Exceptional point in a terahertz graphene metasurface

Exceptional points (EPs) are special state points in a non-Hermitian system, at which both the eigenvalues and the eigenstates of the system coalesce. The parameter space around it often presents peculiar physical phenomena, such as greatly improved sensitivity. In this paper, a non-Hermitian metasurface based on patterned graphene in the terahertz frequency range is designed. Its unit cell consists of a pair of orthogonally oriented graphene split-ring-resonators with different geometries, which makes it a non-Parity-time (PT) symmetric system. The existence of the EPs is further confirmed by the coincident eigenstate polarizations and eigen transmission exchange behaviors. This work provides a basis platform for studying EP points in a graphene metasurface.