GAUGE-INVARIANT NONLINEAR ELECTRIC TRANSPORT IN MESOSCOPIC CONDUCTORS

We use the scattering approach to investigate the nonlinear current-vo ltage characteristics of mesoscopic conductors. We discuss the leading nonlinearity by taking into account the self-consistent nonequilibriu m potential. We emphasize conservation of the overall charge and curre nt and the invariance under a global voltage shift (gauge invariance). As examples, we discuss the rectification coefficient of a quantum po int contact and the nonlinear current-voltage characteristic of a reso nant level in a double-barrier structure.