Newly discovered 'superinsulators' promise to transform materials research,
electronics design
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ARGONNE, Ill. (April 4, 2008) – Superinsulation may sound like a marketing
gimmick for a drafty attic or winter coat. But it is actually a newly discovered
fundamental state of matter created by scientists at the U.S. Department
of Energy's Argonne National Laboratory in collaboration with several European
institutions. This discovery opens new directions of inquiry in condensed
matter physics and breaks ground for a new generation of microelectronics.
Funding for this experiment came principally from the
Novosibirsk Institute of Semiconductor Physics and the University of Regensberg. The Basic
Energy Sciences Division of the Department of Energy's Office
of Science and Argonne Materials Theory Institute also contributed
in part to the research. |
Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana
Baturina, an international team of scientists from Argonne, Germany, Russia
and Belgium fashioned a thin film of titanium nitride which they then chilled
to near absolute zero. When they tried to pass a current through the material,
the researchers noticed that its resistance suddenly increased by a factor
of 100,000 once the temperature dropped below a certain threshold. The same
sudden change also occurred when the researchers decreased the external magnetic
field.
Like superconductors, which have applications in many different areas of physics,
from accelerators to magnetic-levitation (maglev) trains to MRI machines, superinsulators
could eventually find their way into a number of products, including circuits,
sensors and battery shields.
If, for example, a battery is left exposed to the air, the charge will eventually
drain from it in a matter of days or weeks because the air is not a perfect
insulator, according to Vinokur. "If you pass a current through a superconductor,
then it will carry the current forever; conversely, if you have a superinsulator,
then it will hold a charge forever," he said.
"Titanium nitride films, as well as films prepared from some other materials,
can be either superconductors or insulators depending on the thickness of the
film," Vinokur said. "If you take the film which is just on the insulating
side of the transition and decrease the temperature or magnetic field, then
the film all of a sudden becomes a superinsulator."
Scientists could eventually form superinsulators that would encapsulate superconducting
wires, creating an optimally efficient electrical pathway with almost no energy
lost as heat. A miniature version of these superinsulated superconducting wires
could find their way into more efficient electrical circuits.
Titanium nitride's sudden transition to a superinsulator occurs because the
electrons in the material join together in twosomes called Cooper
pairs. When
these Cooper pairs of electrons join together in long chains, they enable the
unrestricted motion of electrons and the easy flow of current, creating a superconductor.
In superinsulators, however, the Cooper pairs stay separate from each other,
forming self-locking roadblocks.
"In superinsulators, Cooper pairs avoid each other, creating enormous
electric forces that oppose penetration of the current into the material," Vinokur
said. "It's exactly the opposite of the superconductor," he added.
The theory behind the experiment stemmed from Argonne's Materials Theory
Institute, which Vinokur organized six years ago in the laboratory's Materials
Science Division. The MTI hosts a handful of visiting scholars from around
the world to perform cutting-edge research on the most pressing questions in
condensed matter physics. Upon completion of their tenure at Argonne, these
scientists return to their home institutions but continue to collaborate on
the joint projects. The MTI attracts the world's best condensed matter scientists,
including Russian "experimental star" Tatyana Baturina, who, according
to Vinokur, "became a driving force in our work on superinsulators."
Scientists from the Institute
of Semiconductor Physics in Novosibirsk, Russia, Regensburg and
Bochum universities
in Germany and Interuniversity
Microelectronics Centre in Leuven, Belgium, also
participated in the research.
The research appears in the April 3 issue of Nature.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology.
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Argonne, LLC for
the U.S.
Department of Energy's Office
of Science.
By Jared Sagoff.
For more information, please
contact Steve McGregor (630/252-5580 or media@anl.gov)
at Argonne.
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