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Physicists Induce Superconductivity In Non-Superconducting Materials (phys.org) 46

An anonymous reader quotes a report from Phys.Org: Researchers at the University of Houston have reported a new method for inducing superconductivity in non-superconducting materials, demonstrating a concept proposed decades ago but never proven. The technique can also be used to boost the efficiency of known superconducting materials, suggesting a new way to advance the commercial viability of superconductors, said Paul C.W. Chu, chief scientist at the Texas Center for Superconductivity at UH and corresponding author of a paper describing the work, published Oct. 31 in the Proceedings of the National Academy of Sciences. The research, demonstrating a new method to take advantage of assembled interfaces to induce superconductivity in the non-superconducting compound calcium iron arsenide, offers a new approach to finding superconductors that work at higher temperatures. Superconducting materials conduct electric current without resistance, while traditional transmission materials lose as much as 10 percent of energy between the generating source and the end user. That means superconductors could allow utility companies to provide more electricity without increasing the amount of fuel used to generate electricity. To validate the concept, researchers working in ambient pressure exposed the undoped calcium iron arsenide compound to heat -- 350 degrees Centigrade, considered relatively low temperature for this procedure -- in a process known as annealing. The compound formed two distinct phases, with one phase increasingly converted to the other the longer the sample was annealed. Chu said neither of the two phases was superconducting, but researchers were able to detect superconductivity at the point when the two phases coexist. Although the superconducting critical temperature of the sample produced through the process was still relatively low, Chu said the method used to prove the concept offers a new direction in the search for more efficient, less expensive superconducting materials.

Physicists Induce Superconductivity In Non-Superconducting Materials

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  • by Lisandro ( 799651 ) on Tuesday November 01, 2016 @06:42AM (#53190717)

    Not a physicist by any chance here, but how is this possible? I thought superconductivity was pretty much binary - either you are or you are not.

    • Re: (Score:3, Informative)

      by Anonymous Coward

      Superconductivity is a second order phase change, so yes, it would appear to be binary from the measurement perspective. Traditional LTS superconductors will conduct without loss in all three dimensions as one would expect. The common HTS superconductors the cuperates, actually only super-conduct in 2-d planes. This is one of the reasons that we have had such a difficult time getting practical high current wires and cables out of HTS that even begin to approach their small scale single grain properties.

    • It is binary at a given temperature. For any given temperature the substance either superconducts or does not.
    • by necro81 ( 917438 ) on Tuesday November 01, 2016 @08:33AM (#53190997) Journal
      Although superconductivity is a a binary effect - resistance is either identically zero or some positive value - there are practical limits. The critical temperature is one such limit that could be "boosted" - raising the temperature at which you can get superconductivity.

      Another limitation that could be boosted is the current limit: although superconductors exhibit zero resistance, they cannot conduct infinite amounts of current. Try to move too much current through the material and you'll eventually have the superconductivity suddenly stop.

      A third limitation of superconductors has to do with magnetic strength: a superconductor will stop being a superconductor in a sufficiently high magnetic field. I do not know for certain (I am not a solid-state physicist), but I suspect it is related to the limitations on current density.

      One very practical result of these limitations is that the main magnet of MRI scanners remains quite large. They have gradually been able to increase the strength of the main field - 3 Tesla is pretty standard these days - but the magnets themselves are still really big, have relatively small (claustrophobic) bores, and are cooled using liquid nitrogen. "Boosting" conventional superconductors to be able to handle higher temperatures, higher current densities, and greater magnetic fields would presumably allow MRI's main magnet to be physically smaller, have a larger-diameter bore, be cooled with something other than helium, while maintaining or increasing the field strength.
    • by HiThere ( 15173 )

      Binary? Yes, sort of. But also not. A magnetic field will suppress superconduction, but the further the superconductor is below (i.e., away from) the critical temperature the stronger a field is required to suppress it. There are other similar effects with other properties...one of which is pressure (perhaps depending on the material.)

      P.S.: I'm no physicist either, nor a materials engineer. But I read a lot. To explain superconducting magnets would require a real expert rather than me.

