Highly nonlinear trion-polaritons in a monolayer semiconductor

R P A Emmanuele,V Shahnazaryan,M S Skolnick,A Catanzaro,F A Benimetskiy,I A Shelykh,F Withers,A I Tartakovskii,P M Walker,D N Krizhanovskii,M Sich,O Kyriienko

doi:10.1038/s41467-020-17340-z

Abstract

Highly nonlinear optical materials with strong effective photon-photon interactions are required for ultrafast and quantum optical signal processing circuitry. Here we report strong Kerr-like nonlinearities by employing efficient optical transitions of charged excitons (trions) observed in semiconducting transition metal dichalcogenides (TMDCs). By hybridising trions in monolayer MoSe2 at low electron densities with a microcavity mode, we realise trion-polaritons exhibiting significant energy shifts at small photon fluxes due to phase space filling. We find the ratio of trion- to neutral exciton–polariton interaction strength is in the range from 10 to 100 in TMDC materials and that trion-polariton nonlinearity is comparable to that in other polariton systems. The results are in good agreement with a theory accounting for the composite nature of excitons and trions and deviation of their statistics from that of ideal bosons and fermions. Our findings open a way to scalable quantum optics applications with TMDCs.

Highlights

Nonlinear optical materials with strong effective photon-photon interactions are required for ultrafast and quantum optical signal processing circuitry
The large oscillator strength of trions enables formation of well-resolved trion-polariton resonances[24] at relatively small electron density[21,25], which, as we show here, leads to a pronounced phase space filling effect enabling nonlinearity of one to two orders of magnitude bigger than that of neutral exciton–polaritons in transition metal dichalcogenides (TMDCs) platform
The nonlinear refractive index (n2) per single TMDC monolayer due to trion-polaritons is estimated to be three to five orders of magnitude greater than in bare 2D TMDC materials and graphene studied in the weak light–matter coupling regime

Summary

Introduction

Nonlinear optical materials with strong effective photon-photon interactions are required for ultrafast and quantum optical signal processing circuitry. Interaction-based effects such as polariton Bose–Einstein condensation and superfluidity[6], solitons[12], quantum emission[11,13,14] as well as polariton transistors/ switches[15,16] have been reported Layered materials such as graphene and transition metal dichalcogenides (TMDCs)[17] have arisen as very promising optically active 2D media offering compatibility and ease of integration with various nanophotonic devices[18]. The strong Coulomb interactions give rise to very robust 2D trions (charged excitons) in TMDCs. The large oscillator strength of trions enables formation of well-resolved trion-polariton resonances[24] at relatively small electron density[21,25], which, as we show here, leads to a pronounced phase space filling effect enabling nonlinearity of one to two orders of magnitude bigger (depending on exciton–photon detuning) than that of neutral exciton–polaritons in TMDC platform. Our work opens a new highly nonlinear system for quantum optics applications enabling in principle scalability and control through nano-engineering of van der Waals heterostructures

Methods

Results

Conclusion