Functionalized graphene as a model system for the two-dimensional metal-insulator transition

TL;DR

This paper investigates the metal-insulator transition in functionalized graphene, revealing that disorder-induced weak localization, rather than electron-electron interactions, drives the transition in this 2D system.

Contribution

It provides the first detailed experimental evidence that disorder-induced weak localization causes the 2D metal-insulator transition in functionalized graphene.

Findings

Weak localization dominates the transition mechanism.

Disorder, not electron-electron interactions, drives the MIT.

First detailed characterization of the 2D MIT in a model system.

Abstract

Reports of metallic behavior in two-dimensional (2D) systems such as high mobility metal-oxide field effect transistors, insulating oxide interfaces, graphene, and MoS2 have challenged the well-known prediction of Abrahams, et al. that all 2D systems must be insulating. The existence of a metallic state for such a wide range of 2D systems thus reveals a wide gap in our understanding of 2D transport that has become more important as research in 2D systems expands. A key to understanding the 2D metallic state is the metal-insulator transition (MIT). In this report, we demonstrate the existence of a disorder induced MIT in functionalized graphene, a model 2D system. Magneto-transport measurements show that weak-localization overwhelmingly drives the transition, in contradiction to theoretical assumptions that enhanced electron-electron interactions dominate. These results provide the first detailed picture of the nature of the transition from the metallic to insulating states of a 2D system.