Composite Bosons: Same State? Fermion Implications

[bsaucer]

If two boson are each composed of two identical fermions in opposite spin states, can the composite bosons occupy the same state? If so wouldn't that cause their fermions to also occupy identical states? (Certainly, they can't occupy four different spin states, can they?)

 

[malawi_glenn]

you mean for instance if He-4 are subject under Bose-Einstein statistics?

 

[Vanadium 50]

I think he means something more like if He-3 forms pairs and is subject to B-E condensation. The answer is "yes". The classic example is Cooper pairs in a superconductor. A second example is superfluid Helium-3.

 

[bsaucer]

Exactly. But isn't there a paradox concerning the individual fermion components occupying identical states?

 

[ZapperZ]

Exactly. But isn't there a paradox concerning the individual fermion components occupying identical states?

No, because these are different states. You can use the Cooper pair as an example. One pair may have (k1, -k1) momentum state, another (k2, -k2), (k3, -k3),... etc.

So each pair still has zero net momentum, but each electron still occupies a unique state. One also needs to remember that these are single-particle states, not 2-particle states, which is what a composite boson (cooper pair) in this case is.

Zz.