Macroscopic Two-Dimensional Polariton Condensates

TL;DR

This paper reports the creation of a large, trap-free two-dimensional polariton condensate formed by ballistic flow, with reduced phase noise and the first observation of the backflow effect in a fast-expanding wave packet.

Contribution

It introduces a record-size, trap-free polariton condensate formed outside the excitation region and demonstrates the first observation of the backflow effect in such a system.

Findings

Record-size 2D polariton condensate formed outside excitation area

Reduced phase noise due to low density (< 1 polariton/μm^2)

First experimental observation of backflow effect in polariton wave packet

Abstract

We report a record-size, two-dimensional polariton condensate of a fraction of a millimeter radius free from the presence of an exciton reservoir. This macroscopically occupied state is formed by the ballistically expanding polariton flow that relaxes and condenses over a large area outside of the excitation spot. The density of this trap-free condensate is < 1 polariton/{\mu}m^2, reducing the phase noise induced by the interaction energy. Moreover, the backflow effect, recently predicted for the nonparabolic polariton dispersion, is observed here for the first time in the fast-expanding wave packet.