Artist's impression of supersolid, which can be described as a mixture of a solid or a liquid.
Two-dimensional supersolid is the first time physicists have ever created a phase of matter that acts like both a liquid and a solid.
Supersolids are materials that have atoms arranged in a repeating, regular crystal structure. They can also flow for countless hours without losing any kinetic energy. Although their strange properties seem to be against many laws of physics, they have been predicted by physicists for years. They first appeared in Eugene Gross's 1957 work.
Now, using super-chilled gas and lasers, scientists have managed to convert a supersolid into an 2D structure. This breakthrough could allow scientists to unravel the deeper physics behind the strange properties of the matter phase.
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Researchers are particularly interested in how the 2D supersolids behave when spun in a circular motion. They also want to see the vortices or whirlpools that may form inside.
"We expect there to be much to learn by studying rotational oscillations," Matthew Norcia (a physicist from Innsbruck University’s Institute for Quantum Optics and Quantum Information, in Austria) told Live Science via email.
The team created their supersolid by suspending a cloud made of dysprosium-164 atoms in optical tweezers. After cooling the atoms to just above zero Kelvin (minus 459.67 degrees Fahrenheit or minus 273.15 Celsius), they used a laser-cooling technique.
A laser beam can heat up a gas, but if the light particles (photons) traveling in the opposite direction to the moving gas particles, it can cause them to slow down and cool them. The laser had cooled the dysprosium molecules as far as possible. However, the researchers removed the grip of their optical tweezers to allow the most energetic atoms escape.
Because "warmer" particles move faster than those of cooler ones, the researchers used evaporative cooling to cool them down. The super-cooled atoms were then transformed into a new phase called Bose-Einstein Condensate, which is a collection of atoms that has been super-cooled to a fraction of absolute zero.
All atoms in a gas lose their energy when it is cooled to a near-zero temperature. They then enter the same energy states. Because we cannot distinguish the atoms of a gas cloud that are not identical by looking at their energy levels alone, this equalizing can have a profound effect. The previously disparate cloud of vibrating jiggling, colliding gas atoms then becomes, from a quantum mechanical perspective, completely identical.
This opens up the possibility of some really bizarre quantum effects. Heisenberg's uncertainty principle is a key rule in quantum behavior. It states that you can't know a particle's momentum and its position with absolute accuracy. All of the momentum for Bose-Einstein condensate particles is now known, even though they aren't moving. The atoms' positions are now so uncertain, the areas they could occupy become larger than the spaces between them.
Instead of having discrete atoms, the overlapping BoseEinstein condensate balls act as one large particle. Some BoseEinstein condensates have the superfluidity property, which allows their particles to flow freely without friction. It is possible to swirl a Bose Einstein superfluid condensate by stirring it.
Researchers used dysprosium-164, an isotope, to study the magnetic properties of Dysprosium. It is also the most magnetic element discovered. The supercooled dysprosium-164 molecules clumped together and became superfluid.
Norcia explained that the team created a one-dimensional tube of droplets with free-flowing atoms by "carefully tuning" the balance between long and short-range magnetic interactions. This was their previous work.
The team created a larger trap to make the jump from a 1D supersolid to a 2D supersolid. They also decreased the intensity of the optical tweezer beams in two directions. They were able to create a zigzag structure of droplets similar to two 1D tubes that are placed next to each other.
Now that they have completed the task of creating it, the physicists want to make use of their 2D supersolid to explore all the properties that arise from this additional dimension. They plan to study vortices which emerge from the array and get trapped between them, particularly since these eddies can spiral indefinitely, at least theoretically.
Researchers are now one step closer towards the bulk, 3D supersolids that Gross' early proposals envisioned, as well as the alien properties they might have.
August 18th, the researchers published their findings in Nature.
Original publication on Live Science
