# Is it necessary for Cooper pair of electrons have opposite spin?

In Cooper pair, is there an essential condition on spin of electrons forming pair? Also explain the reason behind it. And what is the charge on them.

• The projection $m_\ell$ of the orbital angular momentum quantum number $\ell$ applies to the system with angular momentum, not to each particle in the system; it doesn't make sense to talk about the $m$ for "each electron." (This is different from the atomic case, where we sometimes forget that the nucleus is involved.) Also a Cooper pair of electrons with $\ell=1$ must have $S=1$, in order for the entire wavefunction to be antisymmetric, in analogy to the protons in orthohydrogen and parahydrogen. I don't know whether the $\ell=1$ pairs are involved in superconductivity or not. – rob May 15 '17 at 16:35