Cooper Pairs (1 Viewer)

[eX-Bhai]

I understand how cooper pairs are formed, but how exactly do the "binding" of electrons, or cooper pairs allow for a smooth path across the crystal lattice? Like wouldnt these cooper pairs (or having two negatively charged electrons side by side which causes a greater 'negative' force) attract the positive nuclei towards it? This is where I'm kinda getting confused. If anyone could explain and clarify this, it would be much appreciated. Thanks in advanced =)

 

[alcalder]

From what I can gather, the first electron distorts the crystal lattice, causing a positive trough. A second electron is then attracted by the momentary increase in positiveness in that region and follows on behind.

Think of it like this. Imagine you have a big rubber trampoline and on it is a rubber ball. You roll a heavy ball across the trampoline that causes a trough. The rubber ball is attracted to the momentary trough and follows in the wake of the other ball.

Not a great analogy, but that is kind of what is happening.

After the first electron (or bigger ball) has passed by, pulling the other one in its wake, the crystal lattice (or trampoline) springs back into shape.

 

[eX-Bhai]

But if the greater 'positiveness' attracts another electron, how will the electron pass through the crystal lattice? Wouldn't the springing back of the crystal lattice cause the original electron to remain stationary (since the attraction force between the negative electron and the positive nuclei would distort or interupt with the velocity or the electron's path through the lattice), resulting in a self-perpetuating cycle (where the lattice would distort and return back to its original form and so on)?

 

[alcalder]

But if the greater 'positiveness' attracts another electron, how will the electron pass through the crystal lattice? Wouldn't the springing back of the crystal lattice cause the original electron to remain stationary (since the attraction force between the negative electron and the positive nuclei would distort or interupt with the velocity or the electron's path through the lattice), resulting in a self-perpetuating cycle (where the lattice would distort and return back to its original form and so on)?

Remember, this is happening under the influene of a potential difference, so electrons are travelling through the crystal lattice anyway. This just explains how they travel more easily.

Indeed if we had a ball moving across a trampoline that had no forward momentum or force moving it forward, once the trampoline distorted it would want to remain stationary. But since, it has the forward momentum/force on it, the ball continues to move. This ball just pulls another one in its wake.

Thus the current gets through the superconductor crystal more easily.

 

[eX-Bhai]

Heh, thanks for explaining it - I'm still don't think ive grasped the concept yet, but yeh - ill ask my teacher tomorrow. Thanks again, much appreciated =)

 

[helper]

The distortion that is attracting the second in the cooper pair is not at the same physical position as the first. The distortion (phonon) vibrates through the lattice causing the attraction of the second electron that may be a number of atoms away.

 

[eX-Bhai]

ohh okay, i think i get it now - thanks for that =)