Self-trapping of Bose-Einstein condensates expanding into shallow optical lattices

TL;DR

This paper investigates the sudden breakdown of transport in a Bose-Einstein condensate expanding into a shallow optical lattice, revealing self-trapping phenomena and methods to control it.

Contribution

It introduces an analytical and numerical study of self-trapping in BECs within shallow lattices, including control strategies and finite-size effects.

Findings

Transport breakdown correlates with self-trapped states.

Applying a constant offset potential can prevent self-trapping.

Finite lattice width causes revival of expansion after breakdown.

Abstract

We observe a sudden breakdown of the transport of a strongly repulsive Bose-Einstein condensate through a shallow optical lattice of finite width. We are able to attribute this behavior to the development of a self-trapped state by using accurate numerical methods and an analytical description in terms of nonlinear Bloch waves. The dependence of the breakdown on the lattice depth and the interaction strength is investigated. We show that it is possible to prohibit the self-trapping by applying a constant offset potential to the lattice region. Furthermore, we observe the disappearance of the self-trapped state after a finite time as a result of the revived expansion of the condensate through the lattice. This revived expansion is due to the finite width of the lattice.