Topological Polaritons

TL;DR

This paper introduces topolaritons, a new class of topological states formed by mixing photons and excitons, resulting in non-trivial polaritonic bands with chiral edge modes, enabled by momentum-space winding of exciton-photon coupling.

Contribution

It demonstrates the theoretical possibility of topological polaritons arising from exciton-photon coupling with a winding phase, and proposes practical realization methods.

Findings

Topolaritons exhibit chiral edge modes enabling unidirectional propagation.

The winding phase in exciton-photon coupling is linked to spin-orbit interaction and Zeeman field.

Practical schemes are proposed for creating topolaritons in semiconductors.

Abstract

The interaction between light and matter can give rise to novel topological states. This principle was recently exemplified in Floquet topological insulators, where \emph{classical} light was used to induce a topological electronic band structure. Here, in contrast, we show that mixing \emph{single} photons with excitons can result in new topological polaritonic states --- or "topolaritons". Taken separately, the underlying photons and excitons are topologically trivial. Combined appropriately, however, they give rise to non-trivial polaritonic bands with chiral edge modes allowing for unidirectional polariton propagation. The main ingredient in our construction is an exciton-photon coupling with a phase that winds in momentum space. We demonstrate how this winding emerges from spin-orbit coupling in the electronic system and an applied Zeeman field. We discuss the requirements for obtaining a sizable topological gap in the polariton spectrum, and propose practical ways to realize topolaritons in semiconductor quantum wells and monolayer transition metal dichalcogenides.