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This speed is known as the Fermi velocity. Only when the temperature exceeds the related Fermi temperature , do the particles begin to move significantly faster than at absolute zero. The Fermi energy is an important concept in the solid state physics of metals and superconductors .
In condensed matter physics, the Fermi surface is the surface in reciprocal space which separates occupied electron states from unoccupied electron states at zero temperature. [1] The shape of the Fermi surface is derived from the periodicity and symmetry of the crystalline lattice and from the occupation of electronic energy bands.
Taking the classical velocity distribution of an ideal gas or the velocity distribution of a Fermi gas only changes the results related to the speed of the electrons. [Ashcroft & Mermin 3] Mainly, the free electron model and the Drude model predict the same DC electrical conductivity σ for Ohm's law, that is [Ashcroft & Mermin 4]
The drift velocity deals with the average velocity of a particle, such as an electron, due to an electric field. In general, an electron will propagate randomly in a conductor at the Fermi velocity. [5] Free electrons in a conductor follow a random path. Without the presence of an electric field, the electrons have no net velocity.
A result is the Fermi–Dirac distribution of particles over these states where no two particles can occupy the same state, which has a considerable effect on the properties of the system. Fermi–Dirac statistics is most commonly applied to electrons, a type of fermion with spin 1/2.
The work function W for a given surface is defined by the difference [1] =, where −e is the charge of an electron, ϕ is the electrostatic potential in the vacuum nearby the surface, and E F is the Fermi level (electrochemical potential of electrons) inside the material.
Here v F ≈ 10 6 m/s (0.003 c) is the Fermi velocity in graphene, which replaces the velocity of light in the Dirac theory; is the vector of the Pauli matrices; () is the two-component wave function of the electrons and E is their energy. [2]
The Fermi velocity can easily be derived from the Fermi energy via the non-relativistic kinetic energy equation. In thin films, however, the film thickness can be smaller than the predicted mean free path, making surface scattering much more noticeable, effectively increasing the resistivity. Electron mobility through a medium with dimensions ...