Theoretical study of tunable spin-selective terahertz perfect absorption via dual-magnetic-dipoles resonance in an L-shaped metasurface

Spin-selective absorption metasurfaces for incident circularly polarized (CP) waves represent a significant research focus in optics. In this study, an L-shaped metasurface is proposed that achieves perfect spin-selective absorption in the terahertz (THz) band. Consequently, the absorption efficiencies for right-handed and lefthanded CP waves attain values of up to 99.9 % and 99.5 % at 0.28 THz and 0.35 THz, respectively. Correspondingly, maximum circular dichroism values of 0.85 and.86 are observed at the two resonant frequencies. Furthermore, two graphene strips were deposited on the upper surface of the dielectric substrate, demonstrating that both spin-selective absorption and circular dichroism can be flexibly tuned by altering the Fermi energy. The resulting metasurface, featuring tunable and spin-selective perfect absorption properties, holds promise for applications in wireless communications, terahertz sensing, and imaging.