Extended Peierls-Hubbard Model for One-Dimensional N-Sites N-Electrons System. III. Lattice Relaxation after Optical Excitation in CDW

Abstract

The self-trapping of exciton in the CDW phase of one-dimensional many-electron system with short-ranged electron-phonon(e-p) and electron-electron(e-e) interactions is studied by a variational method for exciton and in the adiabatic limit for phonons, so as to clarify its lattice relaxation after the light excitation. The adiabatic potential surface describing the relaxation process is calculated in a wide region of four parameters characterizing the system: the transfer energy of electron T , the e-p coupling energy S , intra- and inter-site e-e repulsive energies U and V . It is shown that in the strong coupling case S ≫2 T , the exciton relaxes to metastable ground states such as an island of SDW phase, and only in the inter-mediate case S ∼2 T it relaxes to a luminescent state localized in the middle of the energy-gap. These results can well explain the luminescence of Wolffram's red salt.