Bright soliton to quantum droplet transition in a mixture of Bose-Einstein condensates

TL;DR

This paper explores the transition between bright solitons and quantum droplets in attractive Bose-Einstein condensates, combining theoretical modeling and experimental measurements to understand their connection and coexistence.

Contribution

It introduces a simple theoretical model and experimental analysis to map the transition and coexistence region between solitons and droplets in a Bose-Bose mixture.

Findings

Solitons and droplets can be smoothly connected or coexist in a bi-stable region.

Experimental measurements of spin composition and density delineate the boundary between states.

Theoretical and experimental results agree on the conditions for state transition.

Abstract

Attractive Bose-Einstein condensates can host two types of macroscopic self-bound states of different nature: bright solitons and quantum liquid droplets. Here, we investigate the connection between them with a Bose-Bose mixture confined in an optical waveguide. We develop a simple theoretical model to show that, depending on atom number and interaction strength, solitons and droplets can be smoothly connected or remain distinct states coexisting only in a bi-stable region. We experimentally measure their spin composition, extract their density for a broad range of parameters and map out the boundary of the region separating solitons from droplets.