Floquet Spectrum in Weyl semimetal via a One-Photon Resonance

Weyl semimetal such as {\$}AsTa{\$} is a new kind of topological material which is protected from small perturbation. In the vicinity of one Weyl point, the linear dispersion indicates that the low-energy excitation is a 3D massless quasi-particle. Usually a photon perturbation could cause a dynamic gap at the resonance energy, however, in Weyl semimetal we find that the dynamic gap stays gapless no matter the form of the perturbation. We also investigate the topology of the dynamic gapless spectrum.