?? (1 Viewer)

[Mathematician]

why does an electron increase the momentum of positive ions and why would this cause distortion?
this is to do with the BCS theory and superconductivity.

 

[+:: $i[Q]u3 ::+]

I would assume it's due to the electrostatic attraction between the negatively charged electron and the cations that form the crystal lattice... (??)

 

[Mathematician]

...

I know this but i dont understand why this distortion occurs only when an electron passes a positive ion for a superconducting material.
Why not with a normal conductor?

Also do cooper pairs form in normal conductors but break instantly, because isnt a phonon also emitted because of the thermal vibrations in a normal conductor?


And someone explain this

"It is this exchange of phonon energy that keeps the cooper pairs together for much longer periods than normally expected."

And someone explain this too.

"Ordinary metals are good conductors if the electron-lattice interaction is weak. Superconductivity results from a strong interaction between electrons and lattice!"

All these questions are cracking my head and i insist i understand them.


Its night time and im doing an assesment and im not passing this section of the assignment until i get cause im just not happy. LOL


Also forget answering the question in the other post

 

[+:: $i[Q]u3 ::+]

Re: ...

Why not with a normal conductor?

with a normal conductor, the molecular vibrations are just too great because of all of the internal energy (heat) possessed by the atoms. So the pairs just can't form... I guess you can say that they form but "break instantly", but it really is instantaneous...


"It is this exchange of phonon energy that keeps the cooper pairs together for much longer periods than normally expected."

The first electron causes the lattice to distort, and the second electron 'absorbs' this distortion (well.. it's just a concept) as it 'rides the wave' behind the first. You'd think that the electrons would soon repel due to like charge, but the second just continues to absorb the photon energy behind the first, keeping them together.

"Ordinary metals are good conductors if the electron-lattice interaction is weak. Superconductivity results from a strong interaction between electrons and lattice!"

it's a bit of a paradox. in ordinary metals, you want weak electron-lattice interactions so as to avoid collisions resulting in electrical resistance. In superconductors, you need interaction, but they're interactions of a different type. You still don't want collisions, but you need the electrons to distort the lattice in such a way as to allow the formation of cooper pairs. if the electrons can't interact (distort) the lattice, then u have no superconductivity.

is that okay ?

 

[Mathematician]

.....

yeah. I figured it was the way u said for most.

But "but the second just continues to absorb the photon energy behind the first, keeping them together." Knocked something into me


Thanx.

And for this assignment i have when they say discuss the applications of superconductors, do they want the limitations etc ... and advantages in certain areas such as electrical transmittion?

 

[+:: $i[Q]u3 ::+]

the 'limitations' bit is in a separate dot point of its own.
but in ur assignment, when you talk about different applications, it would be a good idea to talk about advantages/limitations; it's very possible they could ask you to describe an application and the benefits of using a superconductor or whatever.

 

[Mathematician]

k thanx

If u're still awake now , can u plz help me find out The author of Physics Context 2 and help me refrence it and excel.
Anyone help lol.

I cant find my Context 2 book anymore maybe its under those flooded papers lol.