Spinning superfluid helium-4 nanodroplets

TL;DR

This study uses Density Functional theory to analyze spinning superfluid helium-4 nanodroplets, revealing how vortex nucleation influences their shape and rotational behavior, aligning well with experimental observations.

Contribution

It demonstrates that vortex nucleation induces rigid-body rotation in superfluid droplets, explaining their shape evolution and matching experimental results.

Findings

Vortex nucleation leads to shape transitions from oblate to prolate to two-lobed.

Vortex arrays enable superfluid droplets to mimic rigid-body rotation.

Theoretical results agree with experimental observations.

Abstract

We have studied spinning superfluid $^4$He nanodroplets at zero temperature using Density Functional theory. Due to the irrotational character of the superfluid flow, the shapes of the spinning nanodroplets are very different from those of a viscous normal fluid drop in steady rotation. We show that when vortices are nucleated inside the superfluid droplets, their morphology, which evolves from axisymmetric oblate to triaxial prolate to two-lobed shapes, is in good agreement with experiments. The presence of vortex arrays confers to the superfluid droplets the rigid-body behavior of a normal fluid in steady rotation, and this is the ultimate reason of the surprising good agreement between recent experiments and the classical models used for their description.