Superfluid Plasma of Hexagonal Vortices
MIT Physicists Create New Form of Matter
MIT News Desk in Cambridge
June 22, 2005
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
Nature, is closely related to the superconductivity of electrons in metals.
In the left portion of the above illustration (images produced by Andre Schirotzek, MIT), the gas of fermions
(red) is trapped in an infrared laser beam (pink) and held in place by a magnetic field generated by current-
carrying coils (blue). Two additional laser beams, shown in green, were used like coffee stirrers to set the
gas into rotation. The result, as illustrated, could be seen in a shadow picture of the expanded cloud that
showed its superfluid behavior: The gas was pierced by a regular array of vortices. The rotating
superfluid gas of fermions is pierced with the vortices, which are like mini-tornadoes.
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 explained.
"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 one 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 temperature.
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 related.
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.
Interestingly, this superfluid plasma research at MIT has progressed simultaneously with the plasma beam research of Canadian Troy Hurtubise's work on a prototype called Angel Light, with the public announcements of their achievements coming within days of each other. This God Light article from BayToday.ca was published only five days before the MIT Newsdesk published their findings (above).
While the work of Ketterle's MIT group is focused on the structural movements of the vapor lattice, Hurtubise's plasma beam device is being used on the human body to heal Parkinson's disease and cancer (so far). As well, very similar work on resonant-transfer plasmas has been conducted by Dr. Randell Mills of Blacklight Power in the production of 'free' energy.
Evidently, the field of plasma physics can be applied to the human body in astounding ways, as has been described for decades by people who have had extraterrestrial encounters.