Quantum Model of Propagating Plexcitons in Two-Dimensional Semiconducting Materials*

Hybrid quantum states emerge upon the strong interaction of surface plasmon waves and excitonic species in 2D semiconducting materials. This gives rise to the so-called "plexcitons", which are a special class of polaritonic states that can attain quantum properties that are not possible in either of the decoupled states. In this work, we present a quantum model of the coupling between 2D mobile excitons and mobile surface plasmon polaritons, where both physical states are treated quantum mechanically. Our model shows the emergence of the propagating plexciton states, reflecting a strong coupling between the individual species. The application to a hypothetical device (composed of a gold surface, a spacer, the 2D material, and a capping dielectric) we propose also shows scenarios in which the lower polariton (plexciton) quasiparticle dominates the dynamics of the system upon the injection of surface plasmons to the system. We then discuss opportunities for future work, from both theoretical and experimental perspectives.