Study of Field Enhancement in the Subnanometer Gap of Plasmonic Dimers Accounting for the Surface Quantum Effect

Abstract

We investigate the influence of the surface quantum effect on the optical characteristics of a plasmonic dimer consisting of two identical gold nanoparticles with a tiny gap. To account for the corresponding surface quantum effect, an electromagnetic theory based on mesoscopic boundary conditions and surface response functions is used. It is shown that the quantum surface effect leads to a blue shift and damping of the corresponding plasmon resonance. This effect becomes more substantial when the constituent particles are elongated, and the gap size shrinks to subnanometer values. In this case, the difference in the results obtained using the surface response functions and the local response approximation can be up to four times and is accompanied by a spectral blue shift of 10 nm.