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The Nature of the Cooper Pair - University of Liverpool

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We shall approximately represent <strong>the</strong> attractive potential as a<br />

function that is constant within <strong>the</strong> range l:<br />

where<br />

V (r) =<br />

�<br />

V0 =<br />

−V0 for r < l<br />

0 for r > l<br />

e2<br />

4πɛ0d 2δ.<br />

We have seen that <strong>the</strong> potential only exists within a narrow<br />

tube, so it is not exactly a spherical potential.<br />

However, if two electrons happen to be travelling in opposite<br />

directions and pass very close to each o<strong>the</strong>r, <strong>the</strong>n <strong>the</strong> potential<br />

has <strong>the</strong> same effect as a spherical potential, because <strong>the</strong><br />

electrons do not experience <strong>the</strong> potential outside <strong>of</strong> <strong>the</strong> tube.<br />

Superconductivity 12

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