Transverse Josephson vortices and localized states in stacked Bose-Einstein condensates

TL;DR

This paper explores the behavior of transverse Josephson vortices and localized states in stacked Bose-Einstein condensates, revealing their stability, circulation properties, and potential for experimental realization and technological applications.

Contribution

It introduces the concept of transverse Josephson vortices with non-integer circulation and nonlinear standing-wave states in stacked BECs, expanding understanding of their dynamical stability and localization.

Findings

Transverse Bloch waves can carry stable superflows depending on quasimomentum.

Transverse Josephson vortices exhibit non-integer circulation in ring-shaped systems.

Superpositions of Bloch waves can produce localized standing-wave states.

Abstract

The stacks of Bose-Einstein condensates coupled by long Josephson junctions present a rich phenomenology feasible to experimental realization and specially suitable for technological applications as the nonlinear-optics and superconducting analogues have already proved. Among this, we show that transverse Bloch waves excited in arrays of one-dimensional coupled condensates can carry tunneling superflows whose dynamical stability depends on the quasimomentum. Across the stacks with periodic boundary conditions, forming closed ring-shaped systems, such Bloch states yield transverse Josephson vortices with a generic non-integer circulation in units of $h/m$. Additionally, the superpositions of degenerate linear Bloch waves can suppress the supercurrents and give rise to families of nonlinear standing-wave states with strong (transverse) spatial localization. Stable states of this type can also be found in finite size systems.