Observation of Dirac cones and room temperature polariton lasing in an organic honeycomb lattice

Artificial one- and two-dimensional lattices have emerged as a powerful platform for the emulation of lattice Hamiltonians, the fundamental study of collective many-body effects as well as phenomena arising from non-trivial topology. Exciton-polaritons, bosonic part-light and part-matter quasiparticles, combine pronounced nonlinearities with the possibility of on-chip implementation. In this context, organic semiconductors, hosting ultra-stable Frenkel excitons, embedded in a microcavity have proven to be versatile contenders for the study of nonlinear many-body physics and bosonic condensation, which also enable deployment at ambient conditions. Here, we implement a well-controlled, high-quality optical lattice, hosting light-matter quasi-particles. The realized polariton graphene presents with excellent cavity quality factors, showing distinct signatures of Dirac cone and flatband dispersions as well as polariton lasing at room temperature. This is realized by filling coupled dielectric microcavities with the fluorescent protein mCherry. We demonstrate the emergence of a coherent polariton condensate at ambient conditions, profiting from coupling conditions as precise and controllable as in state-of-the-art inorganic semiconductor-based systems, without limitations due to e.g. lattice matching in epitaxial growth. This progress allows straightforward extension to more complex systems, such as the study of topological phenomena in two-dimensional lattices including topological lasers and non-Hermitian optics.