terahertz energy range of around 4 meV and allows us to study electron dynamics close to the Fermi surface.