Cooper Pairs

[YYYY]

Could somebody please explain what cooper pairs are? In laymans terms. What effect does this have on the electrons and nuculeus.

Also, do you think it is possible for an element to collapse to 1/2 (or there abouts) its original size?

[Mercedes Benzene]

Hmmmmm.... I'm not really sure how to explain this one.
I suggest you try wikipedia.
You should probably look for "BCS Theory".

Good luck! Sorry I could not be more helpful.

[UncleAl]

Electrons are spin-1/2 fermions. If you dump them into a potential well they stack into non-degenerate energy levels. If you kick one the others don't care. Electrons propagate through conductors down a constant potential gradient with resistive loses as each encounters grief along its path.

Given a third body and low enough background temp, pairs of electrons will couple conjugate momenta to cancel. Cooper pairs are spin-0 boson pseudoparticles. Bosons dumped into a potential well are degenerate at cool enough temps so there is only the base energy level accessible. To kick any of them you must kick all of them out of degeneracy. Cooper pairs propagate through conductors down a constant potential gradient with zero resistive losses unless the conductor goes normal. The ensemble doesn't react to petty grievences.

How cool is cool enough? Depends on the third body and its coupling strength. BCS supercons use phonons - quantized lattice vibrations - that are tens of thosands of times more massive than electrons. It's ping pong balls vs. bowling balls. Ya gotta be hard by absolute zero for random thermal excitations to not swamp Cooper pairing.

Cooper pairing via excitons, quantized electron excitations, is approximately same-mass interaction. The calculated critical temp here is 23,000 kelvins,

William A. Little, Phys. Rev. 134 A1416-A1424 (1964)

Over nearly a half-century there have been nearly 900 references to that paper and NOBODY has made the materials. Talk, talk, talk. Theory without experiment is grandiloquent crap.

[YYYY]

Originally Posted by UncleAl

Electrons are spin-1/2 fermions. If you dump them into a potential well they stack into non-degenerate energy levels. If you kick one the others don't care. Electrons propagate through conductors down a constant potential gradient with resistive loses as each encounters grief along its path.

Given a third body and low enough background temp, pairs of electrons will couple conjugate momenta to cancel. Cooper pairs are spin-0 boson pseudoparticles. Bosons dumped into a potential well are degenerate at cool enough temps so there is only the base energy level accessible. To kick any of them you must kick all of them out of degeneracy. Cooper pairs propagate through conductors down a constant potential gradient with zero resistive losses unless the conductor goes normal. The ensemble doesn't react to petty grievences.

How cool is cool enough? Depends on the third body and its coupling strength. BCS supercons use phonons - quantized lattice vibrations - that are tens of thosands of times more massive than electrons. It's ping pong balls vs. bowling balls. Ya gotta be hard by absolute zero for random thermal excitations to not swamp Cooper pairing.

Cooper pairing via excitons, quantized electron excitations, is approximately same-mass interaction. The calculated critical temp here is 23,000 kelvins,

William A. Little, Phys. Rev. 134 A1416-A1424 (1964)

Over nearly a half-century there have been nearly 900 references to that paper and NOBODY has made the materials. Talk, talk, talk. Theory without experiment is grandiloquent crap.

Thanks for your reply Uncle Al
I am not a chemistry student (only self taught) so I am having a bit of trouble with your vernacular.

Could I start with: Whats a potential well?

[Erasmus00]

To start, there are two types of particles, bosons and fermions. Fermions are spin 1/2 particles, which means they have an intrinsic angular momentum quantized like . Bosons are spin 1 particles, which means they have an intrinsic angular momentum quantized like .

The name spin comes from the idea that it was originally concieved that the particles were spinning like tops.

Now, fermions and bosons have some interesting statistical properties. Fermions don't like to stack on top of each other, so you can't put two fermions in the same state. This is essentially the origin of the Pauli exclusion principle you're probably familar with. Bosons, however, have no problems being in the same state.

Now, we need to ask What is going on in a superconductor? All the current flows as if it has virtually no resistance. How can this be? Well, if all the electrons could condense down into the same state then they would behave like one big electron. This is exactly the behavior we see.

