Townes soliton and beyond: Non-miscible Bose mixtures in 2D

TL;DR

This paper explores the formation and stability of Townes solitons in two-dimensional Bose mixtures near demixing, analyzing the transition to droplet states using coupled Gross-Pitaevskii equations and microscopic bath interactions.

Contribution

It introduces a detailed analysis of Townes solitons in 2D Bose mixtures and examines the transition to droplet regimes with a combined macroscopic and microscopic approach.

Findings

Townes solitons can form in 2D Bose mixtures under specific conditions.

Increasing minority atoms leads to a transition from soliton to droplet states.

Microscopic bath-mediated interactions influence soliton stability.

Abstract

In these lecture notes, we discuss the physics of a two-dimensional binary mixture of Bose gases at zero temperature, close to the point where the two fluids tend to demix. We are interested in the case where one of the two fluids (the bath) fills the whole space, while the other one (the minority component) contains a finite number of atoms. We discuss under which condition the minority component can form a stable, localized wave packet, which we relate to the celebrated "Townes soliton". We discuss the formation of this soliton and the transition towards a droplet regime that occurs when the number of atoms in the minority component is increased. Our investigation is based on a macroscopic approach based on coupled Gross-Pitaevskii equations, and it is complemented by a microscopic analysis in terms of bath-mediated interactions between the particles of the minority component.