Graphene-based charge sensors

TL;DR

This paper demonstrates graphene nanoribbon-based charge sensors capable of high sensitivity and operation under strong magnetic fields and high-frequency pulses, with significant impact on quantum dot transport.

Contribution

It introduces the use of graphene nanoribbon charge sensors for quantum dot detection, analyzing their performance and back action under various external conditions.

Findings

Charge sensitivities of 1.3×10^-3 e/√Hz achieved

Charge detector bias increases quantum dot Coulomb peak currents by 400 times

Coulomb blockade can be fully lifted using the charge detector bias

Abstract

We discuss graphene nanoribbon-based charge sensors and focus on their functionality in the presence of external magnetic fields and high frequency pulses applied to a nearby gate electrode. The charge detectors work well with in-plane magnetic fields of up to 7 T and pulse frequencies of up to 20 MHz. By analyzing the step height in the charge detector's current at individual charging events in a nearby quantum dot, we determine the ideal operation conditions with respect to the applied charge detector bias. Average charge sensitivities of 1.3*10^-3 e/sqrt{Hz} can be achieved. Additionally, we investigate the back action of the charge detector current on the quantum transport through a nearby quantum dot. By setting the charge detector bias from 0 to 4.5 mV, we can increase the Coulomb peak currents measured at the quantum dot by a factor of around 400. Furthermore, we can completely lift the Coulomb blockade in the quantum dot.