Unidirectional reflectionless propagation in borophene plasmonic metamaterials

We propose a nonreciprocal borophene metamaterial consisting of a longitudinally separated array of double-layer borophene nanoribbons (BNRs) suspended in the air, exhibiting the unidirectional reflectionless properties at exceptional points (EPs) in the near-infrared communication band. Based on the coupled mode theory and the transfer matrix method, the transmission characteristics of light in the proposed structure can be effectively described. The internal loss and radioactive loss factors of the plasmonic system are successfully calculated by employing the theoretical model we proposed. Thus we conduct the analytical description of the unidirectional reflectionless phenomenon between two borophene plasmonic resonators, where the analytical results show excellent consistency with the finite-difference time-domain simulations. Different from the waveguide structure, the proposed structure has better adjustability that the regulation of EPs can be dynamically achieved by manipulating carrier density and the spatial separation between double-layer of BNRs. Our research results possess the possibility for promising application in tunable nanoelectronic devices in the communication band.