Conventional and Acoustic Surface Plasmons on Noble Metal Surfaces: A Time-dependent Density Functional Theory Study

TL;DR

This study uses first-principles time-dependent density functional theory to analyze surface plasmons on noble metal surfaces, revealing how interband transitions influence plasmon energies and providing results consistent with experimental data.

Contribution

It offers a detailed first-principles analysis of both conventional and acoustic surface plasmons on Cu, Ag, and Au surfaces, highlighting the impact of improved exchange-correlation potentials.

Findings

Plasmon energies follow the trend Cu<Au<Ag due to reduced screening.

ASP features are weak in EELS but identifiable in dielectric band structures.

Results align well with experimental electron energy loss spectroscopy data.

Abstract

First-principles calculations of the conventional and acoustic surface plasmons (CSPs and ASPs) on the (111) surfaces of Cu, Ag, and Au are presented. The effect of $s-d$ interband transitions on both types of plasmons is investigated by comparing results from the local density approximation and an orbital dependent exchange-correlation (xc) potential that improves the position and width of the $d$ bands. The plasmon dispersions calculated with the latter xc-potential agree well with electron energy loss spectroscopy (EELS) experiments. For both the CSP and ASP, the same trend of Cu$<$Au$<$Ag is found for the plasmon energies and is attributed to the reduced screening by interband transitions from Cu, to Au and Ag. This trend for the ASP, however, contradicts a previous model prediction. While the ASP is seen as a weak feature in the EELS, it can be clearly identified in the static and dynamic dielectric band structure.