title: Thermalization and cooling of plasmon-exciton polaritons: towards quantum condensation.
abstract: We present indications of thermalization and cooling of quasiparticles, a precursor for quantum condensation, in a plasmonic nanoparticle array. We investigate a periodic array of metallic nanorods covered by a polymer layer doped with an organic dye at room temperature. Surface lattice resonances of the array--hybridized plasmonic-photonic modes--couple strongly to excitons in the dye, and bosonic quasiparticles which we call plasmon-exciton polaritons (PEPs) are formed. By increasing the PEP density through optical pumping, we observe thermalization and cooling of the strongly coupled PEP band in the light emission dispersion diagram. For increased pumping, we observe saturation of the strong coupling and emission in a new weakly coupled band, which again shows signatures of thermalization and cooling.
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, c/o Philips Research Laboratories, High Tech Campus 4, 5656 AE Eindhoven, The Netherlands.
authors.forename: S R K
authors.initials: SR
authors.lastname: Rodriguez
authors.forename: J
authors.initials: J
authors.lastname: Feist
authors.forename: M A
authors.initials: MA
authors.lastname: Verschuuren
authors.forename: F J
authors.initials: FJ
authors.lastname: Garcia Vidal
authors.forename: J
authors.initials: J
authors.lastname: Gómez Rivas