Dense soliton complexes in a two-component Bose-Einstein condensate

Many natural phenomena are understood at a fundamental level but exhibit complex dynamics which require statistical methods of analysis in practice. The dynamics of nonlinear waves in integrable systems has arisen as a potentially revelatory framework for understanding the emergence of complexity in this context. Of interest here, collections of localized nonlinear waves known as solitons, while being mathematically understood individually, can exhibit sufficiently random dynamics to be better described as a kind of soliton gas.

In this work we demonstrate the experimental realization of dense soliton complexes in a quasi-one-dimensional Bose-Einstein condensate. We employ a Rabi winding technique to controllably initialize a regular array of phase jumps in a two-component atomic superfluid. Depending on the density of phase windings we observe different collective behavior, and for the densest arrays we observe signatures of soliton collisions and randomization which persist over long timescales. This work leverages some of the unique advantages of ultracold atom systems to provide a dual experimental and numerical platform for studies of soliton gases and other nonlinear hydrodynamic phenomena.