Fermion definition in physics

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Fermion Definition in Physics: Fundamental Concepts

What Is a Fermion? Quantum Particle Definition and Properties

In physics, a fermion is a type of particle that follows the Pauli exclusion principle, which means that no two identical fermions can occupy the same quantum state at the same time. This property distinguishes fermions from bosons, which do not have this restriction. Fermions include particles such as electrons, protons, and neutrons, and they are the building blocks of matter in the universe 45.

Pauli Exclusion Principle and Fermi Surface

The Pauli exclusion principle is central to the behavior of fermions. In systems with many fermions, this principle leads to the formation of a Fermi surface at zero temperature, which is a key concept in understanding the electronic properties of metals and other materials. The Fermi surface separates occupied from unoccupied quantum states in momentum space .

Fermions as Particle-Hole Excitations

Fermions can also be described as collections of non-local particle-hole excitations across the Fermi surface. This means that the behavior of a single fermion in a many-body system can be understood in terms of excitations where a particle is removed from one state (a "hole") and placed in another (a "particle"), and these excitations are not limited to low-energy phenomena or specific dimensions .

Mathematical Framework and Quantum Mechanics

The quantum-mechanical description of systems with multiple fermions uses mathematical frameworks that ensure the correct behavior under particle exchange and the exclusion principle. These frameworks allow for the discernment of individual fermions in composite systems, even when the particles are otherwise identical, by using permutation-invariant relations .

Fermion Molecular Dynamics

Fermion molecular dynamics (FMD) is a computational method that models quantum systems using classical equations of motion, but with additional constraints to enforce the Pauli exclusion principle and the Heisenberg uncertainty principle. This approach is used to study atomic and molecular structures and interactions, providing a practical way to simulate systems of many fermions .

Conclusion

In summary, a fermion in physics is a particle that obeys the Pauli exclusion principle, forming the foundation of matter. Its unique quantum properties, such as the creation of a Fermi surface and the ability to be described as particle-hole excitations, are essential for understanding the behavior of complex systems in quantum mechanics and condensed matter physics 145.

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Fermion as a non-local particle-hole excitation

The fermion can be considered as a collection of non-local particle-hole excitations across its Fermi surface, allowing for the calculation of its Green function and Bose-Einstein distribution.

2025·

0citations

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Spectral Theory of the Fermi Polaron

The Fermi polaron system can be characterized using a general mathematical framework, revealing that the polaron and molecule energies are upper bounds to the ground state energy of the system.

2019·

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·M. Griesemer et al.

Fermi Function and Its Applications

The Fermi function, or Woods-Saxon potential, is a well-known potential in nuclear physics, with applications in nuclear and generalized moments, radial Fourier transformation, and related computations.

2023·

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·Asma A. Elahwel et al.

Discerning Fermions

The quantum-mechanical description of composite physical systems with similar fermions can be discerned using permutation-invariant categorical relations, refuting the current dominant view that such systems always conflict with Leibniz's Principle of the Identity of Indiscernibles.

Highly Cited

2008·

144citations

·F. Muller et al.

Fermion molecular dynamics in atomic, molecular, and optical physics

Fermion molecular dynamics (FMD) is a quasi-classical method for treating quantum-mechanical systems, with applications in atomic and molecular structure, ion-atom collisions, stopping powers, formation of antiprotonic atoms, and multiple ionization in strong laser fields.

1998·

26citations

·L. Wilets et al.

The Fermi Level

The Fermi level determines the conductivity, insulator, and semiconductor properties of materials, with its position affecting conductivity, insulator, and semiconductor properties.

2020·

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·B. Cantor

Fermion Models

An algebraic fermion model aims to provide a tractable microscopic description of nuclear phenomena by treating nucleons as fermions and invokes special group symmetries associated with collective behavior.

2020·

5citations

·J. Draayer

Dirac Fermions in Solids: From High-Tc Cuprates and Graphene to Topological Insulators and Weyl Semimetals

Dirac fermions play a crucial role in various electronic systems, from graphene to high-Tc superconductors to topological insulators, with their low-energy properties governed by the same Dirac equation.

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2013·

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·O. Vafek et al.

Observation of three-component fermions in the topological semimetal molybdenum phosphide

Three-component fermions exist in crystalline molybdenum phosphide, offering a platform for studying the interplay between different types of fermions in condensed-matter systems.

Very Rigorous JournalHighly Cited

2017·

247citations

·B. Lv et al.

Verification of universal relations in a strongly interacting Fermi gas.

The Tan relations, which relate microscopic quantities to thermodynamics in strongly interacting fermion systems, have been experimentally confirmed in a strongly interacting gas of fermionic atoms.

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2010·

172citations

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