Modeling and measuring plasmonic excitations in hollow spherical gold nanoparticles.

Marvin M Müller,Christof Holzer,Carsten Rockstuhl,Nanda Perdana

doi:10.1063/5.0078230

Marvin M Müller, Christof Holzer + Show 2 more

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https://doi.org/10.1063/5.0078230

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Abstract

We investigate molecular plasmonic excitations sustained in hollow spherical gold nanoparticles using time-dependent density functional theory (TD-DFT). Specifically, we consider Au60 spherical, hollow molecules as a toy model for single-shell plasmonic molecules. To quantify the plasmonic character of the excitations obtained from TD-DFT, the energy-based plasmonicity index is generalized to the framework of DFT, validated on simple systems such as the sodium Na20 chain and the silver Ag20 compound, and subsequently successfully applied to more complex molecules. We also compare the quantum mechanical TD-DFT simulations to those obtained from a classical Mie theory that relies on macroscopic electrodynamics to model the light-matter interaction. This comparison allows us to distinguish those features that can be explained classically from those that require a quantum-mechanical treatment. Finally, a double-shell system obtained by placing a C60 buckyball inside the hollow spherical gold particle is further considered. It is found that the double-shell, while increasing the overall plasmonic character of the excitations, leads to significantly lowered absorption cross sections.

Highlights

Plasmonics has become an increasingly important topic that has gathered significant momentum in the past decades.[1,2,3] More recently, the field of plasmonics has expanded toward quantum technology, focusing on quantum effects that get more important as the size of nanostructures keeps shrinking evermore.[4,5,6,7] When quantum effects become relevant, the need for ab initio methods to describe these effects immediately emerges
We investigate molecular plasmonic excitations sustained in hollow spherical gold nanoparticles using time-dependent density functional theory (TD-DFT)
To quantify the plasmonic character of the excitations obtained from TD-DFT, the energy-based plasmonicity index (EPI) is generalized to the framework of DFT, validated on simple systems like the sodium Na20 chain and the silver Ag20 compound, and subsequently successfully applied to more complex molecules

Summary

Introduction

Plasmonics has become an increasingly important topic that has gathered significant momentum in the past decades.[1,2,3] More recently, the field of plasmonics has expanded toward quantum technology, focusing on quantum effects that get more important as the size of nanostructures keeps shrinking evermore.[4,5,6,7] When quantum effects become relevant, the need for ab initio methods to describe these effects immediately emerges. There is a need for suitable reference model systems that can be used to evaluate and test certain properties and to benchmark the performances of different calculation methods These systems should be small enough for many ab initio methods to be applicable to, yet at least to some extent similar and comparable to actual materials that plasmonics is mainly concerned with. A method capable of the latter optimally is a simple automatized post-processing tool that evaluates a given mode a posteriori at virtually no additional cost if the question arises whether a said mode is mainly of single-particle or plasmonic character. This contribution aims to meet both needs mentioned above

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