Superconductors are materials which can conduct electricity with no resistance, which means no loss of power at all over distance. Most superconductors perform at temperatures near absolute zero (0 degrees Kelvin). Zeeya Merali reports in the February 22, 2012, Nature periodical that an iron-based crystal operates as a superconductor when under pressure. When the pressure is increased, the superconducting capacity is lost. When even more pressure is applied, the superconducting quality reappears in the crystal.
The crystal is made of iron selenide, and Liling Sun of the Institute of Physics, Chinese Academy of Sciences in Beijing, has investigated this phenomenon with her colleagues. "Pressure is a way to tune basic electronic and lattice structures by shortening atomic distances, and it can induce a rich variety of phenomena," she says.
Iron selenide acts as a superconductor up to about 30 K, and by increasing pressure with a diamond anvil, the superconductivity ceased as pressure approached 10 gigapascals. But increasing the pressure further, above 11.5 gigapascals caused the crystal to begin superconducting again. At about 12.5 gigapascals, the crystal could superconduct at tempratures up to 48 K, a new record for iron-selenide superconduction.
Practical applications would require that superconducting continue above 77 K (which is the limit for liquid nitrogen; it boils above that temperature), but a Tsinghua University physicist, Qi-Kun Xue, thinks this is possible. With his collegues, he grew an iron-selenide compound o a strontium-titanate substrate and is hoping for "a drastic increase in transition temperature," he said.
Subir Sachdev, a Harvard University physicist, notes that ‘vacancies’ – sites I a crystal that lack any ions – are shuffled about when pressure is applied. These ion-free zones are magnetic but not superconducting. The superconducting zones have no ion vacancies. Sachdev speculates that, "Under high pressures, it looks like something happens to push the magnetic behavior out, and let superconductivity take over."
Sun and her colleagues plan neutron-scattering experiments to show how a sample’s structure changes under pressure in an effort to determine whether vacancy order or changes in magnetism or some other effect is behind the change in superconductivity.
Zeeya Merali writes in Nature:
"The findings may confuse, rather than solve, the long-standing mystery of high-temperature superconductivity, says Andrew Green, a condensed-matter physicist at University College London, UK. He notes that although the first phase of superconductivity in iron selenide, seen at lower pressures, is related to the transition seen in other high temperature superconductors, the re-emergence of superconductivity at higher pressure is probably a new type of phase transition that follows a different mechanism. "This is a very nice result — but I think it raises more questions than it answers."
http://www.nature.com/news/superconductor-breaks-high-temperature-record-1.10081
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Note by the Blog Author
High temperature, particularly room temperature, superconductors could provide a revolution in energy generation, transmission over long distances, and in energy-efficient transportation.
Progress in this area, particularly in breaking boundaries for various substances, is good news in future efficient use of power worldwide.
The crystal is made of iron selenide, and Liling Sun of the Institute of Physics, Chinese Academy of Sciences in Beijing, has investigated this phenomenon with her colleagues. "Pressure is a way to tune basic electronic and lattice structures by shortening atomic distances, and it can induce a rich variety of phenomena," she says.
Iron selenide acts as a superconductor up to about 30 K, and by increasing pressure with a diamond anvil, the superconductivity ceased as pressure approached 10 gigapascals. But increasing the pressure further, above 11.5 gigapascals caused the crystal to begin superconducting again. At about 12.5 gigapascals, the crystal could superconduct at tempratures up to 48 K, a new record for iron-selenide superconduction.
Practical applications would require that superconducting continue above 77 K (which is the limit for liquid nitrogen; it boils above that temperature), but a Tsinghua University physicist, Qi-Kun Xue, thinks this is possible. With his collegues, he grew an iron-selenide compound o a strontium-titanate substrate and is hoping for "a drastic increase in transition temperature," he said.
Subir Sachdev, a Harvard University physicist, notes that ‘vacancies’ – sites I a crystal that lack any ions – are shuffled about when pressure is applied. These ion-free zones are magnetic but not superconducting. The superconducting zones have no ion vacancies. Sachdev speculates that, "Under high pressures, it looks like something happens to push the magnetic behavior out, and let superconductivity take over."
Sun and her colleagues plan neutron-scattering experiments to show how a sample’s structure changes under pressure in an effort to determine whether vacancy order or changes in magnetism or some other effect is behind the change in superconductivity.
Zeeya Merali writes in Nature:
http://www.nature.com/news/superconductor-breaks-high-temperature-record-1.10081
= = = = = = = = = = = = = = = = = = = = = = = = = =
Note by the Blog Author
High temperature, particularly room temperature, superconductors could provide a revolution in energy generation, transmission over long distances, and in energy-efficient transportation.
Progress in this area, particularly in breaking boundaries for various substances, is good news in future efficient use of power worldwide.
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