Although they worked independently of each other, Enrico Fermi and Paul Dirac developed a set of quantum statistics that would revolutionize the field of physics. The statistics helped explain electrons’ behavior in atoms, leading to numerous advances in semiconductor electronics, and they even helped deepen our understanding of the universe.
Their work was recognized recently with an IEEE Milestone. Administered by the IEEE History Center and supported by donors, the IEEE Milestone program recognizes outstanding technical developments around the world.
BUILDING A FOUNDATION
Fermi, a physics professor at the University of Florence, Italy, developed quantum statistics in the early 1920s, describing a distribution of particles over different energy states in systems consisting of particles that obey the Pauli exclusion principle. The principle states that two identical fermions—the electrons, protons, and neutrons that make up an atom of matter—cannot occupy the same energy state at the same time. “Fermion” is a term coined by Dirac, an English physicist.
Meanwhile Dirac, who had recently earned a Ph.D. in quantum mechanics from Cambridge, built upon a theory that Fermi had proposed a few years earlier. The two came to the same conclusion in 1926—which is why the statistics carry both their names.
Fermi-Dirac statistics account for the fact that electrons remain in separate states rather than collapsing into a common state.
The same year the statistics were developed and published, astrophysicist Ralph Fowler cited them to explain the collapse of a star into a white dwarf, a stellar remnant smaller than the original star that has the same electron density. In 1927, theoretical physicist Arnold Sommerfield drew from the Fermi-Dirac statistics to develop his free electron model, which describes the behavior of electrons in a crystal structure of a metallic solid. The model allowed scientists to understand and calculate the electronic band structure of metals and helped pave the way for semiconductor electronics.
Fermi went on to receive the 1938 Nobel Prize in physics for discovering new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons.
A ceremony honoring the Fermi-Dirac statistics was held on 4 December at the University of Florence. A plaque mounted on a wall of its School of Engineering’s main hall reads:
Nobel laureate Enrico Fermi developed the quantum statistics that would be named after him while teaching at the School of Engineering of the University of Florence. The Fermi-Dirac statistics were a fundamental contribution to semiconductor physics and to the development of electronics.