Evidence for incompressible states in a metal graphene tunnel junction in high magnetic field

TL;DR

This paper reports on transport measurements of Cu-graphene tunnel junctions in high magnetic fields, revealing Landau level formation and localized states with degeneracy splitting, advancing understanding of quantum Hall effects in graphene.

Contribution

It provides experimental evidence for incompressible states and localized Landau levels in graphene tunnel junctions under high magnetic fields, highlighting the role of capacitive coupling.

Findings

Observation of Landau level-like structures at high magnetic fields

Detection of sharp features indicating localized Landau levels

Capacitive coupling affects Landau level spacing

Abstract

We present transport measurements of tunnel junctions made between Cu and graphene in a magnetic field. We observe a transition to a Landau level like structure at high fields, as well as a set of sharp features in the tunneling spectra that shift with gate and tunnel probe voltage along the lines of constant charge density. We explain the sharp features with the formation of degeneracy split localized Landau levels, and addition of electrons to those levels one by one. A large capacitive coupling to the tunnel probe also increases the gate voltage spacing between the Landau levels.