Theory for self-bound states of dipolar Bose-Einstein condensates
Yuqi Wang, Longfei Guo, Su Yi, Tao Shi
Abstract
Ultracold gases of dipolar Dy have emerged as platforms where studying novel phases of matter, such as liquid droplets, poses many questions since standard theoretical methods fail to account for some of their observed properties. Here we investigate the self-bound states of dipolar Dy condensates by using general Gaussian-state ansatzes which go beyond conventional coherent-state ansatzes by including multimode squeezing. Our theory provides a transition between self-bound liquid and gas phases that agrees well with experimental observations and additionally reveals an experimentally unexplored transition in the self-bound gas region from a coherentdominated to a squeezed-dominated phase. Our theory also allows one to extract the real part of the three-body interaction strength of the Dy atoms from the particle number distribution of the condensates. This allows us to show that the self-bound states are stabilized by the short-range three-body repulsion. Our study sheds a different light onto the properties of self-bound droplets of Bose-Einstein condensates.