Radiative coupling between plasmon and electron-hole pairs in a metallic film based on extended Bohm-Pines theory

TL;DR

This paper develops an extended Bohm-Pines theory to explicitly model the radiative coupling between plasmons and electron-hole pairs in metallic films, explaining frequency-dependent hot carrier generation and improving understanding of energy conversion processes.

Contribution

It introduces a self-consistent, microscopic theory incorporating light-matter interactions and radiative corrections, revealing a new mechanism for hot carrier generation beyond Landau damping.

Findings

Predicts frequency-dependent radiative coupling between modes.

Explains the IQE peak near plasmon resonance.

Provides a unified framework for plasmon-induced hot carrier dynamics.

Abstract

Hot carrier generation in metals, where high-energy electron-hole pairs are produced via plasmon excitation, has emerged as a promising mechanism for photoelectric conversion and photocatalysis. However, conventional theories often describe this process through phenomenological relaxation via Landau damping, which fails to account for the microscopic origin of the frequency-dependent internal quantum efficiency (IQE) observed in experiments. To address this gap, we develop an extended Bohm-Pines theory for a metallic thin film that explicitly incorporates light-matter interactions within a non-local response framework. Our approach treats collective (plasmonic) and individual (electron-hole) excitations on equal footing and includes their coupling mediated by both longitudinal and transverse electromagnetic fields. This results in a self-consistent theory of the optical response of metallic films. The derived total Hamiltonian includes radiative corrections that recover the known dispersion of surface plasmon polaritons and, importantly, predict a frequency-dependent radiative coupling between collective and individual modes. This previously neglected transverse coupling naturally explains the IQE peak near the plasmon resonance and reveals a new mechanism of hot carrier generation distinct from conventional Landau damping. Our results provide a unified theoretical foundation for understanding plasmon-induced hot carrier dynamics and offer guidance for resonance-based photonic design strategies to enhance energy conversion efficiency in metal nanostructures.