Polarization- and angle-insensitive plasmon-induced transparency in four-fold symmetric graphene metamaterials

Plasmon-induced transparency (PIT) holds broad application prospects in terahertz functional devices, yet most reported PIT metamaterials operate effectively only under a single polarization state, severely restricting their use in complex electromagnetic environments. Here, a four-fold rotationally symmetric graphene metamaterial composed of one central disc and four corner quarter-circular discs is proposed, and its PIT response, underlying physical mechanism, and dynamically tunable performance are systematically investigated. A complementary structure is further constructed based on Babinet's principle to expand the PIT design methodology. The proposed structure achieves a robust polarization- and angle-insensitive PIT effect via bright-bright mode coupling; the transparency window can be dynamically modulated by the graphene Fermi level, and a pronounced slow-light effect-likewise insensitive to polarization and incidence angle is observed at the window. The complementary structure delivers a comparable high-performance PIT response with equally stable polarization and angle insensitivity. This work provides a highly adaptable design scheme for PIT metamaterials, offering a promising route toward environmentally robust terahertz sensors and optoelectronic components.