Influence of vibrational modes on the electronic properties of DNA

Abstract

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.