A supersolid is a paradoxical state of matter—it is rigid like a crystal but flows without friction like a superfluid. This exotic form of quantum matter has only recently been realized in dipolar quantum gases. Researchers led by Francesca Ferlaino set out to explore how the solid and superfluid properties of a supersolid interact, particularly under rotation. In their experiments, they rotated a supersolid quantum gas using a carefully controlled magnetic field and observed a striking phenomenon: "The quantum droplets of the supersolid are in a crystal-like periodic order, all dressed by a superfluid between them", explains Francesca Ferlaino "Each droplet precesses following the rotation of the external magnetic field; they all revolve collectively. When a vortex enters the system, precession and revolution begins to rotate synchronously."
"What surprised us was that the supersolid crystal didn't just rotate chaotically," says Elena Poli, who led the theoretical modeling. "Once quantum vortices formed, the whole structure fell into rhythm with the external magnetic field—like nature finding its own beat."
Andrea Litvinov, who conducted the experiments, adds: "It was thrilling to see the data suddenly align with the theory. There was a moment when the system just 'snapped into rhythm'."
A new probe for quantum matter
Synchronization is when two or more systems fall into rhythm with each other. It's common in nature—like pendulum clocks ticking in unison, fireflies flashing together, or heart cells beating in sync. The Innsbruck team showed that even exotic quantum matter can synchronize.
The discovery not only deepens understanding of this unusual state of matter but also offers a powerful new way to probe quantum systems. By tracking synchronization, the team was able to determine the critical frequency at which vortices appear— a fundamental property of rotating quantum fluids that has been difficult to measure directly.
The team combined advanced simulations with delicate experiments on ultracold atoms of dysprosium, cooled to just billionths of a degree above absolute zero. Using a technique called magnetostirring, they were able to rotate the supersolid and capture its evolution with high precision.
From the lab to the cosmos
The findings could have implications beyond the laboratory. Similar vortex dynamics are thought to play a role in sudden "glitches" observed in neutron stars, some of the densest objects in the universe. "Supersolids are a perfect playground to explore questions that are otherwise inaccessible," says Poli. "While these systems are created in micrometer-sized laboratory traps, their behavior may echo phenomena on cosmic scales."
"This work was made possible by the close collaboration between theory and experiment—and the creativity of the young researchers on our team," says group leader Francesca Ferlaino from the University of Innsbruck's Department of Experimental Physics and the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW). The research was conducted in partnership with the University of Trento's Pitaevskii BEC Center.
The study, published in Nature Physics, was supported by the Austrian Science Fund (FWF), the Austrian Research Promotion Agency (FFG), and the European Union, among others.
Publication: Synchronization in rotating supersolids. Elena Poli, Andrea Litvinov, Eva Casotti, Clemens Ulm, Lauritz Klaus, Manfred J. Mark, Giacomo Lamporesi, Thomas Bland, and Francesca Ferlaino. Nature Physics 2025 DOI: 10.1038/s41567-025-03065-7
