The Energy gap in superconductors

The energy gap in superconductors is the gap between the energy bands which are fully occupied by electrons, and the bands which are fully empty. That Eg is one of the superconductors' properties that don't show in any other materials. The size of the energy band is about 1 eV, which is the required energy to break the band between 2 electrons pairs. At zero temperature, the electrons jump over the energy gap and create holes.