Abstract
The activation energy of a charged soliton pinned by a dopant ion is numerically studied as a function of the dopant concentration. To investigate this problem, use is made of Su-Schrieffer-Heeger's model modified to involve the long-range potential due to the dopants. The dopants are assumed to form a regular lattice even in the low concentration region. The activation energy is defined by the energy difference between a state where the soliton is pinned by a dopant and another state where the soliton locates at a mid point between neighboring dopants. It is shown that the activation energy decreases rapidly with increase of the dopant concentration. It is also found through introducing the effect of the intrachain electron-electron interactions that the soliton width is one of the essential factors in determining the activation energy. The threshold electric field for the depinning of the charged soliton from a dopant is also numerically investigated by dynamical simulations. As expected from the results of the activation energy the threshold field decreases rather rapidly as the concentration increases.
