Hi, I am trying to understand the formation of Copper pairs in a superconductor. However, 2 major explainations I found in the internet: 1, Cooper pairs are formed by emitting and receiving phonons between 2 electrons. 2, another explaination is, when an electron drifting between the lattice, the vicinity lattice will be attracted slightly toward to that electron, and increase the charge density in that area, hence another electron will be attracted to the area and become a Copper pair with the 1st electron. which one is correct?? And, why the momentums of the electrons must be "equal and oppsite" to form a Cooper pair? Thanks a lot for your help!!