Giant vortices discovered in superfluid helium express
Liquid helium at ultra-low temperatures flows without friction — like an ideal lubricant. Within it, whirlpools form, similar to ordinary ones in water, but their rotational strength shifts only in strict steps, like a record player — only 33, 45, or 78 rpm. This law, discovered by Lev Landau, seemed eternal.
But when scientists introduced spy dust grains into the helium, they sometimes began to spin furiously, as if the record played at every speed at once. Such a "clump" ought to instantly fall apart, like a vinyl on a mode that doesn't exist. Yet the dust grain held firm inside, and the vortex itself lived suspiciously long.
The discovery shakes up vortex science in frictionless fluids and promises insights into other similar media — from the cores of neutron stars to atomic nuclei.
Original abstract
as written by the authors arXiv:2603.05387
Quantized vortex dynamics in superfluid $$^4$$He (He~II) are widely regarded as well established: circulation is quantized in units of $$\kappa=h/m_4$$, vortices carrying more than one quantum are expected to split into singly quantized filaments, and vortex rings shrink while accelerating due to dissipation from thermal-quasiparticle scattering. Using particle tracking velocimetry with frozen deuterium tracers, we uncover rare vortex-bound particle events that disrupt this canonical picture. In a class of events exhibiting the acceleration characteristic of shrinkage driven vortex ring motion, the measured kinematics cannot be reconciled with a singly quantized ring. Instead, they require an effective circulation $$n\kappa$$ with $$n>1$$, directly challenging the standard expectation that multiquantum vortices are short lived. A more prosaic possibility is that the inferred $$n\kappa$$ arises from a bundle of closely spaced singly quantized rings, which could generate similar large-scale motion. However, this scenario is disfavored by vortex-filament simulations that show rapid bundle dispersion. Furthermore, the persistence of particle trapping at the observed high speeds suggests a much deeper core trapping potential, consistent only with a truly multiquantum core. Together, these results point to anomalously long-lived multiquantum rings, a striking puzzle that calls for dedicated scrutiny beyond the prevailing paradigm.
Frictionless helium, cooled to near absolute zero, can circulate forever in a ring — nothing slows it down.