  Strong-coupling of monolayer metal dichalcogenide semiconductors with light
offers encouraging prospects for realistic exciton devices at room temperature.
However, the nature of this coupling depends extremely sensitively on the
optical confinement and the orientation of electronic dipoles and fields. Here,
we show how plasmon strong coupling can be achieved in compact robust
easily-assembled gold nano-gap resonators at room temperature. We prove that
strong coupling is impossible with monolayers due to the large exciton
coherence size, but resolve clear anti-crossings for 8 layer devices with Rabi
splittings exceeding 135 meV. We show that such structures improve on prospects
for nonlinear exciton functionalities by at least 10^4, while retaining quantum
efficiencies above 50%.
