New Insights into Many-Body and Correlation Effects in Semiconductors

Linear properties of a solid, consisting of 10 sup (22) -10 sup (23) particles/cm sup 3 interacting through infinite-range Coulomb interactions, are well described by the concept of quasi-particles first introduced be Landau. But interactions between quasi-particles, important in all dense systems, are not well understood. Studies over the past decade have shown that, in contrast to atomic systems, Coulomb correlations dominate the nonlinear response of semiconductors. New insights into the nature of many-body interactions and Coulomb correlations provided by these studies are important not only for semiconductors but for all condensed matter systems. We present a broad overview of these results and their implications.