Evolution of Microscopic Localization in Graphene in a Magnetic Field from Scattering Resonances to Quantum Dots

TL;DR

This study uses scanning tunneling spectroscopy to explore how magnetic fields influence electron localization in graphene, revealing a transition from weak localization to quantum dot formation due to disorder potential.

Contribution

It provides a microscopic understanding of how magnetic fields alter localization and quantum dot formation in graphene, advancing knowledge of disorder effects.

Findings

Landau levels form under magnetic field

Transition from weak localization to quantum dots

Disorder potential impacts graphene properties

Abstract

Graphene is a unique two-dimensional material with rich new physics and great promise for applications in electronic devices. Physical phenomena such as the half-integer quantum Hall effect and high carrier mobility are critically dependent on interactions with impurities/substrates and localization of Dirac fermions in realistic devices. We microscopically study these interactions using scanning tunneling spectroscopy (STS) of exfoliated graphene on a SiO2 substrate in an applied magnetic field. The magnetic field strongly affects the electronic behavior of the graphene; the states condense into welldefined Landau levels with a dramatic change in the character of localization. In zero magnetic field, we detect weakly localized states created by the substrate induced disorder potential. In strong magnetic field, the two-dimensional electron gas breaks into a network of interacting quantum dots formed at the potential hills and valleys of the disorder potential. Our results demonstrate how graphene properties are perturbed by the disorder potential; a finding that is essential for both the physics and applications of graphene.