Theory of nonlinear transport in narrow ballistic constrictions

We present quantum-mechanical model calculations of nonlinear transport in narrow ballistic constrictions. We calculate the current and differential conductance g as functions of the applied voltage V₀ and the electron Fermi energy EF. Nonlinear effects in g smooth out transmission resonances and shift and degrade the quantized ballistic conductance plateaus. Contrary to previous claims, we find that g does not develop additional plateaus between those quantized at 2ne²/h. At high V₀ the current saturates at values strongly dependent on EF. .AE