2004 News Releases
Proof of New State of Matter Is in the Jelly
||By observing the way their soup of
lithium-6 atoms jiggled at ultra-cold temperatures, NASA-funded
researchers hit upon the first direct evidence for a frictionless fluid
made up of fermion atoms. This series of pictures shows the "fermion
atom superfluid" oscillating inside a laser beam trap.
+ Larger image
April 27, 2004
In the community of very tiny particles that make up all matter in
the universe, there are two main citizens: bosons and fermions.
Bosons are socially oriented and tend to stick together, while
fermions are solitary entities, preferring to go it alone.
That's why NASA-funded researchers overcame an important technical
challenge when they recently persuaded reclusive fermion atoms to
act like their friendly boson buddies and jiggle together in an
ultra-cold, jelly-like state of matter.
The findings, published in the online version of Physical Review
Letters, represent the first direct evidence for a fermion atom
superfluid – a frictionless fluid made up of a gas of fermion atoms.
Such bizarre atomic soups will help physicists understand how matter
behaves at its most fundamental level, and will serve as models for
exotic systems in nature, such as neutron stars and new super- high-
temperature superconductors that could potentially function at
thousands of degrees Celsius.
"When you build airplanes, you begin with small-scale models. The
same idea can be applied to very high-temperature superconductors,
only the models are fermionic superfluid gases," said Dr. John
Thomas, a physics professor at Duke University, Durham, North
Carolina, and principal investigator for the new study. His research
is funded by a grant from NASA's Office of Biological and Physical
Research, Washington, through the Jet Propulsion Laboratory,
Superconductors are materials that permit electrical currents to
flow without resistance. They have potential applications in the
computer, power and transportation industries. Rail system designers
imagine using superconductors to build magnetically levitated
trains. But current superconductors require impractically cold
temperatures to work. Fermionic superfluid gases — the atomic
equivalent of superconducting electrons — might serve as rudimentary
blueprints for creating superconductors that work at much higher
The latest research builds on previous work by the Duke University
team outlining the creation of a possible fermion atom superfluid.
In that paper, reported in Science Magazine in 2002, the researchers
used an "optical bowl" made of a focused laser beam to trap lithium-
6 atoms (fermions) into a cigar-shaped cloud. They then chilled
their concoction to less than a millionth of a degree above absolute
zero, a temperature just above the point where no more cooling can
occur, and applied a small magnetic field.
The result was a transformation in character; the normally
antisocial atoms stacked up like peas in a pod and exhibited unusual
behavior. For instance, the gas expanded in one direction while
standing still in another when released from the bowl. Nonetheless,
the researchers could not find direct evidence that what they were
seeing was an actual superfluid — until now.
This time the researchers repeated the experiment at different
temperatures and then observed how long the fermionic gas jiggled,
or oscillated, after they switched the optical trap off and on,
essentially giving the gas a light tap. In a normal gas, collisions
between atoms should decrease as the temperature goes down,
producing an imperfect jelly whose oscillations die out quickly. In
a superfluid, the atoms act even more unified when temperatures are
lowered, and the oscillations should theoretically last forever.
What the team discovered was a jelly-like gas that wobbled for
increasingly longer times as the temperature decreased -- the first
direct signs of a fermion atom superfluid and the beginnings of a
new model for exploring the possibility of extremely high-
Other authors include Duke University researchers Joe Kinast, Staci
Hemmer, Mike Gehm and Andrey Turlapov. More information on the
research is available at:
http://www.dukenews.duke.edu/news/superfluid_0404.html. The press
release about the previous Duke University fermion research is at:
Information on the Office of Biological and Physical Research and
the Fundamental Physics Program is available at:
http://spaceresearch.nasa.gov and http://funphysics.jpl.nasa.gov.
The Thomas research was funded by NASA, the National Science
Foundation, the Department of Energy and the Army Reserve Office.
JPL manages the Fundamental Physics in Microgravity Research Program
for NASA's Office of Biological and Physical Research, Washington.
JPL is a division of the California Institute of Technology in
Whitney Clavin (818) 354-4673