Nonlinear stage of modulational instability in repulsive two-component Bose-Einstein condensates

TL;DR

This paper investigates the nonlinear evolution of modulational instability in repulsive two-component Bose-Einstein condensates, combining experimental, analytical, and numerical methods to explore dispersive shock waves and rogue wave formation.

Contribution

It provides the first experimental analysis of MI in repulsive two-component BECs and generalizes the analytical description of dispersive shock wave expansion to various interaction regimes.

Findings

Excellent agreement between experiment, analytical, and numerical models.

Observation of Peregrine solitons from counterpropagating dispersive shock waves.

Versatility of atomic systems for studying nonlinear wave phenomena.

Abstract

Modulational instability (MI) is a fundamental phenomenon in the study of nonlinear dynamics, spanning diverse areas such as shallow water waves, optics, and ultracold atomic gases. In particular, the nonlinear stage of MI has recently been a topic of intense exploration, and has been shown to manifest, in many cases, in the generation of dispersive shock waves (DSWs). In this work, we experimentally probe the MI dynamics in an immiscible two-component ultracold atomic gas with exclusively repulsive interactions, catalyzed by a hard-wall-like boundary produced by a repulsive optical barrier. We analytically describe the expansion rate of the DSWs in this system, generalized to arbitrary inter-component interaction strengths and species ratios. We observe excellent agreement among the analytical results, an effective 1D numerical model, full 3D numerical simulations, and experimental data. Additionally, we extend this scenario to the interaction between two counterpropagating DSWs, which leads to the production of Peregrine soliton structures. These results further demonstrate the versatility of atomic platforms towards the controlled realization of DSWs and rogue waves.