Quantum size effects on the plasma dispersion in quasi-two-dimensional electron systems

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Abstract
A generalized many-body dielectric theory is developed for studying the collective excitation spectrum in quasi-two-dimensional electron systems in semiconductor inversion and accumulation layers and in semiconductor heterostructures and superlattices. In particular, the coupling between the intrasubband and intersubband collective modes (plasmons) is explicitly retained in the theory. This mode-coupling effect modifies the plasma dispersion relation in these systems and the theory explains the hitherto unexplained phenomenon of a plasmon mass increase at higher wave numbers observed in silicon inversion layers. In a superlattice this mode-coupling effect produces a leading-order modification of the plasma dispersion relation in contrast to other mode-coupling-type phenomena (which are usually higher-order processes away from resonance) giving rise to an improved agreement between the theory and light-scattering experimental results.