Authors: S. Tornow, R. Bulla, F.B. Anders, and G. Zwicknagl
Journal:
arXiv:0911.5161
We investigate the transfer characteristics of multiple charges in a DNA base-pair dimer using a model Hamiltonian approach. It comprises different Coulomb matrix elements which where calculated recently by Starikov [E. B. Starikov, Phil. Mag. Lett. {\bf 83}, 699 (2003)] as well as the dissipative environment which is modeled by a bosonic bath. In the nuclear tunneling regime we employ the Numerical Renormalization Group method whereas in the thermal activation regime a scheme of kinetic equations and Marcus rates is used to calculate the time-dependent population probabilities. We find that the mobility of two excess charges depends strongly on the Coulomb-matrix elements which differ for the different base pairs. Starting with two electrons on the donor, the Coulomb matrix elements determine, if, e.g, both electrons are self-trapped, transferred as a pair or only one of the electrons is transferred. The latter can be even activation-less when the difference of the on-site and inter-site Coulomb matrix element is equal to the reorganization energy which is the case in a GC-GC dimer. Whereas two excess electrons in AT-AT, dependent on the temperature and spectral function of the environment, are either self-trapped or are oscillating as a pair.