  • by sjbe ( 173966 ) on Tuesday November 01, 2016 @07:07AM (#53190769)

    If it can be used as a superconductor then by definition it is a superconducting material. Just because we didn't know how to do it in a particular material previously is irrelevant.

    • by drinkypoo ( 153816 ) <martin.espinoza@gmail.com> on Tuesday November 01, 2016 @07:10AM (#53190773) Homepage Journal

      If it can be used as a superconductor then by definition it is a superconducting material.

      The material is not superconducting any time other than during phase transition. The only time it's superconducting is when it's not really anything at all. It's doubtful whether we could maintain such a lack of state indefinitely. That pretty much makes it not a superconducting material. It also pretty much means that this approach won't allow us to use it as a superconductor. It might, however, have some kind of ramifications for producing something like displays or memory around the tech.

      • by Anonymous Coward

        Unless it is self regulating.

        The regular problem with cold superconductors is that if they start to get warm you get a positive feedback loop where they get more resistive and even warmer.

        With this material it might be possible to just dump coolant on it. If it gets too cold it will stop being a super conductor and heat itself up until it reaches a temperature where it no longer have losses.

        • by Anonymous Coward

          With this material it might be possible to just dump coolant on it. If it gets too cold it will stop being a super conductor and heat itself up until it reaches a temperature where it no longer have losses.

          And therin lies the problem...if you don't know exactly what the temperature is, you will fluctuate between a superconductive state and a non-superconductive state. Even if you find the proper temperature, maintaining it within required bounds could be problematic. So much so as to make it impractical.

        • I guess you could get a steady state phase transition in metals, but usually annealing is a conversion process.

          It is notable however that they had superconducting at 350C because of this phase transition.

          • by JesseMcDonald ( 536341 ) on Tuesday November 01, 2016 @10:42AM (#53191799) Homepage

            It is notable however that they had superconducting at 350C because of this phase transition.

            They annealed the material at 350C. The superconducting critical temperature of the resulting material was "relatively low", which in this context probably means that it requires cooling with liquid nitrogen or helium. If they had managed to create a superconductor that worked at 350C this would be much bigger news—we still don't know of any materials which superconduct at room temperature, much less a bit above the melting point of lead. The highest-temperature superconductor on record is hydrogen sulfide at 203K (-70C).

            • yeah, I think I read that as the superconducting was *during* the annealing. Not after. Not clear from TFS.

      • The material is not superconducting any time other than during phase transition.

        I'm not a chemist so I would defer to someone who is but...

        As I understand it you are correct but that doesn't make the title make any more sense. Either the material can superconduct or it cannot. All other superconducting materials can only superconduct under specific conditions as well so that's nothing new. The fact that it can only do it during certain phases or phase transitions doesn't change what the material is made of, just how it is structured. Just because something is not entirely solid or

        • by hey! ( 33014 )

          That's like saying it makes no sense to say that by assembling semiconductors into a transistor they can be made to conduct electricity. By your logic if they conduct electricity under any circumstances they must be conductors.

          This is not how humans use language.

          • That's like saying it makes no sense to say that by assembling semiconductors into a transistor they can be made to conduct electricity. By your logic if they conduct electricity under any circumstances they must be conductors.

            It's nothing like that at all because the very term semiconductor clarifies the matter. Semiconductors DO conduct electricity. Just relatively poorly compared with traditional conductors and better than insulators. We've figured out some clever ways to control and selectively enhance their conductivity under certain conditions much like we have found ways to create superconductivity under certain conditions. The taxonomy here is well understood and defined. We don't call things "conductors in non-condu

            • by hey! ( 33014 )

              Well, then by your standards semiconductors are no longer semiconductors because under certain circumstances they act like conductors.

              Language works because the speaker and listener share a common base of knowledge; not because speech conveys pure ontological assertions. You simply cannot explain what a "semiconductor" is to someone who has not been taught the rudiments of the physics behind it, no matter how precise you try to make the terminology.

    • by mark-t ( 151149 )
      Every conductor is a superconducting material at cold enough temperatures. Heck, even *insulators* can be superconductors when you get close enough to absolute zero.

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