About 60 years ago, it was theorized regarding the existence of supersolids. What was postulated? That there was a supposed matter that had characteristics of solid and liquid states at the same time. Now a recent study from Nature noted that supersolid states simultaneously exhibit properties typically associated with a solid and a superfluid.
As a solid, they have a crystalline order, manifesting as a periodic modulation of the density of the particles; but unlike a typical solid, also have superfluid properties, as a result of the coherent delocalization of particles throughout the system.
These states, the research authors explained Matthew Norcia, Claudia Politi, Lauritz Klaus, Elena Poli, Maximilian Sohmen, Manfred Mark, Russell Bisset, Luis Santos and Francesca Ferlaino, were initially envisioned in the context of bulk solid helium, as a possible answer to the question of whether a solid could have superfluid properties. Although super-solidity has not been observed in solid helium (despite much effort), ultracold atomic gases provide an alternative approach, which recently allowed the observation and study of supersolids with dipole atoms.. However, unlike the proposed phenomena in helium, these gaseous systems have so far only shown supersolidness in a single direction.
“With this finding We demonstrate the extension of supersolid properties in two dimensions by preparing a supersolid quantum gas of dysprosium atoms on both sides of a structural phase transition similar to those that occur in ionic chains, quantum wires and theoretically in chains of dipole particles. individual“, the researchers specified in the scientific paper. This opens the possibility of studying rich excitation properties, including the formation of vortices and ground-state phases with varied geometric structure in a highly flexible and controllable system.
The team of physicists managed to generate, for the first time, in a parallel way between laboratories in the Universities of Innsbruck, Pisa and Stuttgart, supersolid states from highly magnetic lanthanide atoms frozen quantum gases. “Due to quantum effects, a very cold gas of atoms can spontaneously develop both an order of a solid crystal and a flow of particles as a superfluid quantum liquid, that is, a fluid capable of flowing without any friction.”, He explained Francesca Ferlaino, one of the main authors. That is, it has the structure of a crystal, but the particles inside it ‘flow’ like a liquid, because they are delocalized.
The magnetic interaction causes the atoms to self-organize into a kind of “droplet” and organize themselves in a regular pattern. “What they have achieved is to ‘convince’ a matter that tends to expand to confine itself in a regular structure,” explained Juan José García Ripoll, theoretical physicist at the Institute of Fundamental Physics, dependent on the CSIC. “Other experiments had been done but forcing matter.This approach is based on the fact that matter somehow decides by itself to reach this state. And it is also a predictable and reproducible system, making it a new milestone in fundamental physics.”He added.
Other perspectives, different angles
The characteristic of these atoms that are found within these ordered drops and that form a crystalline structure is that “each particle is delocalized through all the drops, existing simultaneously in each drop”, determined Matthew Norcia of Ferlaino’s team. Basically, you have a system with a series of high-density regions (the droplets) that share the same delocalized atoms. That is, the same atoms are in all the drops at the same time, creating a quantum wave, in a strange formation that allows effects such as frictionless flow -the most perfect fluidity, in colloquial terms- despite also having an order space.
But this study goes further. Up to now, supersolid states in quantum gases have only been observed as a chain of drops, along a single dimension. But, in collaboration with theorists Luis Santos, from the Leibniz Universität Hannover, and Russell Bisset, in Innsbruck, the team has managed to expand the phenomenon to two dimensions, which broadens the perspectives of the research. Something like being able to look at this new state from different angles. “For example, in a two-dimensional supersolid system, you can study how vortices are formed in the hole between several adjacent droplets,” Ferlaino added. These theoretically described vortices have not yet been proven, but they represent an important consequence of superfluidity ”.