Analysis of linear and nonlinear conductivity of plasma-like systems on   the basis of the Fokker-Planck equation
  The problems of high linear conductivity in an electric field, as well as nonlinear conductivity, are considered for plasma-like systems.   First, we recall several observations of nonlinear fast charge transport in dusty plasma, molecular chains, lattices, conducting polymers and semiconductor layers. Exploring the role of noise we introduce the generalized Fokker-Planck equation.   Second, one-dimensional models are considered on the basis of the Fokker-Planck equation with active and passive velocity-dependent friction including an external electrical field. On this basis it is possible to find the linear and nonlinear conductivities for electrons and other charged particles in a homogeneous external field. It is shown that the velocity dependence of the friction coefficient can lead to an essential increase of the electron average velocity and the corresponding conductivity in comparison with the usual model of constant friction, which is described by the Drude-type conductivity. Applications including novel forms of controlled charge transfer and non-Ohmic conductance are discussed. 
S. A. Trigger, W. Ebeling, G. J. F. van Heijst, D. Litinski
physics.plasm-ph