Organic Room-Temperature Polariton Condensate in a Higher-Order Topological Lattice.

Organic molecule exciton-polaritons in photonic lattices are a versatile platform to emulate unconventional phases of matter at ambient temperatures, including protected interface modes in topological insulators. Here, we investigate bosonic condensation in the most prototypical higher-order topological lattice: a 2D-version of the Su-Schrieffer-Heeger model. Under strong optical pumping, we observe bosonic condensation into both 0D and 1D topologically protected modes. The resulting 1D macroscopic quantum state reaches a coherent spatial extent of 10 μm, as evidenced by interferometric measurements of first order coherence. We account for the spatial mode patterns resulting from fluorescent protein-filled, structured microcavities by tight-binding calculations and theoretically characterize the topological invariants of the lattice. Our findings pave the way toward organic on-chip polaritonics using higher-order topology as a tool for the generation of robustly confined polaritonic lasing states.