Highly nonlinear trion-polaritons in a monolayer semiconductor

TL;DR

This paper demonstrates extremely large Kerr-like nonlinearities in trion-polaritons within monolayer TMDCs, surpassing other materials and systems, with potential applications in quantum optics and scalable quantum devices.

Contribution

It introduces a new highly nonlinear system using trion-polaritons in monolayer TMDCs, significantly exceeding previous nonlinearities and enabling scalable quantum optical applications.

Findings

Trion-polaritons exhibit energy shifts at very low photon fluxes.

Nonlinearity is 10 to 1000 times larger than in other polariton systems.

Kerr nonlinearity exceeds that of bare TMDCs and common optical materials.

Abstract

Highly nonlinear optical materials with strong effective photon-photon interactions (Kerr-like nonlinearity) are required in the development of novel quantum sources of light as well as for ultrafast and quantum optical signal processing circuitry. Here we report very large Kerr-like nonlinearities by employing strong optical transitions of charged excitons (trions) observed in semiconducting transition metal dichalcogenides (TMDCs). By hybridising trions in monolayer MoSe$_2$ at low electron densities with a microcavity mode, we realise trion-polaritons exhibiting significant energy shifts at very small photon fluxes due to phase space filling. Most notably, the strong trion-polariton nonlinearity is found to be 10 to 1000 larger than in other polariton systems, including neutral exciton-polaritons in TMDCs. Furthermore it exceeds by factors of $\sim 10^3-10^5$ the magnitude of Kerr nonlinearity in bare TMDCs, graphene and other widely used optical materials (e.g. Si, AlGaAs etc) in weak light-matter coupling regimes. The results are in good agreement with a theory which accounts for the composite nature of excitons and trions and deviation of their statistics from that of ideal bosons and fermions. This 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.