Breaking of Josephson junction oscillations and onset of quantum turbulence in Bose--Einstein condensates

TL;DR

This paper investigates how quantum turbulence develops in a 2D Bose-Einstein condensate with a Josephson junction, revealing how different turbulent regimes form and persist based on initial conditions and barrier parameters.

Contribution

It introduces a detailed analysis of turbulence formation and vortex dynamics in BECs with Josephson junctions, highlighting mechanisms for regime mixing and long-term turbulence evolution.

Findings

High initial density imbalance induces turbulence.

Vortex dipole transmission through the barrier causes regime mixing.

Optimal conditions extend turbulence duration.

Abstract

We analyse the formation and the dynamics of quantum turbulence in a two-dimensional Bose-Einstein condensate with a Josephson junction barrier modelled using the Gross-Pitaevskii equation. We show that a sufficiently high initial superfluid density imbalance leads to randomisation of the dynamics and generation of turbulence, namely, the formation of a quasi-1D dispersive shock consisting of a train of grey solitons that eventually breakup into chains of distinct quantised vortices of alternating vorticity followed by random turbulent flow. The Josephson junction barrier allows us to create two turbulent regimes: acoustic turbulence on one side and vortex turbulence on the other. Throughout the dynamics, a key mechanism for mixing these two regimes is the transmission of vortex dipoles through the barrier: we analyse this scattering process in terms of the barrier parameters, sound emission and vortex annihilation. Finally, we discuss how the vortex turbulence evolves for long times, presenting the optimal configurations for the density imbalance and barrier height in order to create the desired turbulent regimes which last as long as possible.