Imaging ballistic carrier trajectories in graphene using scanning gate microscopy

TL;DR

This paper demonstrates how scanning gate microscopy can visualize and manipulate ballistic carrier trajectories in high-mobility graphene, revealing cyclotron motion and enabling control of carrier paths.

Contribution

It introduces a method to image and control ballistic carrier trajectories in graphene using scanning gate microscopy within a magnetic focusing setup.

Findings

Visualized cyclotron orbits in graphene

Controlled carrier redirection with the scanning tip

Mapped ballistic trajectories in high-mobility graphene

Abstract

We use scanning gate microscopy to map out the trajectories of ballistic carriers in high-mobility graphene encapsulated by hexagonal boron nitride and subject to a weak magnetic field. We employ a magnetic focusing geometry to image carriers that emerge ballistically from an injector, follow a cyclotron path due to the Lorentz force from an applied magnetic field, and land on an adjacent collector probe. The local electric field generated by the scanning tip in the vicinity of the carriers deflects their trajectories, modifying the proportion of carriers focused into the collector. By measuring the voltage at the collector while scanning the tip, we are able to obtain images with arcs that are consistent with the expected cyclotron motion. We also demonstrate that the tip can be used to redirect misaligned carriers back to the collector.