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In physics, some particles (for example electrons) follow the Pauli exclusion principle – i.e. that no two particles may occupy the same state at the same time. When a number of electrons are put into a system, electrons will occupy higher energy levels when the lower ones are filled up. Loosely speaking, the Fermi energy is the energy of the highest occupied state at zero temperature. It is given the symbol EF. Fermi energy is a concept which finds application in semiconductor theory and device design.The Fermi surface is the surface in the momentum space where the total excitation energy equals the Fermi energy. It can have a non-trivial topology. Roughly speaking, it divides the occupied states from the empty ones.
Fermi energy was named after Enrico Fermi who, with Paul Dirac, derived the Fermi-Dirac statistics. These statistics allow one to predict the behaviour of large numbers of electrons under certain circumstances, especially in solids. The equations of quantum mechanics would otherwise be too hard to solve in such situations.
The Fermi energy of a three-dimensional, non-interacting, non-relativistic Fermi gas (or free electron gas) is related to the chemical potential by the equation
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where εF is the Fermi energy, k is the Boltzmann constant and T is temperature. Hence, the chemical potential is approximately equal to the Fermi energy at temperatures of much less than the characteristic Fermi temperature EF/k. The characteristic temperature is on the order of 105 KThe kelvin (symbol: K is the SI unit of temperature, and is one of the seven SI base units. It is defined by two facts: zero kelvin is absolute zero (when molecular motion stops), and one kelvin is the fraction 1/273. 16 of the thermodynamic temperature o for a metal, hence at room temperature (300K), the Fermi energy and chemical potential are essentially equivalent. This is significant since it is the chemical potential, not the Fermi energy, which appears in Fermi-Dirac statistics.
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solid state physics, semiconductors, electrical engineeringElectrical engineering is an engineering discipline that deals with the study and application of electricity and electromagnetism. Its practitioners are called electrical engineer s. Electrical engineering is a broad field that encompasses many subfields., electronicsElectronics is the study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The pure study of such devices is considered as a bra, statistical mechanicsStatistical mechanics is the application of statistics, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force. It provides a fr, thermodynamicsThermodynamics is the physics of energy, heat, work, entropy and the spontaneity of processes. Thermodynamics is closely related to statistical mechanics from which many thermodynamic relationships can be derived. While dealing with processes in which sys
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