Effects of quantum fluctuations of electrons and lattice in doped polyacetylene.

Abstract

The effects of quantum fluctuations of electrons and the lattice on the electronic and lattice structures of doped polyacetylene are studied using the quantum Monte Carlo method. We adopt the model where the on-site (U) and the nearest-neighbor (V) Coulomb interaction terms are added to the Su-Schrieffer-Heeger (SSH) model. In the SSH model, a charged soliton lattice survives quantum fluctuations of the lattice even in the heavily doped regime. However, the magnitude of bond-length alternation in the interface regions between charged solitons is reduced by them. In the model where U>0 and V=0, the ground state becomes a charged soliton lattice in the low doping regime by introducing quantum fluctuations of electrons. The magnitude of the bond-length alternation in the interface regions decreases with increasing doping concentration and becomes almost zero in the heavily doped regime. In the model where U>0 and V>0, a charged soliton lattice survives quantum fluctuations of electrons and the lattice even in the heavily doped regime. However, both the magnitude of the bond-length alternation in the interface regions and the magnitude of the charge-density alternation around the soliton centers are reduced by them. The interaction between charged solitons is significantly weakened by quantum fluctuations of electrons, which results in a significant reduction of the charged soliton formation energy in the heavily doped regime. \textcopyright{} 1996 The American Physical Society.