Slowing Down Surface Plasmons on a Moire Surface

We have demonstrated slow propagation of surface plasmons on metallic Moire surfaces. The phase shift at the node of the Moire surface localizes the propagating surface plasmons and adjacent nodes form weakly coupled plasmonic cavities. Group velocities around v(g)=0.44c at the center of the coupled cavity band and almost a zero group velocity at the band edges are observed. A tight binding model is used to understand the coupling behavior. Furthermore, the sinusoidally modified amplitude about the node suppresses the radiation losses and reveals a relatively high quality factor (Q=103).