Directional Goldstone waves in polariton condensates close to equilibrium

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 conde...

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Bibliographic Details
Published in:Nature communications 2020-01, Vol.11 (1), p.217-217, Article 217
Main Authors: Ballarini, Dario, Caputo, Davide, Dagvadorj, Galbadrakh, Juggins, Richard, Giorgi, Milena De, Dominici, Lorenzo, West, Kenneth, Pfeiffer, Loren N., Gigli, Giuseppe, Szymańska, Marzena H., Sanvitto, Daniele
Format: Article
Language:English
Subjects:
639/766/119/999
639/766/400/2797
Asymmetry
Condensates
Excitation spectra
Excitons
Humanities and Social Sciences
Microcavities
multidisciplinary
Polaritons
Science
Science (multidisciplinary)
Sound
Superfluidity
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Summary: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. Polariton condensates undergo continuous driving and dissipation, posing challenges for investigating their collective behaviour. Ballarini et al. adapt an oceanographic technique to measure the asymmetric occupation of the Goldstone mode and identify similarities with equilibrium condensates.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-019-13733-x