Long-Range Transport of Organic Exciton-Polaritons Revealed by Ultrafast Microscopy

The excitations in organic materials are often described by Frenkel excitons, whose wave functions are tightly localized on the individual molecules, which results in short-range, nanoscale transport. However, under strong light-molecule coupling, new quantum states, known as cavity polaritons, are formed and the wave functions describing the coupled system extend over distances much larger than the molecular scale. Using time-resolved microscopy we directly show that this fundamental modification in the nature of the system induces long-range transport in organic materials and propagation over several microns. By following the motion of polaritons in real-time, we measure the propagation velocity of polaritons and we find that it is surprisingly lower than expected. Our approach sheds new light on the fundamental characteristics of polaritons and can provide critical information for the design of future organic-electronic devices, which will harness the polaritonic properties to overcome the poor conductance of organic materials.