Quantum pumping in graphene nanoribbons at resonant transmission

TL;DR

This paper investigates adiabatic quantum charge pumping in graphene nanoribbons with different edge types, revealing how resonance structures influence electron transfer directions and quantities in the resonant transmission regime.

Contribution

It provides a numerical analysis of quantum pumping in armchair and zigzag graphene nanoribbons, highlighting the effects of zero-conductance resonances on charge transfer.

Findings

Armchair ribbons pump one electron per cycle along the resonance line.

Zigzag ribbons exhibit multiple resonance segments, each pumping a single electron.

Direction of pumped current varies with the resonance segment encircled by the pumping contour.

Abstract

Adiabatic quantum charge pumping in graphene nanoribbon double barrier structures with armchair and zigzag edges in the resonant transmission regime is analyzed. Using recursive Green's function method we numerically calculate the pumped charge for pumping contours encircling a resonance. We find that for armchair ribbons the whole resonance line contributes to the pumping of a single electron (ignoring double spin degeneracy) per cycle through the device. The case of zigzag ribbons is more interesting due to zero-conductance resonances. These resonances separate the whole resonance line into several parts, each of which corresponds to the pumping of a single electron through the device. Moreover, in contrast to armchair ribbons, one electron can be pumped from the left lead to the right one or backwards. The current direction depends on the particular part of the resonance line encircled by the pumping contour.