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What is the current highest temperature super conductor?

  1. Jul 18, 2010 #1
    I've read that as of now the highest Tc is 254 K ((Tl4Ba)Ba2Ca2Cu7O13+). Is that correct? My source is superconductors.org, can that site be trusted? It seems like the record has been rapidly increasing in the past decade. If there are any experts out there, do you think we will reach a Tc of 294 K anytime soon?
     
  2. jcsd
  3. Jul 18, 2010 #2
    No , the substance you are reporting has not been verified independently. Many claims have been made for many temperatures, unless someone verifies it, I'd be very skeptical. The record for normal pressure is around 138K maybe a few degrees more under very high pressure. There has been no progress in raising the critical temperature for the last 10 years. We will probably need a new material class, and those are normally found by accident. Because theory is not very good in predicting these things. But the main thing to keep in mind is, that to transport appreciable current you must cool a superconductor far below the critical temperature. Room temperature is not enough 330K or so would be what one would aim for so it can be used without cooling.
     
  4. Jul 18, 2010 #3
    I wouldn't say room-temperature is the only superconductor that is viable. I think a material which can be mass-produced and has good workability that can operate under liquid nitrogen would have many many applications.
     
  5. Jul 18, 2010 #4
    I thought that was only for certain types of superconductors like the cuprate ones. I read that some of the lower Tc superconductors suddenly transition to zero resistance at Tc. Is that correct?
     
  6. Jul 18, 2010 #5

    ZapperZ

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    Er... ALL superconductors make an abrupt drop in resistivity at Tc, not just the cuprates. That is a significant property of a superconductor - a "phase transition".

    The point that is being made here is that, for most practical application it isn't just enough that Tc is high. That isn't the issue anymore because we have already many compounds that becomes superconducting above LN2 temperature. The issue here is that (i) the current density for many of these material is rather small to carry any appreciable current for long-distance transport (ii) the flux migration can cause significant hindrance to transport (iii) quenching on certain parts of the material due to Hc1 being rather low, etc...

    To overcome these effects, one still has to go to a considerably lower temperatures than just getting to below Tc.

    Zz.
     
  7. Jul 19, 2010 #6
    Thanks ZapperZ, that's some useful info. So what are the BEST known superconductors based on these additional factors? (by best I mean most useful to practical applications)
     
  8. Nov 19, 2010 #7
    MgB2 and graphite

    May be the most mass produced superconductor in future: graphite?

    Let us see:
    MgB2 and graphite are very similar in electronic structure
    see the book: Electronic structure: basic theory and practical methods / Richard M. Martin. 2004
    4 relevant pages from this book are here (only for teaching use):
    http://love.minich.ru/s/p068.djvu
    http://love.minich.ru/s/p069.djvu
    http://love.minich.ru/s/p070.djvu
    http://love.minich.ru/s/p071.djvu
    There is a pic from page 48 (p069.djvu)
    [URL]http://love.minich.ru/s/mgb2-graphite-electron-band.jpg[/URL]
    MgB2 to the left, graphite to the right (in red by Minich hand)

    We know experimental Chapnic-Kikoin rule, that materials with negative low temperature Hall coefficient as a rule are not superconductors:
    http://iopscience.iop.org/0305-4608/13/5/011

    [URL]http://www-physics.ucsd.edu/~jorge/tcvshall.gif[/URL]
    Negative Hall coeff elements to the left.

    As we can see MgB2 and graphite also obey Chapnik-Kikoin rule. But!!!

    It may be very usefull to experiment with doped graphite so as to get Fermi level cross (a little bit) sigma graphite band, to get sigma band in graphite partially unoccupied and get hole conductivity (positive Hall coefficient). Graphite can absorb many gases and liquids.
    Sigma band is stronger in graphite, than in MgB2 so we can hope to get Tc more than 39K.

    It would be very interesting to test the Chapnik-Kikoin rule for "doped" graphite. May be we have a chance get from unsuperconductive graphite superconductive one.
     
    Last edited by a moderator: Apr 25, 2017
  9. Nov 20, 2010 #8
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