Biased diffusion in anisotropic disordered systems

We investigate a diffusion process into an anisotropic disordered medium in the presence of a bias. The medium is modeled by a two-dimensional square lattice in which the anisotropic disorder is represented by a bond percolation model with different occupation probabilities on each direction. The biased diffusion process is mapped by a random walk with unequal transition probabilities along and against the field (in the [1,1] direction) by performing Monte Carlo simulations. We observe a transition from pure to drift diffusion when the bias reaches a threshold B(c). In order to estimate this B(c), an effective exponentis used to characterize the diffusion process. This B(c) is also compared with another estimation for the critical field.