Dynamical Phase Diagram of Ultracold Josephson Junctions

TL;DR

This paper maps the dynamical regimes of ultracold superfluid Josephson junctions, revealing transitions from Josephson oscillations to dissipative or self-trapped states as system parameters vary, with implications for experimental observation.

Contribution

It provides the first detailed phase diagram of dynamical regimes in 3D ultracold Josephson junctions, including the crossover between dissipative and self-trapped states beyond the two-mode model.

Findings

Transition from Josephson oscillations to dissipative or self-trapped regimes with increasing chemical potential difference.

Identification of a crossover between dissipative and self-trapped regimes.

Connection of vortex rings and acoustic emission to different superfluid dynamical regimes.

Abstract

We provide a complete study of the phase diagram characterising the distinct dynamical regimes emerging in a three-dimensional Josephson junction in an ultracold quantum gas. Considering trapped ultracold superfluids separated into two reservoirs by a barrier of variable height and width, we analyse the population imbalance dynamics following a variable initial population mismatch. We demonstrate that as the chemical potential difference is increased, the system transitions from Josephson plasma oscillations to either a dissipative (in the limit of low and narrow barriers) or a self-trapped regime (for large and wider barriers), with a crossover between the dissipative and the self-trapping regimes which we explore and characterize for the first time. This work, which extends beyond the validity of the standard two-mode model, connects the role of the barrier width, vortex rings and associated acoustic emission with different regimes of the superfluid dynamics across the junction, establishing a framework for its experimental observation, which is found to be within current experimental reach.