# Sorry but I gotta ask

1. Oct 13, 2005

### Jonny_trigonometry

In an He atom, can the spin up and spin down electrons form a cooper pair? Can the vacuum be thought of as a superconductor?

2. Oct 13, 2005

### lalbatros

No clear answer possible since it is only on the analogy level.
He cooper pair:
In the He atom, the pair of electrons might be seen as a boson. This is similar to a cooper pair.
Both electron have a correlated (entangled) state. Similar too.
Cooper pair have long-range coherence, spanning much more than the inter-atomic distance in the supraconductor. This is different from He, where the coherence is within the atomic radius.
Vacuum as supraconductor
The resistivity of vacuum is zero: there is no dissipation for electrons flowing in vacuum. This is similar.
However, the properties of a supraconductor are the properties of a material. This is not similar, since vacuum is not a material.
Moreover, supraconductivity results from collective behaviour in the material. For the vacuum there is no 'behaviour' explaining its conductivity, it is more the 'absence of behaviour': no friction.

3. Oct 14, 2005

### Jonny_trigonometry

yeah, the vacuum doesn't have any material, just fields. The only reason why a superconductor lets electrons flow without resistance is because they don't collide with the lattice atoms. The field configuration in the SC allows the electrons to have a stable path unobstructed by lattice atoms. I'm not sure where I'm going with this, besides trying to understand superconductivity. Is this the right interpretation of how superconductivity works in a material?

(this part is really stupid, take with a grain of salt)
Is there anything to the resonant frequency of lattice antoms and the debroglie freq of an electron at a specific speed? Do electrons in a high temp SC move faster on average than electrons in a low temp SC, or can they move just as slow as in a low temp SC? Do all the atoms of an SC naturally and automattically resonate at the same freq?

4. Oct 14, 2005

### ZapperZ

Staff Emeritus
No, because in a superconductor, the charge carrier has "long range phase coherence". This means that all the charge carriers settle into a single quantum state, and everyone one of them are "in phase" with each other. You do not have this with electrons moving in a vacuum such as what we have in a particle accelerators. In that case, these electrons are not in phase coherence, they have properties such as emittance and space-charge, etc. that destroy any possibility of long-range coherence.

Zz.

5. Oct 14, 2005

### Jonny_trigonometry

hmm, this is beyond my knowledge. Thanks for the new terms, I'll see if I'm able to understand them.

6. Oct 18, 2005

### Jonny_trigonometry

How far can a virtual photon travel when emmitted from a proton? given that they can only last as long as is dictated by the energy-time uncertainty relation, they have a max distance they can travel right? Of course, assuming that the electric field surrounding the proton is quantized into photons (if I'm interpreting QFT correctly).

Last edited: Oct 18, 2005