Room-temperature quantum fluids of light
Light-matter interaction is at the heart of most optical processes we are familiar with such as absorption, emission and scattering. These are normally treated by assuming that the incident light does not significantly modify the underlying electronic states of the material it interacts with. The strong coupling regime consists of the extreme case where light-matter interaction is so strong that it must be treated non-pertubatively. Polaritons, the resulting mixed light-matter particles, can be the source of many unique phenomena. We will describe how these quasiparticles can be exploited to enhance the photoluminescence yield of molecular emitters, engineer solar cells and photodetectors, modify photochemistry, and create room-temperature analogs to Bose-Einstein condensates1,2 and superfluid He.3
We will first focus on our work which uses organic microcavities that allow for room-temperature operation and then describe recent experiments using atomic monolayers of WS2 as the active medium, which allow for ballistic polariton flow over macroscopic >100 mm distances and the first room-temperature measurements of exciton-exciton interactions in 2D semiconductors. We will conclude with an outlook on the various material sets for room-temperature polaritonics and requirements for practical applications.
 Kéna-Cohen S., Forrest S.R., “Room-temperature polariton lasing in an organic single-crystal microcavity”, Nature Photonics, Vol. 4, (2010), p. 371.
 Daskalakis K.D., Maier S.A., Murray R., Kéna-Cohen S. “Nonlinear interactions in an organic polariton condensate”, Nature Materials, Vol. 13, (2014), p. 271.
 Lerario et al., “Room-temperature superfluidity in a polariton condensate”, Nature Physics, Vol 13, 837 (2017)