Fermi Energy

The Fermi energy is a concept in quantum mechanics usually referring to the energy of the highest occupied quantum state in a system of fermions at absolute zero temperature.

Confusingly, the term "Fermi energy" is often used to describe a different but closely related concept, the Fermi level (also called chemical potential). The Fermi energy and Fermi level are the same at absolute zero, but differ at other temperatures, as described below.