Cooper pair
= Cooper pair
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{wiki}
A <Cooper pair> is a correlated pair of <fermions> associated with <superconductivity>. The conventional <BCS ground state> uses opposite-momentum, opposite-spin pair <creation operators> $c_{k\uparrow}^\dagger c_{-k\downarrow}^\dagger$. Their total <momentum> is zero for every relative <momentum> $k$; zero total <momentum> does not restrict $k$ to zero.