Dynamical localization in a one-dimensional crystal with an impurity under the action of an electric field

We have solved the problem of dynamical localization in a one-dimensional system with an impurity under the action of a dc field along the single-band tight-binding model. By fixing the impurity potential, we show that characteristic field values can make two on-site energies coincide, enhancing in this way the hopping of carriers between the two sites. The distance between the degenerate sites decreases with increasing field intensity. So for high-field values the sites can be nearest neighbors producing strong oscillations. On the other hand, for weak-field values the two degenerate sites are far apart from each other and, as a result, there is an almost complete localization at the impurity site. We propose a model which allows us to determine the impurity level in a superlattice.