5th Institute of Physics

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Self-bound droplets of a quantum liquid

We report on the first observation of stable self-bound droplets of a dilute magnetic quantum liquid. In contrast to classical liquid droplets, e.g. water, our droplets are eight orders of magnitude colder and more dilute. The quantum liquid consists of dysprosium atoms, which possess the highest magnetic moment of all elements and therefore can be seen as tiny magnets. This strong magnetic moment is essential as the creation of such quantum droplets requires a balance between attractive and repulsive forces. Additionally, we were able to study the phase transition between liquid and gas.

In our case, a balance of three interactions ensure the stability of these droplets. The repulsive term is composed of the contact interaction and quantum fluctuations while the attraction is a result of the dipolar interaction. As the two repulsive interactions both scale with the contact interaction parameter (scattering length a), we studied the phase transition for different relative interaction strengths between contact and dipolar interaction.

To study these phenomena, we created a single quantum droplet consisting of 3,000 atoms in a crossed dipole trap that produces an almost round trapping potential. At this point, we adiabatically turned off our trapping potential and observed stable quantum droplets for up to 100 ms while levitating them with a magnetic field gradient. During this levitation time, the droplets lost atoms due to three-body recombination and fully evaporated back to a gas phase as soon as they reached a critical atom number. We finally studied the critical atomnumber, and hence the phase transition, for different values of the scattering length and compared it to a theoretical model.


This work titled "Self-bound droplets of a dilute magnetic quantum liquid" has been published in "Nature":




Read the news & views by Bruno Laburthe-Tolra



Mentioned as research highlight by Iulia Georgescu



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Interview about the publication (only in german)


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