Thomas–Fermi screening

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Thomas–Fermi screening

Dbpedia

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Thomas–Fermi screening is a theoretical approach to calculate the effects of electric field screening by electrons in a solid. It is a special case of the more general Lindhard theory; in particular, Thomas–Fermi screening is the limit of the Lindhard formula when the wavevector (the reciprocal of the length-scale of interest) is much smaller than the fermi wavevector, i.e. the long-distance limit. It is named after Llewellyn Thomas and Enrico Fermi. The Thomas–Fermi wavevector (in Gaussian-cgs units) is where μ is the chemical potential (Fermi level), n is the electron concentration and e is the elementary charge. Under many circumstances, including semiconductors that are not too heavily doped, n ∝ eμ / kBT, where kB is Boltzmann constant and T is temperature. In this case, i.e. 1/k0 is given by the familiar formula for Debye length. In the opposite extreme, in the low-temperature limit T = 0,electrons behave as quantum particles (fermions). Such an approximation is valid for metals at room temperature, and the Thomas–Fermi screening wavevector kTF given in atomic units is If we restore the electron mass and the Planck constant , the screening wavevector in Gaussian units is . For more details and discussion, including the one-dimensional and two-dimensional cases, see the article on Lindhard theory.

Wikipedia Inglés http://en.wikipedia.org/wiki/Thomas–Fermi_screening