Time-dependent quantum current for independent electrons driven under nonperiodic conditions

This is the authors' abstract. We don't add key points for this paper.

An expression for the computation of the current in phase-coherent devices driven under arbitrarily time-dependent conditions is presented. The approach is developed for independent electrons in the time domain within a first-quantization formalism. The time-dependent current is computed by generalizing the Ramo-Shockley theorem to quantum systems. It is shown that the time-dependent conductance is not proportional to the quantum transmission coefficient, but to a parameter named the quantum current coefficient. As a test, it is proved that the present approach leads to the well-known Landauer model when static potentials are considered. As a simple numerical example, coherent quantum pumping is studied and applications for nanoscale solid-state field-effect transistors are predicted.