Superconductivity + Electron Spin (1 Viewer)

[PopcornPixie]

Hey- i've looked through all the threads about Superconductivity and the BCS theory and haven't found what i'm looking for.
The high school textbooks use the exchange of phonons for explaining superconductivity, but at school, it was taught to us as a phenomenon occuring due to electron spin- a e- of+1/2 and another of-1/2 spin, combining to act as a boson, or something or other like that- passing through the lattice at a low energy state. (well, what we went through was a bit more complex, but i still havent managed to get my head around it). I think my teacher got that explanation from a university text book, but im not entirely certain.
thing is, i havent seen or heard about any spin or anything coming into superconductivity at all. When at tytoring, i asked my tutor if he knew of any "spin" thing, he said he wasnt sure- and none of my friends there know either...

Does anyone know if this, is, indeed correct?
Or should i just stick to the phonon thing (which i dont really understand at all...)

Thanks,
PP

 

[Constip8edSkunk]

this is how i understood it: electrons are normally fermions, and hence abide by the exclusion principle. But in super conductors, through the exchange of a phono, the cooper pairs are effectively bosons with total spins of 0, allowing them to occupy the same low energy state when paired up. the formation of the cooper pairs is caused by an exchange of a phonon between the lattice and the electrons. the phonon itself is 1 unit of the quantised lattice vibration (or in other cases accoustic energy) created when the leading electron distorts the positive lattice as it moves past. this creates a localised region of positive charge and fue to the elaticity of the lattice will propagate along as a wave until being absorbed by the 2nd following electron. ive also remember reading about how the phonon transfers momemtum etc but ive forgotten about that...

to simplify, which is i think what the hsc syllabus is after, 1st elctron moving through attracts the lattice 2wards it, the localised positive charge attracts in turn a 2nd trailing electron. so the 1st elctron indirectly interacts with the 2nd, forming a cooper pair that bypasses collisions and scatterings that is normally associated with resistance during conduction.

 

[Jase]

Dont worry about anything other than phonons, lattice distortions and electron pairs.
in fact you hardly have to worry about phonons.

Bosons are bassically energy carriers, and don't obey the exclusion principle. They ussually have integer ( and quantised) spins. Phonons are bosons that carry quantised vibrations, and have zero spin. The inner workings of phonons and bosons in lattice is way beyond our syllabus.
I think what your teacher was getting at was a little to do with Bose-Einstein condensates and superfluidity. the phonons crowd into the lowest energy state since the exclusion principle doesnt apply to bosons, and superfluid matter is formed.
The electrons of cooper pairs in the BCS theory are attracted to each other by exchanging phonons, and thus causes a superfluid phase.
Don't quote me on this, because im not very sure.

So anyway, just listen to Constipatedskunk.

 

[tempco]

Oh phonons aren't bad enough.. now we got bosons... o___________O

 

[PopcornPixie]

Ok, thanks guys. Big help.!! =)

it's a combination of both... -.-'

*dies*

physics confuses me.
but i love it.
=D

yay for bosons!

Thanks again!