What Are Electron Pairs and How Do They Form?

[tarunjot]

I had this lecture today! but everything went over!
How the electrons form those pairs and some more light over it please!

 

[ZapperZ]

I had this lecture today! but everything went over!
How the electrons form those pairs and some more light over it please!

Try this:

http://www.ornl.gov/info/reports/m/ornlm3063r1/pt3.html

Zz.

 

[tarunjot]

Thanks a ton sir. Those figures really made things easy! ;)

 

[marlon]

Try this:

http://www.ornl.gov/info/reports/m/ornlm3063r1/pt3.html

Zz.

Great text, though i don't quite get the content of this extract : " and flux is allowed to penetrate the superconductor through cores known as vortices. Currents swirling around the normal cores generate magnetic fields parallel to the applied field. These tiny magnetic moments repel each other and move to arrange themselves in an orderly array known as a fluxon lattice."

So basically, the extern magnetic flux can penetrate the superconductive specimen to some extent but what exactly are these CORES ? What exactly is the mechanism that describes this penetration. Is this just the generation of magnetic moments due to polarization of charges due to the penetrating extern B-field ?

regards

marlon

 

[marlon]

anyone has a clue...or do i need to start googling again ?

marlon

 

[inha]

Well by quick googling, textbook browsing and searching arxiv it seems that the vortices are the quantized penetrating flux lines. Along the flux lines the density of the Cooper pairs falls to zero and a boundary between the superconducting and normal phase is formed. When the length scale where there is variation in the Cooper pair density around the boundary is smaller than the length scale at which the extern field penetrates the material it's more energtically favourable for the material to break into superconducting and normal regions.

Now someone with more knowledge please give me an intellectual beating. I have a feeling that the paragraph above is filled with horrible errors and inaccuracies.

 

[Gokul43201]

This is simply (as inha said above) what minimizes the free energy of the system. Above a certain field, it is energetically cheaper to make little tubes of normal material within the SC that each allow a flux quantum through than to exclude the field entirely. The density of lines is determined by the applied field, so that the average flux density through the SC is equal to B outside (far away).

Marlon, you could look up the original paper by Abrikosov, if you can read Russian.

It is : A. A. Abrikosov, Zh. Eksperim. i. Teor. Fiz, 32, 1442 (1957)

I believe there's a translation at Soviet Phys. - JETP 5, 1174 (1957)

The concept of the fluxoid was first proposed by London. See F. London, Superfluids, vol. I, Wiley, New York (1950), p. 152

There's a nice review article by Tinkham, which I can not find now...will look for it.

 

[Gokul43201]

PS : I'd wait for Zz to amble by...he's a little busy planning his next vacation, I think