ABCs of strong exciton–plasmon coupling in 2D TMDCs*

We present experimental details of strong exciton–plasmon coupling in 2D MoS₂ at the A-, B-, and C-excitons at room temperature. In one experiment, we show plasmon-mediated coherent hybridization of the A- and B-excitons. Rabi splitting of ~70 meV in k-space at each exciton is also shown. The observation of coherent coupling between different exciton energy levels in a valley-polarized material suggests the possibility of valleytronic quantum information transport and/or spin entanglement.

In another experiment we show giant Rabi splitting of 244 meV at the C-exciton, in k-space. This corresponds to 9.5 % of the transition energy and approaches the ultrastrong coupling regime. We discuss the role the TMDC band structure plays in this large coupling and unique features of the C-exciton.

The band modification that materials experience under strong coupling can be useful for modifying chemical reaction pathways and rates. We discuss experimental design considerations and show results of strong coupling in aqueous electrolyte.

The experimental work is backed up by electromagnetic transfer matrix and coupled oscillator models.