According to foreign media reports, quantum gases are ideal for studying the microscopic consequences of matter interactions. Scientists can now precisely control individual particles in extremely cold gas clouds in the laboratory and reveal phenomena that are unobservable in the everyday world. For example, individual atoms in a Bose-Einstein condensate are completely delocalized. This means that at any given time, the same atom exists at every point in the condensate.
Two years ago, a research team led by Francesca Ferlaino from the Department of Experimental Physics at the University of Innsbruck, in collaboration with the Institute for Quantum Optics and Quantum Information at the Austrian Academy of Sciences in Innsbruck, successfully realized a supersolid state in an ultracold quantum gas of magnetic atoms for the first time. Magnetic interactions caused 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 particular droplet and could not enter each other,” said Matthew Norcia, a member of Francesca Ferlaino’s team. “However, in the supersolid state, each particle is delocalized on all the droplets and exists in every droplet at the same time. So basically, you have a system that has a series of high-density regions, and all of these regions share the same delocalized atoms.”
Despite the existence of spatial order (superfluidity), this exotic structure can produce effects such as frictionless flow.
New dimension, new effect
Until now, the supersolid state in quantum gases has only been observed as a string of droplets (along one dimension). "Through collaboration with theorists Luis Santos at Leibniz University Hannover and Russell Bisset at the University of Innsbruck, we have now extended this phenomenon to two dimensions and produced systems with two or more rows of droplets," notes Matthew Norcia. This is not only a quantitative improvement but also a significant broadening of the research perspective.
He said, "For example, in a two-dimensional supersolid system, one can study how vortices form in the pores between several adjacent water droplets." Francesca Ferlaino is already looking to the future, stating, "Although these theoretically described vortices have not yet been proven, they represent an important outcome for superfluids."
New research area: Supersolids
Fifty years ago, predictions were made that supersolids and their astonishing properties would be extensively studied in superfluid helium. However, after decades of theoretical and experimental research, there was still no definitive evidence to prove that the system was a supersolid. Two years ago, research teams from Pisa, Stuttgart, and Innsbruck independently and successfully created a so-called supersolid from magnetic atoms in an ultracold quantum gas for the first time. The foundation of this emerging and developing field of research on supersolids lies in the strong polarity of magnetic atoms, whose interaction properties make it possible to create this paradoxical quantum mechanical state of matter in the laboratory.
