New superconductors present new mysteries, possibilities
Posted on Sunday, June 08, 2008 @ 22:43:01 UTC by vlad
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Johns Hopkins University researchers and colleagues in China have
unlocked some of the secrets of newly discovered iron-based
high-temperature superconductors, research that could result in the
design of better superconductors for use in industry, medicine,
transportation and energy generation.
In an article published today in the journal Nature,
the team, led by Chia-Ling Chien, the Jacob L. Hain Professor of
Physics and director of the Material Research Science and Engineering
Center at The Johns Hopkins University, offers insights into why the
characteristics of a new family of iron-based superconductors reveal
the need for fresh theoretical models which could, they say, pave the
way for the development of superconductors that can operate at room
temperature.
"It appears to us that the new iron-based
superconductors disclose a new physics, contain new mysteries and may
start us along an uncharted pathway to room temperature
superconductivity," said Chien, who teamed up on the research with
Tingyong Chen and Zlatko Tesanovic, both of Johns Hopkins, and X.H.
Chen and R.H. Liu of the Hefei National Laboratory for Physical Science
at Microscale and Department of Physics, University of Science and
Technology of China in Anhui, China.
Superconductors are materials that can carry electrical current
without friction and as a result, don't waste electrical energy
generating heat. (Imagine your laptop computer or PC not getting warm
when it is turned on.) This means that an electrical current can flow
in a loop of superconducting wire forever without a power source.
Today, superconductors are used in hospital MRI machines, as filters in
cell phone base stations and in high-speed magnetic levitating trains.
Unfortunately, most of today's superconducting materials can only
function and operate at extremely low temperatures, which means that
they must be paired with expensive supercooling equipment. This
presents researchers with a grand challenge: to find superconducting
material that can operate at more "normal" temperatures.
"If superconductors could exist at room temperatures, the world energy crisis would be solved," Chen said.
Chen explains that though all metals contain mobile electrons which
conduct electricity, a metal becomes a superconductor only when two
electrons with opposite "spins" are paired. The superconductor energy
"gap," which is the amount of energy that would be needed to break the
bond between two electrons forming such a pair to release them from one
another, determines the robustness or strength of the superconducting
state. This energy gap is highest at low temperatures, but vanishes at
the temperatures at which superconductivity ceases to exist.
"This gap -- its structure and temperature dependence -- reveal the
'soul' of the superconductor, and this is what was measured in our
experiment," Chien said.
The team measured this gap and its temperature variation, revealing
that the pairing mechanism in iron-based superconductors is different
from the one in more traditional, copper-based, high-temperature
superconductors. To the researchers' surprise, their results were
incompatible with some of the newly proposed theories in this
mushrooming field.
"In the face of this discovery, it is clear that we need to
reexamine the old and invent some new theoretical models," Tesanovic
said. "I predict that these new, iron-based superconductors will keep
us physicists busy for a long, long while."
Source: Johns Hopkins University
Via: http://www.physorg.com/news131813340.html
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