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Forced pairing makes new form of matter


False colour images of the fermionic condensate. Images from left to right correspond to the increasing strength of attraction as the magnetic field strength varies (NIST)

U.S. scientists have made a new form of matter from pairs of atoms in a gas they say could one day be used in hovering trains or superconductors.

Scientists had been trying to make this new form of matter, known as a fermionic condensate, but with no success.

But a team from the National Institute of Standards and Technology's joint lab with the University of Colorado at Boulder were successful late last year.

Physicist, Adjunct Assistant Professor Deborah Jin and her team published their work online this week in the journal Physical Review Letters.

A fermionic condensate is the sixth known form of matter. The others are gases, solids, liquids, plasma and a Bose-Einstein condensate, created only in 1995.

Jin and her colleagues' cloud of supercooled potassium atoms is one step closer to an everyday, usable superconductor, a material that conducts electricity without losing any of its energy.

"It is related to a Bose-Einstein condensate," Jin said. "It's not a superconductor but it is really something in between these two that may help us in science link these two interesting behaviours."

Other researchers may find practical applications.

"If you had a superconductor you could transmit electricity with no losses," Jin said.

Or superconductors could allow for the invention of magnetically levitated trains, she added. They could glide along at high speeds using a fraction of the energy trains now use as they would be free of friction.

Jin was building on the discovery of the Bose-Einstein condensate by colleagues Dr Eric Cornell and Professor Carl Wieman. They won the 2001 Nobel Prize in Physics for their discovery.

Bose-Einstein condensates are collections of thousands of ultracold particles that occupy a single quantum state; they all essentially behave like a single, huge superatom.

But Jin said these Bose-Einstein condensates are made with bosons, which like to act in unison.

"Bosons are copycats. They basically want to do what everyone else is doing," she said.

Fermions just want to be alone

The new form of matter that Jin's team found comprised fermions, the everyday building blocks of matter that include protons, electrons and neutrons.

"They are not copycats," Jin said. "Fermions are your independent thinkers; they don't copy their neighbours."

No fermion can be in exactly the same state as another. So some physicists think the term fermionic condensate is contradictory.

But Jin's team coaxed them to come together and pair up, but only under extreme conditions.

The researchers cooled a gas of 500,000 potassium atoms to a fraction above absolute zero, the point at which matter stops moving.

They confined the gas in a vacuum chamber and used magnetic fields and lasers to manipulate the potassium atoms into pairing up.

"This is very similar to what happens to electrons in a superconductor," Jin said.

Fermionic condensates are more likely to provide applications in the practical world than a Bose-Einstein condensate, she said, because fermions make up solid matter.

Bosons, in contrast, are seen in photons and subatomic particles called W and Z particles.

Jin stressed her team worked with a supercooled gas, which provided little opportunity for everyday applications. But the way the potassium atoms acted suggested there should be a way to translate the behaviour into a solid at room temperature.

"Our atoms are more strongly attracted to one another than in normal superconductors," she said.

Tags: computers-and-technology, physics