# Plasmon-Emitter Interactions at the Nanoscale

## TL;DR

This paper develops a unified mesoscopic electrodynamics framework using Feibelman d-parameters to accurately model plasmon-emitter interactions at the nanoscale, including quantum effects like nonlocality and Landau damping.

## Contribution

It introduces a comprehensive theoretical approach that incorporates nonclassical effects into plasmon-emitter interaction modeling at sub-20 nm separations.

## Key findings

- Accurately models resonance shifts due to quantum effects.
- Accounts for surface-enabled Landau damping.
- Provides a general platform for nanoplasmonic phenomena.

## Abstract

Plasmon-emitter interactions are of paramount importance in modern nanoplasmonics and are generally maximal at short emitter-surface separations. However, when the separation falls below 10-20 nm, the classical theory progressively deteriorates due to its neglect of quantum mechanical effects such as nonlocality, electronic spill-out, and Landau damping. Here, we show how this neglect can be remedied by presenting a unified theoretical treatment of mesoscopic electrodynamics grounded on the framework of Feibelman $d$-parameters. Crucially, our technique naturally incorporates nonclassical resonance shifts and surface-enabled Landau damping - a nonlocal damping effect - which have a dramatic impact on the amplitude and spectral distribution of plasmon-emitter interactions. We consider a broad array of plasmon-emitter interactions ranging from dipolar and multipolar spontaneous emission enhancement, to plasmon-assisted energy transfer and enhancement of two-photon transitions. The formalism presented here gives a complete account of both plasmons and plasmon-emitter interactions at the nanoscale, constituting a simple yet rigorous and general platform to incorporate nonclassical effects in plasmon-empowered nanophotonic phenomena.