intervalley dynamics whose contribution can still be observed in the steady-state. We hence demonstrate the generation of coherent superpositions (i.e. pairs) of chiralitons flowing in opposite directions. These results, unexpected from the bare TMD monolayer RT properties [@Xu2013; @moody2016exciton; @Li2016], point towards the importance of the strong coupling regime where fast Rabi oscillations compete with TMD valley relaxation dynamics, as recently discussed [@Tartakovskii2016; @Chen2017; @Kleemann2017].

The small Bohr radii and reduced screening of monolayer TMD excitons provide the extremely large oscillator strength required for light matter interaction in the strong coupling regime, as already achieved in Fabry-Pérot cavities [@Menon2015; @Tartakovskii2015; @Imamoglu2016] and more recently in plasmonic resonators [@Agarwal2016; @ShaojunWS2]. In this context, Tungsten Disulfide (WS$_2$) naturally sets itself as a perfect material for RT strong coupling [@ShaojunWS2] due to its sharp and intense $A$-exciton absorption peak, well separated from the higher energy $B$-exciton line (see Fig. \[fig:1\](a)) [@Heinz2014]. Moreover, the inversion symmetry breaking of the crystalline order on a TMD monolayer, combined with time-reversal symmetry, leads to spin-polarized valley transitions at the $K$ and $K'$ points of the associated Brillouin zone, as sketched in Fig. \[fig:1\](b) [@reviewTMDs]. This polarization property makes therefore atomically thin TMD semiconductors very promising candidates with 