Fermi surface

Summary

The Fermi surface of a metal is the surface in wave-vector space that separates the occupied electron states from the empty ones at zero temperature. It is the level set at the Fermi energy of the band functions of the electronic band structure. Electrons near the Fermi surface carry the low-energy physics of a metal: conduction, heat capacity and the response to magnetic fields. Insulators have no Fermi surface, because their Fermi energy lies in a gap.