Density engineering of an oscillating soliton/vortex ring in a Bose-Einstein condensate

TL;DR

This paper demonstrates the creation and observation of a stable, periodically oscillating pair of solitons and vortex rings in a Bose-Einstein condensate, revealing a rare, conserved oscillation phenomenon.

Contribution

It introduces a novel density engineering method to produce a single pair of solitons at low collisional energies and observes their stable, periodic evolution into vortex rings.

Findings

Successful creation of a single soliton pair using density engineering.

Observation of stable, periodic oscillations between solitons and vortex rings.

Contrast with previous experiments showing irreversible decay of solitons.

Abstract

When two Bose-Einstein condensates (BEC's) collide with high collisional energy, the celebrated matter wave interference pattern results. For lower collisional energies the repulsive interaction energy becomes significant, and the interference pattern evolves into an array of grey solitons. The lowest collisional energy, producing a single pair of solitons, has not been probed. We use density engineering on the healing length scale to produce such a pair of solitons. These solitons then evolve periodically between vortex rings and solitons, which we image in-situ on the healing length scale. The stable, periodic evolution is in sharp contrast to the behavior of previous experiments, in which the solitons decay irreversibly into vortex rings via the snake instability. The evolution can be understood in terms of conservation of mass and energy in a narrow condensate. The periodic oscillation between two qualitatively different forms seems to be a rare phenomenon in nature.