The Fate of the Upper Polariton: Breakdown of the Quasiparticle Picture in the Continuum

Abstract

Organic polaritons resulting from the strong hybridisation between photons and matter excitations have arisen as a suitable platform to device light-matter technological interfaces at room temperature. Despite their inherent complexity, organic polaritons are commonly regarded as coherent light-matter excitations that can be described in terms of Landau's quasiparticle approach. Here, we experimentally unveil the role of incoherent matter excitations on the polaritons by exploring the relevant energy-momentum parameter space. We demonstrate the emergence of a well-defined lower polariton branch and an intriguing fading of the upper polariton at its entrance to a continuum of matter excitations. This marks the breakdown of the simplistic quasiparticle picture for this branch and the formation of a more complex quantum state. Our experimental results are sustained by a general theoretical framework that allows understanding the light-matter hybridisation beyond the quasiparticle approach. Our work expands the understanding of organic polaritons in all their complexity and increases their technological significance.

4+4 pages, 3 +1 figures

References in corpus (6)

• Quantum fluids of light
• Disorder-induced enhancement of transport through graphene p-n junctions
• Polaritonic Feshbach Resonance
• A theoretical perspective on molecular polaritonics
• Observation of electrically tunable Feshbach resonances in twisted bilayer semiconductors
• Organic charged polaritons in the ultrastrong coupling regime

Cited by in corpus (4)

• Intercavity polariton slows down dynamics in strongly coupled cavities
• Polaronic polariton quasiparticles in a dark excitonic medium
• Resolving exciton and polariton multi-particle correlations in an optical microcavity in the strong coupling regime
• Topological Frenkel Exciton-Polaritons in One-Dimensional Lattices of Strongly Coupled Cavities