  A phonoriton is an elementary excitation that is predicted to emerge from
hybridization between exciton, phonon and photon. Besides the intriguing
many-particle structure, phonoritons are of interest as they could serve as
functional nodes in devices that utilize electronic, phononic and photonic
elements for energy conversion and thermal transport applications. Although
phonoritons are predicted to emerge in an excitonic medium under intense
electromagnetic wave irradiation, the stringent condition for their existence
has eluded direct observation in solids. In particular, on-resonance, intense
pumping scheme has been proposed but excessive photoexcitation of carriers
prevents optical detection. Here we theoretically predict the appearance of
phonoritonic features in monolayer hexagonal boron nitride (hBN) embedded in an
optical cavity. The coherent superposition nature of phonoriton states is
evidenced by the hybridization of exciton-polariton branches with phonon
replicas that is tunable by the cavity-matter coupling strength. This finding
simultaneously provides an experimental pathway to observe the predicted
phonoritons and opens a new avenue for tuning materials properties.
