# Intuitive explanation for the existence of an energy gap in superconductors

In 2012 there was a nice answer explaining basic superconductivity. It ends with the sentence:

The trouble is you're now going to ask for an intuitive description of why the electron correlations open a gap in the energy spectrum, and I can't think of any way to give you such a description. Sorry :-(

Can anyone please follow up with an intuitive explanation of the energy gap in super conductors? In theory it can be derived from the BCS theory -- but this is not, what I would call intuitive ;)

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What do you mean more precisely with "energy gap" in SC? – Ignacio Vergara Kausel Apr 9 '15 at 8:54
Something like this: nature.com/nature/journal/v418/n6899/images/418733a-f1.2.jpg – bernd Apr 9 '15 at 9:04

To destroy such a pair and produce free electrons you need to invest a minimum of energy, which is this energy gap $\Delta$. This produces an excitation (2 free electrons), remember that SC is the ground state of the system.