Manipulating topological states in multi-Weyl semimetals by off-resonant light: Theory and material realization

Employing time-periodic light to modulate physical properties of materials represents an effective strategy, known as Floquet engineering, which enables dynamic manipulation of electronic structures. In this paper, we investigate the dynamic behavior of multi-Weyl topological semimetals irradiated by circularly polarized light (CPL) in the off-resonant regime. Utilizing a minimal low-energy effective model, we reveal distinct evolutions of multi-Weyl points (WPs) under CPL incident from different directions. Since the stability of multi-WPs is usually ensured by a specific crystal symmetry, each multi-WP remains intact when this symmetry is preserved under the CPL, whereas the multi-WP splits into WPs with lower charge under symmetry-breaking CPL. This finding is explicitly exemplified by the celebrated double-Weyl semimetal ${\mathrm{HgCr}}_{2}{\mathrm{Se}}_{4}$. Furthermore, we have carried out first-principles analysis within the framework of Floquet theory to present the dynamical evolution of electronic structures of two realistic materials, namely, ${\mathrm{BaNiIO}}_{6}$ and cP-C24, hosting double and quadruple WPs, respectively. Remarkably, the first-principles results are in good consistence with our theoretical findings. In this paper, we reveal that light can trigger an abundance of topological states in multi-Weyl semimetals, which may hold promising prospects for application in optoelectronic devices.