Charge-Transfer Plasmon Resonance in a Dimer of Gold Nanoparticles Connected with a Carbon Nanotube

The scattering problem for a dimer consisting of a carbon nanotube (CNT) coated with a thick gold layer everywhere except for a narrow central region is solved in the far-IR range by numerical methods. The nanotube in such a dimer is a low-conductive channel that slows the flow of charges between the two parts of the highly conductive gold coating. Charge-transfer plasmon resonance arises at a frequency of 21 THz in the spectrum of the absorption cross section of a dimer with a length of 285 nm and a transverse size of 20 nm. The resonance width is determined by the electron relaxation time in the CNTs. The resonant frequency is shown to decrease and the absorption cross section at the resonant frequency, to increase with increases in the transverse and longitudinal dimensions of the dimer. The presence of contact resistance between the CNT and the gold layer leads to a shift of the resonant frequency to the low-frequency region and a decrease in the absorption peak intensity. The ability to vary the CNT conductivity by electrostatic doping makes it possible to use such dimers as building blocks for metamaterials with controlled resonant properties in the far-IR range.