Self-trapping versus trapping: Application to hole transport in DNA

We address the problem of interplay between self-trapping effects and effects of an external potential, which may be relevant for many physical systems, such as polarons in solids or a Bose-Einstein condensate with attraction. If the potential consists of two different wells, the system initially localized in the shallower well may relax into the deeper well, or may not if stabilized by the self-trapping effect. We show how this picture can be applied to interpret results of recent experiments on electron transfer in the DNA molecule [Giese , Nature 412, 318 (2001)]. The results of our calculations agree well with the experimental findings, giving evidence that hole transport in DNA involves polaronic effects.