Inter-molecular Electronic Transfer
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1207-N09-05
Inter-Molecular Electronic Transfer Karel Král1 and Miroslav Menšík2 1 Institute of Physics, Academy of Sciences of Czech Republic, v.v.i., Na Slovance 2, 18221 Prague, Czech Republic 2 Institute of Macromolecular Chemistry, Academy of Sciences of Czech Republic, v.v.i., Heyrovský sq. 2, 16206 Prague 6, Czech Republic ABSTRACT The transport of electric charge is an important phenomenon in the systems like interacting quantum dots and molecules, and in polymers, including DNA molecules. We expect that in these nanostructure systems the key role is played by the interaction of the charge carriers with the optical phonons. We show the role of the multiple scattering of the charge carriers on the optical phonons in the inter-molecular transfer. The charge carrier transport based on this mechanism will be discussed theoretically and compared with the earlier experimental results on the charge transport in molecular Donor-Acceptor charge transfer crystals and also in other systems. In order to treat theoretically the electron transfer between two zero-dimensional nanostructures, we will use the model of two interacting quantum dots coupled by the electron inter-dot tunneling mechanism. A connection with the popular Marcus semiclassical charge transfer theory between molecules is also shown. We will use the nonequilibrium quantum electronic transport theory based on the nonequilibrium Green's functions. INTRODUCTION Among the molecular condensed matter structures there are at least two kinds of material, in which the material is basically one-dimensional and in which we observe an electronic transport along the one-dimensional stacks of molecules. The two cases we wish to pay attention to are first of all the DNA molecules [1], in which charge carriers are expected to move from one molecular base to the neighboring one. Another example may be served by the Donor-Acceptor (DA) molecular crystal, in which one-dimensional stacks of alternating donor and acceptor molecules form stacks of molecules [2]. In both these kinds of material the one-dimensional stacks remind the stacks of books in shelves. The energies of the single-electron states in the individual molecules (let us call a base of a DNA molecule also simply a molecule) may vary relatively strongly from molecule to molecule in the stack. From this reason we can speak about a rather strong static diagonal disorder influencing seriously the electronic motion along the molecular stacks in these systems. Because of the well known arguments [3] the charge carriers should be localized in such systems, with only elastic scattering of charge carriers, and the electric conductivity should be zero. Because experiments show effects due to a charge carriers moving along the stacks, we thus ascribe this charge carrier motion to be due to mechanisms which allow the charge carriers to be transferred irreversibly from one molecule of the stack to another one in the stack via an inelastic scattering of electrons. We shall treat theoretically this charge carrier motion alo
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