Electron energy loss in simple metals and semiconductors

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Abstract
In this review article, the frequency and wave-vector dependent macroscopic dielectric function εM(q, ω), which determines the energy loss function and in the limit q →0 the optical properties, is calculated from the microscopic dielectric matrix in the random phase approximation. The effect of the crystal potential is included by second order perturbation theory within the nearly free electron pseudopotential theory. The theory is applied to investigate the influence of periodic potential on the plasmon lineshape in simple metals and in semiconductors and comparison is made with experiment. In an attempt to explain remaining discrepancies between theory and experiment, various other effects are investigated based mostly on theories in the literature. These effects arise from many-body effects beyond the RPA, from the presence of phonons and from the polarizable core electrons.