Room temperature superconductivity: One step closer to the Holy Grail of physics
Date: Wednesday, July 09, 2008 @ 21:11:53 GMT Topic: Science
Scientists at the University of Cambridge have for the first time
identified a key component to unravelling the mystery of room
temperature superconductivity, according to a paper published in
today's edition of the scientific journal Nature.
The quest for room temperature
superconductivity has gripped physics researchers since they saw the
possibility more than two decades ago. Materials that could potentially
transport electricity with zero loss (resistance) at room temperature
hold vast potential; some of the possible applications include a
magnetically levitated superfast train, efficient magnetic resonance
imaging (MRI), lossless power generators, transformers, and
transmission lines, powerful supercomputers, etc.
Unfortunately, scientists have
been unable to decipher how copper oxide materials superconduct at
extremely cold temperatures (such as that of liquid nitrogen), much
less design materials that can superconduct at higher temperatures.
Materials that are known to superconduct at the highest
temperatures are, unexpectedly, ceramic insulators that behave as
magnets before 'doping' (the method of introducing impurities to a
semiconductor to modify its electrical properties). Upon doping charge
carriers (holes or electrons) into these parent magnetic insulators,
they mysteriously begin to superconduct, i.e. the doped carriers form
pairs that carry electricity without loss.
The essential conundrum facing
researchers in this area has been: how does a magnet that cannot
transport electricity transform into a superconductor that is a perfect
conductor of electricity? The Cambridge team have made a significant
advance in answering this question.
The researchers have discovered where the charge 'hole' carriers
that play a significant role in the superconductivity originate within
the electronic structure of copper-oxide superconductors. These
findings are particularly important for the next step of deciphering
the glue that binds the holes together and determining what enables
them to superconduct.
Dr Suchitra E. Sebastian, lead author of the study, commented, "An
experimental difficulty in the past has been accessing the underlying
microscopics of the system once it begins to superconduct.
Superconductivity throws a manner of 'veil' over the system, hiding its
inner workings from experimental probes. A major advance has been our
use of high magnetic fields, which punch holes through the
superconducting shroud, known as vortices - regions where
superconductivity is destroyed, through which the underlying electronic
structure can be probed.
"We have successfully unearthed for the first time in a high
temperature superconductor the location in the electronic structure
where 'pockets' of doped hole carriers aggregate. Our experiments have
thus made an important advance toward understanding how superconducting
pairs form out of these hole pockets."
By determining exactly where the doped holes aggregate in the
electronic structure of these superconductors, the researchers have
been able to advance understanding in two vital areas:
(1) A direct probe revealing the location and size of pockets of
holes is an essential step to determining how these particles stick
together to superconduct.
(2) Their experiments have successfully accessed the region betwixt
magnetism and superconductivity: when the superconducting veil is
partially lifted, their experiments suggest the existence of underlying
magnetism which shapes the hole pockets. Interplay between magnetism
and superconductivity is therefore indicated - leading to the next
question to be addressed.
Do these forms of order compete, with magnetism appearing in the
vortex regions where superconductivity is killed, as they suggest? Or
do they complement each other by some more intricate mechanism? One
possibility they suggest for the coexistence of two very different
physical phenomena is that the non-superconducting vortex cores may
behave in concert, exhibiting collective magnetism while the rest of
the material superconducts.
Source: University of Cambridge Via: http://www.physorg.com/news134828104.html
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