SC in CuO Layers: Evidence & Experiments

[nbo10]

What kinda experiments prodive evidence that SC resides in the CuO layers? Off hand I can't think of how any experiments that I'm familiar with could distinguish if the CuO or another plane where SC. Thanks

 

[ZapperZ]

What kinda experiments prodive evidence that SC resides in the CuO layers? Off hand I can't think of how any experiments that I'm familiar with could distinguish if the CuO or another plane where SC. Thanks

First of all, in some camps, this is still a controversial idea. But the community as a whole are convinced that the CuO planes are where all the actions are taking place. There is no single one convincing proof that this is occurring. Rather, it comes from several different observations.

1. We establish that the superconductor is highly 2D. This can be seen from the huge anisotropy in the resistivity of the material, where the c-axis resistivity can be several orders of magnitude greater than the ab-plane resistivity.

2. ARPES measurements see the opening of the anisotropic superconducting gap consistent with where the band crosses the Fermi surface on the CuO plane. Furthermore, we see the split-bands effects from the bonding-antibonding bands in high-Tc compounds with a dual-layer CuO planes per unit cell.

3. Tc seems to increase when there's more CuO planes per unit cell.

4. But the most convincing evidence is the fact that we can practically change the compounds in between the CuO planes and still superconductivity. This seems to indicate that the planes in between the CuO planes are simply "spacers" that act as charge reservoir and plays no significant role in superconductivity.

Zz.

 

[nbo10]

2. ARPES measurements see the opening of the anisotropic superconducting gap consistent with where the band crosses the Fermi surface on the CuO plane. Furthermore, we see the split-bands effects from the bonding-antibonding bands in high-Tc compounds with a dual-layer CuO planes per unit cell.
Zz.

Thanks for the response ZapperZ. Is ARPES a bulk measurement? Do you have any quick reference on ARPES? If not I can do a literature serach.

ZapperZ, would you mind if I PM a few questions that are HTSC related? Thanks

 

[Gokul43201]

There's a review article by Timusk and Statt that explains ARPES measurements. You can download the pre-print from http://physwww.physics.mcmaster.ca/timusk/.

The pseudogap in high-temperature superconductors: an experimental survey, T. Timusk and B. Statt, Rep. Prog. Phys. 62, 61-122, (1999).

 

[ZapperZ]

Thanks for the response ZapperZ. Is ARPES a bulk measurement? Do you have any quick reference on ARPES? If not I can do a literature serach.

ZapperZ, would you mind if I PM a few questions that are HTSC related? Thanks

I'll be tacky and mention that I have an entry in my Journal on Photoemission:

[10-17-2004 08:40 PM] - Photoemission Spectroscopy

Here are the references in that entry:

"The progress in this experimental technique evolved rather spectacularly after the discovery of the high-Tc superconductors. Having the 2D layers of copper-oxide planes where most of the superconducting effects are thought to occur, these made them a natural candidate to be studied by photoemission, especially using a technique called angle-resolved photoemission. The avatar that I am using came from such an experiment done on a highly overdoped Bi2212, a high-Tc superconductor.

It is imperative to point out that ALL of the theory of photoemission, including those applied in the study of materials that we are now using in modern electronics, make use of ONLY the photon picture of light. There have been NO other alternative formulation of light to account for the experimental observations of photoemission spectroscopies. NONE.

There are two very good reviews of the usage of the photoemission technique on superconductors. The identical technique is also used on other materials.

http://arxiv.org/abs/cond-mat/0209476
http://arxiv.org/abs/cond-mat/0208504 "

You can PM me, but unless it has something to do with private info, I'd rather discuss the physics on here. At the very least, someone with more info, or a more accurate one, can come in and contribute.

Zz.

 

[ZapperZ]

There's a review article by Timusk and Statt that explains ARPES measurements. You can download the pre-print from http://physwww.physics.mcmaster.ca/timusk/.

The pseudogap in high-temperature superconductors: an experimental survey, T. Timusk and B. Statt, Rep. Prog. Phys. 62, 61-122, (1999).

Note that the Timusk paper is more of a survey of the pseudogap state. So this includes a whole bunch of experimental observations, with ARPES being just a part of it. Furthermore, you don't get to see the bilayer split bands in the pseudogap state, since the pseudogap came from the optimally and underdoped compounds. The bilayer split bands (one of the evidence that argues for the CuO planes being responsible for superconductivity) are most apparent in the overdoped regime of the phase diagram. In this regime, there are no discernable pseudogap.

Zz.