Superfluid current disruption in a chain of weakly coupled Bose-Einstein Condensates

TL;DR

This paper experimentally investigates how superfluid atomic currents in a chain of weakly linked Bose-Einstein condensates break down, transitioning from coherent flow to localized insulator states under certain conditions.

Contribution

It provides the first experimental observation of superfluid current disruption in a Bose-Einstein condensate array with detailed analysis of the transition conditions.

Findings

Superfluid current breaks down at a critical velocity.

Transition from coherent oscillation to localization observed.

Critical velocity depends on tunneling rate.

Abstract

We report the experimental observation of the disruption of the superfluid atomic current flowing through an array of weakly linked Bose-Einstein condensates. The condensates are trapped in an optical lattice superimposed on a harmonic magnetic potential. The dynamical response of the system to a change of the magnetic potential minimum along the optical lattice axis goes from a coherent oscillation (superfluid regime) to a localization of the condensates in the harmonic trap ("classical" insulator regime). The localization occurs when the initial displacement is larger than a critical value or, equivalently, when the velocity of the wavepacket's center of mass is larger than a critical velocity dependent on the tunnelling rate between adjacent sites.