Transition metal impurity-induced generation of plasmonic collective modes in small gold clusters

TL;DR

This study investigates how doping small gold chains with transition metals affects their plasmonic modes, revealing the emergence of local plasmonic peaks and potential for tuning optical properties in nanotechnology.

Contribution

It demonstrates the generation of local plasmonic modes in small gold chains doped with transition metals, a behavior opposite to larger bulk clusters, offering new ways to tune nanoscale optical properties.

Findings

Doped gold chains exhibit a split in plasmon peaks with certain TM atoms.

Local plasmonic modes are associated with charge oscillations around impurity d-orbitals.

The effect is prominent when the number of TM atoms is much smaller than Au atoms.

Abstract

We study the optical properties of small gold chains doped with different transition metal (TM) atoms (Ni,Rh,Fe) by using the time-dependent density-functional theory (TDDFT) approach. The optical absorption spectrum of such systems demonstrates a collective plasmon mode when the number of atoms is larger than approximately 10, and this mode splits into two peaks when the Au chain is doped with some of the TM (Ni,Fe) atoms. We associate the additional peak with a local plasmonic mode which corresponds to the charge oscillations around the potential created by the d-orbitals of the impurity atoms. The effect takes place when the number of TM atoms is much smaller than the number of Au atoms. This behavior is opposite to the case of larger bulk noble-metal-TM clusters (radius $>$1nm), where the doping with TM atoms does not lead to any generation of additional modes, and often leads to a suppression of the main plasmon peak. This phenomenon of tuning the optical properties of nanosystems with transition metal atoms can be used in many practical applications in the field of nanotechnology.