Discrete charge patterns in a holstein-SSH DNA lattice

DNA nonlinear charge transport is addressed in a combined Holstein-Su-Schrieffer-Heeger (HSSH) model. In the adiabatic approximation the dynamics of the system is shown to be governed by a modified discrete nonlinear Schr€odinger (MDNLS) equation, where charge-lattice coupling parameters are obvious. Attention is paid to the effective coupling parameter, v', between charge and internal molecular vibrations, which importantly influences the stability/instability features of the plane wave, solution to the MDNLS equation. Region of instability are remarkably reduced, therefore predicting that increasing v' could progressively quench charge transport. This is confirmed by numerical simulations on the generic HSSH model, where only the charge density is excited and drives the dynamics of the global system. Polarons, as well as longitudinal and transversal nonlinear waves, are obtained and the dependence of charge transport on DNA conformation is discussed. Accordingly, the longtime evolution of the found polarons is studied and we observe a progressive extinction of its temporal evolution as v' increases.