Theoretical description of atomtronic Josephson junctions in an optical lattice

TL;DR

This paper provides a theoretical framework for understanding atomtronic Josephson junctions in optical lattices, highlighting how strong-coupling Mott physics influences superfluid behavior and vortex formation in rotating systems.

Contribution

It introduces a finite temperature strong-coupling expansion approach to analyze Bose superfluids with barriers in optical lattices, incorporating Mott physics effects.

Findings

Superfluid circulation and phase slips depend on rotation speed.

Vortex formation occurs beyond a critical superfluid velocity.

Mott regions significantly alter superfluid flow patterns.

Abstract

Experimental realizations of ``atomtronic" Josephson junctions have recently been created in annular traps in relative rotation with respect to potential barriers that generate the weak links. If these devices are additionally subjected to an optical lattice potential, then they can incorporate strong-coupling Mott physics within the design, which can modify the behavior and can allow for interesting new configurations of barriers and of superfluid flow patterns. We examine theoretically the behavior of a Bose superfluid in an optical lattice in the presence of an annular trap and a barrier across the annular region which acts as a Josephson junction. As the superfluid is rotated, circulating super-currents appear. Beyond a threshold superfluid velocity, phase slips develop, which generate vortices. We use a finite temperature strong-coupling expansion about the mean-field solution of the Bose Hubbard model to calculate various properties of such devices. In addition, we discuss some of the rich behavior that can result when there are Mott regions within the system.