- #1
mojo0529
- 4
- 0
I've search plenty of papers,but I still got no idea about this.Can anyone give me some clues?
Thanks in advance.
Thanks in advance.
Can anyone tell me how impurity in superconductors changes the Tc?
- Context: Graduate
- Thread starter mojo0529
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- Superconductors
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Discussion Overview
The discussion centers on how impurities in superconductors affect the critical temperature (Tc) of superconductivity. Participants explore various aspects of this relationship, including theoretical implications and experimental observations, without reaching a consensus.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant expresses uncertainty about the effects of impurities on Tc and seeks clarification.
- Another participant suggests that impurities alter the electron mobility in superconductors by changing the lattice potential, although they acknowledge their lack of expertise in the field.
- A different participant notes that non-magnetic impurities typically have minimal impact on superconductivity, while magnetic impurities can severely disrupt it, potentially destroying superconductivity altogether.
- A reference to a study indicates that the transition temperature of amorphous phases is generally lower than that of crystalline phases, suggesting a complex relationship between structure and Tc.
- Discussion includes the Kikoin-Kitaygorodski-Chapnick empirical rule, which posits that most superconductors are hole-like, and mentions that impurities can affect the effective mass of charge carriers, potentially increasing Tc under certain conditions.
- It is noted that in ordinary metals, impurities can sometimes alter the sign of the effective mass, complicating predictions about changes in Tc.
- Participants mention that the situation is more complex in high-temperature superconductors (HTSC), indicating a need for further exploration.
Areas of Agreement / Disagreement
Participants do not reach a consensus on the effects of impurities on Tc, with multiple competing views and uncertainties expressed throughout the discussion.
Contextual Notes
There are limitations in the discussion regarding the assumptions made about the types of impurities and their specific effects on different superconducting materials. The complexity of interactions between electron and hole conductivities is also acknowledged but not fully resolved.
- #2
fatra2
- 475
- 1
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
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
- #3
genneth
- 979
- 2
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.
- #4
Minich
- 86
- 1
For example: experiment for ordinary metals (1/2,... filled zone)
Almost 90-95% superconductors are hole-like (Hall coefficient just above Tc is positive)
See diagram
at http://physics.ucsd.edu/~jorge/bcs.html
See more about Kitaygorodski-Chapnick empirical rule at
"[URL 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.
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
at http://physics.ucsd.edu/~jorge/bcs.html
See more about Kitaygorodski-Chapnick empirical rule at
"[URL 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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