Nonlinear I-V characteristics of a mesoscopic conductor

We present a general theoretical formulation, based on nonequilibrium Green's functions, for nonlinear dc transport in multiprobe mesoscopic conductors. The theory is gauge invariant and is useful for the predictions of current-voltage characteristics and the nonequilibrium charge pileups inside the conductor. We have provided a detailed comparison between the gauge invariant scattering matrix theory and our theory. We have also given several examples where the I-V curve can be obtained analytically. The effects of exchange and correlation have been considered explicitly. (C) 1999 American Institute of Physics. [S0021-8979(99)06121-6].