Physicists Spot Quantum Tornadoes Twirling in a ‘Supersolid’

In a lab nestled between the jagged peaks of the Austrian Alps, rare earth metals vaporize and spew out of an oven at the speed of a fighter jet. Then a medley of lasers and magnetic pulses slow the gas nearly to a halt, making it colder than the depths of space. The roughly 50,000 atoms in the gas lose any sense of identity, merging into a single state. Finally, with a twist of the ambient magnetic field, tiny tornadoes swirl into existence, pirouetting in the darkness.

For three years, the physicist Francesca Ferlaino and her team at the University of Innsbruck worked to image these quantum-scale vortices in action. “Many people told me this would be impossible,” Ferlaino said during a tour of her lab this summer. “But I was so convinced that we would manage.”

Now, in a paper published today in Nature, they’ve published snapshots of the vortices, confirming the long-sought hallmark of an exotic phase of matter known as a supersolid.

The supersolid, a paradoxical phase of matter that’s simultaneously the stiffest of solids and the flowiest of fluids, has fascinated condensed matter physicists since its prediction in 1957. Hints of the phase have been mounting, but the new experiment secures the last major piece of evidence for its existence. The authors believe the vortices that form in supersolids can help explain properties in a range of systems, from high-temperature superconductors to astronomical bodies.

The vortices might show how matter behaves in some of the most extreme conditions in the universe. Pulsars, which are spinning neutron stars — the extraordinarily dense corpses of burnt-out stars — are suspected to have supersolid interiors. “This is actually a really good analogue system” for neutron stars, said Vanessa Graber, a physicist at Royal Holloway, University of London in the United Kingdom who specializes in these stars. “I’m really excited about that.”

Rigid and Runny

Imagine spinning a bucket filled with different kinds of matter. A solid will twirl along with the container because of the friction between the bucket and the material’s rigid lattice of atoms. A liquid, on the other hand, has less internal friction, so it will form a big vortex in the center of the bucket. (The exterior atoms rotate with the bucket while the inner ones lag behind.)

If you make certain liquids cold and sparse enough, their atoms begin interacting across longer distances, eventually linking together in one giant wave that flows perfectly without any friction. These so-called superfluids were first discovered in helium in 1937 by Russian and Canadian physicists.