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A step nearer to understanding superconductivity
June 07, 2007Transporting energy without any loss, travelling in magnetically levitated trains, carrying out medical imaging (MRI) with small-scale equipment: all these things could come true if we had superconducting materials that worked at room temperature. Today, researchers at CNRS have taken another step forward on the road leading to this ultimate goal. They have revealed the metallic nature of a class of so-called critical high-temperature superconducting materials. This result, which was published in the 31 May 2007 issue of the journal Nature, has been eagerly awaited for 20 years. It paves the way to an understanding of this phenomenon and makes it possible to contemplate its complete theoretical description.
Superconductivity is a state of matter characterized by zero electrical resistance and impermeability to a magnetic field. For instance, it is already used in medical imaging (MRI devices), and could find spectacular applications in the transport and storage of electrical energy without loss, the development of transport systems based on magnetic levitation, wireless communication and even quantum computers. However, for now, such applications are limited by the fact that superconductivity only occurs at very low temperatures. In fact, it was only once a way of liquefying helium had been developed, which requires a temperature of 4.2 kelvins (-269 °C), that superconductivity was discovered, in 1911 (a discovery for which the Nobel Prize was awarded two years later.)
Since the end of the 1980s (Nobel Prize in 1987), researchers have managed to obtain 'high temperature' superconducting materials: some of these compounds can be made superconducting simply by using liquid nitrogen (77 K, or -196 °C). The record critical temperature (the phase transition temperature below which superconductivity occurs) is today 138 K (-135 °C). This new class of superconductors, which are easier and cheaper to use, has given fresh impetus to the race to find ever higher critical temperatures, with the ultimate goal of obtaining materials which are superconducting at room temperature. However, until now, researchers have been held back by some fundamental questions. What causes superconductivity at microscopic scales" How do electrons behave in such materials"
Researchers at the National Laboratory for Pulsed Magnetic Fields2, working together with researchers at Sherbrooke, have observed 'quantum oscillations', thanks to their experience in working with intense magnetic fields. They subjected their samples to a magnetic field of as much as 62 teslas (a million times stronger than the Earth's magnetic field), at very low temperatures (between 1.5 K and 4.2 K). The magnetic field destroys the superconducting state, and the sample, now in a normal state, shows an oscillation of its electrical resistance as a function of the magnetic field. Such an oscillation is characteristic of metals: it means that, in the samples that were studied, the electrons behaved in the same way as in ordinary metals.
The researchers will be able to use this discovery, which has been eagerly awaited for 20 years, to improve their understanding of critical high-temperature superconductivity, which until now had resisted all attempts at modeling it. The discovery has been effective in sorting out the many theories which had emerged to explain the phenomenon, and provides a firm foundation on which to build a new theory. It will make it possible to design more efficient materials, with critical temperatures closer to room temperature.
CNRS
Researchers at the National Laboratory for Pulsed Magnetic Fields2, working together with researchers at Sherbrooke, have observed 'quantum oscillations', thanks to their experience in working with intense magnetic fields. They subjected their samples to a magnetic field of as much as 62 teslas (a million times stronger than the Earth's magnetic field), at very low temperatures (between 1.5 K and 4.2 K). The magnetic field destroys the superconducting state, and the sample, now in a normal state, shows an oscillation of its electrical resistance as a function of the magnetic field. Such an oscillation is characteristic of metals: it means that, in the samples that were studied, the electrons behaved in the same way as in ordinary metals.
The researchers will be able to use this discovery, which has been eagerly awaited for 20 years, to improve their understanding of critical high-temperature superconductivity, which until now had resisted all attempts at modeling it. The discovery has been effective in sorting out the many theories which had emerged to explain the phenomenon, and provides a firm foundation on which to build a new theory. It will make it possible to design more efficient materials, with critical temperatures closer to room temperature.
CNRS
Superconductivity News and Current Superconductivity Events RSSGalaxy Zoo -- an Internet superstar
Since Galaxy Zoo's launch in July 2007, some 150,000 members of the public, inspired by the opportunity to be the first to see and classify a galaxy, have helped professional astronomers via this on-line mass-participation project to carry out real scientific research.
Scientists reveal effects of quantum 'traffic jam' in high-temperature superconductors
Scientists at the U.S. Department of Energy's Brookhaven National Laboratory, in collaboration with colleagues at Cornell University, Tokyo University, the University of California, Berkeley, and the University of Colorado, have uncovered the first experimental evidence for why the transition temperature of high-temperature superconductors -- the temperature at which these materials carry electrical current with no resistance -- cannot simply be elevated by increasing the electrons' binding energy.
Creating unconventional metals
The semiconductor silicon and the ferromagnet iron are the basis for much of mankind's technology, used in everything from computers to electric motors. In this week's issue of the journal Nature (August 21st) an international group of scientists, including academic and industrial researchers from the UK, USA and Lesotho, report that they have combined these elements with a small amount of another common metal, manganese, to create a new material which is neither a magnet nor an ordinary semiconductor.
New theory for latest high-temperature superconductors
Physicists from Rice and Rutgers universities have published a new theory that explains some of the complex electronic and magnetic properties of iron "pnictides." In a series of startling discoveries this spring, pnictides were shown to superconduct at relatively high temperatures. The surprising discoveries created a great deal of excitement in the condensed matter physics community, which has been scrambling to better understand and document the unexpected results.
Exotic Materials Using Neptunium, Plutonium Provide Insight into Superconductivity
Physicists at Rutgers and Columbia universities have gained new insight into the origins of superconductivity - a property of metals where electrical resistance vanishes - by studying exotic chemical compounds that contain neptunium and plutonium.
Room temperature superconductivity
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.
UBC physicists develop 'impossible' technique to study and develop superconductors
A team of University of British Columbia researchers has developed a technique that controls the number of electrons on the surface of high-temperature superconductors, a procedure considered impossible for the past two decades.
New superconductors present new mysteries, possibilities
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.
Powerful superconductor is in a class all its own
Superconductivity has perplexed, astounded and inspired scientists ever since it was discovered in 1911. Now, in the latest of a century of surprises, researchers at the National High Magnetic Field Laboratory at Florida State University have discovered unusual properties in a novel superconducting material that point to an entirely new kind of superconductor.
New iron-based and copper-oxide high-temperature
In the initial studies of a new class of high-temperature superconductors discovered earlier this year, research at the Commerce Department's National Institute of Standards and Technology (NIST) has revealed that new iron-based superconductors share similar unusual magnetic properties with previously known superconducting copper-oxide materials.
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