Cooper pairs and Superconductors

[Ben Brain]

How are Cooper pairs being in the same quantum state responsible for superconductivity? Why does them being in the same quantum state matter? Please no complex mathematics, I don't understand that stuff :)

 

[phyzguy]

A simple answer is that electrons, being spin-1/2, are fermions and obey the Pauli exclusion principle. So that no two of them can be in the same quantum state. When the electrons pair up, the pair has spin-1. The pair is then a boson, which means that many of the pairs can be in the same quantum state. In fact, it is energetically more favorable for them to be in the same quantum state. When a macroscopic number of pairs are in the same quantum state, it becomes difficult for one of the pairs to scatter out of this state to a higher energy state, because it has to scatter to a state with an energy far above the common state they are all in. So scattering does not occur. Since electron scattering is the source of resistance in conductors, this means that the electrons flow without resistance.

 

[ZapperZ]

A simple answer is that electrons, being spin-1/2, are fermions and obey the Pauli exclusion principle. So that no two of them can be in the same quantum state. When the electrons pair up, the pair has spin-1.

Just be aware that triplet-spin state superconductors are rather rare. Most of the superconductors are singlet-spin state, i.e. total spin of 0.

Zz.

 

[phyzguy]

Just be aware that triplet-spin state superconductors are rather rare. Most of the superconductors are singlet-spin state, i.e. total spin of 0.
Zz.

Thanks for the clarification. So @Ben Brain, ZapperZ is saying that I should have said, "When the electrons pair up, the pair has spin-0". Spin-0 is still even spin, so still a boson, so everything else I said still applies.