LANDAUER APPROACH TO TIME-DEPENDENT TRANSPORT

Based upon the nonequilibrium Green's function formalism, we present a time-dependent Landauer approach to transport through a mesoscopic sy stem under an ac bias voltage. The system is modeled as an elastic sca tterer coupled to large electron reservoirs through perfect conducting wires (leads). The chemical potentials of the reservoirs are driven a part by the bias and, consequently, current flows through the leads fr om one reservoir to another. We examine the nonequilibrium statistical processes of electrons in the leads. The electronic waves are quantiz ed on the basis of orthonormal wave packets moving along the leads, sc attered by the scatterer, and coupled to the reservoirs. The time for an electron to traverse the leads between the source and the drain res ervoirs plus the phase delay time caused by the scatterer is found to be the relevant time scale in the time-dependent transport. The freque ncy dependence of the admittance is fully investigated.