OPTICAL PROPERTIES OF AN ELECTRON GAS - FURTHER STUDIES OF A NONLOCAL DESCRIPTION

Our previous studies of the optical properties of an electron gas for which the surface scattering is specular have been extended. It is argued that to treat the quantum-mechanical effects appearing at large wave vectors properly, the nonlocal dielectric functions which appear in the expressions for the surface impedance should be finite-electron-lifetime generalizations of the Lindhard dielectric functions rather than those resulting from the Boltzmann equation. The striking anomalous absorption, due to plasmon excitation, occurring above the plasma frequency is emphasized in the discussion of the semi-infinite gas. For the case of a slab, the thickness dependence of the processes characterizing the optical properties is discussed. Electron-gas parameters representing both K and Al were used in the calculations, as were both types of dielectric functions mentioned above. A comparison of the present theory with some alternative theories, particularly that of Melnyk and Harrison, is presented. © 1969 The American Physical Society.