Research Denise Ahmed-Braun

Abstract

Self-bound states in free space such as droplets can exist when attractive forces (collapsing the system) and repulsive forces (expanding the system) balance each other out. In ultracold atomic gases the stabilizing force can be provided by quantum fluctuations, the resulting object is called a quantum droplet. Moreover in quantum gases the interatomic interactions can be tuned experimentally. Nevertheless experimental realization of quantum droplets remains challenging due to their finite lifetime. In this project we will investigate the lifetime and dynamics of quantum droplets taking into account three-body losses as well as quantum evaporation, and calculate the stability phase diagram. To enhance the lifetime of quantum droplets we propose to strongly confine them to the quasi one-dimensional regime, where three-body losses are smaller. We investigate the properties in one dimension as well as the optimal cross-over protocol from 3D to 1D. Finally we will also investigate the fractionalization transition between a single large droplet and many small droplets, expected to occur at a critical temperature. This project will shed new light on the nature of quantum fluctuations and provide pathways for the experimental realization of long lived quantum droplets in one dimension.

Researcher(s)

• Promoter: Tempere Jacques
• Co-promoter: Ahmed-Braun Denise
• Fellow: Van Loock Jeroen

Research team(s)

• Theory of quantum systems and complex systems

Project type(s)

• Research Project

Abstract

The three-body problem is notoriously hard to solve, as explained to a general audiance in Liu Cixin's novels. In condensed matter physics, this problem is exacerbated by the fact that the interaction energy of a three-particle system cannot be decomposed in a sum of pairwise interactions. The part that cannot be reduced is called the three-body interaction, and is typically neglected. However, in extreme cases, the three-body interactions can become dominant over pairwise terms. In ultracold atomic gases, these interactions can stabilize superfluid droplets, which would otherwise collapse. So far, these droplets have remained elusive, but the overall goal of this project is to calculate conditions under which they could be observed, and to work together with experimentalists to finally create this system so crucial to our understanding of three-body physics. Doing so requires a unique combination of expertise in many-body physics and few-body physics, that is realized by combining my skills in three-body coupled channel calculations with my host's expertise in many-body physics. We will go beyond deriving the formation criteria for these droplets, and also propose a way to characterize their properties by using an impurity as a probe in a variety of media and mixtures of quantum fluids. The theoretical analysis and creation of the three-body interaction stabilized droplets will have an important impact on the understanding of a broad class of quantum many-body systems.

Researcher(s)

• Promoter: Tempere Jacques
• Fellow: Ahmed-Braun Denise

Research team(s)

• Theory of quantum systems and complex systems

Project type(s)

• Research Project