Influence of vibrational modes on the electronic properties of DNA

We investigate the electron (hole) transport through short double-stranded DNA wires in which the electrons are strongly coupled to the specific vibrational modes (vibrons) of the DNA. We analyze the problem starting from a tight-binding model of DNA, with parameters derived from ab initio calculations, and describe the dissipative transport by equation-of-motion techniques. For homogeneous DNA sequences like poly-(guanine-cytosine), we find the transport to be quasiballistic with an effective density of states which is modified by the electron-vibron coupling. At low temperatures, the linear conductance is strongly enhanced, but above the “semiconducting” gap it is much less affected. In contrast, for inhomogeneous (“natural”) sequences, almost all states are strongly localized and transport is dominated by dissipative processes. In this case, a nonlocal electron-vibron coupling influences the conductance in a qualitative and sequence-dependent way.