Time-dependent Landauer-B\"uttiker approach to charge pumping in AC-driven graphene nanoribbons

TL;DR

This paper applies a time-dependent Landauer-Büttiker formalism to study charge pumping in AC-driven graphene nanoribbons, revealing conditions for non-zero pump currents and how they can be tuned by bias parameters.

Contribution

It introduces explicit formulas for current response in GNRs under biharmonic bias and analyzes symmetry conditions affecting pump current generation.

Findings

Non-zero pump current requires broken dynamical inversion symmetry.

Pump current sign and existence can be controlled by static bias parameters.

Transient current responses exhibit harmonic selection rules based on symmetry.

Abstract

We apply the recently-developed partition-free time-dependent Landauer-B\"uttiker (TD-LB) formalism to the study of periodically-driven transport in graphene nanoribbons (GNR). When an AC driving is applied, this formalism can be used to prove generic conditions for the existence of a non-zero DC component of the net current (pump current) through the molecular device. Time-reversal symmetry breaking in the driving field is investigated and found to be insufficient for a non-zero pump current. We then derive explicit formulas for the current response to a particular biharmonic bias. We calculate the pump current through different GNR configurations and find that the sign and existence of a non-zero pump current can be tuned by simple alterations to the static parameters of the TD bias. Further, we investigate transient currents in different GNR configurations. We find a selection rule of even and odd harmonic response signal depending on a broken dynamical inversion symmetry in the bias.