why do periodic lattices conduct better


by Gobil
Tags: conduct, lattices, periodic
Minich
Minich is offline
#19
Jan14-12, 05:45 PM
P: 91
Quote Quote by Gobil View Post
ok itīs much clearer now thanks.

So if we consider a cold ~0K solid with some crystal defects, there will also be scattering due to the distortions to the wavefunctions from the aperiodic potential. and hence we have some resistance. right?
It can't be right at all!!!

We consider quite common topic: friction!

For electron gas in solids it is named as resistivity.
For helium 3 and 4 it is named as viscosity.

And what do we see?
Even for IMPERFECT solids and for more IMPERFECT liquids there is SUPERCONDUCTIVITY and SUPERFLUIDITY.
There is NO microscopic theory of superfluid helium and of high temperature superconductivity. Some physicists suppose that also BCS theory can't explain some evident EXPERIMENTAL facts (for example Chapnik Kikoin rule, that most of elemental superconductor have pozitive Hall coefficient

).

So the question: what is it friction ( resistivity/viscosity), does not have clear MICROSCOPIC answer till now.
Gobil
Gobil is offline
#20
Jan16-12, 10:34 AM
P: 59
Quote Quote by Minich View Post
It can't be right at all!!!

We consider quite common topic: friction!

For electron gas in solids it is named as resistivity.
For helium 3 and 4 it is named as viscosity.

And what do we see?
Even for IMPERFECT solids and for more IMPERFECT liquids there is SUPERCONDUCTIVITY and SUPERFLUIDITY.
There is NO microscopic theory of superfluid helium and of high temperature superconductivity. Some physicists suppose that also BCS theory can't explain some evident EXPERIMENTAL facts (for example Chapnik Kikoin rule, that most of elemental superconductor have pozitive Hall coefficient

).

So the question: what is it friction ( resistivity/viscosity), does not have clear MICROSCOPIC answer till now.
really? there is no microscopic theory of superconductivity at high temperatures?

Aside from that, I just wanted a kind of idea of the mechanism for light absorption in metals. Particularly at wavelengths above the plasma frequency, I guess there are inter band transitions going on in the conduction bad right? but is the absotpion happening because the light is shaking the electron and the electron is colliding with an imperfection or a phonon, or another electron?
are all these processes happening?
What about at 0K?

thanks!
DrDu
DrDu is offline
#21
Jan17-12, 03:31 AM
Sci Advisor
P: 3,366
Quote Quote by Gobil View Post
really? there is no microscopic theory of superconductivity at high temperatures?


thanks!
Well, I would say that this is quite a particular oppinion of Minich whose paper on that topic we all are awaiting eagerly. Also note that he refers more to superconductivity and superfluidity than to resistance in ordinary metals at higher temperatures.
Minich
Minich is offline
#22
Jan21-12, 03:13 AM
P: 91
Quote Quote by Gobil View Post
really? there is no microscopic theory of superconductivity at high temperatures?
Quote Quote by DrDu View Post
Well, I would say that this is quite a particular oppinion of Minich whose paper on that topic we all are awaiting eagerly.
For current state of microscopic theory of superconductivity at high temperatures i can advice the exellent review of Uchida
Forefront in the Elucidation of the Mechanism of High-Temperature Superconductivity
Shin-ichi Uchida
Department of Physics, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
Received August 4, 2011; accepted September 8, 2011; published online December 7, 2011
It is only 5 pages.
Can be downloaded from
http://jjap.jsap.jp/journal/JJAP-51-1R.html
OR with free YELLOW comments from Minich can be download from
http://frolih.narod.ru/

I don't think that Uchida knows particular opinion of Minich. I think Uchida doesn't know that any "minich" exists :)

The first sentence from abstract:
Quote Quote by Uchida
The mechanism underlying the high-temperature (Tc) superconductivity of copper oxides has remained unelucidated and is one of the most difficult challenges of physics remaining in the 21st century.
So it is not my particular opinion that there is no microscopic theory of superconductivity at high temperatures :)

I will express my particular opinion in another post.
DrDu
DrDu is offline
#23
Jan21-12, 09:04 AM
Sci Advisor
P: 3,366
Yes, I agree that on HTSC we have no theory (or far too many). The sentence I really wante to object was the following:

"So the question: what is it friction ( resistivity/viscosity), does not have clear MICROSCOPIC answer till now."
I would say that we have a good understanding of how resistivity arises in most substances. although there are always substances where special mechanisms are at work that are not well understood.
Minich
Minich is offline
#24
Jan23-12, 05:33 PM
P: 91
Quote Quote by Gobil View Post
I just wanted a kind of idea of the mechanism for light absorption in metals. Particularly at wavelengths above the plasma frequency, I guess there are inter band transitions going on in the conduction bad right? but is the absotpion happening because the light is shaking the electron and the electron is colliding with an imperfection or a phonon, or another electron?
are all these processes happening?
What about at 0K?
thanks!
Let us see a solid at 0K. There is a ground state of a solid. When photon strikes a solid there are many channels to get solid in another (usually excited) state. So do photon's final states and electron(s) final states knocked out from the solid. The final state of the solid is not usually the stationary state of the solid and this state has probabilistic time evolution. Usually the solid is in contacts with many external sources of material world (other solids, electromagnetic fields and so on).

Such contacts as a rule are considered to obey probability rules. It means we name
such behavior as dissipation. For solids usually we have thermalisation processes.

If a solid has impurities the time evolution of the excited solid (as a whole) differs from that of excited solid without imputities.

At 0K we have no phonons.

There are too many possibilities.
Minich
Minich is offline
#25
Jan23-12, 06:07 PM
P: 91
Quote Quote by DrDu View Post
Yes, I agree that on HTSC we have no theory (or far too many). The sentence I really wante to object was the following:

"So the question: what is it friction ( resistivity/viscosity), does not have clear MICROSCOPIC answer till now."
I would say that we have a good understanding of how resistivity arises in most substances. although there are always substances where special mechanisms are at work that are not well understood.
Yes, You are quite right!

P.S.
As for Uchida review
Forefront in the Elucidation of the Mechanism of High-Temperature Superconductivity - Shin-ichi Uchida - COMPREHENSIVE REVIEW
I found, that Uchida has genius intuition.
He expressed one of the method to increase Tc with the help of pseudogap!
I am going to show how it can be achieved in my paper :)
Pseudogap insulator we can force to superconduct combining with overdoped superconductors at T near to pseudogap T* transition.
You can see the paragraph on page 4 near his reference to number 17:
17) S. Ideta, K. Takashima, M. Hashimoto, T. Yoshida, A. Fujimori, H. Anzai,
T. Fujita, Y. Nakashima, A. Ino, M. Arita, H. Namatame, M. Taniguchi, K.
Ono, M. Kubota, D. H. Lu, Z.-X. Shen, K. M. Kojima, and S. Uchida:
Phys. Rev. Lett. 104 (2010) 227001.


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