  Photo-induced charge separation in nanowires or molecular wires had been
studied in previous experiments and simulations. Most researches deal with the
carrier diffusions with the classical phenomenological models, or the static
energy levels by quantum mechanics calculations. Here we give a dynamic quantum
investigation on the charge separation and dissipation in molecule wires. The
method is based on the time-dependent non-equilibrium Green's function theory.
Polyacetylene chain and poly-phenylene are used as model systems with a
tight-binding Hamiltonian and the wide band limit approximation in this study.
A light pulse with the energy larger than the band gap is radiated on the
system. The evolution and dissipation of the non-equilibrium carriers in the
open nano systems are studied. With an external electric potentials or impurity
atoms, the charge separation is observed. Our calculations show that the
separation behaviors of the electron/hole wave packets are related to the
Coulomb interaction, light intensity and the effective masses of electron/hole
in the molecular wire.
