Ground-state properties and elementary excitations of quantum droplets in dipolar Bose-Einstein condensates

TL;DR

This paper investigates the properties of quantum droplets in dipolar Bose-Einstein condensates, highlighting the role of quantum fluctuations in stabilization, phase regimes, and the characteristics of self-bound states and excitations.

Contribution

It provides a detailed analysis of the phase diagram, stabilization mechanisms, and excitations of quantum droplets, including the first characterization of three-dimensionally self-bound condensates.

Findings

Identification of three main regimes: mean-field, droplet, and multi-stable.

Quantum stabilization enables self-bound three-dimensional condensates.

Characterization of low-lying excitations in trapped and self-bound states.

Abstract

Recent experiments have revealed the formation of stable droplets in dipolar Bose-Einstein condensates. This surprising result has been explained by the stabilization given by quantum fluctuations. We study in detail the properties of a BEC in the presence of quantum stabilization. The ground-state phase diagram presents three main regimes: mean-field regime, in which the quantum correction is perturbative, droplet regime, in which quantum stabilization is crucial, and a multi-stable regime. In the absence of a multi-stable region, the condensate undergoes a crossover from the mean-field to the droplet solution marked by a characteristic growth of the peak density that may be employed to clearly distinguish quantum stabilization from other stabilization mechanisms. Interestingly quantum stabilization allows for three-dimensionally self-bound condensates. We characterized these self-bound solutions, and discuss their realization in experiments. We conclude with a discussion of the lowest-lying excitations both for trapped condensates, and for self-bound solutions.