  Atomically thin semiconductors can be readily integrated into a wide range of
nanophotonic architectures for applications in quantum photonics and novel
optoelectronic devices. We report the observation of nonlocal interactions of
\textit{free} trions in pristine hBN/MoS$_2$/hBN heterostructures coupled to
single mode (Q $>10^4$) quasi 0D nanocavities. The high excitonic and photonic
quality of the interaction system stems from our integrated nanofabrication
approach simultaneously with the hBN encapsulation and the maximized local
cavity field amplitude within the MoS$_2$ monolayer. We observe a nonmonotonic
temperature dependence of the cavity-trion interaction strength, consistent
with the nonlocal light-matter interactions in which the extent of the
center-of-mass wavefunction is comparable to the cavity mode volume in space.
Our approach can be generalized to other optically active 2D materials, opening
the way towards harnessing novel light-matter interaction regimes for
applications in quantum photonics.
