DNA Charge Transfer in an External Field: An Atomistic Approach

We address the problem of charge transfer through DNA-gold junctions from a theoretical and numerical perspective. The geometry and the electronic structure of the DNA fragment is described on an atomistic level making use of an extended Su-Schrieffer-Heeger Hamiltonian. The emerging potential energy surfaces exhibit the characteristics of small polaron formation and can be analyzed to obtain the energy parameters relevant to Marcus' theory of charge transfer and the corresponding interbase hopping rates. At stationarity, the resulting master equations lead to a maximum current of 5 nA per A-DNA double strand upon the application of a potential of +/- 2 V, a value comparable to recent experimental findings. In addition, the overall shape of the I-V curves and their pronounced dependence upon the DNA sequence is reproduced.