Spatial Exciton Localization at Interfaces of Metal Nanoparticles and Atomically Thin Semiconductors

TL;DR

This paper develops a theoretical framework to analyze how excitons in atomically thin semiconductors become spatially localized at interfaces with metal nanoparticles due to strong exciton-plasmon coupling, revealing bound states and characteristic optical signatures.

Contribution

It introduces a self-consistent Maxwell-Bloch model that analytically describes exciton localization and strong coupling effects at metal nanoparticle and monolayer semiconductor interfaces.

Findings

Identification of bound exciton states in plasmon-induced potentials

Observation of avoided crossing and Rabi splitting in optical spectra

Quantitative analysis of exciton-plasmon coupling strength

Abstract

We present a self-consistent Maxwell-Bloch theory to analytically study the interaction between a nanostructure consisting of a metal nanoparticle and a monolayer of transition metal dichalcogenide. For the combined system, we identify an effective eigenvalue equation that governs the center-of-mass motion of the dressed excitons in a plasmon-induced potential. Examination of the dynamical equation of the exciton-plasmon hybrid reveals the existence of bound states with negative eigenenergies, which we interpret as excitons localized in the plasmon-induced potential. The appearance of these bound states in the potential indicates strong coupling between excitons and plasmons. We quantify this coupling regime by computing the scattered light in the near-field explicitly and identify signatures of strong exciton-plasmon coupling with an avoided crossing behavior and an effective Rabi splitting of tens of meV.