Anomalous buoyancy of quantum bubbles in immiscible Bose mixtures

TL;DR

This paper explores how quantum fluctuations alter the buoyancy and equilibrium positions of bubbles in immiscible Bose mixtures, leading to novel behaviors like intermediate positioning and transition into self-bound droplets.

Contribution

It introduces the concept of quantum bubbles in a three-component Bose mixture and analyzes how quantum fluctuations modify buoyancy and bubble stability.

Findings

Quantum fluctuations change the pressure balance of bubbles.

Quantum effects can position bubbles between center and surface.

Bubbles may transition into self-bound droplets at the surface.

Abstract

Buoyancy is a well-known effect in immiscible binary Bose-Einstein condensates. Depending on the differential confinement experienced by the two components, a bubble of one component sitting at the center of the other eventually floats to the surface, around which it spreads either totally or partially. We discuss how quantum fluctuations may significantly change the volume and position of immiscible bubbles. We consider the particular case of two miscible components, forming a pseudo-scalar bubble condensate with enhanced quantum fluctuations (quantum bubble), immersed in a bath provided by a third component, with which they are immiscible. We show that in such a peculiar effective binary mixture, quantum fluctuations change the equilibrium of pressures that define the bubble volume and modify as well the criterion for buoyancy. Once buoyancy sets in, in contrast to the mean-field case, quantum fluctuations may place the bubble at an intermediate position between the center and the surface. At the surface, the quantum bubble may transition into a floating self-bound droplet.