Formulation of a New Theory for Optical Response and Exciton Effects in Insulating States Coming from Strong Electron-Phonon and Inter-Electron Interactions

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We formulate a new theory for optical response of many-electron systems in insulating statescoming from strong electron-plaonon (e-ph) and electron-electron (e-e) interactions. The e-jchcoupling and the short range part of' e-e repulsion are reduced into a time-dependent one-bodyHamiltonian by the path-integral. While, the long range part of e-e reptulsion is taken intoaccovnnt straightly, as a perturbation to this time-dependent Harniltonian. To evaluate higherorder terzns of this perturbation, we have extended the Bloch-De Dominicis theorezn, so that itcan be used even in the cases where an unperturbud one-body Hamiltonian is tinae-dependent, aswell as in the conventional time-independent cases. Using this theorem, we have fornaulated theoptical response, wherein the long range part results in exciton effects or particle-hole attractionsas a final-state interaction of the optical transition. Another path-integral is also formulated, inwhich the short and long range parts are treated on an equal footing.
社団法人日本物理学会の論文
1996-07-15