Plasmon-Mediated Coherent Superposition of Discrete Excitons under Strong Exciton-Plasmon Coupling in Few-Layer MoS2 at Room Temperature

We demonstrate room temperature coherent hybridization of the A- and B-excitons in few-layer MoS2, mediated by simultaneous strong coupling to surface plasmon polaritons. Few-layer MoS2 was placed on a tunable plasmonic structure and the system's dispersion was measured by tuning the plasmon energy across the exciton energies. Strong coupling was observed as double Rabi splitting at the A- and B-excitons of 81 and 93 meV, respectively. A coupled harmonic oscillator model sheds light on the nature of the interaction, revealing a quantum superposition of the A- and B-excitons, mediated by the plasmon interaction. This observation suggests the possibility of room temperature intra- or intervalley quantum information transport and/or spin entanglement. The experiment confirms a previous theoretical prediction of room temperature exciton-exciton hybridization in two-dimensional MoS2. Further, through modeling we find that room temperature strong coupling is a general phenomenon among two-dimensional transition metal dichalcogenide exciton-plasmon systems.