A time-dependent approach to electron pumping in open quantum systems

TL;DR

This paper introduces a versatile time-dependent computational method for analyzing electron transport in quantum pump devices, capable of handling various driving conditions and incorporating electron interactions.

Contribution

It presents a novel real-time propagation scheme that unifies different driving scenarios and integrates with density functional theory to include electron-electron interactions.

Findings

The method accurately simulates electron dynamics under monochromatic, polychromatic, and nonperiodic drivings.

It provides a general expression for pumped current using Floquet theory and Green's functions.

The approach offers a way to surpass limitations of traditional Floquet-based schemes.

Abstract

We propose a time-dependent approach to investigate the motion of electrons in quantum pump device configurations. The occupied one-particle states are propagated in real time and used to calculate the local electron density and current. An advantage of the present computational scheme is that the same computational effort is required to simulate monochromatic, polychromatic and nonperiodic drivings. Furthermore, initial state dependence and history effects are naturally accounted for. This approach can also be embedded in the framework of time-dependent density functional theory to include electron-electron interactions. In the special case of periodic drivings we combine the Floquet theory with nonequilibrium Green's functions and obtain a general expression for the pumped current in terms of inelastic transmission probabilities. This latter result is used for benchmarking our propagation scheme in the long-time limit. Finally, we discuss the limitations of Floquet-based schemes and suggest our approach as a possible way to go beyond them.