Quantum states and optical responses of low-dimensional electron–hole systems

Abstract

Quantum states and their optical responses of low-dimensional electron–hole systems inphotoexcited semiconductors and/or metals are reviewed from a theoretical viewpoint,stressing the electron–hole Coulomb interaction, the excitonic effects, the Fermi-surfaceeffects and the dimensionality. Recent progress of theoretical studies is stressed andimportant problems to be solved are introduced. We cover not only single-exciton problemsbut also few-exciton and many-exciton problems, including electron–hole plasma situations.Dimensionality of the Wannier exciton is clarified in terms of its linear and nonlinearresponses. We also discuss a biexciton system, exciton bosonization technique, high-densitydegenerate electron–hole systems, gas–liquid phase separation in an excited state andthe Fermi-edge singularity due to a Mahan exciton in a low-dimensional metal.