Researchers in a new study brought the molecules down to just above the coldest possible temperature.
The molecules of sodium potassium or NaK were cooled to just 500 billionths of a degree Celsius over absolute zero. At this temperature, no more energy remains in the molecules that can be extracted as heat. The temperature was million times colder than the interstellar space.
Molecules of air generally collide into each other at speeds of several hundreds of miles per hour. Researchers suspected that if the gases were frozen down to temperatures just above absolute zero, the molecules would act together as a single unit. This strange form of matter was a theoretical idea and was never seen.
When the researchers brought the gas down to these ultracold temperatures, they found the magnetic difference in between poles of molecules became more pronounces. The molecules were also found to be come longer lived as the collision between the molecular units became less frequent. The molecules in this state traveled just inches per second, vibrating and tumbling at the lowest possible rate.
Martin Zwierlein of the Massachusetts Institute of Technology or MIT said, “We are very close to the temperature at which quantum mechanics plays a big role in the motion of molecules. So these molecules would no longer run around like billiard balls, but move as quantum mechanical matter waves.”
Sodium potassium was selected for the study because it is an example of the simplest class of molecules. The structure of the molecules is made up to just two atoms, one is potassium and the other is sodium, bound together like a dumbbell.
Molecules vibrate and tumble erratically, making it difficult for the material to freeze. Doing so with single atoms is a much easier task. Bringing the sodium potassium molecules to just above absolute zero was accomplished in a multistage process.
The first stage was evaporating cooling and lasers to slow down motions of the molecules. Later, magnets were used to coax the molecules into binding with one another, forming single large, supercold molecule. However, these bonds only bind the molecules together weakly, allowing the particles to vibrate faster than desired. A pair of lasers was then employed to bind the molecules together as a more cohesive hole.
Some of the theoretical properties of such supercold materials are bizarre when compared with the behavior of matter at room temperature.
Zwierlein said, “With ultracold molecules, you can get a huge variety of different states of matter, like superfluid crystals, which are crystalline, yet feel no friction, which is totally bizarre. This has not been observed so far, but predicted. We might not be far from seeing these effects, so we’re all excited.”