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Can anyone tell me how impurity in superconductors changes the Tc?

  1. Aug 31, 2009 #1
    I've search plenty of papers,but I still got no idea about this.Can anyone give me some clues?

    Thanks in advance.
     
  2. jcsd
  3. Aug 31, 2009 #2
    Hi there,

    Without being an expert in the field, superconductivity comes from the fact that electrons move more freely than in a conventional conductor. If you add some impurities in this material, you change the potential of electrons to move freely, by having variation in the lattice.

    Like I said, this is really not my field. Cheers
     
  4. Aug 31, 2009 #3
    Staying with conventional superconductors: non-magnetic impurities don't do much, and can in fact raise things like the critical field/current. Magnetic impurities tend to cause problems, and can destroy the superconductivity entirely.
     
  5. Sep 12, 2009 #4
    For example: experiment for ordinary metals (1/2,... filled zone)

    Since 1930 years Kikoin-Kitaygorodski-Chapnick empirical rule is known:
    Almost 90-95% superconductors are hole-like (Hall coefficient just above Tc is positive)
    See diagram
    tcvshall.gif

    at http://physics.ucsd.edu/~jorge/bcs.html

    See more about Kitaygorodski-Chapnick empirical rule at
    "[URL [Broken] theory of superconductivity: the world’s largest Madoff scheme?
    J. E. Hirsch
    Department of Physics, University of California, San Diego
    La Jolla, CA 92093-0319[/URL]


    If impuruties make hole effective mass more in value (while Fermi momentum is constant), than Tc will be more in value (as a rule!!!).

    But in ordinary metal impurities in some cases can change even the sign of effective mass! And in that case superconductivity may be destroyed completely.

    Electron and hole conductivities compete in most metals, so it is hard to predict exactly Tc change.

    In HTSC picture is more complex.
     

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    Last edited by a moderator: May 4, 2017
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