Mixing of Edge States at a Bipolar Graphene Junction

TL;DR

This study uses an atomic force microscope to create and analyze a bipolar graphene junction, revealing how edge states mix and how magnetic fields influence transport properties, with implications for quantum electronic devices.

Contribution

It demonstrates local manipulation of graphene to form p-n junctions and investigates edge state mixing and magnetic field effects on transport properties.

Findings

Quantized resistance values observed across the junction

Edge state mixing is suppressed at high magnetic fields

Transport properties vary with charge carrier density and magnetic field polarity

Abstract

An Atomic Force Microscope is used to locally manipulate a single layer graphene sheet. Transport measurements in this region as well as in the unmanipulated part reveal different charge carrier densities while mobilities stay in the order of 10000 cm^2/(Vs). With a global backgate, the system is tuned from a unipolar n-n' or p-p' junction with different densities to a bipolar p-n junction. Magnetotransport across this junction verifies its nature, showing the expected quantized resistance values as well as the switching with the polarity of the magnetic field. The mixing of edge states at the p-n junction is shown to be supressed at high magnetic fields.