The Physics of Solids pp 113-147 | Cite as

# The Jellium Model and Metals II: Response to External Perturbations

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## Summary

The response of a solid to an external electric field is characterized by the dielectric function, ε, or the conductivity, σ, or the electric susceptibility, Ҳ_{e}, of the solid. By relatively simple considerations, different expression for ε are obtained, depending mainly on whether \( k \ll \omega / {\upsilon_F} \) or \( k \gg \omega / {\upsilon_F} \). The static conductivity in metals depends on the area of the Fermi surface and the mean free path. The latter is strongly reduced by phonon scattering, and hence, by temperature increase. The presence of an external static magnetic field modifies the conductivity leading to the so-called magnetoresistance and the Hall effect; it induces additional excited states, which give rise to cyclotron, spin, and nuclear magnetic resonances; and it magnetizes the solid. Temperature gradients is another source that drives the material out of thermodynamic equilibrium in the presence or absence of electromagnetic fields.

## Keywords

Magnetic Susceptibility Fermi Surface Dielectric Function External Perturbation Ionic Contribution## Preview

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## Further Reading

- 1.For the symmetry of the kinetic coefficients see Landau & Lifshitz, Statistical Physics [ST35], ±120, pp. 365–368.Google Scholar
- 2.Thermoelectric and thermogalvanometric phenomena are briefly presented in the book by Landau & Lifshitz, Electrodynamics of Continuous Media [E15], ±26, 27, pp. 97–102.Google Scholar
- 3.See also the book by Ashcroft & Mermin, Solid State Physics [SS75], Chaps. 1, 2, and 3, pp. 2–62.Google Scholar
- 4.An advanced study of the dielectric function is given in Many-Body theory books; among them I mention the book by Nozieres [MB58], pp. 45–57, and the book by Fetter and Walecka [MB45], pp. 151–183, as well as the paper by H. Ehrenreich and M.H. Cohen [5.2].Google Scholar