Intrinsic nonlinear conductance of mesoscopic conductors

The conductance of a mesoscopic conductor is shown to be a sensitive function of the dc voltage on the system. In the low-temperature limit, changing the potential drop across the system by an amount on the order of the level spacing of the system is sufficient to change the conductance by ${\mathit{e}}^2$/h. Arguments based on scattering theory, analogy with the universal conductance fluctuation, and numerical evidence are presented to support our conclusion. Our theory is in good agreement with the results of harmonic-generation experiments.