Scanning Gate Microscopy of Localized States in a gate-defined Bilayer Graphene Channel

TL;DR

This study employs Scanning Gate Microscopy to identify and analyze localized states caused by potential inhomogeneities in a narrow, gate-defined bilayer graphene channel, revealing their spatial distribution and dependence on displacement fields.

Contribution

It demonstrates the use of Scanning Gate Microscopy to map localized states in bilayer graphene and explains their behavior under varying displacement fields.

Findings

Localized states are identified via conductance ellipses.

States tend to occur halfway into the channel at large displacement fields.

Observations are consistent with stochastic Coulomb blockade.

Abstract

We use Scanning Gate Microscopy to demonstrate the presence of localized states arising from potential inhomogeneities in a 50nm-wide, gate-defined conducting channel in encapsulated bilayer graphene. When imaging the channel conductance under the influence of a local tip-induced potential, we observe ellipses of enhanced conductance as a function of the tip position. These ellipses allow us to infer the location of the localized states and to study their dependence on the displacement field. For large displacement fields, we observe that localized states tend to occur halfway into the channel. All our observations can be well explained within the framework of stochastic Coulomb blockade.