Andrew Musser

Polaritons are increasingly touted as a promising tool to ‘rewrite’ the functional behavior of molecular systems. Polaritons are mixed states formed from the hybridization of molecular transition dipoles with a confined electromagnetic field. Originally the purview of ultra-cold physics, when this concept is applied to molecular vibrational or electronic absorption transitions polaritons can be attained at room temperature. Studies over the last decade have revealed a host of weird and wonderful effects that result, from enhanced energy transport and charge carrier mobility to changes in the selectivity of chemical reactions – all by simply enclosing the materials between a pair of mirrors. Yet, while the field has become better and better at identifying exciting polaritonic phenomena, we lack a fundamental understanding of their underlying mechanisms. The temptation is strong to explain their exotic behavior in terms of the bright, strongly coupled states that we can easily observe. However, the bright polariton states are not alone. When we peer into optical cavities with ultrafast spectroscopy, we see that they are accompanied by a host of dark states that can dominate the photophysical response. Work in the Musser lab focuses on these dark states that no one wants to talk about. They introduce undeniable complexity into the framework of polaritonics, but offer new opportunities for functional control.