Question

What is the energy gap in band theory? Compare its size in superconductors, conductors, semiconductors, and insulators.

Short answer

Energy gap is the energy difference in between the valance band and the conduction band of the material.

On the basis of energy gap, the increasing order for the materials is:

Superconductors<Conductors<Semiconductors<Insulators

Step-by-step solution

Energy gap in the band theory

As per the band theory, the energy gap is the difference in the energy level of the conduction band and the valance band. This is the case with conductors, semiconductors and insulators.

In the superconductors, as the current is carried by bosons, the energy gap is the difference in the energies of the electrons in the cooper pair near the Fermi energy level.

Comparison of the band gaps

On comparing the band gaps, the energy gap increases as,

Superconductors<Conductors<Semiconductors<Insulators