Nonequilibrium Green’s Functions
As we have already seen in the previous chapters, the dynamics of electrons in a semiconductor are the result of the solution of a many-body problem. This is due to the direct Coulomb interaction among carriers and the mediated interaction via phonons. So far, the theoretical approaches that we have developed to tackle this difficult problem have all been based on the density matrix approach and — apart from the χ(n) expansion in the last chapter — on the Hartree-Fock approximation. This mean-field approach, however, neglects important physics such as static and dynamic screening, as well as all kinds of relaxation, correlation, and scattering processes. Before reviewing various aspects of relaxation in Chap. 12, we have to get ready for some more sophisticated mathematics.
KeywordsDyson Equation Time Argument Polarization Propagator Quantum Kinetic Equation Complex Frequency Plane
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