This will help scientists study the characteristics of supersolids under extreme conditions while also examining certain aspects of celestial objects like neutron stars.
As a kid, you probably learned that there are three states of matter: solid, liquid, and gas. But like most things in life, it gets a bit more complicated as you get older. For example, super hot plasma powering the Sun (and, hopefully, future fusion reactors) is an important fourth state of matter, and the fifth -- the super-cold Bose-Einstein Condensates -- helps scientists study the nature of the quantum world.
But it gets even more complicated. Within these states of matter reside other, potentially even more counterintuitive objects. Take, for example, the supersolid -- a material that's both a superfluid (exotic matter with zero viscosity) and a solid. The existence of this bizarre example of matter was first hypothesized more than half a century ago, but examining a supersolid's free-flowing atoms through its crystalline lattice has been an extremely difficult undertaking. Now, scientists from University of Innsbruck in Austria state in a new paper (published in the journal Nature) that they've successfully stirred a two-dimensional supersolid and observed "quantum vortices" -- a phenomenon that physicist Francesca Ferlaino told AFP is the "smoking gun of superfluidity."
"It is a bit like Schrödinger's cat, which is both alive and dead, a supersolid is both rigid and liquid," Ferlaino said in a press statement. "This work is a significant step forward in understanding the unique behavior of supersolids and their potential applications in the field of quantum matter."
The first stage of this remarkable breakthrough actually occurred back in 2021, when Ferlaino's team developed the first long-lived, two-dimensional supersolid out of an ultracold gas of erbium atoms, a rare-earth metal. At the time, supersolids had only been observed as a series of droplets in one dimension. The team hoped that this first breakthrough could allow for the study of vortices within the supersolid itself. While that hope wasn't misplaced, observing those quantum tornadoes was far from simple.
"The next step -- developing a way to stir the supersolid without destroying its fragile state -- required even greater precision," Eva Casotti, lead author of the study, said in a press statement.
The team used magnetic fields to deftly rotate the supersolid, and because liquids within the lattice of the supersolid don't rotate rigidly, this high-precision movement created quantum vortices that are a tell-tale sign of superfluidity. The discovery of this phenomenon has big implications for laboratory studies of supersolid dynamics in exotic conditions, but it could also help answer some questions about one of the most extreme celestial objects in the known universe: the neutron star.
"It is assumed that the change in rotational speed observed in neutron stars -- so-called glitches -- are caused by superfluid vortices trapped inside neutron stars," Thomas Bland, co-author of the study, said in a press statement. "Our platform offers the opportunity to simulate such phenomena right here on Earth."