Austrian scientists have successfully observed evidence of the paradoxical state of matter known as supersolidity through the help of atomic gases.
Francesca Ferlaino, a professor at the University of Innsbruck and the Austrian Academy of Sciences, led two separate teams of researchers in looking for clues about supersolidity.
The phenomenon has been predicted as early as 50 years ago, but no one has exactly seen an object enter this exotic state before.
A supersolid is a counterintuitive phase of matter that roughly combines the properties of solids with those of superfluids.
Recent studies have resorted to using atomic gases, especially those with strong dipolar interactions, in the hopes of observing a supersolid matter in action.
Erbium And Dysprosium
For their experiment, Ferlaino and her colleagues focused on quantum gases of erbium and dysprosium. Lauriane Chomaz, one of the authors of the study, explained why they chose these two elements exactly.
"Recent experiments have revealed that such gases exhibit fundamental similarities with superfluid helium," Chomaz noted.
"These features lay the groundwork for reaching a state where the several tens of thousands of particles of the gas spontaneously organize in a self-determined crystalline structure while sharing the same macroscopic wavefunction -- hallmarks of supersolidity."
By tuning the strength of an interaction between the particles within erbium and dysprosium quantum gases, the researchers were able to produce states that manifest some characteristics of supersolidity.
The behavior of the supersolid in erbium was only transient, which was consistent with results of earlier experiments in Pisa and in Stuttgart, according to Ferlaino. However, they observed unprecedented stability when it came to dysprosium.
In the dysprosium realization, the researchers saw that the supersolid behavior of the element had a longer life. The phenomenon was also directly achievable through evaporative cooling, beginning with a thermal sample of dysprosium.
This could be likened to blowing over a cup of tea. If researchers were to remove the particles of the element with the most energies first, it would allow the gas to become cooler. It would also let the element reach a quantum-degenerate stationary state with properties of supersolidity at thermal equilibrium.
The discovery opens the door for new theories and experiments to be carried out regarding supersolidity.
The supersolid state observed in the study was not affected much by excitations or dissipative dynamics. This suggests that the excitation spectrum and superfluid behavior of elements could be worth exploring.
Similar Experiments On Supersolidity
In 2017, a research team at the Massachusetts Institute of Technology in the United States and another at ETH Zurich in Switzerland conducted two separate experiments on supersolidity. Both were able to create supersolids using a certain type of gas called Bose-Einstein condensate or BEC.
A BEC is the supposed fifth state of matter that often appears when elements are exposed to ultra-cold temperatures, which causes their atoms to behave much like waves. It is believed to be the most suitable form to use to create supersolids because it already has properties of superfluids.
The findings of the University of Innsbruck and Austrian Academy of Sciences study are featured in the journal Physical Review X.
