Charge pumping in strongly-coupled molecular quantum dots

TL;DR

This paper explores how time-periodic driving can induce charge pumping in strongly-coupled molecular quantum dots, overcoming Franck-Condon blockade effects, with the pump current exhibiting exponential dependence on drive strength.

Contribution

It demonstrates that specific driving protocols can effectively pump charge in molecular quantum dots and reveals the exponential relationship between pump current and drive strength in strongly-coupled systems.

Findings

Driving can lift the Franck-Condon blockade.

Pump current at resonance is exponentially related to drive strength.

Charge pumping is achievable in strongly-coupled molecular quantum dots.

Abstract

The interaction between electrons and the vibrational degrees of freedom of a molecular quantum dot can lead to an exponential suppression of the conductance, an effect which is commonly termed Franck-Condon blockade. Here, we investigate this effect in a quantum dot driven by time-periodic gate voltages and tunneling amplitudes using nonequilibrium Green's functions and a Floquet expansion. Building on previous results showing that driving can lift the Franck-Condon blockade, we investigate driving protocols which can be used to pump charge across the quantum dot. In particular, we show that due to the strongly coupled nature of the system, the pump current at resonance is an exponential function of the drive strength.