Extended Peierls-Hubbard Model for One-Dimensional N-Sites N-Electrons System. II. Effect of Fluctuation, Optical and Magnetic Excitations

Abstract

A one-dimensional many-electron system with site-diagonal electron-phonon coupling, intra- and inter-site electron-electron (e-e) repulsions is studied within the RPA for electrons and in the adiabatic limit for phonons, so as to clarify effects of fluctuation on the phase diagram of the ground state within the mean field theory (MFT), and also on various excitations therefrom. Energies of bound electron-hole (e-h) pairs in the MFT energy-gap such as magnon and charge-transfer (CT) excitons are calculated together with the ground-state energy-gain due to their virtual excitations. The resultant new phase diagram is such that the SDW phase erodes the CDW region given by the MFT, because of the magnon excitation. It is shown that the inter-site e-e repulsion always gives a stable singlet CT exciton that dominates the optical property of the CDW.