Collisionally inhomogeneous Bose-Einstein condensates with a linear interaction gradient

TL;DR

This paper investigates the complex dynamics of a Bose-Einstein condensate with spatially varying interactions, revealing soliton formation, wave interference, and cascade phenomena, advancing understanding of nonlinear instabilities in quantum gases.

Contribution

It introduces a detailed study of collisionally inhomogeneous BECs with a linear interaction gradient, combining experiments and simulations to explore novel nonlinear wave behaviors.

Findings

Observation of soliton-like density peaks and their decay

Detection of counter-propagating self-interfering wave packets

Identification of cascades of solitons and collapse processes

Abstract

We study the evolution of a collisionally inhomogeneous matter wave in a spatial gradient of the interaction strength. Starting with a Bose-Einstein condensate with weak repulsive interactions in quasi-one-dimensional geometry, we monitor the evolution of a matter wave that simultaneously extends into spatial regions with attractive and repulsive interactions. We observe the formation and the decay of soliton-like density peaks, counter-propagating self-interfering wave packets, and the creation of cascades of solitons. The matter-wave dynamics is well reproduced in numerical simulations based on the nonpolynomial Schroedinger equation with three-body loss, allowing us to better understand the underlying behaviour based on a wavelet transformation. Our analysis provides new understanding of collapse processes for solitons, and opens interesting connections to other nonlinear instabilities.