Extending exciton and trion lifetimes in MoSe$_{2}$ with a nanoscale plasmonic cavity

TL;DR

This paper demonstrates that placing MoSe2 in a nanoscale plasmonic cavity extends exciton and trion lifetimes by suppressing radiative decay, enabling better control of excited states in 2D materials for optoelectronic applications.

Contribution

It introduces an all-optical method using a deep-subwavelength Fabry-Perot silver cavity to significantly extend exciton and trion lifetimes in MoSe2, a novel approach in 2D material engineering.

Findings

PL linewidths of excitons and trions decreased to ~1 nm

Exciton and trion lifetimes increased by approximately 10 ps

Removing the cavity restores original PL linewidths and lifetimes

Abstract

Excitons in transition metal dichalcogenides (TMDs) have extremely short, picosecond-scale lifetimes which hinders exciton thermalization, limits the emergence of collective coherence, and reduces exciton transport in optoelectronic devices. In this work, we explore an all-optical pathway to extend exciton lifetimes by placing MoSe$_2$ in a deep-subwavelength Fabry-Perot silver cavity. The cavity structure is designed to suppress radiative recombination from in-plane optical dipoles, such as bright excitons and trions. We observe a consistent decrease in photoluminescence (PL) linewidths of excitons and trions (~1 nm), along with a corresponding lifetime increase (~10 ps). We confirm the experimental observations arise purely from exciton-cavity interactions-etching back the top silver layer returns the PL linewidth and lifetimes return to their original values. Our study offers a pathway to engineer excited state lifetimes in 2D materials which can be utilized for studies of optically dark excitons and have potential applications for novel optoelectronic devices.