Classical mesoscopic effect in the resistance of point-contacts

The mesoscopic effect of the point-contact conductance dependence on spatial distribution of the impurities is theoretically studied. It is shown that the resistanceR dependence on the diameterd is determined not only by the electron mean free path,l i, but also by the average distance between the impurities. In the case of two types of impurities with different concentrations the mesoscopic effect is predicted for the dirty point-contact (d≫l i) due to the scattering on specific (e.g. magnetic) impurities with low concentration. Such contacts were numerically modeled for random distributions of the two types of impurities.