Quantum pumping of electrons by a moving modulated potential

TL;DR

This paper investigates quantum electron pumping in a one-dimensional waveguide with a harmonically modulated potential barrier, analyzing the mechanisms and contributions to charge transport through analytical and numerical methods.

Contribution

It provides a detailed analytical and numerical analysis of quantum pumping mechanisms involving a moving, time-dependent potential barrier in a 1D electron waveguide, highlighting the roles of different scattering contributions.

Findings

Velocity-independent scattering contribution dominates

Doppler-shifted velocity-dependent contribution is generally small

Relative phase controls the dominance of each contribution

Abstract

Quantum pumping holds great potential for future applications in micro- and nanotechnology. Its main feature, dissipationless charge transport, is theoretically possible via several different mechanisms. However, since no unambiguous verification has been demonstrated experimentally, the question of finding a viable mechanism for pumping remains open. Here we study quantum pumping in an one dimensional electron waveguide with a single time-dependent barrier. The quantum pumping of electrons using a potential barrier whose height and position are harmonically varied is analyzed analytically and by numerically solving the time-dependent Schr{\"o}dinger equation. The pumped charge is modeled analytically by including two contributions in linear response theory. First, the scattering of electrons off a potential moving slowly through matter-waves gives a contribution independent of the translational velocity of the potential. Second, Doppler-shifted scattering events give rise to a velocity dependent contribution, which is found in general to be small in comparison with the first one. The relative phase between the oscillations of the height and position is found to be the factor that determines to what extent either contribution is present.