Hydrodynamic solitons in polariton superfluids

TLDR

Quantum fluids passing an obstacle behave differently from classical fluids, exhibiting superfluidity with no waves or whirlpools at low speeds, while higher velocities are predicted to generate quantised vortices and straight solitons. The study reports observing the transition from superfluidity to quantum turbulence and solitons in exciton‑polariton flow past a defect in a semiconductor microcavity. This observation was enabled by precise control of the polariton fluid’s velocity and density in the microcavity, allowing detailed investigation of the hydrodynamic effects.

Abstract

A quantum fluid passing an obstacle behaves very differently from a classical one. When the flow is slow enough, there are no waves and whirlpools formed around the obstacle, due to the spectacular phenomenon of superfluidity. For higher flow velocities, it has been predicted that the currents created by the obstacle give rise to a turbulent emission of quantised vortices and to the formation of solitons, straight solitary waves. Here we report the observation of a rich variety of quantum hydrodynamic effects and of the transition from superfluidity to quantum turbulence and to solitons in a flow of exciton-polaritons on the wake of a defect in a semiconductor microcavity. This has been possible thanks to the remarkable control of the fluid velocity and density of the polariton system.