Nonlinear conductivity for mesoscopic systems

A generalized Kubo formula for a mesoscopic system is derived describing the conductivity, subject to an (not weak) external electric field, and shown to be expressible in the Landauer–Büttiker form. Using this approach the electrical conductivity of a quantum dot point-contact was expressed as k(2e2/h), where k represents the strength of the mutual interactions. The conditions k<1 and k>1, correspond to “repulsive” and “attractive” interactions with an external electric field, respectively, consistent with recent experimental data.