Time-resolved charge detection in graphene quantum dots

TL;DR

This paper reports real-time charge detection in graphene quantum dots, revealing detailed tunneling dynamics, the influence of localized states, and the back-action effects of charge detection on tunneling rates.

Contribution

It provides the first detailed real-time measurements of electron tunneling in graphene quantum dots, highlighting the role of localized states and detector back-action.

Findings

Single electron charging events can be detected in real-time.

Localized states influence tunneling coupling non-monotonically.

Detector bias affects the tunneling rate through back-action.

Abstract

We present real-time detection measurements of electron tunneling in a graphene quantum dot. By counting single electron charging events on the dot, the tunneling process in a graphene constriction and the role of localized states are studied in detail. In the regime of low charge detector bias we see only a single time-dependent process in the tunneling rate which can be modeled using a Fermi-broadened energy distribution of the carriers in the lead. We find a non-monotonic gate dependence of the tunneling coupling attributed to the formation of localized states in the constriction. Increasing the detector bias above 2 mV results in an increase of the dot-lead transition rate related to back-action of the charge detector current on the dot.