Localization and shot noise in quantum nanostructures

We present an investigation with a quantum model of shot noise suppression in a series of cascaded barriers, showing that the well-known diffusive limit reported in the literature on the basis of semiclassical models can be achieved only in the presence of a mechanism leading to mode mixing, such as a magnetic field. Without mode mixing, strong localization appears, because the localization length is of the order of the mean free path. These results are consistent with existing experimental data on shot noise in superlattices.