OMI Colloquium | Exciton-Polaritons in 2D Transition Metal Dichalcogenide Layers Placed in a Planar Microcavity, Oct. 19

The Ohio Materials Institute Colloquium Series presents Carlos Trallero of Centro Latino-Americano de Fisica,  on “Exciton-Polaritons in 2D Transition Metal Dichalcogenide Layers Placed in a Planar Microcavity”, on special date, time, and location: Friday, Oct. 19, at 10 a.m. in Edwards Accelerator Lab 208.

Carlos Trallero

Abstract: Exciton-polariton modes arising from interaction between bound excitons in monolayer thin semiconductor sheets and microcavity photons are considered theoretically for a Fabry-Perot planar microcavity. In our approach the excitonic resonances are considered as strictly two-dimensional (2D) and are taken into account through boundary conditions (discontinuity of appropriate components of the electromagnetic field). We calculated the dispersion curves, mode lifetimes, Rabi splitting, and Hopfield coefficients of these structures for two nearly 2D transition metal dichalcogenide (TMD) materials, MoS₂ and WS₂. Our results indicate that the strong coupling regime can be achieved in these materials, in accordance with recent experiments. Moreover, excitonic lasing has been demonstrated very recently for a structure of type (ii) incorporating a WS₂ monolayer [1].

We also suggest that such structures are interesting for studying the rich physics associated with the Bose-Einstein condensation of exciton polaritons The large exciton binding energy and dipole allowed exciton transitions, which are characteristic of the TMD materials, in addition to the relatively easily controllable distance between the semiconductor sheets, are the advantages of this system in comparison with traditional GaAs or CdTe based semiconductor microcavities. In particular, in order to mimic the rich physical properties of the quantum degenerate mixture of two bosonic species of dilute atomic gases with tunable interspecies interaction, we put forward a structure containing two semiconductor sheets separated by some atomic-scale distance (l) using a nearly 2D dielectric, which offers the possibility of tuning the interaction between two exciton-polariton Bose-Enstein condensates. We show that the dynamics of this structure are ruled by two coupled Gross-Pitaevskii equations with the coupling parameter∼ l⁻¹.