But electrons are fermions. This is a problem? So how can they condense? Cooper figured out that if electrons interact through the crystal lattice they are moving in, they can pair up. Now, two electrons paired together becomes a spin 0 particle (two spin 1/2s). This is a boson, and so our system can condense, and everything works.
-Will

[UncleAl]

Fermions have non-integral spin and Fermi statistics. Boson shave integral spin and Bose-Einstein statistics. Two fermions occupy an energy level - one spin up and one spin down. The fermion rule is that all quantum numbers may not be identical. Cooper pairs have conjugate momenta - spin-zero pseudoparticle, and its components move in opposite directions.

Both of you need a good dose of Google.

[Qfwfq]

Originally Posted by UncleAl

Both of you need a good dose of Google.

Be less arrogant Unc, and if that was meant to include Will I must say that you're mistaken. I found less wrong in his post than in yours, much less.

[sebbysteiny]

Both of you need a good dose of Google.

- Uncle Al

Be less arrogant Unc, and if that was meant to include Will I must say that you're mistaken. I found less wrong in his post than in yours, much less.

whay, hypography forums gets C A T T Y. Nice. And who said learning wasn't a spectators sport?

I'm going to try, in laymans terms, to explain cooper pairs. Good thing too because I found superconductivity a nightmare because there were so many little bits that took me ages to make any sense of, and it's been 2 years since, so I've forgotten most of it and anything but a layman's approach would be a little demanding.

Here goes.

Electrons in a metal lattice have a number of energy states. However, the lowest electron state is when electrons combine together to form cooper pairs.

However, to do this, one electron with a velocity of say +x must pair with an electron with a velocity of say -x to form a spinless boson. However, if one electron is excited up to a higher energy state (note all lower energy states are full of other electrons), then the cooper pair will have to be broken too and normal conductivity resumes.

All it needs is a small number of electrons to be excited from their lowest energy state and all the cooper pairs break apart. Thus, for most superconductors, anything but the very lowest of temparatures (almost absolute 0) will break the cooper pairs appart.

However, there have been developments in materials allowing materials as piping hot as -170 degrees C to still have superconductive properties. However, I don't know if this is due to the same mechanism as BSC theory suggests.

Okay, era of peace is passed. Lets get back to the era of libal and slander.

[YYYY]

Originally Posted by sebbysteiny

whay, hypography forums gets C A T T Y. Nice. And who said learning wasn't a spectators sport?

I'm going to try, in laymans terms, to explain cooper pairs. Good thing too because I found superconductivity a nightmare because there were so many little bits that took me ages to make any sense of, and it's been 2 years since, so I've forgotten most of it and anything but a layman's approach would be a little demanding.

Here goes.

Electrons in a metal lattice have a number of energy states. However, the lowest electron state is when electrons combine together to form cooper pairs.

However, to do this, one electron with a velocity of say +x must pair with an electron with a velocity of say -x to form a spinless boson. However, if one electron is excited up to a higher energy state (note all lower energy states are full of other electrons), then the cooper pair will have to be broken too and normal conductivity resumes.

All it needs is a small number of electrons to be excited from their lowest energy state and all the cooper pairs break apart. Thus, for most superconductors, anything but the very lowest of temparatures (almost absolute 0) will break the cooper pairs appart.

However, there have been developments in materials allowing materials as piping hot as -170 degrees C to still have superconductive properties. However, I don't know if this is due to the same mechanism as BSC theory suggests.

Okay, era of peace is passed. Lets get back to the era of libal and slander.

Thanks for the input everyone.
I understand what you are saying about the unfilled electron shells, I created a spreadsheet detailing this for all the elements.

So under what conditions do cooper pairs form? Are they natural at low temps or do they have to be induced? Could neo magnets be used in anyway to induce cooper pairs?

Cheers
Y

[sebbysteiny]

Again, it's been a while, but Cooper pairs are the lowest energy state that electrons can have while they act as a free electron gas as they do in any conductor. All conductors will quite naturally have superconductive properties if the temparature is low enough.

I personally can't see how magnitism would effect a cooper pair's formation. Perhaps I've forgotten something.