Floquet engineering of topological semimetals with bicircularly polarized light

We study the effect of illumination of bicircularly polarized light (BCL) on topological semimetals, namely multifold fermion and line-node semimetals. We demonstrate, by means of both low-energy and lattice models, that the band-structures of both multifold fermions and line-node semimetal exhibit rich features with BCL illumination. For multifold fermions, we show that if the relative amplitude, r, between the two frequency components of the BCL is related to the relative frequency, eta, in such a way that r2=eta, then the band touching points remain unchanged without any shift or band gap opening for any choice of the material-dependent parameters. For other choices of the BCL parameters, we find both gapped phases as well as gapless phases with shifted band touching points. Line-node semimetals also exhibit diverse phases, ranging from protected line-nodes under illumination to point nodes, by tuning the BCL parameters r and eta. Overall, our analytical and numerical results establish BCL as a versatile tool for obtaining tunable topological phases which can be potentially observed in future experiments with BCL.