Adiabatic quantum pump in the presence of external ac voltages

TL;DR

This paper studies how external ac voltages influence quantum pumps, revealing a new interference effect that modifies the pump and rectification currents, requiring Floquet scattering matrix analysis beyond the adiabatic approximation.

Contribution

It introduces a novel interference term in the adiabatic dc current of quantum pumps under external ac voltages, extending the theoretical framework beyond frozen scattering matrices.

Findings

Identification of a third interference contribution to the dc current.

Renormalization of quantum pump and rectification effects due to interference.

Analysis of instantaneous currents in nonstationary scattering processes.

Abstract

We investigate a quantum pump which in addition to its dynamic pump parameters is subject to oscillating external potentials applied to the contacts of the sample. Of interest is the rectification of the ac currents flowing through the mesoscopic scatterer and their interplay with the quantum pump effect. We calculate the adiabatic dc current arising under the simultaneous action of both the quantum pump effect and classical rectification. In addition to two known terms we find a third novel contribution which arises from the interference of the ac currents generated by the external potentials and the ac currents generated by the pump. The interference contribution renormalizes both the quantum pump effect and the ac rectification effect. Analysis of this interference effect requires a calculation of the Floquet scattering matrix beyond the adiabatic approximation based on the frozen scattering matrix alone. The results permit us to find the instantaneous current. In addition to the current generated by the oscillating potentials, and the ac current due to the variation of the charge of the frozen scatterer, there is a third contribution which represents the ac currents generated by an oscillating scatterer. We argue that the resulting pump effect can be viewed as a quantum rectification of the instantaneous ac currents generated by the oscillating scatterer. These instantaneous currents are an intrinsic property of a nonstationary scattering process.