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 :)
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.
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.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.