Twinned plasmonic fano resonances in heterogeneous Au-Ag nanostructure consisting of a rod and concentric square ring-disk

In this paper, a heterogeneous Au-Ag nanostructure consisting of a rod and concentric square ring-disk is pro-posed to generate intense plasmonic Fano resonances. And the Fano resonance in plasmonic nanostructures is produced by the coupling between broad bright mode and narrow dark mode, causing a Fano dip in the scattering spectrum. One of the main characteristic of the Fano dip is the line width which can be reduced to 0.0135 eV in this nanostructure, and the local electric field enhancement factor can reach 64, which enables its promising applications in biosensing, detecting and surface-enhanced Raman scattering.