Logical switching with the use of bipolarons in conjugated polymers

Considering impurity molecules functioning as switches, the charge transpor t on a single conducting polymer chain is investigated. The dynamics of str uctural bipolaron-type defects in conjugated polymers using a modified tigh t-binding hamiltonian is extended to include the effects of an external ele ctric field and the parameters of the switching molecules are studied. The electric field is used to accelerate charged bipolarons in polymers and it is introduced in terms of a time-dependent vector potential, We use the Par iser-Parr-Pople model combined with the Su-Schrieffer-Heeger model of elect ron-lattice coupling and a Brazovskii-Kirova-type simmetry-breaking interac tion. The process of charge transfer through the sites, and that it works l ike a switch, is analyzed by the numerical resolution of the equations of m otion within the unrestricted Hartree-Fock approximation. The switching cha racter of the parameters of the molecules on the charge transport through t he chain is determined. The energies involved are also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.