Need quick overview on BCS Theory! Rushing on a few dot points on my notes. (1 Viewer)

[peri24]

As above

 

[Leffife]

Okay from the top of my head:

- BCS Theory was developed by Bardeen, Cooper and Schrieffer (hence the name BCS )
- Electrons operate in pairs called Copper Pairs
- Electrons in ordinary materials (non superconductor) will experience resistance, due to collision and other interactions with the lattice of position ions, where electrons lose energy. These interactions give heat to the lattice in packets called phonons.

BUT

- A material which becomes a superconductor the lattice is pretty much forbidden from absorbing electron energy. So the phonons travel through the lattice for a short period of time before being absorbed by a second electron.
- These electrons that exchanged energy are from what I said previously is Cooper Pairs; and through this process the lattice keeps no energy and the electrons essentially keep all their KE.

So now, THEY EXPERIENCE NO RESISTANCE!

 

[cheepy5]

- BCS theory: Bardeen, Cooper and Schrieffer.
- The BCS theory explains superconductivity at temperatures close to absolute zero where lattice vibrations are very low.

- An electron moves through the material and collides with the lattice and loses some of it momentum in the form of vibrations which travel through the lattice via virtual phonon (packet of vibration energy). This phonon collides with a second electron and gives all of its momentum to the second electron. The two electrons taken together have moved through the lattice without any loss of momentum.
These two electrons are called a Cooper's Pair (electrons that travel together)

Cooper's Pair
They are many lattice spacing's apart.
Travel in opposite directions.
Are continually breaking apart and reforming.

 

[someth1ng]

- bcs theory: Bardeen, cooper and schrieffer.
- the bcs theory explains superconductivity at temperatures close to absolute zero where lattice vibrations are very low.

- an electron moves through the material and collides with the lattice and loses some of it momentum in the form of vibrations which travel through the lattice via virtual phonon (packet of vibration energy). This phonon collides with a second electron and gives all of its momentum to the second electron. The two electrons taken together have moved through the lattice without any loss of momentum.
These two electrons are called a cooper's pair (electrons that travel together)

cooper's pair
they are many lattice spacing's apart.
Travel in opposite directions.
Are continually breaking apart and reforming.

1. That is wrong - it explain superconductivity at temperatures below the CRITICAL TEMPERATURE!
2. Electrons lose ENERGY (sure, they lose momentum but that doesn't quite explain why there's a loss of energy).
3. They're not "Cooper's Pairs", they're called "Cooper Pairs".

 

[someth1ng]

Okay from the top of my head:

- BCS Theory was developed by Bardeen, Cooper and Schrieffer (hence the name BCS )
- Electrons operate in pairs called Copper Pairs
- Electrons in ordinary materials (non superconductor) will experience resistance, due to collision and other interactions with the lattice of position ions, where electrons lose energy. These interactions give heat to the lattice in packets called phonons.

BUT

- A material which becomes a superconductor the lattice is pretty much forbidden from absorbing electron energy. So the phonons travel through the lattice for a short period of time before being absorbed by a second electron.
- These electrons that exchanged energy are from what I said previously is Cooper Pairs; and through this process the lattice keeps no energy and the electrons essentially keep all their KE.

So now, THEY EXPERIENCE NO RESISTANCE!

1. Electrons don't always operate in pairs, they only do this when the temperature is below the critical temperature. Below the critical temperature, lattice vibrations contain less energy than the binding energy between a Cooper pair.
2. They're not exactly "forbidden" from absorbing electron energy, it's just that the vibrations are small enough to not interact with the electron pair and the vibrational energy is less than the binding energy (as said above) so that a Cooper pair can stay in contact for long enough.
3. The lattice DOES have energy, it's not like below this magic temperature, the lattice has 0 energy...IT STILL HAS ENERGY! It just doesn't take energy from the electrons.

 

[cheepy5]

1 - yeah fair enough but i should have wrote for type I superconductors which their critical temps are close to absolute zero right?

3 - opps typo

 

[someth1ng]

1 - yeah fair enough but i should have wrote for type I superconductors which their critical temps are close to absolute zero right?

3 - opps typo

Just say below the critical temperature because it then explains ALL superconductors which is the aim of the BCS theory.

 

[nightweaver066]

Just say below the critical temperature because it then explains ALL superconductors which is the aim of the BCS theory.

Isn't it just type I superconductors?

 

[nerdasdasd]

Isn't it just type I superconductors?

Im pretty sure thats for Superconductivity in general.

 

[nightweaver066]

Im pretty sure thats for Superconductivity in general.

I've read somewhere that there is currently no theory to explain superconductivity of type II superconductors.

I'm not so sure so i'll need to google lol

 

[barbernator]

I've read somewhere that there is currently no theory to explain superconductivity of type II superconductors..

there are some wishy-washy suggestions, but yes no definite and concrete theories

 

[nightweaver066]

From wiki:

In 1986, high-temperature superconductivity was discovered (i.e. superconductivity at temperatures considerably above the previous limit of about 30 K; up to about 130 K). It is believed that BCS theory alone cannot explain this phenomenon and that other effects are at play.

 

[nerdasdasd]

Read the last sentence of the second paragraph from jacaranda physics. Looks like the theory does not apple to high temperature superconductors.

 

[someth1ng]

I stand corrected. It also states the same thing in In2Physics as well as Jacaranda.

It is rather interesting but they do believe that something similar occurs for type II superconductors but they are still unsure and is current an area of research.