Dissipative shock waves generated by a quantum-mechanical piston

TL;DR

This study explores shock wave dynamics in a superfluid Bose-Einstein condensate, revealing dissipative-like behavior due to vortex turbulence, with experimental results aligning with classical shock theory predictions.

Contribution

It demonstrates that superfluid shock waves can exhibit dissipative dynamics through vortex decay, bridging quantum and classical fluid behaviors.

Findings

Formation of shock fronts and rarefaction waves observed

Dissipative-like dynamics explained by vortex turbulence

Quantitative agreement between experiments and simulations

Abstract

The piston shock problem is a prototypical example of strongly nonlinear fluid flow that enables the experimental exploration of fluid dynamics in extreme regimes. Here we investigate this problem for a nominally dissipationless, superfluid Bose-Einstein condensate and observe rich dynamics including the formation of a plateau region, a non-expanding shock front, and rarefaction waves. Many aspects of the observed dynamics follow predictions of classical dissipative---rather than superfluid dispersive---shock theory. The emergence of dissipative-like dynamics is attributed to the decay of large amplitude excitations at the shock front into turbulent vortex excitations which allow us to invoke an eddy viscosity hypothesis. Our experimental observations are accompanied by numerical simulations of the mean field, Gross-Pitaevskii equation that exhibit quantitative agreement with no fitting parameters. This work provides an avenue for the investigation of quantum shock waves and turbulence in channel geometries, which are currently the focus of intense research efforts.