| In this talk I will discuss electronic and excitonic phenomena in low-dimensional molecular aggregates subjected to a linear bias. Disorder is often present in these systems. When correlations in disorder lack characteristic spatial scales (scale-free disorder), the Wannier-Stark ladder reveals in the absorption spectrum of the molecular system. In addition, fluorescence after short-pulse excitation is characterized by an exponential decay at all times. I will also consider Bloch oscillations in the biased Peyrard-Bishop-Holstein model. This model has been previously introduced as an appropriate framework for the description of polaronic effects for charge migration in DNA. I will show that the polaron undergoes coherent oscillations when the electric field is applied along the stacking direction. The frequency of the oscillations is the same as in the rigid lattice (Bloch frequency), provided the carrier-lattice coupling is not large. Increasing the coupling the single peak of the Fourier spectrum splits into side-peaks around the Bloch frequency. Finally, I will advance the most favourable nucleotide sequence for observing Bloch oscillations in single DNA molecules. |
|