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Nonlinearity-induced Anomalous Charge Diffusion in a DNA ModelG. KalosakasTUE-3O28Materials Science Department, University of Patras, GR-26504 Rio, Greecegeorgek@upatras.grWe present results on the diffusive motion of a charge propagating along a double stranded DNA, when thecharge carrier interacts with the nonlinear stretching dynamics of base-pairs [1]. The anharmonicity of base-pairdynamics is described by the Peyrard-Bishop-Dauxois model [2], which accurately reproduces a number ofexperimental results related to base-pair openings [3-6]. The coupled charge-lattice system is studied in theframework of semiclassical dynamical equations [7], where charge motion is described quantum-mechanicallyand the lattice component classically. Temperature is represented using a Langevin description of the latticedynamics [8,9].Signatures of anomalous diffusive properties are found at relatively high temperatures. A sublinear diffusionand a plateau appear before the standard long-time diffusion, during the evolution of charge's mean squareddisplacement (Fig.1), and also a significant degree of heterogeneity is exhibited among individual trajectories(Fig. 2) [10]. The higher the temperature, the more evident is the anomalous charge's relaxation.Fig. 1. Anomalous diffusion (sublinear diffusion and a plateau) at relatively hightemperatures. Evolution of charge’s mean squared displacement for different temperatures.The results are thermally averaged over 200 realizations.These properties are connected with the existence of vibrational hot-spots (breather or multibreatherexcitations [11-13]) in the lattice component of the system. Such a long-lived localized states are present due tothe nonlinearity and their lifetimes are orders of magnitude longer than characteristic time scales of thecorresponding normal modes [11,14]. These hot-spots result in an enhanced confinement of the charge, at themicroscopic level [8,9].Macroscopic charge transport parameters are strongly affected in this case, as it can be exemplified by thesignificant suppression of the diffusion coefficient D [10,15]. The variation of D with temperature follows astretched exponential law. These results are contrasted with the corresponding ones in the case of a linearizedlattice, in the absence of breathers (Fig. 3).Such an anomalous diffusion of a charge which is coupled to a thermalized lattice, may be also relevant inother low-dimensional soft materials with strong anharmonicities, like for example in conducting polymers.74