Quantifying scattering rates in the electronic strong light-matter coupling regime

Stéphane Kená-Cohen Polytechnique Montreal Technological University

One of the most interesting features of exciton-polaritons is their ability to condense into a single macroscopic quantum state: a so-called polariton Bose-Einstein condensate. Under non-equilibrium conditions, the density at which condensation occurs is intrinsically linked to the ratio between the scattering rate from localized “dark” molecular excitations to the polariton lifetime. While a variety of theoretical approaches have been introduced to describe the former, there has yet to be a quantitative comparison of such rates with experiment. We will describe 3 different approaches that allow for direct measurements of these scattering rates. We will show that these rates are generally slow and radiative in nature. This inefficacy is, to some extent, linked to the large N problem, and this intrinsically limits the impact that polaritons have on the kinetics of electronically excited molecule. We will discuss the consequences that this has had on previous attempts to modify photophysical processes using strong light-matter coupling and possible solutions.