Dual top gated graphene transistor in the quantum Hall regime

TL;DR

This paper investigates how dual top gating in graphene transistors influences quantum Hall conductance, revealing complex edge channel interactions and the importance of inhomogeneity for precise quantization, relevant for metrology.

Contribution

It introduces a double top gate design in graphene transistors and analyzes its impact on quantum Hall conductance and edge channel mixing.

Findings

Multiple quantized conductance plateaus observed.

Inhomogeneity affects the exact quantization of plateaus.

Edge channel mixing explains the conductance behavior.

Abstract

We study the effect of local modulation of charge density and carrier type in graphene field effect transistors using a double top gate geometry. The two top gates lead to the formation of multiple \emph{p-n} junctions. Electron transport measurements at low temperature and in the presence of magnetic field show various integer and fractionally quantized conductance plateaus. We explain these results based on the mixing of the edge channels and find that inhomogeneity plays an important role in defining the exact quantization of these plateaus, an issue critical for the metrology applications of \emph{p-n} junctions.