Effects of quantum lattice fluctuations on the charge-density wave of halogen-bridged mixed-valence transition-metal linear complexes.

Abstract

The effects of quantum lattice fluctuations on the charge-density wave (CDW) of a one-dimensional one-band model for halogen-bridged mixed-valence linear chain complexes are studied by a functional integral approach. Equations for the phonon order parameter and the phonon excitations are derived within a one-loop approximation. They can be applied to any value of the ionic mass ranging from the M=0 (antiadiabatic limit) to the M=\ensuremath{\infty} (adiabatic) limit. We find that the dimerized CDW survives the quantum lattice fluctuations for arbitrarily small electron-lattice coupling. In the case of finite ionic mass, the low-energy properties of the system are governed by the limit of M=0 for a weak-electron-phonon interaction, whereas they are governed by the adiabatic limit (M=\ensuremath{\infty}) for a stronger electron-phonon interaction