Plasmonic electromagnetically-induced transparency in symmetric structures

A broken symmetry is generally believed to be a prerequisite of plasmonic electromagnetically-induced transparency (EIT), since the asymmetry renders the excitation of the otherwise forbidden dark mode possible. Nevertheless, according to the picture of magnetic-plasmon resonance (MPR) mediated plasmonic EIT, we show that the plasmonic EIT can be achieved even in the symmetric structures based on the second-order MPR. This sharpens our understanding of the existing concept, but also a profound insight into the plasmonic coherent interference in the near-field zone.