Directional Goldstone waves in polariton condensates close to equilibrium
Abstract
Quantum fluids of light are realized in semiconductor microcavities by 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 show that excitations are created with a definite direction with respect to the condensate, analogous to how a sea breeze develops surface waves aligned with the wind. These results reveal the effect of asymmetric pumping on the collective excitations of a condensate. Furthermore, we measure the critical sound speed for polariton superfluids close to equilibrium.
Keywords
Cite
@article{arxiv.1905.12551,
title = {Directional Goldstone waves in polariton condensates close to equilibrium},
author = {Dario Ballarini and Davide Caputo and Galbadrakh Dagvadorj and Richard Juggins and Milena De Giorgi and Lorenzo Dominici and Kenneth West and Loren N. Pfeiffer and Giuseppe Gigli and Marzena H. Szymanska and Daniele Sanvitto},
journal= {arXiv preprint arXiv:1905.12551},
year = {2020}
}