Super­solid State of Matter in a new Dimen­sion

Super­solid state of matter that was confirmed a few years ago, now is created in a new two-dimensional form.

Quantum matter can be solid and fluid at the same time – a situation known as supersolidity.



Researchers led by Francesca Ferlaino have now created for the first time this fascinating property along two dimensions. They now report in the journal Nature on the realization of supersolidity along two axes of an ultracold quantum gas.

Quantum gases are very well suited for investigating the microscopic consequences of interactions in matter. Today, scientists can precisely control individual particles in extremely cooled gas clouds in the laboratory, revealing phenomena that cannot be observed in the every-day world. For example, the individual atoms in a Bose-Einstein condensate are completely delocalized. This means that the same atom exists at each point within the condensate at any given time. Two years ago, the research group led by Francesca Ferlaino from the Department of Experimental Physics at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information at the Austrian Academy of Sciences in Innsbruck managed for the first time to generate supersolid states in ultracold quantum gases of magnetic atoms. The magnetic interaction causes the atoms to self-organize into droplets and arrange themselves in a regular pattern. “Normally, you would think that each atom would be found in a specific droplet, with no way to get between them,” says Matthew Norcia of Francesca Ferlaino’s team. “However, in the supersolid state, each particle is delocalized across all the droplets, existing simultaneously in each droplet. So basically, you have a system with a series of high-density regions (the droplets) that all share the same delocalized atoms.” This bizarre formation enables effects such as frictionless flow despite the presence of spatial order (superfluidity).
New dimensions, new effects to explore

Until now, supersolid states in quantum gases have only ever been observed as a string of droplets (along one dimension). “In collaboration with theorists Luis Santos at Leibniz Universität Hannover and Russell Bisset in Innsbruck we have now extended this phenomenon to two dimensions, giving rise to systems with two or more rows of droplets,” explains Matthew Norcia. This is not only a quantitative improvement, but also crucially broadens the research perspectives. “For example, in a two-dimensional supersolid system, one can study how vortices form in the hole between several adjacent droplets,” he says. “These vortices described in theory have not yet been demonstrated, but they represent an important consequence of superfluidity,” Francesca Ferlaino is already looking into the future. The experiment now reported in the journal Nature creates new opportunities to further investigate the fundamental physics of this fascinating state of matter.

Image: Two-dimensional supersolid quantum gas produced in the laboratory for the first time (Credit: IQOQI Innsbruck/Harald Ritsch)



source University of Innsbruck