On the existence of a local dipolar plasmon mode in doped small gold atomic arrays

Abstract

Impurity doping in atomic chains provides a potentially effective way to adjust its electronic excitation. Recently, it was reported that doping transition-metal atoms into small gold atomic chains induces a local dipolar plasmon mode which corresponds to charge oscillations around the impurity atoms, whereas our studies indicate that such a local mode does not exist. In this paper, using time-dependent density functional theory, we extensively investigate the excitation properties of plasmons in doped gold nanostructures. Our results show that all the plasmon peaks are affected by impurity, and the corresponding plasmon modes mutate into different forms compared to pure gold atomic chains. The propagation of charge oscillations in some plasmon modes is blocked in the doped chain, so that the charges oscillate mainly in half of the chain. Furthermore, the $5d$ electrons of gold atoms reduce the energies and intensities of plasmon resonances for both the transverse and longitudinal modes, and cause the end and center features of the induced charge distributions to nearly vanish in the transverse plasmon modes.