Direct Imaging of Coherent Quantum Transport in Graphene Heterojunctions

TL;DR

This study uses low temperature scanning gate microscopy to directly visualize quantum transport phenomena in graphene heterojunctions, revealing localized resonant cavities and edge effects in the scattering potential.

Contribution

It demonstrates a novel approach to imaging quantum transport in graphene, highlighting the role of edge and bulk resonant cavities through experimental and simulation methods.

Findings

Detection of localized Fabry-Perot cavities in graphene

Observation of halos associated with edge and bulk scattering

Correlation of experimental results with quantum transport simulations

Abstract

We fabricate a graphene p-n-p heterojunction and exploit the coherence of weakly-confined Dirac quasiparticles to resolve the underlying scattering potential using low temperature scanning gate microscopy. The tip-induced perturbation to the heterojunction modifies the condition for resonant scattering, enabling us to detect localized Fabry-Perot cavities from the focal point of halos in scanning gate images. In addition to halos over the bulk we also observe ones spatially registered to the physical edge of the graphene. Guided by quantum transport simulations we attribute these to modified resonant scattering at the edges within elongated cavities that form due to focusing of the electrostatic field.