Spectral imaging of topological edge states in plasmonic waveguide   arrays
  We report on the observation of a topologically protected edge state at the interface between two topologically distinct domains of the Su-Schrieffer-Heeger model, which we implement in arrays of evanescently coupled dielectric-loaded surface plasmon polariton waveguides. Direct evidence of the topological character of the edge state is obtained through several independent experiments: Its spatial localization at the interface as well as the restriction to one sublattice is confirmed by real-space leakage radiation microscopy. The corresponding momentum-resolved spectrum obtained by Fourier imaging reveals the midgap position of the edge state as predicted by theory. 
Felix Bleckmann, Zlata Cherpakova, Stefan Linden, and Andrea Alberti
quant-ph cond-mat.mes-hall physics.optics