Floquet multi-Weyl points in crossing-nodal-line semimetals

Weyl points with monopole charge ±1 have been extensively studied; however, real materials of multi-Weyl points, whose monopole charges are higher than 1, have yet to be found. In this Rapid Communication, we show that nodal-line semimetals with nontrivial line connectivity provide natural platforms for realizing Floquet multi-Weyl points. In particular, we show that driving crossing nodal lines by circularly polarized light generates double-Weyl points. Furthermore, we show that monopole combination and annihilation can be observed in crossing-nodal-line semimetals and nodal-chain semimetals. These proposals can be experimentally verified in pump-probe angle-resolved photoemission spectroscopy.