Extremely asymmetric absorption and reflection near the exceptional point of three-dimensional metamaterial

In recent years, particular physical phenomena caused by exceptional points (EPs) in non-Hermitian systems have attracted significant research interests. In this paper, a non-Hermitian three-dimensional metamaterial near the EP with extremely asymmetric absorption and reflection is proposed. Unlike the conventional non-Hermitian system, this metamaterial system is constructed with a loss-assisted unique design. By tuning the anisotropic radiation loss between split ring resonator (SRR) in the meta-atoms, extremely asymmetric absorption and reflection unique to EPs are observed. This phenomenon is verified theoretically and experimentally where the theoretical framework of non-Hermitian physics is utilized to explain the formation of EP in the system. By linking the equivalent circuit model (ECM) with the Hamiltonian quantum physical model, a non-Hermitian transmission matrix is constructed. Finally, an analysis method based on the ECM is established. It is demonstrated in a synthetic dimension that the conventional equivalent circuit theory can be utilized to construct non-Hermitian systems. Our work lays down the way for the manipulation of EP to develop perfect absorption, sensing and other applications in the 3D metamaterial platform.