How do phonons contribute to the formation of Cooper pairs in superconductors?

[Forestman]

I know that in a superconductor you have what is known as cooper pairs, which are two electrons paired together by the transfer of phonons. And I know that the phonons are quantized vibrations in the crystal lattice. But I still don't quite understand how the phonons hold the cooper pairs together. I am sure that I could understand it if I did some more reading off of the Internet, but I bet that you guys could explain it a lot better. Anyway, if anyone could help me with this I would greatly appreciate it. I am not studying to be a physicist, I am just a layman. But I have a very strong interest in science and math, and I wish to understand everything about these two subjects that I possibly can.

 

[genneth]

The essential point is that the ions move slower than the electrons. Due to the exclusion principle, we only need to concern ourselves with electrons at the Fermi surface, which all have very high momentum and velocity. Ions, when displaced, will move back, but much slower. Now imagine an electron comes by, and its charge pushes an ion out of place. The electron then immediately goes away, but the ion hasn't moved back yet. There is effectively a charged void, which can attract another electron. This way, you set up an effective interaction between electrons. Specifically, you set up an attractive region which is at the same space but displaced in time.

 

[Forestman]

Thanks genneth.

 

[marcusl]

It may be helpful to know that the electrons in a pair are not physically bound together (don't think of the two oxygen atoms in an O2 molecule, for instance). The electrons in a Cooper pair actually have opposite momenta.