Theory of time‐dependent nonequilibrium transport through a single molecule in a nonorthogonal basis set

Abstract

AbstractA microscopic theory of nonequilibrium electronic transport under time‐dependent bias through a molecule (or quantum dot) embedded between two semi‐infinite metallic electrodes is developed in a nonorthogonal single‐particle basis set using an ab initio formalism of Green's functions. The equilibrium zeroth order electron Green's function and self‐energy are corrected by the corresponding time‐inhomogeneous dynamical contributions derived in the Hartree approximation in a steady‐state linear‐response regime. Nonorthogonality contributes to dynamical response by introducing terms related to the central region‐electrode interface, which appears only in the time‐dependent case. The expression for current is also derived, where a nonorthogonality‐induced dynamical correction gives an additional current that is not present in the orthogonal description. It is shown that the obtained expression for current is gauge‐invariant and demonstrated that the omission of the additional current violates charge conservation. The additional current term vanishes in an orthogonal basis set.