Nonlinear Response of Trion-Polaritons in Two-Dimensional Materials*

The emergence of strongly bound composite particles of electrons (e) and holes (h) in 2D materials gives rise to many remarkable optical properties. In particular, the strong interactions between these composite particles are essential for the material’s nonlinear optical response. In contrast to excitons (e-h), trions (e-e-h) have more extended wavefunction, potentially leading to the increased interaction between these quasiparticles. When coupled to light in a microcavity, trions hybridize with cavity photons and form polaritonic states. The trion-trion scattering thus promotes strong effective nonlinearity for photons and facilitates nonlinear optical effects at the few-photon level. To investigate these effects, we calculate trion wavefunctions by solving the 3-body Wannier equation using a rich Gaussian-type basis. With this solution, we examine the effects of the direct and exchange scattering processes on the nonlinear response of trion-polaritons in the microcavity. The developed theory represents the first study of trion nonlinearity due to Coulomb processes and is directly applicable for describing the trion-polaritons in monolayers of transition metal dichalcogenides.