Nonlocal effects in atom-plasmon interactions

TL;DR

This paper investigates how nonlocal and quantum effects, modeled by surface-response functions, significantly influence quantum electrodynamic phenomena like Purcell enhancement and Lamb shift in noble metal nanostructures, especially at nanometer scales.

Contribution

It demonstrates the impact of surface-response functions on quantum emitter interactions near metal nanostructures and suggests experimental methods to determine these parameters.

Findings

SRFs significantly affect Purcell enhancement and Lamb shift.

Higher dielectric permittivity increases SRF effects.

Reducing metal width amplifies quantum electrodynamic phenomena.

Abstract

Nonlocal and quantum mechanical phenomena in noble metal nanostructures become increasingly crucial when the relevant length scales in hybrid nanostructures reach the few-nanometer regime. In practice, such mesoscopic effects at metal-dielectric interfaces can be described using exemplary surface-response functions (SRFs) embodied by the Feibelman $d$-parameters. Here we show that SRFs dramatically influence quantum electrodynamic phenomena -- such as the Purcell enhancement and Lamb shift -- for quantum emitters close to a diverse range of noble metal nanostructures interfacing different homogeneous media. Dielectric environments with higher permittivities are shown to increase the magnitude of SRFs calculated within the specular-reflection model. In parallel, the role of SRFs is enhanced in nanostructures characterized by large surface-to-volume ratios, such as thin planar metallic films or shells of core-shell nanoparticles. By investigating emitter quantum dynamics close to such plasmonic architectures, we show that decreasing the width of the metal region, or increasing the permittivity of the interfacing dielectric, leads to a significant change in the Purcell enhancement, Lamb shift, and visible far-field spontaneous emission spectrum, as an immediate consequence of SRFs. We anticipate that fitting the theoretically modelled spectra to experiments could allow for experimental determination of the $d$-parameters.