Dear Friends, On Thursday, March 21st, there will be an ITAMP topical lunch discussion. Tea Room (P-226) @ CfA (60 Garden Street) Time: 12:00-1:30 As always pizza will be served. Speaker: Johannes Feist (Universidad Autónoma de Madrid) Title: Signatures of quantum condensation in a diffractive array of plasmonic nanoparticles Abstract: Condensation of bosons, where a single quantum state is macroscopically populated, is a fascinating phenomenon spanning diverse areas of physics. It lies at the heart of superfluidity and superconductivity, as well as the Bose-Einstein condensation of ultracold dilute atoms, which was achieved close to twenty years ago. An important goal is to find systems in which condensation takes place at higher temperatures, even at or above room temperature. Bosonic quasi-particles in solids are excellent candidates due to their light effective masses, and signatures of condensation have been observed for semiconductor excitons and exciton-polaritons at temperatures of a few K, as well as for magnons and cavity photons at room temperature. I will present and discuss experimental signatures of quantum condensation of plexcitons at room temperature. Plexcitons are bosonic quasiparticles formed by strong coupling between organic molecule excitons and surface plasmon polaritons (quasi-bound modes confined on a subwavelength scale at metal-dielectric interfaces). The system I will discuss consists of a periodic array of metallic nanorods covered by a polymer layer doped with an organic dye. By increasing the plexciton density through optical pumping, we observe signatures of thermalization and condensation, such as the emergence of Bogoliubov-Goldstone modes, despite the nonequilibrium character of this driven and dissipative system. Looking forward to seeing you there, Charles Mathy