# Observation of tunable charged exciton polaritons in hybrid monolayer WS2 $-$ plasmonic nanoantenna system

## TL;DR

This paper demonstrates tunable strong coupling between plasmons and charged excitons (trions) in monolayer WS2 coupled with silver nanoantennas, revealing stable trion polaritons at low temperature, opening new avenues in nanoscale light-matter interactions.

## Contribution

It reports the first observation of electrically charged trion polaritons in a hybrid plasmonic system, showing tunable coupling and stable trion states at low temperature.

## Key findings

- Tunable plasmon-trion coupling in WS2 monolayers.
- Emergence of stable trion polaritons at low temperature.
- Potential for electrically controllable light-matter states.

## Abstract

Formation of dressed light-matter states in optical structures, manifested as Rabi splitting of the eigen energies of a coupled system, is one of the key effects in quantum optics. In pursuing this regime with semiconductors, light is usually made to interact with excitons $-$ electrically neutral quasiparticles of semiconductors, meanwhile interactions with charged three-particle states $-$ trions $-$ have received little attention. Here, we report on strong interaction between plasmons in silver nanoprisms and charged excitons $-$ trions $-$ in monolayer tungsten disulphide (WS$_{2}$). We show that the plasmon-exciton interactions in this system can be efficiently tuned by controlling the charged versus neutral exciton contribution to the coupling process. In particular, we show that a stable trion state emerges and couples efficiently to the plasmon resonance at low temperature by forming three bright intermixed plasmon-exciton-trion polariton states. Our findings open up a possibility to exploit electrically charged trion polaritons $-$ previously unexplored mixed states of light and matter in nanoscale hybrid plasmonic systems.