Equation of motion approach to non-adiabatic quantum charge pumping

TL;DR

This paper employs an equation of motion approach to numerically analyze non-adiabatic quantum charge pumping in a one-dimensional system, exploring effects of various parameters on charge transfer and current dynamics.

Contribution

It introduces a versatile numerical method that captures full time-dependent charge and energy currents, extending analysis beyond adiabatic and weak pumping regimes.

Findings

Charge pumping persists against substantial bias.

Asymmetry in currents between leads under strong pumping.

Method aligns with Floquet and adiabatic theories where applicable.

Abstract

We use the equations of motion of non-interacting electrons in a one-dimensional system to numerically study different aspects of charge pumping. We study the effects of the pumping frequency, amplitude, band filling and finite bias on the charge pumped per cycle, and the Fourier transforms of the charge and energy currents in the leads. Our method works for all values of parameters, and gives the complete time-dependences of the current and charge at any site of the system. Our results agree with Floquet and adiabatic scattering theory where these are applicable, and provides support for a mechanism proposed elsewhere for charge pumping by a traveling potential wave. For non-adiabatic and strong pumping, the charge and energy currents are found to have a marked asymmetry between the two leads, and pumping can work even against a substantial bias.