Plasmonic excitations in noble metals: The case of Ag

TL;DR

This paper investigates plasmonic excitations in noble metals, especially silver, using ab initio calculations and a simple model to explain the unique sharp resonance at 3.8 eV in silver and its absence in other noble metals.

Contribution

It provides a detailed analysis of the band structure effects on plasmonic resonances in noble metals, highlighting the unique behavior of silver compared to others.

Findings

Silver exhibits a sharp plasmonic resonance at 3.8 eV.

Band structure effects determine the existence of subthreshold plasmonic modes.

Other noble metals do not show this sharp resonance due to different band structures.

Abstract

The delicate interplay between plasmonic excitations and interband transitions in noble metals is described by means of {\it ab initio} calculations and a simple model in which the conduction electron plasmon is coupled to the continuum of electron-hole pairs. Band structure effects, specially the energy at which the excitation of the $d$-like bands takes place, determine the existence of a subthreshold plasmonic mode, which manifests itself in Ag as a sharp resonance at 3.8 eV. However, such a resonance is not observed in the other noble metals. Here, this different behavior is also analyzed and an explanation is provided.