put a detection threshold below $100$ photon counts that cuts the signal above $\sim 2.03$ eV in panels (a), (c), (e) and (f). (d) Differential angle-resolved reflection spectrum obtained from analyzed TM and TE measurements. (f) $k_x$-energy dispersion of the degree of chiralitonic inter-valley coherence $m_{11}$ computed from (c) and (e). \[fig:4\]](Figure4.png){width="1\columnwidth"}

As a consequence of this motional narrowing effect, such a strongly coupled system involving atomically thin crystals of TMDs could then provide new ways to incorporate intervalley coherent dynamics [@Xu2013; @Li2016; @Urbaszek2016; @schmidt2016magnetic; @ye2017optical] into the realm of polariton physics. To illustrate this, we now show that two counter-propagating flows of chiralitons can evolve coherently. It is clear from Fig. \[fig:1\] (c) that within such a coherent superposition of counter-propagating chiralitons $$|\Psi> = |P^{\pm}_{K,\sigma^+,-k_{\textrm{\tiny SP}}}> + |P^{\pm}_{K',\sigma^-,+k_{\textrm{\tiny SP}}}>
 \label{eq:Psi}$$ flow directions and spin polarizations become non-separable. Intervalley coherence is expected to result in a non-zero degree of linearly polarized PL when excited by the same linear polarization. This can be monitored by measuring the $S_1=I_{\textrm{\tiny TM}}-I_{\textrm{\tiny TE}}$ coefficient of the PL Stokes vector, where $I_{\textrm{\tiny TM}(\textrm{\tiny TE})}$ is the emitted PL intensity analyzed in TM (TE) polarization. This coefficient is displayed in the $k_x$-energy plane in Fig. \[fig:4\](c) 