Superfluid current disruption in a chain of weakly coupled Bose–Einstein condensates

Abstract

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. § To whom correspondence should be addressed (fsc@lens.unifi.it) Atomic Bose-Einstein condensates have been either loaded or produced in periodic potentials opening up the possibility to investigate new phenomena tuning the degree of coherence in the system. Experiments have explored regimes ranging from the coherent matter wave emission from a condensate loaded on a vertical standing wave [1], to the observation of number squeezed states [2], to the demonstration of a one-dimensional Josephson junctions array with a linear chain of condensates produced in an optical