2019/05/29 by Dario Ballarini, Davide Caputo, Galbadrakh Dagvadorj +9 · 20 citations
Physics and Astronomy · #Dispersion (optics) #Excitation #Goldstone #Interference (communication) #Measure (data warehouse) #Mechanical and Optical Resonators #Polariton #Quantum Electrodynamics and Casimir Effect #Quantum fluid #Semiconductor #Strong Light-Matter Interactions #Superfluidity #cond-mat.quant-gas #physics.optics
paper · pdf · doi:10.1038/s41467-019-13733-x
published in Nature Communications 11(1), 217 (Nature Portfolio)
arxiv created 2019/05/29 · openalex created_date 2019/06/07 · openalex publication_date 2020/01/10 · arxiv updated 2020/02/05 · openalex updated_date 2026/08/06
Quantum fluids of light are realized in semiconductor microcavities using exciton-polaritons, solid-state quasi-particles with a light mass and sizeable interactions. Here, we use the microscopic analogue of oceanographic techniques to measure the excitation spectrum of a thermalised polariton condensate. Increasing the fluid density, we demonstrate the transition from a free-particle parabolic dispersion to a linear, sound-like Goldstone mode characteristic of superfluids at equilibrium. Notably, we reveal the effect of an asymmetric pumping by showing that collective excitations are created with a definite direction with respect to the condensate. Furthermore, we measure the critical sound speed for polariton superfluids close to equilibrium.