Alexa Erickson – Objects that take up space and have mass are considered matter, which means that everything around you is made up of matter, including yourself and the sandwich in your hand.
Sound like the beginning of a lecture from your childhood science textbook? That’s because we’ve been taught that matter as we know it is as fundamental and broad as this.
But new research reveals that maybe “matter” isn’t so set in stone.
Scientists at the Massachusetts Institute of Technology (MIT) have produced a brand new form of matter called a supersolid. Until this creation, physicists had an idea supersolids might be possible, but hadn’t analyzed them in the laboratory.
A supersolid combines the properties of solids with those of superfluids.
To create it, the team of researchers used lasers to manipulate a superfluid gas called a Bose-Einstein condensate into a quantum phase of matter that has a rigid structure like a solid, but is able to flow with viscosity, like a superfluid.
This phase of matter, entirely contradictory, could provide valuable information currently unknown regarding superfluids and superconductors. Such insights could help improve technologies like superconducting magnets and sensors, as well as efficient energy transport.
“It is counterintuitive to have a material which combines superfluidity and solidity,” explained team leader Wolfgang Ketterle, the John D. MacArthur Professor of Physics at MIT. “If your coffee was superfluid and you stirred it, it would continue to spin around forever.”
The researchers used a combination of laser cooling and evaporative cooling methods co-developed by Ketterle to cool atoms of sodium to nanokelvin temperatures. Atoms of sodium, called bosons, were cooled to near absolute zero, which caused them to form a superfluid state of dilute gas known as Bose-Einstein condensate, or BEC.
“The challenge was now to add something to the BEC to make sure it developed a shape or form beyond the shape of the ‘atom trap,’ which is the defining characteristic of a solid,” says Ketterle, who co-discovered BECs.
The supersolid state was created by manipulating the motion of the atoms of the BEC with laser beads. Such a process is referred to as spin-orbit coupling.
Within an ultrahigh-vacuum chamber, the researchers used their first set of lasers to change half of the condensate’s atoms to a different quantum state, which created a combination of two Bose-Einstein condensates. The second set of lasers shifted atoms between the two condensates, called a “spin flip.”
“These extra lasers gave the ‘spin-flipped’ atoms an extra kick to realize the spin-orbit coupling,” Ketterle notes.
“The hardest part was to observe this density modulation,” explains Junru Li, an MIT graduate student involved in the study. “The recipe for the supersolid is really simple,” Li adds, “but it was a big challenge to precisely align all the laser beams and to get everything stable to observe the stripe phase.”
As of yet, the supersolid only exists at extremely low temperatures under ultrahigh-vacuum conditions.
“With our cold atoms, we are mapping out what is possible in nature,” says Ketterle. “Now that we have experimentally proven that the theories predicting supersolids are correct, we hope to inspire further research, possibly with unanticipated results.”
SF Source Collective Evolution March 2017