Physics:Quantum Fermi–Dirac statistics
Fermi–Dirac statistics is a Book II topic in the Quantum Collection. Fermi–Dirac statistics describe the occupation of quantum states by identical fermions. They apply to particles with half-integer spin, including electrons, neutrinos, quarks, and composite fermions such as many atoms and nuclei.[1] Fermi-Dirac statistics limit each available one-particle quantum state to one identical fermion. This rule explains electron shells, the structure of metals and semiconductors, Fermi surfaces, and degeneracy pressure in compact stars. The distribution becomes especially important at low temperature or high density, where quantum indistinguishability dominates thermal randomness.
Description
Fermions obey the Pauli exclusion principle: no two identical fermions may occupy the same quantum state. For a system in thermal equilibrium, the average occupation of a one-particle state with energy is given by the Fermi-Dirac distribution:[2]
where is the chemical potential, is the Boltzmann constant, and is temperature.
Physical meaning
At absolute zero, states below the Fermi energy are filled and states above it are empty. At nonzero temperature the boundary is smoothed, but the exclusion principle still limits each available state to one fermion of a given quantum state.
This statistical rule explains the structure of electron shells in atoms[3], the behavior of electrons in metals and semiconductors, degeneracy pressure in white dwarfs and neutron stars, and the existence of Fermi surfaces in condensed matter systems.
Historical names
- Enrico Fermi developed the statistical treatment of particles obeying the exclusion principle.
- Paul Dirac independently developed the same statistics in quantum theory.
- Wolfgang Pauli formulated the exclusion principle on which the statistics depends.
See also
Table of contents (84 articles)
Index
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References
- ↑ Dirac, Paul A. M. (1926). "On the Theory of Quantum Mechanics". Proceedings of the Royal Society A 112 (762): 661-677. doi:10.1098/rspa.1926.0133.
- ↑ Fermi, Enrico (1926). "Sulla quantizzazione del gas perfetto monoatomico". Rendiconti Lincei 3: 145-149.
- ↑ Sommerfeld, Arnold (1927). "Zur Elektronentheorie der Metalle". Naturwissenschaften 15 (41): 824-832. doi:10.1007/BF01505083.
