Dynamics of a vortex lattice in an expanding polariton quantum fluid

TL;DR

This study experimentally investigates the behavior of a vortex lattice in a non-equilibrium polariton quantum fluid, revealing dynamics and deviations from classical vortex relations due to interactions and density gradients.

Contribution

First experimental observation of vortex lattice dynamics and Feynman-Onsager relation deviations in an expanding polariton quantum fluid.

Findings

Vortex lattice stretches and bends outward due to interactions.

Detected small deviation from Feynman-Onsager rule caused by density gradient.

Tracked vortex core positions on picosecond timescales.

Abstract

If a quantum fluid is driven with enough angular momentum, at equilibrium the ground state of the system is given by a lattice of quantised vortices whose density is prescribed by the quantization of circulation. We report on the first experimental study of the Feynman-Onsager relation in a non-equilibrium polariton fluid, free to expand and rotate. Upon initially imprinting a lattice of vortices in the quantum fluid, we track the vortex core positions on picosecond time scales. We observe an accelerated stretching of the lattice and an outward bending of the linear trajectories of the vortices, due to the repulsive polariton interactions. Access to the full density and phase fields allows us to detect a small deviation from the Feynman-Onsager rule in terms of a transverse velocity component, due to the density gradient of the fluid envelope acting on the vortex lattice.