  Chiral interaction between light and two-dimensional transition metal
dichalcogenides (2D-TMDs) has recently drawn enormous scientific attention. The
optical selection rules of these atomically thin semiconductors allow the
attribution of a pseudospin to the TMDs' valleys, which can be coherently
manipulated for information processing using polarized light. The interaction
of TMDs with circularly and linearly polarized light creates the valley
polarization and coherence, respectively. With a full Stokes polarization
analysis of light emitted from WS2 monolayer flakes, we conclusively confirm
the existence of coherence between its valleys. We observe spatial
heterogeneity in photoluminescence intensity, valley polarization and valley
coherence. The discovery of an inverse proportional relationship between
photoluminescence intensity and both valley polarization and coherence, reveals
a correlation between the (non-)radiative decay rate and the valley hopping.
The temperature dependence confirms the phononic nature of valley
depolarization and decoherence, that may be caused by strain and the presence
of defects.
