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In solid-state physics, the free electron model is a quantum mechanical model for the behaviour of charge carriers in a metallic solid. It was developed in 1927, [ 1 ] principally by Arnold Sommerfeld , who combined the classical Drude model with quantum mechanical Fermi–Dirac statistics and hence it is also known as the Drude–Sommerfeld ...
Electrical conduction of metals is a well-known phenomenon and is attributed to the free conduction electrons, which can be measured as sketched in the figure. The current density j is observed to be proportional to the applied electric field and follows Ohm's law where the prefactor is the specific electrical conductivity .
In this case, the carrier density (in this context, also called the free electron density) can be estimated by: [5] n = N A Z ρ m m a {\displaystyle n={\frac {N_{\text{A}}Z\rho _{m}}{m_{a}}}} Where N A {\displaystyle N_{\text{A}}} is the Avogadro constant , Z is the number of valence electrons , ρ m {\displaystyle \rho _{m}} is the density of ...
Free carrier concentration is the concentration of free carriers in a doped semiconductor. It is similar to the carrier concentration in a metal and for the purposes of calculating currents or drift velocities can be used in the same way. Free carriers are electrons that have been introduced into the conduction band (valence band) by doping ...
In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states.
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In a simplified picture of a solid, thermal conduction occurs by two mechanisms: 1) the migration of free electrons and 2) lattice vibrations . The first mechanism dominates in pure metals and the second in non-metallic solids. In liquids, by contrast, the precise microscopic mechanisms of thermal conduction are poorly understood. [32]
A Connecticut boy is among four children all born with severe childhood blindness who gained “life-changing improvements” to their vision after an experimental trial of gene therapy. Jace was ...