Nonlinear Conductance in the Mesoscopic Regime

Fluctuations of the current-voltage (IV) characteristic of a mesoscopic sample are considered. Such a sample can be realized as a junction of two normal metals. The voltage dependence of current is a random function, and the IV-characteristic has a "blades of grass" form on a usual ohmic background. The scale of each "blade" in voltage is of order V_c ~ hbar/τ_fe, where τ_f is the time of flight through the junction and e is the electron charge. The scale in current δI depends on the voltage V and temperature T, and of order (e²/hbar)(VV_c)^1/2, if V gg V_c, T/e. As a result, provided the voltage is sufficiently large, there appear regions of negative differential resistance.