[Paleopsych] MIT: MIT physicists create new form of matter

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MIT physicists create new form of matter
June 22, 2005

CAMBRIDGE, Mass. -- MIT scientists have brought a supercool end to a heated 
race among physicists: They have become the first to create a new type of 
matter, a gas of atoms that shows high-temperature superfluidity.

Their work, to be reported in the June 23 issue of 
<http://www.nature.com/index.html>Nature, is closely related to the 
superconductivity of electrons in metals. Observations of superfluids may help 
solve lingering questions about high-temperature superconductivity, which has 
widespread applications for magnets, sensors and energy-efficient transport of 
electricity, said 
Wolfgang Ketterle, a Nobel laureate who heads the MIT group and who is the John 
D. MacArthur Professor of Physics as well as a principal investigator in MIT's 
Research Laboratory of Electronics.

Seeing the superfluid gas so clearly is such a dramatic step that Dan Kleppner, 
director of the MIT-Harvard Center for Ultracold Atoms, said, "This is not a 
smoking gun for superfluidity. This is a cannon."

For several years, research groups around the world have been studying cold 
gases of so-called fermionic atoms with the ultimate goal of finding new forms 
of superfluidity. A superfluid gas can flow without resistance. It can be 
clearly distinguished from a normal gas when it is rotated. A normal gas 
rotates like an ordinary object, but a superfluid can only rotate when it forms 
vortices similar to mini-tornadoes. This gives a rotating superfluid the 
appearance of Swiss cheese, where the holes are the cores of the 
mini-tornadoes. "When we saw the first picture of the vortices appear on the 
computer screen, it was simply breathtaking," said graduate student Martin 
Zwierlein in recalling the evening of April 13, when the team first saw the 
superfluid gas. For almost a year, the team had been working on making magnetic 
fields and laser beams very round so the gas could be set in rotation. "It was 
like sanding the bumps off of a wheel to make it perfectly round," Zwierlein 

"In superfluids, as well as in superconductors, particles move in lockstep. 
They form one big quantum-mechanical wave," explained Ketterle. Such a movement 
allows superconductors to carry electrical currents without resistance.

The MIT team was able to view these superfluid vortices at extremely cold 
temperatures, when the fermionic gas was cooled to about 50 billionths of a 
degree Kelvin, very close to absolute zero (-273 degrees C or -459 degrees F). 
"It may sound strange to call superfluidity at 50 nanokelvin high-temperature 
superfluidity, but what matters is the temperature normalized by the density of 
the particles," Ketterle said. "We have now achieved by far the highest 
temperature ever." Scaled up to the density of electrons in a metal, the 
superfluid transition temperature in atomic gases would be higher than room 

Ketterle's team members were MIT graduate students Zwierlein, Andre Schirotzek, 
and Christian Schunck, all of whom are members of the Center for Ultracold 
Atoms, as well as former graduate student Jamil Abo-Shaeer.

The team observed fermionic superfluidity in the lithium-6 isotope comprising 
three protons, three neutrons and three electrons. Since the total number of 
constituents is odd, lithium-6 is a fermion. Using laser and evaporative 
cooling techniques, they cooled the gas close to absolute zero. They then 
trapped the gas in the focus of an infrared laser beam; the electric and 
magnetic fields of the infrared light held the atoms in place. The last step 
was to spin a green laser beam around the gas to set it into rotation. A shadow 
picture of the cloud showed its superfluid behavior: The cloud was pierced by a 
regular array of vortices, each about the same size.

The work is based on the MIT group's earlier creation of Bose-Einstein 
condensates, a form of matter in which particles condense and act as one big 
wave. Albert Einstein predicted this phenomenon in 1925. Scientists later 
realized that Bose-Einstein condensation and superfluidity are intimately 

Bose-Einstein condensation of pairs of fermions that were bound together 
loosely as molecules was observed in November 2003 by independent teams at the 
University of Colorado at Boulder, the University of Innsbruck in Austria and 
at MIT. However, observing Bose-Einstein condensation is not the same as 
observing superfluidity. Further studies were done by these groups and at the 
Ecole Normale Superieure in Paris, Duke University and Rice University, but 
evidence for superfluidity was ambiguous or indirect.

The superfluid Fermi gas created at MIT can also serve as an easily 
controllable model system to study properties of much denser forms of fermionic 
matter such as solid superconductors, neutron stars or the quark-gluon plasma 
that existed in the early universe.

The MIT research was supported by the National Science Foundation, the Office 
of Naval Research, NASA and the Army Research Office.

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