Signatures of Quantum Condensation in a Plasmonic Nanoparticle Array
Said R.K. Rodríguez
Center for Nanophotonics, FOM Institute AMOLF, c/o Philips Research Laboratories, Eindhoven, The Netherlands
We present experimental signatures of quantum condensation in a plasmonic system. 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 quasi-particles known as plexcitons are formed. By increasing the plexciton density through optical pumping, we observe the emergence of Bogoliubov-Goldstone excitations on top of the strongly coupled plexciton band in the light emission dispersion diagram. The Bogoliubov-Goldstone mode shows signatures of thermalization and condensation, despite the nonequilibrium character of this driven and dissipative system.