Analogue of double-Λ-type atomic medium and vector plasmonic dromions in a metamaterial.

We consider an array of the meta-atom consisting of two cut-wires and a split-ring resonator coupled with an electromagnetic field with two polarization components. We show that the system can be taken as a classical analogue of the atomic medium of a double-Λ-type four-level configuration coupled with four laser fields and working under the condition of electromagnetically induced transparency, exhibits an effect of plasmon induced transparency (PIT), and displays a similar behavior of atomic four-wave mixing (FWM). We show also that with the PIT and FWM effects the system can support vector plasmonic dromions when a nonlinear varactor is mounted onto the each gap of the split-ring resonator. Our work not only gives a plasmonic analogue of the FWM in coherent atomic systems but also provides the possibility for obtaining new type of plasmonic excitations in metamaterials.