Tunable spin splitting of reflected vortex-beam of Weyl semimetal metasurface with stronger optical activity

This work investigated the spin splitting of a reflected beam with a vortex beam irradiating on a metasurface. This metasurface structure is the periodically rectangular-groove array of ionic crystal, where the array is a sub-wavelength grating with its periodical direction situated in the surface plane. In the grating structure, we embedded magnetic Weyl semimetals. Consequently, a stronger optical activity can be found, which originates from the unique electronic structure of Weyl semimetals and the orientation of the grating arrangement. By controlling the separation of Weyl points and grating orientation, we observe notable asymmetric spin splitting in different frequency ranges with distinctly unique distributions. Significant spin splitting was observed to be correlated with substantial Kerr rotation angles and reflectance differences, indicating strong optical activity. Additionally, with the increasing topological charges, the spin splitting increases significantly. Our results are useful for the manipulation of infrared radiations and infrared optical detection. •Stronger optical activity can be found in this metasurface structure, which originates from the unique electronic structure of Weyl semimetals and the direction of the grating arrangement.•Large Kerr rotation angles and reflectance differences corresponds to the significant spin splitting.•Both the separation of two Weyl points and the orientation angle can significantly modulate the optical activity of the structure and realize the tunable spin splitting.•The spin splitting is also significantly enhanced with the increase of IOAM of vortex beam. In addition, unique intensity and phase distribution SP are formed on the metasurface.