The Nature of the Cooper Pair - University of Liverpool

Let the difference in k be ∆k. The phase at ρ for each sine
function is kρ. Since this difference is is π between the
maximum and minimum k, so
∆k.ρ = π.
To express in terms of E F , we use
E = p2
.
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The small change approximation gives
∆E = p∆p
.
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At the Fermi energy, and for an energy change ∆E equal to ∆,
we have
∆ = p F ∆p
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Superconductivity 23
= pF .�∆k
.
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