High-Temperature Superconductor Transport

[KRaffi]

I am starting to work with the high temperature superconductor BSCCO (Bi–Sr–Ca–Cu–O). I have read that the carriers of superconducting current is hole pairs. (As opposed to electron-pairs in normal superconductors) I am trying to understand how the transport would work.

If I contact it with gold and I am trying to measure the conductance, how does the interface of the metal/superconductor transport work? Normally, an electron crossing from the metal to the superconductor would carry another electron with it creating a Cooper pair. I feel like you would have some sort of junction. I think I am just confused about the physics of the transport and I don't really know what I am asking. If someone could talk about the transport and the interfaces, it would be much appreciated.

Thanks.

 

[f95toli]

There several issues here.

Firsly, for a normal superconductor (say Al or Nb) the physics is quite straigthforward: you have an NS interfac and you can use a semi-classical semiconductor-type desciption, see e.g. relevant chapter in Tinkham's book which describes this in some detail It might also be worth looking up some papers on Andreev reflection/mirrors.

Secondly, if the contacts are large enough (and they usually are) there the only practical issue that comes into play is the contact resistance, i.e. the resistance is high it tends to mess up your measurements. Properly designed contacts should not exhibit any "interesting" physics.

However, things are of course potentially quite different for BSCCO since it is a layered material and therefore extremely anisotropic. This makes everything much more complicated and the details of what is going on will depend on what you are trying to make contact to (a stack? in-plane?) and what the topmost plane is (the current flows preferentially in-plane). Hence, any "simple" mental picture is not going to be very accurate.
I am pretty sure you should be able to find quite a few papers about this if you have a look around.

 

[KRaffi]

Thanks for the book reference.

So you said current flows preferentially in-plane. Doesn't it also have a preferred direction in the a-b plane? So if I figure out a way to measure the conductance in both a and b directions, I should see a higher resistance in one?

Thanks for your response