Feynman, vortices and resistance in atomtronic circuits

Abstract

In a 1955 paper on liquid helium Richard Feynman suggested that a superfluid flowing at sufficient speed through a channel into an infinite reservoir would produce uniformly spaced vortex pairs from the corners of the channel mouth. He argued that the critical velocity which separates the regime of vortex production from the dissipation-free regime is given by v_c=hbar/(md)*ln(d/a), where d is the width of the channel and a is on the order of the interparticle spacing. We numerically investigate this conjecture by simulating the fluid dynamics of a 87Rb BEC in a quasi-2D optical trap. We then explore the applicability of this conjecture to a more experimentally realisable "dumbbell" potential, with possible applications in the emerging field of atomtronics.