Charge transfer plasmons in the arrays of nanoparticles connected by conductive linkers

Charge transfer plasmons (CTPs) that occur in different topology and dimensionality arrays of metallic nanoparticles (NPs) linked by narrow molecular bridges are studied. The occurrence of CTPs in such arrays is related to the ballistic motion of electrons in thin linkers with the conductivity that is purely imaginary, in contrast to the case of conventional CTPs, where metallic NPs are linked by thick bridges with the real optical conductivity caused by carrier scattering. An original hybrid model for describing the CTPs with such linkers has been further developed. For different NP arrays, either a general analytical expression or a numerical solution has been obtained for the CTP frequencies. It has been shown that the CTP frequencies lie in the IR spectral range and depend on both the linker conductivity and the system geometry. It is found that the electron currents of plasmon oscillations correspond to minor charge displacements of only few electrons. It has been established that the interaction of the CTPs with an external electromagnetic field strongly depends on the symmetry of the electron currents in the linkers, which, in turn, are fully governed by the symmetry of the investigated system. The extended model and the analytical expressions for the CTPs frequencies have been compared with the conventional finite difference time domain simulations. It is argued that applications of this novel type of plasmon may have wide ramifications in the area of chemical sensing.