Single particle versus collective electronic excitations

  • Philip B. Allen
Conference paper
Part of the Lecture Notes in Physics book series (LNP, volume 477)


As a first approximation, a metal can be modelled as an electron gas. A non-interacting electron gas has a continuous spectrum of electron-hole pair excitations. At each wavevector Q with |Q| less than the maximum Fermi surface spanning vector (2k F ) there is a continuous set of electron-hole pair states, with a maximum energy but no gap (the minimum energy is zero.) Once the Coulomb interaction is taken into account, a new collective mode, the plasmon, is built from the electron-hole pair spectrum. The plasmon captures most of the spectral weight in the scattering cross-section, yet the particle-hole pairs remain practically unchanged, as can be seen from the success of the Landau Fermi-liquid picture. This article explores how even an isolated electron-hole pair in non-interacting approximation is a form of charge density wave excitation, and how the Coulomb interaction totally alters the charge properties, without affecting many other properties of the electron-hole pairs.


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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Philip B. Allen
    • 1
  1. 1.Department of PhysicsSUNYStony BrookUSA

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