Non-Ohmic conductivity in molecular heterostructures

Abstract

A transport model is developed for quasi-one-dimensional molecular multiple-quantum-well-like structures of finite length. The model system consists of a periodic array of cis-trans-polyacetylene segments (superlattice). A non-linear response theory based on a projection operator technique is presented which describes polaronic hopping conduction between localized quantum-well-like states. The formation of space-dependent Stark ladder energies leads to negative differential resistance. In the case of time-dependent electrical fields, both phonon and polaron distributions are treated as time-dependent variables. It will be shown that only in the limit t to infinity and for an appropriate choice of the boundary conditions are the phonons in equilibrium.