Manipulating Coherent Light Matter Interaction: Continuous Transition between Strong Coupling and Weak Coupling in MoS2 Monolayer Coupled with Plasmonic Nanocavities

TL;DR

This paper demonstrates a controllable transition from weak to strong plasmon-exciton coupling in MoS2 monolayer nanocavities, achieving record Rabi splitting and providing design guidelines for polariton devices at room temperature.

Contribution

It introduces a method to continuously tune coupling regimes in MoS2-plasmonic nanocavities and reports the largest Rabi splitting in 2D materials at room temperature.

Findings

1570-fold photoluminescence enhancement at weak coupling

Room temperature polariton formation with 190 meV Rabi splitting

Numerical model linking coupling strength to spacer thickness

Abstract

Strong interactions between surface plasmons in ultra-compact nanocavities and excitons in two dimensional materials have attracted wide interests for its prospective realization of polariton devices at room temperature. Here, we propose a continuous transition from weak coupling to strong coupling between excitons in MoS2 monolayer and highly localized plasmons in ultra-compact nanoantenna. The nanoantenna is assembled by a silver nanocube positioned over a gold film and separated by a dielectric spacer layer. We observed a 1570-fold enhancement in the photoluminescence at weak coupling regime in hybrid nanocavities with thick spacer layers. The interaction between excitons and plasmons is then directly prompted to strong coupling regime by shrinking down the thickness of spacer layer. Room temperature formation of polaritons with Rabi splitting up to 190 meV was observed, which is the largest plasmon-exciton Rabi splitting reported in two dimensional materials. Numerical calculations quantified the relation between coupling strength, local density of states and spacer thickness, and revealed the transition between weak coupling and strong coupling in nanocavities. The findings in this work offer a guideline for feasible designs of plasmon-exciton interaction systems with gap plasmonic cavities.